DOE Solar Energy Technologies Program 

Welcome to the fiscal year (FY) 2007 Annual Report for the U.S. Department of Energy’s Solar 

Energy Technologies Program (Solar Program). The Solar Program is responsible for carrying 

out the federal role of researching, developing, demonstrating, and deploying solar energy 

technologies. This document presents a detailed description of the activities funded by DOE 

during FY 2007. 

FY 2007 was a year of incredible importance for the Solar Program and its partners. Announced 

during President Bush’s 2006 State of the Union address, the Advanced Energy Initiative includes 

the Solar America Initiative (SAI), a presidential initiative with the goal of achieving grid parity for 

solar electricity, produced by photovoltaic (PV) systems, across the nation by 2015. FY 2007 was 

the first official year of SAI and represented a shift in Solar Program operations, budget, activities, 

and partnerships. 

As a 9-year initiative, SAI is dependent upon wise choices made during its early years. I am 

pleased to report that FY 2007 represented a successful start to this critically important effort. A 

few of the many highlights achieved in FY 2007 and discussed in greater detail within this report 

include: 

•	 Launch of the Technology Pathway Partnerships (TPPs), public-private partnerships with 

industry designed to create fully scalable PV systems that meet the SAI cost goals. The 

TPPs are characterized by rigorous review and down-selection processes, as well as 

ambitious timetables. 

•	 Establishment of the PV Incubator activity, which funds the development of PV-system 

components to shorten their timeline to commercialization. 

•	 Initiation of a groundbreaking market transformation effort to help commercialize solar 

technologies by eliminating market barriers and promoting deployment opportunities through 

outreach activities. 

•	 Resurgence of the Solar Program’s concentrating solar power (CSP) activities, including the 

first new solicitation in several years. 

•	 Opening of the Process Design and Integration Laboratory (PDIL) at the National Renewable 

Energy Laboratory (NREL) for use by both laboratory and private industry researchers and 

designed to help standardize key aspects of PV-research processes. 

FY 2007 was truly a banner year for the Solar Program and its partners, and we are looking 

forward to even greater accomplishments in FY 2008 and beyond. We remain your publiclyfunded, federal solar program and strive to conduct the most relevant, highly-valued activities to 

our stakeholders. Your input is always welcomed. 

Thomas P. Kimbis 

Program Manager 

Solar Energy Technologies Program 

Office of Energy Efficiency and Renewable Energy 

U.S. Department of Energy 

i 
ii
 
DOE Solar Program FY 2007 Annual Report Table of Contents 

The DOE Solar Energy Technologies Program......................................................................................... i 

Photovoltaic R&D Subprogram Overview ................................................................................................ 1 

Fundamental Research.................................................................................................................. 3
 

University and Exploratory Research ........................................................................................ 4 

Electronic Materials and Devices 

Resource and Safety Research
 

Concentrator Crystalline Cells .......................................................................................... 13 

Polycrystalline Thin-Film Device Research ...................................................................... 20 

Process Technology and Advanced Materials .................................................................. 25 

Silicon Materials and Devices ........................................................................................... 30 

Cell and Module Stability & Reliability............................................................................... 34 

Measurements and Characterization ...................................................................................... 37 

Environmental Health and Safety ..................................................................................... 58 

Solar Resource Characterization ...................................................................................... 62 

Advanced Materials and Devices ............................................................................................... 67
 

Systems Development 

Solar America Initiative Photovoltaic Incubator ................................................................ 69 

Component Development
 

Systems Analysis 

Systems Testing and Evaluation
 

Component Testing and Evaluation
 

Solar America Initiative Project Monitoring ....................................................................... 71 

Technology Pathway Partnership ..................................................................................... 73 

PV Manufacturing R&D ..................................................................................................... 83 

Thin Film PV Partnership Program ................................................................................... 89 

PV Grid Integration............................................................................................................ 97 

Market, Value, and Policy Analysis ................................................................................. 100 

Modeling.......................................................................................................................... 103 

PV Inverter and Balance-of-System Testing ................................................................... 106 

PV Module and Array Testing ......................................................................................... 111 

PV Module Failure Analysis ............................................................................................ 115 

Photovoltaic System Evaluation and Optimization ......................................................... 118 

Regional Experiment Stations ......................................................................................... 121 

Solar Radiometry and Metrology .................................................................................... 125 

PDIL Infrastructure, Engineering, and Integration ................................................................. 131 

Market Transformation .............................................................................................................. 135 

Codes and Standards ............................................................................................................ 137
 

Building Integration 

Technical Partnerships 

Technical Outreach
 

Training and Certification....................................................................................................... 143 

Technology Acceptance ........................................................................................................ 149
 

Solar Decathlon............................................................................................................... 152 

Building-Integrated Photovoltaics (Solar Building Benchmarking) ................................. 157 

Finance and Insurance ................................................................................................... 160 

Government Solar Installation Program .......................................................................... 162 

Solar America Cities........................................................................................................ 165 

Solar America Showcases .............................................................................................. 171 

State and Utility Outreach ............................................................................................... 174 

iii 
Market Transformation Support Activities ....................................................................... 178 

Solar Thermal R&D Subprogram Overview.......................................................................................... 181
 

Concentrating Solar Power....................................................................................................... 183
 

CSP Applied Research .......................................................................................................... 184
 

CSP Laboratory Facilities ...................................................................................................... 190
 

CSP Technology Acceptance ................................................................................................ 191 

CSP Testing and Evaluation: Systems Analysis ................................................................... 194 

Dish Engine Research and Development ............................................................................. 197 

Parabolic Trough Research and Development ..................................................................... 201 

Solar Water Heating Systems Development ........................................................................... 209 

Solar Thermal for Zero Energy Homes ................................................................................. 210 

Hybrid Solar Lighting ............................................................................................................. 219 

Systems Integration and Coordination ................................................................................................. 225 

Communications and Outreach ................................................................................................... 227
 

International Activities .................................................................................................................. 233 

Small Business Innovation Research .......................................................................................... 237
 

Appendices 

Funding Table .............................................................................................................................. 239 

Performing Organizations by Name ............................................................................................. 241
 

Performing Organizations by State .............................................................................................. 245
 

Acronyms and Abbreviations ....................................................................................................... 249 

iv 
 

Photovoltaic R&D Subprogram Overview 

As key programs were launched under the Solar America Initiative (SAI) and other efforts were 

phased out, fiscal year (FY) 2007 was a year of transition for the Photovoltaic R&D Subprogram 

in the U.S. Department of Energy’s (DOE) Solar Energy Technologies Program (SETP). The 

largest increase in the SETP budget in decades was put to work in the SAI in a big push to bring 

the cost of solar electricity to grid parity by 2015. It is worth acknowledging that this funding 

increase was dwarfed by the amount of private capital invested in photovoltaic (PV) companies in 

2007—around $800 million in venture capital alone flowed into new U.S. PV start-ups. 

Goals and Objectives 

Within this environment, the strategy of SETP investment needed to be thoughtfully and clearly 

developed within the design of SAI. The goal of solar grid parity in the residential, commercial, 

and utility electricity markets requires system costs to be 50% to 70% lower. The wisest way to 

accomplish this goal was for SETP to build a portfolio from a technology-agnostic foundation, 

oriented to a systems-level approach. This allows companies to decide how best to trim costs in 

the primary metric for electricity relevant to PV, levelizing the cost of energy. 

Although Technology Pathway Partnerships are the main push toward grid parity, other parts of 

the SETP target opportunities to diversify the SAI portfolio. In FY 2007, the SETP initiated the PV 

Incubator program, which targets higher risk, higher payoff approaches for less mature 

companies focused on quickly ramping up innovative modules into production. More solicitations 

will be awarded in FY 2008 that will continue to add diversity, through the maturity of the 

technology (next-generation concepts), other types of components (inverters, balance of 

systems), and new partners (more university R&D support for companies). 

National laboratory participation in the SETP is undergoing a transition under the SAI, as well. 

The Thin Film Partnership program, PV Manufacturing R&D program, and the University and 

Exploratory Research program are being phased out because these needs will be supported by 

Technology Pathway Partnerships, PV Incubator, and other SAI solicitations. 

Internal research and solar community support activities, conducted by the national laboratories, 

are being refocused during the upcoming years, both to respond appropriately to a growing 

number of industry requests for collaboration and testing and to spend time developing the highrisk, high-payoff projects that are best conducted in arenas like the national labs. 

Results and Accomplishments 

These are some of the highlights of the PV Subprogram’s accomplishments in FY 2007: 

•	 Funded 11 Phase I public/private Technology Pathway Partnership awards, the flagship 

program propelling the SAI. These industry-led teams comprise more than 50 companies, 14 

universities, 3 nonprofits, and 2 national laboratories in 20 states across the United States. 

(Technology Pathway Partnerships) 

•	 Funded 10 PV Incubator companies, which will shorten the timeline for these companies to 

transition prototype and precommercial PV technologies to pilot and full-scale manufacturing. 

(PV Incubator) 

•	 Defined the scoped of a new effort in Grid Integration through 14 “Renewable Systems 

Interconnection” (RSI) reports to assess the impacts and needs related to high penetration of 

PV systems on today’s electric infrastructure. Grid Integration has the potential to become a 

large, cross-cutting initiative within the DOE Office of Energy Efficiency and Renewable 

Energy. (PV Grid Integration) 

1 Photovoltaic R&D
•	 Procured critical capital equipment to operate the National Renewable Energy Laboratory's 

(NREL’s) Process Development and Integration Laboratory (PDIL), a collaborative research 

facility In which photovoltaic companies and university partners can work with NREL 

scientists. (PDIL Infrastructure, Engineering, and Integration) 

•	 Updated the Solar Advisor Model (SAM) to make the utility financing portion more accurate 

from a project developer’s perspective, incorporated financial incentives programs into 

calculations of PV systems’ cost and performance, added an inverter model, and developed 

tools to permit the validation of performance models versus measured weather data and 

system output. (System Modeling) 

•	 Maintained prominence in cell, module, and radiometer calibration. Researchers made 5020 

cell current-voltage (I-V), quantum efficiency (QE), and linearity measurements on 1758 

samples, and made 1567 I-V measurements on 408 modules. In addition, 26 spectral and 

405 solar broadband radiometer calibrations were made within NREL and for industry and 

academic partners. (Measurements and Characterization; Solar Radiometry and Metrology) 

•	 Developed an improved technique based on “coring” followed by torque strength versus 

angle characterization to determine and measure the strength and durability of various 

interfaces within many module types. The knowledge added by this technique allows the 

characterization of the durability of the module package—and will also serve to help in 

developing accelerated aging tests for extended lifetimes. (PV Module Failure Analysis) 

•	 Provided inverter testing (performance, power quality, and utility compatibility) and 

improvement advice to manufacturers for two commercial inverters and three residential PV 

inverters, which resulted in software and hardware modifications and rectifications in beta 

units. (PV Inverter and Balance-of-System Testing) 

•	 Implemented and refined an in situ technique to determine III-V concentrator film stress 

during growth. A multibeam optical stress sensor is used in place of time-consuming x-ray 

diffraction measurements, and it may be useful in the industrial production of latticemismatched junctions in inverted devices. (Concentrator Crystalline Cells and Measurements 

and Characterization) 

•	 Developed a relatively easy way to detect “spectral skewing” changes in the solar spectrum 

produced by concentrator optics. By studying the variation of a multijunction cell’s fill factor as 

the solar spectrum changes from the light of midday to the light of sunrise or sunset, 

researchers can characterize the degree of spectrum change by the concentrator’s optics. 

(Concentrator Crystalline Cells) 

•	 Developed a transparent conducting oxide (ZnMgO) for copper indium gallium selenide 

photovoltaics that could have both greater resistance to environmental corrosion and higher 

open-circuit voltage at high gallium concentrations. (Polycrystalline Thin-Film Device 

Research) 

•	 Established a model for the formation of crystallites in thin-film crystalline silicon, a technique 

designed to produce low-cost, high-performing PV using less silicon on low-cost substrates. 

Experimental success was also attained by growing 10 microns of film silicon by a scalable 

manufacturing technique at about 620°C; this is a tenfold increase in epitaxial thickness from 

previous best results. (Silicon Materials and Devices) 

•	 Produced a nanocrystal quantum dot solar cell with 2.4% conversion efficiency and larger 

short-circuit currents than any existing nanostructured solar cell. This cell’s deposition was 

accomplished with simple layer-by-layer dip coating, without the need for sintering, 

superlattice order, or separate phases for electron and hole transport. (University and 

Exploratory Research) 

•	 Published a comparison of greenhouse gas emissions in the PV and nuclear fuel cycles. 

(V.M. Fthenakis and H.C. Kim, “Greenhouse Gas Emissions from Solar Electric and Nuclear 

Power: A Life Cycle Study,“ Energy Policy, 35, 2549-2557 2007). (Environmental Health and 

Safety) 

•	 Conducted the first study on transport and recombination dynamics in dye-sensitized solar 

cells incorporating oriented TiO2 nanotube (NT) arrays (K. Zhu, N. R. Neale, A. Miedaner, and 

A. J. Frank, Nano. Lett., 7, 69, 2007). (University and Exploratory Research). 

Photovoltaic R&D 2
Fundamental Research 

Fundamental or basic research investigates the physical mechanisms of charge carrier transport, 

band structure, junction formation, impurity diffusion, defect states, and other physical properties 

of photovoltaic and photoelectrochemical materials. This area also includes solar resource 

characterization and environmental health and safety. 

Among the research topics are innovative ideas and technologies with the potential to “leapfrog” 

current approaches. This high-risk research leads to new, nonconventional concepts that could 

dramatically improve cost effectiveness in the long term. 

Fundamental research is key to the continued advancement of photovoltaic technology necessary 

to meeting the 2015 goal of achieving $0.05/kWh to $0.10/kWh battery-free, grid-tied systems. 

Industry and university researchers work in partnership with national laboratories to improve the 

efficiency of cell materials and devices by investigating their fundamental properties and 

operating mechanisms. This teamed research approach works to identify efficiency-limiting 

defects in cell materials and analyze their electrical and optical properties. 

FY 2007 marked a host of accomplishments in the Fundamental Research area, including: 

University and Exploratory Research 

•	 Achieved a record 40.7%-efficiency metamorphic 3-junction cell, the first solar cell to 

reach greater than 40% efficiency, and the highest solar conversion efficiency achieved 

to date for any type of photovoltaic device. 

Electronic Materials and Devices 

•	 Demonstrated record efficiencies of 33.8% and 30.6% under one-sun global and space 

conditions, respectively, with the inverted cell. 

•	 Completed transition to the new laboratories facilities at the National Renewable Energy 

Laboratory’s Science and Technology facilities; cell reliability, contacts, cadmium indium 

gallium selenide (CIGS), and cadmium telluride (CdTe) laboratories are fully operational. 

•	 Developed state-of-the-art infrastructure for organic-based thin-film photovoltaics (OPV). 

•	 Achieved best-to-date efficiency of 19.1% heterojunction c-Si solar cell in the wafer 

silicon field. 

•	 Developed the “cone kinetics” model to guide film-Silicon growth. 

Measurements and Characterization 

•	 Supported more than 70 PV research partners in industry, academia, and NREL with 

analytical microscopy, surface analysis, electro-optical characterization, and cell and 

module performance. 

•	 Initiated the design of an improved solar simulator that will reduce uncertainty in highefficiency concentrator measurements. 

•	 Developed a luminescence spectrum imaging system for characterizing industrial silicon 

wafers and solar cells. 

Resource and Safety Research 

•	 Conducted a life-cycle analysis of buffer options for CIGS photovoltaics. 

•	 Completed the 1991–2005 National Solar Radiation Data Base (NSRDB) update and 

documentation, including the 10-km satellite-derived data grid from the State University of 

New York (SUNY) at Albany. 

3

Photovoltaic R&D

Fundamental Research
 

 

____________________________________________________________________________________ 

University and Exploratory Research 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Fannie Posey Eddy (NREL), 303-384-6773, Fannie_Eddy@nrel.gov 

DOE HQ Technology Manager: Jeffrey Mazer, 202-586-2455, jeffrey.mazer@ee.doe.gov 

FY 2007 Budgets: $9,290K 

Objectives 

The project aims to explore the ultimate performance limits of photovoltaic (PV) technologies, approximately doubling their sunlight-to-electricity conversion efficiencies during its course. This work includes: 

•	 Perform research and development (R&D) on improved crystalline silicon cell efficiencies and 

fabrication methods to reduce manufacturing costs. This work is leveraged by the Center of 

Excellence. 

•	 Use advanced research activities to perform leading-edge research in thin-film materials and 

solar cells. The R&D activities include device fabrication, device analysis, film growth, materials 

characterizations, and modeling. 

•	 Design thin-film tandem cells and modules that have approximately 25% and 20% efficiencies. 

•	 Create multijunction pre-commercial concentrator modules that can convert more than one third 

of the sun’s energy to electricity. 

•	 Develop high-risk/high-payoff third-generation (3G) PV technologies beyond 2015, including 

high-efficiency and exciton-based solar cells. 

•	 Target emerging state of the art, high-efficiency concepts relative to advanced super-highefficiency cells to allow cost-effective generation of electricity and hydrogen. 

•	 Provide scientific and technical research opportunities for minority undergraduate and graduate 

students in solar-energy technologies via the Minority University Research Associates (MURA) 

project. 

Accomplishments 

•	 Completed subcontract modification to maintain continuity of research activities and scientific staff 

for an additional year (University Center of Excellence). 

•	 Received IR 100 award for NREL and Spectrolab’s achievement of a record 40.7%-efficiency 

metamorphic 3-junction cell, the first solar cell to reach greater than 40% efficiency, and the 

highest solar conversion efficiency achieved to date for any type of photovoltaic device. 

•	 Made modifications to add tasks to the AMONIX subcontract to build enough multijunction 

receiver plates to populate an entire 5-kilowatt (kW) Mega Module at the University of Nevada– 

Las Vegas (UNLV) using higher-efficiency multijunction cells. 

•	 Reported fabrication of ITO/P3HT/In and ITO/ZnO NWs+CdTe (QDs) +P3HT/In PV cells and 

developed a scalable ZnO nanowire growth technology by Fisk University. 

•	 Enabled five undergraduate students to participate in the NREL MURA Internship Program. Three 

posters were presented by NREL-MURA interns at the 17th Workshop on Crystalline Silicon 

Solar Cells: Materials and Processes, August 5-8, 2007, Vail, Colorado. 

•	 Presented research findings by MURA PIs and students at the Renewable Academic Partnership 

(REAP)/Sustainable Energy from Solar hydrogen NSF/IGERT Workshop, University of Delaware, 

August 20–22, 2007. 

•	 Demonstrated a 3%-efficient hybrid inorganic polymer OPV cell at NREL. 

•	 Assisted DOE Golden Field Office (GFO) with the Solar America Initiative (SAI) university and 

industry partnership solicitation and award process. 

Future Directions 

The project will continue to address key R&D issues in support of the SAI including: 

Photovoltaic R&D

Fundamental Research

University and Exploratory Research

4
___________________________________________________________________________________ 

•	 Demonstrate a 41% III-V multijunction solar cell incorporated into a high-concentration module. 

•	 Design approaches for fabricating solar cells with greater than 50% efficiency, in quantity, in 

5 years. 

•	 Continue to assist GFO with the technical monitoring projects with the MURA program. 

•	 Phase out projects and complete subcontracts during the fiscal year. 

1. Introduction 

The University and Exploratory Research Project 

aims to explore the ultimate performance limits of 

PV technologies, approximately doubling their 

sunlight-to-electricity conversion efficiencies during its course. Research and development is 

directed toward advancing the progress of highefficiency technologies and their demonstration in 

commercial prototype products. To accomplish 

this, a wide range of complex issues are investigated to provide initial modeling and baseline 

experiments involving several advanced concepts. 

The project includes both subcontract and NREL 

in-house activities executed in parallel to reach 

long-term goals (beyond 2015). A work plan is 

being pursued between EERE and the Office of 

Science to further the R&D efforts. To ensure the 

success of the Solar America Initiative (SAI), 

NREL currently is assisting in this effort as well as 

with the SAI university and industry activities. 

Subcontracted research categories within the 

University and Exploratory Research Project 

include the following areas: (1) polycrystalline thinfilm tandems; (2) research in III-V multijunction 

concentrators; (3) future generation research; and 

(4) research collaboration with minority universities 

in the Minority University Research Associates 

(MURA) Program. 

The High-Efficiency Concepts group consists of inhouse NREL researchers and targets emerging 

state-of-the-art, high-efficiency concepts relative to 

advanced super-high-efficiency cells to allow costeffective generation of electricity and hydrogen. 

This group primarily is from the Basic Sciences 

Center and works directly with the NREL National 

Center for Photovoltaics (NCPV) scientists and 

Future Generation subcontractors. 

Near-term milestones for the R&D are listed in the 

CSP database and are addressed below. This 

R&D will lead to new record cell efficiencies and to 

commercial prototype products for the disruptive 

and revolutionary technologies. For CPV, gaining 

a position in the marketplace could portend the 

emergence of CPV systems in the next 2 to 5 

years at installed system costs of $3 per watt. One 

MW at one sun of multijunction solar cells can 

power 1 gigawatt (GW) at 1000 suns of systems. 

Similarly 1 GW of multijunction solar cells can 

power 1 terawatt (TW) of concentrator PV 

systems, revealing a new path to significant TWlevels of electricity production. For 3G technologies gaining market stance, 51%-efficient 

solar cells could achieve below $1 per watt. 

2. Technical Approach 

The University and Exploratory Research Project 

consist of five separate programs with research 

subcontracted through industry and university 

partners. All of the subcontracts are in the last 

phase of the agreement and end in FY 2008. 

However, the project is to be completed during the 

fiscal year. 

The MURA task provides scientific and technical 

research opportunities for minority undergraduate 

students to work on various solar-energy technology projects. 

Task Title FY 2007 

Budget ($K) 

Thin-Film Polycrystalline 

Tandems 860 

III-V Multijunction 

Concentrators 1,128 

Future Generation Project 703 

MURA 344 

Crystalline Si Universities 500 

University Center of Excellence 1,250 

High-Efficiency Concepts 2,060 

FY 2007 Agreement Title Budget ($K) 

University and Exploratory 1,000 Research 

3. Results and Accomplishments 

3.1. University Exploratory Research Project 

Management 

University Exploratory Research (UER) project 

management supports the management activities 

5

Photovoltaic R&D

Fundamental Research

University and Exploratory Research
needed for high-quality research within project 

budgets. All subcontracted researchers work in 

parallel with NREL scientists to reach long-term, 

beyond 2015, goals. 

A majority of the subcontracts under all of the UER 

agreements ended in FY 2007. The remaining 

subcontracts are slated to end in the summer of 

FY 2008. 

3.2. Thin-Film Polycrystalline Tandems 

A series of tandem devices on p-type ribbon or 

float zone (FZ) were fabricated at the Institute of 

Energy Conversion (IEC) at the University of 

Delaware and at Georgia Institute of Technology. 

The objective of this work is to develop a-Si thinfilm/crystalline-silicon wafer tandem cells using a 

very low-cost Si wafer, and to exceed the performance of low-cost c-Si solar cells, such as 

ribbon silicon cells. This device, illustrated in 

Figure 1, has unique features including: (1) a very 

low cost mc-Si material, such as ribbon Si, and/or 

low-purity wafers; (2) a wafer thickness of 100 to 

200 μm to reduce the cost of the wafer; 

(3) deposited emitter/passivation layers as an 

alternative to diffused emitters; and (4) a twoterminal design. 

TCO top contact with grid 

(textured) 

a-SiC wide gap n-layer 

a-Si i-layer 

a-Si p-layer 

Shorting junction 

n-emitter 

p-type wafer or 

ribbon 

Al back contact 

Figure 1. a-Si/c-Si tandem solar cell device 

schematic 

The approach is twofold: (1) To fabricate seriesconnected two-terminal tandem devices having an 

a-Si top cell, and (2) fabricate a low-cost multi-Si 

p-type bottom cell using low-cost device fabrication. Investigations of the effect of the shorting 

junction between the top and bottom cells found 

that the best shorting junction was a stack composed of 5 nm of p+ nc-Si and 5 nm of n+ nc-Si. 

This produced an a-Si/c-Si tandem solar cell with 

an efficiency of 11.3% on a float zone Si wafer. 

3.3. III-V Multijunction Concentrators 

•	 Modifications have been completed adding 

tasks to the Spectrolab and AMONIX subcontracts to build enough multijunction receiver 

plates to populate an entire 5 kW MegaModule 

at University of Nevada at Las Vegas (UNLV) 

using higher-efficiency multijunction cells 

(9/07). Amonix fabricated a new 21" MJ plate 

and installed it at UNLV. It tested greater than 

30% efficiency at Amonix in FY 2006 and 

29.7% at UNLV during FY 2007. 

•	 California Institute of Technology reported 

having InGaP/GaAs two-junction cells on Ge 

templates on Si with performance that is quite 

comparable to those on Ge bulk wafer 

substrates. 

•	 Over the period of performance (POP) the 

research at the University of Delaware from 

the contract “Novel High Efficiency Photovoltaic Devices Based on the III-N Material 

System” demonstrated the feasibility of the IIInitrides as a photovoltaic material, including 

demonstrating high-efficiency high-band-gap 

solar cells suitable for tandems with a large 

number of solar cells, novel device structures, 

new modeling tools, and improved understanding of the physical mechanisms controlling the device behavior. The contract ends in 

FY 2008 and the following summarizes the 

Research Highlights for the POP to date. 

o	 First demonstration of a GaN and InGaN 

solar cell, including IQE of more than 60% 

and Vocs of 2.4 eV. 

o	 First demonstration of InN growth on Ge. 

o	 Demonstration of metal epitaxial interface, 

allowing low -resistance contacts between 

InN and Ge and Si. 

o	 Development of device design rules for 

InGaN solar cells which include the effects 

of polarization. 

o	 Identification of mechanisms operating in 

InGaN solar cells include polarizationinduced band spike in low-band gap 

InGaN alloys. 

o	 Development of first modeling program for 

solar cells to include polarization effects 

by modifying PC1D. 

o	 Development of novel device structure for 

InGaN solar cells. 

3.4. Future Generation 

The remaining Future Generation Subcontracts 

end in FY 2008. 

Photovoltaic R&D

Fundamental Research

University and Exploratory Research

6
 

University of Delaware >50 % (ends 3/08) 

•	 The goal of the University of Delaware (UDEL) 

subcontract, “Approaches to >50% Solar 

Cells,” is to identify solar cell designs based 

on advanced concepts that are capable of 

reaching greater than 50% efficiency, and to 

determine structures that can experimentally 

demonstrate the feasibility of high-efficiency 

advanced-concept solar cells. This project has 

resulted in several advances, particularly for 

intermediate-band multiple quasi-Fermi level 

approaches. The major results include: (1) Analyzing the impact of fundamental nonidealities on theoretical efficiency; (2) design 

rules for achieving high efficiency and identification of material systems to implement highefficiency devices; and (3) experimental examination of physical processes and characterization of multiple quasi-Fermi levels devices. 

•	 UDEL identified an expanded design space for 

selection of materials systems to implement a 

quantum dot (QD) solar cell with η > 50%. 

This was done by the calculation of isoefficiency curves for a three-level system 

under x1000 concentration. Using these 

results and refined design rules, three III-V 

materials systems were identified. Preliminary 

experimental results from one system, 

InAs/GaAsSb were presented. Early results 

have shown the ability to tune the QD 

properties via the GaAsSb barrier thickness. 

UDEL also achieved two of the grant’s major 

milestones by demonstrating the absorption in 

a simulation program and the simulation of 

quantum effects, absorption and recombination properties of nanostructured absorbers 

with deep quantum states. 

Northwestern University (ends 6/08) 

•	 Material Development: The NU group reported 

significant progress in developing n-type 

transparent electrode materials in ZITO (zinc 

indium tin oxide) and also p-type transparent 

electrode materials development. Through this 

work, the group describes an important link 

between thin-film behavior and equilibrium 

bulk phase defect chemistry. The existence of 

“special” compositions was confirmed—its 

composition and transparent electrode behavior correlate well with the bulk-phase 

diagram and the propensity for Sn-excess 

(donor doping) in the bulk. This is an important 

step toward increased understanding and 

control of thin-film TCOs for transparent electrodes in organic photovoltaics (OPVs). 

•	 Novel Redox Probe Development: Northwestern University also developed a novel, 

self-assembling redox probe to analyze the 

surface electron transfer characteristics of 

transparent conducting oxides (TCOs) for 

OPVs. The NU group investigated the 

coverage and electron transfer of organics on 

inorganic (TCO) transparent electrode surfaces. In particular, the electronic properties of 

various TCO surfaces have been probed 

electrochemically via self-assembled monolayers (SAMs). A novel graftable probe 

molecule having a tethered trichlorosilyl group 

and a redox-active ferrocenyl functionality 

(Fc(CH2)4SiCl3) was synthesized and characterized for this purpose. This molecule can 

self-assemble via covalent bonds to form 

monolayers on various TCO surfaces, and be 

used for subsequent electrochemical testing 

(in terms of surface coverage and electrontransfer rates). This is an important step 

toward realizing high-efficiency OPVs. 

•	 Methods Development: New methods have 

been reported to better predict surface electronic structure—including predictions of work 

function, an essential property for OPV applications of TCO electrodes. One new method, 

the FLAPW (full-potential linear augmented 

plane wave) band structure method, was used 

to determine band structures and, for the first 

time, the electronic properties at oxide surfaces (e.g., ZnO, InN, NiO). 

3.5. Novel High-Efficiency Concepts 

The task for NREL’s High-Efficiency Concepts 

supports exploratory research in quantum dot 

cells, theory of III-V and thin-film solar cells, dyesensitized solar cells, and specialized characterization of III-V and thin-film solar cells. These highefficiency concepts could be leveraged into the 

marketplace to achieve costs of less than $1/W. 

•	 “Dye-sensitized solar cell project.” Researchers completed the first study on the 

transport and recombination dynamics in 

dye-sensitized solar cells (DSSC) incorporating oriented TiO2 nanotube (NT) arrays (K. 

Zhu, N. R. Neale, A. Miedaner, A. J. Frank, 

Nano Lett, 7, 69 (2007)). Transport and 

recombination play a major role in determining 

the overall solar-cell conversion efficiency, 

therefore studying such phenomena is 

important for further advances in the DSSC 

technology. From the present study it was discovered that the charge-collection efficiencies 

7

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University and Exploratory Research
 

 

 

 

were significantly greater in NT-based DSSCs 

than in their nanoparticle-based counterparts, 

due to much slower recombination in the NT 

films than in the nanoparticle films. Progress 

also was made in developing synthetic routes 

for preparing reproducible TiO2 nanocrystals 

for DSSCs using the sol-gel method. Despite 

the fact that sol-gel chemistry is the most 

common route for preparing TiO2 nanocrystalline films for DSSCs, it still is challenging to 

predict a priori the crystal size and structure 

from a particular synthetic protocol. To 

address this issue, researchers developed 

reproducible routes for controlling the growth 

of TiO2 nanocrystallites over a broad range of 

sizes and a narrow range of shapes 

(N. R. Neale, A. J. Frank & J. Mater. Chem. 

17, 3216 (2007)). 

•	 “Defect properties of CdTe and CdMTe study 

and first-principles band-structure calculations 

for TCO’s project.” Researchers are investigating doping polarity issues with wide-band-gap 

(WBG) semiconductors used in solar cells as 

transparent conductors and window layers. 

Most WBG semiconductors exhibit the doping 

polarity problem, that is, they can be doped 

either n-type or p-type, but not both. NREL 

has investigated this doping polarity issue and 

proposed a universal approach to overcome 

the doping difficulties. The approach is based 

on the reduction of the ionization energies of 

dopants through introduction and effective 

doping of mutually passivated impurity bands. 

The approach proposed can be applied, in 

principle, to any WBG semiconductor to overcome the doping asymmetry problem found in 

these materials, and therefore will open a 

broad vista for the application of WBG 

materials. 

•	 “Quantum Dot Solar Cells.” Two types of 

detailed theoretical analyses were conducted 

for quantum dot (QD) solar cells. One was an 

analysis of the maximum possible thermodynamic conversion efficiency possible in a 

two-component tandem quantum solar cell 

based on multiple exciton generation (MEG) in 

both or even just one of the quantum dot 

layers, with each QD layer having a different 

(optimum) band gap. The maximum efficiency 

increased from about 32% for a normal solar 

cell (1 electron-hole pair/photon) to about 45% 

for a QD solar cell; a tandem cell did not increase the efficiency over a single-layer cell. 

The second analysis used an experimental 

simple, all-inorganic QD solar cell developed 

through collaboration with the BES program. 

The cell produces a very large short-circuit 

photocurrent (~25 mA cm-2) via a Schottky 

junction between a quantum dot film deposited 

on a transparent conducting ITO electrode and 

a metal counter electrode. The PbSe NC film, 

deposited via layer-by-layer (LbL) dip coating, 

yields an EQE of 65% across the visible and 

up to 25% in the infrared region of the solar 

spectrum, with a power conversion efficiency 

of 2.4%. This NC solar cell produces larger 

short-circuit currents than any existing nanostructured solar cell, without the need for 

sintering, superlattice order, or separate 

phases for electron and hole transport. The 

analysis was done to model the performance 

of such a QD solar cell as a function of the cell 

parameters (carrier mobility, carrier lifetime, 

QD cross section, film thickness), and to show 

the importance of MEG effects in the cell 

performance. 

•	 Demonstration a 3%-efficient hybrid inorganic 

poylmer OPV cell. NREL has established a 

reproducible process for producing bulk heterojunction cells. This process required the development of an all atmospherically controlled 

process. This has been extended to approximately 3%-hybrid inorganic cells. 

•	 Novel Polycrystalline Tandems. NREL 

reseachers are working to produce and characterize carbon nanotube transparent electrodes. Researchers studied the effects of 

doping in the nanotube electrodes and performed extensive temperature-dependent 

electrical measurements to assess transport 

and stability. Results showed that changes in 

resistivity at high temperature are irreversible 

and that, due to doping, thionyl chloride is a 

relatively thermally stable dopant. Initial tests 

were begun to incorporate these electrodes 

into organic solar cells. 

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8
 

 

 

3.6. Thin-Film Center of Excellence 

The University Center of Excellence (UCE) continues to play an important role in supporting the 

advanced research activities in thin-film PV 

materials and devices. The Institute of Energy 

Conversion (IEC) is designated by the U.S. 

Department of Energy, and for the past several 

years it has been the UCE at the University of 

Delaware. The IEC continues to make significant 

contributions in both scientific and advanced 

research in all three areas, namely, a-Si, CIS and 

CdTe. Additionally, the IEC continues to play a 

lead role in the support of new and emerging thinfilm PV companies that have limited human and 

technical resources. Systematic processing variations were the focus of IEC's work. The IEC 

routinely fabricated CdTe cells having greater than 

13% efficiency. IEC provided NREL a Si heterojunction cell with the following characteristics: 

Efficiency = 18.84%; Voc = 0.6708 V; Jsc = 36.183 

mA/cm2; Fill Factor = 77.61%; masked area 

0.247 cm^2; cell area 0.56 cm^2. 

3.7. The MURA Program 

Subcontracts under the Minority University Research Associates (MURA) Program have been 

modified to extend through August 2008. 

•	 MURA principal investigators and students 

presented research findings at the Renewable 

Academic Partnership (REAP)/Sustainable 

Energy from Solar Hydrogen NSF/IGERT 

Workshop, University of Delaware, August 20– 

22, 2007. 

•	 Fisk University reported fabrication of 

ITO/P3HT/In and ITO/ZnO NWs+CdTe 

(QDs)+P3HT/In PV cells and is developing a 

scalable ZnO nanowire growth technology 

(8/07). 

•	 Two MURA/FISK students were awarded 2-

year graduate degrees (6/07). 

•	 Five undergraduate students participated in 

the NREL MURA Internship Program. Three 

posters were presented by NREL-MURA 

interns at the 17th Workshop on Crystalline 

Silicon Solar Cells: Materials and Processes, 

August 5-8, 2007, Vail, Colorado. 

3.8. Crystalline Silicon Universities 

The Crystalline Si Project subcontracts have 

ended or will end early in FY 2008. What remains 

to be done is to close out existing contracts and 

extend Texas Tech, NC State U., and GA Tech 

contracts through February 2008. These contracts 

will be closed out in FY 2008 due to resource 

constraints. It is anticipated that some of the Si 

activity will fit into the SAI University Partnerships 

in FY 2008. 

In its final report, the Manufacturing Research 

Center (MARC) at Georgia Tech addressed photovoltaic manufacturing under an NREL subcontract. 

The initiative led to the creation of the Photovoltaic 

Manufacturing Laboratory (PVML) to address 

fundamental and practical issues related to 

handling and fracture of thin polycrystalline silicon 

wafers used in solar cells, measurement of 

residual and applied stresses in the wafer due to 

processing and handling, and the development of 

factory information software tools for real-time 

monitoring of equipment used in solar cell manufacturing. The following results were reported. 

Residual Stress Measurement 

•	 Predominant orientations were found for cast 

wafers. 

•	 A relationship between dislocation density and 

residual stress was demonstrated. 

•	 Full stress components were obtained for 

several silicon beams. 

•	 Preliminary models were built to calculate 

thermal effect for the polariscopy system. 

Thin Wafer Handling and Breakage 

•	 Results of an experimental and modeling 

investigation of deformation and stresses produced in polycrystalline silicon wafers handled 

by a Bernoulli gripper showed that the air-flow 

rate and wafer thickness have a significant 

effect on wafer deformation. 

•	 For all wafer types, a transition in the maximum in-plane principal tensile stress location 

from the center to the edges occurred as the 

air-flow rate was increased. The relation 

between the total stress and breakage was 

analyzed by calculating the critical crack 

length. Furthermore, breakage can be predicted by using the knowledge of residual 

stresses, handling stresses (calculated from 

the FE model), and wafer strength. 

Factory Information Systems 

•	 It was demonstrated that the CAMX standards 

can be used by the photovoltaic industry to 

improve productivity and reduce cost. 

9

Photovoltaic R&D

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University and Exploratory Research
4. Planned FY 2008 Activities 

• Complete subcontracts in all programs. 

•	 Demonstrate high-efficiency cell in concentrator module, 31%-efficiency conversion. 

•	 Perform GFO-Release Solicitation, “Minority 

University Research Associates Program.” 

5. FY 2007 Special Recognitions 

Spectrolab and NREL received an R&D 100 award 

for achievement of a record 40.7%-efficiency 

metamorphic 3-junction cell. This cell is the first 

solar cell to reach efficiency greater than 40%, and 

the achieved the highest solar conversion efficiency to date for any type of photovoltaic device. 

6. Major FY 2007 Publications 

Chen, Shiyou, X. G. Gong, and S.-H. Wei, “Band 

Structure Anomaly of Chalcopyrite Semiconductors Cugax2 Versus Aggax2 (X=S and Se) and 

Their Alloys,” Phys. Rev. B., Vol. 75, 205209 

(2007). 

Da Silva, J. L. F., S.-H. Wei, J. Zhou, and X. Wu, 

“Stability and Electronic Structures of CuxTe,” 

Appl. Phys. Lett., Vol. 90, 091902 (2007). 

Hanna, M. C. and A. J. Nozik, “Solar Conversion 

Efficiency of Photovoltaic and Photoelectrolysis 

Cells with Carrier Multiplication Absorbers,” 

Journal of Applied Physics, Vol. 100, 74510 (2006) 

(published FY07). 

Jena, H., M. Faruq, Gnanasekar, and B. 

Rambabu, “Nanocrystalline Bulk and Thin Films of 

LaNi1-xFexO3±δ (x=0-0.5) (LNF) as Cathode 

Material for IT-SOFCs,” Journal of Materials 

Science (2007). 

Jena, H., India Snowden, Fannie Posey Eddy, and 

B. Rambabu, “A Study on Proton Transport in 

Nanocrystalline Calcium Hydroxy Apatite and Its 

Sr and Mg Substituted Analogues Prepared by 

Sonochemical and Hydrothermal Methods,” 

submitted to Journal of Materials Science (2008). 

Jin, S., Y. Yang, J. E. Medvedeva, L. Wang, S. Li, 

N. Cortes, A. W. Metz, J. Ni, M. C. Hersam, 

A. J. Freeman, and T. J. Marks, “Tuning the 

Properties of Transparent Oxide Conductors. 

Dopant Ion Size and Electronic Structure Effects 

on CdO-Based Transparent Conductive Oxides. 

Ga- and In- Doped CdO Thin Films Grown by 

MOCVD,” Inorg. Chem. (in press). 

Song, J.-H., T. Akiyama, A. J. Freeman, “Stabilizing Mechanism of the Dipolar Structure and its 

Effects on Formation of Carriers in Wurtzite {0001} 

Films: InN and ZnO,” Phys. Rev. B. (accepted for 

publication). 

Wu, X., J. Zhou, A. Duda, Y. Yan, G. Teeter, 

S. Asher, W. K. Metzger, S. Demtsu, S.-H. Wei, 

and R. Noufi, “Phase Control of CuxTe Film and its 

Effects on CdS/CdTe Solar Cell',” Thin Solid Films, 

Vol. 515, 5798 (2007). 

Yan, Y., C.-S. Jiang, R. Noufi, S.-H. Wei, H. R. 

Moutinho, and M. M. Al-Jassim, “Electrical Benign 

Behavior of Grain-Boundary in Polycrystalline 

CuInSe2 Films,” Phys. Rev. Lett., Vol. 99, 235504 

(2007). 

Yan, Y., J. Li, S.-H. Wei, and M. M. Al-Jassim, 

“Possible Approach to Overcome the Doping 

Polarity in Wide-Band-Gap Semiconductors,” 

Phys. Rev. Lett., Vol. 98, 135506 (2007). 

Yan, Y. and S.-H. Wei, “Doping Asymmetry in 

Wide-Band Gap Semiconductors: Origins and 

Solutions,” Phys. Stat. Sol., Vol. 245, 641 (2008). 

Zhou, J., X. Wu, Y. Yan, S. Asher, 

J. D. L. F. Da Silva, S.-H. Wei, L. Weinhardt, M. 

Bar, and C. Heske, “The Mechanism of J-V ‘rollover’ in CdS/CdTe Devices,” Mater. Res. Soc. 

Symp. Proc., Vol. 1012, Y13-03 (2007). 

Photovoltaic R&D

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10
 

7. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ Principal 

Investigator Location/e-mail 

Description/ 

Title of Research Activity 

FY 2007 

($K) 

Amonix, Inc. 

Vahan Garbushian 

Torrence, CA 

drvahan@earthlink.net 

Design and Demonstration of a 

Greater than 33% Efficiency HighConcentration Module Using 40% 

III-V Multijunction Devices 

234* 

California Institute of 

Technology 

Harry Atwater 

Pasadena, CA 

haa@daedalus.caltech.edu 

Four-Junction Solar Cell with 40% 

Target Efficiency Fabricated by 

Wafer Bonding and Layer 

Transfer 

184* 

Central State University 

Clark Fuller Wilberforce, OH cfuller@prodigy.net 

Renewable energy technology 

and technology transfer in 

developing countries 

34 

Duke University 

Teh Tan 

Durham, NC 

ttan@duke.edu 

Modeling Metallic Precipitate 

Dissolution in Silicon Under Point 

Defect injection 

51 

Fisk University 

Richard Mu 

Nashville, TN 

rmu@fisk.edu 

Development of Si quantum dots 

for advanced solar cells with 

maximum efficiency 

41 

Georgia Institute of 

Technology 

Steven Danyluk 

Ostapenko 

Atlanta, GA 

steven.danyluk@me.gatech.edu Stress Evaluation 50 

Georgia Institute of 

Technology 

Steven Danyluk 

Atlanta, GA 

steven.danyluk@me.gatech.edu 

Stress Evaluation and 

Manufacturing of Wafers 200 

Georgia Institute of 

Technology 

Ajeet Rohatgi 

Atlanta, GA 

Ajeet.Rohatgi@ece.gatec.edu 

Thin-Film Si Bottom Cells for 

Tandem Device Structures 200 

Howard University 

J. M. Momoh 

Washington, DC 

jmomoh@msn.com 

Developing automation/strategies 

to improve power management 

and distribution of renewable 

energy resources 

50 

North Carolina A&T State 

University 

G. Shahbazzi 

Greensville, NC 

ash@ncat.edu 

Modeling performance of a gridconnected PV system in a 

residential area 

41 

North Carolina Central 

University 

Joe Dutta 

Durham, NC 

jmd@nccu.edu 

Fabricating and characterizing 

bulk and non-phase PV materials 

for student research 

41 

North Carolina State 

George A. Rozgonyi 

Raleigh, NC 

rozgonyi@ncsu.edu Defect Engineering 65 

Northwestern University 

Tom Mason 

Evanston, IL 

tmason@northwestern.edu 

Interface and Electrodes for NextGeneration Organic Solar Cells 250 

Oregon State University 

Douglas Keszler 

Corvallis, OR 

Douglas.keszler@orst.edu 

Novel Materials Development for 

Polycrystalline Thin-Film Solar 

Cells 

224 

Penn State 

S. Ashok 

University Park, Pennsylvania 

S.Ashok@PSU.edu 

Electron Cyclotron Resonance 

(ECR) Hydrogenation and 

Deuteration of Solar Cell Samples 

15 

Southern University and A&M 

College 

Rambabu Bobba 

Baton Rouge, LA 

Rambabu@grant.phys.subr.edu 

Student research projects related 

to energy conversion and storage 

devices 

37 

11

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Organization/ Principal 

Investigator Location/e-mail 

Description/ 

Title of Research Activity 

FY 2007 

($K) 

Spectrolab, Inc. 

Raed Sherif 

Sylmar, CA 

rsherif@spectrolab.com 

Ultra-High-Efficiency Multijunction 

Cell and Receiver Module 318* 

Texas Tech 

Stefan Estreicher 

Lubbock, TX 

Stefan.Estreicher@ttu.edu 

Theoretical Modelling, HPassivation 75 

Underwriters Lab/ Arizona 

State University 

Liang Ji 

Phoenix, AZ 

Liang.ji@us.ul.com 

Development of IEC Design 

Qualification Standard for 

Concentrator PV Modules 

40 

University of ColoradoBoulder 

Josef Michl 

Boulder, CO 

michlj@colorado.edu 

Ultra-High Efficiency Excitonic 

Solar Cells 278* 

University of Delaware 

Robert Birkmire 

Newark, DE 

Birkmire@ee.udel.edu 

Processing, Materials, Devices 

and Diagnostics for Thin Film 

Photovoltaics: Fundamental and 

Manufacturing Issues 

1257 

University of Delaware 

Christiana Honsberg 

Newark, DE 

honsberg@ece.gatech.edu 

Novel High Efficiency PV Devices 

Based on the III-N Material 

System 

175** 

University of Delaware 

Christiana Honsberg 

Newark, DE 

honsberg@ee.udel.edu 

Theoretical and Experimental 

Investigation of Approaches to 

>50%-Efficient Solar Cells 

190* 

University of Delaware 

Bill Shafarman 

Newark, DE 

wns@udel.edu 

High-Performance PV 

Polycrystalline Thin-Film Tandem 

Cells 

90 

University of Oregon 

David Cohen 

Eugene, OR 

dcohen@darkwing.uoregon.com 

Identifying the Electronic 

Properties Relevant to Improving 

the Performance of High BandGap Copper-Based I-III-VI2 

Chalcopyrite Thin Film PV 

Devices 

140 

University of Texas, 

Brownsville 

M. Blanco 

Brownsville, TX 

mjblanco@utb.edu 

Student/faculty teams for 

designing and developing 

computer-simulation tools for 

design of solar concentrating 

systems. 

34 

University of Texas, El Paso 

Gregory Lush 

El Paso, TX 

glush@gerdau.com 

Investigation, fabrication, 

characterization, and modeling of 

solar cells 

45 

University of Toledo 

Alvin Compaan 

Toledo, OH 

adc@physics.utoledo.edu 

Sputtered II-VI Alloys and 

Structures for Tandem PV 113 

* Forward funded into FY 2008 

** Modification pending for FY 2008 

Photovoltaic R&D

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Electronic Materials and Devices 

Concentrator Crystalline Cells 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact:	 Daniel Friedman (NREL), 303-384-6472, daniel_friedman@nrel.gov 

DOE HQ Technology Manager:	 Marie Mapes, 202-586-3765, marie.mapes@ee.doe.gov 

FY 2007 Budgets:	 $2,369K* 

*Reference funding table in appendix 

Objectives 

•	 Demonstrate a high-efficiency inverted triple-junction concentrator solar cell at 300 suns. 

•	 Establish optical stress sensor as an in situ probe of relaxation of lattice-mismatched solar cells. 

•	 Transfer the recipe for the inverted triple-junction cell to the low-pressure reactor to identify 

differences in growth of this structure at low pressure. 

•	 Assess the potential for further efficiency improvements in inverted three-junction solar cells. 

•	 Grow ~1 eV GaInNAs with Bi surfactant toward achieving >2 μm depletion width in GaInNAs. 

Accomplishments 

•	 Identified a limiting series resistance in the contact layers of inverted, lattice-mismatched devices, 

resulting in a peak efficiency of 38.9±2.3% at 80 suns and 36% at approximately 300 suns. 

•	 With the inverted cell, demonstrated record efficiencies of 33.8% and 30.6% under one-sun 

global and space conditions, respectively. 

•	 Assessed the potential for further efficiency improvements in an inverted cell, with greater than 

42% efficiency projected. 

•	 Implemented and refined an in situ technique to determine the film stress during growth. 

•	 Transferred cell recipes to a low-pressure metal-organic vapor phase epitaxy (MOVPE) reactor 

and demonstrated inverted top cells, tunnel junctions, GaInP/GaAs tandems, and GaInP grades 

to GaInAs. 

•	 Grew GaInNAs solar cells with a Bi surfactant and demonstrated depletion widths in excess of 

2 μm. 

•	 Measured and modeled the outdoor performance of GaInP2/GaAs tandem cells under direct 

illumination, lending support for the use of the American Society of Testing and Materials (ASTM) 

G-173 direct spectrum to design concentrator cells for maximum daily energy and midday power. 

Future Directions 

•	 Demonstrate inverted, lattice-mismatched multijunction (iLMM) devices with a concentrator 

performance peak above 100 suns. 

•	 Demonstrate iLMM cells with optimized second- and third-junction band gaps. 

•	 Study the effects of growth temperature, surfactants, and impurities on lattice-mismatched 

epitaxy. 

• Perform a comparative evaluation of degradation mechanisms in multijunction cells and plan for 

work to mitigate identified problems. 

1. Introduction concentrators is that all sections of the supply 

chain are well developed to support a 

A large portion of the U.S. market for photovoltaics multigigawatt capacity, because most PV 

(PV) may best be served by utility-scale PV components share production technology with 

systems. Such systems can minimize electricity other commercially available products. The U.S. 

costs through the use of tracking PV concentrator Department of Energy’s PV research and 

systems. The exciting business prospect for PV development (R&D) has recognized this 

13

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opportunity and maintained a research program 

for the development of high-performance 

concentrator cells. Thus, research in the 

Concentrator Crystalline Cells Group at NREL 

focuses its resources on development of ultrahigh-efficiency solar cells that form the heart of the 

concentrator system. Moving the next generation 

of devices into manufacturing requires that we 

understand and control the growth of latticemismatched structures in order to reliably produce 

high-efficiency devices. Mismatched layers with 

high quality can be grown if the strain and 

relaxation properties are controlled in order to limit 

the dislocation density. This is demonstrated by 

the record results from NREL and Spectrolab for 

two different types of lattice-mismatched cell 

designs, both with an efficiency approaching 40%. 

In this area, our primary activity is to expand the 

understanding and control of the epitaxial 

processes that influence strain and relaxation. 

For lattice-matched devices, a higher efficiency 

could theoretically be achieved if the photocurrent 

generated in the Ge junction could be divided 

between a 1-eV material and the bottommost Ge 

junction. The dilute nitride material GaInNAs 

continues to be the most promising candidate for a 

1-eV junction. Growth of GaInNAs by molecular 

beam epitaxy (MBE) has achieved remarkably 

improved photocurrents, but open-circuit voltages 

remain a challenge. In FY 2007, we aimed to 

bring this work to closure; however, this now 

appears to have been premature. Therefore, we 

are maintaining our capabilities with this materials 

system, because we have received very favorable 

estimates of the potential of this work from a 

potential industry partner. 

As industry chooses to embrace the highefficiency concentrator approach, many questions 

arise, including one about the sensitivity of power 

generation to changing spectral conditions. The 

Concentrator Crystalline Cells Group continues to 

support the growth of industry by providing on-sun 

measurement and modeling of concentrator cells 

in real-world operation. 

2. Technical Approach 

This project is composed of three primary 

research tasks. These research tasks and areas 

of investigation are as follows: 

2.1 Inverted Lattice-Mismatched Approach 

•	 Decrease deleterious series resistance in 

inverted, metamorphic devices to improve 

operation at high concentration 

•	 Assess the usefulness of in situ stress 

measurements for lattice-mismatched epitaxy. 

2.2 Dilute Nitrides 

•	 Study the effects of Bi as a surfactant for dilute 

nitride materials 

•	 Use a Bi surfactant to grow ~1 eV GaInNAs 

with a depletion width >2 μm. 

2.3 Concentrator System Device Issues 

•	 Address outdoor measurements of tandem 

cells designed for different spectral conditions 

•	 Address modeling of on-sun data to determine 

the effects of spectral skewing. 

3. Results and Accomplishments 

3.1 Inverted Lattice-Mismatched Approach 

Milestones for this activity were as follows: 

•	 Achieve a 300 suns inverted triple-junction cell 

(Level 3, June 2007) 

•	 Establish optical stress sensor as an in situ 

probe of relaxation of lattice-mismatched solar 

cells (Level 4, March 2007) 

•	 Transfer the recipe for the inverted triplejunction cell to the low-pressure reactor to 

identify differences in the growth of this 

structure at low pressure (Level 4, June 2007) 

•	 Assess the potential for further efficiency 

improvements in an inverted three-junction 

solar cell (Level 4, June 2007). 

We have been working on a new approach for 

ultra-high-efficiency concentrator tandem solar 

cells based on inverted III-V heteroepitaxial 

structures that combines both lattice-matched and 

lattice-mismatched component subcells in a 

monolithic structure, as shown in Figure 1. In this 

approach, high-quality GaInP top junctions and 

GaAs middle junctions are grown inverted and 

lattice-matched on a GaAs substrate. A latticemismatched 1.0-eV GaInAs bottom junction is 

grown last on a transparent GaInP compositionally 

step-graded layer. After growth, the sample is 

attached to a convenient handle, the original 

substrate is removed, and the grids are applied. 

Quantum efficiency data for an inverted device is 

shown in Figure 2. An early device achieved 

37.9% efficiency at about 10 suns, but it was 

limited from further improvement in efficiency by a 

series resistance. 

Photovoltaic R&D

Fundamental Research

Electronic Materials and Devices

14
In FY 2007, we identified a limiting series 

resistance in the contact layers, thus completing 

an important milestone. A dedicated flash 

simulator donated from the measurements group 

was very important for quickly identifying this 

resistance. Optimization of semiconductor contact 

layers and metal grid design increased the peak 

higher efficiencies under AM0 spectral conditions 

(31.9% reported in Milan) while using industrial 

capacity processing equipment. 

100 

80 GaInP 

junction 

GaAs 

junction InGaAs 

junction 

Reflectance 

400 600 800 1000 1200nm 

Wavelength (nm) 

QE or Reflectance (%)

efficiency to 38.9±2.3% at 80 suns. This device 

also operated at concentrations greater than 300 

suns, completing a Level 3 milestone. Opencircuit voltage, fill factor, and efficiency data for 

this device are shown in Figure 3. One Se-doped 

GaInNAs contact layer was used to achieve high 

carrier concentration and reduce dopant diffusion 

60 

40 

20 

from the contact interface during subsequent 0

growth. A further reduction in series resistance is 

required for optimal performance at 500X to 

1000X concentration. The resulting potential Fig. 2. External quantum efficiency and specular 

efficiencies were assessed at greater than 42%. reflectance of the AM1.5G inverted triple-junction 

device. 

Si or Glass Handle 

Gold Grid 

Back Gold 

Al0.3Ga0.7As : C

 GaAs : Se 

Tunnel

 Junctions 

Se-doped contact 

GaInP stop etch 

GaAs substrate 

GaInP : Se emitter 

2.5 μm GaAs : Zn base 

2.9 μm In0.3Ga0.7As : Zn base 

Removed 

GaAs : Se emitter 

InGaAs : Se emitter 

Gax In1-x P : Si 

Step Grade 

0.9 μm Ga0.5In0.5P : Zn base 

Ga0.3In0.7P 

Passivation 

Al0.5In0.5P 

Window 

Al0.25Ga0.25In0.5P 

BSF 

3.6 

3.4 

3.2 

1 10 100 

Concentration (Suns) 

Solar Simulator

 continuous

 flash 

V oc = 3.28 kT/q ln( J sc / 6.5x10-18 mA/cm2 ) 

1.8 eV 

Top 

Junction 

1.4 eV 

Middle 

Junction 

Transparent 

Graded 

V (V) oc

3.0 

2.8 

90 

Fill Factor (%)

88 

86 

84 

82 

80 

42 Layer Efficiency (%)

40 

38 

36 

34 

32 

1.0 eV 

Bottom 

Junction 

30 

Fig. 3. Open-circuit voltage, fill factor, and 

efficiency of the AM1.5D (low-AOD) inverted tripleFig. 1. Schematic of inverted triple-junction junction device as a function of irradiance (1000 

structure. The band gap of the semiconductor W/m2

 = 1 sun). The Voc is fit with a simple diode 

layers are indicated by a rainbow color scale equation (dashed line). 

(violet = high, red = low). 

Engineering the strain in lattice-mismatched solar 

cell junctions is an important factor in optimizing 

their performance. Graded structures that result in 

While optimizing this structure for operation under 

high concentration, we fabricated several devices 

for operation under one-sun global and space near-zero strain within lattice-mismatched devices 

conditions. These devices demonstrated record was pioneered during thermophotovoltaic studies 

efficiencies of 33.8% and 30.6% under these by Mark Wanlass of NREL. Time-consuming x-ray 

conditions, respectively. This technology (referred diffraction measurements have been used in the 

to as IMM devices) has been transferred to past to characterize and improve the strain. In FY 

Emcore, and the organization has achieved even 2007, we implemented and refined an in situ 

15

Photovoltaic R&D

Fundamental Research

Electronic Materials and Devices
 

technique to determine the film stress during ���

growth. In situ stress data from a multibeam ���

optical stress sensor (MOSS) were compared and ���

correlated with ex situ strain measurements from ���

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x-ray diffraction and the performance of latticemismatched 1.0-eV GaInAs solar cells, as shown 

in Figure 4. The efficiency of these 1.0-eV devices 

was found to quickly degrade under tensile stress 

and strain, but excellent performance was 

demonstrated for near-zero or slightly 

compressive stress and strain (see Figures 5 and 

6). Transmission electron microscopy (TEM) and 

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cathodoluminescence demonstrated relatively low 

defect densities (~2x106 -2 cm ) in these optimized 

structures. The MOSS proved to be an essential 

time-saving tool for optimization of stress for highperformance, lattice-mismatched junctions in 

inverted devices and will likely be useful for 

industrial production of such devices. 

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Fig. 5. Solar cell data are shown as a function of 

junction stress during growth. Eg was derived from 

quantum efficiency data. The actual InxGa1-xAs 

composition was derived from x-ray ����

Fig. 4. Shown are growth temperature stress 

calculated from in situ MOSS measurements and 

room temperature strain calculated from ex situ xray diffraction measurements for both the 

In.27Ga.73As active junction and the thick GaxIn1-xP 

layer at the top of the graded buffer as a function 

of the composition of this layer. 

measurements. 

Photovoltaic R&D

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16
 

 

3.2 Dilute Nitrides 

GaInNAs solar cells could be useful in nextgeneration multijunction solar cells if issues 

surrounding low photocurrents and photovoltages 

are surmounted. Wide-depletion-width devices 

generate significant photocurrent using a p-i-n 

structure grown by MBE, but these depletion 

widths are realized only in a region of parameter 

space that leads to rough surface morphologies. 

Thus, bismuth was explored as a surfactant for the 

growth of GaInNAs solar cells. Very low fluxes of 

Bi proved effective at maintaining smooth 

surfaces, even at high growth temperatures and In 

contents. However, Bi also increased the net 

donor concentration in these materials, manifested 

in our n-on-p device structures as a pn-junction 

that moves deeper into the base layer with 

increasing Bi fluxes. This effect is shown in Figure 

7. Quantum efficiency modelling and scanning 

Kelvin probe microscopy measurements confirm 

the type conversion of the 

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Fig. 6. Shown are 220 dark field TEM images of 

two inverted InGaAs solar cells grown with 

different film stress in the active layer: (a) 0.12 

GPa compressive, (b) 0.17 GPa tensile. 

Threading dislocations (TD) and the ends of misfit 

dislocations (MD) are observed in the thick 

InGaAs layer of sample b. 

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We have begun growing inverted cells on the lowpressure (cluster-tool) metal-organic chemical 

vapor deposition, or MOCVD, growth chamber, 

completing a Level 4 milestone. The goal of this 

work is a recipe for an inverted 

GaInP/GaAs/GaInAs three-junction device that 

can then be optimized and studied. Work so far 

has produced functional (but not optimal) inverted 

top cells, tunnel junctions, GaInP/GaAs tandems, 

and GaInP grades to GaInAs. This work will 

continue in FY 2008. 

In addition to these activities, we have evaluated 

possible improvements to the lattice-mismatched 

device; many of these will be explored 

experimentally in FY 2008. These include the use 

of different band-gap combinations for optimum 

conversion efficiency, new grid designs for higher 

concentration, transparent back contacts for use in 

a mechanically stacked device, and improved 

antireflection coatings. 

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Fig. 7. Measured and calculated IQE data for a 

set of GaInNAs(Bi) solar cells with different 

impinging fluxes of Bi (the Bi flux is labelled for 

each curve). With Bi present, the base layer 

converts to n-type, creating a thick emitter. 

base layer from p-type to n-type. Bismuth 

incorporation in GaAsBi samples shows signs of 

surface segregation, leading to a finite build-up 

time, and this effect may lead to slow changes in 

the electrical properties of GaInNAs(Bi) devices. 

Bismuth also appears to create a defect level, as 

measured by deep-level transient spectroscopy 

measurements, although this defect level is not 

deleterious enough to increase the dark current in 

the devices. This painstaking work has recently (in 

FY 2008) attracted a potential industry partner. 

17

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90 

89 

Fill Factor (%) 91 

90 

CDE 

Day 2 

6:00 AM 12:00 PM 6:00 PM 

Time of Day 

Fig. 8. Fill factor is plotted versus time for a set of 

tandem cells (A–E) during a test day. Cell A has 

the thinnest top cell and is well suited for a “bluerich” AM0 space spectrum. Cell E has the thickest 

top cell and is best suited for “red-rich” morning 

and evening spectra. Measured (top) and 

modeled (bottom) results are shown. Both plots 

are for cells at one-sun (collimated/direct), and the 

cells are cooled to 25°–30°C. Current-matched 

times for cells C, D, and E are indicated along the 

bottom axis with dashed lines. 

3.3 Concentrator System Device Issues 

We have measured and modeled the outdoor 

performance of GaInP2/GaAs tandem cells under 

direct illumination for concentrator applications. 

Pressure-Corrected Air Mass 

88 

87 B 

D 

C2 C

86 Day 2 E 

6:00 AM 12:00 PM 6:00 PM 

Time of Day
 

Pressure-Corrected Air Mass
 

Model Results spectrum is required for current-matching, shifting 

Day 1 the fill factor minima toward midday. If “red” 93 A bottom cell light is preferentially removed, then a 

more red-rich incident spectrum is required for 

92 

during continuous operation with no modification B to the concentrator systems. 

Measured Results 

Day 1 

toward sunrise and sunset (away from midday). 

Such shifts can be used to detect and diagnose 

spectral skewing by concentrator optics, outdoors 

current matching, so the fill factor minima will shift 

Here, "spectral skewing" refers to any change in 

the incident spectrum, which affects the current 

matching of a tandem cell. This method requires 

no modification of the concentrator system and is 

therefore suitable for long-term monitoring of 

systems in continuous use. 

Our method is based upon the variation of the fill 

factor as the incident direct spectrum changes 

over the course of a clear, sunny day (see Figure 

8). Sharp minima occur when cells C, D, and E 

are current-matched. (Cells A and B are never 

current-matched, so only a single broad minimum 

is seen.) If the optics of a concentrator system 

preferentially remove “blue” top cell light from the 

incident spectrum, then a more blue-rich incident 

A We also proposed an outdoor testing method for 

characterizing spectral skewing of the incident 

spectrum by the optics of a concentrator system. 

"AM1.5D" spectrum is a poor choice, unless 

maximizing morning and/or evening power 

production is a priority. 

Fill Factor (%) 

10 10 5 5

3 32 21.5 1.51.2 1.21.1 1.11.06 1.061.1 1.1

1.2 1.2 

1.5 1.5 

2 2

3510 

3510 

4. Planned FY 2008 Activities 

During FY 2008, this project will complete several 

milestones, including these: 

•	 Demonstrate an iLMM device with 

concentrator performance peak above 100 

suns (September 2008). 

•	 Demonstrate an iLMM cell with optimized 

second- and third-junction band gaps 

(September 2008). 

•	 Study the effects of growth temperature, 

surfactants, and impurities on latticemismatched epitaxy (September 2008). 

•	 Perform a comparative evaluation of 

degradation mechanisms in multijunction cells, 

and plan for work to mitigate identified 

problems (September 2008). 

This study lends support to the use of the ASTM 

G-173 direct spectrum to design cells for 

maximum daily energy and midday power. A 

similar "low AOD" spectrum, and even the AM1.5G 

spectrum, will also work quite well. The old G159 
 

 

 

 

5. FY 2007 Special Recognitions, Awards, and 

Patents 

Dan David Prize: Quest for Energy 

Dr. James Hansen, Dr. Sarah Kurtz, and Dr. Jerry 

Olson 

United States Patent 7,229,498 

Andrew Norman and Jerry Olson, “Nanostructures 

produced by phase-separation during growth of 

(III-V)1-x(IV2)x alloys; issued June 12, 2007. 

Dr. Bill McMahon chaired the Solar Energy and 

Applications session of SPIE’s Optics and 

Photonics conference, held 28-30 August 2007 in 

San Diego, California. 

6. Major FY 2007 Publications 

J.F. Geisz, S. Kurtz, M.W. Wanlass, J.S. Ward, A. 

Duda, D.J. Friedman, J.M. Olson, W.E. McMahon, 

T.E. Moriarty, and J.T. Kiehl, "High-efficiency 

GaInP/GaAs/InGaAs triple-junction solar cells 

grown inverted with a metamorphic bottom 

junction," Appl. Phys. Lett. 91, 023502 (2007). 

J.F. Geisz, A.X. Levander, A.G. Norman, K.M 

Jones, M.J. Romero, "In situ stress measurement 

for MOVPE growth of high efficiency latticemismatched solar cells," J. Crys. Growth, in press. 

A.J. Ptak, R. France, C.-S. Jiang, and R.C. Reedy, 

“The Effects of Bismuth on Wide-Depletion-Width 

GaInNAs Solar Cells,” J. Vac. Sci. Technol. B, in 

press. 

B. Fluegel, A. Mascarenhas, A. J. Ptak, S. Tixier, 

E. C. Young, and T. Tiedje, “Common origin of E+ 

in GaAs1-xNx and GaAs1-xBix: invalidity of the BAC 

model,” Phys. Rev. B, 76, 155209 (2007). 

T. Liu, D. Korakakis, S. Chandril, T.H. Myers, and 

A.J. Ptak, “Bismuth surfactant effects for GaAsN 

and beryllium doping of GaAsN and GaInAsN 

grown by molecular beam epitaxy,” J. Cryst. 

Growth 304, 402 (2007). 

W.E. McMahon, K.E. Emery, D.J. Friedman, L. 

Ottoson, M.S. Young, J.S. Ward, C.M. Kramer, A. 

Duda, and S. Kurtz, “Fill Factor as a Probe of 

Current-Matching for GaInP2/GaAs Tandem Cells 

in a Concentrator System during Outdoor 

Operation,” Prog. in Photovoltaics, in press. 

W. E. McMahon, K. E. Emery, D. J. Friedman, L. 

Ottoson, M. S. Young, J. S. Ward, C. M. Kramer, 

A. Duda, and S. Kurtz, “Daily Fill Factor Variation 

as a Diagnostic Probe of Multijunction 

Concentrator Systems during Outdoor Operation,” 

High and Low Concentration for Solar Electric 

Applications II session of SPIE’s Optics and 

Photonics conference (28-30 August 2007, San 

Diego); Proc. of SPIE, Vol. 6649, 664906 (2007). 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Electronic Materials and Devices 

Polycrystalline Thin-Film Device Research 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact:	 Timothy Gessert (NREL), 303-384-6451, tim_gessert@nrel.gov 

DOE HQ Technology Manager:	 Marie Mapes, 202-586-3765, marie.mapes@hq.doe.gov 

FY 2007 Budgets:	 $2,537K (NREL)* 

*Reference funding table in appendix 

Objectives 

•	 Finalize fit-up designs and complete the moving of equipment related to cadmium telluride 

(CdTe), cadmium indium gallium selenide (CIGS), transparent conducting oxides (TCO), 

reliability, and multi-user measurements from the NREL Solar Energy Research Facility (SERF) 

to the NREL Science and Technology Facility (S&TF). 

•	 Order initial components of the CIGS Process Development and Integration Laboratory (PDIL) 

platform in the S&TF and continue the design development of the CdTe PDIL platform. 

•	 Begin to reestablish research activities in S&TF. 

•	 Secure intellectual property (IP) related to the design of novel TCOs or for use in thin-film 

photovoltaics (PV). 

•	 Assist with development of goals and metrics associated with CdTe and CIGS Technology 

Roadmaps, including the coordination of PDIL platform designs. 

Accomplishments 

•	 Completed fit-up designs and facilities coordination to enable 100% of equipment moves to the 

S&TF: Cell Reliability laboratories were completed in October 2006, Contacts laboratories were 

completed in December 2006, CIGS laboratories were completed in February 2007, and CdTe 

laboratories were completed in April 2007. 

•	 Restarted full research activities in the User Characterization and Cell Reliability laboratories. 

•	 Completed facility and environment, safety, and health (ES&H) requirements to allow functionality 

of 50% of major laboratory equipment in Contacts, CdTe, and CIGS laboratories. 

•	 Placed the order for the CIGS PDIL platform chamber and related sputter chambers. 

Future Directions 

•	 Complete ES&H and facilities requirements for full functionality of equipment in the remainder of 

the S&TF laboratories. 

•	 Finalize specification and engineering for the remaining components of the CIGS PDIL platform 

and place order(s). Finalize specification and engineering for initial components of CdTe PDIL 

platform and place order(s). 

•	 Assess strategies that can establish a key metric for ultimate device performance immediately 

following CIGS deposition. 

•	 Expand research on alternative processes for CIGS layer deposition. 

•	 Accelerate research on high-band-gap absorber layers for tandem-junction polycrystalline thinfilm PV devices. 

•	 Initiate research to foster partnerships with commercial glass companies to develop PV-specific 

products. 

1. Introduction directed at thin-film semiconductor materials, 

device properties, and fabrication processes to 

The research undertaken by the NREL improve the efficiency, stability, and cost of 

Polycrystalline Thin-Film Devices Group is photovoltaic solar energy conversion. This 

Photovoltaic R&D

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20
 

 

research can be broadly divided into three 

categories: (1) application of capabilities to assist 

industry and national research teams in 

addressing current problems; (2) exploration of 

specific techniques and processes to develop and 

transfer technology improvements that industry will 

soon need; and (3) providing the understanding 

that builds a solid technical foundation for the 

continuing improvement of thin-film PV products. 

Within this framework, the project supports CIGS, 

CdTe, and TCO thin-film technologies and 

develops procedures needed to understand and 

quantify the cell-level reliability of PV devices. 

Activities and time frames are consistent with 

those identified in the DOE Solar Program MultiYear Technical Plan and related Technology 

Roadmaps. 

NREL’s CIGS and CdTe technologies lead the 

world in demonstrated cell performance, while 

innovations related to high-quality TCO 

technologies are being rapidly assimilated into the 

thin-film industry. Because thin-film PV can 

generate lower cost PV electricity (in dollars per 

watt) than many historical alternatives, thin-film PV 

is the fastest growing segment of the PV market. 

Providing innovations and a solid technical 

foundation for this rapidly expanding industry is at 

the heart of the efforts of the NREL Polycrystalline 

Thin-Film Devices Group. 

2. Technical Approach 

The project is composed of research associated 

with CdTe and CIGS device development. FY 

2007 funding for cell-level reliability was derived 

partly from the CdTe/CIGS device activity, and 

partly from the Module-Reliability Project. FY 2007 

activities related to TCO research were also 

funded partly through the CdTe/CIGS device 

activity, and partly through an NREL Fellows 

Research Grant (providing approximately one fulltime graduate student). Research tasks are 

described below. 

2.1 CdTe Research 

•	 Baseline cell research, including advanced 

TCO development for superstrate devices 

•	 Functionality and optimization of buffer layers 

•	 Junction studies, including defect evolution 

during CdCl2 treatment and contacting 

• Wide-band-gap absorbers for polycrystalline 

thin-film tandem solar cells 

•	 Mechanisms of CdTe intrinsic device stability. 

2.2 CIGS Research 

•	 Baseline cell research, including advanced 

TCO development for substrate devices 

•	 Examination of device performance in 

progressively thinner absorber layers 

•	 Improved processes for larger-scale 

manufacture of CIS with high-performance 

•	 Examination of CIGS intrinsic device stability 

modes. 

3. Results and Accomplishments 

Efforts in FY 2007 were dominated by activities 

associated with moving the research equipment of 

the Polycrystalline Thin-Films Group from their 

previous locations in the SERF laboratory building 

to new locations in the S&TF laboratory building. 

Although the amount of time necessary for actual 

movement of the equipment was relatively short 

(and contracted to external groups), a significant 

amount of work on the part of the staff was 

required before and after each move. This 

included disconnection of utilities, separation of 

discrete components, and compliance with ES&H 

pre-move procedures. After the move, technical 

staff performed the equipment reconstruction and 

modifications needed; coordinated the work of 

temporary technicians, S&TF fit-up building 

contractors, and NREL facilities staff; and 

established (or reestablished) the required ES&H 

documentation and compliance. By the end of FY 

2007, 100% of the equipment had been moved to 

the S&TF, 100% of all SERF laboratories had 

been evacuated per ES&H requirements, and 

approximately 50% of the S&TF-located 

equipment was operational per ES&H 

requirements. We estimate that activities 

associated with the S&TF move consumed 50%-

80% of the technical staff’s time in FY 2007. 

The following discussion describes results and 

accomplishments that were achieved in addition to 

SERF-S&TF move-related activities. 

The NREL Polycrystalline Thin-Film Devices 

project leads the world in the development of 

CdTe and CIGS thin films and related materials for 

use in high-performance, stable, single-junction 

solar cells. The project objectives support nearterm manufacturing, build a knowledge and 

technology base for future manufacturing 

improvements, and sustain innovation that 

supports progress toward the long-term Solar 

Energy Technologies Program goal of 15%-

efficient commercial modules. Over the past 

decade, we have steadily improved the quality of 

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the layers in the CdTe device and achieved a 

world-record efficiency of 16.5%. Our work in 

CIGS set the world record in 2006 at 19.52%. Our 

polycrystalline tandem solar cells of semitransparent CdTe atop CIS set a record of 15.3%. 

In FY 2007, shortly after the recommissioning of 

the CIGS deposition capabilities in the S&TF in 

August, a CIGS device was fabricated that that 

has since been confirmed at 19.88% efficiency. 

This result exceeds the previous world-record 

efficiency (19.52%) by a noticeable margin and 

has indicated a pathway toward even higher 

efficiency. A publication describing the process 

improvements that yielded these results was being 

finalized at the end of FY 2007. The result also 

confirms that the equipment and procedures used 

for our CIGS research have survived the rigors 

and design modifications associated with the 

move, and they can again be relied upon to 

produce the high baseline performance that has 

placed NREL at the forefront of the CIGS research 

community. 

The reestablishment of CdTe device activities in 

FY 2007 was guided primarily by deliverables 

associated with a funds-in cooperative research 

and development agreement (CRADA) that began 

in mid-FY 2007 with Primestar Solar. (Note that 

FY 2007 interactions related to the Primestar 

CRADA were very beneficial to Primestar. Work 

at the end of the fiscal year resulted in cell 

performance levels well above 10%; major 

contributions were made in the back contact, 

CdCl2, and CdTe deposition processes.) 

These activities required the reestablishment of 

routine CdCl2 processing, deposition of ZnxSnOy 

and related buffer-layer materials, deposition of 

Cd2SnO4 TCO materials, formation of ZnTe:Cu/Ti 

contacts, formation of graphite-paste contacts, and 

procedures related to baseline reliability 

measurements. By the end of FY 2007, all these 

processes and procedures were operational. 

Work was ongoing to reestablish the ES&H 

documentation and equipment modifications 

required for the deposition of CdTe by close-space 

sublimation (CSS) and SnO2/SnO2:F by chemical 

vapor deposition (CVD). 

Activities related to the development of novel 

TCOs focused on two material systems. The first 

was the development of an aluminum-doped zinc 

oxide (ZnO:Al) material designed to achieve 

higher infrared (IR) transmission for use in CIGS 

solar cells. Unlike “standard” ZnO:Al that contains 

~2 wt.% Al2O3 and is sputter-deposited in pure 

argon, our research determined that if a 

hydrogen/argon sputtering ambient is used, the 

Al2O3 content can be reduced to ~0.05 wt.% to 

provide significantly improved electron mobility 

and higher carrier activation. Because fewer free 

carriers (electrons) are required to produce a lowresistivity film, higher IR transparency results. 

Preliminary incorporation of this new composition 

of ZnO:Al into CIGS devices has yielded quantum 

efficiencies higher than those achieved on worldrecord CIGS devices. Therefore, further testing 

was actively proceeding at the end of the fiscal 

year. 

The second TCO project involves the development 

of a ZnO + MgO alloy (ZnMgO) that may afford the 

ability to control the valance-band discontinuity at 

the Zn(Mg)O/CdS interface, thereby allowing 

higher open-circuit voltages at higher gallium 

concentrations. The material may also have 

greater resistance to environmental corrosion 

when compared with that of ZnO. Initial analysis 

of ZnMgO fabricated by radio-frequency sputter 

deposition has been encouraging, and results 

related to the incorporation of the layer into CIGS 

devices are expected in early FY 2008. 

The final FY 2007 highlighted accomplishment is 

the placing of the order for the initial components 

of the PDIL CIGS platform tool. The components 

of this tool will allow CIGS deposition within the 

boundaries of the PDIL design guidance (i.e., 6-in. 

x 6-in. format, multiple runs per chamber service 

(up to 100), 1.1-m transfer height, pod transfer, 

cassette loading, and robot compatibility). The 

order was placed with DCA Instruments in 

Finland, and acceptance testing by NREL staff at 

the DCA factory is scheduled for mid-FY 2008. 

The placement of this order marks a significant 

step toward establishing the first of the PDIL 

platforms being designed by the Polycrystalline 

Thin-Film Devices Group. 

4. Planned FY 2008 Activities 

In the early part of FY 2008, significant effort will 

continue to be directed at reestablishing research 

capabilities in the S&TF, specifically in the area of 

CSS CdTe and CVD TCO deposition. This and 

other planned activities are as follows: 

•	 Complete fit-up of the group’s S&TF 

laboratories to attain the functionality of the 

previous SERF laboratories. 

•	 Finalize specification and engineering for the 

remaining components of the CIGS PDIL 

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22
 

platform, including the solution-growth CdS 

component. 

•	 Finalize specification for initial components of 

CdTe PDIL platform. 

•	 Assess strategies that can establish a key 

metric for ultimate device performance 

immediately following CIGS deposition. 

•	 Accelerate research on high-band-gap 

absorber layers for tandem-junction 

polycrystalline thin-film PV devices. 

•	 Expand the research into alternative 

processes for CIGS layer deposition. 

•	 Initiate partnerships with commercial glass 

companies to develop PV-specific products. 

5. FY 2007 Special Recognitions and Patents 

•	 T.A. Gessert was the Lead Symposium CoOrganizer for the Spring 2007 Meeting of the 

Materials Research Society (MRS) for a 

symposium on Thin Film Compound 

Semiconductor Photovoltaics. 

•	 M. Contreras has been selected as a 

Symposium Co-Organizer for the 2007 Spring 

Meeting of the MRS. 

•	 T.A. Gessert was elected chair-elect for the 

Vacuum Technology Division of the American 

Vacuum Society. His Chair responsibilities 

were to begin in January 2008. 

•	 U.S. Patent No. 7,179,677 B2, was awarded 

on February 20, 2007, for “ZnO/Cu(InGa)Se2 

Solar Cells Prepared by Vapor Phase Zn 

Doping” to K. Ramanathan, F.S. Hasoon, S.E. 

Asher, J. Dolan, and J.C. Keane. 

•	 A patent was filed, NREL (04-11) in May 2007 

titled “Transparent Conducting Oxides and 

Production Thereof,” by T.A. Gessert, Y. 

Yoshida, and T.J. Coutts. 

•	 A record of invention was filed with DOE, IR 

07-42, in September 2007 titled “High Quality 

Doped ZnO Thin Films,” by T.A. Gessert, J. 

Duenow, T. Barnes, and T.J. Coutts. 

6. Major FY 2007 Publications 

•	 T. M. Barnes, X. Wu, J. Zhou, A. Duda, J. van 

de Lagemaat, T.J. Coutts, C.L. Weeks, D.A. 

Britz, and P. Glatkowski, “Single-Wall Carbon 

Nanotube Networks as a Transparent Back 

Contact in CdTe Solar Cells,” Appl. Phys. 

Lett., 90 (24), 243503 (2007). 

•	 M. Contreras, T. Barnes, J. van de Lagemaat, 

G. Rumbles, T.J. Coutts, C. Weeks, P. 

Glatkowski, I. Levitsky, J. Peltola, and D.A. 

Britz, “Replacement of Transparent 

Conductive Oxides by Single-Wall Carbon 

Nanotubes in Cu(In,Ga)Se2-Based Solar 

Cells,” J. Phys. Chem. C: Nanomaterials and 

Interfaces, 111 (38), 14045-14048 (2007). 

•	 R.G. Dhere, K. Ramanathan, J. Scharf, H. 

Moutinho, B. To, A. Duda, and R. Noufi, 

“Investigation of Cd1-xMgxTe Alloys for 

Tandem Solar Cell Applications,” Proc. 4th 

WCPVEC, Piscataway, NJ, IEEE, 546 (2006). 

•	 J. N. Duenow, T.A. Gessert, D.M. Wood, T.M. 

Barnes, B. To, and T.J. Coutts, “Transparent 

Conducting Zinc Oxide Thin Films Doped with 

Aluminum and Molybdenum,” J. Vac. Sci. 

Tech. A, 25(4), 955-960 (2007). 

•	 T.A. Gessert, S. Asher, S. Johnston, A. Duda, 

and M.R. Young, “Formation of ZnTe:Cu/Ti 

Contacts at High Temperature for CdS/CdTe 

Devices,” Proc. 4th WCPVEC, Piscataway, NJ, 

IEEE, 432-435 (2006). 

•	 T.A. Gessert, S. Asher, S. Johnston, M. 

Young, P. Dippo, and C. Corwine, “Analysis of 

CdS/CdTe Devices Incorporating a ZnTe:Cu 

Contact,” Thin Solid Films, 515, 6103-6106 

(2007). 

•	 X. Wu, J. Zhou, A. Duda, Y. Yan, G. Teeter, S. 

Asher, W.K. Metzger, S. Demtsu, S.H. Wei, 

and R. Noufi, “Phase Control of CuxTe Film 

and its Effects on CdS.CdTe Solar Cell,” Thin 

Solid Films, 515 (15), 5798-5803 (2007). 

•	 J. Zhou, X. Wu, A. Duda, G. Teeter, and S.H. 

Demtsu, “Formation of Different Phases of 

CuxTe and Their Effects on CdTe/CdS Solar 

Cells,” Thin Solid Films, 515 (18), 7364-7369 

(2007). 

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7. Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal 

Investigator 

Location/e-mail Description/Title of 

Research Activity 

FY 2007 

($K) 

Cost 

Share 

($K) 

Primestar Solar 

Fred Seymour 

Golden, CO 

fred.seymour@primestarsolar.com 

Scale of CdTe Photovoltaic 

Device Processes for 

Commercial Applications 

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____________________________________________________________________________________ 

 

____________________________________________________________________________________ 

Electronic Materials and Devices 

Process Technology and Advanced Materials 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact:	 David Ginley (NREL), 303-384-6573, david_ginley@nrel.gov 

DOE HQ Technology Manager:	 Jeffrey Mazer, 202-586-2455, jeffrey.mazer@ee.doe.gov 

FY 2007 Budget:	 $764K* 

*Reference funding table in appendix 

Objectives 

•	 Develop organic-based thin-film photovoltaics (OPV). 

•	 Apply combinatorial methods to identify optimum material and demonstrate conductivity 

>6200 S/cm in transition metal oxides. 

•	 Develop novel solution-based processes for photovoltaics (PV), including metallization and 

copper indium gallium selenide (CIGS). 

Accomplishments 

•	 Developed new combinatorial capabilities for Raman, work function, deposition, and elemental 

analysis; identified two systems with conductivities >6000 S/cm. 

•	 Filed applications for six patents on the direct printing of precursors for copper indium diselenide 

(CIS) solar cell absorbers and metallization for Si solar cell contacts. 

•	 Developed state-of-the-art infrastructure for OPV; obtained a 4.2%-efficient bulk heterojunction 

cell and >3% inverted OPV solar cells using zinc oxide (ZnO) anodes; and initiated reliability 

lifetime studies. 

Future Directions 

•	 Develop improved polymers for OPV and address interface issues to achieve a 6%-efficient solar 

cell with >2000 hour stabilities. 

•	 Transfer ink-based technology to partners. 

•	 Initiate partnerships with awardees in the Solar America Initiative (SAI). 

1. Introduction 

The Process Technology and Advanced Concepts 

Group supports the DOE Solar Program by 

developing new process technology and advanced 

device concepts in areas that support a wide 

range of solar technologies. First, we apply our 

capabilities to assist industry and the national 

research teams in addressing current problems. 

Second, we explore specific techniques and 

processes to develop and transfer technology 

improvements that industry will soon need. Finally, 

we seek to create new technologies and lead the 

development of the knowledge base and tools for 

the future of photovoltaics. Through these 

activities, the group analyzes and develops PV 

technologies at the cell and module level, in all of 

the application targets and time frames identified 

in the DOE Solar Program Multi-Year Technical 

Plan. 

The relatively low cost of electric power in the 

United States will drive PV production to a lower 

cost-point than is needed in most of the rest of the 

world. This requires new processes that enable 

production methods that avoid vacuum processing 

(which is costly), minimize mechanical stress (to 

reduce breakage and increase yield), or 

dramatically increase throughput. The exploration 

and development of technologies to exploit these 

three opportunities compose the primary tasks of 

the Process Technology and Advanced Concepts 

Group. 

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2. Technical Approach 

Process and Advanced Concepts 

•	 Jointly with Sandia National Laboratories 

(SNL), develop next-generation OPV devices 

and begin to look at issues of scalability and 

lifetime 

•	 Develop combinatorial materials science 

deposition, diagnostics, and data analysis 

tools and explore application to transparent 

conducting oxide (TCO) materials; these will 

be applied to silicon (Si), CIS, and cadmium 

telluride (CdTe) as well as to OPV 

•	 Develop ink-jet processing of electronic 

materials for application to metallization and 

semiconductor materials for Si, CIS, and OPV 

•	 Develop an advanced laser process station for 

the laser scribing, laser annealing, and laser 

recrystallization of PV device structures 

•	 Initiate Cooperative Research and 

Development Agreements (CRADAs) (e.g., 

HelioVolt, Evergreen Solar, BP, Konarka, 

TDA, Plextronics, and XJET). 

3. Results and Accomplishments 

Process and Advanced Concepts 

3.1 Jointly with SNL, develop next-generation OPV 

devices and begin to look at the issues of 

scalability and lifetime. Our OPV program has 

begun to gain national and international attention 

as a result of our integrated approach to new 

acceptor and donor development along with our 

developments in new process technology, new 

characterization tools specific to OPV, and initial 

results addressing the lifetime (intrinsic and 

extrinsic) of the devices. Figure 1 shows some 

early encapsulation results for a bulk heterojunction device. 

Fig. 1. Initial aging data for a bulk heterojunction 

device with various encapsulation techniques 

showing strong extrinsic effects, potentially of 

water and oxygen (accepted for publication in 

Solar Energy Materials). 

Table 2. Deposition Results 

Table 2 shows how the hole injection layer— 

poly(3,4-ethylenedioxythiophene)-polystyrene 

sulfonate (PEDOT/PSS)—can be deposited by 

spin coating, or the more scalable ink-jet printing, 

or ultrasonic spray deposition with nearly identical 

results. Recently, we have been able to spray the 

bulk heterojunction in air as well with >2% 

conversion efficiency over a 1-in.-square device. 

3.1 Develop combinatorial materials science 

deposition, diagnostics, and data analysis tools for 

application TCO materials. These will be applied 

to Si, CIS, and CdTe as well as OPV. The 

combinatorial tool development has continued with 

the addition of new tools for mapping work 

function, optical properties, and conductivity. We 

have now automated many of the tools and the 

associated data collection to move toward an 

integrated data management system. These have 

been applied to an increasingly broad range of 

problems, with a focus on TCOs. A key focus has 

been the continued investigation of amorphous 

TCO materials because of their excellent 

conductivity, transparency, smoothness, 

processability, and low-temperature deposition. 

Fig. 2. (a) Conductivity (σ), (b) carrier 

concentration (N), and (c) Hall mobility (μ).of the 

amorphous films vs. oxygen content during 

sputtering. 

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Fig. 3. (a) Hall mobility (μ) versus carrier 

concentration (N) for amorphous and crystalline 

compositions denoted by A and X respectively, 

with a dashed line included as a guide to the eye 

and (b) slope of mobility versus temperature at 

various values of N. 

3.3 Ink-jet processing of electronic materials: 

application to metallization and semiconductor 

materials for Si, CIS, and OPV. This work has 

focused on the development of new inks for CIGS 

solar cells and inks for contacts to PV devices. In 

the former case, this project focuses on the 

development of an atmospheric and direct write 

ink-based approach to CIS solar cells. 

Accomplishing this involves a multistage process 

of developing precursor inks for the various 

components of the cell and then integrating them 

via ink-jet printing and rapid thermal processing 

into actual devices. This period we continued to 

develop our new copper selenide (CuSe) ink, 

which has a much more appropriate Cu/Se ratio 

and is leading to improved films with stoichiometry 

control. We have incorporated our Ga precursor 

with our In precursor to produce good IGS films. 

The combined process solution precursors with 

rapid thermal or FASST processing has led to the 

development of films with very good grain 

structures, as seen in Figure 4. 

Fig. 4. Ink-based precursors incorporated with 

FASST processing to produce large-grain CIS. 

Scale bar is one micron. 

The University of Minnesota has continued to 

focus on the development and processing of 

precursors to ZnO films. The primary focus this 

period has been to continue to evolve the Gadoped ZnO materials and to work on film 

formation. We have also begun to synthesize new 

precursors for the TCOs at NREL with a focus on 

IZO. A route has been identified that produces 

amorphous material at relatively low temperature, 

but the film quality is not good. Work has focused 

on optimizing film deposition for the HelioVolt 

process and scaling to 6-in. wafers. Using this 

approach, we now have over 4%-efficient solar 

cells over large areas. We have continued to 

improve solution-based metallizations by ink-jet 

and have demonstrated that we can write nickel 

(Ni) over scribed cell materials with good 

conductivity. This project should lead to a novel, 

low-cost, scalable production technique for CIS 

solar cells. 

In the latter case, this includes Ni/silver (Ag) and 

Ni/Cu for CIGS and Ag with a variety of burnthrough and doping agents for Si solar cells. We 

have been able to achieve up to 13%-efficient Si 

solar cells on small areas (>1 cm2

) with printed 

contacts and burn-through agents and are scaling 

the process for 6-in. wafers through the 

implementation of two next-generation printing 

systems. Figure 5 is a close-up of the Ag lines on 

Si showing a width of 40-50 μm for a multilayer 

line with a thickness of 10 μm. 

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Fig. 5. Both drop on demand and multilayer 

printing of Ag on silicon nitride coated Si wafer. 

3.4 Develop an advanced laser process station for 

the laser scribing, laser annealing, and laser 

recrystallization of PV device structures. Figure 6 

illustrates the current version of the laser process 

station. It has an excimer, an yttrium aluminum 

garnet (YAG), and a CO2 laser to be able to scribe 

and process from the ultraviolet to the infrared. 

Current optics allow for 1-μm spot size with 0.1-μm 

table positioning accuracy. The system has built-in 

particle removal and beam positioning and 

indexing systems. 

Fig. 6. Laser process station (current version). 

4. Planned FY 2008 Activities 

The primary focus will be on the following: 

•	 Continued improvement of OPV devices, 

processing to larger areas and addressing 

reliability and packaging issues 

•	 Technology transfer of ink-based contacts and 

absorbers and development of nextgeneration inks and processing 

•	 Use of laser processing to develop large-grain 

template layers for thin-film Si on glass 

•	 Development of new TCOs with a focus on 

very high performance, stability, interfacial 

chemistry, and work function; continued 

examination of amorphous systems and 

development of ink-based approaches to highperformance TCOs. 

5. FY 2007 Special Recognitions, Awards, and 

Patents 

Numerous project staff has been chosen by their 

peers to lead professional organization activities 

as general chair, program chair, session 

organizer, session chair, tutorial instructor, and 

similar honors. The more notable of these 

recognitions are: 

•	 David Ginley served as volume organizer for 

the Materials Research Society’s MRS Bulletin 

Special Addition on Harnessing Materials for 

Energy, a two-year project published in April 

•	 David Ginley is editor of a Springer book on 

TCOs, to be published this year 

•	 David Ginley, John Perkins, and Sean 

Shaheen have all been symposia organizers 

for MRS, SPIE, and the American Physical 

Society (APS) for PV or Combi-related topics. 

•	 David Ginley and Joseph Berry received the 

DOE Illuminating Ideas Award for their joint 

effort with Pacific Northwest National 

Laboratory to develop new TCOs for organic 

light-emitting diodes based on the Combi work 

developed in the PV program. 

•	 David Ginley is chairing the sustainable 

energy symposia at the first MRS/Chinese 

MRS meeting. 

The group has also generated new intellectual 

property: 

•	 Novel process approaches for InZnO 

•	 Ink precursors for CIGS materials 

•	 New contact metallizations for ink-jet contacts 

to solar cells. 

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6. Major FY 2007 Publications 

E. Bundgaard, S.E. Shaheen, F.C. Krebs, and 

D.S. Ginley, “Bulk heterojunctions based on a low 

band gap copolymer of thiophene and 

benzothiadiazole,” Solar Energy Materials & Solar 

Cells 91(17), 1631-1637 (2007). 

M.S. Dabney, and D.S. Ginley, “In situ etch rate 

measurements of thin film combinatorial libraries,” 

Applied Surface Science 254(3), 687-691 (2007). 

M.S. Dabney, M.F.A.M. van Hest, C.W. Teplin, S. 

Arenkiel, J.D. Perkins, and D.S. Ginley, ”Pulsed 

laser deposited Nb doped TiO2 as a transparent 

conducting oxide,” Thin Solid Films 516(12), 4133­

4138 (2008). 

E. Fortunato, D. Ginley, H. Hosono, and D.C. 

Paine, “Transparent conducting oxides for 

photovoltaics,” MRS Bulletin 32(3), 242-247 

(2007). 

D.S. Ginley, C.J. Curtis, A. Miedaner, M.F.A.M. 

van Hest, and T. Kaydanova, “Metal inks from 

metal-organic precursor,” U.S. Pat. Appl. Publ., 11 

pp. (2008). 

A.B. Kozyrev, V.N. Osadchy, D.M. Kosmin, A. V. 

Tumarkin, T. Kaydanova, and D. Ginley, “Time 

tuning of ferroelectric film varactors under pulse 

voltages,” Applied Physics Letters 91(2), 

022905/1-022905/3 (2007). 

A.J. Leenheer, A. Miedaner, C.J. Curtis, M.F.A.M. 

van Hest, and D.S. Ginley, “Fabrication of 

nanoporous titania on glass and transparent 

conducting oxide substrates by anodization of 

titanium films,” Journal of Materials Research 

22(3), 681-687 (2007). 

A.J. Leenheer, J.D. Perkins, M.F.A.M. van Hest, 

J.J. Berry, R.P. O’Hayre, and D.S. Ginley, 

“General mobility and carrier concentration 

relationship in transparent amorphous indium zinc 

oxide films,” Physical Review B: Condensed 

Matter and Materials Physics 77(11), 115215/1­

115215/5 (2008). 

A. H. Mahan, S.P. Ahrenkiel, R.E.I. Schropp, H. Li, 

and D.S. Ginley, “A comparison of grain nucleation 

and grain growth during crystallization of HWCVD 

and PECVD a-Si:H films,” Thin Solid Films 516(5), 

529-532 (2008). 

D.C. Olson, S.E. Shaheen, R.T. Collins, and D.S. 

Ginley, “The Effect of Atmosphere and ZnO 

Morphology on the Performance of Hybrid Poly(3­

hexylthiophene)/ZnO Nanofiber Photovoltaic 

Devices,” Journal of Physical Chemistry C 

111(44), 16670-16678 (2007). 

D.C. Olson, Y.-J. Lee, M.S. White, N. Kopidakis, 

S.E. Shaheen, D.S. Ginley, J.A. Voigt, and J.W.P. 

Hsu, “Effect of Polymer Processing on the 

Performance of Poly(3-hexylthiophene)/ZnO 

Nanorod Photovoltaic Devices,” Journal of 

Physical Chemistry C 111(44), 16640-16645 

(2007). 

J. D. Perkins, M.F.A.M. van Hest, C.W. Teplin, 

M.A. Gillispie, M.F.A.M. van Hest, M.S. Dabney, 

J.D. Perkins, and D.S. Ginley, “Sputtered Nb- and 

Ta-doped TiO2 transparent conducting oxide films 

on glass,” Journal of Materials Research 22(10), 

2832-2837 (2007). 

J. Piris, N. Kopidakis, D.C. Olson, S.E. Shaheen, 

D.S. Ginley, and G. Rumbles, “The locus of free 

charge-carrier generation in solution-cast Zn1­

xMgxO/poly(3-hexylthiophene) bilayers for 

photovoltaic applications,” Advanced Functional 

Materials 17(18), 3849-3857 (2007). 

M.O. Reese, M.S. White, G. Rumbles, D.S. 

Ginley, and S. Shaheen, “Optimal negative 

electrodes for poly(3-hexylthiophene):[6,6]-phenyl 

C61-butyric acid methyl ester bulk heterojunction 

photovoltaic devices,” Applied Physics Letters, 

92(5), 053307/1-053307/3 (2008). 

B. Roy, J.D. Perkins, T. Kaydanova, D.L. Young, 

M. Taylor, A. Miedaner, C. Curtis, H.-J. Kleebe, 

D.W. Readey, and D.S. Ginley, “Preparation and 

characterization of sol-gel derived copperstrontium-oxide thin films,” Thin Solid Films 

516(12), 4093-4101 (2008). 

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Electronic Materials and Devices 

Silicon Materials and Devices 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contacts:	 Qi Wang (NREL, Wafer Si), 303-384-6681, qi_wang@nrel.gov 

 Howard Branz (NREL, Film Si), 303-384-6694, howard_branz@nrel.gov 

DOE HQ Technology Manager:	 Marie Mapes, 202-586-3765, marie.mapes@ee.doe.gov 

FY 2007 Budgets:	 $2,544K* 

*Reference funding table in appendix 

Objectives 

•	 Conduct scientific research on silicon Si-based materials and photovoltaic (PV) devices. 

•	 Demonstrate scalable epitaxy technique for film-Si on glass. 

•	 Understand Si based solar cells. 

Accomplishments 

•	 Achieved 19.1% heterojunction c-Si solar cell. 

•	 Achieved low temperature high growth rate epi-Si. 

•	 Developed the “cone kinetics” model to guide film-Si growth. 

•	 Developed high rate low gap a-SiGe:H solar cell by hot-wire chemical vapor deposition 

(HWCVD). 

•	 Completed the purchase of Si-cluster tool. 

Future Directions 

•	 Develop low-cost and high-efficiency film Si. 

•	 Develop high efficiency c-Si solar cell for manufacturing. 

•	 Develop novel Si for low cost and high efficiency Si. 

•	 Collaborate with U.S. industry partners. 

1. Introduction 

The Silicon Materials and Devices Group makes 

science and technology advances that can help 

meet the DOE Solar Energy Technologies 

Program (SETP) targets in the near-term, midterm and long-term. Silicon-based PV modules 

accounted for more than 96% of commercial sales 

in 2007, at a module selling price of $3-4 per watt 

(W). To reach the DOE 2020 goal of $0.06/kWh 

PV electricity, 18% wafer-based modules would 

likely need to sell at about $1/W. Fifteen percent 

film Si modules could sell at a slightly lower cost. 

This will require a combination of increases in cell 

efficiency and reduced costs in almost all 

components. Silicon remains the material of 

choice for terrestrial power photovoltaics (PV) 

because silicon is abundant, non-toxic and has 

demonstrated marketplace acceptance. There is 

a well-developed industrial base in all forms of 

silicon, and an enormous, rapidly growing, Si 

scientific literature that effectively leverages our 

PV research and development (R&D) spending. 

2. Technical Approach 

Our main project in the wafer silicon field in fiscal 

year (FY) 2007 was the development of silicon 

heterojunction (SHJ) surface passivation and solar 

cells. Superior passivation will lead to high opencircuit voltages and a key factor for high efficiency. 

In the film silicon field, we worked on developing

high efficiency low gap a-SiGe:H solar cell at 4 Å/s 

to harvest red light in the multijunction cell. We 

also worked on high quality low temperature 

epitaxial (epi) Si growth to use less Si material in 

c-Si solar cells on low-cost substrates. We 

purchased a versatile multi-chamber Si cluster tool 

for future advanced Si research and collaboration 

with industry partners. 

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3. Results and Accomplishments 

The SHJ is fabricated by putting ultra-thin 

hydrogenated amorphous silicon (a-Si:H) layers 

on c-Si and this passivation is a key step toward 

fabrication of high-efficiency silicon solar cells 

(21%-25% potential) at low temperatures (<250oC) 

with simple processing. Low-temperature is 

critical for PV-cost reduction through use of thinner 

wafers that incorporate less Si feedstock. In FY 

2007, we made our best SHJ cell to-date with a 

confirmed efficiency of 19.14% and a Voc of 678 

mV on p-type wafer. This is the best reported 

efficiency on a p-type wafer using an SHJ 

structure. We also achieved the best reported 

open circuit voltage of 0.689 V with a fill factor of 

0.81. This further demonstrates the passivation 

quality of hot-wire a-Si:H and positions our group 

to implement advanced device concepts requiring 

the extremely low SRV of the SHJ. We expect that 

PV cells employing SHJ passivation and/or 

emitters to be manufactured in the United States 

within the next 5 years and are collaborating with 

an industrial group to make this a reality. 

Fig.1 Silicon heterojunction solar cell on p-type 

wafer with a cell mask area of 0.9 cm2 

We also worked to improve the lowgap (bottom) 

cells for multijunction Si film PV by use of hot-wire

CVD a-SiGe:H at 4 Å/s to effectively convert red 

photons to electricity. Microcrystalline Si bottom 

cells have not yet been shown to have adequate 

properties at economical deposition rates, so 

commercially successful multijunction rely mainly 

upon a-SiGe:H bottom cells. When the Ge content 

is increased to reduce the bandgap, the PECVD aSiGe:H electronic quality declines precipitously. 

We have demonstrated remarkably high quality aSiGe:H by use of a Ta-filament in HWCVD and 

have a collaborative program with United Solar to 

implement high-quality graded-bandgap devices 

compatible with their multijunction approach. This 

project resulted in solar cells with initial efficiency 

of 8.65% at a 1.45 eV average bandgap. 

An important applied science achievement was 

application of the cone kinetics model of 2-phase 

microstructure formation to the problem of 

nanocrystalline and protocrystalline Si film 

formation. The ‘cone kinetics’ model, explains 

development of cone-shaped inclusions during 

nanocrystalline silicon film growth and during lowtemperature silicon epitaxy breakdown. We have 

now extended this model with a publication in 

Applied Physics Letters to protocrystalline (‘edge’) 

amorphous silicon, Si heterojunctions and other Si 

film morpholologies. The model predicts cone 

growth during thin-film deposition by plasmaenhanced and other chemical vapor deposition 

techniques when there is isolated nucleation of a 

second phase which grows faster than the first 

phase together with isotropic growth. 

Protocrystalline amorphous silicon and other 

embedded crystallite forms are understood as 

nucleation of a slightly slower-growing phase that 

is overtaken by the more rapid growing matrix 

phase. Our new ‘morphology phase diagram’ 

explains the continuously varying nanocrystalline 

film morphology with increasing H-dilution of silane 

precursors. This kind of scientific understand 

should lead to better control of morphologies 

critical to thin-film silicon solar cell performance. 

Our mid-term, high-risk goal (5-10 year) is to 

develop crystal Si films on glass that can be used 

to fabricate 15%-PV cells. We aim for crystal Si 

efficiencies at costs per unit area at manufacturing 

costs more characacteristic of thin-films 

(~$100/m2

). Development of this wafer-equivalent 

on glass requires excellent Si seed layers on the 

glass and a capability for rapid expitaxial 

thickening with about 5-20 microns of Si. We 

succeeded in making a 10-fold increase in 

epitaxial thickness from our best previous results; 

we can now grow 10 microns of film silicon by the 

scalable HWCVD technique at about 620°C. 

Even with improved epitaxy, defects in the Si films 

on glass will require hydrogen passivation, as in 

today’s high-performance multicrystalline PV cells. 

We have developed an inductively-coupled 

hydrogenation system combined with a rapid 

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thermal anneal capability. Nearly completed, this 

system will improve our film-PV solar cells once it 

has passed safety review. 

Despite worldwide attention, the problem of 

growing quality seed layers on glass for epitaxy 

has been difficult. Collaborators at Hahn-Meitner 

Institute in Berlin have provided us thin layers on 

glass made by the Al-induced layer exchange 

method; these have 10-50 micron grain sizes with 

only a weak preferential orientation. We 

demonstrated the ability to grow microns of highquality silicon on these seeds on borosilicate 

glass. We appear to grow epitaxially on each 

grain, but of course the grain boundaries 

propagate through the layer. We have negotiated 

a Cooperative Research and Development 

Agreement (CRADA) with a U.S. industrial partner 

who can make superior grains on inexpensive 

substrates. Through the CRADA, they will supply 

seeds and we will demonstrate epitaxial thickening 

and work toward PV devices on their layers. 

Fig. 2. Transmission electron micrograph of 

HWCVD epitaxial silicon layer grown on c-Si seed 

layer on borosilicate glass. Al-induced c-Si layer 

(from HMI-Berlin) shows grain bound boundary that 

propagates into epitaxy (arrow). 

Finally, our Group worked with the NREL 

Engineering Team toward construction and 

hookup of the first major cluster tool to be installed 

in NREL’s large Process Development and 

Integration Laboratory (STF-PDIL). The system 

has 8 deposition chambers, including both PECVD 

and HWCVD chambers with high-throughput 

deposition capabilities. There is also a sputtering 

chamber in which we can finish solar cells with 

conducting oxides after a-Si:H layer deposition. 

The substrate size is significant larger than our 

previous capabilities, up to 15.7 x 15.7 cm2

. In FY 

2008, this cluster tool will be a keystone of our 

thin-film deposition capabilities for amorphous 

silicon and wafer Si solar cell development. 

Fig. 3 Schematic diagram of Si cluster tool 

delivered to PDIL in STF building. 

4. Planned FY 2008 Activities 

Wafer Silicon 

•	 Purchase and install CZ-crystal grower. 

•	 Develop large size heterojunction solar cells. 

•	 Study surface and bulk passivation of c-Si. 

•	 Prototype interdigitated solar cell using 

heterojunction a-Si:H layer. 

Film Silicon 

•	 Improve low defect low temperature epitaxial 

growth. 

•	 Demonstrate epitaxial growth on candidate Si 

seed layers. 

•	 Develop hydrogenation methods for small 

grain Si film and devices. 

•	 Install the Si cluster tool and develop a-Si:H 

based films and devices in. 

5. FY 2007 Patents 

•	 Q. Wang and E. Iwaniczko, U.S. Patent No. 

7,122,736 B2. 

•	 P. Stradins and Q. Wang, “Rapid thermal 

processing by stamping,” filed 2007. 

•	 Q. Wang et al, “Low-temperature junction 

growth using hot-wire chemical vapor 

deposition,” filed 2007. 

6. Major FY 2007 Publications 

V. Gowrishankar, S. Scully, A. Chan, Q. Wang, H. 

Branz, and M.D. McGehee, “Exciton harvesting, 

charge transfer and charge-carrier transport in 

amorphous-silicon nanopillar / polymer hybrid 

solar cells,” J. Applied Physics, August 2007. 

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S. Datta, J. Cohen, Y. Xu, A. Mahan, and H. 

Branz, “Junction capacitance study of an oxygen 

impurity defect exhibiting configuration relaxation 

in amorphous silicon-germanium alloys deposited 

by hot-wire CVD,” J. Non-Crystalline Solids. 

D. Young, D. Williamson, P. Stradins, Y. Xu, L. 

Gedvilas, E. Iwaniczko, Y. Yan, H. Branz, and Q. 

Wang, “Nanostructure evolution in hydrogenated 

amorphous silicon during hydrogen effusion and 

crystallization,” Appl. Phys. Lett., Vol. 90, 81923-6, 

2007. 

C. Teplin, E. Iwaniczko, B. To, H. Moutinho, P. 

Stradins, and H. Branz, “Breakdown physics of 

low-temperature silicon epitaxy from silane 

radicals” Phys. Rev. B, Vol. 74, 235428, 2006. 

J. Doyle, Y. Xu, R. Reedy, H. Branz, and A. 

Mahan, “Film Stoichiometry and Gas Phase 

Chemistry in HWCVD of a-SiGe:H,” Thin Solid 

Films, 10 July 2007. 

H. Branz, C. Teplin, D. Young, M. Page, E. 

Iwaniczko, L. Roybal, R. Bauer, A. Mahan, Y. Xu, 

P. Stradins, T. Wang, and Q. Wang, “Recent 

advances in hot-wire CVD R&D at NREL: From 

18% silicon heterojunction cells to silicon epitaxy 

at glassw-compatible temperatures,” Thin Solid 

Films, 18 June 2007. 

J. Cohen, S. Datta, K. Palinginis, A. Mahan, E. 

Iwaniczko, Y. Xu, and H. Branz, “Defect analysis 

of thin film Si-based alloys deposited by hot-wire 

CVD using junction capacitance methods,” Thin 

Solid Films, 18 June 2007. 

V. Gowrishankar, S. Scully, M. McGehee, Q. 

Wang, and H. Branz, “Exciton splitting and carrier 

transport across the amorphous-silicon/polymer 

solar cell interface,” Appl. Phys. Lett, Vol. 89, 

252102, 2006. 

M. Du, H. Branz, R. Crandall, and S. Zhang, “Selftrapping enhanced carrier recombination at lightinduced boron-oxygen complexes in silicon,” Phys. 

Rev. Lett., Vol. 97, 256602, 2006. 

P. Stradins, C. Teplin, D. Young, Y. Yan, H. Branz, 

and Q. Wang, “Crystallization of thin-film Si 

monitored in real time by in-situ spectroscopic 

techniques,” J. Mat. Sci.: Mats in Electronics, Vol. 

18, S309-S313, 2007. 

Q. Wang, C. Teplin, P. Stradins, B. To, K. Jones, 

and H. Branz, “Significant improvement in silicon 

chemical vapor deposition epitaxy above the 

surface dehydrogenation temperature,” J. Appl. 

Phys., Vol. 100, 93520, 2006. 

D. Young, D. Williamson, P. Stradins, Y. Xu, L. 

Gedvilas, H. Branz, R. Reedy, A. Mahan, and Q. 

Wang “Rapid solid-phase crystallization of highrate, hot-wire-chemical-vapor deposited 

hydrogenated amorphous silicon” Appl. Phys. Lett. 

Vol. 89, 161910, 2006. 

Q. Wang, M. Page, E. Iwaniczko, Y.Q. Xu, L. 

Roybal, R. Bauer, D. Levi, Y. Yan, D. Meier, T. 

Wang, and H. Branz, “Silicon heterojunction solar 

cells by hot-wire CVD,” Solar World Congress 

2007 Beijing, China, 2007. 

D. Levi, E. Iwaniczko, Q. Wang, and H. Branz, 

“Materials Optimization for Silicon Heterojunction 

Solar Cells Using Spectroscopic Ellipsometry,” 

Proc. MRS Spring Meeting Symposium A, 2007. 

P. Stradins, O. Kunz, D. Young, Y. Yan, Y. Xu, R. 

Reedy, H. Branz, A. Aberle, and Q. Wang, 

“Comparative Study of Solid-Phase Crystallization 

of Amorphous Silicon Deposited by Hot-wire CVD, 

Plasma-Enhanced CVD and Electron Beam 

Evaporation,” Proc. MRS Spring Meeting 

Symposium A, 2007. 

C. Teplin, Q. Wang, H. Branz, K. Jones, and P. 

Stradins, “Epitaxy at 100 nm/min by Hot-Wire 

Chemical Vapor Deposition onto Silicon Wafers at 

500 to 700°C,” Proc. MRS Spring Meeting 

Symposium A, 2007. 

Q. Wang, M. Page, E. Iwaniczko, Y. Xu, L. Roybal, 

R. Bauer, D. Levi, Y. Yan, T. Wang, and H Branz, 

“High open-circuit voltage in silicon heterojunction 

solar cells,” Proc. MRS Spring Meeting 

Symposium A, 2007. 

D. Meier, M. Page, E. Iwaniczko, Y.Xu, Q. Wang, 

and H. Branz, “Determination of Surface 

Recombination Velocities for Thermal Oxide and 

Amorphous Silicon on float zone silicon,” Proc. 

17th Workshop on Crystalline Silicon Solar Cells 

and Modules, pp. 214-217, August 2007. 

T.H. Wang, M.R. Page, E. Iwaniczko, Y. Xu, Y. 

Yan, L. Roybal, D. Levi, R. Bauer, H. M. Branz, 

and Q. Wang, “High-efficiency p-type silicon 

heterojunction solar cells,” 21st European 

Photovoltaic Solar Energy Conference 

Proceedings, Dresden, Germany, 2006. 

33

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Electronic Materials and Devices
 

 

 

____________________________________________________________________________________ 

Electronic Materials and Devices 

Cell and Module Stability & Reliability
 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Tom McMahon, 303-384-6762, tom_mcmahon@nrel.gov 

DOE HQ Technology Manager: Dan Ton, 202-586-4618, dan.ton@doe.gov 

FY 2007 Budget: $1,218K (NREL) 

Objectives 

•	 Confirm reliability of new photovoltaic packaging materials and strategies to insure a 30-year 

module life of primarily industrial collaborations. 

•	 Identify module reliability problems with developing technologies. 

•	 Develop and/or acquire measurement techniques for module failure diagnostics. 

•	 Support collaborative R&D activities of DOE national laboratories, universities, and industry 

partners that focus on the identification, study, and mitigation of degradation mechanisms 

observed in advanced thin-film and crystalline modules. 

Accomplishments 

•	 Measured adhesion, cohesion, formation of T-F weak diodes, shunt, and series resistance 

problems with aging, water ingress. 

•	 Offered Accelerated Aging Workshops, along with Sandia National Laboratories, to replace ThinFilm Partnership reliability teams. 

•	 Identified module-level packaging issues such as: 

o	 Alternatives to double glass for thin films (soft backsheets and hard coat barrier films). 

o	 EVA substitutes that are cheaper/better perhaps without transparency. 

o	 Hot/Humid survival, since field and 85%-85°C stress survival depend on adhesion, 

cohesion and water diffusion barriers. 

o	 Moisture, which is relevant properties of polymers and coatings measured, by modeling 

of moisture ingress and egress into module structures. 

Future Directions 

•	 Identify emerging module reliability issues, such as water and heat stress to CdTe and CIGS. 

•	 Research and identify collaborations on barrier coatings. 

•	 Identify specific failure mechanisms with IR images. 

• Support Solar America Initiative’s SAI reliability teams, PV industry and suppliers. 

 ___________________________________________________________________________________ 

1. Introduction 

The development of advanced (e.g., second- and 

third-generation devices) PV technologies requires 

a thorough stage-gate type assessment of the 

technology’s stability (e.g., degradation vs. 

exposure to the environment) and reliability 

(service lifetime, failure mechanisms, etc.). Such 

an assessment/evaluation is as critical as the 

technology’s efficiency, costs, scale-up, and other 

manufacturing-related requirements. This 

agreement will serve as a consolidated (formerly 

these efforts were spread over several research 

tasks) and focused function to address the PV 

technologies’ near- to long-term stability and 

reliability attributes and/or issues. The advanced 

technology options that are and will continue to be 

generated by the University and Exploratory 

Research and Electronic Materials and Devices 

projects and, most likely, by several of the SAI’s 

Technology Pathway Partnerships (TPP) projects 

will be addressed with respect to the early stagegate criteria for stability and reliability for any 

technology. In addition, the various technical and 

material issues identified will be scientifically 

addressed (in close collaboration with the 

developers) in order to help mitigate the 

issues/shortcomings. 

Photovoltaic R&D

Fundamental Research

Electronic Materials and Devices

34
 

 

 

2. Technical Approach 

“Collaborative development (with industry) of 

improved materials (minimodules, backsheets, 

encapsulants)”, is actually a more accurately 

stated fundamental research and development 

(R&D) assessment of packaging 

(encapsulants/backsheets) approaches developed 

in-house and externally with many collaborators 

that are critical to predicting the durability, 

reliability, performance, lifetime of cells and 

modules for all technologies, and especially for 

particular thin-film constructions. Industry 

representatives regularly come through NREL 

asking for R&D advice, testing, and evaluation 

based on our experience with a wide range of 

approaches and based on the testing capability we 

have developed. This first activity ($731K) goes 

hand-in-hand with the second activity, which is to 

develop and apply measurement techniques to 

characterize the performance of these 

encapsulatns/backsheets provided by 

collaborators. 

3. Results and Accomplishments 

R&D on packaging approaches is fundamental to 

evaluating and improving module reliability and 

stability – in particular for new materials and 

technologies being developed. NREL’s expertise, 

developed with a cross-section of manufacturers 

and materials, is contributed in an unbiased 

manner in the National Teams and in open 

forums. An example is mentioned in the paper, 

Testing of Packaging Materials for Improved PV 

Module Reliability, when NREL researchers 

evaluated a number of new encapsulants and 

backsheets as improved packaging materials, and 

presented the results in the open literature. 

Examples of interactions across the industry, 

during FY 2007 alone, include: 

•	 Water vapor transmission testing of AKT 

organic multilayer samples 

•	 Non-disclosure agreement with Planar 

Systems, Inc., with tests on their coatings 

•	 Testing (tensile strength) of Madico backfoils 

as a function of damp heat exposure 

•	 Interactions with Deerfield Urethane to discuss 

potential use of thermoplastic polyurethane as 

a PV module encapsulant 

•	 Interactions with DuPont on potential 

approaches, particularly for outdoor 

weathering and characterization 

•	 Interactions with PPG on durability issues 

(their interest in becoming more involved as a 

supplier of glass substrates/superstrates for 

PV modules) 

•	 Interactions with Dow Chemical interested in 

possible applications of their various 

technologies 

•	 CRADA negotiations with BRP (ROI filed) 

• Interactions with Pilkington Glass on durability, 

glass in particular 

•	 Interactions with Saint Gobain, interested in 

polymer film materials for module construction; 

small module evaluation techniques 

•	 Evaluation of samples of low-temperature sol 

gel coated PET from Applied Films for 

potential improved backsheet materials 

•	 Meetings with Miasolé on packaging materials 

and options; building-integrated PV issues 

•	 Tests and collaboration with STR on their 

experimental EVA product 

•	 Interactions with Fraunhofer Institute for Solar 

Energy Systems on PV reliability (regarding 

European PV reliability program starting up) 

•	 Discussions with InnoSense LLC on 

depositing barrier coatings; request for 

assistance testing materials (silicon oxynitride 

barrier coatings on thin-film cells) 

•	 Testing of samples from Solar Roofing 

Systems prototype constructions 

•	 Advice and tests for DuPont and Dow Corning. 

4. FY 2007 Milestones 

•	 Correlate adhesion failure for and remove 

cores from in-house accelerated aged 

modules and field-aged modules using a 

torque test developed at Sandia National 

Laboratories with an added automated torque 

rate control. 

•	 Test efficacy of barrier coats and 

encapsulants, using our BEG (barrierencapsulant-glass) standard test, but with 

CIGS and CdTe cell films used instead of an 

Al-film. 

•	 Develop with industry collaboration new 

barrier coats and encapsulants, as well as 

provide adhesion and water vapor 

transmission values, water ingress modeling, 

and IR imaging for failure diagnostics. 

5. Planned FY 2008 Activities 

•	 Utilize compositional and thickness mapping 

data along with adhesion and WVTR data to 

examine a series of depositions on PET that 

further explore compositions from SiOx to 

SiOxNy to Si3N4. 

35

Photovoltaic R&D

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Electronic Materials and Devices
•	 Use torque adhesion measurement device to 

evaluate CIGS and CdTe modules undergoing 

Hot and Humid outdoor testing at FSEC. 

6. Major FY 2007 Publications 

D. Ton, J. Tillerson, T.J. McMahon, M.A. 

Quintana, K. Zweibel, "Accelerated Aging Tests in 

Photovoltaics,” sponsored by DOE’s EERE 

Technologies Program, Feb. 22-23, 2006, 

Baltimore, MD. 

J.G Jorgensen and T. J. McMahon, “Accelerated 

and Outdoor Aging Effects on Photovoltaic Module 

Interfacial Adhesion Properties,” Prog. Photovolt: 

Res. Appl. 2008; 16:1–9. 

M.D. Kempe, "Acetic acid production and glass 

transition concerns with ethylene-vinylacetate 

used in photovoltaic devices," Solar Energy 

Materials & Solar Cells 91 (2007) 315–329. 

Photovoltaic R&D

Fundamental Research

Electronic Materials and Devices

36
 

 

____________________________________________________________________________________ 

Measurements and Characterization 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contacts:	 Peter Sheldon (NREL, Primary Contact), 303-384-6533, 

peter_sheldon@nrel.gov 

Mowafak Al-Jassim (NREL), 303-384-6602, mowafak_aljassim@nrel.gov 

Sally Asher (NREL), 303-384-6450, sally_asher@nrel.gov 

Keith Emery (NREL), 303-384-6632, keith_emery@nrel.gov 

Dean Levi (NREL), 303-384-6605, dean_levi@nrel.gov 

DOE HQ Technology Manager:	 Marie Mapes, 202-586-3765, marie.mapes@ee.doe.gov 

FY 2007 Budgets:	 $8,110K 

Objectives 

•	 Provide routine and specialized measurement and characterization support for photovoltaic (PV) 

program research and industry teams. 

•	 Lead and contribute to collaborative research that addresses critical issues in PV technologies. 

•	 Develop and implement novel measurement techniques that enhance the ability to understand 

and advance fundamental PV research and development. 

Accomplishments 

•	 Provided measurement support in the areas of analytical microscopy, surface analysis, electrooptical characterization, and cell and module performance to more than 70 PV research partners 

in industry, academia, and NREL. 

•	 Maintained ISO 17025 accreditation for primary and secondary cell and module calibrations; 

completed periodic audits, maintenance of quality systems, calibrations, software, and 

documentation to meet A2LA requirements. 

•	 Initiated construction of an expansion of the Outdoor Test Facility (OTF), which will allow the 

Measurements and Characterization Group to support future Solar America Initiative (SAI) 

module test and evaluation needs. 

•	 Investigated the structural and electronic properties of nanocrystalline hydrogenated silicon (Si:H) 

films and devices with nanometer-scale resolution. 

•	 Completed an investigation of carrier depletion on individual grain boundaries in polycrystalline Si 

thin films using scanning capacitance microscopy. 

•	 Developed a luminescence spectrum imaging system for characterizing industrial silicon wafers 

and solar cells. 

•	 Initiated the design of an improved solar simulator that will reduce uncertainty in high-efficiency 

concentrator measurements. 

•	 Procured a new solar simulator to measure large-area modules up to 137 mm by 200 mm in size. 

•	 Completed study of the kinetics of Si wafer microcrack propagation as a function of processing. 

•	 Organized the 17th Workshop on Crystalline Silicon Solar Cell Materials and Processes. 

•	 Initiated development of a minority carrier lifetime measurement technique for integration into 

tools in the NREL Process Development and Integration Laboratory (PDIL). 

•	 Developed advanced multidimensional computer models for multicrystalline Si devices. 

•	 Developed a new moisture barrier package with very low water vapor transmission rates and 

excellent adhesion. 

•	 Investigated the materials chemistry of copper indium gallium diselenide (CIGS) on flexible 

substrates, leading to an improved understanding of long-term reliability. 

•	 Developed an improved understanding of cadmium telluride (CdTe) back contact reaction 

kinetics. 

•	 Initiated PDIL tool development projects for the large platen Auger electron spectroscopy tool and 

the small-spot X-ray photoelectron spectroscopy (XPS) tool. 

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____________________________________________________________________________________ 

 

Future Directions 

•	 Develop an integrated plan to provide priority support to the SAI Technology Pathway Partnership 

(TPP) awardees that meets their research and development (R&D) needs within the context of 

available resources. 

•	 Provide measurement support in the areas of analytical microscopy, cell and module 

performance, electro-optical characterization, and surface analysis to PV research partners in 

industry, academia, and NREL. 

•	 Maintain ISO accreditation for primary and secondary cell and module calibrations. 

•	 Complete the construction and fit-up of the OTF expansion project. 

•	 Install enhanced module measurement capabilities that will improve measurement uncertainty, as 

necessary to support the SAI. 

•	 Bring new solar simulators on line and make them compatible with our ISO quality systems. 

•	 Organize the 18th Workshop on Crystalline Silicon Solar Cell & Modules; this year’s theme is 

“Achieving Low-Cost Electricity (Grid-Parity) with Si PV.” 

•	 Design, procure, and install the Measurement and Characterization integrated PDIL tool set; 

integrated tools include the cluster tool robot, resonantly coupled photoconductive decay lifetime 

tool; photoluminescence (PL) imaging tool, spectroscopic ellipsometer tool, Auger electron 

spectroscopy tool, sputter/plasma etch tool, and the plasma-enhanced chemical vapor deposition 

(PECVD) tool. 

•	 Design, procure, and install the Measurement and Characterization stand-alone PDIL tool set; 

stand-alone tools include the X-ray photoelectron spectroscopy tool, scanning electron 

microscopy tool, atomic force microscopy tool, wet chemistry workstation tool, reflectometer, 

optical processing furnace, and the lifetime mapping tool. 

1. Introduction 

The Measurements and Characterization Group 

provides test, measurement, and analysis support 

and research for the National Center for 

Photovoltaics and the Solar Energy Technologies 

Program (SETP). It supports all photovoltaic (PV) 

material technologies and involves essential 

collaborations with external research partners in 

university and industry laboratories, PV 

manufacturers, and internal research groups. 

Each year, this group assists clients with tests and 

analyses of thousands of material and device 

samples, helping them to better understand and 

direct work on their research and commercial 

product development. We also serve as one of the 

test and evaluation facilities that the Solar America 

Initiative (SAI) uses to evaluate subcontract stagegate deliverables. 

These activities address one or more of the three 

areas crucial to meeting the DOE Office of Energy 

Efficiency and Renewable Energy (EERE) goal of 

reducing the levelized cost of energy for PV to 

$0.06/kWh by 2015. The three areas are (1) 

improving device and module performance, (2) 

reducing manufacturing costs, and (3) improving 

device and module reliability. This is accomplished 

by selecting projects that address key issues for a 

broad spectrum of technologies, including 

crystalline silicon (c-Si), amorphous silicon (a-Si), 

thin silicon, copper indium diselenide (CIS), 

cadmium telluride (CdTe), III-Vs, organic 

photovoltaics (OPV), and other future-generation 

materials. As shown in Figure 1, for each 

technology, we allocate resources to (1) provide 

routine and specialized measurement and 

characterization support for research and industry 

partners; (2) lead and contribute to collaborative 

research that addresses critical issues in these PV 

technologies; (3) develop and implement novel 

measurement techniques that enhance our ability 

to understand and advance fundamental PV R&D. 

Fig. 1. Schematic showing areas of research 

emphasis in Measurements and Characterization. 

Photovoltaic R&D

Fundamental Research

Measurements and Characterization

38
 

 

As indicated in Figure 1, these three areas are 

very complimentary and synergistic. For example, 

M&C Support work often leads to a Collaborative 

R&D project that addresses a specific issue 

thought to limit device performance or reliability, or 

alternatively, helps to identify a Technique 

Development project that will ultimately allow us to 

measure a critical device or material parameter. In 

turn, the development of enhanced measurement 

techniques allows us to continuously advance the 

state of the art and is necessary to help the PV 

community advance toward the 2015 SAI goals of 

lower costs, higher performance, and improved 

reliability. 

2. Technical Approach 

The project is composed of four core competency 

research tasks and a management/coordination 

task. The four research tasks are Analytical 

Microscopy, Cell and Module Characterization, 

Electro-Optical Characterization, and Surface 

Analysis. The major nonsupport research activities 

pursued in FY 2007 are outlined below by task. 

Although a significant portion of our work involves 

working with industry to solve research and 

manufacturing problems in a timely manner, these 

activities are not reported in this document 

because of their proprietary nature. During the 

past year, we have collaborated with well over 70 

research groups from industry, universities, and 

national laboratories. The FY 2007 highlighted 

milestones in each task are listed below, and 

additional details are provided in Section 3. 

2.1 Analytical Microscopy Task 

•	 Provided both routine and specialized 

measurement and characterization support for 

SETP PV research and industry teams. 

•	 Investigated the structural and electronic 

properties of nanocrystalline Si:H films and 

devices with nanometer-scale resolution. 

•	 Completed investigation of carrier depletion on 

individual grain boundaries in polycrystalline Si 

thin films using scanning capacitance 

microscopy. 

•	 Developed a luminescence spectrum imaging 

system for characterizing industrial silicon 

wafers and solar cells. 

2.2 Cell and Module Performance Task 

•	 Provided both routine and specialized 

measurement and characterization support for 

SETP PV research and industry teams. 

•	 Maintained ISO 17025 accreditation for 

primary and secondary cell and module 

calibrations. Completed periodic audits, 

maintenance of quality systems, calibrations, 

software and documentation to meet A2LA 

requirements. 

•	 Initiated the design of an improved simulator 

that will reduce uncertainty in high-efficiency 

concentrator measurements. 

•	 Procured a new solar simulator to measure 

large-area modules up to 137 mm by 200 mm 

in size. 

2.3 Electro-Optical Characterization Task 

•	 Provided both routine and specialized 

measurement and characterization support for 

SETP PV research and industry teams. 

•	 Completed a study of the kinetics of Si wafer 

microcrack propagation as a function of 

processing. 

•	 Organized the 17th Workshop on Crystalline 

Silicon Solar Cell Materials and Processes. 

•	 Initiated the development of minority carrier 

lifetime measurement techniques for 

integration into PDIL tools. 

•	 Developed advanced multidimensional 

computer models for multicrystalline Si 

devices. 

2.4 Surface Analysis Task 

•	 Provided both routine and specialized 

measurement and characterization support for 

SETP PV research and industry teams. 

•	 Developed a new moisture barrier package 

with very low water vapor transmission rates 

and excellent adhesion. 

•	 Investigated the materials chemistry of CIGS 

on flexible substrates, leading to an improved 

understanding of long-term reliability. 

•	 Developed an improved understanding of 

CdTe back contact reaction kinetics. 

•	 Initiated PDIL tool development projects for 

the large platen Auger electron spectroscopy 

tool and the small-spot XPS tool. 

Budget allocations by task are provided below. 

Task Title FY 2007 

Budget ($K) 

Analytical Microscopy 2,000 

Cell and Module Performance 1,699 

Electro-Optical Characterization 2,195 

Surface Analysis 1,495 

Management/Maintenance 721 

3. Results and Accomplishments 

Research results outlined in this section address 

only FY 2007 priority milestones, and these 

39

Photovoltaic R&D

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Measurements and Characterization
 

represent only a portion of all our support and 

research activities. Highlights for each task are 

outlined below. 

3.1 Analytical Microscopy Task 

Investigate the structural and electronic properties 

of nanocrystalline Si:H films and devices with 

nanometer-scale resolution: 

Nanocrystalline Si (nc-Si:H) materials are much 

more complicated than either amorphous or 

crystalline Si materials. They consist of 

nanocrystalline grains, grain boundaries, 

amorphous tissues, and voids. Therefore, 

structural and electrical characterization, on the 

atomic and nanometer scale, is required to better 

understand material properties. In collaboration 

with United Solar, we have investigated the Pdoping effects on the structure of nc-Si:H thin 

films. We observed for the first time P-doping 

induced nc-Si:H grains that were dispersed within 

the amorphous Si matrix. We also investigated the 

effects of light soaking and thermal annealing on 

the distribution of microelectrical conductivity, and 

experimentally solved the puzzle of light-soakinginduced open-circuit voltage (Voc) increases in aSi:H and nc-Si:H mixed-phased devices. These 

characterization results proved very useful for 

United Solar in its efforts to incorporate nc-Si:H 

into its production lines. 

The compositional, structural, and microelectrical 

properties of the Si:H films were investigated using 

complementary techniques that included 

secondary ion mass spectrometry (SIMS), Raman 

spectroscopy, atomic force microscopy (AFM), 

transmission electron microscopy (TEM), scanning 

Kelvin probe microscopy (SKPM), and conductive 

(C)-AFM. In the intrinsic and slightly P-doped Si:H 

films, the nc-Si:H grains aggregate to clusters, and 

SKPM and C-AFM images exhibit localized work 

function and conductivities. The local work 

function and conductivity of the nc-Si:H 

aggregates are significantly larger than those of 

the surrounding a-Si:H regions. However, as 

researchers increased the dopant concentration 

by adding small amounts of PH3 into the reactant 

gas during film growth, there was a large impact 

on film growth and structure. We found that (1) In 

order to reach similar crystallinity, the hydrogendilution ratio (H2/SiH4) needs to be doubled; (2) the 

PH3 was very efficiently incorporated, resulting in 

doping concentrations as high as ~1021/cm3

; and 

(3) the nc-Si:H grains no longer aggregate to 

clusters, and instead disperse randomly within the 

a-Si:H matrix. Based on the atomic hydrogenenhanced diffusion model for PECVD growth of 

nc-Si:H, we proposed a model to explain these 

doping effects. 

Along with measuring the changes of local 

conductivity in the a-Si:H and nc-Si:H mixedphase devices, we experimentally demonstrated 

that the light-soaking induced Voc increase 

originates from the degradation of the nc-Si:H 

phase. Using C-AFM, we measured the local 

electric current flow through the nc-Si:H 

aggregates. As shown in Figure 2, the current 

increases with the aggregation area. The current 

density decreased significantly by light soaking 

and recovered to a value similar to the original 

value with thermal annealing. These changes in 

current density explain the mechanisms of the 

light-soaking–induced Voc increase. 

Fig. 2 Local electric current through nc-Si:H 

aggregates as a function of the aggregation area. 

Linear fitting to the data represents the current 

density. The current density decreases with light 

soaking, and recovers after thermal annealing. 

Investigation of carrier depletion on individual 

grain boundaries in polycrystalline Si thin films 

using scanning capacitance microscopy. 

Grain boundaries (GBs) in polycrystalline Si thinfilm solar cells are believed to limit photovoltaic 

efficiencies. However, most measurement and 

characterization studies on the electronic 

properties of GBs were carried out on large 

samples that contain a high density of grains. As a 

result, one cannot resolve the electronic properties 

at a specific GB. In this study, in collaboration with 

NREL’s Si group, we carried out a nanometerresolution measurement of carrier depletion at the 

GBs using scanning capacitance microscopy 

(SCM). This nanometer-resolution measurement 

Photovoltaic R&D

Fundamental Research

Measurements and Characterization

40
allows us to examine the electronic properties of 

individual GBs. This is the first step toward our 

ultimate goal of correlating the electronic 

properties of specific GB structures. 

As shown in Figure 3, the SCM images exhibit the 

following features: (1) the carrier concentration is 

lower at locations near the GB edges in 

comparison to the central region of the grains; (2) 

the degree of depletion varies considerably from 

one GB to another—for example, GBs between 

grains A/B, A/C, and B/C clearly exhibit a high 

level of depletion, and in contrast, the GBs 

between A/D and A/E do not exhibit significant 

depletion; and (3) intragrain carrier depletion was 

also observed at point and line defects. 

Fig. 3 An SCM image taken on a polycrystalline Si 

thin film grown by HWCVD on an AIC-seed layer 

on a glass substrate. 

The direct measurement of the carrier depletion in 

the GBs demonstrates that the GBs in Si thin films 

indeed create charged gap states. The 

nonuniformity of the carrier depletion suggests that 

the gap states depend on specific GB structures, 

which should relate directly to the grain 

orientations and grain facets adjacent to the GB. 

The depletion around the intragrain defects 

indicates that the defects are charged and can be 

recombination centers, and thus harmful to device 

performance. Such in-depth studies are expected 

to have a direct impact on improving thin-film Si 

solar cells through understanding the local defect 

behavior at the GBs. 

Conduct electron backscatter diffraction studies of 

CdTe thin films: 

Electron-backscattered diffraction (EBSD) is a new 

technique that provides information about the 

crystalline structure of materials with high spatial 

resolution, in contrast to X-ray diffraction, which 

provides information on the bulk of the sample. In 

EBSD, diffracted electrons are collected and 

analyzed while the electron beam of a scanning 

electron microscope (SEM) scans the sample 

surface, providing diffraction patterns at every 

pixel of the SEM image. EBSD provides crystalline 

orientation maps, and it is able to identify 

crystalline phases and orientations with submicron 

spatial resolution. This capability enables the 

investigation of the misorientation between 

individual grains; the study of grain boundaries 

and special boundaries; the determination of grain 

size, grain distribution, and film texture; and the 

study of strain. EBSD requires a flat sample to 

avoid shadowing of the electrons from the detector 

by surface features. In this work, we investigated 

and developed procedures to prepare the surface 

of close-spaced sublimation (CSS) CdTe thin films 

necessary for producing artifact-free EBSD data. 

We found that polishing resulted in an amorphous 

layer on the surface and no Kikuchi pattern. 

However, ion-beam milling produced a relatively 

flat and good-quality surface, resulting in highquality patterns, and, consequently, excellent 

EBSD data. We used a combination of polishing 

and ion-beam milling or etching to study the 

crystalline structure of the CdTe film at different 

depths, as shown in Figure 4. 

Fig 4. EBSD data (band contrast and Euler map 

coloring) for an untreated CSS CdTe film after 

polishing with 0.05 μm alumina suspension for (a) 

30 s, (b) 120 s, and (c) 150 s. After polishing, each 

sample was ion-beam milled (5 keV, 1 min, 3°). 

The red lines are 60° <111> twin boundaries. 

41

Photovoltaic R&D

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We also used EBSD, in conjunction with other 

analytical techniques, to investigate the effects of 

the CdCl2 treatment, performed at different 

temperatures and times, on the recrystallization 

process of physical vapor deposition (PVD) CdTe 

thin films. This treatment is an important step in 

the production of high-efficiency solar cells, and 

needs to be optimized for the PVD CdTe films 

produced at NREL. The CdCl2 treatment in <111>­

oriented films shows ongoing recrystallization 

when performed at 350°C. When performed at 

400° and 420°C, the recrystallization process is 

complete and the microstructure reveals randomly 

oriented grains with a large variation in grain 

size—some grains reach dimensions exceeding 

40 μm. These films are so flat that good EBSD 

data could be obtained without any surface 

preparation. The large grains have different 

morphologies than the small grains do, and they 

have <111> orientation, indicating that, during the 

grain growth process, they enlarged at the 

expense of grains with less favorable orientations. 

The grains sizes observed for the PVD CdTe films 

are the largest obtained for CdTe films produced 

at NREL and are desirable for solar cells because 

of the reduction in grain boundary area. Another 

desirable characteristic is the fact that these films 

are very flat, making it easier for the application of 

a thin, homogeneous layer of a back-contact 

material. 

The EBSD analysis showed that both CSS and 

PVD CdTe films have a large density of 60° <111> 

twin boundaries, even after recrystallization, 

indicating a low formation energy for these 

interfaces. This capability to detect the distribution 

of two-dimensional boundaries is a unique 

capability of EBSD. Before EBSD was used, the 

most common way to study twins in CdTe films 

employed TEM, which is time-consuming and 

cannot provide an overall picture of the twin 

distribution. 

Investigate In2O3 and Al coverage and c-Si/a-Si 

interfaces in Si heterojunction cells: 

The texture of Si heterojunction (SHJ) cells is an 

important process for light trapping, which 

improves the efficiency of the cells. However, the 

textured surface can be a potential problem for the 

growth of uniformly and fully covered In2O3 and a 

back Al reflective layer. Therefore, it is critical to 

examine the quality of these layers for highefficiency SHJ cells. In collaboration with NREL’s 

Si Group, the front In2O3 coverage and back Al 

coverage of textured Si heterojunction cells was 

investigated using SEM. The c-Si/a-Si interface 

was also examined by high-resolution 

transmission electron microscopy (HRTEM). The 

thickness and uniformity of the a-Si layer and the 

quality of the a-Si/c-Si interface were examined by 

site-selected TEM preparation using our new 

focused ion beam (FIB) workstation and HRTEM. 

Because the cells are textured, cross-sectional 

TEM samples must be prepared along certain 

directions and at specific areas. This was 

achieved by using dual beam FIB milling. 

Figure 5(a) is an SEM image of the front side of a 

Si heterojunction cell. Both the front and back 

sides are textured. On the front side, the In2O3 

layer was grown after the growth of the a-Si layer. 

The SEM image indicates that the Indium tin oxide 

(ITO) layer has very good coverage, which is 

necessary in order for Si heterojunction cells to 

achieve high performance. However, the SEM 

image also indicates that the texture is not very 

uniform. 

Fig. 5. (a) SEM image of front In2O3 coverage (b) 

SEM image of back Al coverage of textured Si 

heterojunction cell. (c) HRTEM image of c-Si/a-Si 

interface. 

Figure 5(b) shows an SEM image of the back side. 

On this side, a layer of Al was deposited on the aSi layer. The image shows that the entire backside 

was covered with Al. However, the Al layer is not 

very smooth. Small voids are seen in this layer. 

The mechanism of the formation of these small 

voids is not yet known. It is likely that these small 

voids in the Al contact layer will have harmful 

effects on transport properties. These small voids 

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were not seen in the a-Si layer in a cross-sectional 

TEM investigation. Figure 5(c) shows an HRTEM 

image of the c-Si/a-Si interface in the front side. 

The interface in the backside showed similar 

structure, but with much higher thickness. The a-Si 

layer is about 10 nm thick in the front side and 43 

nm in the back side. On both sides, flat and abrupt 

c-Si/a-Si interfaces were observed. Our results 

indicate that the In2O3 layer, Al-layer, and a-Si 

layer grown at NREL have very high quality. 

These critical data greatly helped the NREL Si 

group to achieve a record efficiency SHJ cell using 

a p-type Si wafer. 

Investigate the electronic effects of grain 

boundaries in CIS: 

Polycrystalline semiconductors generally exhibit 

poor opto-electronic properties compared with 

those of their single-crystal counterparts owing to 

the existence of grain boundaries containing 

dislocation cores. The latter normally create deep 

levels and act as effective recombination centers, 

as the classic grain boundary (GB) model 

concludes. Thus, GB passivation is extremely 

important for polycrystalline solar cells to suppress 

the harmful effects of GBs. 

Surprisingly, however, without intentional GB 

passivation, the efficiency of polycrystalline 

Cu(In,Ga)Se2 (CIGS)-based solar cells is now 

approaching 20%, greatly surpassing that of their 

single-crystal counterparts (~13%). Therefore, 

understanding GB behavior in CIS chalcopyrite 

may lead to future designs of optoelectronic 

devices based on many low-cost polycrystalline 

materials. For a long time, GBs in polycrystalline 

CIS thin films have been explained by the classic 

electronic GB model. However, the classic 

electronic GB model cannot explain the 

remarkable performance of polycrystalline CISbased solar cells. Recent theoretical study has 

proposed that GBs in CIS could be significantly 

Cu-poor, act as hole-barriers, and be charge 

neutral. 

In contrast, our first-principles density-functional 

theory calculations reveal that, surprisingly, GBs in 

CuInSe2 do not follow the classic GB model: GBs 

in polycrystalline CIS do not create any deep 

levels because of the large expansion in the GB 

regions. Thus, our results show for the first time 

that, unlike the classic GB model, GBs in CIS are 

electrically benign. This explains a long-standing 

puzzling fact: polycrystalline CIS solar cells with 

remarkable efficiency can be achieved without 

deliberate GB passivation. This benign electrical 

character of GBs in CIS is confirmed by our SKPM 

measurements on polycrystalline Cu(In,Ga)Se2 

chalcopyrite films. 

Develop luminescence spectrum imaging for 

characterizing industrial silicon wafers and solar 

cells: 

NREL’s spectrum imaging system is based on 

ultra-fast spectrum acquisition (10 ms/pixel) in 

synchronization with the scanning of the electron 

beam in the electron microscope. Spectrum 

imaging is used to map recombination (including 

extended defects such as dislocations and grain 

boundaries), energy levels associated with 

impurities and complexes, stress, composition, 

and other properties relevant to semiconductor 

technology. 

We have expanded the maximum scanning range 

of spectrum imaging to 3 in. × 3 in. (from 100 μm x 

100 μm) by adding external control to the X-Y 

stage of the electron microscope. Both modes—XY SCAN (scanning the X-Y stage to cover large 

areas) and E-B SCAN (scanning the electron 

beam for high-resolution)—are integrated into one 

platform, which enables first mapping the 

transitions identified in the emission spectrum over 

the entire silicon wafer or solar cell and, 

subsequently, running high-resolution 

measurements on preselected locations (such as 

grain boundaries and degraded areas). This 

combination of X-Y SCAN and E-B SCAN in the 

SEM has proven very attractive in addressing 

uniformity concerns and providing defect mapping 

of mc-Si technologies for industrial partners such 

as Advent Solar and CaliSolar. 

When running the X-Y SCAN mode on silicon, 

researchers used the photon intensity at room 

temperature for lifetime mapping. At LN2 

temperatures, D1-D4 and DB transitions 

associated with dislocations and grain boundaries 

are accessible. Figure 6 illustrates the combination 

of these modes for a 2 in. × 2 in. section of an mcSi wafer. 

We drive the X-Y stage to generate a map of the 

photon intensity (which correlates with lifetime at 

room temperature). At the end of the X-Y SCAN 

[see, for example Figure 6(a)], we can select a 

precise location and shift to E-B SCAN to improve 

the resolution [see, for example, Figure 6(b) and (c)]. 

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Fig. 6. (a) Photon intensity X-Y SCAN map of a 2 

in. × 2 in. section of an mc-Si wafer taken at T = 

300 K; (b) selected area high-resolution E-B SCAN 

of the excitonic photon intensity (TO); (c) the 

luminescence associated with deep levels; (d) the 

emission spectrum at locations P1, P2, and P3. 

A high density of dislocations is seen on the grain 

with reduced photon intensity (location P1 on the 

image); a few of the dislocations show a high 

density of deep levels (location P3) at LN2 

temperature. Using spectrum imaging, we can 

extract the emission spectrum from different 

locations (P1, P2, and P3) and obtain information 

about the active electronic states responsible for 

the recombination. 

Investigate the recombination at intragrain 

extended defects in polycrystalline thin-film silicon 

solar cells: 

In polycrystalline thin-film silicon solar cells, larger 

grains do not always translate into higher 

efficiencies. This is largely the result of 

recombination at intragrain extended defects. 

Removal, or at least mitigation, of the harmful 

effects of such defects is therefore critical to this 

thin-film technology. 

We investigated silicon epilayers grown by 

chemical vapor deposition (CVD) at high 

temperature (1100oC) and at moderate 

temperatures (500–600oC) that are compatible 

with glass. Although the temperature dramatically 

affects the microstructure of the epilayers, since a 

higher temperature gives considerably larger 

grains, we found that the recombination is 

dominated by extended defects located in grain 

interiors (not grain boundaries) across the entire 

temperature range. The infrared emission from 

these epilayers, where the band-to-band phononassisted transition seen in Czochralski (CZ) or 

float-zone (FZ) grown silicon is completely absent, 

can be described as band-tail recombination. The 

emission from the S3-type extended defects 

moves further into the infrared when compared 

with their surroundings, a signature of a higher 

density of deep levels contributing to the band tail. 

The luminescence is thermally deactivated by 

similar energy levels (electronic states) 

independently of temperature. Hydrogen 

treatments seem to be ineffective on the extended 

defects. When these findings are complemented 

with TEM observations, it becomes evident that 

the best approach to achieving better efficiencies 

in CVD silicon involves better control of the 

epilayer back interface, where these extended 

defects originate. 

Investigate the effect of in situ stress during 

MOVPE growth of high-efficiency latticemismatched III-V multijunction solar cells: 

NREL’s high efficiency devices team recently 

demonstrated record-breaking efficiencies in a 

monolithic III-V triple-junction solar cell. This solar 

cell utilizes a lattice-mismatched 1.0 eV 

In0.27Ga0.73As bottom junction and is grown in an 

inverted geometry with GaInP and GaAs top 

junctions lattice-matched to the GaAs substrate. 

Further improvement of cell efficiency requires a 

better understanding of the factors that control the 

threading defect density in these latticemismatched multijunction solar cells. 

In collaboration with NREL’s high-efficiency 

devices team, we have been involved in a study of 

the effect of in situ stress during metal organic 

vapor phase epitaxy (MOVPE) growth on the 

performance and microstructure of monolithic III-V 

triple-junction solar cells that were grown inverted 

with a metamorphic 1.0 eV bottom In0.27Ga0.73As 

junction. The in situ stress during the growth of 

this lattice-mismatched junction was varied by 

controlling the design of a step-graded GaxIn1-xP 

buffer layer in which most, but not all, of the 1.9% 

misfit strain was relieved. Excellent performance 

was obtained for inverted In0.27Ga0.73As solar cells 

grown with slight compressive or zero stress, but a 

degradation in performance was observed for cells 

grown under tensile stress. These results were 

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found to correlate with the threading dislocation 

density in the samples, as revealed by SEM 

cathodoluminescence (CL) and cross-sectional 

TEM. For samples grown under zero or moderate 

compressive stress, threading dislocation 

densities in the low 106

 cm-2 were measured by 

CL, and no threading dislocations were seen in 

cross-sectional TEM images [Figure 7(a)]. The 

cells had a VOC of ~ 0.54 eV. For a sample grown 

under tensile stress (0.17 GPa), which had a VOC 

of 0.32 eV, CL revealed threading dislocation 

densities in the high 106

 cm-2 range, and threading 

and misfit dislocations were present in crosssectional TEM images of such devices [Figure 

7(b)]. These results indicate that achieving a lower 

threading dislocation density is crucial in improving 

lattice-mismatched multijunction solar cells’ 

performance, and that in situ tensile stress during 

growth should be avoided. The knowledge gained 

from this work should enable researchers to obtain 

improved, record-efficiency lattice-mismatched 

multi-junction solar cells in the near future. 

Fig. 7. TEM images (220 dark-field) of two inverted 

InGaAs solar cells grown with different film stress in 

the active layer: (a) 0.12 GPa compressive and (b) 

0.17 GPa tensile. Threading dislocations (TD) and 

the ends of misfit dislocations (MD) are observed in 

the thick InGaAs junction layer of sample (b). 

3.2 Cell and Module Performance Task 

Provide routine and specialized measurement and 

characterization support for SETP PV research 

and industry teams: 

During FY 2007, researchers made 5020 cell 

current-voltage (I-V), quantum efficiency (QE), and 

linearity measurements on 1758 samples, and 

1567 I-V measurements on 408 modules. In direct 

support of SAI TPP and PV Incubator 

subcontracts, researchers made 1339 cell 

measurements on 414 samples and 394 module 

measurements on 128 samples. 

Reduce uncertainty in high-efficiency concentrator 

measurements: 

Upon release of capital equipment funds, detailed 

simulator specifications were submitted to 

procurement in order to initiate the request for 

proposals. The proposals have been received and 

reviewed by a technical team, and a statement of 

work has been completed with the selected 

vendor. We are currently awaiting an estimated 

delivery date. The specifications call for a 

spectrally adjustable simulator in at least 10 bands 

to accommodate all the conceivable highefficiency concentrator cell designs we might 

encounter over the next 10 years. The system is 

designed to cycle through temperatures, 

irradiance, and spectra to produce an energy 

rating for any given typical meteorological year. 

NREL will have complete access to the software 

developed for this system. This is critical for 

calibrations and compliance with the team’s ISO 

quality system. Software will have to be written to 

take these data automatically and process the 

data. This tool will allow the spectral sensitivity of 

multijunction concentrator cells to be addressed in 

terms of energy production and not just their 

performance with respect to fixed reference 

conditions. The irradiance range will be 

approximately 1 to 2000 suns with ±1% spatial 

nonuniformity over an area of 10 cm by 10 cm. 

Expand capabilities to evaluate large-area 

modules: 

The current module solar simulator using pulsed 

light is limited to modules that are smaller than 61 

cm by 122 cm. A new pulsed class AAA Spire 

4600SLP solar simulator has been ordered with an 

expected delivery date of August 15, 2008. The 

advantage of a pulsed class AAA solar simulator is 

that the temperature is accurately known, the 

spectrum is well defined throughout the life of the 

lamp, and the spatial nonuniformity is ±2% or 

better. We anticipate that, once this simulator is 

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brought to operational status and the software is 

modified to be compliant with the team’s ISO 

quality system, the capabilities will be expanded to 

automatically measure I-V characteristics as a 

function of total irradiance and temperature. This 

will allow the energy to be predicted with respect 

to a typical meteorological year. The new 

simulator is capable of measuring modules as 

large as 137 cm by 200 cm. 

Reduce measurement time and uncertainty of 

evaluating multijunction devices at 1-sun: 

Activity on this task has been delayed because of 

inadequate labor resources. This labor shortage 

has been corrected by two new hires that started 

in January and Feburary. Work on the task is now 

proceeding in parallel with training the new hires. 

The simulator will have features similar to those of 

the multisource cocntrator simulator, except that it 

will operate at 1-sun and with continuous light. 

This tool will allow the spectral sensitivity of 

multijunction cells to be addressed in terms of 

energy production as a function of spectral 

irradiance, total irradiance, and temperature and 

not just their performance with respect to fixed 

reference conditions. 

Maintain ISO 17025 accreditation for primary and 

secondary cell and module calibrations; complete 

periodic audits, maintenance of quality systems, 

calibrations, software and documentation to meet 

A2LA requirements: 

Quality calibration plays a critical role in the 

product-manufacturing process. ISO accreditation 

provides our customers with confidence that the 

performance reported for these products is 

verifiable and internationally accepted. Many of 

our PV industry partners currently have ISO 9001 

quality programs in place. These companies rely 

on NREL for calibrations of the reference cells and 

modules they use to measure their products. 

Certified module-qualification facilities such as the 

Arizona State PV Testing Laboratory and the 

Florida Solar Energy Center require their 

reference cell calibrations to be traceable to a 

certified laboratory. 

All PV calibrations performed by the group are 

traceable to primary reference cells calibrated by 

NREL. NREL is one of four calibration 

laboratories in the world certified to perform 

Photovoltaic Scale Primary reference cell 

calibrations. For this reason, it was critically 

important that NREL attain an ISO accreditation 

for the reference cells we calibrate for the PV 

community. The ISO 17025 accreditation provides 

NREL with international credibility and recognition 

(Figure 8). 

Fig. 8. NREL A2LA accreditation certificate # 

2236.01, valid to November 30th, 2008. 

This process took two years to complete and 

involved establishing a very structured quality 

system, detailed work procedures, a detailed 

document control methodology, formalized recordkeeping process, rigorous management review 

process, corrective action plan process, and an 

instrument calibration validation process. 

Implementing and maintaining an ISO 17025 

program is a significant and critically important 

task. Test beds within the PV performance team 

that produce numerical results for customers that 

are not within the scope of A2LA certificate 

2236.01 are required to be in calibration as if part 

of the scope and the software is subjected to the 

ISO 17025 software review process. 

Concentrator module testing: 

Eleven concentrator prototype modules from six 

companies, including Spectrolab and Solfocus, 

were evaluated, generating more than 48,580 I-V 

curves with accompanying irradiance and other 

meteorological data. Direct-beam spectra also 

accompany the data set for 15 sunny days. Data 

were analyzed using multiple linear regression to 

project test conditions (20°C air temperature, 850 

or 1000 W/m2

 direct irradiance, and 4 m/s wind 

speed). Evaluation of the data set to develop and 

compare alternative rating methods, develop 

translation equations, and predict the energy with 

respect to SAI reference conditions were not 

performed because this enhancement in the scope 

of the activities, with commensurate funding, was 

not accepted in the FY 2007 Annual Operating 

Plan. 

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American Society for Testing and Materials 

(ASTM) and International Electrotechnical 

Commission (IEC) standards: 

We attended committee meetings and participated 

in standards development. We also shepherded 

standards for linearity determinations, rating 

concentrator modules and systems, and spectral 

responsivity measurements. 

Technology transfer: 

There were approximately 50 instances, lasting 

from 1 to 15 hours, of the transfer of I-V and QE 

measurement technology to SAI partners, U.S. 

industry, and others. Hundreds of other visits, 

phone conversations, and e-mail interactions 

relating to specific questions about I-V and QE 

measurement technology took less than 1 hour. 

3.3 Electro-Optical Characterization Task 

Study the kinetics of Si wafer microcrack 

propagation as a function of processing: 

Wafer breakage is a critical issue in current lowcost solar cell production, because typically about 

10% of wafers break during cell fabrication. It is 

now recognized that wafer breakage arises 

primarily because of the presence of microcracks, 

either on the edges or the surfaces of the wafer. In 

our ongoing efforts to alleviate this problem, we 

have performed numerical and analytical studies 

of the fracture properties of silicon wafers. 

We developed a general fracture-mechanics 

model that can successfully predict the strength of 

cast silicon wafers used by the PV industry. The 

model combines Monte Carlo simulations with 

finite-element fracture computations. The 

computation procedure developed starts from 

virtual generation of a set of wafers n. Each wafer 

in the set contains a prescribed number of surface 

cracks, which are randomly distributed and 

oriented. Next, the maximum load for each wafer 

is calculated using the numerical fracturemechanics method combined with the weakestlink principle. Finally, we perform a statistical 

analysis of the results for all n wafers to obtain the 

strength distribution, and we estimate the 

corresponding distribution parameters. 

The technique is very general and allows the 

modeling of wafers of various sizes and shapes 

that are subjected to any type of loading. This 

understanding can now be applied to real-world 

crack distributions induced by different process 

steps and the strength of wafers relative to the 

various stress distributions they are subject to 

during solar cell processing. Ultimately, this will 

inform PV manufacturers about how to modify 

their manufacturing processes to minimize 

breakage. 

Organize the 17th Workshop on Crystalline Silicon 

Solar Cell Materials and Processes: 

The 17th Workshop on Crystalline Silicon Solar 

Cells and Modules: Materials and Processes was 

held in Vail, Colorado, on August 5–8, 2007. This 

meeting spanned 3-1/2 days and attracted a 

record number of attendees (179) from 16 

countries, with representatives from 62 

international PV and semiconductor companies 

and 19 universities. The greatest number of 

participants were from the United States (114), 

Germany (21), Japan (9), Canada (8), Norway (7), 

and Taiwan (6). The workshop’s central theme, 

“Expanding Technology for a Future Powered by 

Silicon Photovoltaics,” reflected the enormous 

growth in Si-PV and huge number of new 

companies. Sessions were organized around 

specific topics related to the theme and included 

several invited presentations by selected experts 

followed by lengthy discussions on the topic 

moderated by the session chair or panel leader. 

This intense meeting was designed to promote 

extensive interactions and exchanges of ideas 

among participants. Evening poster sessions 

permitted additional research presentations and 

interactions. As in prior workshops, there was an 

informal Rump Session on Sunday evening. The 

theme of that session was “Achieving Low-Cost 

Electricity (Grid-Parity) with Si PV.” Oral, poster, 

and discussion sessions addressed recent 

advances in crystal growth technologies, 

impurities and defects in semiconductors, 

feedstock issues, solar cell processing, thin-film Si 

and heterojunction devices, solar cell 

metallization, and cell and module measurement 

issues. 

Develop minority carrier lifetime measurement 

techniques: 

Quality control in PV manufacturing is hindered by 

the lack of in-line diagnostics. Because 

manufacturers are unable to test cells until the end 

of the production line, problems in the production 

process can go undiscovered for a day or longer. 

This can result in the production of large volumes 

of defective cells. Measurements of minority 

carrier lifetime (MCL) and related properties offer 

the promise of rapid noncontact diagnostics of 

materials and processes that can be deployed on 

the production line. Scanning or mapping 

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techniques measure a sample over thousands of 

points, while imaging techniques measure the 

entire sample at once. Scanning techniques apply 

single-point measurement techniques that are well 

understood, while imaging techniques are 

relatively new and untested. The new imaging 

techniques hold great promise for in-line 

diagnostics because of their rapidity; however, the 

correlation between their images and solar cell 

efficiency is poorly understood. 

Our group at NREL possesses a unique 

combination of expertise and facilities to 

investigate and develop advanced techniques for 

measuring MCL. Our goal in this project is to 

develop and compare the latest techniques to 

determine the optimum methods and conditions 

for on-line MCL diagnostics. In FY 2007, we made 

considerable progress toward developing new 

technique capabilities in spite of numerous delays. 

A commercial microwave reflection system was 

ordered, but we have not yet received it. In the 

meantime, we built a homemade version of a 

microwave reflection scanner that will prove useful 

in the design and construction of a custom system 

to be installed in a future PDIL vacuum system. 

Mapping results for a wafer intentionally 

contaminated with iron are shown in Figure 9. 

Fig. 9. Microwave reflection lifetime map of a single 

100-mm crystalline silicon wafer with features caused 

by iron contamination in the center and vertical lines 

caused by contact with grid supports during furnace 

annealing. 

Fig. 10. (a) PL image of the c-Si wafer shown in 

Fig. 9; (b) PL image of multicrystalline Si wafer. 

Photoluminescence imaging (PLI) is a relatively 

new technique in which the photoluminescence 

(PL) intensity is thought to be proportional to the 

carrier lifetime in each area. This may provide a 

high-speed method for characterizing the lifetime 

distribution in a wafer. Figure 10(a) shows PLI 

data from same wafer scanned in Figure 9. 

Scanning takes a few seconds per point over 

thousands of points, so the map of Figure 9 took 

nearly an hour to complete. In contrast, the PL 

image took only a few seconds of exposure time. 

PLI will also be applicable to multicrystalline 

samples, as shown in Figure 10(b). 

Carrier density imaging (CDI) is another relatively 

new technique under development. CDI uses an 

infrared camera to monitor either the absorption or 

emission of infrared radiation by excess carriers. 

CDI may have an advantage over PLI in that 

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recombination of excess carriers can be any 

mechanism, and a strong PL signal is not 

necessary. This may make CDI more appropriate 

for unpassivated surfaces. CDI, however, requires 

extreme sensitivity, and only lock-in techniques 

will provide such resolution. We are currently in 

the early stages of developing this technique. 

Figure 11 shows a wafer with multiple 

contamination spots clearly resolved by CDI. 

Fig. 11. Carrier density image of a c-Si wafer 

with multiple contamination spots as measured 

using an infrared camera with lock-in detection. 

Develop advanced multidimensional computer 

models for multicrystalline-Si devices: 

Multicrystalline (mc)-Si wafers made from cast 

ingots are significantly less expensive than singlecrystal wafers made from single-crystal boules. 

Unfortunately, solar cells made from mc-Si wafers 

are also significantly less efficient than their singlecrystal counterparts. Although there is a 

consensus that the lower efficiency of mc-Si solar 

cells is the result of the presence of grain 

boundaries and nonuniformities from grain to 

grain, there is no clear understanding of how these 

properties impact the function of solar cells or 

measurements of their properties. Numerical 

modeling of mc-Si wafers and solar cells provides 

a unique capability to do “numerical experiments” 

in which it is a simple matter to change the grain 

size, local lifetime, or recombination velocity at 

grain boundaries and observe the effect on cell 

efficiency and MCL that would be observed 

experimentally. 

To gain a better understanding of both mc-Si solar 

cells and measurements of their properties, we 

developed advanced, two-dimensional computer 

models to analyze the physics introduced by GBs 

and nonuniformities. Figure 12 illustrates how the 

impact of lifetime nonuniformity depends on the 

grain size. In Figure 12(a), each of the grains is 

3.33 mm wide; in Figure 12(b), each grain is 3.33 

μm wide. The carrier lifetime varies from 100 to 1 

to 10 μs across the three grains. In the large-grain 

material, each grain functions as an independent 

diode; in the small-grain material, all three grains 

function with a single effective diffusion length. We 

find that, for grains greater than 1 mm across, GB 

recombination does not significantly affect device 

performance, but it can be very deleterious to 

smaller grain material. For macroscopic lifetime 

fluctuations, the regions with the shortest lifetimes 

generally dominate performance in a manner that 

can be estimated reasonably well using analytical 

formulas. 

Models were also developed to simulate quasisteady-state photoconductivity (QSSPC), 

photoconductive decay (PCD), and infrared carrier 

density (IR-CD) lifetime mapping measurements 

on mc-Si solar cells with grain boundaries and 

lifetime fluctuations on different scales—both 

before and after the formation of the junction. If 

there is no junction, QSSPC and IR-CD measure 

the average lifetime for fluctuations on a scale 

larger than the diffusion length, whereas PCD 

measurements may measure the harmonic mean, 

the spatial average, or something else, depending 

on how the decay curve is analyzed. 

Generally, the measured lifetime does not 

correspond to the aggregate lifetime, which 

represents device performance. So, highresolution mapping and specialized analysis are 

required to accurately correlate lifetime maps to 

device performance. Once a junction is added, 

charge separation significantly distorts lifetime 

measurements regardless of the technique used. 

Implementing high injection might mitigate charge 

separation effects, but it might also lead to 

undesired high-injection effects. These findings 

contradict the ideas of researchers who promote 

using QSSPC and CDI measurements in the 

presence of a junction to correlate lifetime maps to 

device performance. Much of this work has been 

summarized in a manuscript submitted to Solar 

Energy Materials and Solar Cells. 

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Fig. 12. The arrows indicate the direction of 

electron flow, and the contour colors indicate the 

magnitude of the electron current density in the x 

direction (Jex) for a mc-Si solar cell under AM1.5 

irradiation and no bias. For the three equally 

spaced regions running from left to right, τ is 100, 

1, and 10 μs, respectively. In (a), each region is 

3.33 mm across; in (b), each region is 3.33 μm 

across and the contour color scale is different. 

Develop an in situ spectroscopic ellipsometry 

capability for the TCO sputtering tool in the PDIL: 

Virtually all types of solar cell devices utilize a 

transparent top contact to allow light to penetrate 

into the cell while enabling the collection of electric 

current from the front surface. This requires high 

transparency together with high electrical 

conductivity, two frequently incompatible 

requirements. 

Researchers at NREL are constantly working to 

develop new types of transparent conducting 

oxides (TCO) that can satisfy both of those 

requirements. Zinc oxide (ZnO) is one the most 

promising of the new TCOs, and NREL 

researchers are actively working to advance our 

capabilities to simultaneously optimize both the 

transparency and conductivity of ZnO. One of the 

most effective ways to accelerate progress in 

materials development is through the application 

of in situ diagnostic tools. 

By measuring the film thickness and optical 

constants in real time during film deposition, in situ 

spectroscopic ellipsometry, also known as realtime spectroscopic ellipsometry (RTSE), provides 

valuable insights into the material properties and 

growth dynamics of the thin-film materials used in 

photovoltaics. Many of the deposition chambers 

integrated into the cluster tools being designed 

and installed in the PDIL will incorporate optical 

ports for RTSE. We hope that this capability will 

greatly contribute to the science and engineering 

of materials for PV. The TCO sputtering tool is the 

first of these tools to come online. 

In FY 2007, we used RTSE to study the effect of 

substrate temperature on the growth dynamics 

and material properties of undoped sputterdeposited ZnO. We found that there is a layer 40– 

90 nm thick on the surface of the growing ZnO film 

that has optical properties distinct from those in 

the bulk of the film. Significant near-IR absorption 

indicates that there may be a high density of 

defects or free carriers in this material. During film 

deposition, this film stays constant in thickness 

while the underlying bulk ZnO increases in 

thickness, indicating a conversion of the growth 

zone material into bulk material at the bulk-growth 

zone interface. This may be an annealing effect 

caused by the elevated substrate temperature. We 

have also determined a correlation with poor 

conductivity in ZnO films less than 100 nm thick. 

Through ongoing studies we expect to gain a 

better understanding of the growth mechanisms of 

ZnO and obtain better control of film properties. 

3.4 Surface Analysis Task 

Provide surface analysis support: 

The Surface Analysis team supported a variety of 

U.S. PV manufacturers during FY 2007. The most 

intensive efforts were with Advent Solar (XPS 

studies of SixNy:H passivation layers), Miasole 

(extensive analytical support to understand 

compositional and contaminant issues related to 

process development for CIGS), SoloPower 

(compositional profiling in CIGS materials), and 

CaliSolar (dopant profiling for silicon device 

structures). In FY 2007, we were able to honor all 

requests for analysis and support. 

Photovoltaic R&D

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Measurements and Characterization

50
Develop a new moisture barrier package and 

conduct barrier coated aluminum mirror screening 

studies: 

Barrier layers for inhibiting the ingress of moisture 

in flexible packages must possess two properties 

to be effective for this application. Obviously, the 

barrier must inhibit the passage of water through 

the barrier. It is not so obvious, however, that the 

barrier must also adhere well to the surface it is 

deposited on and laminated to, in order to function 

properly. Previous collaborative work at NREL 

between the Surface Analysis team and the 

Reliability Packaging team has shown that 

PECVD-grown moisture barriers on polyethylene 

terephthalate (PET) can have excellent initial 

adhesion to PET and ethylene vinyl acetate (EVA) 

and exhibit moderate barrier efficacy; however, 

adhesion of the barrier to the PET fails after even 

a very brief exposure to damp heat. Weak 

interfacial bonds between the PECVD layer and 

the PET surface are suspected to contribute to the 

adhesion failure. 

During FY 2007, we investigated a variety of new 

interfacial layer (IFL) coatings deposited on PET. 

We evaluated IFL/PET for efficacy and adhesion 

before and after damp heat exposure. Initial 

measurements showed that the barrier efficacy of 

IFL alone ranged from inferior to very good, when 

compared with PECVD barriers alone. We found 

that IFL-alone adhesion was similarly variable, 

depending on composition. It was particularly 

interesting that even the IFL composition 

displaying the highest resistance to damp heatinduced adhesion loss was still inferior in 

performance to a PECVD barrier alone. However, 

subsequent depositions of PECVD barrier 

overcoats on IFL-coated PET resulted in a 

package that exhibited some of the lowest WVTR 

(water vapor transmission rate) values we have 

seen to date, as well as 100% retention of peel 

strength (adhesion) even after 300+ hours of 

damp heat testing. Inserting the interfacial 

adhesion layer represents a new barrier 

construction that resulted in an NREL Record of 

Invention filed in December 2007. 

Other studies performed during FY 2007 focused 

on determining the best composition for PECVD 

barrier overcoats. A variety of compositions 

ranging from SiOx → SiOxNy → Si3N4 were 

deposited on aluminum-coated glass containing 

scribe lines. Because thin films of aluminum on 

glass are very susceptible to chemical attack 

under damp-heat conditions and turn clear where 

attack has taken place, they offer a quick and 

effective screening method for barrier efficacy. 

Aluminum mirrors were deposited in 1 in. x 1 in. 

squares on glass to perform a combinatorial 

composition study. By using a new photocurrent 

measurement device to measure light 

transmission after varying amounts of damp-heat 

exposure, we found that films with high nitrogen 

content (such as stoichiometric Si3N4) exhibited 

the highest barrier efficacy even after 2000+ hours 

of damp-heat exposure. In addition, the films in 

general are apparently highly conformal around 

scribe lines, as evident in no observable 

deterioration in the areas around the scribe lines. 

We intend to use a similar approach with ZNOcoated glass to evaluate barriers suitable for direct 

overcoats of PV absorbers. 

Investigate the materials chemistry of CIGS on 

flexible substrates, leading to an improved 

understanding of long-term reliability: 

This work was formulated to be a continuation of 

studies begun during FY 2006. In the earlier work, 

a sodium fluoride (NaF)-induced defect was 

identified that appeared to show a correlation with 

the damp-heat-induced degradation of 

unencapsulated CIGS devices on flexible 

substrates. The intent of the current work was to 

study this defect with various PV manufacturers; 

however, we encountered difficulties because of 

the proprietary nature of each manufacturer’s 

process and our inability to arrive at test structures 

and processing conditions that could be shared in 

the general literature. 

The results of this work that can be shared are as 

follows. Sodium fluoride is often used as a source 

of sodium in CIGS grown on non-soda-lime-glass 

substrates or on diffusion-barrier coated glass. 

This is necessary to provide an adequate supply 

of sodium to produce high-efficiency CIGS films. 

Several previous studies reported in the literature 

for CIGS films grown on glass had determined that 

no fluorine remained in the CIGS from the NaF 

(also confirmed in previous NREL studies); 

however, our current study finds that, on various 

nonglass substrates, this result is not always the 

case. Certain processing conditions do not result 

in complete volatilization of the fluorine from the 

growing film, leaving high levels of this halide 

impurity in the film. The presence of fluorine 

indicates that unbound sodium may not be 

available to aid in CIGS film growth. Although we 

had limited samples to investigate these 

processing-related compositional differences, it 

appears that, to volatilize all the fluorine, it is 

critical that the substrate reach a high enough 

51

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Measurements and Characterization
temperature. This critical temperature could be 

difficult to attain on a flexible substrate, where too 

high a temperature may also result in the diffusion 

of deleterious elements from the substrate or even 

in the melting of the substrate. Unfortunately, the 

details of this study cannot be disclosed because 

of the proprietary nature of the work done with our 

industry partners. 

Improve the understanding of CdTe back-contact 

reaction kinetics: 

A study describing the CuxTe/CdTe surfaceprecipitation phenomenon and the accompanying 

change to the CdTe surface electronic structure 

has been completed and published in the Journal 

of Applied Physics. The results were presented at 

the 2007 Spring Materials Research Society 

(MRS) Meeting in the Thin-Film Compound 

Semiconductor Photovoltaics Symposium. These 

studies shed new light on the role of Cu in CdTe 

PV back contacts. In particular, the segregated 

nanoscale CuxTe creates a metallic surface state 

that effectively lowers the ionization potential of 

the surface. Because secondary back-contact 

materials can readily contact the metallic CuxTe 

layer, this helps to explain the role of Cu in ohmiccontact formation in CdTe PV devices. 

A second experimental paper published in Thin 

Solid Films describes the formation of CuxTe via 

the exposure of elemental Cu to Te vapor, and the 

decomposition kinetics via in-vacuum thermal 

decomposition of these films via the reaction 

CuxTe(s) Æ xCu(s) + Te(v). This study has 

relevance both to back-contact processing and 

long-term stability issues and was presented at the 

2006 American Vacuum Society (AVS) Fall 

Meeting. 

The lack of a suitable theory in the literature to 

describe the observed CuxTe/CdTe surfaceprecipitation phenomenon motivated us in 2007 to 

develop an impurity migration model for systems 

with material interfaces. The model is very general 

and is capable of describing diffusion, segregation, 

and migration phenomena in a wide variety of 

material systems relevant to PV research. One 

exciting application for the model is Cu-migration 

in CdTe/CdS solar cells under both deviceprocessing and field-deployed conditions. 

Preliminary modeling of this system explains the 

frequently observed migration of Cu from the back 

contact and segregation in the CdS layer. Two 

manuscripts have been prepared that describe the 

development and implementation of the 

diffusion/segregation model. One paper addresses 

impurity migration phenomena in systems with 

material interfaces. The other paper applies the 

model to surface-segregation phenomena like the 

CuxTe surface precipitation observed on the 

surfaces of Cu-doped CdTe. 

Develop a large-platen Auger electron 

spectroscopy tool: 

The order for the large-platen Auger electron 

spectroscopy (AES) PDIL tool was placed in the 

final quarter of FY 2006, and the tool was to be 

delivered and installed in 2007. Unfortunately, the 

tool builder encountered several problems with 

various subcomponents for the Auger analysis 

system that repeatedly delayed the completion 

and testing of the tool. Initially there were 

difficulties with computer control of the electron 

spectrometer, the detectors, and the ion gun. The 

problems were serious enough to require 

modification of the Auger components and 

electronics at the OEM vendor. The delay in 

reconfiguring the Auger parts left the tool vendor 

unable to test the system until late in FY 2007. As 

testing progressed, NREL Surface Analysis staff 

members raised concerns about the electron 

spectrometer’s resolution and transmission, and 

later about the stability of the ion gun. By February 

2008, the spectrometer had exceeded NREL’s 

performance specification for the tool. The ion 

gun, however, is still performing at unacceptable 

levels. The Surface Analysis team is working with 

the vendor to resolve these issues. We expect the 

problems to be resolved and believe the tool will 

be ready for acceptance testing in April 2008. 

Develop the design and specification of a smallspot XPS tool: 

The small-spot XPS tool based on the process 

integration standard for the PDIL is currently under 

construction, and delivery is expected to NREL 

during the fourth quarter of FY 2008. The tool was 

procured through a competitive bidding process, 

and four vendors responded to the request for 

quotations. The winning bids were from Kratos 

Analytical for the XPS tool and from Transfer 

Engineering (TE) for an integrated rotationflipping-transfer station. Both vendors provided 

outstanding technical excellence and value in their 

bids. The TE flipping station will allow the sample 

platen to be loaded from other tools in the facedown position, which is common in the PDIL 

deposition tools, and then flipped to face-up for 

XPS analysis. The Kratos AXIS NOVA is a highly 

automated, state-of-the-art imaging XPS with a 

capability for selected area spectroscopy with 

lateral resolution of ≤10 μm. The tool will be able 

Photovoltaic R&D

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Measurements and Characterization

52
to access all areas of the platen via a single 180° 

rotation of the sample built into the flipping station. 

The fact that the XPS tool is based on a standard 

Kratos product will facilitate completion and 

installation. Kratos and TE have been strong 

partners in this endeavor. 

Develop a liquid-phase quartz-crystal 

microbalance for automated chemical-bath 

deposition end-point detection: 

In FY 2007, we completed the construction and 

testing of the liquid-phase quartz crystal 

microbalance (LQCM) automated chemical 

reaction system. This system uses inexpensive 

off-the-shelf components and was designed to 

help the Surface Analysis Team investigate 

processes that occur at the solid-liquid interface. A 

number of these processes are used in the PV 

industry because of their favorable combination of 

effectiveness and lower cost; examples include 

the chemical bath deposition of CdS buffer layers 

in Cu(In,Ga)Se2 and CuInS2 devices, a process 

that is used in virtually every commercially 

available CIS-based module. Others are aqueous 

etching of silicon-based cells for AR-texturizing, 

cleaning, and defect removal, and solution-based 

methods for the growth and modification of nextgeneration quantum dot (QD)-based solar cells. 

The system is installed in the glove box of our 

cluster tool, allowing materials to be studied in 

liquid environments and the direct transfer of the 

reacted surface into the ultra-high-vacuum (UHV) 

environment, in order to study the surface 

chemistry and physics. 

Initial results from the apparatus are extremely 

promising and will be described in detail in a 

presentation at the 33rd Institute of Electrical and 

Electronic Engineers (IEEE) PV Specialists 

Conference. We have demonstrated the 

successful operation of all hardware and software 

components, reagent dispensing systems, pumps, 

membrane contactors, a six-way valve for the 

sequential addition of reagents, monitoring 

equipment such as a pH meter, and the QCM 

itself. We have shown that the special QCM 

crystals, originally meant for operation in liquids 

only, can be heated to >200oC in a sputter 

deposition system and coated with materials of 

interest, and that crystals coated with a solid 

material of interest still perform as expected in 

liquids. We have used the system to accurately 

measure the dissolution rate of ZnO, an important 

transparent conductor, in dilute chloride solutions 

down to 0.008 Å/s. We have also shown how 

attaching a simple organic molecule to the oxide 

surface can be used to dramatically slow this 

corrosion. This result has obvious implications for 

studying the degradation of PV materials under 

various aqueous conditions, such as those that 

might be experienced in humid environments 

inside an actual module. 

Multiple exciton generation collaborative R&D: 

Our previous efforts to integrate atmospheric 

pressure tools with UHV surface analysis tools 

generated new collaborations in FY 2007 with the 

Nozik group in studies of materials for multipleexciton generation in PV devices. Our teams were 

able to grow quantum dots with a solution-based 

process and study how post-growth processing 

enables thin films of these QDs to be transformed 

from electrical insulators to conducting, active 

elements in electronic devices. Such electronic 

coupling between QDs is a prerequisite for the 

efficient operation of a wide variety of strategies 

that aim to make use of the unique properties of 

QDs in a new generation of PV devices. 

The issue here is that QDs typically are grown with 

long, straight-chain alkanes that have large 

HOMO-LUMO gaps (between the highest 

occupied molecular orbitals and the lowest 

unoccupied molecular orbitals) of ~8 eV. Because 

each QD is encapsulated in a thick insulating shell 

of organic molecules, thin films of as-grown QDs 

are also insulators. Our plan, which was 

successful, was to try to exchange the long-chain 

organic capping groups (oleic acid) with much 

shorter molecules (ethanedithiol) in the hope that 

the exchange would be possible and that this 

would allow greater inter-dot electronic coupling. A 

key problem that was overcome with the Surface 

Analysis Team cluster tool stems from the fact that 

removing the long-chain alkane capping groups 

from QDs makes them extremely reactive towards 

one or more constituents of air. We were able to 

use the glove box portion of the cluster tool to 

perform contamination-free transfers of films 

between laboratories and thus do some of the very 

first surface analytical studies on these types of 

films. This work has resulted in two publications to 

date. A third publication is being prepared in which 

we elucidate the mechanisms by which QD-based 

devices fail upon exposure to air. 

4. Planned FY 2008 Activities 

A list of selected FY 2008 planned activities is 

given below. A more complete list of planned 

activities and milestones can be found in the 

Measurements and Characterization FY 2008 

53

Photovoltaic R&D

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Measurements and Characterization
 

 

 

Annual Operating Plan. In FY 2008, we will Patents: 

complete the following milestones: • B. Sopori, Wafer Characteristics via
 

•	 Develop an integrated plan to provide priority 

support to SAI TPP awardees that meets their 

R&D needs within the context of available 

resources. 

•	 Provide measurement support in the areas of 

analytical microscopy, cell and module 

performance, electro-optical characterization, 

and surface analysis to PV research partners 

in industry, academia, and NREL. 

•	 Maintain ISO accreditation for primary and 

secondary cell and module calibrations. 

•	 Complete the construction and fit-up of the 

OTF expansion project. 

•	 Install enhanced module measurement 

capabilities that will improve measurement 

uncertainty, as necessary to support the SAI. 

•	 Bring new solar simulators on line and make 

them compatible with our ISO quality systems. 

•	 Organize the 18th Workshop on Crystalline 

Silicon Solar Cells & Modules. This year’s 

theme is “Achieving Low-Cost Electricity (GridParity) with Si PV.” 

•	 Design, procure, and install the Measurement 

and Characterization integrated PDIL tool set. 

Integrated tools include the cluster tool robot; 

resonantly coupled photoconductive decay 

lifetime tool; PL imaging tool; spectroscopic 

ellipsometer tool; Auger electron spectroscopy 

tool; sputter/plasma etch tool; and the PECVD 

tool. 

•	 Design, procure, and install the Measurement 

and Characterization stand-alone PDIL tool 

set. Stand-alone tools include the X-ray 

photoelectron spectroscopy tool; scanning 

electron microscopy tool; atomic force 

microscopy tool; wet chemistry workstation 

tool; reflectometer; optical processing furnace; 

and lifetime mapping tool. 

5. FY 2007 Special Recognitions, Awards, and 

Patents 

Awards: 

•	 Keith Emery received the 2007 Paul 

Rappaport Award. 

•	 Keith Emery was also one of the recipients of 

a 2007 R&D 100 award to Spectrolab and 

NREL. 

•	 Manuel Romero won an NREL outstanding 

performance staff award. 

•	 Peter Sheldon was elected to the position of 

Director of the AVS Science and Technology 

Society. 

Reflectometry and Wafer Processing 

Apparatus and Method, U.S. Patent No. 

7,238,912, July 3, 2007. 

•	 D. Levi, Optical Method for Determining the 

Doping Depth Profile in Silicon, U.S. Patent 

No. 7,179,665, Feb. 20, 2007. 

•	 B. Sopori and P. Sheldon, Technique for 

Screening and Isolating, “Problem Wafers” 

with Fatal Cracks, Filed 2007. 

•	 A. G. Norman and J. M. Olson, 

Nanostructures Produced by PhaseSeparation during Growth of (III-V)1-x(IV2)x 

Alloys, U.S. Patent No. 7,229,498 B2, June 

12, 2007. 

6. Major FY 2007 Publications 

K. Ahn, Y. Yan, S-H. Lee, T. Deutsch, J. Turner, 

C.E. Tracey, C.L. Perkins, and M. Al-Jassim, 

"Photoelectrochemical Properties of NIncorporated ZnO Films Deposited by Reactive RF 

Magnetron Sputtering,” J. Electrochem. Soc., 

154(9), B956 (2007). 

K. Ahn, T. Deutsch, Y. Yan, C-S. Jiang, C.L. 

Perkins, J. Turner, M. Al-Jassim, and K. Ahn et al., 

"Synthesis of Band-Gap-Reduced P-Type ZnO 

Films by Cu Incorporation,” J. Appl. Phys., 102(2), 

023517 (2007). 

R.K. Ahrenkiel, S.W. Johnston, and P. Dippo, 

“Relationship of Intrinsic Luminescence to 

Recombination Lifetime in Single-Crystal Silicon 

Wafers.” Sopori, B.L., ed., in 17th Workshop on 

Crystalline Silicon Solar Cells and Modules: 

Materials and Processes; Workshop Proceedings, 

5-8 August 2007, Vail, Colorado, NREL Report no. 

BK-520-42056) (2007). Golden, CO: National 

Renewable Energy Laboratory (2007). 

R.K. Ahrenkiel, S.W. Johnston, and W.K. Metzger, 

“Comparison of Techniques for Measuring 

Recombination Lifetime in Photovoltaic Materials: 

Trapping Effects,” in Solar Energy Conversion, y 

Matt Beard, ed., Mater. Res. Soc. Symp. Proc. 

974E, Warrendale, PA, 0974-CC01-01 (2007). 

K. Araki, K. Emery, and M. Yamaguchi, “The First 

Grid-Connected Concentrator PV System in 

Industry Zone Using III-V Cells,” Proc. Renewable 

Energy 2006, International Energy Society, Chiba, 

Japan, Oct 9-13 (2006). 

Photovoltaic R&D

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Measurements and Characterization

54
 

A. Barnett, D. Kirkpatrick, C. Honsberg, D. Moore, 

M. Wanlass, K. Emery, R. Schwartz, D. Carlson, 

S. Bowden, D. Aiken, A. Gray, S. Kurtz, L. 

Kazmerski, T. Moriarty, M. Steiner, J. Gray, T. 

Davenport, R. Buelow, L. Takacs, N. Shatz, J. 

Bortz, O. Jani, K. Goossen, F. Kiamilev, A. 

Doolittle, I. Ferguson, B. Unger, G. Schmidt, E. 

Christensen, and D. Salzman, “Milestones Toward 

50% Efficient Solar Cell Modules,” Proc. 22nd 

European Photovoltaic Solar Energy Conf., Milan, 

Italy, September 3 (2007). 

J.R. Doyle, Y.Xu, R. Reedy, H.M. Branz, and A.H. 

Mahan, “Film Stoichiometry and Gas Phase 

Chemistry in HWCVD of a-SiGe:H,” Thin Solid 

Films, in press. 

K. Emery, ”Accuracy in Solar Cell and Module 

Measurements and Approaches to Improve 

Them,” Proc. 17th Workshop on Crystalline 

Silicon Solar Cells and Modules: Materials and 

Processes, Vail, CO, August 5-8 (2007). 

K. Emery, “Cell and Module Performance,” Proc. 

Solar Energies Technologies Review Meeting, 

April 17-19 (2007). 

K. Emery, ”ASTM Photovoltaic Performance 

Standards in Use at NREL,” ASTM International 

Standardization News, vol. 35 (7), pp. 30-33, July 

(2007). 

K. Emery, “Performance of Thin Film Modules,” 

2nd International Photovoltaic Industry Workshop 

on Thin Films, 11/9-10/2006, JRC/IES, Ispra, Italy 

(2006). 

J.F. Geisz, S. Kurtz, M.W. Wanlass, J.S. Ward, A. 

Duda, D.J. Friedman, J.M. Olson, W.E. McMahon, 

T.E. Moriarty, and J.T. Kiehl, “High-Efficiency 

GaInP/GaAs/InGaAs Triple-Junction Solar Cells 

Grown Inverted with a Metamorphic Bottom 

Junction,” Applied Physics Letters. Article No. 

023502, Vol. 91(2) (2007). 

T.A. Gessert, S. Asher, S. Johnston, M. Young, P. 

Dippo, and C. Corwine, “Analysis of CdS/CdTe 

Devices Incorporating a ZnTe:Cu/Ti Contact,” Thin 

Sol. Films, 515(15), 6103 (2007). 

M.A. Green, K. Emery, D.L. King, Y. Hishikawa, 

and W. Warta, “Solar Cell Efficiency Tables 

(version 29),” Progress in Photovoltaics Research 

and Applications, vol. 15, pp. 35-40 (2007). 

M.A. Green, K. Emery, D.L. King, Y. Hishikawa, 

and W. Warta, “Solar Cell Efficiency Tables 

(version 30),” Progress in Photovoltaics Research 

and Applications, vol. 15, pp. 425-430 (2007). 

J.B. Hurst, S.D. Lewis, M.M. Oye, A.L. Homes, Jr., 

A.J. Ptak, R.C. Reedy, “Unintentional Calcium 

Incorporation in Ga(Al,In,N)As,” J. Vac. Sci. 

Techn. B, 25(3), 1058 (2007). 

C.-S. Jiang, B. Yan, H. R. Moutinho, M. M. AlJassim, J. Yang, and S. Guha, “Light Soaking and 

Thermal Annealing Effects on the Micro-Electrical 

Properties of Amorphous and Nanocrystalline 

Mixed-Phase Silicon Solar Cells,” Mat. Res. Soc. 

Symp. Proc. Vol. 989, A02-05 (2007). 

C.-S. Jiang, B. Yan, Y. Yan, C.W. Teplin, R. 

Reedy, H.R. Moutinho, M.M. Al-Jassim, J. Yang, 

and S. Guha, “Effect of P Incorporation on 

Aggregation of Nanocrystallites in Amorphous and 

Nanocrystalline Mixed-Phase Silicon Thin Films,” 

J. Non-crystalline Solids (proceedings of 22nd 

ICANS), in press. 

C.-S. Jiang, B. Yan, Y. Yan, C.W. Teplin, R. 

Reedy, H.R. Moutinho, M.M. Al-Jassim, and J. 

Yang, “P-Induced Dispersion of Nanocrystallite Si 

in Amorphous Matrix,” J. Appl. Phys., in review. 

S.W. Johnston, R.K. Ahrenkiel, P. Dippo, M. Page, 

and W.K. Metzger, “Comparison of Silicon 

Photoluminescence and Photoconductive Decay 

for Material Quality Characterization,” 

Semiconductor Defect Engineering—Materials, 

Synthetic Structures and Devices II, S. Ashok, J. 

Chevallier, P. Kiesel, and T. Ogino, eds.,Mater. 

Res. Soc. Symp. Proc., Volume 994, Warrendale, 

PA (2007). 

D. Levi, E. Iwanizcko, S. Johnston, Q. Wang, and 

H.M. Branz, “Materials Optimization for Silicon 

Heterojunction Solar Cells Using Spectroscopic 

Ellipsometry,” Paper No. 0989-A24-04. Chu, V., et 

al., eds. Amorphous and Polycrystalline Thin-Film 

Silicon Science and Technology - 2007: 9-13 April 

2007, San Francisco, CA. Mater. Res. Soc. Symp. 

Proc., Vol. 989, Warrendale, PA, pp. 569-574; 

NREL Report No. CP-520-41527 (2007). 

F. Liu, M. J. Romero, K. M. Jones, A. G. Norman, 

M. M. Al-Jassim, D. Inns, and A. G. Aberle, 

“Intragrain Defects in Polycrystalline Silicon ThinFilm Solar Cells on Glass by Aluminum-Induced 

Crystallization and Subsequent Epitaxy,” accepted 

in Thin Solid Films. 

55

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Measurements and Characterization
 

J. M. Luther, M. Law, Q. Song, C. L. Perkins, M. 

C. Beard, and A. J. Nozik, “The Structural, Optical 

and Electrical Properties of Self-Assembled Films 

of PbSe Nanocrystals Coupled with 1,2­

Ethanedithiol,” ACS Nano., 2(2), 271-280 (2008). 

W.E. McMahon, K.E. Emery, D.J. Friedman, L. 

Ottoson, M.S. Young, J.S. Ward, C.M. Kramer, A. 

Duda, and S. Kurtz, “Daily Fill Factor Variation as 

a Diagnostic Probe of Multijunction Concentrator 

Systems During Outdoor Operation,” SPIE 

Proceedings, vol. 6649, High and Low 

Concentration for Solar Electric Applications II, 

ISBN 9780819467973, Sept. 10 (2007). 

W.K. Metzger, T.J McDonald., C.Engtrakul, J. L. 

Blackburn, G. D. Scholes, G. Rumbles, and M. J. 

Heben, “The Temperature Dependence of 

Excitonic Decay and Multiple States in Single-Wall 

Carbon Nanotubes,” J. Phys. Chem. C 111(9), 

3601-3606 (2007). 

W.K. Metzger, “The Impact of Lifetime 

Fluctuations and Grain Boundary Recombination 

on Silicon Solar Cells and Lifetime Maps,” 

submitted to Solar Energy Materials and Solar 

Cells. 

H.R. Moutinho, R.G. Dhere, B. To, C.-S. Jiang, 

and M.M. Al-Jassim, “Electron Backscatter 

Diffraction of CdTe Thin Films–Effects of CdCl2 

Treatment,” accepted for publication in the JVST 

A. 

H.R. Moutinho, R.G. Dhere, C.-S. Jiang, B. To, 

and M.M. Al-Jassim, “Electron-Backscatter 

Diffraction of Photovoltaic Thin Films,” Materials 

Research Society Proceedings, in press (2007). 

H.R. Moutinho, R.G. Dhere, C.-S. Jiang, T. 

Gessert, A. Duda, M. Young, W.K. Metzger, and 

M.M. Al-Jassim, “The Role of Cu on the Electrical 

Properties of CdTe/CdS Solar Cells–A CrossSectional Conductive Atomic Force Microscopy 

Study,” J. Vac. Sci. Technol. B 25, 361 (2007). 

H.R. Moutinho, R.G. Dhere, C.-S. Jiang, T. 

Gessert, A. Duda, M. Young, W.K. Metzger, X. Li 

and M.M. Al-Jassim, “Cross-Sectional Conductive 

Atomic Force Microscopy of CdTe/CdS Solar 

Cells: Effects of Etching and Back-Contact 

Processes,” Proc. 4th World Conf. on Photovoltaic 

Energy Conversion, Hawaii, 404 (2006). 

S. Pinegar, D. Nalley, and K. Emery, “Linearity 

Testing of Photovoltaic Cells,” U.S. Department of 

Energy, Journal of Undergraduate Research, vol. 

6 (2006). 

M.J. Romero, J. van de Lagemaat, G. Rumbles, 

and M. M. Al-Jassim, “Plasmon Excitations in 

Scanning Tunneling Microscopy: Simultaneous 

Imaging of Modes with Different Localizations 

Coupled at the Tip,” Appl. Phys. Lett. 90, 193109 

(2007). 

P. Rupnowski and B. Sopori, “Strength of PV 

Silicon Wafers–Fracture Mechanics Approach.” 

17th Workshop on Crystalline Silicon Solar Cells 

and Modules: Materials and Processes; Workshop 

Proceedings, Vail, Colorado, 5-8 August 2007, 

B.L. Sopori, ed., NREL/BK-520-42056, Golden, 

CO: National Renewable Energy Laboratory, 44­

48 (2007). 

B. Sopori, V. Mehta, P. Rupnowski, J. Appel, M. 

Romero, H. Moutinho, D. Domine, B. To, R. 

Reedy, M. Al-Jassim, A. Shaikh, N. Merchant, C. 

Khadilkar, D. Carlson, M. Bennet, (2007). 

“Fundamental Mechanisms in the Fire-Through 

Contact Metallization of Si Solar Cells: A Review.” 

17th Workshop on Crystalline Silicon Solar Cells 

and Modules: Materials and Processes; Workshop 

Proceedings, Vail, Colorado 5-8 August 2007, B. 

L. Sopori, ed., NREL/BK-520-42056, Golden, CO: 

National Renewable Energy Laboratory, 93-103 

(2007). 

P. Stradins, D. L. Young, Y. Yan, E. Iwaniczko, Y. 

Xu, R. C. Reedy, H. M. Branz, and Q. Wang, 

“Real-Time Optical Spectroscopy Study of SolidPhase Crystallization in Hydrogenated Amorphous 

Silicon,” Appl. Phys. Lett. 89, 121921 (2006). 

P. Stradins, O. Kunz, D.L. Young, Y. Yan, Y. Xu, 

R. Reedy, H.M. Branz, A.G. Aberle, and Q. Wang, 

“Comparative Study of Solid-Phase Crystallization 

of Amorphous Silicon Deposited by Hot-Wire CVD, 

Plasma-Enhanced CVD and Electron Beam 

Evaporation,” Proc. MRS Spring Meeting 

Symposium A, in press (2007). 

G. Teeter, “Cu2Te Synthesis and In-Vacuum 

Thermal Decomposition: Chemical-Kinetics 

Analysis and Comparison to Equilibrium VaporPressure Measurements,” Thin Sol. Films, 515, 

7886–7891 (2007). 

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G. Teeter, “X-Ray and Ultraviolet Photoelectron 

Spectroscopy Measurements of Cu-Doped 

CdTe(111)-B: Observation of TemperatureReversible CuxTe Precipitation and Effect on 

Ionization Potential,” J. Appl. Phys., 102, 034504­

1-7 (2007). 

X. Wu, J. Zhou, A. Duda, Y. Yan, G. Teeter, S. 

Asher, W. K. Metzger, S. Demtsu, S. H. Wei, and 

R. Noufi, “Phase Control of CuxTe Film and Its 

Effects on CdS/CdTe Solar Cell,” Thin Sol. Films 

515, 5798-5803 (2007). 

Y. Yan, C.-S. Jiang, R. Noufi, S.-H. Wei, H. R. 

Moutinho, and M. M. Al-Jassim, “Electrically 

Benign Behavior of Grain Boundaries in 

Polycrystalline CuInSe2 Films,” PRL 99, 235504 

(2007). 

Y. Yan, J. Li, S.-H. Wei, and M. Al-Jassim, “A 

Possible Approach to Overcome Doping 

Asymmetry in Wide Bandgap Semiconductor,” 

Phys. Rev. Lett. 98, 135506 (2007). 

Y. Yan, K.M. Jones, C.S. Jiang, X.Z. Wu, R. Noufi, 

and M.M. Al-Jassim, “Understanding the Defect 

Physics in Polycrystalline Photovoltaic Materials,” 

Physica B, in press (2007). 

J. Zhou, X. Wu, A. Duda, G. Teeter, and S. H. 

Demtsu, “The Formation of Different Phases of 

CuxTe and Their Effects on CdTe/CdS Solar 

Cells,” Thin Solid Films, 515, 7364-7369 (2007). 

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____________________________________________________________________________________ 

 

 

Resource and Safety Research
 

Environmental Health and Safety
 

Performing Organization: Brookhaven National Laboratory (BNL) 

Key Technical Contact: Vasilis Fthenakis (BNL), 631-344-2830, vmf@bnl.gov 

DOE HQ Technology Manager: Alec Bulawka, 202-586-5633, alec.bulawka@ee.doe.gov 

FY 2007 Budget: $470K 

Objectives 

•	 Assist in preserving the safe and environmentally friendly nature of photovoltaics (PV) and in 

minimizing environmental health and safety (EH&S) risks and associated costs, to ensure the 

economic viability of PV systems and public support for them. 

•	 Identify potential EH&S barriers for PV materials, processes, or applications and define strategies 

to overcome such barriers. 

•	 Maintain the EH&S Research Center as the world’s best resource on PV EH&S and for accurate 

information related to EH&S issues and perceptions. 

Accomplishments 

•	 Conducted a life-cycle analysis of buffer options for cadmium-indium-gallium-selenium (CIGS) 

photovoltaics; presented the results at the 22nd European Photovoltaic Solar Energy Conference, 

Milan, Italy. 

•	 With European research collaborators, conducted a life-cycle study of greenhouse gas (GHG) 

use in crystalline silicon (c-Si) etching operations; the results were presented at the 22nd 

European Photovoltaic Solar Energy Conference, Milan, Italy. 

•	 Invited to and participated in the 4th European PV Industry Forum Expert Panel on Sustainability 

Challenges, Milan, Italy. 

•	 Invited to and participated in the California Energy Commission Expert Workshop on Nuclear 

Power in California; presented a comparison of GHG emissions in the PV and nuclear fuel cycles. 

•	 Promoted and established international collaborative life-cycle environmental assessments (LCA) 

of PV energy technologies, enhancing the quality and quantity of PV environmental assessments. 

•	 Initiated International Energy Agency Task 12; conducted the first LCA Task 12 expert meeting. 

•	 Improved the recovery and purity of cadmium (Cd) and tellurium (Te) through recycling CdTe 

spent modules and manufacturing waste. 

•	 Assisted FirstSolar, PrimeStar Solar, and the University of Toledo with site-specific EH&S issues. 

•	 Answered several requests for EH&S information from industry and the public. 

Future Directions 

EH&S research at Brookhaven National Laboratory (BNL) will support the objectives of the Solar America 

Initiative (SAI) through the following: 

•	 Conduct LCA of near-commercialization technologies (e.g., III/V and c-Si PV concentrators). 

•	 Conduct preliminary LCA of 3rd-generation PV technologies, to guide the industry toward more 

environmentally friendly alternatives. 

•	 Accurately define the environmental profiles of solar technologies in comparison to those of other 

energy technologies. 

•	 Define the cost of recycling spent modules and determine scenarios for cost reductions. 

•	 Assist the industry in preventing accidents and releases of hazardous materials to the 

environment, and guide them toward environmentally friendly material and process options. 

•	 Conduct LCA of integrated PV and storage systems. 

•	 Answer inquiries from industry, the legislators, and the public about EH&S issues in solar energy 

cycles. 

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____________________________________________________________________________________ 

 

 

 

 

 

In addition, research at BNL will identify and characterize EH&S hazards associated with emerging 

materials, including nanomaterial forms, for the U.S. Department of Energy (DOE), its contractors, 

and the private sector.

1. Introduction 

The activities of the Environmental, Health and 

Safety (EH&S) Research Center focus on 

minimizing potential EH&S impacts associated 

with current and future photovoltaic (PV) energy 

systems and applications. This objective is 

accomplished by proactive research, rigorous 

industry outreach, and technical communications. 

The overall goal is to preserve the safe and 

environmentally friendly nature of PV and 

minimize EH&S risks and associated costs to 

ensure the economic viability of PV systems and 

public support for them. Minimizing EH&S risks 

and costs is paramount in achieving the Solar 

Program’s goal of $0.06/kWhr by 2020, and 

having the support of the public is a prerequisite 

for viability and growth on a scale that would 

support that low cost. 

The Center also serves as the world’s best 

resource on PV EH&S, providing accurate 

information related to EH&S issues and 

perceptions. This activity supports the overall 

communications and outreach objectives of the 

Solar Program. 

2. Technical Approach 

The major areas of Brookhaven National 

Laboratory’s (BNL's) activities are Hazard 

Identification and Characterization, Hazard 

Management, Industry Outreach, and Information 

Dissemination. Ongoing work is required because 

the PV industry is undergoing changes in types 

and quantities of materials as well as in 

manufacturing processes and scale. These 

activities are also needed because continuous 

vigilance is required for safety and loss prevention. 

Task 1: Identification and Characterization of 

EH&S Issues 

BNL continues to monitor process, material, and 

application alternatives being investigated by 

DOE, the National Renewable Energy Laboratory 

(NREL), Sandia National Laboratories (SNL), and 

industry to determine if any potential safety, 

health, and environmental hazards exist and if so, 

to quantify those hazards. This investigation 

covers the entire life cycle of photovoltaics, from 

the production of materials used in manufacturing 

solar cells, modules, and systems to eventually 

disposing of and/or recycling them. 

Task 2: Hazard Management 

BNL’s studies on safety, loss prevention, and 

environmental impact are disseminated to the 

industry to assist them in protecting PV facilities. 

Task 3: Industry Outreach and Support to DOE 

and the National Center for Photovoltaics (NCPV) 

Industry outreach activities include frequent 

interactions with EH&S personnel, site visits, 

guidance on EH&S issues and concerns, and 

assistance with new facilities. 

Task 4: Information Dissemination 

Providing accurate and objective information on 

PV EH&S issues is crucial for the PV industry as 

installations grow to levels that attract public 

interest and scrutiny. 

Task Title FY 2007 

Budget ($K) 

Hazard 

Identification/Characterization 180 

Hazard Management/Recycling 90 

Industry Outreach/ 

DOE/NCPV Information 

Dissemination 

130 

IEA Task 12 70 

3. Results and Accomplishments 

Task 1 

•	 Conducted and published (a) a life-cycle 

investigation of CdS alternatives in CIGS PV 

systems and (b) a life-cycle investigation of 

greenhouse gas emissions (GHG) in c-Si 

etching operations. 

•	 Invited to and participated in two high-impact 

expert panels (EPIA/sustainability and 

California Energy Commission/nuclear 

issues). 

• Conceptualized, organized and currently 

manage Task 12 of the International Energy 

Agency (IEA). 

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Task 2 

•	 Advanced the recycling of CdTe PV by 

achieving a recovery of 99.99% pure cadmium 

and 99.99% pure tellurium through optimized 

separations. 

•	 Accomplished the advancement just described 

on a laboratory scale 10 times greater than 

that of the previous year while incorporating a 

wide variety of actual manufacturing waste. 

Task 3 

•	 Provided facility-specific assistance to First 

Solar and PrimeStar; advised dozens of PV 

community members on EH&S issues. 

•	 Organized the first IEA PV task 12 meeting, 

bringing together analysts from several 

countries for interaction. 

Task 4 

•	 Answered several requests for EH&S 

information from different agencies, business 

partners, citizen organizations, and the media. 

•	 Invited to and participated in high-impact 

expert panel discussions. 

•	 Published and presented extensively. 

4. Planned FY 2008 Activities 

Task 1: Hazard Identification/Characterization 

This task is part of BNL’s proactive research to 

overcome EH&S barriers to support for largescale implementation of PV. Activities planned for 

FY 2008 include the following: 

•	 Conduct LCA study of III/V and c-Si PV 

concentrators. 

•	 Coordinate joint research on PV LCA for c-Si 

and thin-film PV with European collaborators. 

•	 Organize a Materials Research Society 

Symposium on LCA. 

Task 2: Hazard Management/Recycling 

These activities are pivotal in preserving the safe 

and environmentally friendly nature of the PV 

industry as it moves toward large-scale 

manufacturing. In FY 2008, research at BNL will 

focus on the following: 

•	 Assist the industry in developing a recycling 

infrastructure and in implementing recycling 

options. 

•	 Conduct a silane safety seminar with industry 

participation. 

Task 3: Industry Outreach/Support to DOE and the 

NCPV 

•	 Serve as the lead organizer and U.S. 

representative to IEA PV EH&S Task 12. 

•	 Guide the industry and R&D laboratories on 

accident prevention and pollution prevention. 

•	 Support DOE and the NCPV as needed. 

Task 4: Information Dissemination 

The results of BNL’s research will be disseminated 

through new publications, e-mail, and the Web. 

The PV EH&S Research Center serves as a 

clearinghouse for EH&S information requested by 

potential customers, business partners, citizen 

organizations, and the media. Such inquiries have 

been increasing as the industry, universities, and 

national laboratories respond to the SAI challenge 

to achieve cost-effective production of solar 

electricity by 2020. 

5. FY 2007 Special Recognitions 

•	 Invited to participate in the EPIA Expert Panel 

on Sustainability; the subsequent presentation 

was broadcast widely. 

•	 Invited to participate in the California Energy 

Commission’s Expert Panel on Nuclear Power 

in California; the subsequent testimony was 

used for the 2007 Integrated Energy Policy 

Report. 

6. Major FY 2007 Publications 

V.M. Fthenakis and H.C. Kim, “Greenhouse Gas 

Emissions from Solar Electric and Nuclear 

Power: A Life Cycle Study,“ Energy Policy, 35, 

2549-2557 (2007). 

V.M. Fthenakis, W. Wang, and H.C. Kim, “Life 

Cycle Inventory Analysis of the Production of 

Metals used in Photovoltaics,” Renewable and 

Sustainable Energy Reviews (in press). 

V.M. Fthenakis and H.C. Kim, “Photovoltaics 

Life Cycle Analysis,” Advances of Solar Energy, 

invited (in press). 

V.M. Fthenakis, H.C. Kim, and E. Alsema, 

“Emissions from Photovoltaic Life Cycles,” 

Environmental Science and Technology (in 

press). 

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K. Zweibel, J. Mason, and V. Fthenakis, “A Solar V. Fthenakis and H.C. Kim, “Cu(InGa)Se2 ThinGrand Plan,” Scientific American, 298(1), 64-73 Film Solar Cells: Comparative Life-Cycle 

(2008). Analysis of Buffer Layers,” Proceedings of the 

22nd European Photovoltaic Solar Energy 

M. de Wild-Scholten, E. Alsema, V. Fthenakis, Conference, Milan, Italy, 3-7 September (2007). 

G. Agostinelli, H. Dekkers, K. Roth, and V. 

Kinzig, “Fluorinated Greenhouse Gases in M. Ragei, P. Frankl, E. Alsema, M. de WildPhotovoltaic Module Manufacturing: Potential Scholten, V. Fthenakis, and H.C. Kim, “Life 

Emissions and Abatement Strategies,” 

Proceedings of the 22nd European Photovoltaic 

Cycle Assessment of Present and Future 

Photovoltaic Systems,” Proceedings of the AIST 

Solar Energy Conference, Milan, Italy, 3-7 Symposium Renewable Energy, Chiba, Japan, 

September (2007). 11 October (2007). 

. 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

Resource and Safety Research
 

Solar Resource Characterization 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Dave Renné (NREL), 303-384-7408, david_renne@nrel.gov 

DOE HQ Technology Manager: Jeffrey Mazer, 202-586-2455, jeffrey.mazer@ee.doe.gov 

FY 2007 Budget: $420K 

Objectives 

•	 Complete a 15-year update (1991–2000) of the National Solar Radiation Data Base (NSRDB). 

•	 Produce an enhanced 1998–2005 10-km gridded data solar product for the United States. 

•	 Produce an updated Typical Meteorological Year (TMY) data set from the updated 1991–2005 

NSRDB. 

•	 Implement Task 36 “Solar Resource Knowledge Management” under the International Energy 

Agency Solar Heating and Cooling (IEA/SHC) Programme. 

Accomplishments 

•	 Completed the 1991–2005 NSRDB update and documentation, including the 10-km satellitederived data grid from the State University of New York (SUNY) at Albany. 

•	 Worked with National Climatic Data Center (NCDC) and established a distribution method for the 

updated NSRDB and 10-km gridded data via the NCDC distribution infrastructure. 

•	 Held NSRDB forum and rollout at the annual conference of the American Solar Energy Society 

(ASES). 

•	 Technical results in several topical areas coming out of IEA Task 36, Solar Resource Knowledge 

Management. 

Future Directions 

•	 Produce a TMY data set based on the updated NSRDB. 

•	 Finalize plans for producing a 10-km gridded data set for 1991–1998. 

•	 Produce reports through the IEA Task 36 that benchmark and quantify various solar resource 

assessment approaches developed by different countries and international institutions, including 

NREL’s NSRDB. 

1. Introduction 

This project addresses solar resource assessment 

as outlined in the U.S. Department of Energy’s 

Solar Energy Technologies Program Multi-Year 

Technical Plan. The project includes access to the 

data and characterization of the solar resource 

and addresses the needs of designers, modelers, 

and resource assessment interests, both in the 

United States and internationally. This multiyear 

project is intended to update the 1961–1990 

National Solar Radiation Data Base and derivative 

products such as TMY data sets as well as to 

implement the IEA Solar Resource Knowledge 

Management task (Task 36) for benchmarking 

international solar resource data sets. Work 

performed in FY 2007 included (1) the completion 

and release of an NSRDB update and (2) the 

continued implementation of several subtasks 

under the IEA/SHC Solar Resource Knowledge 

Management task. 

2. Technical Approach 

Two tasks are under way in the Solar Resource 

Characterization Project: (1) a domestic task 

focused on updating NSRDB products and (2) an 

international task that allows the NSRDB to be 

benchmarked against international solar resource 

assessment methods. Previous work allowed us 

to select a solar radiation model (METSTAT) and 

develop a plan for final NSRDB production. 

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The IEA/SHC Solar Resource Knowledge 

Management task provides a collaborative 

mechanism to enable researchers from a number 

of international research institutions to compare 

and benchmark various approaches for assessing 

solar resources, allowing the new NSRDB to be 

benchmarked against these other methods. 

During this reporting period, the third and fourth 

task experts meetings were held (March 2007 and 

October 2007). In these meetings, experts from 

the participating countries presented research 

results and future plans on topics directly related 

to the task. In addition, a mid-term review of 

technical progress was presented to the IEA/SHC 

Executive Committee in December 2007 

A breakdown of the total project funding is shown 

in the following table: 

Task Title FY 2007 

Budget ($K) 

IEA Task 36 Solar Resource 

Knowledge Management 100 

NSRDB Update and Release 320 

3. Results and Accomplishments 

3.1 National Solar Radiation Data Base 

The National Weather Service’s changeover to 

automated stations eliminated human-observed 

total and opaque sky cover amounts that had been 

used as inputs to the METSTAT model, which in 

turn was used for the 1961–1990 NSRDB. To 

adapt the model to currently available data sets, 

we derived equivalent sky cover inputs (total and 

opaque cloud cover) from a combination of 

Automated Surface Observing System (ASOS) 

and ASOS supplemental cloud measurements; the 

latter were derived from Geostationary Operational 

Environmental Satellite (GOES) satellite data. 

ASOS detects clouds to 12,000 ft (3660 m), 

whereas the ASOS supplemental cloud 

measurements provide sky cover estimates for 

heights above 12,000 ft for a 50 km x 50 km area 

centered on the ASOS station. 

Based on foundational work in FY 2006, including 

coordination of a procedural review of the NSRDB 

update procedures by external experts, we 

completed the 1991–2005 NSRDB, which updated 

the original 1961–1990 NSRDB. This work 

included a 10-km gridded solar database 

produced in collaboration with SUNY Albany. We 

also worked with the NCDC in the U.S. 

Department of Commerce to incorporate the 

NSRDB in the center’s data distribution 

infrastructure. In July 2007, we held an NSRDB 

forum and product rollout at the ASES annual 

conference. This forum also sought input from 

attendees to help guide future work in solar 

resource assessment. 

The updated NSRDB holds data for 1480 sites in 

the United States, about 850 of which have serially 

complete data for the 15-year period of record. 

The remaining sites were included for applications 

that don’t require a serially complete data set but 

that can benefit from some characterization of the 

solar resource. Figure 1 is a map of the NSRDB 

sites overlaid with the 239 sites in the original 

NSRDB. 

Fig. 1. Map of NSRDB sites. 

Work also included the production of monthly and 

annual means for the 10-km gridded data set. 

Figure 2 shows a map of the global horizontal 

latitude tilt for these summary data sets. 

Fig. 2. Global horizontal latitude tilt derived from 

SUNY gridded solar data set. 

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3.2 IEA Task 36, Solar Resource Knowledge 

Management 

The three subtasks in Task 36 are contributing to 

achieving the vision of fast and easy access to 

relevant, qualified, and reliable solar resource 

information that has been benchmarked to 

international standards. 

Subtask A: Standard qualification for solar 

resource products. This subtask is focusing on: 

•	 Coherence and benchmarking of models 

producing surface irradiance values from 

satellite data; this includes SUNYA, NREL's 

Climatological Solar Radiation (CSR) model, 

and the NASA Surface Meteorology and Solar 

Energy (SSE) models, which are also being 

used for the NSRDB updates 

•	 Ground truth validations with high-quality 

surface network data, such as the Baseline 

Surface Radiation Network (BSRN) 

•	 Definition of validation protocols and 

measures of end-product confidence 

•	 Cross-satellite platform and cross-model 

comparisons. 

Subtask B: Common structure for archiving and 

accessing resource products. This subtask 

focuses on the following: 

•	 Development of worldwide networking 

between distributed data centers, resulting in a 

global coverage for high-quality solar resource 

data 

•	 Development of information and data 

exchange protocols 

•	 Reliable and fast end-user access to specific 

queries 

•	 Preparation of data documentation for specific 

end-user applications. 

The main outcome of Subtask B will be a unique 

Web entry point that performs a smart network of 

resources and products. Specifically, Subtask B 

will build on existing Web services, such as the 

SoDa or NASA portals, to construct an advanced 

prototype of the distributed information system. 

Resources (e.g., solar resource databases) will be 

accessible through a Web server and data 

providers will be connected on a voluntary basis to 

this information system. Providers of such 

resources will be organizations such as NREL, 

NASA, and the German Aerospace Center (DLR). 

The Web service will be maintained by Task 36 

partners, and, where required by the data 

providers, could involve possible commercial 

revenues. 

Subtask C: Improved techniques for solar 

resource characterization and forecasting. This 

subtask covers R&D work and focuses chiefly on: 

•	 Improved Satellite Retrieval Methods for Solar 

Radiation Products: This activity focuses on 

key model input parameters and 

methodologies, such as cloud indices, 

radiative transfer schemes, aerosol data 

retrievals, and treatment of snow and other 

surface albedo artifacts. The activity also 

addresses ways of improving the spatial 

resolution of satellite-derived broadband solar 

resource products. 

•	 Climatological Analysis of Solar Resources: 

To ascertain future impacts on system 

performance due to climate variations, this 

activity includes the analysis of long-term 

surface and satellite-derived data sets and 

climate models, specifically addressing natural 

long-term fluctuations associated within the 

ocean-atmosphere system, such as the 

Southern Oscillation/El Nino. 

•	 Forecasting of Solar Radiation: This activity 

investigates different approaches for 

developing solar resource forecasts based on 

global numerical weather predictions and 

extrapolation of cloud motion vectors. 

Preliminary results of comparisons of long-term 

satellite-derived climatological solar data with high 

quality (BSRN) ground data are shown in Figure 3. 

The figure shows good agreement between the 

satellite-derived and ground-based data sets, with 

a very slight trend toward overestimates of satellite 

values when surface radiation values are high. 

Fig. 3. Intercomparison of the NASA Surface 

Radiation Budget Products for total ground 

irradiance vs. BSRN precision measurements 

(from Zhang and Stackhouse, NASA; presented at 

the IEA/SHC Task 36 Fourth Experts Meeting). 

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At the Fourth Experts Meeting, the Joint Research 

Center reported on the Photovoltaic Geographic 

Information System (PVGIS) Web site, which was 

developed to provide users with an easy 

interactive application that provides free access to 

solar resource data for Europe, Africa, and 

southwestern Asia, as well as ambient 

temperature data for Europe. The PVGIS site also 

provides assessment tools that calculate solar 

radiation for fixed and sun-tracking systems, 

calculations of energy output for grid-connected 

photovoltaic systems, and the performance of 

stand-alone PV systems (Africa only). Tools on 

the Web site provide the user with key overview 

information on investment decisions to support 

project developers and the manufacturing industry. 

The applications are based on the Google Maps 

interface and provide several different formats of 

information, including the estimated accuracy of 

the calculations. Web-based estimates for single 

sites can be accessed through the following URL: 

http://re.jrc.ec.europa.eu/pvgis/apps3/pvest.php. 

Gridded data sets at approximately 10-km by 10­

km resolution can also be accessed. An example 

of the PVGIS interface is shown in Figure 4. 

Fig. 4. Example page from the PVGIS Web site 

(courtesy of T. Huld, M. Šúri, and T. Cebecauer of 

the Joint Research Centre, Ispra, Italy). 

4. Planned FY 2008 Activities 

Activities in the Solar Resource Characterization 

task in 2008 will focus on releasing additional 

products related to the NSRDB, such as TMY 

data, and undertaking research in short-term solar 

resource forecasting to support utility operations 

for distributed PV generation. In addition, the 

participants in IEA/SHC Task 36 will focus on 

developing appropriate benchmarking procedures 

for comparing international solar data sets and on 

methodologies for improving satellite-derived 

estimates, with particular emphasis on highresolution and long-term data. Testing of various 

solar resource forecasting methodologies is 

underway in Europe, and a cooperative activity 

among the University of Oldenburg, NASA 

Langley Research Center, and SUNY/Albany is 

underway to test methodologies at specific 

locations in the United States. 

5. Major FY 2007 Publications 

S. Wilcox, M. Anderberg, W. Beckman, R. George, 

C. Gueymard, W. Marion, D. Myers, R. Perez, M. 

Plantico, D. Renne, P. Stackhouse, and F. 

Vignola. “Completing Production of the Updated 

National Solar Radiation Database for the United 

States,” Proc. Solar 2007, American Solar Energy 

Society (2007). 

D. Myers, “Relative Performance of Multiple Solar 

Radiation Resource Assessment Data Sources,” 

Proc. Solar 2007, American Solar Energy Society 

(2007). 

R. Perez, M. Kmiecik, S. Wilcox, and P. 

Stackhouse, “Enhancing the Geographical and 

Time Resolution of NASA SSE Time Series Using 

Microstructure Patterning,” Proc. Solar 2007, 

American Solar Energy Society (2007). 

R. Perez, M. Kmiecik, J. Schlemmer, L. Root, K. 

Moore, and P. Stackhouse, “NASA Langley 

Research Center: Evaluation of PV Generation 

Capacity Credit Forecast on Day-Ahead Utility 

Markets,” Proc. Solar 2007, American Solar 

Energy Society (2007). 

R. George, S. Wilcox, M. Anderberg, and R. 

Perez, “National Solar Radiation Database 

(NSRDB)—10 km Gridded Hourly Solar 

Database,” Proc. Solar 2007, American Solar 

Energy Society (2007). 

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Advanced Materials and Devices 

The Advanced Materials and Devices effort carries out research in semiconductor material 

properties, device mechanisms, and fabrication processes to improve the efficiency, stability, and 

cost of photovoltaic energy conversion. The effort focuses on thin-film materials and modules 

(which hold promise for major reductions in PV costs), module manufacturing methods, and 

module reliability. 

The Thin-Film PV Partnership has formed strong research teams to focus R&D on promising thinfilm candidates, such as amorphous silicon, cadmium telluride, copper indium diselenide, and thin 

silicon. These research teams comprise laboratory, industry, and university researchers who work 

to solve generic issues as well as industry-specific problems. 

The overall objective of the PV Module Reliability Project is to work with industry to develop PV 

modules that have 30-year service lifetimes. This project also provides critical performance and 

reliability testing and benchmarking of modules to validate the progress and accomplishments of 

the Solar Program’s investments in PV module technology R&D. The Inverter and BOS 

Development Project is directed toward improving inverters and balance of systems (BOS) 

through the High-Reliability Inverter Initiative. 

In PV Manufacturing R&D, strong partnerships with the U.S. PV industry have been formed with 

the goal of retaining and enhancing the industry’s leadership in the development and manufacture 

of PV modules. Many problems in manufacturing R&D exist whose solutions are critical to further 

reducing the cost of PV. 

Achievements in Advanced Materials and Devices for FY 2007 include the following: 

Systems Development 

•	 Selected 10 companies to become subcontracts, emphasizing way to overcome the 

barriers to manufacturing scale-up and 2010 commercialization. 

•	 Selected 12 Technology Pathway Partnerships that foster development within the 

domestic PV industry. These projects will catalyze collaboration across the value chain to 

cut costs, optimize PV-system design, and assure superior performance and reliability. 

Component Development 

•	 Achieved a significant milestone, a higher efficiency thin-film module of 12.2%. 

•	 Evaluated U.S. industry participants to assess and determine the needs for additional 

manufacturing research and development. 

Systems Analysis 

•	 Completed drafts of 14 reports on “Renewable Systems Interconnection.” 

•	 Developing a model and other tools to examine the impacts of high levels of PV 

penetration on the U.S. electricity generation system.
 

•	 Developed a photovoltaic (PV)-system inverter model for use within the Solar Advisor 

Model. 

Systems Testing and Evaluation 

•	 Determined inverter performance, power quality, and utility compatibility capabilities for 

commercial inverters and residential PV inverters. 

•	 Conducted performance tests to support the development of industry solar modules. 

•	 Developed interfacial measurement technique of layer adhesion inside modules. 

•	 Evaluated the performance of system configurations for PV manufacturing companies 

and characterized additional modules and arrays. 

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Component Testing and Evaluation 

•	 Performed 26 spectral and 405 solar broadband radiometer calibrations for national 

laboratories, industry, and academic partners. 

PDIL Infrastructure, Engineering, and Integration 

•	 Developed the design of process-integration-compatible measurement and 

characterization equipment developed at NREL, including resonance-coupled 

photoconductive decay, photoluminescence imaging, and a special spectroscopic 

ellipsometry chamber; integrated this equipment into a central robotic transfer chamber 

along with a sputtering/etching chamber and a chamber for studying plasma enhanced 

chemical vapor depositions. 

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___________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

Systems Development 

Solar America Initiative Photovoltaic Incubator 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact:	 Martha Symko-Davies (NREL), 303-384-6528, 

 Martha_symko_davies@nrel.gov 

DOE HQ Technology Manager:	 Marie Mapes, 202-586-3765, marie.mapes@ee.doe.gov 

FY 2007 Budget:	 $10,127K (NREL) 

Objectives 

•	 Shorten the timeline for companies to transition prototype and pre-commercial photovoltaic (PV) 

technologies into pilot and full-scale manufacture. 

•	 Move companies into commercial production quickly and successfully. 

•	 Position companies to be competitive for Technology Pathway Partnership (TPP) funding 

opportunities. 

•	 Focus the efforts of subcontractors to a limited number of high-impact module technology 

improvement opportunities (TIOs) that lay on the critical path to scaling-up their technology to full 

manufacture. 

Accomplishments 

•	 Completed merit criteria and analysis to select negotiations for subcontracts. 

•	 Selected 10 subcontracts for negotiations, including: Blue Square, Solopower, AVA, Primestar, 

Plextronics, Solaria, Microlink, Enfocus, Solfocus, and CaliSolar. 

•	 Concluded fiscal year negotiations in September 2007 (FY 2007). 

•	 Awarded the majority of subcontracts in October and November of FY 2008. 

Future Directions 

•	 Issue a second letter of interest (LOI) for the Solar America Initiative Photovoltaic (SAI PV) 

Incubator in FY 2008. 

•	 Complete merit review for responses to the LOI. 

•	 Complete stage-gate review of individual progress versus deliverables by late summer, FY 2008. 

1. Introduction 

The primary objective of the Solar America Initiative Photovoltaic (SAI PV) Technology Incubator 

project is to shorten the timeline for companies to 

transition PV technologies into pilot and full-scale 

manufacture. The incubator concept generally will 

apply to those companies that were not far enough 

along in technology and product development 

pathways to be positioned to qualify for the first of 

the SAI’s Technology Pathway Partnership (TPP) 

awards. Successful participation in the SAI PV 

Technology Incubator project will quickly move 

companies into commercial production and position those companies to be competitive for the 

next TPP funding opportunity, which is expected to 

be issued in 2010. 

The SAI provides significant opportunities for collaboration and partnership among industry and 

university researchers to develop and improve 

solar-energy technologies. This SAI PV Technology Incubator project targets research and 

development on PV cell and module prototypes 

with demonstrated functionality in either large-area 

cell/module form or, preferably, prototypes 

produced in pilot-scale operations. The emphasis 

on proposed activities should be focused on the 

barriers to manufacturing scale-up and 2010 

commercialization. 

Advances are needed to achieve prototype 

modules and pilot production, which will be 

facilitated through projects funded under this LOI. 

It is expected that the subcontract duration will be 

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for 18 months for each award made under this 

solicitation. Entrance opportunities for the Incubator project are anticipated every 9 months as 

funding opportunities become available. The 

entrance criterion is demonstrated PV cells or 

process lab devices or modules. A successful 

demonstration for the entrance criterion is a 

quantifiable and verifiable baseline measurement. 

The successful exit criterion would be for prototype modules and pilot production demonstration 

greater than 3 megawatts per year (MW/year). 

These entry and exit criteria are provided to 

applicants as general guidelines for maturity of 

technology that the DOE intends to fund through 

this LOI, but the guidelines are flexible—applicants 

may be more advanced than the stated entrance 

criteria at the time of application, and may plan to 

be more advanced than ~3MW/year pilot production at the completion of their “incubator” project. 

2. Technical Approach 

2.1. SAI PV Incubator Management 

The Project Management and Support subtask 

addresses: (1) management of the Incubator 

project; (2) management of subcontracts awarded; 

and (3) coordination of NREL in-house activities in 

support of the small businesses 

2.2. SAI PV Incubator Scope 

The National Renewable Energy Laboratory 

(NREL) solicited LOIs from individual U.S. small 

businesses and U.S. small-business-led teams 

that were working on research and development of 

demonstrated PV cell and module prototypes. 

The LOI emphasized overcoming the barriers to 

manufacturing scale-up and 2010 commercialization. 

Topic Areas include: 

•	 Novel wafer-based silicon modules; 

•	 Polycrystalline thin films; 

•	 Film silicon on a foreign substrate; 

•	 High-efficiency cells, including 

multijunction, and CPV module concepts; 

•	 Organic PV, dye-sensitized solar cells, or 

other polymer-based solar cells; 

•	 Low-X concentration CPV systems with 

limited or 1-axis tracking module designs; 

and 

•	 Low-X Si modules, 3-10X. 

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____________________________________________________________________________________ 

 

 

____________________________________________________________________________________ 

Systems Development 

Solar America Initiative Project Monitoring 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

 DOE Golden Field Office (DOE/GO) 

Key Technical Contacts:	 Roland Hulstrom (NREL), 303-384-6420, roland_hulstrom@nrel.gov 

Charles Hanley (SNL), 505-284-4435, cjhanle@sandia.gov 

DOE HQ Technology Manager:	 Thomas Kimbis, 202-586-7055, tom.kimbis@ee.doe.gov 

FY 2007 Budgets:	 $998K (NREL), $580K (SNL) 

Objectives 

•	 Oversee technical progress of the SAI Technology Pathway Partnerships (TPPs). 

•	 Verify progress towards TPPs and program goals (including the use of the Solar Advisor Model 

tool), coordinating collaborative efforts between TPPs and the labs, coordinating T&E activities 

between the labs and the TPPs, and assuring readiness on all parts for stage-gate reviews. 

Related metrics are those provided by TPPs in their applications, as well as the key performance 

parameters described in the TPP Funding Opportunity Announcement (FOA). The key protocol 

from this effort is an operational format for the conduct and evaluation of stage-gate reviews. 

Accomplishments 

•	 Provided the scientific/engineering foundations for the development of the plans for the Solar 

America Initiative (SAI) TPP FOA/Project. 

•	 Served as technical reviewers of the industry applications, and subsequently as the technical 

monitors of the winning applications and projects. 

Future Directions 

•	 Continue to monitor these activities throughout the duration of SAI, slated to run until 2015. 

These activities will be revamped at 3-year intervals, concurrent with the issuance of new SAI 

solicitations. 

•	 Monitor oversight and collaboration of stage-gate reviews and assessment of deliverable 

provided by TPPs to assure progress toward goals. 

1. Introduction 

NREL and SNL provide selected expertise, based 

on the specific nature of each of the SAI TPPs, for 

assisting DOE with the detailed technical 

assessment and monitoring of the TPPs. This 

expertise ranges from the applied research to the 

systems development area. NREL and SNL key 

focus of their role/responsibilities are the stagegate reviews of each of the TPPs. Along these 

lines, NREL and SNL anticipate that a portion of 

their support, specific to the TPP Technical 

monitoring, will include selected analyses (e.g. 

using the SAM model or other research and 

development tools), literature reviews, etc, to 

produce credible technical assessments of the 

progress, deliverables, and issues associated with 

the TPPs. Another aspect of the NREL/SNL roles 

will include attending to the integration of the 

technical efforts within the TPPs with the in-house 

R&D at NREL and/or SNL. This is done to ensure 

the most effective and efficient use of the DOE 

investments (in the TPPs and NREL/SNL) and to 

help resolve any unforeseen technical and/or 

engineering barriers. 

2. Results and Accomplishments 

NREL and SNL scientists and engineers provided 

the scientific/engineering foundations for the 

development of the plans for the SAI’s Technology 

Pathway Partnerships (TPPs) FOA/Project, which 

are subcontracted R&D through DOE/GO. 

NREL/SNL experts served as technical reviewers 

of the industry applications and subsequently as 

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the technical monitors of the winning applications 

and projects. 

3. Planned FY 2008 Activities 

The main areas of focus for SAI project monitoring 

include oversight and collaboration of stage-gate 

reviews and assessment of deliverable provided 

by TPPs to assure and verify progress toward 

goals. This includes utilization of the SAM tool to 

assess results in terms of SETP’s key 

performance parameters. These tasks will be 

executed through close collaboration with other 

lab staff involved in test & evaluation, systems 

analysis and benchmarking, and overall program 

management. In addition, monitors will coordinate 

release of public information with the 

communication and outreach personnel where 

appropriate. 

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Systems Development 

Technology Pathway Partnership 

Performing Organizations: Amonix 

The Boeing Company 

BP Solar, Inc. 

Dow Chemical Company 

GE Global Research 

GreenRay, Inc. 

Konarka Technologies, Inc. 

Nanosolar, Inc. 

Soliant Energy, Inc. 

Sunpower, Inc. 

United Solar Ovonic LLC 

National Renewable Energy Laboratory (NREL) 

Sandia National Laboratories (SNL) 

Key Technical Contacts: Carolyn Elam, DOE Golden Field Office (DOE/GO), 303-275-4953, 

carolyn.elam@go.doe.gov 

Jim Payne, DOE/GO, 303-275-4756, jim.payne@go.doe.gov 

Brad Ring, DOE/GO, 303-275-4930, bradley.ring@go.doe.gov 

Holly Thomas, DOE/GO, 303-275-4818, holly.thomas@go.doe.gov 

DOE HQ Technology Manager: Marie Mapes, 202-586-3765, marie.mapes@ee.doe.gov 

FY 2007 Budgets: $34,331,113 TPP Recipients, $898,751 (NREL), $600,000 (SNL) 

Objectives 

•	 Bring better products to market and enable new applications. Develop modular, turnkey PV 

systems that provide residential and commercial customers with a complete solution and 

attractive value proposition (e.g., enabling BIPV and zero-energy homes). Develop designs and 

supply chains for large-field PV installations to service large commercial and utility RPSgenerating requirements. Help U.S. companies to leapfrog global competition by providing the 

best designed, lowest-cost solar-energy solutions. 

•	 Foster development of the domestic PV industry. Catalyze collaboration across the value chain 

to: (1) squeeze out costs; (2) better optimize PV-system design; and (3) assure superior 

performance and reliability. Demonstrate novel manufacturing processes that provide U.S. 

industry with a cost advantage, and that facilitate manufacturing scale-up. 

•	 Impact the U.S. energy economy with results. Accelerate development of U.S.-produced PV 

systems so that PV-produced electricity reaches parity with the cost of electricity in grid-tied 

markets across the nation by 2015. Enable expansion of the annual U.S. production capacity of 

PV systems from 240 megawatts (MW) in 2005 to as much as 2,850 MW by 2010, representing a 

ten-fold increase. Foster research that will lower the cost of PV-generated electricity to $0.05 to 

$0.10 per kilowatt (kWh) by 2015 in residential, commercial, and utility markets. 

Accomplishments 

•	 Selected 12 projects, based upon merit and program review of submitted proposals. 

•	 Defined roles and responsibilities of program management team, including technical monitors at 

NREL and Sandia. 

•	 Completed 12 awards. The award recipients/subrecipients include more than 50 companies, 

14 universities, 3 non-profits, and 2 national laboratories in 20 states across the United States. 

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____________________________________________________________________________________ 

Future Directions 

•	 Develop PV systems so that by 2015 PV-produced electricity reaches parity with the cost of electricity in select grid-tied target markets across the nation and the U.S.-installed domestic capacity 

of PV systems is expanded to 5 to 10 gigawatts (GW). 

1. Introduction 

In January 2006, President Bush announced the 

Advanced Energy Initiative. This initiative is 

designed to reduce the nation’s dependence on 

foreign sources of energy by promoting broader 

research and development (R&D), and to achieve 

substantive breakthroughs in a variety of energy 

resources, including solar photovoltaic systems. 

An integral part of this initiative is the DOE Solar 

America Initiative (SAI) Technology Pathway 

Partnerships (TPP). Authorized under the Energy 

Policy Act of 2005, the SAI TPP represents a 

significant enhancement of DOE’s business 

strategy of partnering with entities in the industry 

to accelerate commercialization of photovoltaic 

(PV) system R&D to meet aggressive cost and 

installed-capacity goals. 

The SAI TPP program will accelerate comercialization of solar photovoltaic (PV) systems by 

2015. The goal is to have PV electricity generation 

that is competitive with conventional sources of 

electricity in all domestic grid-tied market sectors. 

The specific goals of the 9-year TPP mission are: 

•	 Accelerate development of U.S.-produced PV 

systems substantively, so that PV-produced 

electricity reaches parity with the cost of electricity in select grid-tied target markets across 

the nation (identified in Table 1, below). 

•	 Expand the U.S.-installed domestic capacity of 

PV systems to 5 to 10 gigawatts (GW). 

Table 1. Cost Targets for Grid-Connected PV 

Systems in Key Market Sectors 

1 Costs are based on constant 2005 dollars. 

2 Current costs are based on electric-generation with conventional sources. 

3 Cost to customer (customer side of meter). 

4 Cost of generation (utility side of meter).
 

Market 

Sector 

Current 

U.S. 

Market 

Range 

(c/kWh)1,2 

Solar Electricity Cost—Current 

and Projected (c/kWh)1 

Benchmark Target 

2005 2010 2015 

Residential3 5.8–16.7 23–32 13–18 8–10 

Commercial3 5.4–15.0 16–22 9–12 6–8 

Utility4 4.0–7.6 13–22 10–15 5-7 

The cost basis of electric energy in these markets 

is the kilowatt hour, therefore the SAI TPP program uses targets for PV systems based on the 

Levelized Cost of Energy (LCOE) delivered by 

these systems. The LCOE is a measure of total 

lifetime costs of a PV system divided by expected 

lifetime energy output, with appropriate adjustments for such factors as time value of money. 

The overall cost goals for the SAI TPP projects are 

shown in Table 1. 

The SAI Photovoltaic Systems R&D Technology 

Pathway Partnerships (TPPs) program implements partnerships with U.S. industry for projects 

that focus on development, testing, demonstration, 

validation, and interconnection of new PV components, systems, and manufacturing equipment. 

These projects will yield new reduced-cost commercial products by the end of Phase 1 in 2010, 

and also are expected to initiate product and process development activities on a trajectory that will 

meet the SAI cost targets in 2015. 

2. Program/Technical Approach 

As noted, the TPP program is focused on developing new PV solutions for the residential, commercial, and utility market sectors of grid-tied electric 

power. These markets are described as follows. 

•	 Residential rooftop market. Equipment 

typically is mounted on rooftops and ranges in 

size from less than 1 kW to 10 kW, most 

commonly in the 3 kW to 4 kW range. These 

systems are connected to the grid on the retail 

(customer) side of the utility meter, and can be 

retrofitted onto existing homes or integrated 

into new construction through building-integrated PV (BIPV) designs. 

•	 Commercial rooftop market. Equipment 

typically is mounted on the large flat roofs of 

commercial, institutional, and industrial buildings, and ranges in size from less than 10 kW 

to 500 kW. Connected on the retail side of the 

utility meter. Retrofits and BIPV are possible 

applications in this market as well. 

•	 Utility market. Large-scale (multi-megawatt) 

systems that displace conventional utility 

generated intermediate load electricity (e.g., 

natural gas CCT plants) on a wholesale basis. 

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74
Utility PV systems typically are groundmounted and range in size from 1 MW to 

10 MW, although much larger systems currently are in development. Designs include 

both fixed and tracking configurations. 

To address these market goals, the following 

overall approach for the SAI TPP has been 

implemented. 

•	 SAI TPPs are industry-led. All technical details 

regarding approach, timelines, milestones, 

and system integration are formulated by 

applicants. The National Laboratories supports 

DOE in monitoring technical progress, conducting tests and evaluations, and directly 

supporting TPPs on specific R&D. 

•	 SAI TPPs are focused on near- and mid-term 

results. Accordingly, emphasis is on technologies with the greatest potential for cost-competitiveness in the period leading up to 2015. 

•	 SAI TPPs are focused on PV systems. The 

primary metric for SAI is LCOE, which is determined by the complete PV system rather than 

any component. Therefore, SAI is working 

towards novel integrated PV systems 

approaches. 

•	 SAI TPPs are partnership-oriented. Industry 

participants are strongly encouraged to formulate partnerships to address the spectrum of 

possible technical improvements in the PVsystem value chain. 

•	 SAI TPP is market-based. Goals are directly 

market-oriented in terms of cost, penetration, 

and job creation, and all technical objectives 

established through SAI directly impact these 

market-based goals. 

Each SAI TPP project is segmented into 3 manageable 3-year phases. These phases progressively reduce the cost of commercially-available 

PV systems and components, and ultimately yield 

commercial products and producion processes 

that achieve the LCOE and support installed capacity targets by 2015. The first 3-year phase is 

scheduled to run from calendar year (CY) 2007 

through CY 2010; the second 3-year phase is 

expected to run from CY 2010 through CY 2013; 

and the third 3-year phase is expected to run from 

CY 2013 through 2015. 

The three phases of technology development for 

the TPP programs are as follows: 

•	 Phase 1. Demonstrate pilot production of 

lower-cost systems. R&D Project Duration of 3 

years (2007–2009) that allows companies the 

flexibility to align projects with their targeted 

business model, technical capabilities, and 

product/process maturity. 

•	 Phase 2. Demonstrate replication of low-cost 

pilot production. Project duration of 3 years 

(2010–2012), with new entrants eligible. 

•	 Phase 3. Develop supply chain and distribution infrastructure. Reduce capital expenditure 

intensity of manufacturing scale-up through 

targeted investments in such areas as 

equipment/feedstock suppliers and distribution 

channels. 

The TPP partnerships are industry-led teams composed of one or more companies, universities, 

national laboratories, and non-governmental 

organizations. Team composition emphasizes a 

coordinated effort of diverse approaches that in 

combination mitigate the total project risk and 

maximize the potential project outcome. 

DOE has made 12 awards for both systems class 

and subsystems class projects defined as follows: 

• Systems-class projects (integrated systems) 

address multiple technology improvements in 

PV-system and PV-component design, 

integration, and installation. 

•	 Subsystems-class projects (componentbased) projects focus on fewer technology 

developments to improve PV systems. 

Both systems-class and subsystems-class projects will be required to demonstrate the benefits 

of a project on system-level LCOE and installed 

capacity. 

Systems-class awards are funded up to $10 million annually, and subsystems-class awards are 

funded up to $4 million annually. Total DOE funding available for systems-class awards is limited to 

$20 million through the 3-year project period. Total 

DOE funding available for subsystems-class 

awards is limited to $8 million throughout the 3­

year project period. Both classes of projects 

require that applicants share 50% of the total 

project costs. 

Awards have been made as cooperative agreements between the DOE and the recipient, with a 

maximum project period of 3 years, beginning in 

fiscal year (FY) 2007. The cooperative agreements are funded through (approximately) annual 

budget periods, each of which concludes with a 

Stage-Gate Review scheduled around major tech75

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nical milestone(s) or decision point(s). At the 

completion of each successive Stage-Gate 

Review, a determination for continuation of the 

Phase 1 TPP project into the next budget period 

will be made. 

2.1. Stage-Gate Reviews 

DOE requires the use of a stage-gate management approach in Solar America Initiative (SAI) 

Technology Pathway Partnership (TPP) Projects, 

to facilitate rigorous project management and to 

support the DOE’s continuous assessment of its 

investment in the partnerships. The DOE will use 

this process to make informed decisions regarding 

the strategic direction of the program in general 

and, more specifically, regarding the future of 

individual recipients. Each recipient has specified 

the types of data, deliverables, testing, evaluation, 

and reports that will be developed and be made 

available for stage-gate reviews. A schematic of 

the review process is provided in Figure 1. 

At its simplest, three steps are included in the 

stage gate-review: Obtaining and analyzing data, 

performing the review, and deciding on the next 

steps. At each gate review, deliverables must be 

provided as specified in the recipient-developed 

project plans. These deliverables demonstrate the 

ability of each recipient to meet the DOE LCOE 

cost targets for their technology. The LCOE values 

are dependent on system performance and 

manufacturing costs, therefore these quantities 

are evaluated independently (performance 

evaluated by NREL/Sandia, and cost evaluated by 

an independent contractor to DOE) to assure that 

they are sufficient to demonstrate the stage-gate 

criteria have been met. Recommendations made 

by the reviewers are documented and provided to 

the DOE Solar Program management. Ultimately, 

the four outcomes possible from a stage-gate 

review (Figure 1) are: Pass (to the next stage), 

Recycle/Redirect (stay in the same stage but 

complete additional necessary work), Hold (suspend DOE support for the project until additional 

data supports restarting or canceling), or Stop (no 

further DOE support for this project). A schedule 

for the TPP project stage gates is shown in Figure 

2 below. Blue-shaded blocks indicate times of test 

and evaluation activities leading to the stage-gate 

review. 

Figure 1. Stage-Gate Review 

Amonix 

C. Cameron 

Greenray 

Sig Gonzales 

Boeing 

Dan Friedman 

United Solar 

Brent Nelson 

Konarka 

T. Barnes 

BP Solar 

Harv Mahan 

Nanosolar 

David Young 

Sunpower 

John Benner 

Dow 

Bill Marion 

GE Energy 

M. Quintana 

Soliant 

Nathan Siegel 

TPP 

J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N 1/27 

9/1/07 

11/18 

9/1/07 

11/6 

8/1/07 

10/29 

9/1/07 

10/28 

9/1/07 

10/21 

9/1/07 

7/1/07 

9/4 8/19 

4/30/07 

7/1/07 

6/26 

1/1/07 

6/10 

2010 

5/14/07 

5/8 

Start 

date 

2008 2009 

Figure 2. TPP Stage-Gate Review Schedule 

2.2. TPP Project Management Approach 

Project monitoring and technical oversight are 

conducted over the course of Phase 1 by a team 

that includes personnel from the DOE Golden 

Field Office, through which SAI TPP cooperative 

agreements will be managed and administered; 

DOE Headquarters; the National Renewable 

Energy Laboratory; and Sandia National 

Laboratories. 

The basic management structure for TPP projects 

is depicted below (Figure 3). Individual responsibilities and authorities within this structure also are 

described below. 

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76
 

Program Manager/

Technology Manager

DOE HQ Solar Program

TPP Contact

Partner Lab/FFRDC

TPP Contact

Partner Company

TPP Contact

Partner University

Project Officer

DOE Golden Field Office

Principal Investigator

TPP Prime Recipient

TPP Support Contact

FFRDC Support Resource

Technical Monitor

NCPV Lab

Project Engineer

GO Support Contractor

Contracting Officer

DOE Golden Field Office

TPP Validation Contact

FFRDC T&E Support

Program Manager/ 

Technology Manager 

DOE HQ Solar Program 

TPP Contact 

Partner Lab/FFRDC 

TPP Contact 

Partner Company 

TPP Contact 

Partner University 

Project Officer 

DOE Golden Field Office 

Principal Investigator 

TPP Prime Recipient 

TPP Support Contact 

FFRDC Support Resource 

Technical Monitor 

NCPV Lab 

Project Engineer 

GO Support Contractor 

Contracting Officer 

DOE Golden Field Office 

TPP Validation Contact 

FFRDC T&E Support 

Figure 3. SAI TPP Project Management 

Structure 

Notably, for each TPP recipient, this management 

approach utilizes a technical monitor that is 

cognizant of the technology being developed. 

Technical monitors have been assigned from one 

of the NCPV National Laboratories (NREL or 

Sandia). Assignments have been made based on 

the alignment between the skills and experiences 

of lab personnel and the R&D activities of the TPP 

project. The technical monitor assists the project 

officers in overseeing and assessing the progress 

of TPP projects. In this capacity, they are available 

to provide technical assistance and guidance, 

facilitate interactions with experts as needed, and 

assure timely access to DOE-funded laboratory 

resources as they are required for project implementation (e.g., test facilities). The technical 

monitor provides the project officer with technical 

evaluations and reports supporting stage-gate 

reviews; evaluates quarterly reports on progress 

against milestones, go/no go decision points, and 

critical success factors; and makes recommendations with respect to stage-gate decisions. 

2.3. TPP Program Recipients 

A summary of the TPP program recipients is 

included below. A short description of the activities 

encompassed for each recipient is as follows. 

• Amonix 

Total Award Amount: $33,635,272 

DOE Share $15,605,631 

Recipient Cost Share $18,029,642 

The objective of the Amonix project is to 

transition its concentrating photovoltaics 

technology to high-volume production to meet 

market demand and price. The main focus will 

be to develop the high-volume tooling, processes, robotic machines, etc. necessary to 

achieve high -volume production and low labor 

costs. Amonix’s manufacturing steps, having 

already been well-defined by previous manufacturing experience, need to be transitioned 

to automation. These new processes and 

machines will be integrated into a pilot factory 

to verify their performances. The pilot factory 

will be used to manufacture 25-kW and 35-kW 

systems, incorporating both silicon and multijunction solar cells. 

•	 The Boeing Company 

Total Award Amount: $45,314,582 

DOE Share $19,980,504 

Recipient Cost Share $25,334,078 

The Boeing Company program, “High 

Efficiency Concentrating Photovoltaic Power 

Systems,” will draw on previously developed 

state-of-the-art multijunction solar cell technology used in concentrator photovoltaic systems to provide lower system costs. 

•	 BP Solar Inc 

Total Award Amount: $39,693,369 

DOE Share $19,431,635 

Recipient Cost Share $20,261,734 

BP Solar’s project is based on accelerated 

development of multicrystalline silicon technology for use in the residential and commercial markets. The program goals are to 

achieve grid parity and increased production 

volume. The BP Solar Program addresses all 

aspects of the PV product chain from raw 

materials, including silicon, through installation 

of the systems at the customer site. A key 

component of the program is the development 

of multi-crystalline Si with single-crystal quality, and thinner wafers for better material 

utilization. Lower system costs and reliability 

also will be developed under the program. 

•	 Dow Chemical Company 

Total Award Amount: $19,648,607 

DOE Share $9,824,303 

Recipient Cost Share $9,824,304 

The Dow Chemical Company, together with 

residential and commercial builders, will 

develop building integrated photovoltaic 

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roofing products specifically optimized for realworld conditions. Dow Chemical will design, 

engineer, and develop innovative PV–packaging solutions for building integrated applications. These will include residential shingles, 

slates, and tiles as well as commercial roll 

roofing and standing metal rib roofing. Design 

application packages for all of the PV technologies will enable low-cost, high-reliability 

installation. The PV package development will 

create designs that drastically simplify the 

installation of PV systems. This will include the 

PV-module installation itself, interconnect 

systems, and all the durability and weatherresistance issues necessary for a reliable 

long-life system. 

•	 GE Global Research 

Total Award Amount: $46,217,121 

DOE Share $19,999,991 

Recipient Cost Share $26,217,130 

GE has assembled a team of industrial 

partners that will create an unbroken value 

chain from the raw materials to the customer’s 

rooftop. By 2010, GE and its partners will be 

positioned to deliver more than 200 MW of 

GE-branded products into the residential and 

commercial segments of the U.S. market. The 

team will pursue various technical pathways 

including a mono-crystalline silicon pathway 

that incorporates a high-efficiency bifacial 

solar cell, and a thin-film pathway that takes 

advantage of new GE materials technology to 

produce a 25-year flexible module for building 

integration. 

• GreenRay Inc 

Total Award Amount: $5,043,503 

DOE Share $2,521,751 

Recipient Cost Share $2,521,752 

GreenRay, Inc. will develop an AC-module 

system. The AC module will have a superior 

life span and will produce lower-cost energy 

for customers. The simplified design and 

installation requirements will bring photovoltaic 

technology to a broader class of installers. At 

the heart of the AC-module system is a gridtied micro-inverter with the potential to achieve 

a 30-year lifetime, optimally sized to operate 

with a high-powered, ultrahigh-efficiency 

photovoltaic module. The micro-inverter will 

have a small physical size allowing it to be 

factory-integrated into the frame of the 

module. Each AC-module system will have 

wireless communication capability enabling it 

to report its performance to a central display 

for the homeowner. 

•	 Konarka Technologies Inc. 

Total Award Amount: $8,584,841 

DOE Share $3,655,491 

Recipient Cost Share $4,929,350 

The Konarka Technologies Inc. program will 

address technical challenges that prevent the 

use of organic polymer-based photovoltaic 

(PV) modules on rooftop applications. The first 

objective is to develop new barriers to prevent 

water and oxygen from entering a cell and 

impeding cell function. The second is to raise 

module performance to a required output level 

(W/m2) for commercial rooftop applications. 

Konarka’s manufacturing process uses continuous roll-to-roll printing or coating equipment 

to produce lightweight, flexible modules using 

small quantities of inexpensive materials. This 

approach offers the potential for producing a 

low-cost ($/W) solar material that, due to its 

weight and flexibility, is easier to integrate into 

roofing material and other products. 

• Miasolé Inc. 

Total Award Amount: Not awarded 

DOE Share: Not awarded 

Recipient Cost Share: 

Miasolé will significantly reduce the cost of PV 

by bringing high-volume manufacturing technology to the production of thin-film solar cells, 

and introducing flexible PV modules with integrated electronics. Miasolé already has an 

operational 25-MW solar-cell production 

system and a second is near completion. 

These systems utilize all sputtered, roll-to roll 

deposition technology combined with roll-toroll lamination technology for module 

assembly. The resulting modules are large, 

lightweight, and flexible for building integrated 

solar-cell applications. The program includes 

the incorporation of AC inverters and moduleembedded semiconductor technology. 

Photovoltaic R&D

Advanced Materials and Devices

Systems Development

78
• Nanosolar Inc. 

Total Award Amount: $42,616,356 

DOE Share $19,991,101 

Recipient Cost Share $22,625,255 

Nanosolar has developed a new generation of 

solar-cell technology—the industry’s first backcontacted thin-film cell as well as the world’s 

most-efficient cell produced with printed semiconductors. The target market for the PV 

system developed through this project is flatand low-sloped commercial rooftops with total 

installed capacity greater than 100 kW. The 

program focus will be on the retrofit market 

with aggressive cost-reduction goals that 

benefit a wide range of users. The project 

team will bring together innovations in cell and 

module technology, inverter technology and 

systems optimization, and module-mounting 

technology to deliver a pilot installation with 

grid-parity customer economics. 

•	 Soliant Energy Inc. 

Total Award Amount: $13,659,722 

DOE Share $4,886,762 

Recipient Cost Share $8,772,960 

The Soliant Energy program will develop and 

evaluate pilot installations of advanced concentrating solar panels for commercial rooftop 

applications. The 2010 direct-cost goal is 

$1.25/W with array efficiency of 28%. The 

panels have self-powered integrated-tracking 

to make them drop-in alternatives for conventional modules. This breakthrough technology 

enables more solar power on a rooftop than 

any other solution without the need to modify 

standard installation practices. Additionally, 

the concentrating panel’s production cost is 

projected to be a fraction of the cost of conventional technology. 

• Sunpower Corporation 

Total Award Amount: $52,647,068 

DOE Share $24,700,000 

Recipient Cost Share $27,947,068 

SunPower, a manufacturer of high-efficiency 

silicon solar cells and modules, proposes to 

build an innovative network for efficient downstream distribution. The near-term focus will 

be achieving grid parity in the residential 

market, and achieving the LCOE targets in the 

utility market will be a longer-range objective. 

PowerLight is SunPower’s subsidiary and has 

been selected for a separate but related TPP 

project activity related to solar-cell development. The two selections have been integrated into a single project. 

•	 United Solar Ovonic LLC 

Total Award Amount: $39,848,561 

DOE Share $19,339,034 

Recipient Cost Share $20,509,527 

United Solar Ovonic is a manufacturer of thinfilm amorphous silicon alloy based photovoltaic products. The company uses a proprietary roll-to-roll manufacturing process and the 

product is flexible, lightweight, aesthetically 

pleasing, and suited for building integrated 

(BIPV) applications. A two-pronged approach 

to achieving Levelized Cost of Energy goals is 

proposed: (1) to improve the efficiency of the 

solar cell; and (2) to reduce the cost of major 

module components. 

3. Results and Accomplishments 

3.1. Project Selection 

•	 Applications were received by the Golden 

Field Office in response to the SAI TPP Funding Opportunity Announcement. 

•	 Twelve applications were chosen for negotiation, based on various program factors. 

3.2. DOE Program Review 

•	 A DOE program review showcasing the anticipated activities of the SAI TPP recipients was 

held in Denver, Colorado. (See “Major FY 

2007 Publications” (below) for a presentation 

reference.) 

3.3. Project Kickoff Meetings 

•	 Following completion of the SAI TPP awards, 

kickoff meeting were held (see Table 2 below) 

at each recipients facility, to review the technology baseline and the plans for reaching the 

first scheduled stage gate. 

4. Planned FY 2008 Activities 

4.1. Stage Gates 

•	 Stage Gates anticipated for FY 2008 are 

shown in Figure 2 (above). 

79

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Systems Development
 

4.2. Critical Milestone 

•	 Nanosolar Inc. critical milestone criteria is to 

deliver a commercial-size cell and module with 

solar conversion efficiency that is greater than 

6% and 4.5% respectively. The milestone will 

be verified by NREL (3/08). 

5. Major FY 2007 Publications 

•	 Solar Program Peer Review Agenda Overview 

(April 2007). 

•	 “Overview of Solar America Initiative Awards,” 

Project Announcements on Technology Pathway Partnerships, 8 Mar. 2007. 

Copies of the publications can be found at http:// 

www.energy.gov/public. 

Table 2. TPP Award Recipients 

SAI TPP Recipient 

FY 2007 

Obligation Award Date Start Date 

Project Kickoff 

Date 

Amonix Inc. $2,200,000 30 July 2007 14 May 2007 24 Oct. 2007 

The Boeing Co. $3,400,000 30 July 2007 1 July 2007 28 Sept. 2007 

BP Solar Inc. $4,000,000 31 July 2007 1 Sept. 2007 18 Sept. 2007 

Dow Chemical Co. $1,600,000 30 July 2007 1 Aug. 2007 29 Sept. 2007 

GE Global Research .Inc. $4,600,000 30 July 2007 1 Sept. 2007 19 Sept. 2007 

Greenray Inc. $591,353 3 July 2007 1 Jan. 2007 12 Sept. 2007 

Konarka Technology Inc. $868,805 1 Aug. 2007 1 July 2007 11 Oct. 2007 

Miasolé Inc. $3,000,000 30 July 2007 1 Sept. 2007 — 

Nanosolar Inc. $4,750,105 23 Aug. 2007 1 Sept. 2007 25 Oct. 2007 

Soliant Energy Inc. $2,098,991 31 July 2007 1 Sept. 2007 23 Oct. 2007 

Sunpower Corp. $4,400,000 20 Aug. 2007 1 Sept. 2007 2 Oct. 2007 

United Solar Ovonics LLC $2,821,859 30 July 2007 30 Apr. 2007 30 Sept. 2007 

6. University and Industry Partners 

The following organizations partnered in the TPP program research activities during FY 2007. 

Recipient and 

Sub-Recipients Location 

Title of Research Activity 

and Principal 

Investigator Information 

FY 2007 

($K) 

Cost Share 

($K) 

Amonix, Inc. 

University of Las Vegas 

Spectralab Inc. 

Cryo Industries 

Arizona State University 

NREL 

Xantrex Technologies Inc. 

Imperial Irrigation District 

Torrance, CA 

Las Vegas, NV 

Sylmar, CA 

Sanford, ME 

Tempe, AZ 

Golden, CO 

Burnaby, BC, 

Canada 

Imperial, CA 

“Low Cost, High 

Concentration Photovoltaic 

Systems for Utility Power 

Generation” 

Bob McConnell 

310-325-8091 x18 

3,234,471 9,836,219 

The Boeing Company 

PV Powered Inc 

Sylarus Technologies. LLC 

Southern California Edison 

NREL 

Light Prescriptions 

Innovators 

Array Technologies 

California Institute of 

Technology 

Huntington Beach, CA 

Bend, OR 

Columbus, OH 

Monterey Park, CA 

Golden, CO 

Altadena, CA 

Albuquerque, NM 

Pasadena, CA 

“High Efficiency Concentrating Photovoltaic 

Power System” 

Russ Jones 

Russ.jones@boeing.com 

714-206-2556 

8,136,637 11,538,846 

Photovoltaic R&D

Advanced Materials and Devices

Systems Development

80
 

Recipient and 

Sub-Recipients Location 

Title of Research Activity 

and Principal 

Investigator Information 

FY 2007 

($K) 

Cost Share 

($K) 

BP Solar Inc. 

Arizona State University 

Bekaert Corp. 

Dow Corning Corp. 

Georgia Institute of 

Technology 

Ceradyne Thermo Materials 

Palo Alto Research Center 

ATS Ohio, Inc 

Ferro Corp. 

Recticle UREPP N. America 

SMUD 

University of Central Florida 

Xantrex Technology Inc. 

Fat Spaniel Technologies 

Inc. 

Specialized Technology 

Resources Inc. 

AFG Industries 

Komax Systems, York 

Frederick, MD 

Tempe, AZ 

Marietta, GA 

Midland, MI 

Atlanta, GA 

Clarkson, GA 

Palo Alto, CA 

Lewis Center, OH 

Cleveland, OH 

Clarkson, MI 

Sacramento, CA 

Orlando, FL 

Burnaby, BC 

Canada 

San Jose, CA 

Enfield, CT 

Kingston, TN 

York, PA 

“Reaching Grid Parity 

Using BP Solar Crystalline 

Silicon Technology A 

Systems Class Application” 

John Wohlgemuth 

John.wohlgemuth@bp.com 

301-698-4375 

7,029,635 7,099,255 

Dow Chemical Company 

Miasolé Inc. 

Solfocus Inc. 

University of Delaware 

Fronius USA, LLC 

IBIS Associates 

Midland, MI 

Santa Clara, CA 

Palo Alto, CA 

Newark, DE 

Brighton, MI 

Waltham, MA 

“Fully Integrated Building 

Science Solutions for Residential and Commercial 

Photovoltaic Energy 

Generation” 

Bob Cleereman 

RJCleereman@dow.com 

989-636-5425 

2,841,296 2,841,296 

GE Global Research LLC 

GE Energy Inc./Energy 

Power Generation 

REC Silicon Inc. 

Solaicx Inc. 

Xantrex Technologies Inc. 

University of Delaware 

Georgia Tech Research 

Institute 

Niskayuna, NY 

Newark, DE 

Moses Lake, WA 

Santa Clara, CA 

Burnaby, BC, 

Canada 

Newark, DE 

Atlanta, GA 

“A Value Chain Partnership 

to Accelerate U.S. PV 

Industry Growth” 

Danielle Merfeld 

merfeldw@research.ge.co 

m 

518-387-4252 

9,949,710 13,062,461 

Greenray Inc. 

Coal Creek Design Inc. 

Bluepoint Associates 

NREL 

Sandia National Laboratory 

Sanyo Energy USA Corp. 

Lincoln, MA 

Lafayette, CO 

San Luis Obispo, 

CA 

Golden, CO 

Albuquerque, NM 

Frisco, TX 

“Development of an AC 

Module System” 

Miles Russell 

Miles.russell@gmail.com 

781-962-9878 

591,353 591,353 

Konarka Technologies Inc. 

University of Delaware 

NREL 

Lowell, MA 

Newark, DE 

Golden, CO 

“Low Cost, Lightweight 

Solar Modules Based on 

Organic Photovoltaic 

Technology” 

Russ Gaudiana 

rgaudiana@konarka.com 

978-569-1410 

868,805 1,847,999 

Miasolé Inc. 

University of Delaware 

Carlisle Syntec Inc. 

University of Colorado 

Exeltech Inc. 

Sandia National Laboratory 

NREL 

Santa Clara, CA 

Newark, DE 

Carlisle, PA 

Boulder, CO 

Ft. Worth, TX 

Albuquerque, NM 

Golden, CO 

“Flexible Integrated PV 

System” 

Tom Hecht 

thecht@miasole.com 

408-919-5718 

Not 

Awarded 

Not 

Awarded 

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Systems Development
 

Recipient and 

Sub-Recipients Location 

Title of Research Activity 

and Principal 

Investigator Information 

FY 2007 

($K) 

Cost Share 

($K) 

Nanosolar Inc. San Jose, CA “Delivering Grid-Parity 4,750,105 5,073,118 

Suntechnics Energy Sacramento, CA Solar Electricity on Flat 

Systems Inc. Commercial Rooftops” 

Sunlink, LLC Larkspur, CA 

Conergy Inc. Santa Fe, NM Brian Sager 

bsager@nanosolar.com 

408-365-5965 

Soliant Energy Inc. 

Spectralab Inc. 

MIT 

Sandia National Laboratory 

Pasadena, CA 

Sylmar, CA 

Cambridge, MA 

Albuquerque, NM 

“Concentrating Solar 

Panels: Bringing the 

Highest Power and Lowest 

Cost to the Rooftop” 

Brad Hines 

Brad.hines@soliantenergy.com 

626-389-1101 

2,098,991 2,557,186 

Sunpower Inc. 

Dow Corning Corp. 

Massachusetts Institute of 

Technology 

Xantrex Technologies Inc. 

Solaicx Inc. 

NREL 

Specialized Technology 

Resources Inc. 

Silicon Genesis Corp. 

New Power Technologies 

San Jose, CA 

Midland, MI 

Cambridge, MA 

Burnaby, BC, 

Canada 

Santa Clara, CA 

Golden, CO 

Enfield, CT 

San Jose, CA 

“Grid-Competitive Residential and Commercial Fully 

Automated PV Systems 

Technology” 

Terry Jester 

terry.jester@ 

sunpowercorp.com 

408-218-0884 

8,469,998 8,469,998 

United Solar Ovonic LLC 

Energy Conversion Devices 

Inc. 

Syracuse University 

Colorado School of Mines 

University of Oregon 

NREL 

PV Powered Inc. 

Solectria Renewables LLC 

DEERS 

Satcon Technology Corp. 

Sun Edison 

SMA America Inc. 

Auburn Hills, MI 

Richmond Hills, MI 

Syracuse, NY 

Golden, CO 

Eugene, OR 

Golden, CO 

Bend, OR 

Lawrence, MA 

Ripon, CA 

Boston, MA 

Baltimore, MD 

Grass Valley, CA 

“Low Cost Thin-Film 

Building-Integrated PV 

Systems” 

Subhendu Guha 

sguha@uni-solar.com 

248-364-5707 

4,424,948 4,675,356 

Photovoltaic R&D

Advanced Materials and Devices

Systems Development

82
 

 

 

____________________________________________________________________________________ 

 

 

Component Development 

PV Manufacturing R&D 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Richard Mitchell (NREL), 303-384-6479, richard_mitchell@nrel.gov 

DOE HQ Technology Manager: Jeffrey Mazer, 202-586-2455, jeffrey.mazer@ee.doe.gov 

FY 2007 Budget: $8,711K (NREL) 

Objectives 

•	 Improving photovoltaic (PV) manufacturing processes and products for terrestrial applications 

•	 Accelerating PV manufacturing cost reductions 

•	 Increasing commercial product performance and reliability 

•	 Laying the foundation for significantly increased production capacity 

•	 Achieving these goals in an environmentally safe manner. 

Accomplishments 

•	 Completed reviews, required redirections, and renewals for the Large-Scale Module and 

Component Yield, Durability, and Reliability (YDR) project subcontracts. 

•	 Evaluated the scope of subcontracted research under the Large-Scale Module and Component 

Yield, Durability, and Reliability solicitation through identifying Solar America Initiative (SAI) 

Technology Pathway Partnership awards and successfully transferred research efforts under the 

Photovoltaic Manufacturing Research and Development (PVMR&D) project into the SAI 

Technology Pathway Partnership Funding Opportunity Announcement (FOA) through termination 

of five PVMR&D subcontracts. 

•	 Successfully transitioned the research of five of the PVMR&D YDR subcontracts to support 

Technology Pathway Partnership research through early subcontract terminations. 

•	 As part of the annual DOE Solar Energy Technologies Program (SETP) Review, conducted a 

stage-gate evaluation of U.S. industry participants in the PVMR&D Project to assess and 

determine the needs for additional manufacturing R&D and select areas for elimination or 

support. 

•	 Spire – Designed an automated stringing system for back contact solar cells and transferred the 

long-pulse simulator technology to market. 

•	 BP Solar – Demonstrated the feasibility of Mono2 technology, verified the expected efficiency 

gain, and reduced wafer thickness to 200 microns in production. 

•	 Dow Corning – Designed and began development of a pilot-scale, protection-system production 

line, including identification, acquisition, and installation of tooling. 

•	 Evergreen Solar – Demonstrated equipment for in situ laser cutting and wafer removal and ran 

five such machines continuously in a pilot line production. 

•	 First Solar – Improved thin-film CdTe module efficiency by 1.5 efficiency points. 

•	 GE Energy – Developed a metal wrap-through process for GE solar cell manufacturing and 

competed a highly accelerated lifetime testing capability for elements of roof-integrated modules. 

•	 PowerLight – Modified manufacturing and shipping processes to accommodate design changes, 

streamline material flow, reduce cost, and decrease waste streams. 

•	 Schott Solar – Demonstrated a prototype backplane interconnect process leading to prototype 

construct for laying back-contact cells on flexible copper patterned substrate. 

•	 Shingleton Design – Developed a new structural design with emphasis on factory-based 

assembly, modular design, and rapid deployment, resulting in a first-generation platform with the 

potential for 5%–10% increased energy production at a 5%–6% cost reduction. 

•	 SolarWorld – Increased the wire sawing yield to 2.78, a 25% improvement. 

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____________________________________________________________________________________ 

 

 

•	 SunPower – Improved the performance of a newly introduced magnetic-induction soldering 

process by reducing the heat zone while maintaining solder bond quality with a new coil design. 

•	 Xantrex Technology – Updated product functional specification and design to insure that the 500­

kW inverter product offering remains aligned with current market requirements, and successfully 

tested short circuit at full rated current. 

Future Directions 

•	 Complete stage-gate review of individual progress versus milestones and required redirection for 

YDR subcontracts. 

•	 Complete research subcontracts awarded under the Large-Scale Module and Component Yield, 

Durability, and Reliability procurement. 

•	 Complete all remaining research under the PVMR&D Project. 

1. Introduction 

The PV Manufacturing R&D Project was designed 

to assist the U.S. photovoltaic industry through a 

cost-shared manufacturing R&D partnership with 

the U.S. Department of Energy (DOE) and 

members of the U.S. PV industry. Subcontracted 

research has focused on the U.S. PV industry’s 

improvement of processes and products, resulting 

in (1) a substantial reduction in associated 

manufacturing costs; (2) a technology foundation 

that supports significant manufacturing scale-up 

(500 MW total U.S. capacity); and (3) positioning 

the industry to meet rapidly emerging large-scale 

deployment opportunities. This focus has directly 

supported the DOE Solar Energy Technologies 

Program’s Advanced Materials and Devices 

activities. 

Each subcontractor has enhanced existing 

manufacturing technologies through cost-shared 

development efforts geared toward achieving the 

overriding PVMR&D goals. Work areas have 

included (1) the improvement of module 

manufacturing processes to increase module 

reliability; (2) system and system-component 

packaging, system integration, manufacturing, and 

assembly; (3) product manufacturing flexibility; 

and (4) balance-of-systems (BOS) development, 

including storage and quality control. 

2. Technical Approach 

The PVMR&D Project is a government/industry 

partnership through cost-shared, subcontracted 

research in PV manufacturing technologies. The 

approach for the FY 2007 work effort was divided 

into three areas: (1) Project Management and 

Support subtask activities; (2) research 

subcontracts under the FY 2001 competitive 

solicitation for In-Line Diagnostics and Intelligent 

Processing in Manufacturing Scale-Up (IDIP); and 

(3) research subcontracts under the FY 2003 

competitive solicitation for Large-Scale Module 

and Component Yield, Durability, and Reliability, 

or YDR. 

During FY 2007, the focus of the PVMR&D Project 

was redirected to support the Technology Pathway 

Partnership Funding Opportunity Agreement under 

the Solar America Initiative. As such, many of the 

subcontracted research activities under the YDR 

procurement were terminated early in order to 

transfer their research focus to newly awarded 

Technology Pathway Partnership research. 

2.1 PV Manufacturing R&D Management 

The Project Management and Support subtask 

addresses (1) management of the PVMR&D 

project; (2) management of subcontracts awarded 

under the IDIP and YDR procurements; and (3) 

coordination of NREL’s in-house activities in 

support of PVMR&D industrial partners. 

Table 1. PVMR&D Project Tasks and Budget 

Task Title FY 2007 

Budget ($K) 

PV Manufacturing R&D Technical 

Coordination 542 

In-Line Diagnostics and Intelligent 

Processing 

217 

Module Yield, Durability, and 

Reliability 7,952 

2.2 In-Line Diagnostics and Intelligent Processing 

The IDIP subtask consisted of the last remaining 

FY 2007 cost-shared PVMR&D subcontract with 

Spire Corporation, “Development of Automated 

Production Line Processes for Solar Brightfield 

Modules,” which was awarded under the FY 2001 

IDIP competitive solicitation. This solicitation was 

directed toward the improvement of module 

manufacturing processes; system and system 

Photovoltaic R&D

Advanced Materials and Devices

Component Development

84
 

 

component packaging, system integration, 

manufacturing, and assembly; product 

manufacturing flexibility; and BOS development. 

This subcontract emphasized new and improved 

in-line diagnostics and monitoring with real-time 

feedback for optimal process control and 

increased yield in the fabrication of PV modules, 

systems, and other system components. 

2.3 Yield, Durability, and Reliability 

The FY 2007 YDR subtask comprises the costshared PVMR&D subcontracts in Table 2 resulting 

from a competitive solicitation in FY 2003. The 

focus is on improving module manufacturing 

processes to increase module reliability, system 

and system-component packaging, system 

integration, manufacturing, and assembly; product 

manufacturing flexibility; and BOS development, 

including storage and quality control. The 

emphasis is on enhancing the reliability of the 

module, system components, and the complete 

system. Note that many of the subcontracts under 

this subtask were terminated early; therefore, the 

funding originally under this subtask was made 

available for use in the SAI Technology Pathway 

Partnership projects. 

Table 2. FY 2007 YDR Subcontractors 

Subcontractor Title of Subcontract 

BP Solar 

Development of Large High-Voltage 

PV Modules with Improved Reliability 

and Lower Cost 

Dow Corning 

Corporation 

High Performance Packaging 

Solutions for Low Cost, Reliable PV 

Modules 

Evergreen 

Solar 

Low-Cost Manufacturing of HighEfficiency, High-Reliability String 

Ribbon Si PV Modules 

First Solar 

Implementation of Reliable 

Manufacturing of Higher Efficiency 

Module 

GE Energy Solar Cell Design for Manufacturability 

PowerLight 

Corporation 

Accelerating PV Cost Effectiveness 

Through Systems Design, 

Engineering, and Quality Assurance 

SCHOTT Solar 

Subcontracts under PV Module And 

Component Yield, Durability, And 

Reliability solicitation 

Shingleton 

One-Axis Trackers – Improved 

Reliability, Durability, Performance, 

and Cost Reduction 

SolarWorld Manufacturing Improvements in CZ 

Silicon Module Production 

SunPower Automated Manufacturing of High 

Efficiency Modules 

Subcontractor Title of Subcontract 

Xantrex 

Advanced, High Reliability, System 

Integrated 500-kW Photovoltaic 

Inverter Development 

3. Results and Accomplishments 

3.1 In-Line Diagnostics and Intelligent Processing 

Under this subtask, the PVMR&D project focused 

on completing all but one of the IDIP subcontracts 

to a successful conclusion during the year. The 

significant achievements accomplished under this 

subtask by the remaining IDIP subcontractor, 

Spire Corporation, are described below. 

Spire Corporation 

“Development of Automated Production Line 

Processes for Solar Brightfield Modules” 

•	 Designed an automated stringing system for 

back contact solar cells 

•	 Designed and implemented a Supervisory 

Control and Data Acquisition (SCADA) system 

for photovoltaic module assembly 

•	 Transferred the long-pulse simulator technology 

to market. 

3.2 Yield, Durability and Reliability 

The Large-Scale Module and Component Yield, 

Durability, and Reliability letter of interest issued in 

FY 2003 focused on addressing needs in two 

categories. Category A, PV System and 

Component Technology, largely addresses the 

nonmodule aspects of PV systems component 

manufacturing processes. Category B, PV Module 

Manufacturing Technology, primarily addresses 

aspects of module manufacturing processes. 

Under this subtask, the significant achievements 

of individual subcontractors in FY 2007 are 

described below. 

BP Solar 

“Development of Large High-Voltage PV Modules 

with Improved Reliability and Lower Cost” 

•	 Demonstrated feasibility of Mono2 technology 

and verified the expected efficiency gain 

• Qualified and implemented (in production) a 

U.S. supply of antireflective (AR) coated glass 

•	 Reduced wafer thickness to 200 microns in 

production 

•	 Built and populated a high-voltage test bed at 

the Florida Solar Energy Center 

•	 This subcontract was terminated early as a 

PVMR&D subcontract, and the work was 

successfully integrated into the BP Solar SAI 

Technology Pathway Partnership FOA. 

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Dow Corning Corporation 

“High Performance Packaging Solutions for LowCost, Reliable PV Modules” 

•	 Designed and began development of a pilotscale, protection-system production line, 

including identification, acquisition, and 

installation of tooling 

•	 Applied and characterized the protection system 

on multicrystalline silicon (Si) cells and strings, 

successfully passing the industry standard 

humidity-freeze cycle testing of 1,000 hours, 

85oC, 85% relative humidity, 200 TC, and 420 

hours UV/50 TC/10 

•	 Applied the optimized protection system to thinfilm PV devices and characterized them under 

humidity-freeze (HF) cycling; found that 

protection system effectiveness strongly 

depended on layer thickness; sufficiently thick 

layers were able to withstand HF cycling well. 

Evergreen Solar, Inc. 

“Low-Cost Manufacturing of High-Efficiency, HighReliability String Ribbon Si PV Modules” 

•	 Developed concept to address the buildup of 

impurities in Si melt, and allow the use of impure 

Si by periodically removing liquid from the melt 

during growth 

•	 Ran five quad machines on a continual basis in 

the pilot line; in some cases, a machine ran for a 

full 24 hours with no operator intervention at 

all—probably a first for silicon ribbon technology. 

•	 Designed a machine with a chamber containing 

a cutting laser and associated mechanical 

equipment to allow in situ wafer cuts to be 

grasped and placed in a plastic box. Five such 

machines were built and placed in a pilot line to 

be run continuously. 

First Solar 

“Solar Cell Design for Manufacturability” 

• Improved thin-film CdTe module efficiency by 

1.5 efficiency points 

•	 The efficiency improvement resulted from 

research in these module fabrication processes: 

0.5% from the alternative front contact window 

(AFCW) substrate; 0.3% from post-deposition 

processing (PDP); 0.3% from initial optimization 

of PDP and vapor transport deposition (VTD) of 

AFCW and the interfacial layer; 0.2% from 

improvements to the wet spray process; and 

0.3% from additional optimization rounds of PDP 

and VTD processes. 

GE Energy, LLC 

“Solar Cell Design for Manufacturability” 

•	 Developed a metal wrap-through process for GE 

solar cell manufacturing 

•	 Competed highly accelerated lifetime testing 

capability for elements of roof-integrated 

modules 

•	 Developed an improved diffusion process 

resulting in a near-ideal blue response at 

moderately low emitter sheet resistance of 50 to 

60 ohms per square 

•	 This subcontract was terminated early as a 

PVMR&D subcontract, and the work was 

successfully integrated into the GE Energy SAI 

Technology Pathway Partnership FOA. 

PowerLight Corporation 

“Accelerating PV Cost Effectiveness Through 

Systems Design, Engineering, and Quality 

Assurance” 

•	 Implemented design improvements with the goal 

of reducing costs while maintaining and/or 

improving product quality 

•	 Modified manufacturing and shipping processes 

to accommodate design changes, streamline 

material flow, reduce cost, and decrease waste 

streams. 

Schott Solar, Inc. 

“High Performance Multicrystalline Silicon 

Modules and Products” 

•	 Demonstrated prototype backplane interconnect 

process; optimized materials and process, 

leading to prototype construct for laying backcontact cells on flexible backplane substrate 

containing patterned copper substrate 

•	 Examined approaches for improving potential 

cell efficiency in Si wafers from edge-defined, 

film-fed growth process through cell design or 

process modifications. Identified changing the ptype dopant source during crystal growth from 

boron to gallium as especially promising, with 

resulting cell efficiencies as high as 16.2% 

•	 This subcontract was terminated as a PVMR&D 

subcontract at the direction of DOE as part of its 

overall realignment of research under the SAI. 

Shingleton Design 

“Advanced, High Reliability, System Integrated 

500-kW Photovoltaic Inverter Development” 

•	 Completed the development of the new 

structural design with emphasis on factorybased assembly, modular design, and rapid 

deployment 

Photovoltaic R&D

Advanced Materials and Devices

Component Development

86
 

 

 

 

 

 

 

•	 Improved the controller and drive subassemblies 

for further improved tracker performance 

•	 Completed the development of design and cost 

analysis tools enabling commercialization of a 

next-generation tracker 

•	 Demonstrated first-generation platform potential 

for 5%–10% increased energy production at a 

5%–6% cost reduction 

•	 This subcontract was terminated early as a 

PVMR&D subcontract, and the work was 

successfully integrated into the SunPower SAI 

Technology Pathway Partnership FOA. 

SolarWorld Industries America 

“Manufacturing Improvements in CZ Silicon 

Module Production” 

•	 Implemented a new ethylene vinyl acetate 

material into production, allowing a 30% 

reduction in cycle time without sacrificing 

module reliability 

•	 Reduced the average wafer thickness from 280 

microns to 210 microns and the wire thickness 

from 140 microns to 120 microns 

• Increased the wire sawing yield by 25%. 

SunPower Corporation 

“Automated Manufacturing of High Efficiency 

Modules” 

•	 Introduced a modified tab shape change 

expected to improve electrical performance at 

no increase in cost; tested coupons with 

modified tab shape and found good performance 

after 900 temperature cycles 

•	 Improved the performance of a newly introduced 

magnetic-induction soldering process by 

reducing the heat zone while maintaining the 

solder bond quality with a new coil design; 

tooling automation control will benefit greatly 

from this change 

•	 Identified single-layer sol-gel AR glass coating 

as promising for further development; found 

advantages in antisoiling properties as well as in 

the (expected) gain in energy production 

•	 This subcontract was terminated early as a 

PVMR&D subcontract, and the work was 

successfully integrated into the SunPower SAI 

Technology Pathway Partnership FOA. 

Xantrex Technology 

“Advanced, High Reliability, System Integrated 

500-kW Photovoltaic Inverter Development” 

•	 Updated the product functional specification and 

design to insure that the 500-kW inverter 

product offering remains aligned with current 

market requirements 

•	 Fabricated all critical subassemblies and 

magnetic components required to begin design 

verification testing 

•	 Completed the design of the inverter packaging 

and enclosure 

•	 Successfully tested the 500-kW inverter into a 

short circuit at full rated current. 

4. Planned FY 2008 Activities 

PVMR&D project procurements were framed to 

specifically address milestones under the SETP. 

The focus of this project has now been directed 

toward supporting the Technology Pathway 

Partnership FOA under the Solar America 

Initiative. As such, many subcontracted research 

activities under the YDR procurement were 

terminated early in order to transfer the focus of 

industrial subcontractors to newly awarded 

Technology Pathway Partnership research. The 

remaining YDR subcontracts will continue their 

efforts to enhance field reliability and durability as 

well as manufacturing yield. The major task 

milestone and expected accomplishment of this 

project during FY 2008 will be to complete 

research under the Large-Scale Module and 

Component Yield, Durability, and Reliability 

procurement during this year. 

The research addressed by the PVMR&D project 

has been selected by participants from the U.S. 

PV industry, in the form of proposals received in 

response to competitive solicitations. As such, 

these are systems-driven issues and are those of 

the greatest importance to individual PV 

manufacturers. Actual projects have been chosen 

primarily by evaluators external to the government 

using criteria constructed to select, in a 

technology-neutral manner, activities that are most 

likely to contribute to the PVMR&D project goals 

and objectives. 

Subcontracts under this project continue to assist 

in reducing PV system costs and improving PV 

manufacturing processes and products. In 

addition, representatives of the PV industry have 

identified this project as one of the most, if not the 

most, important and successful projects in the 

DOE SETP to date. 

5. Major FY 2006 Publications 

J. Shingleton, “One-Axis Trackers – Improved 

Reliability, Durability, Performance, and Cost 

Reduction,” Final Subcontract Technical Status 

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Report, SR-520-42769, 2 May 2006–31 August T.L. Jester, “Manufacturing Improvements in Cz 

(2007). Silicon Module Production,” Annual Subcontract 

Report, SR-520-42418, July 2005–October 2006 

T. Ellison, “Implementation of a Comprehensive (2006). 

On-Line Closed-Loop Diagnostic System for Rollto-Roll Amorphous Silicon Solar Cell Production,” J. Botkin, “Accelerating PV Cost Effectiveness 

Final Subcontract Report, SR-520-41560, 23 April Through Systems Design, Engineering, and 

2003–30 September (2006). Quality Assurance,” Final Subcontract Report, SR520-42420, June (2007). 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title 

of Research Activity 

FY 

2007 

($K) 

Cost 

Share 

($K) 

Spire Corporation 

Michael Nowlan 

Bedford, MA 

mnowlan@spirecorp.com 

Development of Automated 

Production Line Processes for Solar 

Brightfield Modules 

217 211 

BP Solar International, Inc. 

John Wohlgemuth 

Frederick, MD 

john.wohlgemuth@bp.com 

Development of Large High-Voltage 

PV Modules with Improved Reliability 

and Lower Cost 

562 526 

Dow Corning Corporation 

Barry Ketola 

Midland, MI 

barry.ketola@dowcorning.com 

High Performance Packaging 

Solutions for Low Cost, Reliable PV 

Modules 

904 904 

Evergreen Solar, Inc. 

Jack Hanoka 

Marlboro, MA 

hanoka@evergreensolar.com 

Low-Cost Manufacturing of HighEfficiency, High-Reliability String 

Ribbon Si PV Modules 

1408 1935 

First Solar, LLC 

Greg Helyer 

Perrysburg, OH 

ghelyer@FIRSTSOLAR.COM 

Implementation of Reliable 

Manufacturing of Higher Efficiency 

Module 

1080 1085 

GE Energy, LLC 

James Rand 

Newark, DE 

im.rand@ps.ge.com Solar Cell Design for Manufacturability 554 579 

PowerLight Corporation 

Jonothan Botkin 

Berkeley, CA 

Jbotkin@powerlight.com 

Accelerating PV Cost Effectiveness 

Through Systems Design, 

Engineering, and Quality Assurance 

0 0 

SCHOTT Solar, Inc. 

Mark Rosenblum 

Billerica, MA 

mark.rosenblum@us.schott.com 

High Performance Multicrystalline 

Silicon Modules and Products 335 324 

Shingleton Design, LLC 

Jefferson Shingleton 

Auburn, NY 

jefferson@shingleton.com 

One-Axis Trackers – Improved 

Reliability, Durability, Performance, 

and Cost Reduction 

273 597 

SolarWorld Industries America 

Theresa Jester 

Camarillo, CA 

Theresa.jester@shellsolar.com 

Manufacturing Improvements in CZ 

Silicon Module Production 975 1164 

SunPower Corporation 

Doug Rose 

Sunnyvale, CA 

Doug.Rose@sunpowercorp.com 

Automated Manufacturing of High 

Efficiency Modules 535 558 

Xantrex Technology, Inc. 

Raymond Hudson 

San Luis Obispo, CA 

Ray.Hudson@xantrex.com 

Advanced, High Reliability, System 

Integrated 500-kW Photovoltaic 

Inverter Development 

451 451 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Component Development 

Thin Film PV Partnership Program 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 DOE Golden Field Office (DOE/GO) 

Key Technical Contact: Harin S. Ullal (NREL), 303-384-6486, harin_ullal@nrel.gov 

DOE HQ Technology Manager: Jeffrey Mazer, 202-586-2455, jeffrey.mazer@ee.doe.gov 

FY 2007 Budget: $6,000K (NREL) 

Objectives 

•	 Support the Solar America Initiative Technology Partnership Pathway Funding Opportunity 

Announcement to achieve levelized cost of electricity by 2015. 

•	 Support the near-term transition to first-time manufacturing and commercial introduction of 

reliable thin-film amorphous silicon (a-Si), copper indium diselenide (CIS), cadmium telluride 

(CdTe), and film silicon modules. 

•	 Build a technology base upon which these advanced photovoltaic (PV) technologies can continue 

to be successful in improving manufacturing and can continue to progress in performance, 

reliability, and cost reductions, resulting in products that are able to compete in the PV 

marketplace. 

•	 Sustain innovation to support progress toward ambitious long-term PV cost and performance 

goals (e.g., 15% efficient modules costing less than $50/m2

 and capable of lasting 30 years), 

which are appropriate for cost-competitive PV-generated electricity. 

Accomplishments 

•	 Met one important OMB/DOE/EERE/SET Joule milestone. 

•	 U.S. manufacturing facilities expanded for two technology partners: First Solar, 120 MWp, and 

Uni-Solar, 90 MWp. 

•	 Production of thin films in the United States grew from about 10 MWp in 2003 to an estimated 

160 MWp in 2007. 

Future Directions 

•	 Continue to address key issues supporting the transition to a successful first-time manufacturing 

operation or a major production expansion in each thin-film area. 

•	 Significantly reduce CIS and CdTe layer thicknesses in cells and support the transfer of this 

advance to future manufacturing technologies. 

•	 Direct thin-film CdTe solar cell research to achieve a higher open-circuit voltage. 

•	 Investigate the use of nanocrystalline bottom cells in thin-film silicon multijunction solar cells. 

1. Introduction those goals. The partnership includes 

subcontracted research and development (R&D) 

Thin-film photovoltaic (PV) technologies are in CIS, CdTe, a-Si, and new thin films such as film 

considered to have good potential to meet silicon. The partnership members work closely 

ambitious cost and performance goals that are with NREL’s internal researchers, facilitating 

consistent with those of the Solar America collaborative activities with academia and U.S. 

Initiative (SAI) Technology Partnership Pathway, thin-film industry groups. 

e.g., to achieve long-term goals for a levelized 

cost of electricity by the year 2015. 2. Technical Approach 

The Thin Film PV Partnership Program is The partnership included about 20 subcontracts 

designed to accelerate progress toward meeting during FY 2007. Subcontract funding for FY 2007 

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for the Industry and University Thin Film PV Table 2. Estimated Worldwide Production 

Partnership is shown in Table 1. Capacity of Thin-Film PV Modules by 2010 

Table 1. Thin Film PV Partnership Funding 

Task Title FY 2007 

Budget ($K) 

Industry Thin Film 2,686 

University Thin Film 3,382 

Three groups were major technology partner 

subcontractors: Global Solar in CIS, First Solar in 

CdTe, and United Solar Ovonic (Uni-Solar) in a-Si. 

The rest were R&D partners and were either small 

businesses making progress in establishing pilot 

production operations or universities supporting 

partnership objectives. 

3. Results and Accomplishments 

The Thin Film PV Partnership supported the 

transition to successful first-time manufacturing of 

key thin-film technologies during FY 2007. This is 

our most important activity in the short term, 

because it will help establish thin films in the 

marketplace, improve their chances of future 

growth and success, and help define the transition 

to the private sector of technologies that have 

been successfully developed through U.S. 

Department of Energy (DOE) funding. 

This transition has been more than two decades in 

the making and is not yet accomplished. However, 

because of the substantial growth in CY 2007 to a 

total of more than 160 MW of U.S. production 

capacity (from only 12 MW in the United States in 

2003), thin films are now making this important 

transition. 

Surveys of the partnership’s technology partners 

indicated that this growth might increase 

substantially in CY 2008, to about 260 MW of 

annual U.S. production. If this happens, it will 

show that these key, potentially lower-cost 

technology options have arrived in the PV 

marketplace. It will also suggest the resumption of 

U.S. market leadership in PV, because thin films 

could take on a leading role in the future. 

Table 2 summarizes worldwide thin-film PV 

production capacity achievements by 2010. 

Estimated worldwide thin-film PV production 

capacity by that year could be approximately 4600 

MW. 

The following summaries describe some of the 

highlights of R&D in FY 2007. 

3.1 First Solar Expands to 120-MWp Factory 

First Solar aggressively expanded its 

manufacturing in 2007, with an installed capacity 

of 120 MW and expected sales of about 100 MW 

in that year. Also, First Solar’s worldwide 

production capacity is expected to be more than 

900 MW by December 2009, with projected sales 

of over 350 MW. This would place it among the 

top five PV companies in the world as well as the 

number one thin-film PV company. Figure 1 shows 

the progress that First Solar has made in module 

efficiency over the past several years. 

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Fig. 1. First Solar’s progress in module efficiency 

and in shipments from 2002 to 2007. 

Substantial progress has been made in terms of 

the following: 

•	 The new 120-MWp coater, which is now 

fabricating the majority of the company’s 

products 

•	 Reducing maintenance costs by substantially 

enhancing materials utilization rates 

•	 Automating and improving most aspects of 

production. 

First Solar planned to move to a cost structure that 

would allow $3/Wp ground-mounted PV systems 

to be installed in the not-too-distant future. 

The DOE Solar Energy Technologies Program, 

NREL, the National Center for Photovoltaics 

(NCPV), and the Thin Film PV Partnership have 

supported R&D in this very promising thin-film PV 

technology at First Solar for the past several 

years. First Solar uses a very rapid vapor transport 

deposition technique to deposit the semiconductor 

films in less than one minute, which gives it a 

significant advantage over its competitors. That 

deposition process won a prestigious R&D 100 

Award in 2003 that was shared by NREL. 

“These accomplishments strengthen the position 

of U.S. manufacturers as leaders in the next 

generation of thin-film solar technologies and 

accelerate our nation’s drive to make solar 

electricity competitive with conventional 

electricity,” said DOE Under Secretary David 

Garman. 

3.2 Uni-Solar Attains 90-MWp Capacity 

The Uni-Solar a-Si factory is working at full 

capacity, about 5 MWp/month. Because of the 

silicon shortage, module prices have been rising, 

and profitability is increasing. Recently, Uni-Solar 

built a third 30-MWp plant in Michigan, bringing 

the total manufacturing capacity to 90 MW. In 

describing the competitiveness of the Uni-Solar 

technology, company President Subhendu Guha 

made the case that the company’s peel-and-stick 

roofing material is directly competitive with all 

other rooftop PV approaches (including those 

using c-Si and CdTe) because installation is easy 

(reducing, e.g., balance of system costs) and 

because of its superior aesthetics and durability 

(see Figure 2). He mentioned two major “wins” 

over such competition to large commercial rooftop 

projects—one for 1 MW on a GM building and 

another for 750 kW in California. 

Fig. 2. The Uni-Solar a-Si factory produces peeland-stick thin-film PV roofing material, as shown in 

the figure. 

It is interesting that First Solar and Uni-Solar have 

different, but complementary, focus markets: UniSolar for commercial roofs and First Solar for 

large, ground-mounted systems. In both markets, 

they are quite competitive with companies using 

crystalline silicon technology. 

3.3 Global Solar Expands Capacity to 40 MW 

Global Solar Energy (GSE) is expanding 

production capacity to 40 MW of thin-film CIGS 

modules in 2008. In addition, a new 35-MW thinfilm copper indium gallium diselenide (CIGS) 

manufacturing plant has been set up in Germany. 

Thus, GSE’s cumulative production capacity is at 

75 MW worldwide. Some of the new encapsulation 

schemes for the CIGS modules have shown 

exceptionally good stability, especially in dampheat tests. Tests are also being conducted at 

Tucson Electric Power in Springerville, Arizona. 

Global Solar Energy also fabricated a 10.2%­

efficient, 88.9-W thin-film CIGS power module, the 

highest wattage in the world for a CIGS module. 

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ITN Energy Systems (ITN/ES) in Littleton, 

Colorado, developed an intelligent processing 

system to improve processing conditions and 

yields in cell and module fabrication that helped 

produce this module. The module parameters are 

as follows: short-circuit current = 4.07 A, opencircuit voltage = 36 V, fill factor = 0.606, and area 

= 8709 cm2

. Stainless steel webs 1000 ft in length 

were used for roll-to-roll processing of the devices. 

The typical cell structure is ITO/CdS/CIGS/Mo/SS 

(i.e., indium tin oxide/cadmium sulfide/CIGS/ 

molybdenum/stainless steel). 

The CIGS is deposited by physical vapor 

deposition, CdS by a modified chemical bath 

deposition process, and ITO and Mo by sputtering. 

More process optimization should improve module 

performance in the near future. NREL and GSE 

shared an R&D 100 Award in 2004 for 

development of the GSE CIGS technology. 

3.4 One Critical OMB/DOE/EERE Joule Milestone 

Is Completed 

One OMB/DOE/EERE/SET Joule milestone was 

completed within the partnership. One milestone 

involved achieving a higher efficiency thin-film 

module (12.2%) by the end of the fiscal year. The 

milestone was for a thin-film power module. 

3.5 University and Technical Highlights 

While technically no longer supported by the Thin 

Film Partnership, the University Center of 

Excellence (Institute of Energy Conversion (IEC), 

University of Delaware) continues to provide both 

valuable insights as well as services in the 

fabrication of thin-film solar cells. IEC 

implemented vapor transport deposition of CdTe 

solar cells and has fabricated and analyzed many 

solar cells produced using this method. A 

significant part of that work has been to 

characterize the role of impurities in the CdTe 

absorber and during “contacting” in cell 

performance. Recently, IEC began developing a 

CdTe cell on flexible foil. 

Regarding CIGS solar cells, NREL urged IEC to 

put significant effort into working on the reaction 

kinetics of selenization and sulfurization reactions. 

This now includes CIS solar cells and compares 

their characteristics to CIGS cells with a similar 

band gap. Historically, IEC has developed much 

know-how and understanding in the field of 

coevaporated CIGS solar cells. However, a while 

ago there was not enough fundamental support for 

companies forming CIGS by selenization 

(sulfurization) of metallic precursors. One key 

aspect of producing CIGS by this method is 

shortening the selenization (sulfurization) reaction 

times. IEC has also implemented in-house 

fabrication of CIGS minimodules. 

In the area of Si film solar cells, IEC recently used 

its deposition capabilities to produce 

heterojunction “HIT” solar cells. HIT cells made on 

textured Czochralski-grown Si wafers had reported 

efficiencies as high as 18.8%. 

IEC also continues developing a cell design with a 

new heterojunction wrap-through emitter. 

Although this work is being carried out by very 

talented personnel at IEC, the work (like similar 

work being done at other institutions outside the 

United States) has not yet resulted in cells with a 

competitive performance advantage over that of 

existing commercial cells produced by Sanyo. 

IEC maintains a capability to produce state-of-the 

art or near-state-of-the-art solar cells in all thin-film 

PV technologies using a variety of deposition 

approaches. The institute continues to enable 

start-up companies to complete solar cells with its 

materials. 

Solar cell fabrication continued at the University of 

Toledo. Amorphous silicon work (Deng and 

Collins) has been done as well as work on CdTe 

cells (Compaan, Karpov, and Collins). Work with 

the Florida Solar Energy Center continues on 

CIGS cells (Dhere], in addition to in-house efforts 

at NREL and at IEC. Device fabrication by 

university groups requires a significant long-term 

investment, but there are four major benefits: 

1. Commercial spin-off opportunities can be 

created (e.g., Xunlight Corp. from the 

University of. Toledo, AVA Solar from 

Colorado State university); 

2. A better understanding of solar cell physics 

can be obtained, because university cell 

makers usually reveal more detail than 

industrial groups do about their cell fabrication 

methods; 

3. Specialized cells for special measurements 

can be fabricated that resemble regular cells; 

and 

4. Options for changes in processing can be 

explored before industry has to invest in 

expensive modifications of pilot or production 

equipment. 

Beyond a capability for analyzing losses in cells 

and modules, the University of Toledo has also 

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developed mitigation schemes for reducing the 

losses arising from localized “weak diodes” and 

shunts. 

The Universities of Nevada and Oregon continued 

work on the chemical composition and energy 

band gap measurements of solar cells as well as 

measurements using defect spectroscopes 

(Heske, Cohen). They moved from having 

specialized cell structures fabricated for the 

research to applying their characterization 

techniques to actual solar cell structures with 

known performance. 

Research at the University of Utah (Taylor, now at 

Colorado School of Mines) has been providing 

valuable insights into light-induced degradation 

mechanisms (the Staebler-Wronski effect) in aSi:H alloys and nc-Si:H. And at the University of 

South Florida in Tampa, researchers are 

investigating doping the CdTe absorber film with 

P. They are also studying the effect of a new TiO2 

buffer layer and a back contact of TiSe2 produced 

by sputtering. 

Investigations at Colorado State University (CSU) 

have already resulted in 12% to 13% efficient thinfilm CdTe solar cells. This work has also made 

valuable contributions to device stability under 

long-term light exposure. 

The CSU group (Sites) continued to provide 

valuable analyses of the performance of CIGS and 

CdTe solar cells, identifying pathways for further 

enhancing cell performance. Prof. Sites’ graduate 

students now hold many prestigious and important 

R&D positions with a variety of companies and 

organizations. CSU’s thin-film PV technology has 

been transferred to AVA Solar of Fort Collins, 

Colorado. 

In addition, encapsulation research continued at 

Pacific Northwest National Laboratory (PNNL) 

(Olsen). Researchers reported encouraging 

progress in finding low-cost transparent 

encapsulation schemes for CIGS cells that show 

significantly reduced power losses after dampheat testing. 

Other than NREL’s in-house group, PNNL’s is the 

only group dealing with cell and module packaging 

and encapsulation issues. This is an important 

area, as many current industrial start-ups prepare 

to produce a flexible CIGS product on a foil 

substrate. Currently, no low-cost, flexible 

transparent packaging exists for CIS products that 

allows a long-term (20 years or more) power 

warranty for flexible CIGS modules. 

3.6 Tracking Metrics 

Each year, we track cell efficiencies, best 

prototype module efficiencies, and commercial 

module efficiencies for thin-film PV (see Tables 3 

and 4). Updated information is posted on our Web 

site and can be found via the search page. 

There are currently about 40 thin-film PV 

companies operating in the United States. These 

include 15 companies focusing on a-Si/thin Si 

technologies, 10 on CdTe, and 15 on CIGS. 

Another 4 U.S. CIGS PV companies should be 

announced in 2008. Worldwide, there are about 35 

PV companies producing CIGS products. 

DOE Thin Film PV Partnership subcontracts and 

funding amounts for FY 2007 are listed in Section 

7. 

4. Planned FY 2008 Activities 

In FY 2008, although most university subcontracts 

are being phased out, the Thin Film PV 

Partnership will continue to address key issues 

supporting successful first-time manufacturing 

efforts and the explosive growth in manufacturing 

that is occurring for each thin-film technology. 

These will be especially important in FY 2008, 

which is expected to be a key year for growth in 

thin-film manufacturing. U.S. production increased 

from about 10 MW in CY 2003 to about 160 MW in 

CY 2007. Another substantial increase could occur 

in CY 2008 to approximately 270 MW. 

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Table 3. Best Large-Area, Thin Film Modules 

(standard conditions and aperture area) 

Company Device Size 

(cm2

) 

Efficiency Power 

(W) 

Date 

Mitsubishi 

Heavy* 

Glass/a-Si 15625 6.4% (stabilized) 100 7/05 

Global Solar 

Energy 

CdS/CIGS/SS 8709 10.2% 88.9 5/05 

Wurth Solar CdS/CIGS/glass 6500 13% 84.6 6/04 

United Solar a-Si/a-SiGe/a-SiGe/SS 9276 7.6% (stabilized) 70.8 9/97 

First Solar Glass/CdS/CdTe 6624 12.2% 80.2 12/07 

Shell Solar 

GMBH CIS-alloy/CdS/glass 4938 13.1% 64.8 6/04 

Sharp* Glass/a-Si/nano-Si 4770 11% (stabilized) 52.5 7/05 

Antec Solar* Glass/CdS/CdTe 6633 7.3% 52.3 6/04 

Kaneka Glass/a-Si 8100 6.3% (stabilized) 51 7/04 

Shell Solar 

Industries CdS/CIS-alloy 3644 12.9% 46.8 5/05 

Showa Shell* Zn(O,S,OH)x/CIGS/Glass 3459 13.4% (4 1-ft2

 modules 

laminated together) 

46.45 8/02 

EPV Glass/a-Si/a-Si 7432 5.7% (stabilized) 42.3 10/02 

United Solar a-Si triple/SS 4519 7.9% (stabilized) 35.7 6/97 

*Indicates data reported by company, but not, to our knowledge, independently measured. 

Table 4. Commercial Thin-Film Modules 

(total-area efficiencies; data compiled from Web sites) 

Rated Module 

Efficiency (%) Description 

Rated 

Output 

(Wp) 

Estimated Price 

($/Wp) 

Temperature 

Coefficient* 

(%/oC) 

11.0 WürthSolar WS31050/80 (CIS) 80 Above $3 -0.36 

9.4 First Solar FS65 (CdTe) 67.5 Below $3 -0.25 

6.9 Antec-Solar ATF50 (CdTe) 50 Below $3 -0.18 

6.3 Kaneka GEA/GSA 

(single-junction a-Si) 60 Below $3 -0.2 

6.4 Mitsubishi Heavy MA100 (singlejunction a-Si, VHF deposition) 100 Below $3 -0.2 

6.3 Uni-Solar US-64 (triple-junction 

amorphous silicon) 64 $3.10–$3.40 -0.21 

5.3 RWE Schott ASI-F32/12 

(same bandgap a-Si tandem) 32.2 Varies -0.2 

*Temperature coefficients will vary slightly, depending on the local spectral content. 

Data compiled by B. von Roedern, NREL, September 2006. Note: This list could now be out of date or incomplete; 

some manufacturers and/or some "best" products could be missing. Prices are estimates for large quantities.
 

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5. FY 2007 Awards 

Harin S. Ullal received an NREL Directors 

Award as NREL’s designated Point of Contact 

for the Solar America Initiative from 2007 to 

2010. 

6. Major FY 2007 Presentations and 

Publications 

We have published several subcontract reports 

and presentations and have posted them on the 

Thin Film PV Partnership Web site. Other 

important publications include the following: 

Harin S. Ullal; “Thin Film Solar Photovoltaic 

Technologies: Progress and Outlook,” Solar 

Power 2007, Long Beach, CA, September 

(2007). 

Harin S. Ullal, “Thin Film Solar Electric 

1st Technologies: Challenges and Outlook,” 

Investors PV Conference, Munich, Germany; 

April (2007). 

Harin S. Ullal, “Thin Film Solar Electric 

Technologies,” Solar Power 2006, San Jose, 

CA, October (2006). 

Harin S. Ullal and Bolko von Roedern, “Thin Film 

CIGS and CdTe PV Technologies: 

Commercialization, Critical Issues and 

Applications,” 22nd European Photovoltaic Solar 

Energy Conference, Milano, Italy, September 

(2007). 

Bolko von Roedern, “High-Efficiency Si Solar 

Cell Processing Requirement: Why 0.5 + 0.5 ≠ 1 

(i.e., >3),” 17th Workshop on Crystalline Silicon 

Solar Cells and Modules: Materials And 

Processes, Vail, Colorado, August (2007). 

Bolko von Roedern, “Si Thin-Film Photovoltaics 

Program in the U.S.,” International Workshop on 

Thin Film Silicon Solar Cells, Nara City, Japan, 

February (2007). 

Bolko von Roedern, “Past Progress and Future 

Developments in Photovoltaic Module 

Manufacturing,” California-Germany Solar Day 

Workshop, San Francisco, CA, March (2007). 

Bolko von Roedern, “PV Research Activities in 

the US,” International Symposium on Silicon to 

Light/Light to Silicon: Materials, Characterization 

and Applications, Halle, Germany, July (2007). 

7. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2007 

($K) 

Cost 

Share 

($K) 

Colorado School of Mines; 

Jim Sites 

Ft. Collins, CO 

sites@lamar.colostate.edu 

Characterization and analysis of 

CIS and CdTe devices 195 0 

Colorado State University; 

W.S. Sampath 

Ft. Collins, CO 

sampath@engr.colostate.edu 

Development of a robust in-line 

manufacturing approach for 

CdTe, and stability assurance 

400 0 

Energy Photovoltaics; 

Alan Delahoy 

Lawrenceville, NJ 

a.delahoy@epv.net 

Advanced CIGS photovoltaic 

technology 350 100 

First Solar, LLC; 

Peter Meyers 

Perrysburg, OH 

pmeyers@firstsolar.com 

Expanding the limits of CdTe PV 

Performance 412 20 

First Solar, LLC; 

Roger Green 

Perrysburg, OH 

rgreen@firstsolar.com 

Research leading to highthroughput processing of thin-film 

CdTe PV technology 

1000 1050 

Florida Solar Energy 

Center; 

Neelkanth Dhere 

Cocoa, FL 

dhere@fsec.ucf.edu 

CIGS solar cells by selenization 

and sulfurization 209 10 

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Global Solar Energy Tucson, AZ 

swiedman@globalsolar.com 

Cost and reliability 

Improvements for CIGS based 

on flexible substrates 

690 732 

NanoSolar; 

Chris Eberspacher 

Palo Alto, CA 

chris@nanosolar.com 

High-productivity annealing for 

thin film CIS PV 200 10 

Pacific Northwest National 

Laboratory; 

Larry Olsen 

Richland, WA 

Larry.Olsen@pnl.gov 

Barrier coatings for thin-film cell 

protection 163 0 

United Solar Ovonic; 

Subhendu Guha 

Auburn Hills, MI 

sguha@uni-solar.com 

High-efficiency amorphous and 

nanocrystalline-based solar cells 

and modules 

997 997 

University of Nevada; 

Clemens Heske 

Las Vegas, NV 

heske@unlv.nevada.edu 

Characterization of the electronic 

and chemical structure at the 

thin-film solar cell interfaces 

181 0 

University of Oregon; 

Dave Cohen 

Eugene, OR 

dcohen@oregon.uoregon.edu 

Innovative characterization of 

amorphous and thin-film silicon 

for improved module 

performance 

200 0 

University of South 

Florida; 

Chris Ferekides 

Tampa, FL 

ferekide@eng.usf.edu 

High-efficiency CdTe cells by 

CSS 200 14 

University of Toledo; 

Al Compaan 

Toledo, OH 

ADC@physics.utoledo.edu 

Fabrication and physics of CdTe 

devices by sputtering 328 100 

University of Toledo; 

Xunming Deng 

Toledo, OH 

dengx@physics.utoledo.edu 

Fabrication and characterization 

of advanced triple-junction 

amorphous-silicon-based solar 

cells 

355 100 

University of Utah; 

Craig Taylor 

Salt Lake City, UT 

craig@physics.utah.edu 

Innovative characterization of 

amorphous and thin-film silicon 

for improved module 

performance 

170 0 

Photovoltaic R&D

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Systems Analysis 

PV Grid Integration 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Ben Kroposki (NREL, Primary Contact), 303-384-2979, 

benjamin_kroposki@nrel.gov 

Robert Margolis (NREL), 202-488-2222, robert_margolis@nrel.gov 

Juan Torres (SNL, Primary Contact), 505-844-0709, jjtorre@sandia.gov 

Charles Hanley (SNL), 505-844-4435, cjhanle@sandia.gov 

DOE HQ Technology Manager:	 Dan Ton, 202-586-4618, dan.ton@ee.doe.gov 

FY 2007 Budgets:	 $1,950K (NREL), $700K (SNL) 

Objectives 

•	 Conduct series of 14 studies on impacts, plans, and strategies to address high penetration of 

photovoltaic (PV) systems on electric infrastructure. 

•	 Complete a multi-year research plan for DOE related to Renewable Systems Interconnection 

(RSI) initiative. 

•	 Develop position paper for Solar Energy Grid Integrated Systems (SEGIS) initiative as part of 

RSI. 

•	 Assist in developing strategy for RSI initiative. 

Accomplishments 

•	 Completed drafts of 14 reports, including analysis and modeling. To read the executive summary, 

“Renewable Systems Interconnection: Executive Summary,” visit 

www.eere.energy.gov/solar/solar_america/rsi.html. 

•	 Presented preliminary findings to DOE. 

•	 Completed draft RSI multi-year research plan, which is used for internal DOE communications. 

•	 Completed SEGIS position paper as a precursor to fiscal year (FY) 2008 solicitation. 

Future Directions 

•	 Publish and release of finalized reports, including the executive summary. 

•	 Continue to scope out a broad cross-cutting initiative within EERE, on behalf of DOE/Solar. This 

initiative would cover several areas effecting renewable systems interconnection including: 

advanced technology development, advanced distribution systems integration, system-level test 

and demonstrations, distributed renewable energy analysis, solar resource assessment, and 

codes, standards, and regulatory implementation. 

•	 Collect field data to verify early findings and steer future technology R&D. 

•	 Develop field implementation sites for new concepts and hardware, including Hawaii, Mesa del 

Sol, Solar Technology Acceleration Center (SolarTAC), etc. 

•	 Develop an advanced storage initiative as part of RSI. 

•	 Initiate and complete SEGIS initiative to develop new hardware to facilitate high penetration of PV 

into electric grid. 

•	 Develop lab-based test and development sites to provide leadership and early development for 

industry efforts. 

1. Introduction Energy Technologies Program (SETP) initiative in 

the near term. The objective was to develop a 

This effort was started late in the fiscal year, as a series of reports based on technical assessments 

means of scoping out what may become a Solar of the impacts and needs related to high 

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penetration of PV systems on today’s electric 

infrastructure. These studies included analyses of 

utility planning tools and methods, PV system and 

distribution system designs, utility business 

models, and studies of impact and penetration. A 

broad team was formulated to complete this effort 

in a short time period, with important support 

coming from partners such as GE, EPRI, 

Navigant, and BEW (see section 6). 

2. Technical Approach 

RSI Study 

The approach employed was to quickly build a 

team of appropriate technical experts, designate 

the areas of focus for the contributors, and hold 

regular discussions to ensure that the complete 

package would be well integrated with appropriate 

cross references. Originally, five areas were 

envisioned, but more needs were identified, so the 

effort grew to 14 reports. 

RSI Multi-Year Research Plan 

SNL, NREL, and DOE collaborated on utilizing the 

gaps that were identified in the reports to develop 

a 5-year plan to provide research and 

development (R&D) leadership, in partnership with 

the U.S. industry. This plan defines near- and 

longer-term activities to assist in the infrastructure 

transition needed for minimal interruption as PV 

penetration continues to increase. 

SEGIS Position Paper 

This paper focuses specifically on the 

development of new inverters, controllers, and 

energy management systems for the solicitation 

that is slated to start in FY 2008. DOE worked 

with SNL to develop a document that establishes 

the objectives and scope of the solicitation. 

3. Results and Accomplishments 

By the end of FY 2007, draft reports were 

completed in all areas. These reports reflect the 

results of intensive efforts at modeling, analysis, 

system design studies, and research into current 

and future operating methodologies for utilities and 

other industry players. The 14 RSI reports cover 

the following areas: 

•	 Advanced Grid Planning and Operations. 

•	 Utility Models, Analysis and Simulation Tools. 

•	 Advanced PV System Designs and 

Technology Requirements. 

•	 Development of Analysis Methodology for 

Evaluating the Impact of High Penetration PV 

•	 Distribution System Performance Analysis for 

High Penetration PV. 

•	 Enhanced Reliability of PV Systems with 

Energy Storage and Controls. 

•	 Transmission System Performance Analysis 

for High Penetration PV. 

•	 Cyber Security Analysis. 

• Solar Resource Assessment: Characterization 

and Forecasting to Support High PV 

Penetration. 

•	 Test and Demonstration Program Definition to 

Support High PV Penetration. 

• Value Analysis. 

• PV Business Models. 

•	 Production Cost Modeling for High Levels of 

PV Penetration. 

•	 PV Market Penetration Scenarios. 

All of these efforts have been successful in 

facilitating internal DOE communications and 

allowing the development of well-aligned, followup activities in the context of a growing initiative. 

These reports have also been helpful in obtaining 

industry input into this process. 

4. Planned FY 2008 Activities 

Major activities are focused on completing the final 

versions of the RSI reports and setting up a 

project to gather and analyze field data to provide 

validation of the findings and further our 

understanding of the impacts of high PV 

penetration on the electric grid. The Hawaii Clean 

Energy Initiative (HCEI) will also provide a nearterm opportunity to begin addressing RSI issues in 

partnership with the Hawaii State Energy Office 

and utilities on the islands of Kauai and Lanai. 

Additionally, as we prepare for a larger initiative in 

this area, we’re working to define R&D needs with 

controllers, energy management systems, and 

integrated storage. 

We’ve identified the following tasks: 

•	 Collect field data at model high-penetration 

field sites such as communities with the 

Sacramento Municipal Utility District (SMUD), 

Nellis Air Force Base, and Xcel Energy in 

Alamosa, CO. 

•	 Complete a position paper on the role of 

integrated storage in high penetration PV 

scenarios, including associated R&D needs. 

•	 Develop action plans and collect field data 

from additional partnerships such as the State 

of Hawaii, Mesa del Sol in Albuquerque, 

SolarTAC, etc. 

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•	 Define additional laboratory development, 

testing, and evaluation needs to support 

industry and DOE-led developments. 

•	 Initiate the SEGIS solicitation. 

5. Major FY 2007 Publications 

D. Ton, B. Kroposki, and R. Margolis, G. Kuswa, J. 

Torres, W. Bower, C. Hanley, J. Boyes, “DRAFT 

Renewable Systems Interconnection Distributed 

PV Activities; Multi-Year Research Plan (MYRP) 

FY2008-FY2013,” (2007). 

D. Ton, W. Bower, C. Cameron, “DRAFT Solar 

Energy Grid Integration Systems (SEGIS); 

Concept Paper,” (2007). 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2007 

($K) 

Cost Share 

($K) 

Electric Power 

Research Institute/ 

Tom Key 

Palo Alto, CA 

Renewable Systems 

Interconnection – High Penetration 

Distributed Photovoltaics Studies – 

Distribution Designs and Utility 

Models 

253 -

General Electric/ 

Jovan Bebic Niskayuna, NY 

Renewable Systems 

Interconnection – High Penetration 

Distributed Photovoltaics Studies 

406 -

BEW Engineering/ 

Chuck Whitaker San Ramon, CA 

Renewable Systems 

Interconnection – PV Technology 

and Field Testing 

163 -

Navigant Consulting/ 

Lisa Francis San Francisco, CA 

Renewable Systems 

Interconnection – High Penetration 

Distributed Photovoltaics Studies – 

Business Cases, Value Analysis, 

Market Penetration 

540 -

Sunpower/ 

Gary Wayne San Jose, CA Feasibility Study of PV Integrated 

with V2G 50 -

Global Energy 

Decisions/ Boulder, CO 

Renewable Systems 

Interconnection –Market 

Penetration for PV 

50 -

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

Systems Analysis 

Market, Value, and Policy Analysis 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Lawrence Berkeley National Laboratory (LBNL) 

Key Technical Contacts:	 Robert Margolis (NREL, Primary Contact), 202-488-2222, 

robert_margolis@nrel.gov 

Ryan Wiser (LBNL), 510-486-5474, RHWiser@lbl.gov 

DOE HQ Technology Manager: Dan Ton, 202-586-4618, dan.ton@ee.doe.gov 

FY 2007 Budgets: $510K (NREL), $100K (LBNL) 

Objectives 

•	 Develop long-term market penetration projections for photovoltaic (PV) technologies. 

•	 Develop the Solar Deployment Systems (SolarDS) model—a PV market-penetration model that 

will serve as an alternative to the National Energy Modeling System (NEMS) and be compatible 

with the broader model-development effort within the Solar Energy Technologies Program. 

•	 Evaluate policies and other factors that impact the value of solar energy technologies in a variety 

of markets. 

Accomplishments 

•	 Continued to develop the SolarDS model and a number of other tools, such as PVFlex, to 

examine the impacts of high levels of PV penetration on the U.S. electricity generation system. 

•	 Enhanced the Web-based distributed PV cost-benefits clearinghouse. 

•	 Carried out a wide range of policy analysis in support of the Solar Energy Technologies Program, 

in particular, to help provide a context for the planning and execution of research and 

development (R&D) under the Solar America Initiative (SAI). 

Future Directions 

•	 Publish an annual report on solar market, cost, and performance trends. 

•	 Provide analytical and technical support to the PV Industry Roadmap process. 

•	 Continue to maintain and enhance the PV Value Clearinghouse. 

•	 Support the annual Government Performance and Results Act (GPRA) benefits and Program 

Decision Support analysis efforts. 

•	 Produce a series of topical reports that anticipate and respond to the emerging critical needs of 

the solar industry and the Solar Energy Technologies Program. 

1. Introduction 

The primary objective of the market, value, and 

policy analysis activity is to provide a broad range 

of analytical support to the U.S. Department of 

Energy’s (DOE) Solar Energy Technologies 

Program (SETP). The types of analysis carried 

out under this project include the following: 

Market analysis: This includes developing a PV 

market penetration model, the Solar Deployment 

Systems, or SolarDS, model. The model is being 

designed to gain insight into the factors influencing 

the market penetration of PV technology into U.S. 

markets. 

Value/benefits analysis: This includes providing 

inputs to, support for, and review of the annual 

GPRA benefits analysis and program decision 

support analysis efforts. It also includes 

developing methods and tools for improving the 

quantification of the benefits and cost of solar 

technologies. 

Policy analysis: This includes defining and 

carrying out analysis that meets the needs of the 

Solar Energy Technologies Program in a timely 

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fashion, for example, related to issues such as the 

reliability, security, and time-of-use value of PV, as 

well as the potential role of solar in the energy 

economy in the long term. 

The market, value, and policy analysis activity 

provides an array of support to the SETP that 

integrates the program’s modeling and 

benchmarking activities into an analysis of a 

technology advancement’s impact on market 

penetration. It also quantifies the potential benefits 

of increased solar energy use. 

2. Technical Approach 

The market, value, and policy analysis activity 

relies on two main technical approaches. 

The first approach is to use and improve existing 

models and to develop new tools that can be 

employed to develop long-term market-penetration 

projections for solar technologies. This effort 

involves examining both the system and policy 

drivers of solar technologies in various markets in 

both the short and long term, as well as improving 

the analytical basis for projecting the SETP’s 

economic and environmental benefits. Here, the 

emphasis has been on models and modeling, for 

example, using existing models—such as the 

Energy Information Administration’s NEMS, 

MARKAL, and others—to carry out analyses. 

These analyses examine the structure of various 

models and provide feedback on how to improve 

the representation of solar technologies in existing 

models to modelers. They also help to develop 

new models, such as SolarDS and PVFlex, that 

will help meet the needs of the SETP and solar 

community more broadly. 

The second approach is to employ a range of 

policy analysis tools and techniques to evaluate 

policies and other factors that impact the value of 

PV technologies in a variety of markets. These 

tools and techniques include using existing 

models, spreadsheets, and other tools (such as 

surveys and gathering and synthesizing 

information from a wide range of sources). Here, 

the emphasis is on using analytical tools to 

quantify how changing policies, rate structures, 

system designs, and other factors have or will 

impact the value of solar technologies to 

consumers, utilities, governments, and other 

players. 

3. Results and Accomplishments 

The market, policy, and value analysis activities 

resulted in a wide range of accomplishments 

during FY 2007. Some of the accomplishments 

include the following: 

•	 Writing an internal DOE white paper and 

presentation material on the impact of 

extending the solar investment tax credit 

•	 Writing an internal DOE white paper on the 

potential impact of establishing a solar 

manufacturing tax credit 

•	 Providing numerous background slides and 

material for presentations given by the SETP 

Program Manager and staff on the program’s 

activities, market trends, and future directions 

(such as internal DOE briefings, hill staff 

briefings, investor briefings, and conference 

presentations) 

•	 Presenting analysis activities results at a 

number of major solar industry conferences 

and meetings (such as Solar 2007 and Solar 

Power 2007) 

•	 Providing support to the California Solar 

Initiative’s effort to design and launch its 10-

year, $50 million R&D program 

•	 Completing a detailed analysis of the potential 

economic benefits of meeting the SAI targets. 

Many of these activities resulted in conference 

papers, technical reports, or journal publications, 

as listed in Section 5. 

4. Planned FY 2008 Activities 

Over the next 5 years, as solar markets continue 

to grow at a record pace and solar technologies 

continue to evolve rapidly, the need for detailed, 

timely analysis will be critical for helping to guide 

policy decisions within the SETP. Thus, a number 

of ongoing analytical activities will be supported 

under this task. These ongoing activities include 

publishing an annual report on solar market, cost, 

and performance trends, working with industry to 

produce a semi-annual PV Industry Roadmap, 

maintaining and enhancing the PV Value 

Clearinghouse, producing and improving the 

annual GPRA benefits and Program Decision 

Support analysis, and producing a series of topical 

reports that anticipate and respond to the 

emerging critical needs of both the solar industry 

and the SETP. 

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5. Major FY 2007 Publications 

P. Denholm and R. M. Margolis, "Evaluating the 

Limits of Solar Photovoltaics (PV) in Electric 

Power Systems Utilizing Energy Storage and 

Other Enabling Technologies," Energy Policy, Vol. 

35, pp. 4424-4433 (2007). 

P. Denholm and R. M. Margolis, "Evaluating the 

Limits of Solar Photovoltaics (PV) in Traditional 

Electric Power Systems," Energy Policy, Vol. 35, 

pp. 2852–2861 (2007). 

P. Denholm, R. M. Margolis, and K. Zweibel, 

“Tackling Climate Change in the U.S.: Potential 

Carbon Emissions Reductions from Solar 

Photovoltaics by 2030,” Chapter in Tackling 

Climate Change in the U.S.: Potential Carbon 

Emissions Reductions from Energy Efficiency and 

Renewable Energy by 2030, Boulder, CO: 

American Solar Energy Society (2007). 

S. Grover, Energy, Economic, and Environmental 

Benefits of the Solar America Initiative, Report No. 

NREL/SR-640-41998, Golden CO: National 

Renewable Energy Laboratory, August (2007). 

T. E. Hoff, R. Perez, and R. M. Margolis, 

“Maximizing the Value of Customer-Sited PV 

Systems Using Storage and Controls,” Solar 

Energy, Vol. 81, pp. 940-945 (2007). 

J. I. Levene, M. K. Mann, R. M. Margolis, and A. 

Milbrandt, “Analysis of Hydrogen Production from 

Renewable Electricity Sources,” Solar Energy, 

Vol. 81, pp. 773-780 (2007). 

R. Wiser, A. Mills, G. Barbose, and W. Golove, 

The Impact of Retail Rate Structures on the 

Economics of Commercial Photovoltaic Systems 

in California, Report No. LBNL-63019. Berkeley, 

CA: Lawrence Berkeley National Laboratory, July 

(2007). 

R. Wiser, M. Bolinger, P. Clappers, and R. 

Margolis, “Analyzing Historical Cost Trends in 

California’s Market for Customer-Sited 

Photovoltaics,” Progress in Photovoltaics: 

Research and Applications, Vol. 15, pp. 69–85 

(2006). 

R. Wiser, M. Bolinger, P. Clappers, and R. 

Margolis, “PV Cost Trends: Letting the Sun Shine 

on Solar Costs in California,” REFocus. 

September/October, pp. 26-31 (2006). 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2007 

($K) 

ECONorthwest 

Steve Grover 

Portland, OR 

grover@portland.econw.com 

Energy, Economic and 

Environmental Benefits of the Solar 

America Initiative 

100 

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____________________________________________________________________________________ 

Systems Analysis 

Modeling 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Nate Blair (NREL, Primary Contact), 303-384-7426, nate_blair@nrel.gov 

Mark Mehos (NREL), 303-384-7458, mark_mehos@nrel.gov 

Chris Cameron (SNL), 505-844-8161, cpcamer@sandia.gov 

Craig Christensen (NREL), 303-384-7510, craig_christensen@nrel.gov 

DOE HQ Technology Manager:	 Dan Ton, 202-586-4618, dan.ton@ee.doe.gov 

FY 2007 Budgets:	 $550K (NREL), $850K (SNL) 

Objectives 

•	 The system modeling efforts of this project seek to enhance the U.S. Department of Energy 

(DOE) Solar Energy Technologies Program (SETP) Solar Advisor Model (SAM) to develop 

capabilities to calculate energy output, energy costs, and cash flows using up-to-date component 

and system data while enabling parametric analysis. 

•	 These efforts will also validate SAM and, potentially, other solar models for a variety of 

technologies, applications, and locations. 

•	 These tools can be used to by industry and government to guide research and development 

(R&D) prioritization and to provide credible energy production and cost data using a common 

platform for project development, evaluation, and due diligence. 

•	 These efforts will also provide additional tools to industry to meet their planning, R&D, siting, and 

other modeling needs to help accelerate market penetration. 

•	 These efforts will support progress evaluation at stage-gate assessments for the Solar America 

Initiative (SAI). 

Accomplishments 

•	 Completed an industry survey of modeling needs. 

•	 Included concentrating solar power (CSP) parabolic trough modeling within SAM. 

•	 Included detailed incentives within SAM for all technologies. 

•	 Enhanced graphical outputs, parametrics, and sensitivity analysis. 

•	 Improved speed of calculations significantly. 

•	 Completed a dish Stirling performance model by a subcontractor. 

•	 Developed a photovoltaic (PV)-system inverter model for use within SAM. 

•	 Developed tools to permit validation of performance models versus and measured weather data 

and system output. 

•	 Refined cost and performance estimates for PV reference systems. 

•	 Conducted analysis in support of SAI and other program initiatives, such as the Solar Energy Grid 

Integration System. 

Future Directions 

•	 Develop a SAM version with: 

o	 A major update of the user manual including documentation; 

o Improved PV-performance algorithms; 

o	 Capability of using the latest California Energy Commission (CEC) and Sandia module 

 and inverter databases; 

o	 Detailed operation and maintenance (O&M) inputs including annual cost, cost/MW, and 

 cost/MWh options. 

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____________________________________________________________________________________ 

 

 

 

•	 Release SAM version with: 

o	 Dish Stirling CSP models incorporated; 

o	 Enhanced graphical user interfaces (GUI) and greater graphical output capability; 

o Time-of-use rates. 

•	 Develop a 10-km-resolution combined solar radiation and meteorological data set for the PVWatts Web-based calculator. 

•	 Complete validation of PV-performance models. 

•	 Provide modeling support to SETP programs, including SAI stage-gate evaluations. 

1. Introduction 

The objective of this project is to provide a focal 

point for system-driven-approach (SDA) activities 

and to provide a common framework for 

evaluation of all solar technologies. This 

evaluation happens within the cost, financing, and 

performance modeling of PV systems, CSP, and 

other solar technologies. 

2. Technical Approach 

The system modeling task consists of systems 

performance and cost modeling and validation 

projects. The primary function of the Solar Advisor 

Model (SAM) is to allow users to investigate the 

impact of variations in physical and financial 

parameters to better understand their impact on 

key figures of merit for solar power systems. 

Figures of merit related to the cost and 

performance of these solar power systems 

include, but are not limited to, system output, peak 

and annual system efficiency, levelized cost of 

energy, and system capital and O&M costs. SAM 

is intended for use by DOE, laboratory 

management, and research staff and is a critical 

element in the implementation of the systemsdriven approach to SETP program planning. The 

model is and will continue to be used by members 

of the solar industry to inform internal R&D 

direction and to estimate systems cost and 

performance 

3. Results and Accomplishments 

For SAM, particular emphasis was placed upfront 

on the design of a user interface that could meet 

the needs of a diverse set of users. User profiles 

were developed to provide a general description of 

DOE, laboratory, and industry users and their 

motivation for using the modeling tool. 

The working model for SAM consists of: 

•	 A user-interface module for selecting and 

providing input data on the system 

configuration and operating environment. 

•	 A system-performance module that simulates 

the hour-by-hour output of the selected system 

for the lifetime of a project. 

•	 A cost-input module for providing simple or 

detailed cost inputs for system components. 

•	 A financial-analysis module for calculating 

system economics. 

The modules work in concert to generate the 

physical and financial figures of merit relevant to 

the particular user. 

FY 2007 development activities for SAM primarily 

focused on several areas. One specific effort was 

to add a parabolic trough model to SAM for use by 

DOE solar program planners for the CSP program 

and by the CSP industry. The model within SAM 

was originally developed at NREL by Hank Price 

within Excel, called Excelergy. This undocumented 

model was not easily transferrable to industry, nor 

to DOE analysts. The implementation of the same 

algorithms within the SAM environment makes 

them more accessible and continuously improving 

documentation makes it easier to get new users 

up to speed. 

A second area of focus was improving financial 

analysis methods for the residential, commercial 

and utility markets. Extensive efforts have been 

put into making the utility financing portion of the 

model accurate and appropriate from the 

perspective of the project developer. Finally, 

extensive efforts have been incorporated into 

adding the ability to factor in incentives such as 

infrastructure tax credits, production tax credits, 

and buy downs into the model for all markets. This 

is critically important as subsidies are so prevalent 

for financing solar projects. 

For PV, research efforts focused on developing 

the data and tools to validate the performance 

models. An inverter model was developed and will 

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be incorporated into SAM in FY 2008. The model 

was also applied in support of the SETP, including 

the Solar America Initiative. 

In carrying out these projects, we use resources at 

NREL and Sandia as well as the subcontracts 

described in Section 6. 

4. Planned FY 2008 Activities 

•	 Release a SAM version with additional 

weather-file type support. 

•	 Incorporate a user forum and user interactivity 

into SAM. 

•	 Validate SAM versus measured system data 

and document findings in a research paper 

•	 Release a SAM version with: 

o	 A major update of the user manual 

including documentation; 

o	 Improved PV performance algorithms; 

o	 capability of using latest CEC and SNL 

module and inverter databases; 

o	 Detailed O&M inputs including annual 

cost, cost/MW, and cost/MWh options. 

•	 Hold a first modeling workshop concurrently 

with the American Solar Energy Society 

meeting. 

•	 Publish a subcontractor report on financial 

model validation. 

•	 Release a SAM version with: 

o	 Dish Stirling CSP models; 

o	 Enhanced GUI and greater graphical 

output capability; 

o Time-of-use rates. 

•	 Complete PV model validation. 

•	 Provide modeling support to the SETP 

program. 

5. Major FY 2007 Publications 

C. Cameron and C. Cornelius, “A Systems-Driven 

Approach to Solar Energy R&D,” Paper presented 

at the IEEE International Conference on System of 

Systems Engineering, San Antonio, TX, April 16-

18, 2007, (2007). 

S. Gonzalez, W. Boyson, G. Galbraith, and D. 

King, “Performance Model for Grid-connected 

Photovoltaic Inverters, Albuquerque, NM: Sandia 

National Laboratories, SAND2007-5036, 

(September 2007). 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2007 

($K) 

Cost Share 

($K) 

Janzou Consulting 

Steve Janzou 

Evergreen, CO 

Steve_janzou@nrel.gov 

Program the front-end and basic 

engine of the Solar Advisor Model 105 0 

University of WisconsinMadison 

Prof. Sanford Klein 

Madison, WI 

Klein@engr.wisc.edu 

Development of a dish-Stirling 

model for use in SAM 82 0 

Paul Gilman 

Paul Gilman 

Chicago, IL 

PaulGilman@earthlink.net 

Provides user support and 

technical writing support 35 0 

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Systems Testing and Evaluation 

PV Inverter and Balance-of-System Testing 

Performing Organizations: Sandia National Laboratories (SNL) 

 Northern Plains Power 

Key Technical Contacts: Sigifredo Gonzalez (SNL, Primary Contact), 505-845-8942, 

sgonza@sandia.gov 

Ward Bower (SNL), 505-844-5206, wibower@sandia.gov 

Michael Ropp (Northern Plains Power), 605-688-4664, 

Michael.Ropp@SDSTATE.EDU 

DOE HQ Technology Manager: Dan Ton, 202-586-4618, dan.ton@ee.doe.gov 

FY 2007 Budgets: $850K (SNL), $50K (Northern Plains Power) 

Objectives 

•	 Determine effects of long-term inverter operation after 2 years of outdoor operation. Evaluating 

sample inverters after 2 years both provides reliability information for a small grid-connected 

system and provides a platform to validate system modeling activities. 

•	 Assist in the development of new photovoltaic (PV) inverters and balance-of-system (BOS) 

hardware that meet today’s utility interconnect standards, performance requirements, and safety 

requirements. 

•	 Enable PV inverter manufacturers to meet standard and code requirements through laboratory 

evaluations. 

•	 Develop a test platform and protocols to evaluate Solar America Initiative (SAI) stage-gate 

deliverables and Solar Energy Grid Information Systems (SEGIS) project stage-gate deliverables. 

Accomplishments 

•	 Conducted the laboratory recharacterization evaluations on the first set of inverters undergoing 

long-term evaluations. Inverter efficiencies are only slightly lower but the most significant finding 

was that the maximum continuous power rating was lower on the 4 units evaluated. 

•	 Evaluated Xantrex’s High Reliability Inverter Initiative deliverable (XW 6000). Issues that were 

discovered during laboratory testing led to several software revisions. The system continues to 

be evaluated. 

•	 Determined inverter performance, power quality, and utility compatibility capabilities for two 

commercial inverters and three residential PV inverters. Feedback was provided to the 

respective manufacturers and most of the beta units have implemented either software or 

hardware modifications or rectifications. 

•	 Implemented and conducted preliminary validation evaluations on a PV system performance 

model. Utilizing a complete PV system provided by USDA Rural Utilities Service (RUS) 

preliminary validation evaluations results were quantified. 

•	 Conducted laboratory evaluations per American National Standards Institute’s (ANSI’s) ANSI 

C62.45 requirements on two surge-suppression circuits. Evaluated a residential inverter’s 

integrated surge suppression circuitry for conformance to Underwriters Laboratories’ (UL’s) UL 

1741-2005 standard and a retrofit circuit board for a three-phase commercial PV inverter. 

•	 Sandia collaborated with Dr. Michael Ropp of South Dakota State University (SDSU) in the 

development of a MATLAB/Simulink model of a single-phase grid-connected photovoltaic system. 

Future Directions 

• Assure that DOE maintains a state-of-the-art developmental test bed for all industry, university, 

and laboratory developments under its new Renewable Systems Interconnection Initiative. 

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____________________________________________________________________________________ 

 

•	 Complete the first round of the long-term inverter operation evaluations and implement any 

significant inverter performance issues discovered in the long-term inverter operation evaluations 

into the PV system performance model. 

•	 Determine development protocols and tools needed to validate SAI stage-gate deliverables that 

target individual PV system components and the complete PV system. Initiate the 

implementation and validation of such protocols. 

•	 Provide PV inverter manufacturers with a facility to enhance performance capabilities and 

communication. 

•	 Continue to collaborate with SDSU to validate the MATLAB/Simulink inverter model and to 

validate high market-penetration issues that may exist between different topologies. 

1. Introduction 

A primary objective of Sandia’s inverter and BOS 

testing and evaluation program is to provide 

technical support to SAI’s Technology Pathway 

Partnership (TPP) participants and industry in 

developing commercial inverters/controllers that 

consistently meet the performance, reliability, and 

cost goals of the Solar America Initiative. The test 

protocols used will include a revised Distributed 

Energy Technologies Laboratory (DETL) grid-tied 

inverter test plan, the expanded Sandia/California 

Energy Commission (CEC) inverter test protocol, 

and a new system testing protocols developed as 

part of the Systems Test and Evaluation Project. A 

complementary objective is to assist the 

development and implementation of advanced 

concepts arising from inverter and controller and 

BOS research and development (R&D) projects. 

2. Technical Approach 

Inverter Performance Modeling 

A primary objective of this effort was to develop an 

inverter performance model applicable to all 

commercial inverters used in photovoltaic power 

systems. The model performance parameters are 

progressive in the sense that the accuracy of the 

model can be improved as more detailed test data 

become available. The initial inverter performance 

model parameters are derived from 

manufacturers’ specifications. Utilizing field 

measurements during system operation provides 

additional parameters and accuracy. Detailed 

performance measurements conducted by 

recognized testing laboratories provide further 

refinement of parameters used in the model. The 

inverter performance model is an empirical model 

that simply, but accurately, replicates the power 

delivery characteristics of the DC-to-AC inversion 

process. The inverters undergoing long-term 

operational testing provide additional operational 

characteristics of the inverter and can be 

implemented into the inverter performance model 

to better represent PV systems after long term 

operation. Three sites have been chosen to 

evaluate up to four inverters at each site. These 

sites are the Florida Solar Energy Center (FSEC), 

the Southwest Technology Development Institute 

(SWTDI), and Sandia’s DETL. Presently the longterm inverter test recharacterization evaluation has 

involved two inverters from the DETL. These 

inverters are popular residential utilityinterconnected PV inverters connected to enough 

PV to operate the inverter at rated power for a 

short duration each day. These inverters initially 

underwent a detailed laboratory characterization 

and after more than 2 years of outdoor operation 

the inverters are being brought in for a 

recharacterization of their performance. The 

information gathered from these inverters will be 

used to refine the inverter performance model and 

will be ultimately used in a system performance 

model. 

In addition, efforts to model the interaction of 

today’s inverter in high market-penetration 

situations are being simulated through the 

development of PV system models for use in 

power system simulations. Although useful in 

some circumstances, most simulations either 

resort to full switching models of the inverter, 

which are not suitable for high market-penetration 

case studies, or they do not model the maximum 

power point tracking (MPPT) and anti-islanding 

controls in sufficient detail to accurately simulate 

the performance and functionality of today’s 

inverters. To address these needs, we developed 

a computer model of a single-phase PV inverter in 

the MATLAB/Simulink environment. The model 

was designed to accurately represent the 

behaviors of a PV inverter that are most relevant 

at the system level, especially islanding detection 

and MPPT. Its primary value is thus to the power 

system engineer, and secondarily to the power 

electronics designer. 

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SAI/TPP and Industry Test Support 

The objective of this task is to assist SAI/TPP 

participants and industry to develop commercial 

hardware that consistently demonstrates service 

lifetimes consistent with the SAI objectives. One 

aspect of this is the completion of Phase 3 of 

DOE’s High Reliability Inverter Initiative. An 

additional, complementary objective is to assist in 

developing and evaluating advanced concepts 

arising from inverter R&D projects. These 

concepts may include changes in materials and 

designs, new standardized communication 

protocols, internal system or hardware 

diagnostics, alternative anti-islanding 

methodologies, new wide-band high-temperature 

switching devices, or “smart” power distribution 

controllers. Providing DOE with a test facility to 

analyze SAI state-gate deliverables is a necessity 

to fulfill the objectives set forth in the initiative. 

Furthermore, work by DETL continues to enable 

existing inverter manufacturers to develop and 

enhance performance, reliability, and power 

quality capabilities. The following are examples 

for each of the parameters under development by 

the various manufacturers. 

Performance enhancement examples: 

• Array utilization 

•	 Early/late and dynamic irradiance 

operations 

• conversion efficiency 

Reliability enhancements examples: 

• Heat mitigation 

• Component monitoring 

• Surge suppression 

Power quality enhancements examples: 

• Improved magnetics 

•	 Increased power factor at low power 

•	 Reduced anti-islanding perturbation. 

Codes and Standards Support 

The objective of this task is to assist in the 

development of commercial hardware that is fully 

compliant with all utility-interconnection standards 

and applicable safety codes. As a complementary 

activity, Sandia actively participates in PV-related, 

domestic and international codes and standards 

committees to assure that consensus information 

and requirements flow between the committees 

and the inverter industry and through the 

collaboration with BEW Engineering continue the 

effort to harmonize the International 

Electrotechnical Commission and UL utility 

interconnection standards and test procedures. 

PV Inverter and BOS Evaluation FY07 Work Plan 

Agreement Title FY 2007 

Budget ($K) 

Inverter/BOS Performance 

Modeling (SNL) 140 

SAI/TPP and Industry Test 

Support (SNL) 620 

Codes & Standards Support 

(SNL) 140 

Total 900 

3. Results and Accomplishments 

Inverter Performance Modeling 

SNL personnel have developed an inverter 

performance model applicable to all commercial 

inverters used in photovoltaic power systems that 

provides a versatile numerical algorithm that 

accurately relates the inverter’s ac-power output to 

the dc-power input. The model developed requires 

a set of measured performance parameters and 

the accuracy of the performance model is 

optimized by utilizing detailed performance 

measurements as conducted by recognized 

testing laboratories. Additionally, laboratory 

inverter performance data was used to assist in 

the implementation of the inverter performance 

model. With the implementation of the model into 

laboratory data acquisitions systems, a validation 

of the empirically derived inverter performance 

model can be validated against measured 

parameters. Controlled laboratory conditions 

assist in validating the inverter modeling tool that 

provides an indication of the ability for the device 

under test to utilize available PV and convert that 

available PV into usable ac power. The following 

are some of the significant accomplishments. 

•	 Completed implementation of inverter 

model (1/07) 

•	 Completed the implementation of 10 

inverter performance parameters using 

CEC inverter performance protocol results 

(03/07) 

•	 Initiated inverter model validation (06/07). 

The inverter model developed in 

MATLAB/Simulink environment has been 

completed and initial laboratory validation of the 

model has commenced in single-inverter condition 

and in multi-inverter condition. 

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•	 Completed the implementation of a single 

phase inverter model with MPPT and antiislanding functionality 

•	 Conducted the laboratory initial model 

validation test. 

SAI/TPP and Industry Test Support 

SNL’s DETL evaluations of inverters have focused 

on utility compatibility issues, array utilization 

issues, and reliability issues. A new UL 1741-

2005 requirement is for utility interconnected 

inverters and 240–volt-system inverter voltage 

measurements between L1-N and L2-N to survive 

an ANSI C62.45 surge. These new requirements 

have been difficult for several manufacturers to 

achieve and laboratory evaluations have assisted 

the PV industry in realizing these requirements. 

Today’s inverters do well in utilizing the PV array, 

but some have slight issues during low-irradiance 

conditions. Another issue is heat mitigation 

because inverters have inadequate heat sinks or 

because environmental element residue reduces 

heat sink thermal characteristics, which leads to 

heat buildup. The following are major results and 

accomplishments of the project for FY 2007. 

•	 Completed evaluations of two commercial 

PV inverters (06/07) 

•	 Completed evaluations of three residential 

PV inverters (09/07) 

•	 Completed evaluations of beta surge 

suppression circuits for both residential 

and commercial PV inverters (03/07) 

•	 Completed RUS PV system evaluations 

(09/07) 

•	 Completed draft development of a PV 

system protocol (05/07). 

Codes and Standards Support 

Laboratory evaluations conducted at SNL’s DETL 

provide a means to analyze the ability of utility 

interconnected PV inverters to adhere to utility 

interconnection requirements. Also, by 

participating in the National Electrical Code (NEC) 

review process, these evaluations help to review 

the implementation of required hardware. An 

integrated and collaborative approach is taken to 

address codes, standards, and related 

infrastructure development and issues related to 

solar installation. The development of codes and 

standards is essential for the success of SAI. The 

following are the major accomplishments: 

•	 Provided feedback to industry partners 

when developmental product failed to 

meet standard requirements 

•	 Provided input to the NEC Code Making 

Panel for Article 690 and 705. 

4. Planned FY 2008 Activities 

Inverter/BOS Performance Modeling and System 

Test Protocol Validation and Refinement 

Sandia will complete the validation of Sandia’s 

inverter and systems performance models at 

Sandia’s PV Systems Optimization Laboratory and 

will assist full inclusion of these models in the 

Solar Advisor Model analysis tool. Work will 

involve the following: 

•	 Validating the models by applying CEC 

inverter performance information 

•	 Compiling a database that will incorporate 

test protocols for SAI stage-gate reviews 

•	 Implementing SNL inverter performance 

model refinements 

•	 Assure proper inclusion of the inverter and 

systems performance models in DOE’s 

Solar Advisor Model analysis tool. 

As PV inverters and their connection to the utility 

grid proliferate, additional questions regarding high 

market penetration will arise and SNL plans on 

continuing its multi-inverter modeling efforts. 

Applied SAI and R&D Industry Support 

This task is geared toward the provision of 

developmental support and stage-gate evaluations 

of inverter and BOS improvements by TPP, 

participants in the SEGIS inverter initiative, and 

other industry development. The objectives are: 

•	 Validation of SAI TPP’s stage-gate 

deliverables and assistance to industry in 

developing commercial hardware that 

consistently demonstrates advanced 

operational functionality and performance 

consistent with the SAI goals 

•	 Development of a new set of evaluation 

protocols to support the development of 

new capabilities within the inverter and 

energy management system 

•	 Development of improved capabilities to 

collect field data on the performance of 

installed inverters and improvement of the 

linkage between field and laboratory data 

in reliability and system-life determinations 

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Support for Development and Implementation of 

Codes & Standards 

The objective of this task is to assist in the 

development of commercial hardware that is fully 

compliant with all utility-interconnection standards 

and applicable safety codes. Efforts will involve: 

•	 Participation in domestic and international 

PV-related codes and standards 

committees 

•	 Sandia analysis of developmental and 

production hardware for compliancy with 

all utility-interconnection standards and 

applicable safety codes. 

5. Major FY 2007 Publications 

M. Ropp and S. Gonzalez, “Development of a 

MATLAB/Simulink model of a single-phase gridconnected photovoltaic system,” Sandia National 

Laboratories, Albuquerque, NM SAND2007 

(2007). 

J. Ginn, D. Menicucci, J. Ortiz-Moyet, Primecore, 

Inc., T. Byrd, S. Gonzalez, and J. Blevins, Salt 

River Project, Phoenix, AZ, “Laboratory tests of 

IEC DER object models for grid applications”, 

Sandia National Laboratories, Albuquerque, NM 

SAND2007 (2007). 

D. King, S. Gonzalez, G. Galbraith, and W. 

Boyson, “Performance model for grid-connected 

photovoltaic inverters”, Sandia National 

Laboratories, Albuquerque, NM SAND2007 

(2007). 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2007 

($K) 

Northern Plains Power/ 

Dr. Michael Ropp 

Brookings, SD 

mropp@sdsu.edu 

Develop and report on an advanced 

inverter integrated control modeling 

concept..” 

50 

. 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Systems Testing and Evaluation 

PV Module and Array Testing 

Performing Organizations: Sandia National Laboratories (SNL) 

 National Renewable Energy Laboratory (NREL) 

Key Technical Contacts: M. A. Quintana (SNL), 505-844-0474, maquint@sandia.gov 

C. R. Osterwald (NREL), 303-384-6764, carl_osterwald@nrel.gov 

DOE HQ Technology Manager: Dan Ton, 202-587-4618, dan.ton@ee.doe.gov 

FY 2007 Budgets: $1,000K (SNL), $1,570K (NREL) 

Objectives 

•	 Provide module and array performance evaluations for Solar America Initiative (SAI) Technology 

Pathway Partnership (TPP) stage-gate evaluations and in support of the photovoltaic (PV) 

industry’s product development efforts. 

•	 Develop test protocols and performance models that support PV investments at the U.S. 

Department of Energy (DOE) as well as supporting industry and TPP progress. 

•	 Assess PV module and array reliability issues to quickly isolate, scientifically understand, and 

help industry mitigate module failure and/or degradation mechanisms. 

•	 Gather and analyze outdoor, long-term exposure data for candidate module technologies. 

•	 Develop new and improved module packaging designs that result in improved service lifetimes 

and reduced annual performance degradation. 

•	 Assist industry with developing new consensus standards and codes for module performance 

and/or qualification testing. 

•	 Characterize and provide models for PV module performance and reliability. 

•	 Measure degradation rates per year of both modules and systems using real-time testing. 

•	 Perform accelerated stress testing of modules following national and international standards for 

qualification and safety testing. 

Accomplishments 

•	 Tested world record performance of two production modules for SunPower having 19.8% and 

20.1% efficiency. 

•	 Provided baseline tests of Sanyo modules for GreenRay to support initial development in 

fulfillment of the GreenRay TPP. 

•	 Evaluated arrays from SunPower (evaluating the performance of glass antireflective coatings) 

and Advent (short-term performance/degradation tests). 

•	 Conducted performance tests to support the development of Emcore concentrating photovoltaic 

(CPV) modules. 

•	 Initiated efforts to conduct a soiling test for Evergreen Solar. 

Future Directions 

•	 Increase development and stage-gate testing in support of SAI TPP progress. 

•	 Increase module and array testing in support of reliability studies. 

•	 Include future work that may be carried out as part of the SAI. 

1. Introduction ingredient for product credibility and consumer 

confidence. In addition, a systems-driven 

One of the top research priorities identified by approach has been applied somewhat recently 

the PV industry year after year is module and used to identify technical improvement 

performance and reliability, as an essential opportunities, using the Solar Advisor Model 

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(SAM) for program planning. This approach has 

shown that a total system lifetime of 30 years 

and electrical output that stays within acceptable 

levels (e.g., no more than 0.5% to 1% annual 

degradation rates) are critical in order to 

produce the expected total kilowatt-hours of 

electricity over the system’s 30-year lifetime to 

meet DOE cost goals. Photovoltaic modules are 

the most important system component in terms 

of cost, performance, and reliability. Modules 

make up 55% to 65% of the total PV system 

price and costs and directly determine the 

overall system conversion efficiency. Therefore, 

this project addresses module reliability, 

packaging, performance, and characterization 

research and development (R&D), and is a joint 

effort between the National Renewable Energy 

Laboratory (NREL) and Sandia National 

Laboratories (SNL). The project continues to be 

an essential element of the PV R&D work in 

DOE’s Solar Energy Technologies Program 

(SETP). 

During the SETP peer review in October 2005, 

the feedback about the relevance of the work 

included “critical to the achievement of DOE 

goals ... [and] the development of sustainable 

PV markets,” “highly valuable to the U.S. PV 

industry,” “relevant to the DOE objectives by 

providing a combination of laboratory and field 

testing of PV modules,” and “by solving reliability 

problems, module life cycle costs are reduced, 

and thus the DOE goal of lowering system cost 

is supported." Also, this work is “a key element 

of the overall DOE program ... that 

complements other projects and is integral to 

overall program advancement [and] systems 

that perform to specifications over prolonged 

time periods show the value of PV as an energy 

source and lead to acceptance of the technology 

by utilities and other customers.” 

Numerical ratings given by the reviewers were 

the highest of all projects reviewed. 

2. Technical Approach 

The technical approach in this project consists of 

short-term and long-term outdoor module 

performance testing and characterization; 

selected outdoor stress testing (e.g., in highvoltage environments); accelerated indoor 

environmental stress testing (e.g., temperature, 

humidity); performance analyses, 

characterization, and modeling; failure and 

degradation analyses; and module packaging 

R&D (e.g., moisture ingress analysis and 

amelioration). These evaluations are performed 

to help mitigate failures and degradation and/or 

reduce module costs and improve performance. 

In order to conduct these testing, analyses, and 

module packaging investigations, NREL and 

SNL develop and apply advanced measurement 

techniques, diagnostic methods, and 

instrumentation. A key aspect of the overall 

approach is close interactions and collaborations 

with PV module manufacturers. The intent is to 

optimize the time and funding required when 

advancing module technologies from the 

prototype to the commercial production stage, 

with respect to meeting acceptable performance, 

reliability, and cost requirements. 

In FY 2007, the tasks were accomplished under 

four agreements, as shown in the table. 

Task Title 

(Module & Array Testing) 

FY 2007 

Budget 

(In-House) 

($K) 

Module & Array Testing (NREL) 1,940 

Task 1: Module Parameter 

Database (SNL) 140 

Task 2: Module/Array Degradation 

(SNL) 130 

Task 3: Testing & Modeling 

Protocols (SNL) 280 

Accelerated stress testing is done on 

developmental module designs, and typically 

comprises tests proscribed by several 

International Electrotechnical Commission (IEC) 

standards, such as damp heat, thermal cycling, 

hot spot endurance, and humidity-freeze cycling. 

Mechanical integrity tests such as hail impact, 

mechanical load, robustness of terminations, 

and junction box securement are also available. 

These tests can be performed in one or more of 

the standard module qualification or safety 

testing sequences, or individualized sequences 

may be employed while assisting a 

manufacturer with product development. This 

collaborative testing and feedback is performed 

for industry contacts (e.g., SunPower, GE) and 

subcontractor deliverables. In addition, needs of 

the SAI Technology Pathway Partnerships will 

be assessed when the agreements are in place, 

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and a plan developed for making the requisite 

measurements, in cooperation with SNL and the 

RESs. 

3. Results and Accomplishments 

Task 1 

Task 1 involves coordinating and facilitating the 

development of databases for module and array 

performance parameters needed by integrators 

for PV system design and energy modeling. The 

rapid growth of the PV industry has resulted in 

hundreds of module types and sizes (models) 

for inclusion in a publicly accessible database. 

As the industry grows, the testing and database 

function for commercial modules should 

transition to commercial testing laboratories. 

Likely commercial labs include Arizona State 

University’s Photovoltaic Testing Laboratory 

(ASU/PTL), the Florida Solar Energy Center 

(FSEC), the Southwest Technology 

Development Institute (SWTDI), and 

Underwriters Laboratories (UL). 

Task 2 

This task involves analyzing and documenting 

failure mechanisms and performance 

degradation rates observed during long-term 

field exposures of modules and arrays with 

accelerated thermal and humidity conditions, 

when possible. Field exposure is a critical 

prerequisite and the most defensible method for 

demonstrating module reliability and service 

lifetime. This task establishes reliability 

baselines and opportunities for improvement 

through a well-controlled long-term exposure in 

different climates. Partners in this effort include 

SNL, NREL, FSEC, SWTDI, module 

manufacturers, and system integrators. Activities 

in this task will emphasize field reliability 

assessments for SAI TPP participants. 

Task 3 

Task 3 involves developing testing protocols and 

associated modeling algorithms needed for 

energy-based system design, field installation 

and checkout, array performance ratings, longterm performance monitoring, and diagnosis of 

array degradation events. The array modeling 

algorithms are developed in conjunction with 

inverter and system modeling procedures 

addressed in the Inverter & BOS (Balance of 

System) Testing Agreement and the System 

Test & Evaluation Agreement, resulting in 

system testing protocols. 

FY 2007 Milestones 

•	 Established a Test and Evaluation (T&E) 

Working Group, coordinate lab activities, 

and provide T&E support for DOE TPP 

participants: A Test and Evaluation 

document published by DOE was 

implemented as the basis for establishing 

the T&E Working Group. Two meetings 

were conducted in FY 2007. The first was to 

establish the lab working group and the 

second was a seminar provided to TPP 

technical monitors to establish test and 

evaluation strategies for implementation in 

TPP stage-gate validations. (SNL, NREL) 

•	 Provided outdoor module performance 

characterization and module database 

parameters for TPP participants: Progress 

in awarding TPP contracts minimized the 

amount of TPP testing that occurred during 

FY 2007. Baseline testing of Sanyo 

modules and surge tests of inverter 

packaging were performed for GreenRay’s 

module scale inverter development under 

the TPP awarded in FY 2007. 

•	 Initiated a new method for accelerated array 

field-aging for SAI TPP participants: A 

reliability program was formulated to 

address issues related to field-aging. The 

methodology will use information from 

fielded system, models, and accelerated 

aging efforts to model system reliability; this 

effort will be implemented in FY 2008. (SNL, 

NREL, SWTDI, FSEC) 

•	 Developed techniques to diagnose reliability 

issues caused by cell/solder bond/laminate 

stresses resulting from the introduction of 

TPP-driven module technologies: Reliability 

needs voiced by the PV community drove 

the creation of a rigorous strategy to 

address the reliability of photovoltaics in FY 

2007. Development of this strategy included 

research in methodologies and approaches 

that are being considered. 

•	 Implemented and verified SNL’s module and 

array testing and analysis protocols at 

ASU/PTL, FSEC, and SWTDI. 

Module & Array Testing Task (NREL) 

This agreement provided for real-time outdoor 

testing on modules and small grid-tied systems, 

and accelerated indoor and outdoor module 

stress testing. These activities are performed at 

the NREL Outdoor Test Facility (OTF) in 

collaboration with PV module manufacturers 

(industry partners), SNL, and Underwriters’ 

Laboratories (UL) in order to improve industry 

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prototypes before large-scale commercialization, 

and/or to characterize real-world performance of 

modules representing various technologies (thinfilm, silicon, etc.). 

Work on this project was adversely affected 

during the fourth quarter of FY 2007 by the 

initiation of a construction project to expand the 

OTF on the NREL permanent site. The 

laboratories used for many of these activities 

had to be evacuated. 

FY 2007 Milestones 

•	 Deliver system performance reports & 

analyses to module manufacturers (quarterly 

reports transmitted to Uni-Solar, SunPower, 

First Solar, Schott Solar) 

•	 Obtain UL accreditation at NREL for 

IEC61215 (qualification) and IEC61730 

(safety) testing of modules (testing 

agreement with UL through a CRADA could 

not continue due to internal changes at UL) 

•	 Support test and analysis for thin-film, hot & 

humid module exposure contracts, and other 

in-house and contract research (testing 

performed for Advent Solar, SunPower; new 

Shell CIGSS system installed) 

•	 Evaluate modules in Performance and 

Energy Ratings Testbed (PERT), replace 

with new technologies as needed; report on 

feasibility of using PERT data for module 

energy ratings to draft IEC standard 

(completed) 

•	 New environmental chamber installed at 

OTF to replace 25-year-old unit 

•	 Procurements for four new environmental 

chambers initiated using FY 2007 General 

Equipment funds. 

4. Planned FY 2008 Activities 

Efforts described in this activity will be folded 

into other projects (specifically, a Reliability 

project and the PV Test and Evaluation project) 

in FY 2008. The goal is to develop and apply 

methodologies to test, evaluate, and assess the 

reliability of components in PV systems. This 

information will be used to develop a reliability 

model. Specific objectives are as follows: 

•	 Provide an increasing amount of effort in 

Test and Evaluation to support product 

development by SAI TPP participants. 

•	 Perform stage-gate validations as needed to 

assist DOE in the administration of TPP 

contracts. 

•	 Install new environmental chambers at the 

OTF. 

5. University and Industry Partners 

During FY 2007, university partners included New Mexico State University (SWRES) and the University of 

Central Florida. PowerMark Corporation and Sunset Technologies (IEC TC-82 Secretariat) subcontracts 

were continuations of existing subcontracts that maintain a U.S. presence in the international PV 

standards and product certification efforts. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity FY 2007 

($K) 

Sunset Technologies, 

H. Barikmo 

Mesa, AZ 

HBARIKMO@aol.com IEC TC-82 Secretariat support 40 

PowerMark Corp., S. 

Chalmers 

Mesa, AZ 

SteveChalm@aol.com PowerMark Corp. PV certification support 40 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Systems Testing and Evaluation 

PV Module Failure Analysis 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 DOE Golden Field Office (DOE/GO) 

Key Technical Contacts:	 Carl Osterwald (NREL, Primary Contact), 303-384-6764, 

carl_osterwald@nrel.gov 

Tom McMahon (NREL), 303-384-6762, tom_mcmahon@nrel.gov 

DOE HQ Technology Manager:	 Dan Ton, 202-586-4618, dan.ton@ee.doe.gov 

FY 2007 Budgets:	 $340K (NREL) 

Objectives 

•	 Investigate photovoltaic (PV) module reliability through understanding of module failure modes. 

•	 Continue thin-film module hot-and-humid exposure testing subcontracts for one more year. 

•	 Provide failure analysis for Solar America Initiative (SAI) Technology Pathway Partnership (TPP) 

participants as needed. 

Accomplishments 

•	 Developed interfacial measurement technique of layer adhesion inside modules. 

•	 Completed thin-film hot-and-humid module exposure subcontracts. 

•	 Continued investigating slow degradation of short-circuit current in crystalline-Si module. 

Future Directions 

•	 This activity has been reorganized into other activities for FY 2008 under the PV-Module 

Reliability Program. 

•	 Perform post-exposure testing on thin-film hot-and-humid exposure modules from Florida Solar 

Energy Center (FSEC) and Texas A&M University (TAMU). 

1. Introduction 

This agreement addresses module reliability, and 

thereby system-level performance, by elimination 

of failure modes that are identified from a failure 

investigation. If a failure mode that greatly limits 

module lifetime is subsequently eliminated, the 

levelized cost of electricity is also improved by 

increasing the total energy delivered. The U.S. 

Department of Energy Solar Energy Technologies 

Program (SETP) peer review in October 2005 

stated that this work “...uses experimental and 

analytical methods to improve the reliability of PV 

modules. The approach includes analysis to 

understand failure mechanisms...” and “highlights 

how [t]he approach includes interaction with the 

academic community and PV module 

manufacturers.” This work was given numerical 

ratings that were the highest of all projects 

reviewed. 

2. Technical Approach 

Working as closely as possible with module 

manufacturers, laboratory personnel attempt to 

identify the causes of failures observed during 

testing at the national laboratories or in modules 

deployed in the field. Analyses can also be 

initiated upon request of manufacturers or TPP 

participants. Detailed analyses of any observed 

failures are performed as needed, using existing 

resources at the national laboratories. Diagnostic 

tools for these analyses are available in two 

divisions of the National Center for Photovoltaics. 

They include an indoor infrared imaging camera, 

light and dark I-V measurements, quantum 

efficiency measurements, core sampling, polymer 

and adhesion diagnostics, surface analysis, and 

laser spot scanning. Findings are then 

documented and reported, including any 

recommendations for changes to module designs 

that might eliminate problems. A multiyear 

investigation into an observed slow degradation of 

short-circuit current in encapsulated crystalline-Si 

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modules is currently underway and will be 

continued under this agreement. Other 

degradation or failure mechanisms are identified 

as new prototypes are submitted for evaluation or 

field problems arise for manufacturers, who often 

come to the laboratories for help. Work under this 

agreement also includes development of 

diagnostic techniques and methodologies needed 

to address specific failures that are identified with 

new modules. 

Failure analysis results are communicated to the 

respective module manufacturers, who are then 

responsible for implementing any manufacturing 

changes to alleviate problems. For the TPPs, 

specific requirements may be negotiated into the 

cooperative agreements with the recipients. 

The FSEC and TAMU hot-and-humid thin-filmmodule exposure subcontracts provide for another 

year of funding for this existing program, initiated 

as part of the former Thin-Film Partnership 

Program, during which time a decision will be 

made about continuing these projects, recompeting them, or both. 

PV Module Failure Analysis FY 2007 Work Plan 

Agreement Title FY 2007 

Budget ($K) 

PV Module Failure Analysis 340 

3. Results and Accomplishments 

Work on this project was adversely affected during 

the fourth quarter of FY 2007 by the initiation of a 

construction project to expand the Outdoor Test 

Facility (OTF) at the National Renewable Energy 

Laboratory (NREL). The laboratories used for 

many of these activities had to be evacuated. 

Milestones: 

•	 Investigation of slow short-circuit current 

degradation in crystalline-Si encapsulated 

modules was continued (09/07) 

•	 A new measurement technique for polymer 

interfacial adhesion in PV modules was 

developed and documented (05/07) 

•	 No requests for testing or failure analyses 

from SAI/TPP participants were received 

during FY 2007 (09/07). 

A significant accomplishment under this project 

was the development of a measurement technique 

that allows characterization of the strength and 

durability of various interfaces within many types 

of PV modules. The key element is a device that 

measures torque as a function of twist angle on 

circular core samples (see Fig. 1). Analysis of 

modules exposed to ultraviolet (UV) radiation 

indicated that the interface between ethylenevinyl-acetate (EVA) encapsulation and crystallineSi top surfaces is degraded significantly, while 

adhesion at rear-side interfaces is not degraded. 

Adhesion of polymers is a key factor for protecting 

PV cells when packaged inside modules. 

Fig. 1. Example torque measurement of interfacial 

adhesion of EVA polymers to crystalline-Si cells. 

The long-term exposure experiment of crystallineSi cells encapsulated in module packages reached 

a total UV exposure dose of 4750 Mj/m2

 of metalhalide illumination (equivalent to about 17 years of 

outdoor UV exposure at the NREL OTF site). 

Careful periodic measurements of short-circuit 

current have indicated that degradation vary 

according to manufacturer and cell technology, 

and a thermal degradation of Si cell p-n junctions 

has been eliminated as a cause (see Fig. 2). 

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Fig. 2. Loss of short-circuit current versus UV 

exposure dose for a crystalline-Si cell technology 

with TiO2 antireflection coating. 

After 1-year extensions, the thin-film module -andhumid-exposure subcontracts at both TAMU and 

FSEC have ended and the program was evaluated 

internally at NREL. Part of the evaluation included 

a site visit to FSEC just prior to the end of 

operation. The evaluation identified a number of 

shortcomings with both testing activities: 

•	 Principal investigators (PI) were not familiar 

with PV system design practices, especially 

the National Electric Code 

•	 PIs misunderstood the program intent and 

objectives 

•	 Changes recommended after an earlier site 

visit were ignored and not implemented 

(FSEC) 

•	 A principal investigator was lost at the 

midpoint of a subcontract (TAMU) 

•	 There was no appreciation for the possible 

impact of hurricanes (NREL). 

As a result of these shortcomings, the real-time 

data collected by both subcontractors has not 

been of sufficient quality to allow continuous 

monitoring as originally intended. The FSEC data 

could not be used because graduate students 

periodically changed corroded load resistors, 

which invalidated month-to-month comparisons. 

At TAMU, the former PI was the only person who 

understood the data acquisition system, which 

caused a number of problems when he left the 

university. Thus, module degradation will have to 

be determined when exposed modules are 

returned to NREL for retesting. 

Module testing in diverse or harsh climates is still 

recognized as an important priority, and the 

lessons learned here need to be applied to future 

testing activities. 

4. Planned FY 2008 Activities 

As a result of the new structuring of the DOE PV 

reliability program, module failure analysis has 

been incorporated into a number of new program 

agreements. Any future equivalents of the hot & 

humid exposure program have been allocated to 

outdoor testing activities under the Sandia PV 

program. 

5. Major FY 2007 Publications 

G.J. Jorgensen and T.J. McMahon, “Accelerated 

and outdoor aging effects on PV module interfacial 

toughness and shear strength”. Proceedings of the 

2007 DOE Solar Program Review Meeting, 

Denver, CO, (2007). 

G.J. Jorgensen and T.J. McMahon. “Accelerated 

and outdoor aging effects on photovoltaic module 

interfacial adhesion properties.” Progress in 

Photovoltaics: Research Applications (in press) 

(2008). 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 

2007 

($K) 

Florida Solar Energy 

Center 

Neekanth Dhere 

Cocoa, FL 

dhere@fsec.ucf.edu 

Thin-Film Hot-and-Humid Exposure: 

continuation of research initiated under the 

former Thin-Film Partnership Program to 

expose thin-film PV modules in a humid climate 

and measure and observe degradation 

145 

Texas A&M University 

Jeff Haberl 

College Station, TX 

jeffhaberl@tees.tamu.edu 

Thin-Film Hot-and-Humid Exposure: 

continuation of research initiated under the 

former Thin-Film Partnership Program to 

expose thin-film PV modules in a humid climate 

and measure and observe degradation 

65 

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________________________________________________________________________________ 

 

____________________________________________________________________________________ 

Systems Testing and Evaluation 

Photovoltaic System Evaluation and Optimization 

Performing Organization: Sandia National Laboratories (SNL) 

Key Technical Contact: M.A. Quintana (SNL), 505-844-0474, maquint@sandia.gov 

DOE HQ Technology Manager: Dan Ton, 202-587-4618, dan.ton@ee.doe.gov 

FY 2007 Budgets: $950K 

Objectives 

•	 Provide research and development support for DOE Solar America Initiative (SAI) participants 

and the photovoltaic (PV) industry to investigate advanced PV system concepts, manufacturing 

methods, and deployment strategies that improve performance, reliability, and cost, and to 

accelerate deployment. 

•	 Provide SAI stage-gate validations to assist DOE administration of SAI programs. 

•	 Operate a versatile fully instrumented PV System Optimization Laboratory (PV-SOL) for system 

and inverter performance and aging research. 

•	 Develop, validate, and apply new testing and analysis procedures, based on energy production, 

needed to verify and optimize the performance and reliability of PV systems. 

•	 Provide manufacturers, integrators, and software developers accurate comprehensive test data 

required to model and verify system, module, and inverter performance. 

•	 Coordinate a multi-site research effort to evaluate the long-term field-aging behavior of inverters 

in collaboration with inverter manufacturers and the Florida Solar Energy Center (FSEC), 

Southwest Technology Development Institute (SWTDI), and BEW Engineering. 

•	 Collect and analyze system installation and operation information in collaboration with established 

system integrators to establish performance and cost baselines. 

Accomplishments 

•	 Completed a draft protocol on field testing for confirmation by the PV community and 

implementation for SAI validations. 

•	 Evaluated the performance of system configurations for PV manufacturing companies Advent and 

SunPower at Sandia National Laboratories’ (SNL’s) Photovoltatic Systems Operations Laboratory 

(PV-SOL), which has the capability to perform detailed performance and long-term reliability 

research on 14 separate nominally 3-kW PV systems with multiple array/inverter combinations. 

•	 Characterized additional modules and arrays; SNL’s “module database,” used by integrators and 

in commercial PV system design software, now includes more than 200 commercial modules and 

12 arrays. 

•	 Participated in a draft comparison of array-performance models to understand differences and 

best practices. 

Future Directions 

•	 Continue the concerted effort to enhance and document PV systems and inverter performance 

and reliability research through coordinated efforts in the PV-SOL with module and inverter 

manufacturers, integrators, FSEC, SWTDI, and BEW Engineering. 

•	 Develop a comprehensive reliability program that captures the need of evolving business models 

for greater reliability of data and information. 

•	 Develop improved field data-acquisition and analysis procedures for monitoring PV-system 

performance to provide more meaningful system performance indices. 

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1. Introduction 

The PV System Evaluation and Optimization 

activities at SNL are closely linked to the needs 

of manufacturers and system integrators. These 

activities provide laboratory and field-test 

information needed to establish the performance 

and reliability status of current PV systems and 

also identifies opportunities for improved system 

design and component integration in nextgeneration systems. These activities are key to 

meeting DOE Solar Energy Technologies 

Program multi-year program plan targets and 

objectives of the Solar America Initiative 

Program, as well as the goals of the U.S. PV 

industry roadmap. As such, the System 

Evaluation and Optimization Project is the focal 

point within the DOE Solar Program where the 

technical issues of PV component 

manufacturers, system integrators, and users 

converge. 

2. Technical Approach 

Major research activities for FY 2007 included 

detailed module, array, inverter, and system 

research aimed at understanding and improving 

the performance, reliability, and cost of fully 

integrated PV systems. This research was 

conducted using the capabilities and expertise 

associated with SNL’s PV System Optimization 

Laboratory, PV-SOL. 

The PV-SOL is equipped to accurately evaluate 

the energy production from 14 separate 3-kW 

grid-tied systems using different combinations of 

the latest vintage modules and inverters. 

Energy flow in and out of all system components 

is continuously recorded, providing detailed 

performance characteristics, as well as longterm aging characteristics for both inverters and 

arrays under all weather conditions. The 

performance of the PV array associated with 

each inverter has been fully characterized and 

modeled, providing real-time calculation of the 

expected DC energy from the array for 

comparison with measured DC input to the 

inverter. 

PV-SOL activities include the following: 

•	 Validation of PV-system performance 

models and development of better 

performance indices. 

•	 Serving as a testbed for new “system 

manufacturing” concepts and structural 

designs. 

• Characterization of balance-of-system 

components supporting product 

development. 

•	 Improvement of performance or diagnostic 

field tests. 

•	 Investigation of array utilization, inverter 

maximum power point tracking (MPPT), and 

efficiency based on energy production. 

•	 Improvement of start-up, shut-down, MPPT, 

and performance-monitoring algorithms for 

inverters. 

•	 Thermal modeling (operating temperature) 

for inverters versus meteorological 

conditions. 

•	 Investigation of array shading and 

orientation. 

•	 Optimization of design, components, 

setpoints, and controls for off-grid and hybrid 

systems. 

•	 Evaluation of PV-system monitoring and 

control hardware and software. 

•	 Development of wireless, low-cost, accurate 

data acquisition hardware. 

•	 Characterization of prototype components 

supporting industry product development. 

FY 2007 Work Plan 

Tasks FTEs 

In-house 

Funding 

($K) 

System Testing Protocols 0.5 140 

SAI/Industry Test Support 2.0 560 

System Reliability & Safety 0.7 200 

Fig. 1. PV-SOL: Six new PV array technologies 

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Fig. 2. PVSOL: Fully instrumented inverters in 

continuous system performance test 

3. Results and Accomplishments 

The FY 2007 technical milestones and related 

accomplishments for the System Evaluation and 

Optimization Project are listed below by project 

subtask. 

•	 Documented field-testing protocol for array, 

inverter, and system performance for SAI 

Technology Pathway Partnership (TPP) 

participants— 

A field test protocol was drafted in FY 

2007. This protocol was written to 

provide a standardized procedure for 

evaluating SAI systems as a validation 

of stage-gates for SAI. The protocol will 

be further iterated and formalized in FY 

2008. 

•	 Conducted field survey of PV array safety 

status after years of operation— 

Array safety issues have been compiled 

as a part of test protocol development 

and development of a comprehensive 

reliability program to be conducted in FY 

2008. 

•	 Calculated annual AC-energy system 

efficiencies for multiple sites using best-inclass technologies as SAI benchmarks— 

This is an ongoing activity that has 

provided multiple applications for the PV 

Solar Advisor Model and SAI TPP 

planning purposes. 

•	 Documented advanced concepts for 

wireless irradiance and temperature sensing 

and “smart” diagnostics— 

This activity was investigated and 

terminated after industry counterparts 

fell short on development efforts. 

4. Planned FY 2008 Activities 

In FY 2008, the Photovoltaic System Evaluation 

and Optimization Project will be folded into 

System Modeling, PV System Reliability, and PV 

System Test and Evaluation projects. 

The major activities for FY 2008 include: 

•	 Initiation of a comprehensive reliability 

program that begins a rigorous effort to 

define 1) system reliability issues in the field, 

2) development of system availability needs, 

3) designs for system maintainability, and 4) 

supply chain requirements to establish and 

support system reliability metrics. 

•	 Initial requests and fulfillment of SAI TPP 

stage-gate validations from PV 

manufacturing companies GreenRay, 

Amonix, and Soliant. 

•	 Development of additional tracker test 

capabilities for concentrating-PV and flatplate PV-system evaluations. 

•	 Continue efforts to improve general 

performance model for inverters, including 

characteristics associated with DC/AC 

efficiency, MPPT effectiveness, start-up, 

shut-down, thermal foldback, and power 

factor. 

5. University and Industry Partners 

The Southwest Region Experiment Station of New Mexico State University and the Florida Solar Energy 

Center at the University of Central Florida partnered in the project’s research activities during FY 2007. 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Systems Testing and Evaluation 

Regional Experiment Stations 

Performing Organizations: Sandia National Laboratories (SNL) 

DOE Golden Field Office (DOE/GO) 

Key Technical Contact: M.A. (SNL), 505-844-0574, maquint@sandia.gov 

DOE HQ Technology Manager: Dan Ton, 202-587-4618, dan.ton@ee.doe.gov 

FY 2007 Budget: $1,750K (DOE/GO) 

Objectives 

•	 Meet Solar Program Annual Operating Plan objectives and milestones by teaming with the 

national laboratories. 

•	 Assure that education, training, outreach, and technical support required to accelerate the rate of 

the nation’s PV deployment efforts are available and effectively implemented to support growth of 

the PV market. 

•	 Provide leadership and support to the industry and the national labs for: (1) systems, module, and 

inverter testing; (2) creating and implementing procedures, codes, and standards for quality, safe, 

and cost-effective installed systems; (3) hardware certification; and (4) addressing system 

engineering issues observed in fielded systems. 

•	 Provide technical support to DOE, national laboratories, and industry in the execution and validation of stage gates for the Solar America Initiative (SAI) Technology Pathway Partnerships (TPP). 

Accomplishments 

•	 Completed the first-year requirement of a 3-year contract and began the second-year 

requirements. 

•	 Conducted product testing, system evaluations, and research and development (R&D) activities 

that related to cutting levelized cost of energy, increasing system efficiency, and cutting initial 

costs of PV systems; particularly as required by SAI participants. 

Future Directions 

•	 Lead technical outreach Tiger Teams to Solar America Cities and Showcases. This work, led by 

Southwest Regional Experiment Station (SWRES), builds on successes with Forest City Military 

Communities, City of Tucson, and City of Austin . 

•	 Continue participation in the test and evaluation process of fielded systems for TPP stage-gate 

testing, as well as general system benchmarking of performance, cost, and reliability 

characterization by SWRES. 

•	 Participate in the development and dissemination of codes and standards for solar technologies, 

reducing barriers and increasing responsiveness to stakeholders. 

•	 Support codes and standards development. 

•	 Escalate testing in support of reliability studies being initiated at the national labs. 

•	 Increase data collection from field installations to better capture costs, system availability, and 

system maintainability. 

1. Introduction a university affiliation: University of Central 

Florida for SERES and New Mexico State 

The Southeast Regional Experiment Station University (NMSU) for SWRES. In addition, each 

(SERES) and Southwest Regional Experiment station has university-level capabilities, which 

Station (SWRES) are partners in the DOE Solar have been developed to provide systems and 

Energy Technologies Program. Each station has component-level research and development 

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(R&D) for DOE, the U.S. photovoltaic (PV) 

industry, other government agencies, and PV 

consumers. The work of each is aligned with 

activities conducted in the Technology 

Development and Advanced Materials and 

Devices portion of the DOE PV Subprogram. 

Regional Experiment Station (RES) goals are to 

provide value-added technical support to the 

Solar Program that effectively and efficiently 

meets the R&D needs identified by the DOE’s 

Annual Operating Plan and the Solar America 

Initiative (SAI), and to pursue targets specified 

by the DOE Solar Program Multi-Year Program 

Plan. 

RESs have contributed to the DOE National PV 

Program for 2 decades. This work is integrated 

into DOE’s Annual PV Program plan and is 

highly collaborative. Throughout the years, RES 

support has been an integral part of program 

projects, such as: 

• Module reliability R&D; 

•	 Inverter and balance-of-system development; 

•	 PV systems engineering; 

• Domestic PV applications; 

•	 System evaluation and optimization (especially for fielded system); 

•	 PV system analysis; and 

•	 Education and codes and standards 

development. 

Collaborations with SNL, National Renewable 

Energy Labatory (NREL), National Center for 

Photovoltaics (NCPV) R&D partners, and 

industry counterparts are focused on reducing 

systems costs, improving system reliability, 

improving system performance, improving 

system safety, and removing barriers to 

deployment, thereby promoting market growth. 

2. Technical Approach 

Work conducted by the RESs builds on 

expertise with fielded systems that is unique to 

the DOE Solar Program. Expertise acquired as a 

result of extensive field investigations provides a 

system perspective that is the foundation for 

solving technical problems that are barriers to 

widespread deployment. A large volume of 

requests from the PV industry, as well as the 

alignment to an evolving U.S. PV Program, 

provides continuous feedback on the relevance 

of RES activities. The following tasks describe 

the technical approach to applying the RES 

capabilities in pursuit of DOE and industry 

needs. 

2.1. PV Systems Assistance Center 

The Photovoltaic Systems Assistance Center 

(PVSAC) is a virtual laboratory comprising 

engineers and staff from both SWRES and 

SERES. The objective of the PVSAC is to 

become a national one-stop resource for publicpolicy support, design reviews, specialized 

training and training materials, and technical 

field-support activities. This enables the PVSAC 

to be a major gateway for technical education, 

training, and outreach to the U.S. PV 

community. 

The PVSAC has impaneled a board of advisors, 

with which it develops comprehensive strategic 

plans for PVSAC prioritization of activities. The 

board will provide annual review of progress and 

revise PVSAC planning to reflect changes in the 

needs of the U.S. PV community. 

PVSAC will play an important role in the execution and validation of Technology Pathway Partnership stage gates. As an independent thirdparty evaluator, the RES will provide DOE with 

assistance in ensuring that stage gates are met, 

in order to extend cooperative agreements. 

Stage gates can include system performance 

testing, outdoor exposure tests, code compliance investigations, and hosting fielded systems. The Regional Experiment Stations will 

provide design and test support directly to the 

TPPs during product and system development 

activities. 

2.2. Infrastructure Development 

Infrastructure development consists of training, 

design review and approval, and codes and 

standards development activities. Training 

occurs through multiple venues and in several 

subject areas. A key issue with fielded systems 

is poor installation (including design practices, 

code compliance, and safety), which has been 

addressed consistently by RES staff. Activities 

began with providing training to interested 

parties and have evolved to the creation and 

establishment of a National Installer Certification 

Program, an independent activity that the 

Regional Experiment Stations were instrumental 

in creating. Similarly, training of inspectors and 

installers now is evolving to a system of “training 

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the trainers,” providing an opportunity to reach a 

greater audience and minimize investment. 

Technical assistance to the industry and users 

has resulted in an evolving design review and 

approval standard that provides guidance for 

uniform designs and system documentation. 

This activity promotes a level of quality accepted 

and practiced by other industries that provide 

recognized products in successful markets. 

Development of codes, standards, and certification addresses compliance to a set of prescribed recommendations to assure quality and 

safety. The proactive approach of Regional 

Experiment Stations provides the opportunity to 

guide development of codes and standards that 

assure performance, quality, and safety without 

creating a cost burden for the industry. Capabilities for test and certification of hardware are 

used to create and apply a uniform set of standards in a recognizable format that instills consumer confidence. Certification also is the basis 

for assuring optimal awards from government 

incentive programs. 

2.3. Long-Term Component Testing 

The Regional Experiment Stations provide 

unique and severe environments for stressing 

PV components and systems. Initially, they 

provided long-term exposure in hot/dry and 

hot/humid climates for stressing PV modules 

deployed in a field-like setting. More recently, a 

similar approach has been begun to study the 

long-term performance of inverters in field-like 

outdoor configurations. Increased reliability 

needs voiced by labs and industry will increase 

demand for this type of testing; for both commercial products and the development of 

prototypes/samples. 

Additional activities include placing the inverters 

in a distributed-generation scenario to address 

issues associated with controls and generator 

interactions. Both of these activities are complementary to the Sandia National Laboratories 

(SNL) baseline tests, which establish initial component performance parameters while seeking 

to identify degradation rates for different 

technologies. 

3. Results and Accomplishments 

•	 Conducted PV Systems Assistance Center 

inaugural board meeting Oct. 17, 2006. The 

PVSAC Board meeting notes were adapted 

into a revised PVSAC Implementation Plan 

(PVSAC-IP) during the last quarter and 

circulated for review. The final draft is in 

progress, awaiting the return of comments 

from some reviewers. 

•	 The Southwest Technology Development 

Institute (SWTDI) and PVSAC developed 

the test requirements (labor, hardware, 

travel) for testing and evaluation (T&E) 

support of the SAI TPP award winners. 

•	 SWTDI and Florida Solar Energy Center 

(FSEC) staff participated in a “Tiger Team” 

evaluation of the National Zoo, Washington, 

DC, as the zoo facilities and grounds were 

being renovated. 

•	 FSEC worked with BP Solar to provide an 

unbiased perspective in its training program. 

Kevin Lynn gave a presentation using 

materials taken from the PV Installers Class 

and used it to teach students about installation and the National Electric Code (NEC) as 

it relates to some of BP system designs. 

•	 FSEC worked with Palm Harbor Homes to 

install a PV system on a manufactured 

home for display at the International Builders 

Show (Feb. 2007), at the Orange County 

Convention Center, Orlando, Florida. 

•	 PVSAC participation with Sacramento Municipal Utility District (SMUD) concluded in 

March with the final revision and validation 

of the SMUD Performance Index software. 

Special validation was required for the oneaxis tracking algorithms used to validate 

performance of the utility’s larger arrays. 

•	 SWTDI staff participated in the 2007 Solar 

Decathlon kickoff meeting in Washington, 

DC. SWTDI reviewed electrical drawings and 

specifications submitted by all 20 participating university teams for safety, compliance 

with the NEC and general quality of design. 

•	 SWTDI staff performed acceptance testing 

of the new 30-kW PV system at the City of 

Phoenix Pecos Park municipal building 

•	 SWTDI staff tested and provided a field 

rating for the 1-MW PV system at the 

Sonoma Mountain Village, Rohnert Park, 

California. In addition to rating the system, 

SWTDI engineers used this test to develop 

and revise the test protocols for arrays and 

inverters that will be put forward for consensus adoption by the T&E group in May. 

•	 The FSEC conducted 80 system design 

reviews supporting small system manufacturing. 

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•	 Presented PV/NEC day training for more 

than 1700 participants—including code 

officials, electricians, and inspectors—from 

throughout the country. 

•	 FSEC performed a round-robin test between 

FSEC’s Spire Sun Simulator 660, Spire’s 

multipulse and long-pulse simulators, and 

indoor and outdoor module performance 

testing at NREL. Results were described in 

the report “Round Robin Testing of PV 

Modules 2006 Between FSEC, Spire Corp. 

and NREL.” 

•	 The Fronius inverter originally part of the 

ILTF failed in Q2 of 2007 and will be sent 

back to Sandia for failure analysis. 

•	 Six ILTF monitoring systems continue 

operation online, collecting data and realtime displays of performance on the Web 

throughout FY 2007. 

•	 Construction was completed on the 18-kW 

modular, prototype, PV parking structure on 

the NMSU campus. SWTDI staff tested and 

provided a complete field rating for the new 

18-kW PV parking structure. 

•	 Several one-week classes, “Installing Photovoltaic Systems,” were conducted at FSEC 

during FY 2007, training more than 200 

installers. 

•	 SWTDI provided support for Underwriters 

Laboratories (UL) investigation of module 

grounding problems and concerns. 

•	 SWTDI has begun working closely with a 

major U.S. manufacturer of nonresidential, 

architectural, industrial, and institutional 

metal buildings. 

•	 The FSEC was the first organization to have 

its PV program accredited by ISP (Institute 

for Sustainable Power, Quality). Accreditation requires periodic review and auditing. 

•	 The FSEC is working with several partners 

to investigate PV-array structural attachment 

and integration methods. 

•	 Two inverters (SMA, Fronius) were removed 

from ILTF testing and sent to Sandia 

National Laboratories for the second round 

of full characterization. 

•	 Kaneka of Japan has finalized plans to send 

modules to the FSEC for long-term performance evaluation of its thin-film modules. 

•	 The SWTDI has developed a wireless, lowcost pyranometer for integration into the 

systems monitoring capabilities already 

available in most commercial inverters. 

4. Planned FY 2008 Activities 

•	 Continue to support development of Codes 

and Standards. 

•	 Continue to support market transformation 

activities with needs that capitalize on RES 

strengths. 

•	 Increase SAI TPP validation test to assist 

DOE administration of cooperative agreements with industry. 

•	 Increase field-test and outdoor-validation 

activities in support of developing reliability 

enhancement methodologies with the 

national labs. 

5. FY 2007 Special Recognitions 

John Wiles, New Mexico State University, was 

elected a fellow of the American Solar Energy 

Society. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/ Title of Research Activity FY 2007 ($K) 

Florida Solar Energy Center 

Kevin Lynn 

Bob Reedy 

Cocoa, FL 

klynn@fsec.ucf.edu 

reedy@fsec.ucf.edu 

PV System Research 875 

Southwest Technology 

Development Institute 

Andrew Rosenthal 

Las Cruces, NM 

arosenth@nmsu.edu 

PV System Research 875 

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____________________________________________________________________________________ 

 

Component Testing and Evaluation 

Solar Radiometry and Metrology
 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

 DOE Golden Field Office (DOE/GO) 

Key Technical Contact: Daryl R. Myers (NREL), 303-384-6768, daryl_myers@nrel.gov 

DOE HQ Technology Manager: Dan Ton, 202-586-000, dan.ton@ee.doe.gov 

FY 2007 Budgets: $750K (NREL) 

Objectives 

These objectives relate to accurate measurements and models relating to the levelized cost of electricity 

(LCOE), efficiency, dollars per peak watt ($/Wp), and other metrics associated with the Solar Energy 

Technologies Program’s (SETP) goals and/or the Solar America Initiative (SAI): 

•	 Provide accurate broadband and spectral optical radiation measurements to evaluate solar 

conversion device and system performance consistent with the ISO 17025 accredited scope. 

•	 Establish and maintain optical radiation calibration references traceable to national and 

international standards for calibrating broadband and spectral radiometers and light sources. 

•	 Maintain technical support to the consensus standards community (e.g., American Society for 

Testing and Materials, International Lighting Commission) in developing industry standards. 

•	 Perform research and development to establish and/or reduce uncertainties in optical radiation 

measurements related to the solar energy conversion research and development and industry. 

•	 Transfer technology to the solar conversion industry related to solar and optical measurements 

and data for the design or evaluation of solar conversion technologies. 

Accomplishments 

These support LCOE, efficiency, $/Wp, and other metrics associated with accurate measurements of 

known uncertainty and appropriate consensus standards for performance testing and reporting: 

•	 Supported the NREL Pyrheliometer Comparison (NPC), September 24-27, 2007, verifying the 

stability of NREL’s reference absolute cavity radiometers with respect to the World Radiometric 

Reference (WRR). 

•	 Performed 26 spectral and 405 solar broadband radiometer calibrations for NREL, industry, and 

academic partners. 

•	 Performed on-site spectral classification of 10 industry and two NREL flash solar simulators with 

respect to ASTM E-927 spectral classification standard, using NREL’s unique radiometer system. 

•	 Analyzed five sources of solar radiation resource data, reported observed differences between 

data sets of up to 25% in an American Solar Energy Society (ASES) conference paper. 

•	 Jointly with a South African colleague, evaluated a passive radiometer system to separate global, 

direct, and diffuse solar components; reported results in a Society for Photo-Optical 

Instrumentation Engineers (SPIE) technical conference paper. 

•	 Provided technical input to generate or revise/update five ASTM and CIE standards on solar 

reference spectra, materials degradation testing, and photovoltaic (PV) performance testing. 

Future Directions 

•	 Identify means of deriving spectral distribution information from broadband data, such as Typical 

Meteorological Year data, to address impacts on emerging high-efficiency PV technologies. This 

effort addresses needs in the SAI advanced technologies area. 

•	 Expand the evaluation of variations among multiple solar radiation data sources used for design 

and performance benchmarks. 

•	 Develop techniques to reduce uncertainties in solar and broadband measurements based on new 

and innovative reference sources or detailed radiometer characterization. 

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1. Introduction 

The Solar Radiometry and Metrology task 

provides traceable optical radiation measurements 

that support NREL’s Photovoltaic (PV) 

Measurements and Characterization and 

Reliability tasks, the PV industry, and academic 

partners. The task maintains ISO 17025 

accreditation levels for optical radiometry 

associated with the NREL accreditation scope. We 

maintain a traceable optical measurement 

chain from the World Meteorological Organization 

World Radiometric Reference (WMO/WRR) and 

the National Institute of Standards and Technology 

(NIST) spectral irradiance scale. NREL’s optical 

standards calibrate broadband and spectral 

radiometers that measure natural and artificial 

source optical radiation during PV performance 

testing. Calibrated sensors provide accurate data 

for developing, testing, and validating broadband 

and spectral models used by the research and 

industry communities. We provide technical input 

to national and international consensus standards 

organizations generating standard test methods 

important to the solar industry. Our knowledge of 

solar radiation resource data, instrumentation and 

measurement techniques, and applications is 

shared or transferred to SETP program 

researchers, the solar industry, and academia. 

2. Technical Approach 

a. Maintain the stability of the NREL solar 

radiation reference (absolute cavity 

radiometers) 

b. Execute high-quality, detailed radiometric 

calibrations for broadband and spectral 

radiometers to meet NREL research and PV 

industry needs 

c. Participate in national and international 

consensus standards development by 

contributing technical expertise, data, and 

analysis, where appropriate 

d. Provide technical information on solar 

radiation resource data and applications to 

meet research and industry needs 

e. Transfer technology in this area to other 

researchers and industry via publications such 

as conference papers and presentations. 

Items a and b require regular experimental and 

routine operations at the NREL Solar Radiation 

Research Laboratory and Optical Metrology 

Laboratory; interactions with research, industry, 

subcontractor, and academic contacts to meet 

their needs; management of the physical 

reference and test instrumentation; database 

management of results and reports; and delivering 

reports of results to requestors. Items c through e 

require maintaining state-of-the-art knowledge of 

solar and optical radiation measurement 

techniques, data, applications, and technical 

issues. We conduct and publish research results 

based on available and newly developed solar 

radiation research in house, and in technical 

exchanges with contacts in this scientific field. We 

respond to technical requests though discussions 

and sharing of technical publications. The 

following table shows the approximate level of 

support for formal agreements within the FY 2007 

Annual Operating Plan for this task. 

Agreement Title 

FY 2007 

Budget 

($750K) 

Module and Array Testing 200 

Cell and Module Performance 150 

T&E Technical Coordination 100 

System Analysis and Modeling 50 

Benchmarking and Design Support 

Database 

50 

Market, Value, Policy Analysis 50 

CSP System Analysis 75 

Solar Resource Characterization 50 

PV, thermal, concentrating, 

daylighting, solar industry 

technology transfer, as needed(a) 

25 

(a)Not an official agreement; industry technology transfer is 

based on requests received. 

In addition, Technical Partnership Agreements are 

used as a vehicle to address industry needs 

requiring relatively more resources and costsharing with requestors. 

3. Results and Accomplishments 

3.1 NREL 2007 Pyrheliometer Comparison 

The NREL Pyrheliometer Comparison (NPC) 2007 

verified the stability of NREL’s reference absolute 

cavity radiometers with respect to WMO/WRR. For 

reference radiometers, NREL participated with 23 

other organizations such as SNL, the European 

Union Joint Research Center at Ispra, the National 

Aeronautical and Space Administration, and the 

National Oceanic and Atmospheric Administration. 

Reference absolute cavity radiometers were 

compared, establishing the stability of NREL’s 

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WMO/WRR factor to better than 0.1%. Figure 1 

shows the setup for participating cavity 

radiometers. Figure 2 shows that the stability of 

NREL’s reference absolute cavity radiometer AHF 

23734 with respect to WRR is known with a 

precision of 0.06%. 

Fig.1. Sample of the absolute cavity radiometers 

at NPC 2007, Sept. 24-27, 2007. 

Fig. 2. NPC 2007 results for NREL’s reference 

absolute cavity radiometer AHF 23734 showing 

the WRR factor to be 0.9977 ± 0.0006, or ±0.06%. 

This activity is required to maintain the ISO 17025 

accreditation scope for the NREL Measurement 

and Characterization task PV reference cell and 

PV reference module calibrations. 

3.2 Broadband and Spectral Radiometer 

Calibrations 

The task carried out three Broadband Outdoor 

Radiometer Calibration (BORCAL) events and the 

resulting calibration of 405 broadband solar 

radiometers traceable to WRR. 

As of FY 2007, all current and historical BORCAL 

reports since 2001 are available on the Solar 

Radiation Research Laboratory (SRRL) Web site 

at www.nrel.gov/aim/borcal.html, as shown in 

Figure 3. Absolute cavity radiometer reference 

data for each event is also available for research 

purposes. 

Fig. 3. Broadband radiometer calibration reports 

and reference data from 2001 to the present are 

available for download on the SRRL Web site. 

We executed two biannual calibrations of 13 

NREL spectroradiometers (26 calibrations in all) 

traceable to NIST spectral irradiance standards. 

The Measurements and Characterization Task 

reference PV cell and module calibrations uses 

these spectrometers under the scope of the ISO 

17025 accreditation received by that task. They 

also aid in establishing spectral mismatch factors 

and characterize the natural sunlight and light 

sources used in PV, solar thermal, concentrating 

PV, and daylighting solar technologies. 

3.3 Flash Solar Simulator Spectral Classifications 

At industry’s request, NREL performed spectral 

classifications of 12 flash and continuous solar 

simulator systems. Requestors included Spire 

Corp., Shell Solar, Evergreen Solar, First Solar, 

Newport/Oriel Corp., and the Florida Solar Energy 

Center (FSEC). The unique Pulse Analysis 

Spectrometer System (PASS) developed at NREL 

is used to make these measurements and to 

regularly classify all NREL solar simulators used in 

the PV Measurements and Characterization Task. 

These data help identify and troubleshoot spectral 

mismatch and drift issues with industry and NREL 

solar simulators. Figure 4 is an example of a 

classification result for the FSEC Spire 660 solar 

simulator used to certify PV module performance 

for the State of Florida. 

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conference held August 24-28, 2007, in San Diego 

California (see the publications section). 

3.5 Solar Resource Databases and Modeling 

We undertook an investigation into the differences 

between five of the most popular sources for these 

data (NASA Surface Solar Energy [NASA SSE], 

European Solar Data [SoDa], Swissmeteo 

Meteonorm, Candian RetScreen, and the U.S. 

National Solar Radiation Data Base [NSRBD]). We 

found that, at a single site, we are able to observe 

differences of many tens of percent. Figure 6 

compares monthly mean daily totals of solar 

radiation from the NASA SSE, SoDa, and 

Meteonorm CD-Rom. Differences of up to 25% 

occur between the three data sets. Many similar 

examples are shown in our ASES conference 

paper discussing the results and issues 

associated with the differences (see the 

publications section). 

6 

Fig. 4. April 2007 spectral classification results for 

the FSEC Spire 660 flash solar simulator with 

respect to the ASTM E-927 classification standard, 

using NREL’s PASS spectrometer system. 

3.4 Radiometric Instrumentation Research 

With a colleague from the Kwa-Zulu Natal 

1 2 3 4 5 6 7 8 9 10 11 12 

University in Durban, South Africa, we installed an 

innovative passive radiometer system for 

separating the global, direct, and diffuse irradiance 

components. The Zonal Exposure to Broadband 

RAdiation, or ZEBRA, shading band has regularly 

spaced perforations to alternately shade and 

expose the sensor, producing output similar to that 

MMDT kWh m-2 day-1 5 

4 

3 

2 

1 

0 of the rotating shadowband system, but at 

intervals of lower frequency and longer duration. Month Figure 5 shows a sketch of the system and a 

typical signal profile. 

Fig. 5. Sketch of ZEBRA installation and typical 

clear day signal profile. 

A DOE Science Undergraduate Laboratory intern 

from Northwestern University, Sarah Braden, 

developed techniques to accurately reconstruct 

continuous global, direct, and diffuse irradiance 

profiles. She applied techniques developed by 

Long and Ackerman [1] in identifying clear-sky 

profiles. She also investigated shade/unshade 

calibrations for pyranometers based on the 

system. This work resulted in a conference paper 

detailing promising results for the Optical Modeling 

and Measurements for Solar Energy Systems 

Potsdam-MET Potsdam SoDa Potsdam SSE 

Fig. 6. Monthly mean solar irradiance data for 

Potsdam, Germany, from three different solar 

databases (NASA SSE, SoDa, Meteonorm). 

We reevaluated the cloud cover modifier algorithm 

for the all-sky version of the Bird clear-sky model, 

published in 2006. We used two additional clearsky models and NSRDB cloud cover data to 

compare with modeled solar data. We used Iqbal’s 

Parameterization C and Gueymard’s REST2 to 

show that a simple polynomial cloud cover 

modifier generates a realistic time series of hourly 

solar radiation data from a reasonable clear-sky 

model and available cloud cover data. Figure 7 

compares time series of the original NSRDB data 

for a typical site with the Iqbal Parameterization C 

model cloud modified results. Similar results were 

obtained with the REST model. Details were 

published in a paper for the Optical Modeling and 

Measurements for Solar Energy Systems 

conference held August 24-28, 2007, in San 

Diego. 

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Fig. 7. Comparison of hourly time series for 

NSRDB data (bottom) and clear-sky model with 

cloud cover modifier applied for a typical NSRDB 

site. The model produces realistic time series 

data. 

3.6 Consensus Standards Activities 

We provided technical input and draft language for 

multiple documents at ASTM committee meetings 

for Committee G03 on Weathering and Durability, 

and for CIE technical committee TC2-17 on 

revising CIE-85 on Solar Spectral Irradiance. We 

also reviewed, commented upon, and voted on 10 

new and revised ASTM Committee E-44 

standards on PV performance testing. 

3.7 Technical Transfer 

We responded to more than 120 technical 

requests from over 100 entities on the following: 

solar radiation instrumentation and calibration; 

broadband and spectral solar models (e.g., Bird, 

REST2, DISC, SMARTS2, SEDES2, and 

SPCTRL2); data obtained using RetScreen, 

Meteonorm, NASA SSE, NSRDB, TMY2, 

WMO/WRR, SoDa, and SWERA, as well as DOE 

EnergyPlus weather data and SRRL baseline 

measurement data; and applications (e.g., 

PVWatts, SOLAR ADVISOR, PVFORM). We 

reviewed 15 journal articles at the request of 

editors of five different professional journals. In 

addition, the task leader organized and chaired 

two technical conferences on solar and optical 

radiation in FY 2007: 

•	 Council for Optical Radiation Measurements 

Annual Technical Conference: Optical 

Radiation Standards Development for 

Industry, in conjunction with CIE-USA and 

NIST, May 8-11, 2007, Gaithersburg, 

Maryland. 

•	 Optical Modeling and Measurements for Solar 

Energy Systems, August 24-28, 2007, in San 

Diego, California, a part of the SPIE Photonics 

2007 Symposium. 

We also contributed three book chapters on solar 

radiation measurements and modeling (see the 

publications section). And we initiated a costshared Technical Services Agreement (TSA-07­

130) with SPIRE Corp. to provide the company 

with a PASS solar simulator classification 

spectrometer for internal use. The TSA is 

scheduled to conclude by the middle of FY 2008. 

All of the technical accomplishments described 

above reflect the completion of the five milestones 

listed in the following table. 

FY 2007 Milestone Level Accomplished 

Perform NPC 

verification of 

NREL WRR 

traceability 

5 Sept. 28, 2007 

Calibrate 13 NREL 

spectroradiometer 

systems 

5 Sept. 30, 2007 (26 

calibrations) 

Calibrate broadband radiometers 

for PV industry and 

NREL 

5 Aug. 30, 2007 (405 

calibrations) 

Characterize NREL 

and industry flash 

solar simulators 

5 Sept. 30, (15 total 

characterizations) 

Prepare technical 

publications and 

conduct technology 

transfer 

4 Sept. 30 

(organized two 

conferences, 5 

conf papers, 3 

book chapters, 2 

draft standards) 

4. Planned FY 2008 Activities 

•	 Conclude Spire Corp. TSA-07-130 with 

delivery of PASS system to Spire for internal 

use by March 2008 

•	 Investigate and develop techniques for 

deriving solar spectral distribution data from 

broadband solar radiation data (such as TMY2 

hourly data) to support SAI activities in 

emerging PV technologies 

•	 Research the possibility for a high-accuracy 

detector-based spectral irradiance calibration 

system to reduce uncertainty in spectral 

calibrations 

•	 Conduct NPC 2008 to maintain WRR 

traceability and ISO 17025 accreditation 

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•	 Conduct spectral and broadband radiometer 

calibrations in support of SETP program 

needs. 

5. FY 2007 Special Recognitions 

In conjunction with Spire Corp. (TSA-07-130; 

innovation report No.07-43), asserted copyright on 

NREL PASS operational software. 

6. Major FY 2007 Publications 

D. Myers, “General Cloud Cover Modifier for Clear 

Sky Solar Radiation Models,” Optical Modeling 

and Measurements for Solar Energy Systems, 

Conference Vol. 6652, SPIE, Bellingham, WA 

(2007). 

D. Myers, ”Relative Performance of Multiple Solar 

Radiation Resource Assessment Data Sources,” 

Solar 2007, Annual Conference of the American 

Solar Energy Society, Cleveland OH, July 7-12, 

Boulder CO: American Solar Energy Society 

(2007). 

D. Myers, Government Participation in Consensus 

Standards Development, OMB Circular A-119, 

Council for Optical Radiation Measurements 

Annual Technical Conference, Optical Radiation 

Standards Development for Industry, in 

conjunction with CIE-USA and NIST, May 8-11, 

2007, Gaithersburg, MD. 

M.J. Brooks, S. Braden, and D. Myers, “Passive 

Separation of Global Irradiance into Direct Normal 

and Diffuse Components,” Optical Modeling and 

Measurements for Solar Energy Systems, 

Conference Vol. 6652, SPIE, Bellingham WA 

(2007). 

C. Gueymard and D. Myers, “Performance 

Assessment of Routine Solar Radiation 

Measurements for Improved Solar Radiation and 

Radiative Modeling,” Solar 2007, Annual 

Conference of the American Solar Energy Society, 

Cleveland, OH, July 7-12, Boulder, CO: American 

Solar Energy Society (2007). 

S. Wilcox et al., “Completing Production of the 

National Solar Radiation Data Base for the United 

States,” Solar 2007, Annual Conference of the 

American Solar Energy Society, Cleveland, OH, 

July 7-12, Boulder, CO: American Solar Energy 

Society (2007). 

D. Myers, “The Solar Resource,” Solar Hydrogen 

Generation, Toward a Renewable Energy Future, 

K. Rajeshwar, S. Licht, and R. McConnell, eds., 

Springer (2008). 

C. Gueymard and D. Myers, Solar Radiation 

Measurements: Progress in Radiometry for 

Improved Modeling in Modeling Solar Radiation at 

the Earth's Surface: Recent Advances, V. 

Badescu, ed., Springer (2008). 

C. Gueymard and D. Myers, “Validation and 

Ranking Methodologies for Solar Radiation 

Models,” Modeling Solar Radiation at the Earth's 

Surface: Recent Advances, V. Badescu, ed., 

Springer (2007). 

7. References 

1. C.N. Long and T.P. Ackerman, “Identification of 

Clear Skies from Broadband Pyranometer 

Measurements and Calculation of Downwelling 

Shortwave Cloud Effects,” Journal of Geophysical 

Research, vol. 105, no. D12, 15609-16626 (2000). 

8. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal 

Investigator 

Location/e-mail Description/Title of Research 

Activity 

FY 

2007(a) 

($K) 

Cost Share* 

($K) 

Spire Corp. 

Harvey Serrez 

Bedford, MA 

HSerreze@spirecorp.com 

NREL designed Pulse Analysis 

Spectrometer System for internal 

applications, quality control of flash 

simulator designs, TSA-07-130 

20 

20 + purchase 

of equipment 

(30) 

(a)To be concluded in the 2nd quarter of FY 2008. 

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____________________________________________________________________________________ 

PDIL Infrastructure, Engineering, and Integration 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contacts:	 Brent Nelson (NREL, Primary Contact), 303-384-6407, 

brent_nelson@nrel.gov 

Steve Robbins (NREL), 303-384-6400, steven_robbins@nrel.gov 

Robert White (NREL), 303-384-7802, robert_white@nrel.gov 

DOE HQ Technology Manager:	 Marie Mapes, 202-586-3765, marie.mapes@ee.doe.gov 

FY 2007 Budgets: $1,750K 

Objectives 

•	 Develop, Improve, and implement process integration standards. 

•	 Provide project management for securing capital equipment to go into the Process Development 

and Integration Laboratory (PDIL). 

•	 Provide infrastructure development for facilities and for the installation of equipment. 

•	 Develop an integrated software infrastructure within the PDIL that enables secure data access for 

National Center for Photovoltaics (NCPV) personnel and research partners. 

•	 Work with core research teams to develop research partnerships with external collaborators, 

including making the PV industry aware of the PDIL in Web sites and by other means. 

Accomplishments 

•	 Provided installation support for installing the silicon cluster tool, including replacing the entire 

gas-handling hardware and the installation of specialty gas line infrastructure. 

•	 Provided project management support leading to the competitive procurement of a molecular 

beam epitaxy (MBE)-type of deposition chamber for copper indium (gallium) diselenide (GIGS) 

material, a central robotic transfer chamber, and ancillary deposition chambers for metals, 

transparent conducting oxides (TCOs), and cadmium sulfide (CdS). 

•	 Provided project management and engineering development for the design of an automated 

chemical bath deposition system for CdS growth. 

•	 Provided project management support leading to the procurement of an atmospheric processing 

platform, which includes ink jet printing and spray jet deposition of metals and semiconductor 

materials. 

•	 Provided project management and engineering development for the design of processintegration-compatible measurement and characterization equipment developed at NREL, 

including resonance-coupled photoconductive decay (RCPCD), photoluminescence (PL) imaging, 

and a special spectroscopic ellipsometry chamber; integrated this equipment into a central robotic 

transfer chamber along with a sputtering/etching chamber and a chamber for studying plasma 

enhanced chemical vapor depositions (PECVD). 

•	 Provided project management support leading to the procurement of stand-alone processintegration-compatible measurement and characterization equipment, including Auger electron 

spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy 

(SEM), atomic force microscopy (AFM), a wet chemistry workstation, a reflectometer, an optical 

processing furnace, and a Semilab tool. 

•	 Provided project management and engineering development in the design of a CdTe platform 

capable of fully processing a CdTe device. 

•	 Provided project management and engineering development in the design of a silicon wafer 

replacement platform. 

Future Directions 

•	 Complete the acquisition and hardware installation of the equipment listed above. 

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•	 Complete the development of the data infrastructure for the data feeding into, and being 

generated by, the equipment listed above. 

•	 Assist the core groups in developing cooperative agreements for research to be performed with 

the equipment listed above or to be supplied under these agreements. 

1. Introduction 

The National Center for Photovoltaics has been 

working to develop a collaborative research facility 

where established and start-up photovoltaic (PV) 

companies, as well as potential university 

partners, can work with NREL scientists and 

engineers to gain the knowledge they need to 

further their respective PV technologies. The 

ultimate goal is to get the right teams of people 

working with the best equipment possible to try to 

answer the most important questions in a 

particular technology. Toward that end, we have 

built a new building and developed a set of design 

standards for equipment to populate the space. 

This equipment will be used in research that 

includes polycrystalline thin-films, thin silicon film, 

atmospheric processing of contacts and absorber 

materials, and a variety of characterization tools to 

support a spectrum of PV roadmap technologies. 

Integration standards include the establishment of 

a maximum substrate size and shape, the form 

factor of a platen that accommodates a variety of 

samples, a fixed sample transfer height, a 

standard chamber interface that allows modular 

techniques to be readily reconfigured between 

platforms, and a mobile sample transfer pod that 

enables intertool transport of samples between 

platforms in a controlled ambient. We are also 

developing software and data integration schemas 

that allow powerful software tools to be used with 

full security. Finally, we have a process with 

which to assess proposed activities within the 

collaborative facility and to ensure that proper 

facility and equipment resources are allocated, 

along with bringing together the best skill sets to 

accomplish project goals. 

The purpose of the process-integration project is 

to develop an infrastructure that will allow 

researchers to gain new knowledge that is 

difficult—if not impossible—to obtain with existing 

equipment. This difficulty is due, in part, to the 

state of the NCPV’s existing tool set, which either 

lacks sufficient in situ or real-time measurement 

capabilities or lacks access to analytical or 

subsequent processing capabilities, where the 

sample remains in a controlled environment 

between measurements and/or steps. Integration 

of the existing tool set is virtually impossible 

because of the wide variety of sample sizes used 

and the nature of the existing equipment. 

Therefore, the process-integration project is 

involved in developing new infrastructure 

implementing a core set of standards that make 

possible an integrated collection of techniques. As 

NREL, industrial, and university staff collaborate to 

define, construct, and use specific technology 

platforms, this will accelerate the growth of the PV 

knowledge base and help to move many PV 

technologies forward. 

2. Technical Approach 

The first step in integrating various techniques 

within and between platforms is to develop 

standards for the common interface and transport 

elements. Integrating a diverse set of tools 

requires a “universal” maximum substrate size and 

shape to be held in a platen. The platen’s size 

and shape drive the requirements for the entire 

design. The various core activities within the 

NCPV have set, by consensus, the maximum 

substrate size that the platen can handle to be 

approximately 6 in. x 6 in. This size supports the 

silicon PV industry, which has both a “6-inch 

square” protocol in multicrystalline Si and a “6-inch 

round” protocol in single-crystalline Si. It also 

more than adequately supports the other 

technological areas studied by the NCPV with a 

commercially viable area. 

Various platen designs will be needed to 

accommodate several different substrates, such 

as soda-lime glass, high-temperature glass (e.g., 

Corning 1737), crystalline wafers (e.g., of silicon, 

germanium, or gallium arsenide), and thin 

stainless steel, ceramic, and exotic materials. The 

platen is a 7-in. x 7-in. square with holes centered 

along each edge for alignment purposes. 

Individual deposition, processing, and 

characterization techniques will be integrated via 

one of several different modes. Ideally, 

characterization techniques will be used for realtime analysis of deposition and processing 

techniques. The next best solution is in situ 

diagnostics (in the original place, but not real-time 

data). 

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When neither of these integration modes is 

possible, techniques will be integrated by 

transferring samples from one location to another 

either via intratool or intertool sample transport. 

Intratool transport is the movement of samples 

between techniques on the same platform. The 

actual transfer mechanism will typically be a 

robotic transport mechanism in a central chamber, 

but it could be a linear track. The intratool transfer 

height is the Semiconductor Equipment and 

Materials International (SEMI) standard of 1.1 m 

above the floor. 

Intertool transport is the movement of samples 

between techniques when those techniques do not 

share a direct connection. The techniques could 

be in a stand-alone tool or a part of a larger 

platform. The sample is moved from one platform 

into a pod, which is sealed and disconnected from 

that platform before being wheeled to another 

platform, where the process is reversed. The 

transfer ambient within the pod can be either an 

atmosphere of ultra-high-purity inert gas or high 

vacuum. 

This intertool transport is similar to the Standard 

Mechanical InterFace (SMIF) used by the 

integrated-circuit (IC) industry to enclose and 

transport wafers between 200-mm tools, or the 

newer Front-Opening Unified Pods (FOUPs) used 

on 300-mm tools. One of the keys to the success 

of the IC industry was the creation of these minienvironments, in which the industry significantly 

reduced the contamination of wafers between 

processing steps. While SMIFs and FOUPs are 

typically operated with particulate-free, dry air, our 

initial pods will operate under high vacuum using a 

battery-powered ion pump. Thus, they will go 

beyond limiting particulate contamination to 

limiting molecular contamination (e.g., reactions of 

surfaces with oxygen or water vapor). Our microenvironment also allows us to integrate equipment 

without requiring clean-room facilities. The use of 

intertool transport in a high-vacuum ambient on 

such a large sample is a unique capability. 

A final integration mode is to make some of our 

techniques modular so that they can be moved 

between platforms. All chambers connecting to 

platforms will use a standard 10-in. metal sealed 

vacuum flange (Conflat®), centered at 1.1 m 

above the floor; therefore, a modular deposition, 

processing, or characterization technique can be 

docked on any given platform based on project 

needs, strategic priorities, and available space. 

Not all techniques can be modular, however, 

because size, sensitivity, complexity, and safety 

issues must be taken into account. 

Because very few techniques are commercially 

available that are integrated into a platform—and 

none that use our standard sample size or 

intertool integration scheme—participating core 

activities within the NCPV are defining their own 

platforms. They have been in consultation with 

their industrial and university collaborators with 

regard to the specific techniques built into each 

platform. NCPV management manages these 

plans within the scope of the NCPV strategic 

vision and available resources. The processintegration project works tactically to implement 

these plans according to integration standards. 

3. Results and Accomplishments 

In addition to the accomplishments listed in the 

summary, the following items were accomplished. 

A Web site was planned and is being 

implemented. It includes a voice-over to a PDIL 

animation explaining the conceptual 

implementation of process integration standards. 

Other animations explaining PV basics and 

specific research within various PV technologies, 

and defining integration terminology, are being 

developed. Currently, a home page has been 

posted at www.nrel.gov/pv/pdil.html. 

As soon as funding was allocated, the process 

began for hiring key PDIL staff. A senior research 

technician was hired who is helping with hardware 

installations of equipment. A controls engineer 

was also hired who is helping with automating 

hardware for sample motion, process control, and 

data logging. A software integrator was hired who 

is automating the secure databasing of diverse 

deposition, processing, and measurement data in 

collaboration with the scientific computing center, 

so that NCPV staff members have access to 

sophisticated software tools in order to analyze 

their data. 

Project management support of equipment 

acquisitions by the core research teams was 

provided by a variety of means, depending on the 

need: from engineering and design, to writing 

statements of work, to providing assistance in 

negotiating the acquisition process, to helping 

track expenses. Project management through 

NREL’s Earned Value Management System was 

also provided for the Science and Technology 

Facility Essential Capital Equipment. A relational 

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PDIL Infrastructure, Engineering, and Integration
database was developed to help meet the goal of 

tracking equipment to related data, such as 

support of the PV technology roadmaps, NCPV 

research plans, staffing, acquisition activity, 

potential industrial collaborators, and installation 

projects. The illustration depicts an entity 

relationship diagram showing how the data fit 

together. 

4. Planned FY 2008 Activities 

The activities planned for FY 2008 are to complete 

the tasks initiated in FY 2007, with added 

emphasis on software development and 

equipment installations. 

5. University and Industry Partners 

No cooperative research agreements were 

finalized within the PDIL during FY 2007. 

Because of the sensitive nature of the 

collaborations that the core research teams have 

been negating, these collaborations will be 

described in the annual reports for PV 

technologies or for measurement and 

characterization areas. 

Entity relationship diagram of the NCPV proposal and equipment management database. 

Photovoltaic R&D

Advanced Materials and Devices

PDIL Infrastructure, Engineering, and Integration

134
Market Transformation 

The Solar America Initiative (SAI) aims to make photovoltaic (PV) technologies, or solar 

electricity, cost-competitive with conventional forms of electricity from the utility grid by 2015. The 

U.S. Department of Energy is working to accomplish this goal through work at its national 

laboratories and public-private partnerships with industry, universities, states, municipalities, and 

nongovernmental organizations. When federal solar energy research began in the 1970s, the 

cost of electricity from solar resources was about $2.00 per kilowatt-hour (kWh). Technological 

advances during the last two decades have reduced solar electricity costs by more than 90% to 

about 20¢ per kWh, opening up new markets for solar energy. Due in large part to DOE-funded 

research, the cost of electricity from PV has dropped more than tenfold since 1976. 

In addition to the research and development efforts, DOE conducts complementary activities in 

the area of market transformation to lower market barriers and capitalize on large-scale solar 

deployment opportunities. Areas of market transformation work include: solar codes & standards, 

solar rating systems, education and training for installers, system financing options, and strategic 

stakeholder partnerships. DOE works with states, cities, non-profits, utilities, labor unions, and 

industry to address commercialization barriers and to educate solar stakeholders. DOE’s specific 

market transformation activities include: 

•	 Solar America Board of Codes & Standards: The board works to ensure the 

responsiveness, effectiveness, and accessibility of PV codes and standards to U.S. 

stakeholders at all levels. 

•	 Solar America Cities: Cities are both the nation’s population and electricity-load centers, 

so this activity focuses on increasing the adoption of solar energy technologies at the 

local level. Partner cities engage in cost-shared activities and receive technical 

assistance from DOE-identified experts to help overcome barriers to increased solar 

installations. 

•	 Solar America Showcases: These showcases are large, public projects that demonstrate 

solar energy technologies to the public. Partners receive technical assistance from DOEidentified experts to assist in the implementation of these projects. 

•	 State Technical Outreach: DOE partners with nongovernmental organizations to build 

relationships with and provide necessary information to decision makers to develop 

energy policies and programs. 

•	 Utility Technical Outreach: DOE partners with nongovernmental organizations to provide 

technical assistance and information to utilities to promote their acceptance and use of 

solar technologies. 

Achievements in Market Transformation for FY 2007 include: 

Codes and Standards 

•	 Led an industry forum with more than 100 attendees for Article 690 of the National 

Electrical Code (NEC) that resulted in 46 proposals and follow-up on public comments for 

inclusion into the 2008 NEC. 

Training and Certification 

•	 Published 52 issues of the Interstate Renewable Energy Council/SAI e-newsletter for 

1,700 subscribers 

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Technology Acceptance 

•	 Administered the photovoltaic and solar thermal exam twice, in March and September. At 

the end of fiscal year, 422 people were certified PV Installers and 56 Solar Thermal 

Certificants. 

Building Integration 

•	 Prepared for and conducted a successful 2007 Solar Decathlon university competition on 

the National Mall in Washington, DC., (October 2007). 

•	 Conducted building energy monitoring and computer modeling research on past Solar 

Decathlon houses to improve future contests, quantify the annual performance of the 

houses, identify areas of technical significance, and extend the education and outreach 

component of the competition beyond the 10 days on the National Mall. 

•	 Completed initial data gathering and analysis on state and local government financing of 

PV. 

Technical Partnerships 

•	 Prepared a report technically defining the solar energy opportunities for federally-owned 

Congressional office buildings in Washington, D.C. 

•	 Established strategic partnerships with 13 cities through a competitive funding 

opportunity and awarded a combined $2.5 million in financial assistance. 

•	 Planned the installation of a 1-megawatt PV system on the roof of the Orange County 

Convention Center (OCCC), in partnership with the Orlando Utilities Commission (OUC). 

Technical Outreach 

•	 Created a readily accessible database of current and previous years’ bills on energy, 

Solar State Legislation (www.ncsl.org/programs/energy/energypolicy.cfm). 

•	 Launched a Web site (www.statesadvancingsolar.org) that serves as a resource for state 

policy makers and decision makers interested in developing a solar program. 

•	 Released the "Solar Energy Technology and Policy Reference Guide." 

•	 Released “The Peer Matching Online Tool” (www.solarelectricpower.org/peer/) to share 

information and best practices to help all utilities improve their solar programs. 

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____________________________________________________________________________________ 

 

Codes and Standards 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Sandia National Laboratories (SNL) 

New Mexico State University (NMSU) 

Tucson Electric Power (TEP) 

Research Foundation of the State University of 

New York (SUNY–Albany) 

Key Technical Contacts:	 Holly Thomas (DOE Golden Field Office, Primary Contact), 

303-275-4818, holly.thomas@go.doe.gov 

Thomas Basso (NREL), 303-275-3753, thomas_basso@nrel.gov 

Ward Bower (SNL), 505-844-5206, wibower@sandia.gov 

DOE HQ Technology Manager:	 Charlie Hemmeline, 202-586-6646, charlie.hemmeline@hq.doe.gov 

FY 2007 Budgets:	 $1,998.6K 

Objectives 

•	 Provide consistent support for codes and standards development so that solar technology can be 

deployed on a large scale. 

•	 Improve the responsiveness, effectiveness, and accessibility of codes and standards in all 

markets (federal, state, local, and utility). 

•	 Address codes, standards, and related infrastructure development and issues. 

•	 Establish utility photovoltaic (PV) capacity credits models to reduce market barriers and promote 

solar-energy technologies acceptance. 

Accomplishments 

•	 NREL conducted a study on external disconnect switch (EDS) for grid-connected PV systems. 

•	 SNL led an industry forum (100+ attendees) for Article 690 of the National Electrical Code (NEC) 

that resulted in 46 proposals and follow-up on public comments for inclusion into the 2008 NEC. 

Final balloting included language from 40 of the proposals. 

•	 SNL provided the principal member of the Code Making Panel for National Electrical Code 

articles 690 and 705 (Utility Interconnected Systems), to create a common code basis for 

interconnecting to the grid. 

•	 SNL applied PV-related International Electrotechnical Commission (IEC) standards used in 

Europe and many other parts of the world. 

•	 SNL continued efforts to improve the test protocol for certification of inverters for PV applications. 

•	 NMSU established the Solar America Board for Codes and Standards (Solar ABCs) to coordinate 

and organize approaches to addressing market-transformation barriers. 

•	 NMSU developed Solar ABCs Web site (www.solarabcs.org), which includes solar standards and 

codes documents, to be used to disseminate information on the Solar ABCs programs. 

•	 NMSU organized PV Stakeholders Workshop at Solar Power 2007 Conference in Long Beach, 

California (September 2007); the workshop had approximately 250 attendees. 

•	 TEP published a draft model for valuing the effects of short-time-frame variations on solar-electric 

power availability using actual data from the Springerville Generating Station Solar System to 

address one of the utility market barriers to implementing PV. 

•	 SUNY–Albany prepared a catalogue of capacity credit metrics and evaluated and compared 

metrics with experimental case studies to assess solar capacity credit options. 

•	 NMSU, NREL, Sandia, SUNY–Albany, and TEP presented initial results at a PV Stakeholders 

Workshop, leading to a preliminary consensus about the options in each of the research topics. 

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____________________________________________________________________________________ 

 

Future Directions 

•	 NREL will continue providing leadership for, participation in, and coordination with, existing and 

new codes and standards assisting in removing market barriers for the broad use of PV systems. 

•	 SNL will work to improve domestic and applicable international standards primarily for 

interconnection and higher penetrations of PV to make way for widespread and increased 

deployment of PV systems in the United States. 

•	 SNL will provide validation of proposed codes, standards, and certifications, to avoid unnecessary 

requirements and costs. 

•	 Solar ABCs group will complete eight major studies on key codes and standards topics. 

•	 Solar ABCs group will conduct a formal gap analysis and work with PV stakeholders to analyze 

the current state of major codes and standards for solar energy and produce a prioritized list of 

codes and standards most urgently needed to remove barriers and promote deployment of solar 

technologies. 

•	 TEP will complete an analysis comparing traditional hourly sample analysis methods for electric 

load carrying capacity value with newly developed Demand Time Interval Method (DTIM) model 

results using actual hourly and shorter time-frame production data from two utility solar systems. 

•	 TEP will discuss comparative results with other electric utilities and publicize results at a national 

meeting. 

1. Introduction 

Codes and standards are the backbone of the 

success of the Solar America Initiative (SAI). The 

goal of the Codes and Standards project is to 

address the critical marketplace barriers to 

implementing photovoltaic (PV) systems. The 

project focuses on codes, standards, and certifications, as well as the agreements for net metering 

and system interconnection that prevent or slow 

the acceptance of solar technologies in the mainstream marketplace. 

To reduce or remove barriers to solar technology 

commercialization, this project also seeks 

consensus-based solutions to address the multiplicity of state and local jurisdictions to create 

more consistent standards and regulatory environment for PV. Examples of such barriers include an 

undue multiplicity of state and local jurisdiction 

requirements, which sometimes are lacking technical rationale or are based on inexperience and a 

misunderstanding of solar technologies. Further, 

historically there has been a lack of uniformity and 

transparency for standards requirements and best 

practices for PV products, systems, installation, 

acceptance, and interconnection with the electric 

utility grid. 

2. Technical Approach 

NREL and Sandia, to accomplish the goal of the 

project, conducted work that complemented 

additional work from a U.S. Department of Energy 

(DOE) Funding Opportunity Announcement (FOA) 

issued during fiscal year 2007 (FY 2007). The 

FOA requested assistance to provide the Solar 

Codes and Standards Working Group Leadership 

with ideas to support the development and 

adoption of specific capacity credit values or other 

utility-approved values for system benefits of PV. 

As a result of the FOA, three agreements were 

negotiated; these provide a coordinated approach 

for a Standards and Codes Working Group, and 

address standard methods to value PV. NREL and 

Sandia helped develop the scientific and engineering data needed to establish new and necessary 

codes and standards in the areas of interconnections, buildings, net metering, and PV ratings, by 

participating in the several recognized standards 

organizations that develop these codes to ensure 

that resulting regulations are compatible with PV 

requirements. 

Agreement Title FY 2007 

Budget ($K) 

NREL 350 

Sandia 250 

An Integrated Partnership to Create 

and Lead the Solar Codes and Standards Working Group 

1,200 

Utility Solar Generation Valuation 

Methods 100 

A Standard Definition of PV Capacity 

Credit 98.6 

2.1. Technical Support—NREL 

NREL staff provides leadership for and 

coordination of existing and new codes, standards, 

and entities that have jurisdiction in these areas. 

An integrated and collaborative approach is used 

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138
 

to address related solar codes, standards, and 

their adoption in conjunction with stakeholders. 

The NREL approach is predicated on broad 

consensus involving large numbers of individuals 

and entities. 

Coordinating codes and standards development, 

and revision, and providing technical assistance to 

adopting organizations forms the cornerstone of 

efforts to minimize redundancy and expenses to 

the industry. The coordination and collaborations 

result in expanded and new access for PV system 

installations in a broad set of scenarios, with fewer 

and less-restrictive barriers. NREL continues to 

provide expert technical assistance for DOE SAI 

solar codes and standards approaches, activities, 

and performing organizations; and also interfaces 

with SAI Technology Pathway Partnerships 

grantees. 

2.2. Technical Support—Sandia 

SNL’s approach focuses on reducing and 

eliminating barriers to the deployment of PV and 

other distributed systems. Sandia supports the SAI 

Technology Pathway Partnerships through testing 

and evaluation of codes, standards, and certifications-related functionality of new hardware and 

systems. The organization continues to use 

industry groups, such as the “Industry Forum,” and 

industry requests to identify and verify issues 

(through testing and analysis) that must be 

addressed. 

2.3. Standards and Codes Working Group— 

NMSU 

This 5-year Solar Codes and Standards Working 

Group Leadership project is designed to identify 

current issues, establish a dialogue among key 

stakeholders, and catalyze appropriate activities to 

support the development of codes and standards 

that facilitate the installation of high-quality, safe 

photovoltaic systems. 

2.4. Utility Solar Generation Valuation Methods 

Work began on this project to develop, test, and 

verify a method for accurately evaluating the capacity credit of time-variant power from solar generation. Traditional methods are compared with new 

methods to determine approaches that appropriately and fairly evaluate the value of solar generation to electric utilities. These results will lead to 

verified models that accurately assess the 

adequate compensation that solar owners provide 

to utilities. 

2.5. A Standard Definition of PV Capacity Credit 

This project is designed to establish a set of 

consensus-driven standard methodologies to 

quantify PV capacity credit that are acceptable to 

all concerned stakeholders, ranging from utilities 

and grid operators to the solar industry and related 

advocacy groups. The project also documents and 

describes the methodologies as a function of the 

relevant parameters affecting capacity, including 

PV generation, load demand, and market 

structure. 

3. Results and Accomplishments 

3.1. Technical Support—NREL 

NREL provided expert technical assistance in the 

development of SAI solar codes and standards, 

including: 

•	 Recommending development of a formal 

charter for the Solar America Board for Codes 

and Standards; the recommendation was 

implemented in September 2007. 

•	 Conducting a study on external disconnect 

switch (EDS) for grid-connected PV systems, 

evaluating the effects of evolving technology 

and standards and changing perceptions of 

the need for utility-accessible external disconnect switch (EDS) and related regulations 

(09/07). Although utility arguments for requiring utility-accessible EDSs for gridconnected PV systems might have been justifiable 5 or 10 years ago, today the EDS issue 

is effectively addressed by UL and IEEE 

standards. The utility-accessible EDS increasingly is viewed as redundant and unnecessary 

for residential and small-commercial PV 

systems with UL-listed inverters. 

•	 NREL staff members served as: The chair of 

the IEEE Standards Coordinating Committee 

21 (SCC 21) on Fuel Cells, Photovoltaics, Dispersed Generation and Energy Storage (http:// 

grouper.ieee.org/groups/scc21); officers for 

various individual SCC21 standards activities; 

and as an IEEE Standards Board Liaison to 

the DOE. A number of IEEE SCC21 standards 

were renewed or published And IEEE SCC21 

continually offers to sponsor new standards for 

PV per stakeholder priorities (09/07). 

•	 Participating in numerous state utility-commission workshops on interconnection and net 

metering (e.g., Washington, DC; Florida; Iowa; 

Illinois; Maryland; New Mexico; South Dakota; 

Utah) (09/07). 

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3.2. Technical Support—SNL 

SNL staff members served as chair of the Industry 

Forum for Article 690 of the National Electrical 

Code, and as a principal member of Code Making 

Panel for Article 690 and Article 705. Sandia staff 

also served on crucial committees associated with 

the Underwriters Laboratories Standards for 

inverters and controllers for PV and other 

distributed-generation applications. Sandia 

reviewed and provided language for changes in 

UL1741 for inverters and controllers and worked to 

verify and validate testing methodologies. Sandia 

also provided funding to and collaborated with 

BEW Engineering on international standards 

(specifically the International Electrotechnical 

Commission (IEC)) as the convener of Working 

Group 6 (PV Inverter and BOS standards) for 

Technical Committee 82 (TC82). The collaborative 

work with BEW also extended to further work in 

completing an economical testing protocol for 

certification of inverters. Much of this work was 

related to eliminating barriers to integrating PV 

systems into the utility grid. All work was focused 

on collaboration with Technology Pathway 

Partnership recipients and Market Transformation 

reduction in barriers. 

3.3. An Integrated Partnership to Create and Lead 

the Solar Codes and Standards Working Group— 

NMSU 

Work began in several areas. The Solar America 

Board for Codes and Standards (Solar ABCs) was 

organized, studies were begun, and PV stakeholder outreach was initiated. Specific accomplishments include: 

•	 Establishing Solar ABCs and adopting a 

charter describing its purpose. 

•	 Initiating studies on the following topics: 

o	 Solar system issues, including arc fault 

interrupter and external disconnect switch 

requirements and the effects of high 

winds; 

o	 Identifying causes and severity of PV 

module failures resulting from polymer 

property failure issues; 

o	 Standardizing PV cell performance; 

o	 Evaluating concentrating PV safety; 

o	 Approaches to speed system permitting; 

o	 Solar access and solar rights; 

o	 Advanced metering infrastructure; and 

o	 Rating and comparing the various system 

interconnection models. 

•	 Developing Solar ABCs Web site (http:// 

www.solarabcs.org) to disseminate information on Solar ABCs programs (09/07). 

•	 Organizing PV Stakeholders Workshop 

attended by approximately 250 people at Solar 

Power 2007 conference in Long Beach, 

California (09/07). 

3.4. Utility Solar Generation Valuation—Tucson 

Electric Power 

Electric utilities must have sufficient generating 

capacity available at all times to meet the load 

demands of customers. Many studies have 

evaluated the capacity credit of solar generation to 

utilities. Utilities, however, need tools to use highresolution (short time-scale) solar generation data 

to produce results accounting for regional effects 

on specific systems. TEP began work this year to 

develop a new and appropriate method for 

evaluating the capacity credit of solar generation. 

This work included: 

•	 Identifying the need for short time interval 

(10 second to 5 minute) analysis of power 

availability because of local effects on a solar 

system, including cloud cover (09/07). 

•	 Developing draft Demand Time Interval 

Method (DTIM), and presenting it at the Solar 

Power 2007 PV Stakeholder Workshop 

(09/07). 

3.5. A Standard Definition of PV Capacity Credit— 

SUNY–Albany 

As part of the SAI, SUNY began evaluating the 

variety of photovoltaic capacity valuation methods. 

It also began to bring the solar industry, electric 

utility, and research communities together with the 

goal of consensus on the most appropriate PV 

generation-capacity valuation methodology. 

Reaching consensus on methodology is an 

important step in removing barriers on dispersed 

PV generation—barriers which are the result of an 

incomplete and often contentious understanding of 

PV generation benefits. SUNY also completed and 

presented a draft of, “Moving Toward Consensus 

on a Photovoltaic Generation Capacity Valuation 

Methodology” for the PV Stakeholder Workshop, 

Solar Power 2007 Conference, Long Beach, 

California (09/2007). 

4. Planned FY 2008 Activities 

•	 NREL staff will provide leadership for and 

coordinate existing and new codes, standards, 

and entities that have jurisdiction in these 

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140
areas and over standards and codes 

requirements, such as state public utility 

commissions. 

•	 Sandia continues to chair the Industry Forum 

(now 150 members strong) and to provide 

leadership for Article 690 and Article 705 for 

the National Electrical Code (NEC). Major 

changes will begin to be implemented in the 

2011 edition of NEC with a increased effort to 

include all interconnect requirements in Article 

705 while maintaining the unique and PVspecific requirements in Article 690—Solar 

Photovoltaic Systems. Sandia staff will 

continue as a principal part of the codemaking-panel for PV- and distributed generation–related code requirements. 

•	 Sandia continues to work closely with NMSU 

and the SAI Solar ABCs groups to provide 

needed verification for new requirements 

before they are published. 

•	 Sandia will organize and lead the new 

“Inverter/controller/BOS/energy management 

Advisory Group” to prioritize activities for the 

Solar Energy Grid Integration Systems program and the Renewable System Interconnection initiative for advanced hardware for 

connection to the utility grid. This includes 

recommending updates and revisions for 

codes, standards, and certifications. 

•	 Sandia is leading the U.S. DOE Solar Energy 

Grid Integration Systems (SEGIS) program, 

which focuses on developing advanced 

inverters, controllers, and balance of system 

and energy-management hardware that likely 

will need new codes and standards 

requirements. 

•	 NMSU throughout the year will facilitate stakeholder involvement and communication on 

codes and standards issues, including holding 

stakeholder meetings and distributing 

electronic newsletters. 

•	 NMSU will complete studies on standards and 

code topics listed in section 3 above (07/08). 

•	 NMSU will provide recommended amendments to the National Electrical Code for solar 

systems (09/08). 

•	 NMSU will conduct a formal Gap Analysis and 

work with PV stakeholders to analyze the 

current state of major codes and standards for 

solar, and produce a prioritized list of codes 

and standards most urgently needed to 

remove barriers and promote the deployment 

of solar technologies (06/08). 

•	 TEP will discuss comparative results with 

several other electric utilities, and will publicize 

results at a national meeting (06/08). 

•	 SUNY–Albany will recommend two to three 

capacity credit metric methodologies (06/08). 

•	 SUNY-Albany will conduct “webinars” to 

disseminate findings and will write one to three 

technical articles to publicize recommended 

methodologies (06/08). 

5. Major FY 2007 Publications 

T. Hansen, “Utility Solar Generation Valuation 

Methods”, Solar Power 2007, PV Capacity Value 

Workshop, Long Beach, California, September 

2007. 

J. Wiles, W. Bower, “Changes In the 2008 

National Electrical Code®

 For PV Installations” 

Proceedings of the ASES Solar 2007, Cleveland, 

Ohio, June 2007. 

6. Partnerships 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/E-mail Description/Title of 

Research Activity 

FY 2007 

($K) 

Cost Share 

($K) 

NREL 

Thomas Basso 

Golden, CO 

Thomas_basso@ 

nrel.gov 

Provide leadership, participation in, and coordination with 

existing and new codes, 

standards, and authorities 

having jurisdiction, such as 

utility commissions. 

350 0 

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Organization/ 

Principal Investigator Location/E-mail Description/Title of 

Research Activity 

FY 2007 

($K) 

Cost Share 

($K) 

Sandia 

Ward Bower 

BEW Engineering 

Albuquerque, NM 

wib@sandia.gov 

San Ramon, CA 

Reducing and eliminating 

barriers to the deployment of 

PV and other distributed 

systems. 

250 0 

New Mexico State University 

Andrew Rosenthal 

Florida Solar Energy Center 

(University of Central Florida) 

Interstate Renewable Energy 

Council 

Sherwood Associates 

PowerMark Corporation 

Underwriters Laboratories 

Arizona St University 

Photovoltaic Testing Lab 

BEW Engineering 

Las Cruces, NM 

arosenth@nmsu.edu 

Cocoa, FL 

Latham, NY 

Boulder, CO 

San Ramon, CA 

Northbrook, IL 

Mesa, AZ 

San Ramon, CA 

Conduct work in a wide range 

of codes and standards issues 

for PV systems, including 

Building Electrical Codes, 

study of local codes, system 

interconnection, and product 

safety. 

1,200 0 

Tucson Electric Power 

Thomas N. Hansen 

Tucson, AZ 

thansen@tep.com 

Develop appropriate 

evaluation models of solar 

generation capacity valuation 

methods verified with actual 

utility data for use by utilities. 

100 100 

Research Foundation of the 

State University of New York 

Richard Perez 

Albany, NY 

perez@ 

asrc.cestm.albany.edu 

Achieve consensus on the 

methodology and metric to 

quantify the capacity credit of 

photovoltaic power generation 

that is acceptable to utilities 

and to the solar industry. 

98.6 25 

Photovoltaic R&D

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142
 

 

 

 

____________________________________________________________________________________ 

 

 

Training and Certification 

Performing Organizations: Interstate Renewable Energy Council (IREC) 

 New Mexico State University (NMSU) 

Key Technical Contacts:	 Margie Bates, (DOE Golden Field Office, Primary Contact), 

303-275-4845, Margie.bates@go.doe.gov 

Kevin Lynn (Florida Solar Energy Center), 202-586-1044, 

Kevin.lynn@hq.doe.gov 

Ward Bower (Sandia National Laboratories), 505-844-5206, 

wibower@sandia.gov 

John Wiles (Southwest Technology Development Institute), 

505-646-6105, jwiles@nmsu.edu 

DOE HQ Technology Manager:	 Charlie Hemmeline, 202-586-6646, charlie.hemmeline@hq.doe.gov 

FY 2007 Budget:	 $600,000 (DOE/GO) 

Objectives 

Interstate Renewable Energy Council 

•	 Promote better communications among stakeholders under the Solar America Initiative (SAI), to 

address infrastructure barriers to solar energy in coordination with industry, the U.S. Department 

of Energy (DOE), national laboratories, states, cities, and counties. 

•	 Create a five-year plan based on getting the right information to the right people; working on and 

implementing sustainable solutions to institutional and market barriers to solar energy; and 

offering easy and accessible communication channels for sharing information. IREC’s five-year 

plan encompasses the following: 

o	 Web Site and Newsletter. Manage and maintain the Interstate Renewable Energy Council 

Web site, which is the principal source of information for and about SAI Market 

Transformation (MT) partnerships and stakeholders, offering easily accessible news, 

information, tools, and materials. 

o	 Bi-weekly SAI-Market Transformation E-Newsletter. Bring up-to-date news and events to 

partnerships, state stakeholders, and federal agencies via e-mail. 

o	 SAI-Market Transformation Telephone Seminars. Connect experts with SAI-MT stakeholders 

on key issues in a cost-effective, convenient format. Post summary and highlights of seminar 

on the SAI Web site. 

o	 Connecting to the Grid Project. Provide models and assistance on net metering and 

interconnection to lower both barriers and cost for solar electricity installations. IREC 

continually updates model rules and the Connecting to the Grid guidebook, and provides 

technical assistance to solar stakeholders, including states, utilities, and other stakeholders. 

o	 Workforce Training and Quality Assessment Project. Encourage quality and accessible 

learning opportunities, lower installation and repair costs, and enhance consumer confidence. 

IREC coordinates and works with the North American Board of Certified Energy Practitioners 

and the Institute for Sustainable Power to maintain and expand the online course catalog, 

provides assistance to educational providers, maintains and updates training and certification 

Web pages, and updates Labor Forecast and Job Trends and Occupational Profiles reports. 

o	 Solar Codes and Standards Public Hearings. Monitor and participate, as appropriate, in 

public hearings and meetings and provide input using best practices that could impact solar 

barriers and/or commercialization (e.g., interconnection and net metering) in the wake of 

Energy Policy Act (EPAct) requirements for state consideration. IREC prepares and posts on 

the IREC Web site a report on the outcome of the public hearings. 

o	 Annual Publication. Prepare and submit an annual report documenting trends and impacts 

regarding interconnection and net metering, training and certification programs, state 

incentives, and other relevant newsworthy issues. 

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New Mexico State University 

•	 Establish a Solar Codes and Standards Working Group (SCSWG) that is engaged in identifying 

current issues, establishing a dialogue among key stakeholders, and catalyzing appropriate 

activities to support the development of codes and standards that facilitate the installation of highquality, safe photovoltaic (PV) systems, as well as education and training in the codes and 

standards. This sustained effort supports the timely introduction of new technologies as they 

occur and the overall growth of PV deployment to new sectors of the energy market. 

•	 Establish SCSWG activities within three major descriptive categories: study areas, coordination 

activities, and implementation activities. Coordination activities will be conducted by working 

panels designed to enable communication and planning across different codes and standardssetting processes in these five areas: building electrical codes, product safety codes, national 

standards, interconnection and net metering, and international standards. The working panels will 

provide implementation activities in support of these key stakeholder groups: code officials, state 

energy offices, and regulators. 

•	 Establish an Interconnection/Net Metering Working Panel whose objectives are to focus on 

providing needed support to U.S. PV stakeholders in this important and often diverse context. 

Tasks for this working panel consist of Web-based activities, coordination activities, and training 

and outreach activities. The panel is coordinating with ongoing IREC activities in this area to 

minimize duplication of effort and maximize leveraging opportunities. 

•	 Through the Interconnection/Net Metering Working Panel, obtain access to discussions and 

solutions of interconnection and net metering challenges, including facilitating communications 

between jurisdictions facing such challenges and those who have successfully met them. All 

activities and tasks are designed particularly for outreach, training, and interaction with SCSWG 

members and PV stakeholders, and they are critical to supporting growth in U.S. PV deployment 

over the next several years. 

Accomplishments 

Interstate Renewable Energy Council
 

IREC has accomplished the following to meet the objective to remove institutional and market barriers:
 

•	 Published 52 issues of the IREC/SAI e-newsletter for 1,700 subscribers and posted issues on the 

IREC Web site. 

•	 Regularly updated the State-by-State Interconnection and Net Metering Tables on the Web. 

•	 Promoted IREC’s Model Rules on Interconnection and Net Metering. 

• Produced Web-based, monthly updates of the EPAct tracking database of interconnection and 

net metering state activities. 

•	 Published 24 issues of the Interconnection/Net Metering e-newsletter for 2,300 subscribers and 

posted on the IREC Web site. 

•	 Regularly updated the State-by-State Interconnection and Net Metering Tables. 

•	 Promoted IREC’s Model Rules on Interconnection and Net Metering. 

•	 Produced monthly updates on the EPAct tracking database of interconnection and net metering 

state activities. 

•	 Published the 5th edition of the Connecting to the Grid Guide. 

•	 Updated Job Trends and Occupational Profile Reports. 

Future Directions 

Interstate Renewable Energy Council 

• In the Connecting to the Grid Project, provide models and assistance on net metering and 

interconnection to lower both the barriers to and the cost of installations of solar electricity. 

•	 Conduct workforce training activities to implement a sustainable solution to the market barrier of 

having too few trained solar professionals to meet market demand. 

• Through the Workforce Training and Quality Assessment Project, provide assistance to 

educational providers and coordinate the project with assistance from the North American Board 

of Certified Energy Practitioners (NABCEP) and the Institute for Sustainable Power; coordinate 

training workshops with states, cities, and other SAI-MT stakeholders to facilitate training 

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____________________________________________________________________________________ 

 

 

workshops for code officials to help them recognize codes and standards applicable to PV 

installations and understand important PV electrical installation issues. 

• Through the Solar Codes and Standards Hearing Project, address infrastructure barriers with the 

states. IREC has coordinated a team of individuals (e.g., engineers, lawyers) who can provide 

technical information to state policymakers and other stakeholders on solar codes and standards. 

Additional information will be provided to policymakers and other SAI-MT stakeholders before, 

during, or after the hearings. 

• Through the SAI-Market Transformation Recipient E-Newsletter and frequent telephone 

seminars, address infrastructure barriers by “getting the right information to the right people”; 26 

issues of the SAI-MT E-Newsletter will be disseminated per year, and six SAI Telephone 

Seminars, with a final report after each one are planned. 

•	 Continually maintain the IREC Web site, which enables focused stakeholder coordination and 

addresses key barriers with all stakeholders, including industry, DOE, national laboratories, and 

the states. 

New Mexico State University 

•	 Web-based Activities: Develop Web-based activities as an important element identified by the 

Interconnection/Net Metering Working Panel that will include developing and operating a listserve forum to facilitate discussions of interconnection and net metering issues identified by 

SCSWG members and the public. 

•	 Coordination Activities: Through the Interconnection Standards Study Panel, perform a one-year 

examination of critical interconnection issues that will analyze existing utility interconnection 

screens (institutional forms and processes that allow approval of interconnect requests) adopted 

by local jurisdictions and the perceived roles of these screens in facilitating PV deployments. This 

panel will also determine the usefulness of the external utility disconnect switch that local 

jurisdictions often require but is also often described as superfluous and unneeded. The panel will 

prepare a final report to identify resolutions of contentious issues governing the interconnection 

process from both institutional and hardware perspectives. 

1. Introduction 

The Interstate Renewable Energy Council seeks 

to promote better communications among 

stakeholders under the Solar America 

Initiative/Market Transformation (SAI-MT) 

project to address infrastructure barriers to solar 

energy and to coordinate with industry, DOE, 

national laboratories, states, cities and counties. 

This five-year plan is based on getting the right 

information to the right people; working on and 

implementing sustainable solutions to 

institutional and market barriers to solar energy; 

and offering easy and accessible communication 

channels for sharing information. 

2. Technical Approach 

In 2007, IREC continued to promote better 

communications among stakeholders, 

addressed infrastructure barriers by promoting 

easy and fair hook-up rules to the utility grid, 

promoted quality training based on industry 

competency standards, and coordinated closely 

with multiple federal, state and local 

stakeholders. 

2.1 Net Metering and Interconnection 

The August 2005 enactment of the federal 

Energy Policy Act (EPAct) of 2005 and the May 

2005 adoption of Federal Energy Regulatory 

Commission (FERC) Order 2006 have inspired 

several states to examine or reexamine 

interconnection standards and/or net-metering 

rules. EPAct created another reason for states 

to consider net metering and interconnection. 

Under Sections 1251 and 1254, every utility 

must offer interconnection—based on Institute of 

Electrical and Electronics Engineers (IEEE) 

1547 rules—and net metering to all of their 

customers. 

Along with this increased activity, IREC has 

been participating in state working groups 

providing legal and technical expertise. In 2007, 

seven states were on the priority list: Arizona, 

Florida, Illinois, Maryland, New Mexico, North 

Carolina and Texas. 

IREC’s approach on Interconnection Rules 

includes the following: 

•	 Rules should be designed to eliminate as 

many barriers as possible to result in easy 

but safe interconnection. 

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•	 Rules are the collection of best practices 

from federal and state actions, e.g., those of 

FERC Order 2006, National Association of 

Regulatory Commissions (NARUC) New 

Jersey, Massachusetts, Colorado, and 

Texas. 

•	 The IREC model uses as its core the recent 

IEEE 1547 standard and the associated 

Underwriters Laboratories 1741 testing 

standard. 

•	 The interconnection procedures are divided 

into four areas to categorize 

interconnections from the least to the most 

complex: 

o	 Level 1 – 10 kW and smaller for certified 

inverters (residential-sized systems) 

o	 Level 2 – 2 MW and smaller, certified 

(commercial net metering and other 

systems) 

o	 Level 3 – 10 MW certified generators, 

nonexporting (designed for combined 

heat and power, or CHP, facilities) 

o	 Level 4 – All others up to 10 MW, 

including generators that attempt to 

meet but do not qualify for other, more 

expedited standards. 

2.2 New Mexico State University 

NMSU has developed an Interconnection/Net 

Metering Working Panel under its Solar Codes 

and Standards Working Group that will focus on 

providing necessary support to U.S. PV 

stakeholders in this important and often diverse 

context. The working panel coordinates with 

ongoing IREC activities in this area to minimize 

the duplication of effort and maximize leveraging 

opportunities. Examples include these: 

•	 Web-Based Activities. NMSU Web-based 

activities include developing and operating a 

list-serve forum to facilitate discussions of 

interconnection and net metering issues 

identified by SCSWG members and the 

public. 

•	 Coordination Activities. The NMSU’s 

Interconnection/Net Metering Working Panel 

holds regular, open meetings for SCSWG to 

establish priorities and action plans for 

addressing the most pressing problems 

facing SCSWG members. Panel members 

participate in public forums to gain greater 

access to discussions and solutions of 

interconnection and net metering 

challenges, including facilitating 

communications between jurisdictions facing 

such challenges and those who have 

successfully met them. 

2.3 IREC’s Workforce Development 

Because of the growth in the solar market over 

the past few years and renewed attention to 

solar energy solutions, workforce development 

and quality training have become a critical 

component for this sector. If the goals of the 

Photovoltaic Industry Road Map are met, direct 

employment would increase from 20,000 now to 

62,000 by 2015. DOE estimates that as many as 

5,000 trained installers could be needed by 2015 

to accomplish the new Solar America Initiative. 

IREC continues its work with Community 

Colleges and with the North American Board of 

Certified Energy Practitioners (NABCEP). IREC 

focuses its work on quality training and verifies 

the legitimacy of the training content and 

trainers. In consultation with subject matter 

experts and educational providers, IREC’s 

training approach is based on these 

recommendations: 

•	 Design training to provide educational and 

skill-development experiences that lead to 

defined workplace knowledge, skills, and 

abilities. 

•	 Address issues of safety, codes, and core 

competencies of an industry-approved task 

or job analysis. 

•	 Conduct training in appropriate facilities with 

proper tools, safe practices, and in an 

atmosphere of administrative and 

managerial quality. 

•	 Offer a formal, planned learning structure in 

which the learner receives feedback and the 

learner’s progress is monitored. 

•	 Conduct training under the administration of 

a legally registered entity. 

•	 Ensure that training is offered by any 

accredited university, college, community 

college, or vocational-technical institute; or 

by any Joint Apprenticeship and Training 

Committee or U.S. Department of Laborapproved apprenticeship program; or by a 

training program accredited by IREC to 

Institute for Sustainable Power quality 

(ISPQ) standards or those of a similar 

accrediting body; or is approved by the State 

Contractor Licensing Boards; or is offered or 

taught by a certified installer with 

instructional experience. 

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3. Results and Accomplishments 

•	 Published 26 issues of the IREC/SAI enewsletter 

•	 Published 12 issues of the Interconnection/ 

Net Metering e-newsletter 

•	 Added 5,000 subscribers to the two 

newsletters 

•	 Regularly updated the State-by-State 

Interconnection and Net Metering Tables on 

the Web 

•	 Promoted IREC’s Model Rules on 

Interconnection and Net Metering 

•	 Produced Web-based, monthly updates of 

the EPAct tracking database of 

interconnection and net metering state 

activities 

•	 Organized six phone seminars; topics 

included solar renewable energy credits, 

interconnection and net metering, feed-in 

tariffs, federal solar tax incentives, 

photovoltaic market trends, and solar access 

laws 

•	 Convened six workshops for code officials 

•	 Participated in and filed comments and reply 

comments at interconnection/net metering 

hearings and meetings in targeted states 

•	 Updated Job Trends and Occupational 

Profile Reports. 

4. Planned FY 2008 Activities 

To meet the SAI objectives for Solar Outreach 

and Communications proposed for FY 2008, 

IREC will use an integrated approach that 

combines Web-based resources, on-site and 

electronic forums, print material and technical 

assistance by utilizing and enhancing the 

resources described in the following paragraphs. 

The IREC Web site (www.irecusa.org) will 

feature news, articles, and events covering 

areas such as solar schools, interconnection to 

the grid and net metering, community and 

national outreach, workforce development 

(training and certification), and other stakeholder 

information. 

IREC continues to coordinate and participate in 

stakeholder coordination activities with DOE, 

industry, states, and all stakeholders, and 

actively participates in the annual American 

Solar Energy Society (ASES), Solar Energy 

Industries Association (SEIA), and Solar Electric 

Power Association (SEPA) conferences. 

IREC will publish the Connecting to the Grid 

newsletter. Issues include state, national, 

international, industry news, publications and 

events. Three important trends have been 

reported: first, how the North American Electric 

Reliability Corporation is beginning to 

accommodate renewables at the grid level; 

second, how many utilities are planning to make 

significant investments in utility-scale 

renewables; and, third, how time-of-use pricing, 

as facilitated by automated metering 

infrastructure, has the potential to make retail 

rates correspond realistically to wholesale 

rates—a shift that changes everything. 

Regarding workforce development, IREC will 

continue working on implementing quality 

assessment of training programs and 

instructors, a critical component. IREC is using 

the ISP international framework of metrics and 

standards to measure the quality and 

consistency of training programs and trainers. 

IREC works with educational providers such as 

Lane Community College, Hudson Valley 

Community College, Solar Energy International, 

the North Carolina Solar Energy Center, Florida 

Solar Energy Center, and other training 

resources. In addition, IREC will continue 

working closely with NABCEP and the ISP to 

ensure quality assessment of practitioners and 

training programs. IREC’s proposals for two 

forums at the ASES 2008 May conference were 

accepted: one on workforce development and 

the other on certification. 

In addition, IREC is writing an article for the 

Northeast Sun magazine on workforce 

development. And IREC is working with New 

York State in planning the second Workforce 

Education Conference, which will take place the 

week of March 17, 2008, at Hudson Valley 

Community College outside of Albany, NY. Also, 

during the last quarter of 2007, IREC’s Annual 

Report on updates and trends was released. 

The Annual Metrics Report will be prepared in 

March 2008. 

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At solar codes and standards public hearings, 

IREC and its team of experts provide legal and 

regulatory expertise and are currently monitoring 

and participating in state and public hearings 

that could impact interconnection standards and 

net metering, especially in regard to EPAct 

requirements. In consultation with industry and 

DOE, IREC has targeted seven states for 

interconnection and net metering rule-making 

activities: Arizona, Florida, Illinois, Maryland, 

North Carolina, New Mexico, and Texas. 

The semi-monthly SAI/IREC State E-Newsletter 

will continue to report on DOE, state, 

stakeholder, and former Million Solar Roofs 

Initiative partner activities. More than 2,000 

people receive the newsletter. Plans are 

underway with DOE SAI-MT staff to focus on 

news and interviews with Solar America cities. 

IREC will also plants to continue to host SAI 

Telephone Seminars featuring select topics and 

expert speakers based on stakeholder input. 

The seminars, which have been widely 

attended, are interactive, allowing each 

participant to view presentations and ask 

questions. Seminar highlights and presentations 

are available on the IREC Web site. 

5. Major FY 2007 Publications 

In addition to numerous presentations at 

conferences and meetings, project members 

published the following: 

Connecting to the Grid Guidebook, 5th Edition 

(2007). 

J. Weissman, “Workforce Education for 

Renewable Energy: Lessons Learned from a 

National Gathering of Educators,” Proceedings 

of the ASES Annual Conference, July (2007). 

L. Sherwood, “U.S. Solar Market Trends,” 

Proceedings of the ASES Annual Conference, 

July (2007). 

Annual Metrics Reports on Solar Installations 

(2007). 

Annual Trends & Update Report, September 

(2007). 

6. University and Industry Partners 

IREC works closely with many groups, industry, and community colleges, which include the following: 

• North Carolina Solar Center at North Carolina State University 

• The Southwest Technology Development Institute at New Mexico State University 

• New York State Energy Research and Development Authority 

• North American Board of Certified Energy Practitioners 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

Technology Acceptance 

Performing Organizations: DOE Golden Field Office (DOE/GO) 

North American Board of Certified Energy Practitioners (NABCEP) 

Key Technical Contact: Steve Palmeri (DOE/GO) 303-275-4832, steve.palmeri@go.doe.gov 

DOE HQ Technology Manager: Thomas Kimbis, 202-586-7055, tom.kimbis@ee.doe.gov 

FY 2007 Budgets: $325K (DOE/GO) 

Objectives 

•	 Since 2003, the North American Board of Certified Energy Practitioners (NABCEP) has been 

awarding professional credentials to solar installers. NABCEP’s provides rigorous competency 

standards for certification to send a clear message to consumers, financers, and public officials 

that the Industry stresses high quality, safe and ethical business practice, and workmanship 

standards. 

Accomplishments 

•	 Administered the photovoltaic (PV) exam twice, in March and September. At the end of fiscal year 

(FY) 2007, 422 people were certified PV Installers. 

•	 Administered the solar thermal exam twice, in March and September. At the end of FY 2007, 

there were 56 Solar Thermal Certificants. 

Future Directions 

•	 NABCEP plans to continue offering PV and solar thermal exams, in March and September 2008. 

•	 Due to the popularity of the PV Entry Level Certificate of Knowledge, NABCEP plans to develop a 

sample exam, study guide, and/or a course outline for instructors. 

1. Introduction 

Since 2003, the North American Board of Certified 

Energy Practitioners (NABCEP) has been 

awarding professional credentials to solar 

installers. NABCEP’s rigorous competency 

standards for certification sends a clear message 

to consumers, financers, and public officials that 

the Industry stresses high quality, safe and ethical 

business practice, and workmanship standards. 

NABCEP has three certification programs: 

•	 Professional credential for Solar Electric (PV) 

Installers 

•	 Professional credential for Solar Thermal 

Installers 

•	 Entry level certificate of knowledge for PV 

2. Technical Approach 

NABCEP recognizes that professionals in the field 

of renewable energy technologies receive their 

training and work experiences in a variety of ways. 

Therefore, each requirement to qualify for the 

exam stipulates specific training and/or 

experience. 

Both the PV and solar thermal credentialing 

programs are based on strict, psychometric 

principles and credentialing guidelines. The 

program is rigorous, requiring documentation of 

experience and/or training and the passing a 4-

hour exam. 

NABCEP has developed two task analyses, one 

for the PV Installer and the other for the Solar 

Thermal Practitioners. The task analysis is a 

formal process for determining what people do, 

under what working conditions they do it, what 

they must know to do it, and the skills they must 

have to do it. A technical committee of subject 

matter experts develops the task analysis. 

The task analysis contributes to test validity by 

ensuring that the critical aspects of the job 

become the domain of content that the test 

measures. 

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The PV Installer Task Analysis includes 8 main 

tasks and 58 subtasks. The Solar Thermal Task 

Analysis includes 12 main tasks and 129 

subtasks. 

After the overall content of the test has been 

established through the task analysis, the next 

step in developing a test is to create the detailed 

test specifications. Test specifications include a 

test description component and a test blueprint 

component. The test description specifies aspects 

of the planned test such as the test purpose, the 

target examinee population, the overall test length, 

and more. The test blueprint provides a listing of 

the major content areas and cognitive levels 

intended to be included on each test form. 

Once the test specifications are complete, the item 

writing phase of the test development project 

begins. A panel of subject matter experts is 

assembled to write a set of test items (questions). 

NABCEP convenes both the PV Exam Committee 

and the Solar Thermal Exam Committee. The 

Committee is assigned to write items according to 

the content areas and cognitive levels specified in 

the test blueprint. Items are written for each of the 

item types identified in the test specifications. 

Both the PV and Solar Thermal exams are given 

twice a year. Each exam runs for a maximum of 4 

hours and includes 60 scenario-based multiplechoice questions. The exams are administered 

with strict security and monitored by both a proctor 

and administrator. 

NABCEP also offers an entry level Certificate of 

Knowledge aimed at students wanting to get into 

the solar photovoltaic field. After taking a course 

from an approved provider and passing a national 

exam, this Certificate shows that the recipient has 

achieved basic knowledge, comprehension and 

application of key terms and concepts of 

photovoltaic (solar electric) system operations. 

The Certificate by itself does not qualify an 

individual to install PV systems but it does prepare 

them for employment in the field. 

As the market grows for PV, the person holding 

this industry-sponsored Entry Level Certificate is 

likely to find that their employment opportunities 

enhanced by starting the job with an 

understanding of the basic terms and operational 

aspects of a PV system and that their NABCEP 

Entry Level Certificate is noticed by potential 

employers. 

3. Results and Accomplishments 

Exam Administration 

The PV and solar thermal exams are administered 

twice, in March and September. 

At the end of FY 2007, 422 people were certified 

PV Installers. The Solar Thermal Credential was 

started in 2006, and at the end of FY 2007, there 

were 56 Solar Thermal Certificants. These 

certificants represent 41 states, as well as 

Canada, Puerto Rico, and Honduras. 

By the end of the fiscal year, NABCEP had 26 

institutions offering the PV Entry Level Certificate 

of Knowledge course and exam, a 44% increase. 

These were top 10 states: 

State Number of PV & 

Solar Thermal 

Certificants 

Percent of Total 

California 145 33% 

Colorado 31 7% 

New York 29 7% 

Wisconsin 18 4% 

New Jersey 17 4% 

Vermont 17 4% 

New Mexico 13 3% 

Texas 13 3% 

Arizona 11 2.5% 

Ohio 11 2.5% 

PV and Solar Thermal Exam Committee Meetings 

The Solar Thermal Exam Committee met in 

Chicago on June 4-6, 2007, and the PV Exam 

Committee met in Albuquerque on June 26-28, 

2007. The main purpose was to add new 

questions to the item bank for the upcoming 

exams, test assembly, pool review, and standard 

setting exercise. 

Outreach to consumers and industry 

NABCEP exhibited at: 

•	 New York Solar Industries Exhibition in 

Albany, New York 

•	 Midwest Renewable Energy Fair in Custer, 

Wisconsin 

•	 ASES Solar Energy Conference in Cleveland, 

Ohio 

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150
•	 NJATC – National Training Institute (NTI) 

“Train the Trainer” Conference in Knoxville, 

Tennessee 

•	 Solar Power 2007 Conference in Long Beach, 

California 

•	 NECA 2007 Conference in San Francisco, 

California 

As part of our outreach strategy, a board member 

used SEPA’s conference registration listing for the 

Solar Power 2007 Conference to prepare an 

invitation list and agenda for a state lunch and 

presentation at the conference. 

PV Entry Level Certificate of Knowledge 

At the end of FY ‘07, NABCEP has 26 institutions 

offering the Entry Level course and exam, a 44% 

increase. Additionally, we have noticed a marked 

increase in inquiries from eligible institutions. To 

date, 662 students have taken the exam. 

ANSI Accreditation 

NABCEP has been going through the application 

and audit process for Accreditation to the ISO 

Standard 17024, Bodies that Certify People. On 

September 10, 2007, we learned that we had 

earned the prestigious ANSI/ISO/IEC 17024 

Accreditation. This award validates NABCEP’s 

Solar PV Installer Certification Program by an 

independent, unbiased accreditation body. 

ANSI/ISO/IEC 17024 specifies requirements which 

ensure that organizations operating certification 

systems for persons operate in a consistent, 

comparable, and reliable manner. This 

accreditation includes rigorous requirements for 

examination development and maintenance and 

for quality management systems. ANSI/ISO/IEC 

17024 has been approved by 85 countries. 

4. Planned FY 2008 Activities 

PV and Solar Thermal Exams 

NABCEP will be offering the PV and Solar 

Thermal exams for experienced installers on 

March 15 and September 13, 2008, at various 

locations across the United States. 

PV Entry Level Certificate of Knowledge 

This certificate has become very popular among 

Community Colleges and offers students a career 

ladder into the solar energy field. We have 

received numerous requests from students and 

instructors for a sample exam, study guide, and/or 

a course outline for instructors, and have plans to
 

develop one or more of these tools in the 

upcoming fiscal year. 

Outreach to Consumers and Industry 

NABCEP plans to exhibit at the following events: 

•	 NESEA Conference, Boston, MA (March 11-

13) 

•	 Workforce Education Conference, Troy, NY 

(March 18-20) 

•	 SEI/ COSEIA Conference, Fort Collins, CO 

(March 25-29) 

•	 Solar NY/NYSEA Albany, NY (April 15) 

•	 ASES, San Diego, CA (May 3-8) 

•	 MREA, Custer, WI (June 20-22) 

•	 NECA, Chicago, IL (October 4-7) 

•	 Solar Power 2008, San Diego, CA (October 

13-17) 

ANSI 

Quarterly meetings will be held with a 

subcommittee to review updates and changes to 

documents and procedures affected by 

organizational changes. We also prepare for our 

yearly on-site process audit. 

5. University and Industry Partners 

NABCEP works closely with representatives from 

the following companies and organizations: 

•	 American Wind Energy Association 

•	 Alternative Energy Institute 

•	 Appalachian State University 

•	 BP Solar 

•	 Home Power Magazine 

•	 IBEW 

•	 Interstate Renewable Energy Council 

•	 Malaspina College 

•	 Midwest Renewable Energy Association 

•	 National Electrical Contractors Association 

•	 National Joint Apprenticeship & Training 

Committee 

•	 National Renewable Energy Laboratory 

•	 North Carolina Solar Center 

•	 NYSERDA 

•	 Powerlight Corporation 

•	 Sandia National Laboratories 

•	 Sharp Solar 

•	 Solar Energy International 

•	 Solar Rating Certification Corporation 

•	 Southwest Technology Development Institute 

•	 SunEdison Corporation 

•	 SunPower Corporation. 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Building Integration 

Solar Decathlon 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 DOE Golden Field Office (DOE/GO) 

Key Technical Contacts:	 Cécile Warner (NREL, Primary Contact), 303-384-6516, 

cecile_warner@nrel.gov 

Glenn Doyle (DOE/GO), 303-275-4706, glenn.doyle@go.doe.gov 

DOE HQ Technology Manager:	 Richard King, 202-586-1693, richard.king@ee.doe.gov 

FY 2007 Budgets:	 $3,700K (NREL) 

Objectives 

•	 Lead and conduct the Solar Decathlon university competition of 100% solar-powered houses, 

which demonstrate solar technologies in marketable residential applications. 

•	 Accelerate adoption of Building-Integrated Photovoltaics (BIPV) in new residential and 

commercial construction through technical outreach via the event and through successful 

collaborative partnerships.
 

Accomplishments 

•	 Prepared for, conducted, and concluded the safe and successful implementation of the 2007 

Solar Decathlon university competition on the National Mall in Washington, DC, including 

releasing the final regulations; solidifying sponsors; supporting teams; and scoring, monitoring, 

and implementing all aspects of the event (October 2007). 

•	 Developed and released a solicitation for the 2009 Solar Decathlon event (October 2007). 

Future Directions 

•	 Conduct the 2009 Solar Decathlon in the fourth quarter, fiscal year 2009, and release a 

solicitation for the 2011 event. 

•	 Monitor and guide the development of solar energy systems through the subcontracted university 

programs. 

•	 Continue and expand productive interactions with the building industry. 

1. Introduction 

The Building-Integrated Photovoltaics (BIPV) 

Project fosters the widespread acceptance of 

photovoltaic-integrated buildings by overcoming 

technical and commercial barriers, and by 

facilitating the integration of photovoltaics (PV) into 

the built environment through technology development, applications, and key partnerships. Through 

this project, PV will become a routinely accepted 

building technology in the twenty-first century. 

2. Technical Approach 

The project’s goal is to develop and facilitate 

widespread adoption of PV in the built environment, resulting in solar-powered houses and 

businesses that demonstrate BIPV and solar 

technologies in marketable applications and 

partnerships that build on successes. There are 

two interrelated activities within this overall effort, 

including the Solar Decathlon and research and 

development (R&D) on PV in buildings. 

2.1. Conduct the 2007 Solar Decathlon 

The Solar Decathlon is an intercollegiate competition to design, build, and operate the most attractive and energy-efficient solar-powered house. 

Twenty teams of students from the United States, 

Canada, and Spain competed in the 2007 event. 

Teams were selected through a competitive 

procurement conducted in 2005, and they worked 

on their projects over the intervening 2 years, 

under our supervision and guidance. They 

transported their houses to the National Mall in 

Washington, DC, where they built a “solar village.” 

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The houses were open to the public from October 

12 to October 20, 2007. The teams competed 

against each other in ten contests that tested their 

abilities to produce electricity and hot water from 

solar panels to perform all the functions of the 

house—from turning on the lights to cooking, 

washing clothes and dishes, powering home 

electronics, and maintaining a comfortable temperature. These houses also were required to 

provide the power for an electric car. In addition to 

the energy-related contests, each team was 

judged on its house’s architecture and livability. 

Expert homebuilders evaluated each house’s 

“build-ability” (ease of construction and replication 

of design). Each team provided documentation 

about its house’s design and communicated 

information about the house to the public. We 

hosted a Web site that informed visitors about the 

competition and scoring. 

Production of the event, including scoring; selection of judges; review of designs; instrumentation; 

development of communications materials and 

review of exhibit designs; coordination of teams, 

sponsors, and volunteers; procurement of stagecraft and assembly of the village; and safe conduct 

of the entire event comprised the activities of this 

project for the NREL organizers and subcontractors. Some contests were scored by 

measuring performance, and others were scored 

by judges having expertise in appropriate fields. 

For more information, visit the Solar Decathlon 

Web site (www.solardecathlon.org). The primary 

sponsors of the 2007 Solar Decathlon are the U.S. 

Department of Energy’s Office of Energy 

Efficiency and Renewable Energy, with its 

National Renewable Energy Laboratory, the 

American Institute of Architects, the National 

Association of Home Builders (NAHB), the U.S. 

Green Building Council (USGBC) and privatesector sponsors BP, Honeywell, and Sprint-Nextel. 

2.2. Develop and Release Solicitation for 2009 

Solar Decathlon Event 

While also preparing for the 2007 event, the 

concept for a new round of R&D at the universities 

participating in the 2009 event evolved, culminating in the development of a solicitation for the 

2009 event (prepared by NREL) to be announced 

by the Secretary of Energy in early October at the 

start of the 2007 event. With this solicitation, and 

as done in 2005, each winning university proposal 

was set to receive $100K in research funding 

(over 2 years) to support the innovative development of its entry. 

Task Title FY 2007 

Budget ($K) 

Solar Decathlon (NREL) 3,700K 

3. Results and Accomplishments 

3.1. Major Accomplishment: Solar Decathlon 2007 

During FY 2007, we successfully prepared for 

carrying out the 2007 Solar Decathlon, held from 

October 1 to October 24, 2007 on the National 

Mall in Washington, DC. Activities included scoring 

for the 10 contests; expert judging for the contest 

on aspects such as market appeal, architecture, 

engineering, Web sites, and house tours; a review 

of team designs for code and regulation compliance; instrumentation system development, acquisition, and shakedown, as well as installations of 

equipment; distribution of communications materials (brochures, media kits, official program, Web 

site materials, and graphics); coordination of 

teams; coordination of sponsors; coordination of 

volunteers (including a procurement for management of volunteers); procurement of stagecraft and 

assembly of the solar village; and execution of 

procedures for safely conducting the entire event. 

We managed crowds of more than 120,000 

visitors to the Solar Decathlon and the massive 

media interest to view the future of solar energy 

and the next generation of solar practitioners and 

solar houses. 

3.2. Major Accomplishment: Prepare for solicitation and selection of teams for the 2009 Solar 

Decathlon and launch the activities leading toward 

execution of the 2009 event. We developed a 

process for the selection of 20 teams (from proposal responses to a solicitation) to participate in 

the 2009 Solar Decathlon. 

Milestones Supported by DOE Funding 

Milestone or Deliverable Due Date Status 

Carry out Solar Decathlon 

2007 event in Washington, 

DC, on the National Mall, 

beginning October 2007. 

11/01/07 Complete 

Release solicitation for 

university participants for 

the 2009 event. 

10/12/07 Complete 

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4. Planned FY 2008 Activities university programs and through evaluation of 

•	 Announce the 2009 Solar Decathlon Teams in long-term performance of selected entries. 

the first quarter, FY 2009. 

•	 Continue the activities leading toward execu- 5. Major FY 2007 Publications 

tion of the 2009 Solar Decathlon event. 

•	 Monitor and guide the development of solar- U.S. Department of Energy, Solar Decathlon Web 

energy systems through the subcontracted Site, www.solardecathlon.org. 

6. University and Industry Partners 

The following organizations partnered in the project’s activities during FY 2007. 

Organization/ 

Principal Investigator Location/E-mail Description/Title of Research Activity FY 2007 ($K) 

Colorado Code 

Consulting, LLC 

Thomas Meyers 

Berthoud, CO 

codeconsultant@gmail.com 

Complete 3 plan reviews of 20 sets of 

drawings and specifications and perform 20 

on-site building inspections of the competition 

houses after installation on the National Mall in 

fall 2007 for the Solar Decathlon competition. 

70 

Carnegie Mellon 

University 

Stephen R. Lee 

Pittsburgh, PA 15213 

Phone: 412-268-3528 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. Those selected for the 

competition were awarded $100,000 over 2 

years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Cornell University 

Zellman Warhaft 

Ithaca, NY 14853 

Phone: 607-255-3898 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Georgia Institute of 

Technology 

Chris Jarrett 

Atlanta, GA 30332 

Phone: 404-894-4885 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Kansas State 

University 

R. Todd Gabbard 

Manhattan, KS 66506-2901 

Phone: 785-532-1129 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Organization/ 

Principal Investigator Location/E-mail Description/Title of Research Activity FY 2007 

($K) 

Massachusetts Institute 

of Technology 

Kurt Keville 

Cambridge, MA 

Phone: 617-324-6422 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

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New York Institute of 

Technology 

Thomas Rochon 

New York, NY 

Phone: 212-261-1629 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Pennsylvania State 

University 

David R. Riley 

University Park, PA 

Phone: 814-863-2079 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Santa Clara University 

Jorge E. Gonzalez 

Santa Clara, CA 

Phone: 408-554-4459 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Team Montréal Twenty teams were selected to compete in the 

(École de Technologie 2007 Solar Decathlon. The teams selected for 

Supérieure, Université 

de Montréal, McGill 

University) 

Montréal, Quebec, Canada 

Phone: 514-396-8667 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

50 

Hughes Rivard technology. 

Technische Universität 

Darmstadt 

Manfred Hegger 

D-64287 Darmstadt, 

Germany 

Phone: +49-6151-16-20-46 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Texas A&M University 

Pliny Fisk 

College Station, TX 

Phone: 979-458-4124 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50 

Organization/ 

Principal Investigator Location/E-mail Description/Title of Research Activity FY 2007 

($K) 

Universidad de Puerto 

Rico 

Rafael A. OlivenciaMartínez 

Mayagüez, Puerto Rico 

00681-9009 

Phone: 787-832-4040 

ext. 5361 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50K 

University of Colorado 

Michael Brandemuehl 

Boulder, CO 80309-0428 

Phone: 303-492-8594 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50K 

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University of Cincinnati 

Dale L. Murray 

Cincinnati, OH 45221-0016 

Phone: 513-556-1524 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50K 

University of Illinois 

Ty Newell 

Urbana, IL 61801 

Phone: 217-333-1655 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50K 

University of Maryland 

Amy Gardner 

College Park, MD 

20741-1411 

Phone: 301-405-6303 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years, to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50K 

University of Missouri– 

Rolla 

Stuart W. Baur 

Rolla, MO 65409 

Phone: 573-341-7236 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition will be awarded $100,000 over 

2 years to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50K 

University of Texas at 

Austin 

Samantha Randall 

Austin, TX 78712-1160 

Phone: 512-466-9298 

Twenty teams were selected to compete in the 

2007 Solar Decathlon. The teams selected for 

the competition were awarded $100,000 over 

2 years to support the Solar Decathlon’s 

research goal of reducing the cost of solarpowered houses and advancing solar 

technology. 

50K 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

Building Integration 

Building-Integrated Photovoltaics (Solar Building Benchmarking) 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 DOE Golden Field Office (DOE/GO) 

Key Technical Contacts:	 Michael Wassmer (NREL, Primary Contact), 303-384-6461, 

michael_wassmer@nrel.gov 

Glenn Doyle (DOE/GO), 303-275-4706, glenn.doyle@go.doe.gov 

DOE HQ Technology Manager:	 Richard King, 202-586-1693, richard.king@ee.doe.gov 

FY 2007 Budget:	 $250K (NREL) 

Objectives 

•	 Support the deployment of Building-Integrated Photovoltaics (BIPV) technologies by measuring 

their in situ performance in various locations throughout the country. 

•	 Provide participating university research groups with the technical knowledge they need to 

conduct their own experiments on various aspects of Solar Decathlon houses. 

Accomplishments 

•	 Conducted building energy monitoring and computer modeling research on past Solar Decathlon 

houses to (1) improve future Solar Decathlon contests, (2) quantify the annual performance of the 

houses, (3) identify areas of technical significance in the houses to focus future teams’ design 

efforts, and (4) extend the education and outreach component of the competition beyond the 10 

days on the National Mall. 

•	 Substantially completed the installation and commissioning of building energy monitoring systems 

in the 2005 Cornell and New York Institute of Technology (NYIT) houses (January 2007). 

•	 Completed the design and partially completed the installation of building energy monitoring 

systems in the 2007 Lawrence Technological University, University of Illinois, Carnegie Mellon, 

Penn State, and Santa Clara University houses (September 2007). 

•	 Completed the design of a Web-based “dashboard” display that illustrates the houses’ 

performance in real time (September 2007). 

Future Directions 

•	 Collect data from the 2005 Cornell and NYIT houses. 

•	 Complete the installation and commissioning of systems in five 2007 houses and begin to collect 

data. 

•	 Work with the NREL Web development team to publish the real-time dashboard display on the 

Solar Decathlon Web site. 

•	 Recruit participants in the project from among the 2009 Solar Decathlon teams and Solar 

America Cities. 

1. Introduction computer models that will be used to improve 

future competitions. 

The Solar Building Benchmarking activity within 

the BIPV Project extends the Solar Decathlon This monitoring also helps to guide future Solar 

project into a long-term research and outreach Decathlon teams’ efforts and quantify the 

opportunity. Detailed building energy monitoring performance of the houses in terms of their 

systems are installed in past Solar Decathlon intended occupancy patterns and the climates 

houses to continue to educate the public about for which they were designed. 

the houses after a particular competition has 

ended and to aid in the calibration of detailed 

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2. Technical Approach 

Many building energy research activities are 

conducted using computer models that are 

either poorly calibrated or not calibrated at all. 

The lack of model calibration casts doubt on the 

validity of the results, since certain important 

performance characteristics could be attributable 

to either the building itself or to imperfections 

within the model. This project seeks to 

substantially reduce the consequences of the 

latter shortcoming through detailed calibration of 

the computer models that are used to 

extrapolate the performance of the home 

beyond the climatic and occupancy patterns 

actually experienced. 

The calibrated computer models will be used to 

project the home’s performance in a range of 

hypothetical climates and occupancy behavior 

patterns. This will help both Solar Decathlon 

teams and organizers to identify the most and 

least effective system choices and design 

approaches in previous generations of Solar 

Decathlon competition houses. With this 

knowledge, the organizers will be able to design 

contests that challenge the universities to 

develop creative solutions in the areas of 

residential building design that are in the 

greatest need of improvement. 

In the past, the incredible opportunity afforded 

by the Solar Decathlon for education and 

outreach essentially ended when the houses left 

the competition site. By continuously monitoring 

and interpreting the real-time performance of the 

houses on their permanent sites, and by 

presenting this information on the Solar 

Decathlon Web site, the education and outreach 

potential of the competition in science class 

curricula improves exponentially. This visibility 

also improves community outreach opportunities 

for the universities and offers home builders 

insight into the performance of these ultra-highefficiency houses in the real world. These 

insights could be some of the deciding factors in 

motivating builders to implement some of the 

design features and system choices in their 

designs. 

3. Results and Accomplishments 

In January 2007, we substantially completed the 

installation of the monitoring systems in the 

2005 Cornell University and 2005 NYIT houses. 

These installations will be finalized and 

commissioned when the owners make some 

repairs and system adjustments that have been 

delayed since the houses were assembled on 

their final sites. Official data collection began in 

spring 2007, but it was suspended because 

some house performance problems remained as 

a result of incomplete repairs and adjustments. 

During the spring and summer of 2007, NREL 

personnel worked with five 2007 Solar 

Decathlon teams to complete the design of 

monitoring systems that were assembled and 

partially installed in their houses during the 

construction stages on campus. Several of the 

teams used the partially installed systems to aid 

in house operation and outreach activities during 

the competition in October 2007. 

The project was improved in 2007 in two 

significant ways designed to place more of the 

burden of the project on the universities so as to 

avoid some of the schedule and budget 

problems associated with the 2005 houses. 

First, instead of having NREL purchase and lend 

the teams the sensors and data acquisition 

equipment (at approximately $10K per house), 

the participating teams were required to 

purchase the equipment themselves. This 

enabled NREL to focus its efforts on system 

design, technical support to the students, 

installation assistance, and administration of the 

central data server. Teams had the option of 

letting NREL complete the entire installation 

without assistance from the university, or 

assigning one or more students to the project to 

help NREL complete the installation. In all 

cases, students from the universities were 

assigned to the project and made substantial 

contributions to the system design and 

installation. In two or more cases, the students 

involved used the systems to conduct their own 

research projects for class or master’s thesis 

credit. 

Second, a significant change was made to the 

project’s structure in regard to the schedule. 

Based on lessons learned from experiences with 

the 2005 houses, NREL now requires that teams 

finish reassembling the houses on their 

permanent sites before NREL performs postcompetition reinstallation and commissioning of 

the monitoring systems. This change will reduce 

the amount of time that NREL personnel have 

had to spend in making multiple site visits and in 

troubleshooting problems that could have been 

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avoided if the house had been fully assembled, 

finished, and occupied before the postcompetition monitoring equipment was 

scheduled to be installed and commissioned. 

4. Planned FY 2008 Activities 

•	 Continue monitoring the progress of the 

2007 teams as they reassemble their 

houses on their permanents sites. When 

reassembly is complete, NREL personnel 

will make a site to complete the system 

installation and commission it so that official 

data collection activities can begin and then 

continue without interruption. 

•	 Continue monitoring the progress of the 

2005 teams as they resolve the remaining 

issues with their houses. When these issues 

are resolved, system installation and 

commissioning will be completed so that 

official data collection activities can resume. 

If the remaining issues are not resolved, 

NREL’s equipment, which was on loan to 

the university, will be removed from the 

houses and returned to NREL. 

•	 Work with the NREL Web development 

team to publish real-time data displays on 

the Solar Decathlon Web site. 

•	 Develop computer models that will be 

calibrated after several months of official 

data collection have taken place. Results of 

analyses conducted with the aid of the 

calibrated computer models will begin to be 

available in late FY 2008, assuming that the 

houses are reassembled some time during 

the spring. 

•	 Recruit 2009 Solar Decathlon teams and 

Solar America Cities to participate in the 

project. 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

Building Integration 

Finance and Insurance 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Lawrence Berkeley National Laboratory (LBNL) 

Key Technical Contacts: Robert Margolis (NREL), 202-488-2222, robert_margolis@nrel.gov 

Karlynn Cory (NREL), 303-384-7464, karlynn_cory@nrel.gov 

DOE HQ Technology Manager: Charles Hemmeline, 202-586-6646, charles.hemmeline@ee.doe.gov 

FY 2007 Budgets: $240K (NREL) 

Objectives 

•	 Provide a series of photovoltaic (PV) application case studies illustrating how financing and 

insurance best practices were employed using specific examples. 

Accomplishments 

•	 Completed initial data gathering and analysis and began drafting report on state and local 

government financing of PV. This project was funded during the second half of FY 2007, so most 

of the work and products will be completed during FY 2008. 

Future Directions 

•	 Complete a series of papers on PV financing best practices for federal, state, and local 

governments as well as other sectors. 

1. Introduction 

Financing and insurance are critical components 

of almost all solar system purchases. Few areas 

can provide a more dramatic impact on the 

decision of a consumer, be it a utility, a 

commercial entity, or a homeowner, than financing 

mechanisms. Over the past few years, substantial 

innovations in the area of financing have helped 

facilitate PV purchases and installations. For each 

type of consumer, there are a wide variety of 

aspects to structuring financing. These include 

potential project revenues, such as renewable 

energy certificates (RECs), the availability of 

different financing mechanisms, federal and state 

incentives, and the rise of third-party financier 

models. The combination of these aspects results 

in a specific up-front expense for each consumer 

and ultimately substantially impacts their 

willingness to deploy solar PV. 

The insurance industry, like the financial 

community, suffers from misperceptions about 

solar and its risks. Insurance companies often 

require homeowners to purchase large liability 

policies, in case of an accident involving the solar 

system. These policies can be cost prohibitive to 

the homeowner and wind up killing the solar 

purchase altogether. Often such policy 

requirements are backed by little or no analysis, 

using old data. Insurance companies need to 

understand the characteristics and risks 

associated with current solar installations so that 

they can formulate analysis-based and reasonable 

company-wide policy requirements. 

2. Technical Approach 

This project will examine the current state of 

private lending and insurance requirements for 

solar system applications across various market 

sectors (federal, state, and local governments, 

residential buildings, and commercial industries) 

as well as various geographic areas in the United 

States. A series of reports focusing on issues 

related to financing photovoltaics systems will be 

carried out. These reports will identify and explain 

how financial complexity and options, such as 

state and federal incentives and the use of REC 

markets, differ within each sector. They will also 

include specific project and financing examples 

from across the United States. Additionally, these 

reports will provide recommendations for best 

methods and practices for a range of solar system 

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financing applications and sectors. As appropriate, 

the insurance requirements and barriers to 

implementation will also be outlined, by sector. 

3. Results and Accomplishments 

This project was funded during the second half of 

FY 2007, thus most of the work and products will 

be completed during FY 2008. 

4. Planned FY 2008 Activities 

The bulk of the work and deliverables for this 

project will be completed during FY 2008. In 

particular, the project will produce a series of solar 

application case studies illustrating how financing 

and insurance best practices were employed using 

specific examples. One or more of these case 

studies will: 

•	 Explain the state of private lending practices 

and insurance requirements for PV-system 

applications across the federal, state, and 

local government and residential, commercial, 

and industrial sectors; specific examples of 

projects and financial structures will be 

included that cover various geographic areas 

in the United States. 

•	 Identify successful novel financing 

mechanisms for PV-system applications and 

how they can be replicated, either for a niche 

application or when applied more broadly. 

Such novel approaches may include methods 

by which solar equipment manufacturers, 

utilities, and other solar technology or power 

providers are selling solar equipment (i.e. 

financing options) or power. 

•	 Identify leading innovators with respect to 

financing PV systems in the United States. 

•	 Evaluate the extent to which homeowner 

insurance policies cover residential PV 

systems in a fairly uniform or standard manner 

and identify any instances when excessive 

insurance requirements were changed to a 

more practical basis, with a discussion of the 

process used to bring about the change. 

•	 Evaluate the residual value of PV systems if a 

solar system is damaged and an insurance 

claim is paid out. 

As a set, the case studies will identify and explain 

the way that each of the following mechanisms is 

used to support solar project financing or 

insurance and examine their potential and impact. 

•	 Participating parties and ownership models 

such as power purchase agreements. 

•	 Compensation programs for the environmental 

attributes of solar power, such as renewable 

energy credits. 

•	 Clean renewable energy bonds and DOE loan 

guarantee program authorized by the Energy 

Policy Act of 2005 for large-scale solar-energy 

projects. 

•	 State programs such as system benefit 

charges that cover upfront investment 

incentives, production incentives, and lowinterest loans. 

•	 Utility involvement scenarios. 

•	 Residential green mortgage options. 

•	 Combination of solar and energy efficiency 

projects in single financing packages. 

•	 Financing systems for projects at federal, 

state, and other public facilities. 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Technical Partnerships 

Government Solar Installation Program 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Steven Palmeri (DOE), 303-275-4832, steve.palmeri@go.doe.gov 

Cecile Warner (NREL), 303-384-6516, cecile_warner@nrel.gov 

Vipin Gupta (SNL), 915-491-1158, vpgupta@sandia.gov 

DOE HQ Technology Manager: Charles Hemmeline, 202-586-6646, charles.hemmeline@ee.doe.gov 

DOE Golden Field Office, 

Solar Branch Chief: Carolyn Elam, 303-275-4953, carolyn.elam@go.doe.gov 

FY 2007 Budgets:	 $900K 

Objectives 

•	 Support federal agencies to achieve commitment to purchasing 2 gigawatts of solar power at 

federal facilities and 1 gigawatt at state and local facilities, with all transactions and installations to 

be completed by 2012 ahead of the final renewable energy purchase phase of the Energy Policy 

Act of 2005 (EPAct 2005). 

•	 Lower production costs for solar components through a market-based approach of using 

governmental energy needs to build demand for solar products and increase production. 

•	 Maximize installation of secure, on-site renewable energy projects at all DOE sites, optimize 

affordable purchases of renewable electricity by DOE facilities, or both. 

Accomplishments 

•	 Developed a model for a “Federal Photovoltaic Request for Proposals” vetted through financial 

and solar communities and the General Services Administration (GSA). 

•	 Initiated development of a dynamic “Government Solar Installation Program Web-Enabled Tool.” 

•	 Prepared a report technically defining the solar energy opportunities for federally-owned 

Congressional office buildings in Washington, D.C. 

•	 Prepared a report providing technical assessment of the potential for using solar energy and 

other key energy efficiency features as part of the Elephant House renovation in progress at the 

National Zoological Park in Washington, D.C. 

•	 Planned the “Federal PV Standard Offer Contract/Power Purchase Agreement with a Standard 

Lease” model for release during FY 2008. 

Future Directions 

•	 Continue assessments of governmental buildings and implementation of solar rooftop 

installations. 

•	 Work with the DOE Federal Energy Management Program (FEMP) to identify the best federal 

buildings where solar makes the most sense. 

•	 Begin a dialog with other federal agencies to help them identify locations where solar can be 

installed in a cost-effective manner on their buildings. 

1. Introduction increase their use of solar energy power. GISP 

is carried out in partnership with DOE’s 

The Government Solar Installation Program Transformational Energy Action Management 

(GSIP) is a market-based challenge to public (TEAM) Initiative, a department-wide effort 

entities—federal agencies, states, cities, aimed at reducing energy intensity across the 

counties, and other local governments—to nationwide DOE complex by 30%. GSIP is a 

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single program with a three-phased structure. In 

Phase One, DOE will evaluate DOE facilities for 

pilot sites for solar installations. In Phase Two, 

DOE will complete installations on the 

appropriate sites identified in Phase One. In 

Phase Three, DOE will work with other federal 

agencies to apply the lessons learned and assist 

other agencies with solar installations on their 

individual facilities. 

The major partners in the GSIP are the DOE 

Solar Energy Technologies Program (SETP), 

DOE Federal Energy Management Program 

(FEMP) and General Services Administration 

(GSA). The organization’s roles include: 

SETP 

•	 Take primary responsibility for the Phase 

One pilot installations. 

•	 Participate in decision-making on solar 

TEAM projects in Phase Two. 

•	 Provide technical assistance to GSA in 

Phase Three. 

FEMP 

•	 Provide government energy procurement 

assistance to SETP in Phase One. 

•	 Take primary responsibility for Phase Two 

installations to complete the TEAM effort. 

•	 Assist with Phase Three energy purchases. 

GSA 

•	 Provide procurement vehicles for Phase 

One power purchase agreements (PPAs). 

•	 Develop a Web portal with strong SETP 

input. 

•	 Take primary responsibility for Phase Three 

procurements with DOE support. 

Technical assistance teams, also known as 

Tiger Teams, provide any needed assistance 

and are comprised of representatives from the 

national laboratories (NREL and SNL) as well as 

New Mexico State University and the University 

of Central Florida. 

Agreement Title FY 2007 

Budget ($K) 

National Renewable Energy 

Laboratory 600 

Sandia National Laboratory 300 

2. Technical Approach 

The GSIP initiative meets or exceeds energy 

efficiency goals mandated by EPAct 2005, as 

well as Executive Order 13423, directing federal 

agencies to: 

•	 Reduce energy intensity and 

greenhouse gas emissions 

•	 Increase energy efficiency and use of 

renewable energy technologies 

•	 Adopt sustainable design practices 

•	 Reduce petroleum use in federal fleets. 

This initiative adopts a more ambitious timeline 

and targets changes that will have an impact on 

DOE’s energy use as early as next year. 

GSIP is a single program with a three-phased 

structure: Phase One includes DOE facilities 

and will collaborate with DOE’s TEAM Initiative. 

The TEAM Initiative is a nationwide effort to 

reduce energy intensity by 30% in DOE 

buildings. This energy reduction will save 

approximately $90 million in taxpayer dollars per 

year, after projects are paid for. The TEAM 

Initiative aims to meet or exceed the aggressive 

goals for increasing energy efficiency throughout 

the federal government as stated in the 

executive order. 

Phase Two will focus on the most appropriate 

sites for solar applications identified during 

Phase One. The GSIP program approach is to 

use power purchase agreements, except where 

straight purchases are more cost effective. The 

program will initially emphasize solar 

installations in regions of the country with 

regulations or incentives in place, conducive to 

solar energy projects, such as in California and 

New Jersey. The program will then transition to 

other regions as the cost of PV falls and other 

state or local incentives for renewable energy 

develop. 

Phase Three of the GSIP broadens the effort to 

include other federal agencies beyond DOE, as 

well as state and local governments. Lessons 

learned during the first two phases of the 

program will be useful for helping other agencies 

to overcome barriers to solar installations. 

The strategic approach of the GSIP is to: 

•	 Leverage federal purchase power to create 

significant demand pull. 

•	 Promote U.S.-manufactured products. 

•	 Promote an installation development model 

using a power purchase agreement model. 

•	 Increase demand for installers and thereby 

boost U.S. jobs. 

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•	 Facilitate achievement of EPAct and other 

federal goals by using a market-based 

approach rather than regulation. 

•	 Use growing capital markets to finance 

installations. 

•	 Support domestic power purchase 

agreement providers. 

•	 Facilitate the process by minimizing 

government involvement. 

3. Results and Accomplishments 

GSIP was initiated during FY 2007. An initial 

project is to install PV panels on the Forrestal 

Building, the DOE’s Headquarters Building in 

Washington, DC. Installation began late in FY 

2007 and is expected to be completed in FY 

2008. As part of Phase One, processes for 

evaluating additional projects were identified in 

preparation for additional installations. 

A Tiger Team of solar experts from NREL, SNL, 

and the Florida Solar Energy Center prepared 

an assessment report of the U.S. Capitol 

Complex, detailing each building’s energy 

consumption and potential solar PV installations. 

The following buildings were identified for 

consideration: 

•	 Rayburn House Office Building 

•	 Cannon House Office Building 

•	 Ford House Office Building 

•	 House Page Dorm 

•	 House Parking Lot 

•	 Longworth House Office Building 

•	 Dirksen Senate Office Building 

•	 Hart Senate Office Building 

•	 Russell Senate Office Building and Senate 

Child Care 

• Adams Building 

•	 Madison Memorial Building. 

In addition, the team assessed the potential for 

using solar energy and other key energy 

efficiency features as part of the Elephant House 

renovation in progress at the National Zoological 

Park in Washington, D.C. This assessment also 

analyzed the feasibility of using solar water 

heating in the Elephant House renovation. 

4. Planned FY 2008 Activities 

•	 Release of a model “Federal Photovoltaic 

Request for Proposals and a Federal 

Photovoltaic Standard Offer Contract / 

Power Purchase Agreement with Standard 

Lease” with input from the GSA and the 

financial and solar communities. 

•	 Release of a dynamic “Government Solar 

Installation Program Web-Enabled Tool” that 

will allow industry to examine facility 

characteristics, submit inquiries, and place 

bids. Successful bids will be transferred 

automatically into “Federal PV Standard 

Offer Contract’ format for further negotiation. 

•	 Continue Tiger Teams efforts to implement 

some of the plans proposed in the reports 

completed in FY 2007. 

5. Major FY 2007 Publications 

•	 U.S. Department of Energy Solar and 

Renewables Tiger Team, “Energy Efficiency 

and Renewable Energy Recommendations: 

National Zoological Park, Asia Trail, Phase 

II, Elephant Trails.” (April 13 2007). 

•	 A. Walker, W. Cox, and S. Barkaszi, 

“Architect of the Capitol Solar Energy 

Assessment Project: Assessment of the 

United States Capitol Complex for 

Application of Solar Energy Technologies,” 

Prepared by NREL, SNL, and FSEC, 

(October 1, 2007). 

6. University Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

New Mexico State University 

Andy Rosenthal 

Las Cruces, NM 

303-275-4864 

arosenthal@nmsu.edu 

Technical assistance teams, also known as Tiger 

Teams, provide any needed assistance and are 

comprised of representatives from the national 

laboratories (NREL and SNL) as well as 

universities. Florida Solar Energy Center 

Robert Reedy 

University of Central 

Florida 

reedy@fsec.ucf.edu 

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____________________________________________________________________________________ 

Technical Partnerships 

Solar America Cities 

Performing Organizations:	 Cities: Ann Arbor, MI; Austin, TX; Berkeley, CA; Boston, MA; Madison, WI; 

New Orleans, LA; New York, NY; Pittsburgh, PA; Portland, OR; Salt Lake 

City, UT; San Diego, CA; San Francisco, CA; and Tucson, AZ 

Key Technical Contacts:	 Margie Bates, (DOE/GO), 303-275-4845, margie.bates@go.doe.gov 

Carla Clemons (DOE/GO), 303-275-4864, carla.clemons@go.doe.gov 

Steve Palmeri (DOE/GO), 303-275-4832, steve.palmeri@go.doe.gov 

DOE HQ Activity Manager:	 Thomas Kimbis, 202-586-000, tom.kimbis@ee.doe.gov 

FY 2007 Budgets:	 $2.5M (DOE), $2.5M (Technical Assistance from Labs) 

Objectives 

•	 Issue competitive funding opportunity announcement (FOA) to form strategic partnerships with U.S. 

cities as part of DOE’s Solar America Initiative (SAI). These partnerships are intended to accelerate 

the adoption of solar technology at the local level by engaging city governments, key intermediaries 

to other end users within their jurisdiction, and regulatory entities. 

•	 Provide financial assistance awards (cooperative agreements) of $200,000 each to 13 cities with 

populations of 100,000 or more to propose activities that support the objectives of DOE and SAI 

market transformation activities. 

•	 Provide up to $200,000 in tailored technical assistance from DOE national laboratories and 

contractors to each of the recipient cities to accomplish the project goals. 

Accomplishments 

•	 Established strategic partnerships with 13 cities through a competitive funding opportunity. 

•	 Awarded a combined $2.5 million in financial assistance (cooperative agreements). 

•	 Held kickoff meetings with each city publicizing the plans for each Solar America City. 

•	 Developed and initiated tailored technical assistance for each of the cities from national labs 

(National Renewable Energy Laboratory, Sandia National Laboratories), Florida Solar Energy 

Center, or New Mexico State University. 

Future Directions 

•	 City of Ann Arbor will identify and reduce barriers to solar, propose commercial and residential solar 

installations, integrate energy efficiency and renewable energy into K-12 curriculum and develop 

solar installer training. 

•	 City of Austin will work to reduce information barriers that prevent citizens from participating in the 

city’s extensive renewable energy and energy conservation programs and will install highly-visible 

solar energy facilities at public schools. 

•	 City of Berkeley will develop and implement a turn-key program to install solar photovoltaic (PV) 

and solar hot water and air heating (SWAH) systems in the residential and small-to-medium 

commercial/public sectors. 

•	 City of Boston anticipates that the city-wide installation proposed for 2008-2010 to be managed by 

the Solar Boston Partnership’s non-profit successor entity will result in the installation of 2-

megawatt (MW) capacity with ongoing capacity to manage at least 10 MW by 2015. 

•	 City of Madison will be working towards achieving its goal of 250 kilowatts (kW) of PV and 200 solar 

hot water systems installed by 2010. 

•	 City of New Orleans will initiate a publicity and outreach program to induce demand for solar among 

individuals, businesses, and institutions, analyze and recommend modifications and enhancements 

to the city’s codes, regulations, and policies in order to foster the adoption of solar technologies. 

•	 City of New York will use the City’s resources to spur the market and create economies of scale to 

lower prices. 

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___________________________________________________________________________________ 

•	 City of Pittsburgh will encourage adoption of solar energy by residential- and small-scale 

commercial users to demonstrate that the technology will lower their energy bills in the long run. 

•	 City of Portland will provide high level policy support to solar market transformation and streamline 

city-level regulations and practices that affect solar adoption. 

•	 Salt Lake City will design a comprehensive city and county-wide solar implementation plan to 

develop an additional 10,000 government, residential, and commercial installations by 2015. 

•	 City of San Diego will update and expand GIS analysis of solar installations and potential future 

sites, conduct performance analysis of around 12 MW of existing PV systems and develop case 

studies that explain the process used for designing, planning, installing and monitoring solar energy 

systems and provide energy and financial analyses. 

•	 City of San Francisco will identify sites for large installations and marketing to those building 

owners. 

•	 City of Tucson will work towards a Solar Energy Integration Plan, a Greater Tucson Solar Energy 

Development Plan and 2 MW to be installed by 2015. 

1. Introduction 

In January 2006, the President announced his 

Advanced Energy Initiative, which “provides for a 

22-percent increase in funding for clean-energy 

technology research at the Department of Energy. 

An integral part of this Initiative is the U.S. 

Department of Energy’s (DOE’s) Solar America 

Initiative (SAI). The goal of the SAI is to reduce 

the cost of solar photovoltaic (PV) technologies so 

that they become cost-competitive by 2015. SAI 

represents a significant enhancement of DOE’s 

business strategy of partnering with key 

stakeholders to accelerate commercialization of 

PV system research and development (R&D) to 

meet aggressive cost and installed capacity goals. 

To learn more about SAI, visit 

www.eere.energy.gov/solar/solar_america/index.html 

To complement the R&D and testing/evaluation 

activities that are the backbone of SAI, DOE 

conducts Market Transformation (MT) efforts, with 

a mission to reduce market barriers and promote 

market expansion of solar energy technologies 

through non-R&D activities. MT activities fall into 

two areas: (1) activities which provide technical, 

regulatory, institutional, financial and educational 

solutions to MT barriers; and (2) those which 

accelerate demand for new solar technologies 

primarily through provision of technical assistance. 

There are several aspects to SAI MT that define it 

as a new approach for DOE: 

•	 SAI MT is looking to identify and remove 

market barriers. Through its infrastructure 

development activities, DOE is seeking to 

identify and minimize or remove barriers to 

solar technology commercialization as quickly 

and efficiently as possible. 

•	 SAI MT is looking for significant market 

changing activities. Given the proximity of the 

2015 goal, DOE is seeking to make large and 

significant changes in the marketplace through 

its market transformation activities. 

•	 SAI MT is focused on near- and mid-term 

results. Accordingly, emphasis will be on 

projects and activities with the greatest 

potential to assist the DOE in reaching its SAI 

cost-competitiveness goal by 2015. 

•	 SAI MT is looking for performers and partners 

who are committed to the SAI mission. In 

order to achieve the SAI mission of 2015, 

DOE is inclined to partner and work with 

motivated entities that will also benefit from 

achievement of the SAI mission. 

Solar technologies addressed under this FOA 

included PV, concentrating solar power (CSP), 

and solar water/air heating technologies (SWAH). 

2. Technical Approach 

Cities play an important strategic role in SAI and 

present unique challenges and opportunities for 

solar market transformation. DOE recognizes the 

important role of Cities as champions of 

progressive energy efficiency and renewable 

energy efforts and wishes to support their bold and 

innovative approaches to accelerate solar 

technology adoption at the local level. 

Through Solar America Cities (SAC), DOE seeks 

to support Cities ready to take a comprehensive, 

systemic, city-wide approach to solar technology 

that facilitates mainstream adoption and provides 

a model for other cities. Consistent with the 

mission of SAI, DOE is looking for Cities to commit 

to achieving a sustainable solar infrastructure, not 

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simply a year or two of experimental solar 

projects. It was critical for each city to express a 

commitment to a city-wide approach to integration 

of solar energy into city planning and processes, 

as well as to large-scale implementation of solar 

technologies by 2015. 

Such an approach recognizes the city’s role as an 

important end user of electricity, as a key 

intermediary to other end users within their 

jurisdiction, and as a regulatory entity. DOE 

expected cities to develop a fully-scoped, city-wide 

solar implementation plan as a deliverable under 

this project. Each city-wide solar plan addressed 

efforts to: 

•	 Integrate solar technology into city energy 

planning and facilities. 

•	 Streamline city-level regulations and practices 

that affect solar adoption by residents and local 

businesses (e.g. permitting, inspections, local 

codes). 

•	 Promote solar technology among residents and 

local businesses (e.g., outreach, curriculum 

development and/or implementation, incentive 

programs, etc.). 

Solar America Cities build on the networks and 

momentum of former Million Solar Roofs 

partnerships, and DOE encouraged their 

participation in this activity. To ensure maximum 

impact, cities were required to submit a letter of 

support from their mayors and local utilities. 

3. Results and Accomplishments 

The Awards 

On June 21, 2007, DOE named 13 cities as 

inaugural Solar America Cities. In September 

2007, the DOE Golden Field Office awarded a 

combined $2.5 million in federal financial 

assistance to Solar America Cities. 

Each of these cities submitted a proposal outlining 

its plans to build a sustainable solar infrastructure, 

streamline city-level regulations, and promote the 

adoption of mainstream solar technology among 

residents and businesses. Cites were selected 

competitively. Evaluation criteria focused on 

demonstrating a comprehensive city government 

approach to solar planning, including methods to 

further market expansion and to remove local 

market barriers. Selected cites demonstrated a 

high level of commitment to promote solar power 

throughout the city, involving local government 

officials, utilizes private partners. 

Winning Cities for 2007 

The winning cities for 2007 are the following: 

Solar City 2007 FY 2007 Budget 

($K) 

Ann Arbor, MI $200,000 

Austin, TX $186,930 

Berkeley, CA $200,000 

Boston, MA $150,000 

Madison, WI $200,000 

New Orleans, LA $200,000 

New York , NY $190,140 

Pittsburgh, PA $200,000 

Portland, OR $200,000 

Salt Lake City, UT $197,286 

San Diego, CA $200,000 

San Francisco, CA $200,000 

Tucson, AZ $200,000 

Of these 13 cities, eight are among the largest 50 

cities in the United States. 

On-Site Technical Assistance 

In their proposals, each city identified the technical 

assistance their project might require in areas 

such as city planning, technology selection, project 

financing, building codes, architecture and 

community outreach. 

Following the award, DOE appointed a technical 

assistance lead, called a Tiger Team leader to 

each city. The tiger team lead contacted the 

appropriate person at each city to discuss their 

project’s technical assistance needs and then 

conducted a site visit to identify specific technical 

assistance needs, resulting in the optimal 

composition of the Tiger Team and in the 

development of a 2-year project plan. 

Members of the Tiger Team were drawn from the 

National Renewable Energy Laboratory (NREL) in 

Colorado, Sandia National Laboratories (SNL) in 

New Mexico, and the Southwest and Southeast 

Regional Experiment Stations (RESs) at New 

Mexico State University, and the Florida Solar 

Energy Center. 

Technical Assistance MOA 

The DOE Golden Field Office developed a 

Technical Assistance Memorandum of Agreement 

(MOA) with each city that includes the 2-year 

technical assistance project plan, establishes the 

framework for cooperation, and sets the value of 

the technical assistance. The MOA is between the 

City, the Tiger Team lead organization, and DOE. 

The MOA is being implemented by the Golden 

Field Office. 

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SAC Goals and Project Highlights 

“Ann Arbor Solar City Partnership” 

Goals: Help the city reach its goal of 20% 

renewable energy by 2015 by utilizing a wide 

range of community partners and resources to 

remove market barriers to the adoption of solar 

energy. Help local solar manufactures and 

contractors to increase business. 

Project Highlights: Develop a comprehensive 

solar plan. Hold solar informational workshops for 

consumers and installers. Implement a 

community-based marketing campaign. Offer city 

incentives and rebates for installations. 

“Austin Solar City Partnership” 

Goals: Educate the city’s teachers and youth 

about the benefits of solar. Reduce barriers that 

prevent participation in the city’s renewable energy 

and energy conservation programs. Increase 

solar installation visibility. Establish benchmarks 

for distributed and central solar to be integrated 

into Austin Energy’s generation plan. 

Project Highlights: Install solar energy systems 

in local schools and develop curricular materials to 

accompany these systems. Work with local nonprofits to promote and cross-market the solar, 

energy efficiency and green building programs of 

Austin Energy. Assess the rooftop area suitable 

for solar development. Assess the potential for 

hybrid solar/wind installations. 

“Berkeley Smart Solar Program: A Partnership 

to Serve the East Bay” 

Goals: Increase the market share of solar energy 

technologies in the residential and small- and 

medium-commercial sectors in the East Bay. 

Build local capacity by working with local 

suppliers, installers, trade associations, and 

financiers. 

Project Highlights: Develop and implement a 

pilot turn-key program to install 142 kW of PV 

installations at 10 residential and 5 commercial 

sites, as well as 10 large solar hot water and air 

heating systems. Launch a partnership with 

PG&E East Bay Energy Watch to expand depth of 

utility services provided. Annually install 800 kW of 

PV and 24,000 therms of thermal projects. 

“Solar Boston” 

Goals: Examine barriers to widespread solar 

deployment and develop a strategy for installing 

solar throughout Boston. Coordinate resources 

and best practices of Boston with DOE, the 

Commonwealth of Massachusetts, utilities, 

electrical workers’ unions, industry and others. 

Create a non-profit organization to accomplish the 

goals of the solar partnership members. 

Project Highlights: Map feasible locations for 

solar installations and market solar energy to 

prime sites. Prepare a project-labor agreement. 

Plan city-wide bulk purchase, financing, and 

installation of solar technology. 

“Midwest Solar City Model (MadiSUN)” 

Goals: Coordinate and galvanize substantial local 

and state resources to showcase how a Midwest 

City can dramatically increase the use of solar 

energy. Establish a 2-year program, MadiSUN, to 

provide an ongoing commitment to sustainability. 

Project Highlights: Double solar energy 

utilization in Madison by lowering transaction costs 

to help building owners buy solar. Review and 

modify the City’s procedures and policies for solar 

permitting and installation to be more supportive of 

solar systems. 

“New Orleans Solar Cities Initiative” 

Goals: Accelerate the adoption of solar 

technology by partnering with DOE. Include solar 

technology in the construction and renovation of 

new homes and businesses wherever applicable 

and economically feasible. 

Project Highlights: Implement a publicity and 

outreach plan to increase demand for private 

solar. Evaluate and modify city regulations 

hindering the use of solar technologies and install 

solar on city government properties. Develop 

incentives that support solar technology in 

residential developments. Conduct outreach to 

develop a solar supply base in New Orleans. 

 “Solar City Strategic Partnership: NYC Solar” 

Goal: Achieve large-scale solar energy market 

growth that complements long-term sustainability 

planning efforts and the City’s greenhouse gas 

reduction goals. 

Project Highlights: Develop a long-term solar 

energy plan. Conduct a feasibility study of realtime pricing for PV net metering. Evaluate how to 

integrate solar into emergency planning and 

demand reduction programs. Create new 

municipal solar energy incentives. Address 

interconnection and code barriers through a 

collaborative stakeholder process. 

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“The Pittsburgh Solar Initiative” 

Goal: Build on Pittsburgh’s reputation as a 

national leader in green practices by developing a 

distributed approach to solar adoption, as a model 

for other northern cities. 

Project Highlights: Power traffic lights along 

main roads with solar power to eliminate their 

consumption of brown power and ensure they 

remain operational during a blackout. Incorporate 

solar on new construction in two city parks. 

Sponsor Carnegie Mellon’s entry into the Solar 

Decathlon. 

“Portland Solar Now!” 

Goal: Build on its longstanding commitment to 

renewable energy by launching a robust program 

to facilitate the widespread adoption of solar 

technology and establish Portland as a leader in 

solar energy. 

Project Highlights: Develop a marketing plan to 

assist property owners with the technical process 

of implementing solar technologies and applying 

financial incentives to make solar more affordable. 

Align City policies to promote solar technology by 

examining how to power municipal operations with 

solar, removing regulatory barriers, and adopting 

policies to encourage the use of solar technology. 

“Solar Salt Lake” 

Goal: Develop a fully-scoped city and countylevel implementation plan to facilitate an additional 

10 MW of solar PV installations by 2015 and serve 

as a model for other cities integrating solar into 

their policy, planning, and processes. 

Project Highlights: Identify and reduce barriers 

to solar deployment in Salt Lake City and County. 

Implement a comprehensive plan for Salt Lake 

City and County that establishes a long-term 

commitment to solar deployment. Partner with 

private entities, including land developers, to 

advance residential solar installations in new 

housing developments. 

“San Diego Sustainable Energy 2050 Plan” 

Goal: Provide a blueprint for the nation by 

creating an energy infrastructure that is diversified, 

reliable, and as self-contained as possible, as they 

advance the Solar America Initiative. 

Project Highlights: Update GIS analysis of solar 

installations and potential sites. Conduct 

performance analysis of approximately 12 MW of 

existing PV. Produce outreach materials to 

stimulate a robust project pipeline in the city. 

Develop a citywide solar implementation plan. 

Study the impact of solar on property value/resale. 

Develop 3 case studies to explain solar energy 

systems from design to use. 

“Solar San Francisco” 

Goals: Realize the City’s ambitious renewable 

energy goals established in its Electricity 

Resource Plan by targeting barriers facing solar 

technology market penetration. 

Project Highlights: Develop a program to group 

commercial customers into one or larger, 

aggregated purchasing pools to be marketed to 

different types of perspective solar installers. 

Identify sites for large installations and marketing 

the prospects to building owners. Develop a plan 

to tackle problems with installing solar on multitenant buildings. 

“Tucson Solar Initiative” 

Goals: Expand the Tucson solar energy market 

through accelerated investments and establish a 

mechanism for sustainable solar energy 

integration for the next ten years. Transform 

knowledge and financing market barriers into 

opportunities for solar installations. 

Project Highlights: Implement a City of Tucson 

Solar Energy Integration Plan and a Greater 

Tucson Solar Energy Development Plan. 

Enhance financing techniques for large-scale solar 

energy installations. Develop and disseminate 

solar best practices and other outreach. 

4. Planned FY 2008 Activities 

• Issue competitive funding opportunity 

announcement (FOA) and award financial 

assistance to approximately 12 additional U.S. 

Cities to form strategic partnerships. 

•	 Begin to implement technical assistance 

activities to help cities achieve their goals. 

•	 Provide for additional technical assistance 

resources for new cities. 

•	 Implement planned activities by cities that 

include comprehensive, systemic, city-wide 

approaches to solar technology that facilitates 

mainstream adoption and provides a model for 

other cities. 

•	 Hold annual meeting to bring together cities to 

share best practices and lessons learned. 

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5. Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

National Renewable Energy 

Laboratory 

Cecile Warner 

Golden, CO 80401-3393 

303-384-6516 

cecile_warner@nrel.gov 

Technical Assistance for Solar 

America Cities 2007 

Sandia National Laboratories 

Vipin Gupta 

Albuquerque, NM 87185 

915-491-1158 

vpgupta@sandia.g 

Technical Assistance for Solar 

America Cities 2007 

New Mexico State University 

Andy Rosenthal 

Las Cruces, NM 88003-8001 

303-275-4864 

arosenthal@nmsu.edu 

Technical Assistance for Solar 

America Cities 2007 

Florida Solar Energy Center 

Robert Reedy 

Cocoa, FL 32922-5703 

321-638-1000 

reedy@fsec.ucf.edu 

Technical Assistance for Solar 

America Cities 2007 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Technical Partnerships 

Solar America Showcases 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

 New Mexico State University (NMSU) 

 Florida Solar Energy Center (FSEC) 

Key Technical Contacts:	 Cecile Warner (NREL), 303-384-6516, cecile_warner@nrel.gov 

Vipin Gupta (SNL), 915-491-1158, vpgupta@sandia.gov 

Andy Rosenthal, (NMSU), 303-275-4864, arosenthal@nmsu.edu 

Robert Reedy, (FSEC), reedy@fsec.ucf.edu 

DOE HQ Technology Manager:	 Charlie Hemmeline, 202-586-6646, charles.hemmeline@ee.doe.gov 

DOE Golden Field Office, 

Solar Project Officer: Steve Palmeri, 303-275-4832, steve.palmeri@go.doe.gov 

FY 2007 Budgets: $1,000K 

Objectives 

•	 Accelerate demand for solar technologies among key end-use sectors. 

•	 Assist in creating high visibility solar projects that increase public awareness of solar power. 

•	 Create replicable, large-scale projects that can become models for other U.S. entities. 

Accomplishments 

•	 Forest City Military Communities Project 

o	 DOE’s Technical Assistance Team supported the Forest City Military Communities to 

create a real estate project that will showcase the wider adoption of solar technology. 

This project is a public-private joint venture with the Department of Navy to build or 

refurbish 6,500 homes for military families on U.S. naval and marine bases in Hawaii. 

•	 Orange County Convention Center (OCCC) Project 

o	 DOE’s Technical Assistance Team provided assistance to the OCCC, in partnership with 

the Orlando Utilities Commission (OUC), to plan the installation of a nominal onemegawatt (MW) photovoltaic (PV) system on the roof of and in the area surrounding its 

North-South Building. The system will include a large rooftop system, as well as four 

experimental systems showcasing new technologies at ground-level for public viewing. 

•	 San Jose City Project: 

o	 DOE’s Technical Assistance Team provided support to the City of San Jose in identifying 

city-owned buildings (8) that may be suitable for solar installations. These locations are 

highly visible in the San Jose downtown area and have the potential for up to two MW of 

total solar power. 

Future Directions 

The Solar America Showcase Project will continue to seek solar projects to support in fiscal year (FY) 

2008 that accelerate demand for solar technologies. 

1. Introduction large-scale, high-visibility solar installation projects 

that have the ability to impact the market for solar 

The purpose of Solar America Showcases (SAS) technologies through large project size, use of a 

is to accelerate demand for solar technologies novel solar technology, and/or use of a novel 

among key end-use market sectors. Under this application for a solar technology. In addition, it is 

activity, DOE will provide technical assistance to desired that the project be replicable or have 

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replicable components. Although It is not 

expected that projects meet all of these 

parameters, ideally projects should reflect some or 

most of these qualities. Large-scale installations 

may include PV, concentrating solar power (CSP), 

and solar water heating (SWH) applications. 

DOE will not purchase hardware or provide direct 

funding to organizations selected for this 

assistance. 

The types of installations DOE is looking to 

support are described in the following paragraphs: 

Regarding the scale of the project, DOE is looking 

for projects with total capacity in excess of 100 

kilowatt (kW). Projects may include multiple sites 

and do not have to be co-located. In addition to 

the initial installation, the kW total may also 

include planned follow-on activities (direct 

replication efforts). Examples include installations 

in residential subdivisions, shopping centers, office 

buildings or parks, big box retail locations, 

factories, and utility solar production. 

Regarding the visibility of the project, DOE 

anticipates projects that are centrally located in 

towns, are sited near highly trafficked vehicle or 

pedestrian areas, house hundreds of residents or 

workers, are a part of an area frequented by 

tourists, are part of a popular public destination 

(e.g. shopping centers, courthouses, etc.), or have 

some other high visibility component. The project 

would also have an outreach component that 

provides information about the installation. 

Regarding the novel solar technology, DOE 

proposes to support projects that introduce new 

solar technologies that hold the promise of 

reducing initial costs, simplifying installation, and 

boosting consumer confidence, but which have 

little testing to date that demonstrates such 

improvements. Examples include new cell or 

module technology, new materials, or innovative 

installation and mounting techniques. By offering 

technical assistance, DOE envisions helping these 

new solar technologies develop a performance 

record in the marketplace, identify technical 

problems early in mass product releases, and 

devise solutions and alternatives that move 

specific solar technologies to cost-competitiveness 

by 2015. 

Regarding the novel solar application, DOE 

expects to support projects that utilize solar 

technology in new ways. One example would be 

to include new methods of building integration 

beyond traditional roof-mounted modules. DOE 

also supports innovative designs and methods that 

open up previously untapped markets or end uses 

to solar technology adoption. Acceptable solar 

applications could also include those that are used 

in other geographic areas but not in the vicinity 

(state or region) of the proposed site. 

Regarding replicability, DOE expects to support 

projects that can either be replicated by the entity 

requesting the technical assistance or by others. 

The entire project should be replicable, or have 

replicable components, unless installations are of 

an extremely large size that justifies DOE support 

without replicability. Replication of projects is a 

critical component to advance solar 

commercialization. 

2. Technical Approach 

SAS awarded technical assistance to four 

organizations. These organizations represented a 

broad spectrum of applications with cross-cutting 

issues that allowed the SAI to work on several 

barriers. These barriers included: 

•	 Addressing financing barriers for solar 

applications in a municipality. 

•	 Creating an RFP that municipalities can use 

for soliciting bids on solar installations. 

•	 Developing an economically sound model for 

doing site surveys across a large housing 

complex. 

•	 Researching inverter location and 

interconnection issues. 

•	 Developing protocols for acceptance testing 

and commissioning processes on new solar 

installations. 

3. Results and Accomplishments 

For the Forest City Military Communities Project, 

the Technical Assistance Team accomplished the 

following: 

•	 Provided technical and economic analyses as 

well as design recommendations for use of PV 

technologies on Forest City’s five warehouse 

properties, adjacent to the airport. 

•	 Completed technical recommendations on 

performance monitoring of SHW heating 

systems. 

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•	 Authored a report on ‘Solar Ready’ 

specifications for residential housing. 

•	 Provided a formal technical report on hybrid 

PV/thermal systems for cooling. 

•	 Completed a site evaluation and solar survey 

on public-private venture housing areas and 

technical recommendations on construction of 

PV solar farms in open spaces, residential PV 

“in-fill,” “PV on skids” in land bank areas, PV 

on community centers, PV on warehouses, PV 

integration on new residential 

rooftops/carports, rapid PV retro-fit of housing 

units, and adoption of solar thermal cooling 

systems in community centers. 

For the Orange County Convention Center 

(OCCC) Project, the Technical Assistance Team 

accomplished the following: 

•	 Assessed the feasibility of the OCCC site for 

the planned five PV systems. 

•	 Developed specifications for the OCCC to use 

for the bid process and assisted the OCCC in 

determining the systems best suited for the 

site. 

•	 Developed educational materials for the 

Climate Change Education Center, which is 

the core of the publicity and outreach program, 

designed to increase demand for solar among 

individuals, businesses, and institutions 

throughout the state. 

For the City of San Jose Project, the Technical 

Assistance Team accomplished the following: 

•	 Conducted site evaluations on the 

appropriateness for solar electric (photovoltaic 

or PV) and solar thermal systems at selected 

city sites. 

•	 Provided project financing and procurement 

options evaluation and recommendation. 

•	 Assisted with procurement language, contract 

negotiations, and design review on selected 

solar installations for the City of San Jose. 

4. Planned FY 2008 Activities 

•	 Issue FY 2008 competitive Notice of Technical 

Assistance and award Technical Assistance to 

up to 15 organizations. 

•	 Complete the second phases of the Forest 

Cities Military Communities Project, Orange 

County Convention Center Project, and City of 

San Jose Project. 

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____________________________________________________________________________________ 

 

____________________________________________________________________________________ 

Technical Outreach 

State and Utility Outreach 

Performing Organizations: National Conference of State Legislatures

 Clean Energy Group

 National Association of Regulatory Utility Commissioners 

Solar Electric Power Association 

Key Technical Contact:	 Steve Palmeri, 303-275-4832, steve.palmeri@go.doe.gov 

DOE HQ Technology Manager:	 Charlie Hemmeline, 202-586-6646, charlie.hemmeline@hq.doe.gov 

FY 2007Federal Budgets:	 $247,500 National Conference of State Legislatures 

$247,500 Clean Energy Group, Inc. 

$203,004 National Association of Regulatory Utility Commissioners 

$614,780 Solar Electric Power Association 

Objectives 

•	 Build relationships with State decision-makers (such as State legislatures, energy offices, public 

utility commissions and air quality offices) responsible for enacting policies, programs, and plans 

that are key drivers for solar technology market transformation. 

•	 Provide key state actors with solar best practices and up-to-date, accurate information about 

solar technology characteristics. 

•	 Enlist the assistance of a utility membership organization to deliver key technical and 

informational assistance to utilities to promote their acceptance and use of solar.
 

Accomplishments 

•	 National Conference of State Legislatures Solar State Legislation 

(www.ncsl.org/programs/energy/energypolicy.cfm) was created to provide a readily accessible 

database of current and previous years' bills on energy issues. The database is searchable by 

energy topic and by state. 

•	 Clean Energy Group, Inc. launched the program Web site (www.statesadvancingsolar.org) that 

serves as a resource for state policy makers and decision makers interested in developing a solar 

program. 

•	 The National Association of Regulatory Utility Commissioners released the "Solar Energy 

Technology and Policy Reference Guide" (www.naruc.org/programs.cfm?c=Domestic), which 

includes information on Solar regulatory policies, technologies, and state and industry 

perspectives. 

•	 Solar Electric Power Association released “The Peer Matching Online Tool” 

(www.solarelectricpower.org/peer/), a service to share information and best practices to help all 

utilities improve their solar programs. The database is searchable by location, utility type, 

experience, or by solar program type. 

Future Directions 

•	 National Conference of State Legislatures will continue working on ongoing LegisBriefs and Solar 

Energy Institute sessions, as well as the solar energy database for solar legislators. 

•	 Clean Energy Group, Inc. is planning to develop a state solar program survey. 

•	 The National Association of Regulatory Utility Commissioners plans to hold a regional dialogue 

for the Northeast and Mid-Atlantic to examine the regional solar initiative. 

•	 Solar Electric Power Association is planning to develop a Solar Program Options Tool (SPOT) 

and an Online Resource Library. 

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1. Introduction 

In January 2006, the President announced his 

Advanced Energy Initiative, which “provides for a 

22% increase in funding for clean-energy 

technology research at the U.S. Department of 

Energy (DOE). To change how we power our 

homes and offices, we will invest more in zeroemission coal-fired plants, revolutionary solar and 

wind technologies, and clean, safe nuclear 

energy.”1 

An integral part of this Initiative is DOE’s Solar 

America Initiative (SAI). The goal of SAI is to 

reduce the cost of solar photovoltaic (PV) 

technologies so that they become cost-competitive 

by 2015. SAI represents a significant 

enhancement of DOE’s business strategy of 

partnering with key stakeholders to accelerate 

commercialization of PV systems R&D to meet 

aggressive cost and installed capacity goals. To 

learn more about SAI, visit 

www.eere.energy.gov/solar/solar_america/index.ht 

ml. 

To complement the R&D and testing/evaluation 

activities that are the backbone of SAI, DOE will 

conduct Market Transformation2

 (MT) efforts, with 

a mission to reduce market barriers and promote 

market expansion of solar energy technologies 

through non-R&D activities. MT activities fall into 

two areas: (1) activities which provide technical, 

regulatory, institutional, financial, and educational 

solutions to market transformation barriers; and (2) 

those which accelerate demand for new solar 

technologies, primarily through technical 

assistance. 

There are several aspects to SAI that define it as a 

new approach for DOE: 

• SAI MT is looking to identify and remove market 

barriers. Through its infrastructure development 

activities, DOE is seeking to identify and minimize 

1 President George W. Bush, Advanced Energy 

Initiative, The White House National Economic 

Council, Feb. 2006. 

2 "Market Transformation" was formerly referred to as 

"Technology Acceptance" in DOE documents and 

events leading up to the issuance of this Funding 

Opportunity Announcement. The two terms are 

synonymous for purposes of this FOA. 

or remove barriers to solar technology 

commercialization as quickly and efficiently as 

possible. 

• SAI MT is looking for significant market changing 

activities. Given the 2015 goal, DOE is seeking to 

make large and significant changes in the 

marketplace through its MT activities. 

• SAI MT is focused on near- and mid-term results. 

Emphasis is on projects and activities with the 

greatest potential to assist DOE in reaching its SAI 

cost-competitiveness goal by 2015. 

• SAI MT is looking for performers and partners 

who are committed to the SAI mission. DOE is 

inclined to partner with motivated entities that will 

also benefit from achievement of the SAI mission. 

2. Technical Approach 

To reach the targeted Stakeholders in State 

Government and Utility Companies, SAI awarded 

cooperative agreements to four organizations that 

have expertise in working with these entities. 

•	 The Solar Electric Power Association (SEPA) 

has extensive experience working with Utility 

Partners and was chosen to lead the outreach 

efforts in this area. 

•	 The Clean Energy Group (CEG), National 

Association of Regulatory Utility 

Commissioners (NARUC), and National 

Council of State Legislatures (NCSL) were 

chosen to perform outreach to the States. 

These organizations have a broad membership 

network that has effectively done outreach to the 

targeted stakeholders in the United States. 

Clean Energy Group, Inc. (CEG) 

Cost of Total Award (FY07-FY09): $345,000 

Using education, research and information 

services, CEG’s project will: (1) provide 

information and technical assistance to state 

leaders and state renewable energy programs in 

the development of effective solar programs; (2) 

identify and foster solar program best practices; 

and (3) identify and promote strategic 

opportunities for states and DOE to advance solar 

technology deployment through partnerships, 

collaboration, and targeted activities. 

National Conference of State Legislatures 

(NCSL) 

Cost of Total Award (FY07-FY09): $263,672 

NCSL’s Solar Energy Project will provide outreach 

to state policymakers on solar technology and 

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policy options that can assist in integrating solar 

energy into the fuel mix while breaking down 

market barriers to the adoption of solar energy 

technology. The project will communicate the 

economic, energy security, and fuel diversity 

benefits of solar energy technology. 

National Association of Regulatory Utility 

Commissioners (NARUC) 

Cost of Total Award (FY07-FY09): $303,004 

NARUC project goals are to: (1) provide key state 

agencies, like Commissions and Energy Offices, 

with resources to help solar technologies 

overcome regulatory and market barriers; and (2) 

take advantage of emerging opportunities to 

encourage greater deployment and penetration of 

solar technologies into society. The project 

implementation will include outreach and 

education, regulatory and technical best practices, 

renewable portfolio standards and market 

structures, and other activities to encourage solar 

technologies. 

Solar Electric Power Association (SEPA) 

Cost of Total Award (FY07-FY09): $1,597,092 

The overall goal of SEPA’s project is to address 

utilities’ unique roles in the increased adoption of 

solar electric technology, both through utilityowned systems and utility programs that facilitate 

customers’ use and ownership. The project seeks 

to stimulate the increased utility adoption and 

integration of solar technologies, on either side of 

the meter, by providing a variety of support 

services and information to utilities throughout the 

United States. 

3. Results and Accomplishments 

Solar State Legislation Database 

NCSL Solar State Legislation 

(www.ncsl.org/programs/energy/energypolicy.cfm) 

was created to provide a readily accessible 

database of current and previous years' bills on 

energy issues. The database is searchable by 

energy topic and by state. 

Solar Energy Institute 

The Solar Energy Institute conference took place 

in Washington, DC, on October 18-19, 2007. 

Fifteen legislators and legislative staff attended the 

two-day conference and participated in the solar 

homes tour at the Solar Decathlon on the Mall. 

Response was overwhelmingly positive, and after 

attending the meeting, at least two of the 

attendees proceeded to introduce or consider 

legislation related to solar energy. 

States Advancing Solar 

CEG launched www.statesadvancingsolar.org to 

serve as a resource for state policy makers and 

decision makers interested in developing a solar 

program. 

Technology and Policy Reference Guide
 

NARUC released the "Solar Energy Technology 

and Policy Reference Guide" 

(www.naruc.org/programs.cfm?c=Domestic) which
 

includes information on Solar regulatory policies, 

technologies, and state and industry perspectives. 

Peer Matching Online Tool 

SEPA released “The Peer Matching Online Tool” 

(http://www.solarelectricpower.org/peer/), a 

service to share information and best practices to 

help all utilities improve their solar programs. The 

database is searchable by location, utility type, 

experience or by solar program type. 

4. Planned FY 2008 Activities 

•	 Developing and disseminating a “Utility Solar 

Toolkit” to nearly all utilities in the US. 

•	 Performing a State Solar PV Program Survey 

•	 Performing state policymaker education and 

outreach. 

•	 Performing solar market research and public 

education. 

•	 Conducting Renewable Portfolio Standard 

(RPS) Implementation Collaborative. 

•	 Hosting workshops at NARUC’s 2008 Annual 

Convention in Anaheim and 2008 Winter 

Committee Meetings in Washington. 

•	 Creating a LegisBrief, two-page summaries on 

important issues of the day for state 

legislatures, on solar technology and state 

policy activities. 

•	 Conducting a seminar with area experts, 

targeted toward state legislators and 

legislative staff. 

5. Major FY 2007 Publications 

M. Taylor, “Utilities Engage Solar Electricity,” 

Association of Energy Engineers, Alternative & 

Renewable Energy Development Institute News, 

Fall 2007 Newsletter. 

M. Taylor, ”Utility Solar Evolution,” Renewable 

Energy Access, Solar Power 2007, September 26, 

2007. 

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6. Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2007 

($K) 

Cost Share 

($K) 

National Conference of 

State Legislatures 

(NCSL) 

7700 East First Place 

Denver, CO 

303-364-7700 

glen.andersen@ncsl.org 

State Legislative outreach on 

Solar Technology and Policy 

Options 

247,500 122,000 

Clean Energy Group, Inc. 

(CEG) 

Clean Energy States 

Alliance, Inc. (CESA) 

50 State Street, Suite 1 

Montpelier, VT 

802-223-2554 ext. 203 

maria@cleanegroup.org 

Solar State Partnership 

Project 247,500 122,000 

National Association of 

Regulatory Utility 

Commissioners (NARUC) 

NASEO 

1101 Vermont Ave., Suite 200 

Washington, DC 

202-898-2204 

aparraway@naruc.org 

Solar America Initiative State 

Working Group 203,004 100,00 

Solar Electric Power 

Association (SEPA) 

John Nimmons & 

Associates, Inc. Madison 

Energy Consultants 

Energy Matters 

Sonenthal and Overall 

1341 Connecticut Ave. NW, 

Suite 3.2 

Washington, DC 

202-857-0898 ext. 1 

mkimble@solarelectricpower.org 

Facilitating Utility Use and 

Integration of Solar Electric 

Power 

614,780 982,312 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

Technical Outreach 

Market Transformation Support Activities
 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Cécile Warner (NREL), 303-384-6516, cecile_warner@nrel.gov 

DOE HQ Technology Manager: Charlie Hemmeline, 202-586-6646, charlie.hemmeline@hq.doe.gov 

FY 2007 Budgets: $145K (NREL), $50K (BCS) 

Objectives 

•	 Coordinate the technical assistance support across all market transformation activities to 

capitalize on synergistic opportunities and efficiently apply resources and expertise across a 

range of projects. 

•	 Identify and develop analytical tools and assistance products such as targeted training, which can 

be used by multiple tiger teams in their efforts to support Solar America Cities, Showcases, and 

Government Solar Installation Program (GSIP) projects. 

Accomplishments 

•	 These efforts are largely targeted for fiscal year (FY) 2008 and beyond. The work is intended to 

be in full swing when the memorandum-of-agreement (MOA) documents for each market 

transformation project have been executed, and the projects are officially launched. 

•	 We coordinated across and among tiger teams at each of the four participating institutions that 

are leading the technical support to identify opportunities for capacity building among the projects’ 

participants. 

Future Directions 

•	 Develop and convene a series of interactive seminars on financing of solar systems within 

municipalities, including a Clean Renewable Energy Bonds (CREB) Seminar, for Solar America 

City representatives. 

•	 Coordinate technical assistance efforts among all participating institutions and identify and 

produce user-friendly tools and products to accelerate solar market penetration in Solar America 

cities, Showcases and within the GSIP federal government projects. 

1. Introduction 

Market barriers increase the price of solar 

systems and the time to commercialization. The 

Technical Partnerships and Demonstrations 

activity reduces barriers to the 

commercialization of solar energy technologies 

and promotes market expansion. Through this 

activity, we will accelerate Solar America City 

(SAC), Solar America Showcase, and GSIP 

government photovoltaic (PV) deployment by 

efficiently providing technical and analytical 

support to participating PV developers, cities, 

and government entities. 

2. Technical Approach 

There are three Technical Partnerships and 

Demonstration agreements: Solar America 

Showcases, Solar America Cities, and GSIP. At 

the direction of DOE, so-called “Tiger teams” for 

technical and analytical support of showcase PV 

installations are formed to support these 

requests. Tiger team personnel from several 

institutions, including NREL, provide projectspecific technical support that covers the gamut 

of large project development and installation 

activities, as well as coordination among diverse 

stakeholder groups and education and outreach 

activities. Specifically, the technical assistance 

contribution to Showcase projects, SAC 

partnerships, and GSIP partnerships will focus 

on technical aspects of project implementation. 

The Market Transformation support activities 

focus on the coordination and streamlining of 

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178
 

 

these technical assistance efforts to identify and 

capitalize on synergies and to ensure efficient 

project implementation. 

Agreement Title FY 2007 

Budget ($K) 

Market Transformation Support 145 K 

3. Results and Accomplishments 

•	 Because the project memorandums of 

agreements (MOAs) with the participating 

institutions (SAC, Showcases, and GSIPs), 

were not fully executed during fiscal year 

(FY) 2007, this project’s accomplishments 

are limited. 

•	 This work is intended to be in “full swing” 

when the MOA documents for each market 

transformation project have been executed 

and the projects are officially launched. 

Hence, this task’s effort is largely targeted 

for FY 2008. 

•	 We coordinated across and among tiger 

teams at each of the four participating 

institutions that are leading the technical 

support to identify opportunities for capacitybuilding among the projects’ participants. 

4. Planned FY 2008 Activities 

•	 Develop performance specifications and 

support to solicitations related to 

implementation of PV and renewable energy 

projects, including review of quotes and 

bids, conducting acceptance tests, and 

ensuring appropriate user and other 

stakeholder training for long-term project 

sustainability. 

•	 Develop and apply performance models to 

predict and validate performance of planned 

and installed systems. Produce user-friendly 

tools and products to accelerate solar 

market penetration in Solar America cities, 

Showcases and within the GSIP federal 

government projects. 

•	 Develop success stories and best practices 

guides for the technical implementation of 

projects in all relevant market sectors, and 

conducting outreach activities to increase 

understanding of new and existing 

stakeholder partners. 

•	 Coordinate across and among tiger teams at 

each of the four participating institutions that 

are leading the technical support to identify 

opportunities for capacity-building among 

each of the projects’ participants and identify 

•	 Develop and convene a series of interactive 

seminars on financing of solar systems 

within municipalities, including a CREB 

Seminar, for interested SAC 

representatives. 

5. Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description FY 2007 

($K) 

Cost Share 

($K) 

BCS, Inc. 

Suzie Lemieux 

Laurel, MD 

slemieux@bcs-hq.com 

• Coordinated logistics for FY07 

Annual Review. 

• Provided participants with the 

opportunity to review and 

comment on SETP’s 

technology roadmaps and to 

confirm the roadmaps’ utility 

in helping formulate SETP’s 

FY08 Annual Operating Plan. 

$50K 

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180
Solar Thermal R&D Subprogram Overview 

Frank (Tex) Wilkins, Team Leader, Solar Thermal R&D 

Fiscal year (FY) 2007 was a momentous one for the Solar Thermal Subprogram. The Office of 

Energy Efficiency and Renewable Energy (EERE) conducted a reorganization that had a 

significant impact on the Subprogram, and the Concentrating Solar Power (CSP) program saw a 

resurgence. 

The Solar Heating and Lighting (SHL) activity was transferred from the Solar Program to EERE’s 

Building Technologies Program, where it will become an important part of their development of 

zero energy buildings. Bob Hassett, who has a long history with SHL, manages the activity in the 

Building Technologies Program. 

In June, the sun was shining on a new CSP project when Nevada Solar OneTM began operation. 

This 64-megawatt (MW) trough plant, located in Boulder City, Nevada, is the first commercial 

CSP plant built in the United States since 1991. Nevada Solar One shows the resurgence of CSP 

as a major option for generating carbon-free renewable energy. Another sign of CSP’s 

resurgence during 2007 was the planning of other large CSP projects. 

Recognizing the value of CSP, utilities announced planned projects that totaled more than 3,000 

MW. These included dishes, troughs, and towers. However, Spain was the hotbed of CSP activity 

during 2007. A 10-MW tower became operational and construction begun on a 20-MW tower. At 

least four 50-MW trough projects were also under construction in Spain by the end of the year. 

Results and Accomplishments 

The CSP budget got a boost in FY 2007 which enabled a competitive solicitation for the first time 

in several years. The solicitation, released through the Golden Field Office, was focused on three 

areas: (1) thermal storage, (2) trough component manufacturing, and (3) advanced CSP systems 

and components. The objective of the solicitation is to establish cooperative research and 

development (R&D) contracts that will help the Solar Program achieve its CSP cost goal of 7-10 

cents/kWh by 2015. A total of 12 proposals from nine companies were selected for negotiation. 

The selected proposals included work on troughs, dishes, and towers and will begin in FY 2008. 

As the subprogram gears up, work continues at Sandia National Laboratories and National 

Renewable Energy Laboratory to help industry improve their technology. This is becoming more 

difficult because the industry is rapidly expanding, and new concepts are being touted as having 

the potential for low-cost power. The increased budget is enabling an increase in lab staff to 

handle the increased work load. 

New Directions 

The increased budget also provided the impetus to take a long term view of CSP R&D. This 

exercise led to a scenario that would establish a new goal for CSP: providing baseload power at a 

competitive cost by 2020. To provide baseload power, CSP projects would require 12-17 hours of 

storage at low cost. As the country looks for methods of combating climate change, CSP could 

prove to be an attractive option to coal for providing baseload power. To reach this goal, an 

expanded R&D program with a new emphasis on thermal storage would be required. Planning for 

an increased effort on thermal storage began with the intent of implementing it in FY 2008. 

FY 2007 was a momentous year, yet FY 2008 promises to be even more exciting. 

181 Solar Thermal R&D
Solar Thermal R&D 182
Concentrating Solar Power 

Concentrating solar power (CSP) systems use the heat generated by concentrating and 

absorbing the sun's energy to drive a conventional turbine or heat engine/generator and produce 

electric power. Three types of CSP systems—trough, dish/engine, and power tower—are all 

capable of producing power using the sun's energy. 

Trough systems, the most commercially mature of the three systems, use linear parabolic 

concentrators to focus sunlight along the focal lines of the collectors. Dish/engine systems 

comprise a parabolic dish concentrator, thermal receiver, and heat engine/generator located at 

the focus of the dish to generate power. In a variation of the dish/engine system, concentrating 

photovoltaics (CPV), an array of high-efficiency photovoltaic cells replaces the thermal receiver 

and heat engine. In a power tower system, a field of two-axis tracking mirrors, called heliostats, 

reflects the solar energy onto a receiver that is mounted on top of a centrally located tower. 

With the advent of renewables-friendly policies within the United States and abroad, there is a 

renewed interest in CSP technologies based on their potential for low cost and ease of largescale implementation. The Western Governors’ Association (WGA) established a Solar Task 

Force to determine the potential of solar energy in the West and identify the incentives required to 

establish projects. The National Renewable Energy Laboratory (NREL) provided much of the 

analysis required by the WGA. In the U.S. southwestern states, CSP projects are under way in 

Nevada and Arizona; New Mexico and California are investigating the possibilities of developing 

CSP plants. R&D priorities of the CSP Subprogram are determined, in part, by projects being 

developed under the state programs. 

The accomplishments of the DOE Solar Program’s CSP activity for FY 2007 include: 

CSP Applied Research 

•	 Performed durability testing and published results of optical materials that potentially can 

reduce the cost of levelized cost of energy of CSP to less than 10 cents/kWh by 2015. 

CSP Technology Acceptance 

• Continued development of the Concentrating Solar Deployment System (CSDS) model. 

CSP Testing and Evaluation 

•	 Included CSP parabolic trough modeling within Solar Advisor Model. 

Dish Engine Development 

•	 Operated and improved the Stirling Energy Systems six-dish model power plant, 

cataloging more than 100 development areas. 

•	 Installed Infinia 3-kilowatt system at SNL. 

Parabolic Trough Development 

•	 Developed a new selective coating to meet the long-term selective property goals for 

parabolic trough receivers. 

•	 Refined its theoretical overlay photographic alignment system for evaluating the 

alignment of mirrors and receivers on parabolic trough collectors installed in a solar field. 

•	 Improved the speed of infrared imaging of receivers for assessing the thermal 

performance of receivers in the solar field. More than 30,000 receivers were imaged at 

the Solar Energy Generating Systems fields to help FPL Energy categorize receiver 

performance in advance of a major receiver upgrade program. 

183

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Concentrating Solar Power
 

 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

CSP Applied Research 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Cheryl Kennedy (NREL), 303-384-6272, cheryl_kennedy@nrel.gov 

DOE HQ Technology Manager: Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2007 Budgets: $135K 

Objectives 

•	 Develop technology that dramatically reduces the cost of concentrating solar power (CSP) to less 

than 10 cents/kWh by 2015. 

•	 For mirrors, this is accomplished through technology advances that reduce the cost of the mirrors 

by half by moving from heavy glass mirrors to lightweight front-surface reflectors that include 

surface coatings to reduce soiling. 

•	 Develop advanced reflector materials that are low in cost (less that $1/ft2

 or $10.76/m2) and 

maintain high specular reflectance (90%–95% into a 4-mrad cone angle) for long lifetimes (10 to 

30 years) under severe outdoor environments. 

•	 Test the durability of optical materials to determine lifetime of solar reflector materials. 

Accomplishments 

•	 Performed durability testing and published results of optical materials that potentially can reduce 

the cost of levelized cost of energy (LCOE) of CSP to less than 10 cents/kWh by 2015. 

•	 Provided significant industry support to the CSP and concentrating photovoltaic (CPV) industries 

on solar reflectors. 

Future Directions 

•	 Continue durability testing of optical materials to determine lifetime of solar reflector materials. 

•	 Optical characterization of advanced reflector materials, accelerated and outdoor testing of 

commercial, experimental, CSP FOA, CSP industry, and CRADA supplied reflector materials to 

determine lifetime of solar reflector materials, and support of industry/program needs. 

•	 Analyze and publish testing results of reflector materials applied to CSP technologies. 

1. Introduction 

Commercialization of concentrating solar power 

(CSP) technologies requires the development of 

advanced reflector materials that are low in cost 

and maintain high specular reflectance for 

lifetimes of 10 to 30 years under severe outdoor 

environments. The DOE Solar Program Multi-Year 

Technical Plan targets cost reductions of up to 

50% for the solar concentrator. These goals 

should be achieved through technology advances 

such as lightweight front-surface reflectors that 

include anti-soiling coatings. The objective of this 

research is to identify new, cost-effective 

advanced reflector materials that are durable with 

weathering. 

2. Technical Approach 

Candidate reflector materials were identified 

based on their potential for low cost and high 

optical performance and durability. All candidate 

materials were optically characterized prior to 

exposure testing and as a function of exposure 

time to assess optical durability. The 

hemispherical reflectance of the samples was 

measured from 250 to 2500 nm using a PerkinElmer Lambda 9 or 900 UV-VIS-NIR 

spectrophotometer with a 60-mm, integratingsphere attachment relative to National Institute of 

Science and technology (NIST) standards. The 

direct normal air-mass 1.5 (DIRNOR15) solarweighted hemispherical reflectance is calculated 

from data collected in the 250-2500-nm range. 

The specular reflectance is measured at 7- and 

25-mrad cone angle with a Device and Services 

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184
 

 

 

 

(D&S) Field Portable Specular Reflectometer at 

660 nm. 

The mirrors are subjected to accelerated or 

outdoor weathering at a variety of geographically 

diverse exposure sites. Outdoor exposure testing 

is performed in Golden, Colorado (NREL); Miami, 

Florida (FLA); and Phoenix, Arizona (AZ). 

Accelerated exposure testing can be performed at 

NREL in the Atlas Ci65A (Ci65) or Ci5000 

(Ci5000) Weather-Ometers (WOM), and a BlueM 

damp heat oven (BlueM). The WOM’s, and BlueM 

allow control of exposure temperature and 

ambient humidity. The WOM's use xenon-arc light 

source with filters designed to closely match the 

terrestrial air-mass 1.5 solar spectrum. The 

WOM’s operates continuously at 60°C and 60% 

relative humidity (RH), with light levels about equal 

to outdoor exposure for the Ci65 and twice 

outdoor exposure for the Ci5000. A single day of 

testing (24 hours) is roughly equivalent to three 

times the outdoor exposure for the Ci65 and six 

times for the Ci5000 in terms of light intensity. 

The BlueM operates continuously at 80°C and 

80% RH, but the samples are not exposed to the 

light. The BlueM does not have the same 

measured acceleration factor as the WOMs, but 

from other experiments it is believed the 

acceleration factor is roughly 5 times the Ci5000. 

3. Results and Accomplishments 

•	 Paper on durability of thin-glass mirrors 

applied to CSP technologies (03/31/07) 

•	 Paper on status of reflector materials. 

(07/31/07) 

•	 Provided significant industry support about 

cleaning and quality control, and the lead-free 

paints were developed for interior applications. 

Consequentially, the basic mirror composition of 

commercially available mirrors is radically different 

from historically durable solar mirrors, and 

alternatives have been limited. 

Trough mirrors, used in commercial solar plants, 

manufactured by Flabeg have historically been 

very durable. They use silvered thick, slumped 

low-iron glass that is protected with a heavily 

leaded proprietary multilayer paint system 

designed for outdoor exposure. Flabeg converted 

their mirror line to 4- or 5-mm glass and a new 

low-lead paint system in 2003, in which the lead 

was reduced to the point that durability was 

expected to be equivalent. The base paint of the 

three-layer paint system now contains 2.5% lead 

and the intermediate paint contains 1% lead, 

where the lead content was reduced from ~20% 

and ~10% respectively. The white top coat with 

high UV stability remained the acrylic based top 

coat that was used in the past. Side-by-side 

exposure testing of the original and new 

construction began in 2005. The original mirrors 

with the high-lead paint system exhibit better 

optical durability than the new reduced-lead 

mirrors (see Fig. 1). The high-lead mirrors 

degraded 0.9% and the reduced-lead degraded 

1.9% after 18 months of outdoor exposure in 

Colorado (NREL). Whereas, the high-lead mirrors 

degraded 2.1% and the reduced-lead degraded 

3.6% after 24 months of accelerated exposure in a 

Ci65a Weather-Ometer (WOM). 

 Equivalent NREL Exposure Time 

0 1 2 3 4 5 6 100 

reflectors to CSP and concentrating 

photovoltaic (CPV) industry. 

3.1 Glass Mirrors 

Traditionally, glass mirrors have excellent 

durability, are readily available, have the 

confidence of the solar manufacturing industry, 

and have been commercially deployed. However, 

for parabolic shapes glass needs to be slumped 

% Hemispherical Reflectance 95 

90 

85 

SWV - Old - Ci65 

SWV - New - Ci65 

SWV - Old - NREL 

SWV - New - NREL

which is expensive. Glass mirrors are heavy and 

require more robust support, footings and tracking 

hardware. If the mirrors break under wind loads, 

they tend to break adjacent mirrors and receivers. 

Two significant changes occurred in the classical 

wet-chemistry process used in mirror 

manufacturing because of environmental 

concerns. The first is the use of a copper-free 

back layer, and the second is the use of lead-free 

paints. The copper-free process requires stringent 

80 

0.0 3.3 6.7 10.0 13.3 16.7 20.0 

Total UV Dose (100 x MJ/m2) 

Fig. 1. Loss of solar-weighted reflectance of 

original high-Pb and new low-Pb Flabeg thickglass mirrors as function of accelerated WOM and 

outdoor exposure at Golden, CO (NREL), in total 

UV dosage. 

Pilkington (4-mm copper-free) mirrors and 

“Spanish” (Cristaleria Espanola S.A; i.e., Saint 

Gobain) glass mirrors (3 mm, copper-free, and 

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lead-free paint), bonded to steel with four different 

candidate adhesives, were tested for possible use 

at Solar Tres. Up to this point, neither Pilkington 

nor Spanish mirrors exposed outdoors at NREL for 

82 months show degradation; but the Pilkington 

mirrors exhibit better optical durability than the 

Spanish mirrors in accelerated WOM exposure 

testing (see Fig. 2). Spanish mirrors degraded 

19.0%, whereas Pilkington mirrors degraded 2.8% 

after 53 months of accelerated WOM exposure 

and adhesive-related degradation is more 

prevalent with Spanish glass mirrors. Depending 

on the adhesive used to bond the mirror, Spanish 

mirrors degraded 4.7% to 12.0%, whereas 

Pilkington mirrors degraded 1.7% to 2.9% after 50 

months of accelerated WOM exposure. 

 Equivalent NREL Exposure Time (years) 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 100 

95 

were from an experienced copper-free production 

run that included 0.15% Pb in the two-coat paint 

system, and the Naugatuck mirrors were poor 

quality mirrors from an inexperienced pilot run that 

incorporated <5 ppm Pb in a 1-coat paint system. 

For the copper-free constructions, adding epoxy 

and polyurethane back protection appears to be a 

poor choice because when these constructions 

failed, they typically failed catastrophically by 

silver/paint delamination. The epoxy 

adhesive/substrate show slight advantages over 

other adhesive/substrates. Edge protection and 

substrate and glass back-cleaning had no effect. 

CPV manufacturers have expressed significant 

concern regarding the durability of thin-glass 

mirrors made with copper-free and lead-free paint 

systems. Naugatuck Glass responded to the 

mirror degradation issue and provided copper-free 

mirror samples for testing with a two-coat, leadNREL - Pilkington 

NREL - Spanish 

Ci65 - Pilkington 

Ci65 - Spanish

free paint system plus moisture and adhesive­ 90 resistant back protection, instead of the one-coat 

paint system previously used in its manufacturing 

line. Exposure testing results appear encouraging 

85 

80 and testing is ongoing (see Fig. 3). 

% Hemispherical Reflectance

75 

100 

Single surviving 

sample f

initial 

rom 3 

GreyCoat 

GreyCoat/966Adh/Al 

ClearCoat 

ClearCoat/966Adh/Al 

70 

65 

0.0 3.3 6.7 10.0 13.3 16.7 20.0 23.3 26.6 30.0 33.3 36.6 40.0 43.3 46.6 50.0 53.3 

Total UV Dose (100 x MJ/m2) 

% Hemispherical Reflectance80 

Fig. 2. Loss of solar-weighted reflectance of thick 60 

40 

20 

Pilkington and Spanish reflectors with copper-free 

back layer, Pb-free paint, as a function of Ci65a 

WOM exposure and outdoor exposure at NREL. 

Thin-glass mirrors also use traditional wet-silvered 

processes on thin (<1 mm), relatively lightweight 

glass. The choice of adhesive has been observed 

to affect the performance of weathered thin-glass 

mirrors, and corrosion has been observed in 

deployed mirrors, including mirrors using the new 

copper-free protective layer and lead-free paints. 

In addition, some thin-glass silvered copper-free, 

lead-free mirrors sold for outdoor applications 

have not passed the minimum ASTM standards 

(i.e., 120-h CASS, 480-h salt spray, and damp 

heat) to qualify for indoor applications. 

A matrix of sample constructions prepared to 

identify the most promising combinations of paints 

and adhesives for use with solar reflectors has 

more than 3 years of exposure in the Ci5000 and 

in BlueM. The AGC (formerly Glaverbel -

Belgium) mirrors tended to outperform the 

Naugatuck mirrors (U.S.) in the mirror matrix 

experiment. However, at the time the mirrors 

were acquired, the Glaverbel mirrors provided 

0 

0 3 6 9 12 15 18 21 24 

Exposure Time (Months) 

Fig. 3. Loss of solar-weighted reflectance of 

Naugatuck thin-glass mirrors with Cu-free back 

layer and 2-layer Pb-free paint system with and 

without moisture barrier clear coat and laminated 

substrate as a function of accelerated BlueM 

exposure. 

Although glass mirrors with copper back layers 

and heavily leaded paints have been considered 

robust for outdoor use, the new copper-free, back 

layer and lead-free paint systems were designed 

for interior mirror applications and their outdoor 

durability must be determined. 

3.2 Aluminized Mirrors 

Aluminized reflectors use a polished aluminum 

substrate, an enhanced aluminum reflective layer, 

and a protective oxidized topcoat. These mirrors 

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40 

50 

60 

70 

80 

have shown poor durability in urban and 

industrialized (polluted) locations. The 

hemispherical reflectance and 25 mrad specularity 

had improved durability with protective polymeric 

overcoat incorporated onto the aluminized 

aluminum. However, the specularity degraded with 

outdoor exposure at Arizona, Florida, and 

Colorado (NREL) and with accelerated exposure 

in the Ci65a WOM. Alanod stopped selling this 

material in 2004 for outdoor use because of 

problems associated with the delamination of the 

overcoat. Alanod worked to improve the reflector 

durability and its in-house testing capability. The 

fluoropolymer overcoat was replaced with a 

nanocomposite oxide protective layer. New 

samples received in 2005 are undergoing testing. 

Preliminary exposure testing results appear 

encouraging and testing is ongoing (see Fig. 4). 

Alanod reintroduced the product for sale as MiroSun in 2006. The material is commercially 

available from Alanod in Germany for ≈$2.50/ft2

. 

The initial solar-weighted hemispherical 

reflectance is ≈91.8%; initial specular reflectance 

at 25 mrads is ≈83.7% and at 7 mrads is ≈63.9%. 

Alanod is now working to develop a silvered solar 

reflector likely to be called Miro-Silver. 

100 

90 

after the equivalent of 10 years of accelerated 

outdoor exposure in ACUVEX (natural sunlight in 

Phoenix, AZ, concentrated seven to eight times 

with a Fresnel-reflector while samples are cooled 

with a fan to near-ambient conditions and sprayed 

with deionized water 8 minutes per natural sun 

hour). However, Ci65a WOM results showed 

significant reflectance loss earlier than anticipated 

from the proof-of-concept materials. Prototype 

materials to test modifications to the baseline 

construction were produced under a subcontract. 

These tests were successful in identifying changes 

to the baseline construction that dramatically 

improved the Ci65a WOM durability of the 

reflective film. Some of these improvements were 

then incorporated into a new pilot plant production 

run delivered late 2004. Initial hemispherical and 

specular reflectivity was low due to a vacuum 

problem when the silver was sputtered process. 

In ReflecTech’s third pilot-plant run additional 

improvements from the subcontract were 

incorporated. Samples (ReflecTech [06-48, 06­

60]) delivered in 2006 had improved hemispherical 

and specular reflectivity. Both versions of the third 

pilot-run materials show minimal loss in solarweighted and 25-mrad and 7-mrad specular 

reflectance after 16 months of real-time outdoor 

exposure in Golden, CO. The 06-60 shows 

minimal loss in solar-weighted and 25-mrad and 7­

mrad specular reflectance, but the 06-48 shows 

30 

NREL - 25 mr 

NREL - 7 mr 

NREL - SWV 

APS - 25 mr 

APS - 7 mr 

APS - SWV 

FLA - 25 mr 

FLA - 7 mr 

FLA - SWV 

WOM - 25 mr 

WOM - 7 mr 

WOM - SWV 

Blue M - 25 mr 

BlueM - 7 mr 

BlueM - SWV 

Sandia -25mr 

0 3 6 9 12 15 18 21 24 27 30 33 36 

12-20% loss after 6 months of accelerated Ci65a 

% Specular Reflectance 

60 

70 

80 

90 

% Reflectance 

25-mr - NREL - (06-48) 

7-mr - NREL - (06-48) 

SWV NREL (06-48) 

25-mr - WOM - (06-48) 

7-mr - WOM - (06-48) 

SWV WOM (06-48) 

25-mr - NREL - (06-60) 

7-mr - NREL - (06-60) 

SWV NREL (06-60) 

WOM exposure (see Fig. 5). Durability testing is 

ongoing and the material is being field-tested. 

Equivalent NREL Exposure Time (years) 

0 1 2 3 100 

Exposure Time (Months) 

Fig. 4. Loss of solar-weighted reflectance, 25- 

and 7-mradian specular reflectance at 660 nm of 

Alanod Miro-Sun aluminized reflectors as a 25-mr - WOM - (06-60) function of APS, NREL, and Sandia outdoor 7-mr - WOM - (06-60) 

SWV WOM (06-60) exposure and accelerated WOM and BlueM 50

exposure. 40 

3.3 Silvered Polymer Reflectors 

A polymeric solar reflector was developed through 

collaborative research with ReflecTech. In 2001, a 

small pilot run demonstrated that production could 

be achieved using standard commercial film 

converter equipment. This initial pilot-run material 

shows minimal loss in solar-weighted reflectance 

after 5 years of real-time outdoor exposure in 

Golden, CO. In addition, there was no significant 

loss in solar-weighted reflectance for samples 

0.0 3.3 6.7 10.0 

Total UV Dose (100 x MJ/m2) 

Fig. 5. Loss of solar-weighted and 25-mrad and 

7-mrad specular reflectance of ReflecTech third 

pilot run as a function of outdoor exposure in 

Colorado and accelerated Ci65a WOM exposure. 

Progress has been made on advanced solar 

reflector research and durability testing of 

reflectors supplied by industry is ongoing. Glass, 

ReflecTech, and Alanod mirrors are commercially 

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available and, based on accelerated exposure 

testing, should meet the 10-year lifetime goals. 

However, predicting an outdoor lifetime based on 

accelerated exposure testing is risky because the 

accelerated failure mechanisms must exactly 

replicate those observed outdoors. The 

construction of solar reflectors has significantly 

changed. Because of this, all of the solar reflectors 

commercially available have been in outdoor realtime exposure testing for less than 3 years. 

4. Planned FY 2008 Activities 

The most significant activities planned (as part of 

the FY 2008 AOP) are: 

•	 Complete installation of new accelerated 

exposure chambers to test durability of 

commercial and experimental solar mirrors. 

(3/08). 

•	 Determine optical performance, lifetimes, and 

cost goals for advanced reflectors that are 

consistent with current CSP program 

objectives. (6/08). 

•	 Compare the durability of silvered thin-glass 

copper-free and lead-free mirrors after 

exposure to AET (Ci5000 WeatherOmeter and 

damp-heat at different humidity conditions) 

and OET (Golden, CO; Phoenix, AZ; Miami, 

FL; and Alice Springs, Australia) (6/08) 

•	 Provide status of test results of candidate 

solar mirror samples and identify promising 

candidates and how advanced solar mirrors 

will help meet the cost goal for electricity. 

(09/08). 

5. Major FY 2007 Publications 

M. Kempe, G. Jorgensen, K. Terwilliger, T. 

McMahon, C. Kennedy, and T. Borek, “Acetic Acid 

Production and Glass Transition Concerns with 

Ethylene-Vinyl Acetate Used in Photovoltaic 

Devices” Sol. Energ. Mater. Sol. Cell 91, 315 

(2007). 

C. Kennedy, “Durability of Front Surface Solar 

Reflectors,” 2007 TechCon Proceedings of Society 

of Vacuum Coaters, April 28-May 3, Louisville, KY, 

2007. 

C. Kennedy, K. Terwilliger, and G. Jorgensen, 

“Further Analysis Of Accelerated Exposure 

Testing Of Thin-Glass Mirror Matrix,” Proceedings 

of Energy Sustainability 2007, June 27-30, Long 

Beach, CA, 2007. 

C. Kennedy and K. Terwilliger, “Solar 2007: 

Optical Durability of Candidate Solar Reflectors for 

Concentrating Solar Power,” Proceedings of Solar 

2007, July 7-12, Cleveland, OH, 2007. 

C. Kennedy, “Advances in Concentrating Solar 

Power Collectors: Mirrors and Solar-Selective 

Coatings,” Proceedings of Association of Industrial 

Metallizers, Coaters and Laminators (AIMCAL) 

Fall Technical Conference 2007 and 21st 

International Vacuum Web Coating Conference, 

October 8-10, Scottsdale, AZ, 2007. 

6. University and Industry Partners 

Significant industry interaction occurred with CSP 

reflector manufacturers and CPV manufacturers 

on the durability of solar mirrors. A partial list 

includes: 3M, A Better Focus, Acciona, AGC 

(Glaverbel), Alanod, Alcoa, Applied Image, 

Boeing, Cool Earth, Cooper Lighting, Corning, 

Cosmo Films, Dow Chemical, Dow Corning, 

Emcore, eSolar, Flabeg, Gardner, GreenVolts, 

Guardian, Honeywell, Infinia, JX Crystals, Luz II, 

Nambia Power Tower project, Naugatuck, Nitinol, 

Northside, ORNL, PARC, Pilkington, PPG, Pratt & 

Whitney, Praxair, RAflector, Raytheon, 

ReflecTech, Replex, Rio Glass, Rocky 

development, SAIC, Saint Gobain, Sandia, 

Sandvik, Schott, Solel, SolFocus, Soliant, Solucar, 

Solyndra, Southwall, Stirling Energy Systems, 

Sunray, SunTechnics, Symmorphix, United Solar, 

University of Baleric Islands, University of 

California Merced, University of Colorado, 

University of Hartford, University of Minnesota, 

Von Ardenne, West Virginia University, and Wooly 

Parsons. 

Cooperative Research and Development 

Agreement’s were negotiated with SolFocus and 

Solar Systems to determine the reliability and 

durability of large and small mirror dishes; front 

surface reflectors, adhesive and encapsulents, 

and III-V cells; and will help to establish the 

viability of producing low cost, high performance 

photovoltaic energy conversion modules by 

collector based CPV. 

The following organizations partnered in the 

project’s research activities during FY 2007. 

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Organization/ 

Principal 

Investigator 

Location/e-mail Description/Title of Research 

Activity 

FY 2007 

($K) 

Cost Share 

($K) 

Solar Systems 

Ken Cheah 

Melbourne, Australia 

Kcheah@solarsystems.com.au 

Research on durability of small 

mirror dishes and front surface 

reflectors, and bond joints. 

8.4* 30.3** 

SolFocus 

Mark Spencer 

Mountain View, CA 

mark_spencer@solfocus.com 

Research on optical durability of 

thin-glass mirror panels. 13.0† 234.0‡ 

*NREL Funded Amount: $8.4k 6/26/07 - 9/30/07 

** Sponsor Contract Value $39.3k 6/6/07 - 1/25/08 

† NREL Funded Amount: $13.0k 6/15/07 - 9/30/07 

‡ Sponsor Contract Value $234.0k 6/15/07 through 8/14/11 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

 

CSP Laboratory Facilities 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Key Technical Contacts: 

DOE HQ Technology Manager: 

FY 2007 Budgets: 

Sandia National Laboratories (SNL) 

Mark Mehos (NREL), 303-384-7458, mark_mehos@nrel.gov 

Tom Mancini (SNL), 505-844-8643, trmanci@sandia.gov 

Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

$380K (NREL), $500K (SNL) 

Objective 

•	 Maintain and upgrade NREL and SNL facilities to support in-house, subcontracted, and work-forothers activities. 

1. Introduction 

DOE national laboratories are government-owned, 

contractor-operated facilities that rely on 

government funding for buildings and equipment. 

Facilities at NREL include the High Flux Solar 

Furnace (HFSF), Mesa Test Area, VSHOT 

laboratory, advanced optical materials laboratory, 

advanced receiver laboratory, and other laboratory 

support facilities. Facilities at SNL include the 

National Solar Thermal Test Facility (NSTTF). 

Both the HFSF and NSTTF are designated by 

DOE as User Facilities, which means that the 

facilities and staff are available for use by U.S. 

industry, universities, other laboratories, state and 

local governments, and the general scientific 

community. Concentrating Solar Power (CSP) 

facilities need to be continually outfitted with the 

most advanced equipment to conduct full-scale, 

CSP research of use to near- and long-term 

development efforts. 

2. Technical Approach 

The technical approach to operating and 

maintaining the NSTTF is to support the six-dish 

mini power plant and to assure that all 

environmental safety and health (ES&H) 

requirements are met at the facility, which includes 

a solar furnace, a 5-MWth central receiver test 

facility, a “mothballed” molten-salt test facility, an 

engine test facility, and a rotating platform for onsun, high-temperature trough testing. The facility 

comprises a laboratory/office/control building, a 

power tower building, and multiple fabrication, test, 

and storage buildings. 

Operation and Maintenance of the NSTTF 

includes monthly, semi-annual, and annual 

inspections and ES&H evaluations, training for all 

site workers, maintenance of all equipment at the 

site, and operation of equipment for testing and 

evaluation. This year we have had a significant 

effort in non-national research test laboratory 

compliance evaluation which requires that all 

equipment be evaluated, tested, and certified by 

either a nationally recognized testing laboratory or 

made compliant via a DOE-certified procedure. 

NREL facilities funding supports facilities space 

located on South Table Mountain (e.g. the HFSF 

and the large payload 2-axis tracker), the VSHOT 

optical test lab, receiver test lab, optical materials 

laboratory, and thermal storage laboratory. 

Capital funds ($136K) were allocated for purchase 

and installation of a new Ci5000 Weatherometer. 

Task Title FY 2007 

Budget ($K) 

1000 MW Initiative Support - NREL 380 

1000 MW Initiative Support - SNL 500 

3. Planned FY 2008 Activities 

As a direct result of low CSP program funding over 

the last 7 years, there has been little maintenance 

done at NREL and SNL facilities. Fiscal year (FY) 

2008 funding for facilities will begin to support 

upgrades necessary to support in-house and 

subcontracted (e.g. FOA) R&D efforts as proposed 

in the FY 08 annual operating plan for specific 

project activities (dish, trough, storage, and 

advanced concepts). 

Solar Thermal R&D

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190
 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

CSP Technology Acceptance 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Mark Mehos (NREL), 303-384-7458, mark_mehos@nrel.gov 

Tom Mancini (SNL), 505-844-8643, trmanci@sandia.gov 

DOE HQ Technology Manager:	 Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2007 Budgets:	 $580K (NREL), $200K (SNL) 

Objectives 

•	 Provide support for Concentrating Solar Power (CSP) Subprogram analysis efforts relating to 

large-scale implementation of concentrating solar power in the southwestern United States. 

•	 Support CSP-specific analysis related to implementation of the Systems-Driven Approach within 

the U.S. Department of Energy’s (DOE) Solar Energy Technologies Program (SETP). 

•	 Support DOE and Energy Information Administration analysis requests on an as-needed basis. 

Accomplishments 

•	 Continued development of the Concentrating Solar Deployment System (CSDS) model. 

•	 Expanded the geographical information system (GIS)-based tool by developing a prototype 

dynamic mapping tool. 

•	 Provided support to utility stakeholders, including the Southwest Joint Development Group. 

Future Directions 

Funding for CSP analysis and outreach has increased for fiscal year (FY) 2008 and will be funded under 

a new project titled “CSP Market Transformation.” Specific market transformation activities will include: 

•	 Continue CSP stakeholder outreach (e.g., staff in state energy, economic, and environment 

offices and utilities). 

•	 Continue the development of tools (GIS, market analysis, economic impact analysis) for use in 

supporting the activities described above. 

•	 Continue providing support of CSP model development in the Solar Advisor Model framework. 

•	 Continue and expand work related to market penetration, with a new emphasis on grid integration 

and expansion studies. 

•	 Expand the resource assessment activity to include reducing the uncertainty of satellite-derived 

solar resource data through improved aerosol optical depth data and ground measurements, 

supporting university- and industry-led resource forecasting efforts, and investigating 

methodologies for projecting long-term seasonal and inter-annual solar resource characteristics 

from short-term data. 

•	 Initiate efforts on a Programmatic Environmental Impact Statement (PEIS) for solar energy 

development on southwestern lands administered by the Bureau of Land Management (BLM). 

1. Introduction southwestern United States and analysis in support 

of stakeholders at the state and federal level. 

The 1000-megawatt (MW) CSP project was initiated 

in FY 2002 based on a congressional request to The focus of the FY 2007 CSP technology 

DOE to investigate the “feasibility of 1000 MW of acceptance activity was to accelerate the 

concentrating solar power in the Southwest by commercialization of concentrating solar power2006.” The original charge has grown and now generation technologies. Analysis shows that cost 

involves a number of activities, including outreach reductions needed for the technologies to be 

and support of state-level activities in the competitive in central power-generation markets will 

result from a combination of advances in research 

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and development, system scale-up, and learning 

and deployment. The technology acceptance 

activity primarily addresses cost reductions resulting 

from deployment. 

This project links directly to the DOE Energy 

Efficiency and Renewable Energy and SETP 

missions to “bring clean, reliable, and affordable 

energy technologies to the marketplace” and to 

“increase the viability and deployment of renewable 

energy technologies.” Cost reductions due to 

learning and deployment, the primary outcome of 

this project, directly support the SETP’s long-term 

goal of achieving wholesale, central power 

generation from solar energy at a cost of $0.05– 

$0.08/kWh. 

2. Technical Approach 

The technology acceptance activity is conducted 

through the SunLab collaboration between NREL 

and SNL. In addition, funding is provided to outside 

contractors—in particular, Fred Morse and 

Associates—to coordinate communications and 

analysis with key CSP stakeholders, including the 

Western Governors’ Association (WGA), major 

southwestern utilities, state energy staff, and state 

and local policy makers. 

As described in previous annual reports, this activity 

originated with the development of a report on the 

potential of 1000 MW of CSP power in the West, 

which was completed and submitted to Congress in 

August 2002. Following the submission of the report, 

a CSP “road show” was formed to provide 

information on the characteristics of CSP 

technologies, the technical potential for CSP within 

each of the southwestern states, and the benefits 

that would accrue from the implementation of CSP. 

In 2006, the CSP program provided substantial 

analytical support for the WGA’s 30 GW Clean and 

Diversified Energy Initiative. This and similar 

stakeholder outreach and analysis efforts continued 

into FY 2007. 

Budget allocations by task are provided below. 

Task Title FY 2007 

Budget ($K) 

1000 MW Initiative Support - NREL 580 

1000 MW Initiative Support - SNL 200 

3. Results and Accomplishments 

The technical work plan focused on the following: 

a. Provide analytical support for stakeholders in 

Southwest. 

b. Develop analytical tools to support these efforts. 

3.1 Analytical Support for Stakeholders in the 

Southwest 

•	 Provided general analytical support to DOE and 

to numerous state stakeholders, as requested 

•	 Provided specific technical support to the 

development of a request for proposals to 

industry for interest in developing a regional 250 

MW Concentrating Solar Power Project. 

3.2 Analytical Tools to Support These Efforts 

•	 Continued the development of the CSDS Model, 

with emphasis on analyzing parabolic systems 

with thermal storage. The model was used to 

investigate the impact of policy scenarios on the 

penetration of CSP in U.S. markets. 

•	 Initiated development of Web-based dynamic 

mapping tools designed to support public (state 

and local stakeholders) and private industry 

requests for siting analysis. 

•	 Completed development of a CSP Jobs and 

Economic Development Impact (JEDI) Model. 

4. Planned FY 2008 Activities 

The activities of this task have increased awareness 

about the technologies among energy decision 

makers in the Southwestern United States. In FY 

2008, we will continue to provide analysis in support 

of stakeholders interested in deploying significant 

levels of CSP in the Southwest. Increased budgets 

in FY 2008 will support a more robust solar resource 

assessment, market penetration, and grid integration 

activity. 

Specific activities identified in the FY 2008 Annual 

Operating Plan include the following: 

•	 Continued CSP stakeholder outreach efforts. 

•	 Continued development of analytical tools for 

use in supporting stakeholder outreach and 

analysis efforts. 

Solar Thermal R&D

Concentrating Solar Power

192
•	 Continued support of CSP model development 

for use in the Solar Advisor Model framework. 

•	 Continued work related to market penetration 

with new emphasis on grid integration and 

expansion studies. 

•	 Expanded resource assessment efforts 

designed to reduce the uncertainty of satellitederived solar resource data, initiate a solar 

resource forecasting activity, and project longterm seasonal and inter-annual solar resource 

characteristics from short-term data. 

•	 Development of a PEIS for solar energy 

development on southwestern lands 

administered by the BLM. 

5. Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2007 

($K) 

Morse Associates, Inc. 

Fred Morse 

Washington, D.C. 

fredmorse@morseassociatesinc.com 

Consulting for government and 

utilities on CSP applications and 

marketing policy 

150 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

CSP Testing and Evaluation: Systems Analysis 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Mark Mehos (NREL, Primary Contact), 303-384-7458, 

mark_mehos@nrel.gov 

Nate Blair (NREL), 303-384-7426, nate_blair@nrel.gov 

Chris Cameron (SNL), 505-844-8161, cpcamer@sandia.gov 

Craig Christensen (NREL), 303-384-7510, craig_christensen@nrel.gov 

DOE HQ Technology Manager:	 Thomas Rueckert, 202-586-0942, Thomas.Rueckert@ee.doe.gov 

FY 2007 Budgets:	 $200K (NREL) 

Objectives 

•	 Develop a Solar Advisor Model (SAM) that will calculate energy output, energy costs, and cash 

flows using up-to-date component and system data while enabling a parametric analysis. 

•	 Validate the Solar Advisor Model (SAM) and, potentially, other solar models for a variety of 

technologies, applications, and locations. 

•	 Provide tools that can be used by industry and government to guide research and development 

(R&D) priorities and to provide credible energy production and cost data using a common 

platform for project development, evaluation, and due diligence. 

•	 Provide additional tools to industry to meet their planning, research and development (R&D), 

siting, and other modeling needs to help accelerate market penetration. 

Accomplishments 

•	 Included concentrating solar power (CSP) parabolic trough modeling within SAM. 

•	 Included detailed incentives within SAM for all technologies. 

•	 Enhanced the model’s graphical outputs, parametrics, and sensitivity analysis 

•	 Significantly improved the model’s calculation speed. 

•	 Completed a dish Stirling performance model through a subcontract. 

Future Directions 

•	 Release a SAM version with the following: 

o	 A major update of the user manual with documentation 

o	 Improved PV performance algorithms 

o	 The ability to use the latest California Energy Commission (CEC) and Sandia module and 

inverter databases 

o	 Detailed operation and maintenance (O&M) inputs (including annual cost, cost per megawatt, 

and cost per megawatt-hour options). 

•	 Release a SAM version with the following: 

o	 Dish Stirling CSP models present 

o	 Enhanced graphical user interface (GUI) and greater graphical output capability. 

o Time-of-use rates. 

• Achieve a 10-km resolution, combined solar radiation and meteorological data set for PV Watts. 

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1. Introduction 

Note: This section replicates the section on 

Solar Modeling with the exception of the $200K 

budget stated above. This budget represents the 

CSP contribution to the overall SAM activity. 

The objective of this project is to provide a focal 

point for system-driven approach (SDA) 

activities as well as a common framework for 

evaluating all solar technologies. This evaluation 

is part of the cost, financing, and performance 

modeling of photovoltaic (PV) systems, 

concentrating solar power (CSP) systems, and 

other solar technologies. 

2. Technical Approach 

The Solar Advisor Model (SAM) task consists of 

systems performance and cost modeling and 

validation projects. The primary function of the 

model is to allow users to investigate the impact 

of variations in physical, cost, and financial 

parameters to better understand their impact on 

key figures of merit. Figures of merit relating to 

the cost and performance of these systems 

include, but are not limited to, system output, 

peak and annual system efficiency, levelized 

cost of energy, and system capital and 

operations and maintenance (O&M) costs. 

The Solar Advisor Model is intended for use by 

DOE and laboratory management and research 

staff, and it is a critical element in the 

implementation of SDA activities relating to 

Solar Energy Technologies Program (SETP) 

planning. The model is, and will continue to be, 

used by members of the solar industry to inform 

the internal R&D directions and to estimate 

system costs and performance. 

3. Results and Accomplishments 

For the Solar Advisor Model, we placed 

particular emphasis up front on the design of a 

user interface that could meet the needs of a 

diverse set of users. User profiles were 

developed to provide a general description of 

DOE, laboratory, and industry users and their 

motivation for using the modeling tool. 

The working model consists of a user-interface 

module for selecting and providing input data on 

the system configuration and operating 

environment, a system-performance module that 

simulates the hour-by-hour output of the 

selected system for the lifetime of a project, a 

cost-input module for providing simple or 

detailed cost inputs for system components, and 

a financial-analysis module for calculating 

system economics. The modules work in concert 

to generate the physical and financial figures of 

merit relevant to a particular user. 

The development portion of SAM focused on 

several areas in FY 2007. Specifically, the 

parabolic trough model was added to SAM for 

use by DOE SETP planners for the CSP 

program and by the CSP industry. The model 

within SAM was originally developed at NREL by 

Hank Price in Excel and called Excelergy. This 

undocumented model was not easily 

transferable to industry or to DOE analysts. 

Implementing the same algorithms within the 

SAM environment makes them more accessible, 

and continuously improving documentation 

makes it easier to help new users get up to 

speed. 

Another area of focus was to improve financial 

methods for the residential, commercial, and 

utility markets. An extensive effort went into 

making the utility financing portion of the model 

accurate and appropriate from the perspective of 

the project developer. Finally, an extensive effort 

was made to incorporate the ability to factor in 

incentives (input tax credits, production tax 

credits, buy-downs, and so forth.) into the model 

for all markets. This is critically important since 

subsidies are so prevalent within solar financing. 

In carrying out these projects, we used 

resources at NREL as well as subcontracts, as 

described in Section 5. 

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4. Planned FY 2008 Activities 

•	 Release a SAM version with additional 

weather file type support. 

•	 Create a user forum and enhance user 

interactivity. 

•	 Validate SAM in comparison to measured 

system data (paper). 

•	 Release a SAM version with the following: 

o	 A major update of the user manual with 

documentation. 

o	 Improved PV performance algorithms. 

o	 The capability of using the latest CEC 

and Sandia module and inverter 

databases. 

o	 Detailed O&M inputs (with annual cost, 

cost per megawatt, and cost per 

megawatt-hour options) 

•	 Hold first modeling workshop concurrently 

with American Solar Energy Society 

meeting. 

•	 Publish a subcontractor report on financial 

model validation. 

•	 Release a SAM version with the following: 

o	 Dish Stirling CSP models present. 

o	 Enhanced GUI and greater graphical 

output capability. 

o Time-of-use rates. 

5. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2007 

($K) 

Janzou Consulting/ 

Steve Janzou 

Evergreen, CO 

Steve_janzou@nrel.gov 

This effort includes programming the 

front-end and basic engine of the 

Solar Advisor Model. 

105 

University of WisconsinMadison/Prof. Sanford 

Klein 

Madison, WI 

Klein@engr.wisc.edu 

For example, development of a dishStirling model for use in SAM. 82 

Paul Gilman Chicago, IL 

PaulGilman@earthlink.net 

Provides user support and technical 

writing support. 35 

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196
 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

Dish Engine Research and Development 

Performing Organization: Sandia National Laboratories (SNL) 

Key Technical Contact: Charles Andraka (SNL), 505-844-8573, ceandra@sandia.gov 

DOE HQ Technology Manager: Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2007 Budget:	 $1,000K 

Objectives 

•	 Improve the reliability and reduce the cost of dish/engine components and systems. 

•	 Support industry in the commercialization of the technology. 

•	 Perform research and development on dish/engine system components and systems. 

•	 Test, evaluate, and improve the performance of dish/engine components and systems. 

Accomplishments 

•	 Continued to operate, maintain, and improve the Stirling Energy Systems (SES) six-dish model 

power plant, cataloging more than 100 development areas. 

•	 Participated as a key member of the commercial product design team. 

•	 Developed systems models for cost studies on facet designs. 

•	 Developed components for a potential production alignment tool. 

•	 Installed Infinia 3-kW system at SNL. 

•	 Assisted Infinia in optical design and systems design of 3-kW system. 

•	 Enhance CIRCE2 model to support finite element analysis-modeled deflections. 

Future Directions 

Primary activities in FY 2008 will support industry’s efforts toward commercialization: 

•	 Continuing to evaluate the reliability of the six-dish mini-power plant. 

•	 Identifying and resolving operational and reliability issues. 

• Testing next-generation components. 

•	 Supporting SES as it begins to deploy a 1-MW power plant. 

•	 Participating in final design processes for SES commercial systems. 

•	 Installing two next-generation Infinia dish systems at SNL. 

•	 Continuing to support Infinia’s commercialization effort 

1. Introduction 

Staff carrying out the U.S. Department of Energy’s 

(DOE) dish-Stirling activities in the Solar Energy 

Technologies Program work closely with industry 

to improve system performance and reliability and 

to support industry deployment in the near term. 

Both of these are explicit goals of the DOE Solar 

Program Multi-Year Program Plan, section 4.2.5.3. 

While we continued to gain operational experience 

with the SES 6-dish Model Power Plant (MPP) at 

SNL, this year we focused on next-generation 

system design, with an emphasis on 

manufacturability. In addition to SES, we 

supported Infinia in its first product development 

and deployment effort. 

The SES system is derived from the successful 

McDonnell Douglas Corporation (MDC) system, 

but it was redesigned to improve the cost. SES’s 

objective is to put this system into production 

within a few years; the target market is bulk power 

production in the southwestern United States. 

Preproduction prototypes will begin deployment in 

the next year, based on lessons learned at SNL. 

SES is pursuing the aggressive deployment of 

25-kW dish-Stirling systems for bulk power 

generation. SES hardware is based on the triedand-true MDC design, with refinements to reduce 

manufacturing costs. SES is working closely with 

an SNL engineering team to maximize the 

possibility of success. 

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The success of the MPP has, in part, led to SES 

signing agreements with Southern California 

Edison for up to 850 MW of power and with San 

Diego Gas and Electric for up to 900 MW of 

power. Operational improvements in the MPP are 

critical in the design process for the deployments. 

SES has made significant progress in developing 

site plans for the plants. The operational plant at 

SNL enabled successful partnerships to be made 

with the utilities and with companies developing 

the site plans. 

This year, the emphasis regarding SES has been 

to convert the prototype system design deployed 

at MPP to a manufacturable design that facilitates 

the logistics of deployment and service. A team 

approach with suppliers was further developed, 

and key suppliers were involved in the design 

process. 

Infinia, previously Stirling Technology Corporation 

(STC), has developed a system around a 3-kW 

free-piston Stirling engine. This system is 

hermetically sealed and requires no maintenance. 

Infinia plans both large and small deployments 

and has targeted photovoltaics as a competitor. 

Sandia National Laboratories was involved in the 

conceptual design, the detailed design, and the 

deployment of the first prototype systems. SNL 

has entered into a memorandum of understanding 

with Infinia to support several Infinia staff on SNL 

premises. 

2. Technical Approach 

SES plans to achieve cost reductions by rapidly 

moving to high production rates in support of bulk 

power production. This approach, when compared 

with smaller prototype installations spread out at 

many locations, has the advantage of lower cost 

through production automation early in the product 

design cycle and lower operations and 

maintenance (O&M) cost through the 

consolidation of O&M resources. 

SNL has provided office, test lab, field, and 

infrastructure facilities to SES at the SNL National 

Solar Thermal Test Facility, which provides direct 

access to technology transfer and expertise and 

allows the engineers daily hands-on access to the 

dish systems. This is critical to accelerating the 

development and deployment path and to rapidly 

training new solar engineers. SNL has also played 

a consultant role in design meetings throughout 

the design life cycle. 

The operation of the MPP at SNL has provided 

continued valuable information about the 

advantages and limitations of existing systems. 

Although several key reliability areas have been 

addressed in the field, a number of issues need to 

be addressed through the redesign. We have 

teamed with the SES design team, both at SES 

and at their strategic partners, to be sure reliability 

issues are addressed in the design-formanufacture stage. The issues identified have 

been systematically categorized for severity and 

impact to the future success of the design. Key 

resources have been applied to the highest priority 

issue areas based on this approach. The 

remaining issues are set aside for the redesign 

process. All of the dish system hardware is funded 

through SES investor financing, while SNL, 

through the DOE CSP Subprogram, provides inkind engineering support, technology transfer, 

training, and facilities. 

Infinia is taking a similar approach. The company 

plans high-rate production to reduce the cost of 

the systems down to competitive levels. While 

initial markets are identified as small business and 

commercial installations, Infinia has proposed 

installations up to 300 MW (see Solar Paces, 

March 2008). 

Infinia has designed a system based on a 3-kW, 

single-cylinder, free-piston engine. Similar 1-kW 

engines have run very well with extended nomaintenance life. The company has designed a 

composite-structure dish system with glass mirrors 

on a composite substrate and a steel rib backing. 

Two dish-related proposals in response to a DOE 

Funding Opportunity Announcement (FOA) were 

selected by the DOE Golden Field Office for 

negotiation. Once these negotiations are 

completed, we anticipate significant laboratory 

involvement in evaluation, testing, and design 

support for these systems. 

3. Results and Accomplishments 

By the end of FY 2007, the MPP dish systems had 

accumulated a total of 16,252 hours on sun. The 

performance of the system continues to exceed 

the performance of the MDC systems, primarily as 

a result of improved system optics, alignment, and 

cooling. 

The SES and Sandia team has continued to 

catalog issue areas. Many of the known issues will 

be addressed in the design-for-manufacture stage, 

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as solutions are impractical as retrofits to the 

existing systems. The formalized Failure 

Reporting, Analysis, and Corrective Action System 

(or FRACAS) ensures that each issue area is 

carried through to design and testing. These data 

have been made available to the entire design 

team for each component. 

Some of the key problem areas have been 

addressed in the field at the MPP. These include 

several high-priority software issues that led to 

repeated nuisance faults, as well as a substantial 

redesign of the gas management system (GMS). 

The manufacturer of the gas valving has been 

involved in the redesign of the GMS, resulting in a 

substantial reduction in cost as well as a very 

significant reduction in fittings, tube length, and 

leak opportunities. The new valves have 

demonstrated several thousand hours of operation 

without faults, and a test rig at the manufacturer 

has demonstrated millions of valve cycles without 

failure. 

The focus of SES this year turned from the 

operation of the MPP to the design of the 

preproduction prototypes and design for 

manufacture. The SES approach includes 

significant involvement with the entire supply 

chain, rather than fully in-house development. One 

engine unit was transferred to the proposed 

engine manufacturer, and the design-formanufacture process has begun, with impressive 

results. SES has done substantial hiring for the 

controls team in preparation for the development 

of next-generation controls for the engine and the 

dish. 

A substantial redesign of the dish system has led 

to a 4000-lb weight reduction and resulted in a 

stiffer system. This was facilitated over the last 2 

years by SNL’s optical code combined with SES’s 

structural model. SES’s steel fabrication partner 

has designed a highly automated fabrication plant 

in conjunction with the redesign effort. The 

refinement of this design is continuing, taking into 

account the key environmental implications of the 

California sites. 

SNL demonstrated components of a proposed 

alignment system that has the potential to allow 

the entire alignment process to be completed in 

20-30 minutes, a key for rapid field assembly. Key 

areas were demonstrated and took advantage of 

SNL’s experience with robotic vision systems. 

SNL also supported Infinia in the development of 

its first 3-kW prototype system. A Sandiadeveloped optical design approach provided a 

facet contour that deviates slightly from a true 

parabola but provides a flat flux profile on the 

receiver without compromising the aperture. This 

was a significant enhancement over the approach 

Infinia had developed, and it will improve the 

system performance by several points of 

efficiency. SNL also supported Infinia in the 

development of dish controls based on SNLdeveloped tracking algorithms and NRELdeveloped sun position algorithms. 

In support of Infinia, SNL changed the CIRCE2 

optical modeling code to support the 

characterization of arbitrarily deflected continuous 

mirror and gore-mirror structures. This change 

allowed the coupling of the optical model to 

Infinia’s structural model, aiding in the optimization 

of the dish design. 

Infinia installed its second prototype system at 

SNL and characterized the mirror assembly. A 

complete system was installed at Infinia’s 

corporate headquarters. The installation took 

place less than 6 months after the conceptual 

design review. 

4. Planned FY 2008 Activities 

SNL and SES have successfully installed and 

continued operating a six-dish MPP to 

demonstrate the technology, develop new 

components and methods, and improve reliability 

in preparation for larger deployments. SES has 

developed agreements with California utilities for 

up to nearly 2 GW of installed capacity. The 

systems have brought unprecedented publicity to 

both the CSP Subprogram and SES. 

SNL will continue to support SES in its aggressive 

schedule for product improvement and 

deployment. The company will next install a 1-MW 

(40-dish) system, followed by high-rate production. 

The involvement of high-production suppliers and 

the national laboratories in the deployment of the 

MPP and the 1-MW plant is key to transitioning to 

production. 

The systems are performing at expected efficiency 

and power production levels, which helps firm up 

predictions for large plant production. Initial 

reliability has been impacted by several known 

problems. SNL and SES have applied engineering 

resources to these problems, implemented short199

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term fixes to the MPP, and outlined development 

paths for the production version. During 2008, we 

will improve the accuracy of key performance 

measurements to more fully characterize system 

performance. 

The partnership between SNL and SES is a new 

way of doing business that maximizes the benefit 

to SES while continuing to leverage the expertise 

developed at the national laboratories. During 

FY 2008, we will accomplish the following: 

•	 Continue to operate the six-dish MPP, 

evaluate performance, and identify reliability 

issues. 

•	 Continue to resolve known issues with field 

validation and design assistance feeding the 

design for manufacturing and assembly 

(DFMA) process. 

•	 Support SES as it begins to deploy a 1-MW 

power plant. 

•	 Actively participate in the DFMA of all major 

components. 

•	 Develop assembly plant and field-deployable 

alignment tools to support rapid deployment. 

•	 Develop rapid deployment component designs 

including foundation, dish structures, and son 

on, and test prototypes at SNL. 

•	 Develop tools to assist in the rapid 

development of next-generation controls, 

including hardware and software simulation 

systems. 

SNL anticipates having significant involvement 

with the two FOAs that are being negotiated by the 

DOE Golden Field Office for dish development 

activities—one with Infinia and one with Brayton 

Energy Systems. 

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____________________________________________________________________________________ 

 

Parabolic Trough Research and Development 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Chuck Kutscher (NREL, Primary Contact), 303-384-7521, 

chuck_kutscher@nrel.gov 

Greg Kolb (SNL), 505-844-1887, gjkolb@sandia.gov 

DOE HQ Technology Manager:	 Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2007 Budgets:	 $2,065K (NREL), $1,080K (SNL) 

Objectives 

•	 Support the development of near-term parabolic trough technology for central-station power 

generation. 

•	 Support the development of advanced technologies for next-generation parabolic trough solar 

fields, thermal energy storage, and power plant technologies to meet the long-term goals of the 

DOE Solar Program Multi-Year Technical Plan. 

•	 Support the expansion of U.S. industry to supply parabolic trough technology. 

•	 Support continued SunLab1

 collaborations on parabolic trough technology development and 

testing. 

Accomplishments 

•	 During FY 2007, Acciona Solar (formerly Solargenix) completed the construction and began the 

operation of a 64-MW parabolic trough plant in Eldorado Valley, near Boulder City, Nevada. The 

plant uses a new second-generation parabolic trough collector design developed under the 

company's USA Trough Initiative R&D contract during FY 2006. The new collector design 

provides a number of advantages over the earlier design: it's cheaper, easier to erect, and does 

not require any alignment of mirrors during assembly. Many of the collectors also use a new, 

improved receiver from Schott Glass. 

•	 SNL refined its theoretical overlay photographic (TOP) alignment system for evaluating the 

alignment of mirrors and receivers on parabolic trough collectors installed in a solar field. 

•	 NREL tested Solel UVAC-2 receiver tubes from the Solar Energy Generating Systems (SEGS) 

field, some of which contained hydrogen in the vacuum annulus and some which did not. This 

allowed us to quantify the impact of hydrogen on heat loss. We also tested the 2006 Schott PTR70 receiver model and found that its heat losses were virtually identical to those of the Solel 

UVAC-2, thus meeting Schott’s design goal at that time. NREL published a paper on the test 

stand results and has since received numerous requests for testing. 

•	 NREL continued the development of a new selective coating that appears to meet the long-term 

selective property goals for parabolic trough receivers. NREL modified its vacuum deposition 

system to allow codeposition of the materials required to make the coating. Initial samples were 

deposited with promising results. 

•	 The Video Scanning Hartmann Optical Test (VSHOT) instrument was used to evaluate the 

accuracy of the new Solargenix SGX-1 concentrator and the improved Industrial Solar 

Technology (IST) PT-1 concentrator. VSHOT testing was also conducted on Luz LS-2 and LS-3 

collectors to provide a baseline for comparison to the new collectors from Solargenix and IST. 

•	 NREL has continued to improve the speed of infrared (IR) imaging of receivers for assessing the 

thermal performance of receivers in the solar field. NREL imaged over 30,000 receivers at SEGS 

III, IV, and V to help FPL Energy categorize receiver performance in advance of a major receiver 

upgrade program. 

1

 SunLab is a collaboration between Sandia National Laboratory and the National Renewable Energy Laboratory in 

support of the U.S. Department of Energy’s R&D activities on concentrating solar power technologies. 

201

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________________________________________________________________________________ 

 

•	 SNL formulated molten salt mixtures of alkali metal nitrates and alkaline earth nitrates that are 

liquids at about 100°C and have useful properties as thermal energy storage fluids in parabolic 

trough systems, including stability in air up to 500°C. 

•	 Nexant completed work on several tasks to look at the optimum size of parabolic trough plants, 

the benefit of building plants in a power park, and the impact of dry cooling on cost and 

performance. 

•	 NREL developed a new selective surface with an absorptance of 0.959 and emittance of 0.007 at 

500oC with high thermal stability. 

•	 NREL began work on a funds-in cooperative research and development agreement (CRADA) 

with Solar Systems to expand the capability of the VSHOT system for measuring reflector surface 

accuracy. 

•	 NREL developed and tested a heat collection element temperature survey system with which one 

or two field personnel can cover 20 MW per day. 

•	 NREL performed a SEGS III–VII heat collection element (HCE) temperature survey for FPL 

Energy and then successfully transferred the HCE Temperature Survey System to FPL Energy to 

complete the plant surveys at Harper Lake. 

•	 NREL completed the design of an outdoor optical efficiency test loop for parabolic trough 

collectors.
 

Future Directions 

•	 Continue the development of advanced receiver and concentrator technologies to meet long-term 

DOE Solar Program Multi-Year Technical Plan goals. 

•	 Working with the NREL Technology Transfer Office, identify interested U.S. industry partners who 

can commercialize the improved solar selective coating technology. 

•	 Support the development of advanced thermal energy storage technologies. 

•	 Support trough funding opportunity announcement (FOA) awardees in response to industry/DOE 

requests. 

•	 Continue building a laboratory capability to support trough testing and analysis. 

1. Introduction 

Parabolic trough technology is being reintroduced 

actively into the marketplace. For example, during 

FY 2007, Acciona Solar (formerly Solargenix) built 

completed the 64-MW Nevada Solar One power 

plant outside Las Vegas (Figure 1). 

Fig. 1. New 64-MW Solar One power plant using 

Acciona parabolic trough concentrators and Schott 

receivers. 

Along with this market development, the DOE 

parabolic trough R&D program has focused on the 

following activities: 

•	 Advance technologies that have an 

opportunity to be deployed in early projects. 

•	 Encourage the development of advanced 

technologies that will improve the 

competitiveness of future parabolic trough 

plants. 

•	 Encourage the expansion of U.S. industry to 

supply these early plants. 

•	 Develop improved tools, testing capabilities, 

and the knowledge base necessary to support 

the needs of a growing U.S. parabolic trough 

industry. 

2. Technical Approach 

Parabolic trough R&D is divided into these three 

areas: 

a. Trough solar field technology. 

b. Thermal energy storage technology. 

c. Trough systems integration. 

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2.1 Trough Solar Field Technology 

The solar field technology agreement focuses on 

SunLab’s development of new parabolic trough 

solar technology and tools for evaluating trough 

technology. During FY 2007, SunLab activities 

focused on the following: 

•	 Development and field testing of an IR camera 

system for the rapid field assessment of 

receiver performance. 

•	 Development and field testing of a new field 

alignment system for assessing the alignment 

of mirrors and receivers on parabolic trough 

concentrators. 

•	 Testing of advanced receiver tubes on NREL’s 

receiver test stand. 

•	 Continued development of advanced selective 

coating technologies for receivers, focusing on 

developing coatings that have improved 

thermo/optic properties and that are thermally 

stable in air up to 500°C. 

2.2 Thermal Energy Storage Technology 

The cost of solar thermal energy storage is about 

$40–$50/kWhthermal. The objective of Thermal 

Energy Storage (TES) R&D is to develop nextgeneration TES technology that will cost 

substantially less ($15–$20/kWhthermal). To achieve 

this goal, DOE’s R&D focuses on modeling 

advanced storage systems and improved storage 

and heat transfer fluids through in-house and costshared contracts with industry. 

Specific FY 2007 activities included these: 

•	 Supported the DOE Golden Field Office with 

the development of a Federal Opportunity 

Announcement (FOA) and reviews of 

proposals for advanced storage systems for 

parabolic troughs 

•	 Began the development of molten salt heat 

transfer fluids with a lower freezing point 

(SNL) 

•	 Measured the presence of hydrogen in field 

receiver tubes (NREL). 

2.3 Systems Integration 

This activity focuses on the development of 

systems-integration tools for evaluating trough 

technologies and assessing program activities. 

Specific FY 2007 activities included these: 

•	 Developed a power plant and heat exchanger 

sizing and cost model for the Solar Advisor 

Model (Nexant). 

• Updated the TroughNet Web site (NREL). 

•	 Organized and held an international trough 

workshop (NREL). 

•	 Generated quarterly milestone reports in 

support of the Concentrating Solar Power 

(CSP) FY 2007 Joule milestone. 

Budget allocations by task are provided in the 

table for both NREL and SNL. 

Task Title FY 2007 

 Budget ($K) 

Solar Field Technology 1,400 

Thermal Storage Technology 1,400 

Trough Systems Integration 345/125* 

*Carry-over from FY 2006. 

3. Results and Accomplishments 

3.1 Solar Field Technology 

In previous years, NREL developed the Video 

Scanning Hartmann Optical Test (VSHOT) system 

for measuring the optical accuracy of reflectors. In 

FY 2007 the instrument was used to evaluate the 

accuracy of the new Solargenix SGX-1 

concentrator and the improved IST PT-1 

concentrator. VSHOT testing was also conducted 

on the Luz LS-2 and LS-3 collectors to provide a 

baseline for comparison to the new collectors from 

Solargenix and IST. 

In FY 2007, NREL also finalized a funds-in 

CRADA with Solar Systems Pty Ltd of Victoria, 

Australia, that will expand the capability of the 

VSHOT apparatus by allowing us to test larger 

aperture reflectors with extensions to flat mirror 

panels (i.e., heliostats). Planned software and 

hardware modifications will be applicable to both 

the CRADA and other program efforts. 

Fig. 2. Optical testing with VSHOT of LS-3 

concentrator at SEGS IX. 

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During FY 2007, SNL continued to field-test and 

improve a new prototype system for conducting 

field alignment checks on parabolic trough 

collectors. The system, called the theoretical 

overlay photographic, or TOP, alignment system, 

can be used to check for misalignment of mirrors 

and receivers. The system concept, shown in 

Figure 3, uses a modification of the distant 

observer approach to assess alignments. In a 

true distant observer approach, the collector is 

viewed from a long distance away and the image 

of the receiver completely fills the image in the 

mirrors. 

The TOP system is a variation that observes the 

collector from a closer vantage point, so that the 

receiver fills only a portion of the image seen in 

the mirrors. The TOP system compares the place 

where the receiver image actually appears vs. 

where it should appear if the collector were 

perfectly aligned. Based on the relative position of 

the receiver’s location in the mirror, we can 

determine any misalignment of mirrors or 

receivers. The TOP system thus allows rapid 

measurement and characterization of large 

commercial solar fields. 

Fig. 3. Prototype TOP alignment system being 

tested at the APS Saguaro parabolic trough plant. 

NREL used computer design software in FY 2007 

to develop a model of a solar-selective coating (α

= 0.959 and ε = 0.070 at 450°C) that is stable at 

high temperatures. Sample coatings were 

fabricated and characterized. The results have 

been encouraging, even though the measured 

optical performance of the deposited coatings was 

inferior to the modeled optical performance 

because of errors known to have occurred during 

deposition of the coating. 

Fig. 4. A sample (foreground) of NREL #6A solar 

selective coating deposited by directly and 

reactively evaporating the layers by elemental 

codeposition. The deposition system is in the 

background. 

NREL also worked in FY 2007 to improve the 

speed of IR field measurements of receiver tubes 

and data analysis to allow a more rapid field 

survey of the condition of receivers. Upgrades to 

the IR system allowed all 9,600 receivers in the 

SEGS VI solar field to be imaged over a 2-day 

period. NREL also replaced the streaming video 

approach for data sampling with a global 

positioning system (GPS)-driven method that 

significantly reduced the amount of data that must 

be processed. This allowed us to rapidly analyze 

more than 30,000 receivers at SEGS III, IV, and V. 

This information was used to show that more than 

half of the receiver tubes in the field had sufficient 

hydrogen in the annulus to decrease trough output 

by as much as 20%. In large part because of 

NREL’s results, plant owner FPL decided to make 

a multi-million-dollar investment to replace the 

receiver tubes that NREL indicated were 

problematic. 

During FY 2007, NREL tested receiver tubes from 

two manufacturers by using its receiver test bed 

(Figure 5). NREL tested Solel UVAC-2 receiver 

tubes from the SEGS field; some of them 

contained hydrogen in the vacuum annulus and 

some did not. This allowed us to quantify the 

impact of hydrogen on heat loss. We also tested 

the 2006 Schott PTR-70 receiver model and found 

that its heat losses were virtually identical to those 

of the Solel UVAC-2, thus meeting Schott’s design 

goal at that time. NREL published a paper on the 

test stand results and has received numerous 

requests for testing since that time. 

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Fig. 5. Parabolic trough receiver thermal loss test 

bed 

Fig. 6. Parabolic trough receiver thermal loss test 

bed results. 

In FY 2007, the NREL outdoor optical efficiency 

test loop was designed using an Engineering 

Equation Solver, or EES, model of the system. 

FY 2007 milestones achieved were as follows: 

•	 Made laboratory receiver heat loss 

measurements of Schott PTR-70 and Solel 

UVAC2. 

•	 Submitted detailed report describing receiver 

test bed. 

•	 Conducted IR surveys of SEGS III-V receiver 

tubes. 

•	 Designed the NREL outdoor optical efficiency 

test loop. 

•	 Developed the HCE Temperature Survey 

System capable of covering 20 MW per day 

with one or two field personnel. 

•	 Provided HCE Thermal Analysis support to 

Sunray Energy and assisted them in 

understanding the performance of HCEs 

purchased from FPL Energy and the effects of 

adding argon into the annulus as well as air. 

•	 Performed a SEGS III–VII HCE temperature 

survey for FPL Energy and then successfully 

transferred the HCE Temperature Survey 

System to FPL Energy to complete the plant 

surveys at Harper Lake. 

3.2 Thermal Energy Storage Technology 

A SunLab and industry team prepared a thermal 

energy storage development plan for parabolic 

trough technology. The plan envisions a move to 

inorganic molten salts as the heat transfer fluid in 

the solar field; it appears to be the most promising 

opportunity for reducing costs and for improving 

the overall economics of parabolic trough plants in 

the future. In FY 2007, SunLab staff conducted a 

visit to the Italian National Agency for New 

Technologies, Energy and the Environment to see 

its parabolic trough molten-salt test facility. The 

storage team also met with staff at the German 

Aerospace Center to get an update on its concrete 

and phase-change-material thermal storage 

activities. The planned development of a 

thermocline storage system at the APS Saguaro 

plant was dropped because APS had to turn its 

attention to other projects. 

During FY 2007, advanced fluid work focused on 

understanding the thermal decomposition 

mechanisms for Therminol VP-1. The 

decomposition of the heat transfer fluid is 

important not only because of the replacement 

cost of the fluid, but also because the 

decomposition of the fluid results in the presence 

of hydrogen in the fluid, which is an issue for 

maintaining the vacuum in the receiver. 

NREL performed an analysis to determine the rate 

at which hydrogen diffuses from the working fluid 

into the initially evacuated annulus. NREL also 

performed a literature search to investigate the 

impact of injecting a heavier inert gas such as 

xenon into the vacuum space to mitigate the 

additional heat loss caused by the hydrogen. 

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heat loss (W/m HCE length)

0.0001 0.001 0.01 0.1 1 10 100 1000 

300 

400 

500 

600 

700 

800 

900 

1000 

Air 

Argon 

Hydrogen 

desired vacuum level 

Tabs = 400 °C 

vw = 0 mph 

εabs 

Tamb = 16 °C 

= 0.15 

Pannulus (torr) 

Fig. 7. Model results showing how the presence of 1000 

10000 

Solar salt 

QA 

QB 

Ternary 

QC 

Nitrite Concentration (ppm) 

P,O2 = 0.19 atm. (ABQ) 

20000 

5000 

Solar salt 

(Na,K)NO3 

relatively small quantities of hydrogen in the 

vacuum space significantly increases heat losses 

from a receiver. 

Another option for advanced heat transfer fluids is 

to identify and develop alternative inorganic 

molten salt formulations. Current formulations, 

while offering many advantages over the 

Therminol oil used in the SEGS plants, have 

distinct disadvantages. Primary among these are 

high freezing temperatures, higher costs, and 

unidentified potential material interaction issues. 

Recent developments of multicomponent molten 

salt formulations consisting of common alkali 

nitrate and alkaline earth nitrate salts display 

freeze-onset temperatures below 100°C. In 

addition to phase-change behavior, several 

properties of these molten salts were evaluated 

that significantly affect their suitability as thermal 

energy storage fluids, including chemical stability 

and viscosity. These alternative molten salts have 

demonstrated chemical stability in the presence of 

air up to approximately 500°C in laboratory testing, 

and they follow chemical equilibrium relationships 

that have been reported for solar salt (NaNO3 and 

KNO3), as shown in the graph of Figure 8. 

Experimental measurements of viscosity were 

performed from near the freeze-onset temperature 

to about 200°C. Viscosities can exceed 100 cP at 

the lowest temperature but are less than 10 cP in 

the primary temperature range at which the 

mixtures would be used in a thermal energy 

storage system. The compatibility of container 

materials is not anticipated to be a problem, and 

experiments are in progress to confirm the 

corrosion behavior of a wide variety of metallic 

materials. 

375 400 425 450 475 500 525 550 

Temperature (°C) 

Fig. 8. The equilibrium chemistry of new molten 

salt mixtures (QA, QB, QC) follows the 

temperature dependence of binary solar salt. 

Testing completed at SNL during FY 2002 through 

FY 2004 identified both the potential benefits 

associated with improved molten salt formulations 

and some of the key issues related to their use in 

parabolic trough solar fields. Planning in FY 2005 

and work in FY 2006 focused on investigating a 

large suite of potential nitrate and nitrite salt 

constituents that might be combined to yield 

favorable heat transfer fluid properties at a 

reasonable cost. Detailed plans were written to 

continue a phased development program during 

FY 2007. 

At the same time, freeze protection and recovery 

from freeze events in solar fields will remain a key 

issue even with improved salt formulations that 

exhibit lower freeze points. As such, simple 

modeling of likely freeze events was completed in 

solar fields that will contain heat collection 

elements with widely variable conditions and heat 

loss characteristics. This modeling identified the 

need for a comprehensive testing program 

involving freeze protection and recovery methods 

based on impedance heating designs. This testing 

will occur during FY 2007 and 2008. 

In addition, Nexant prepared a manual on a 

storage model developed for the SAM model. 

Solar Thermal R&D

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FY 2007 Milestones: 

•	 Modeled the impact of hydrogen diffusion into 

the vacuum space of a parabolic trough 

receiver. 

•	 Formulated molten salt mixtures of alkali metal 

nitrates and alkaline earth nitrates that are 

liquids at about 100°C and have useful 

properties as thermal energy storage fluids in 

parabolic trough systems. 

•	 Determined through experiments and 

chemical analysis that molten salt mixtures are 

thermally stable in air up to at least 500°C. 

•	 Measured the viscosity of these molten salts 

near the low-temperature end of the usable 

range. 

3.3 Systems Integration 

Using Nexant analysis and Excelergy runs, NREL 

authors published a paper describing the optimum 

size and economics of parabolic trough power 

plants with and without storage. The paper shows 

that building four 250-MWe plants together could 

reduce the cost of energy by about 10% to 12%. 

Nexant also prepared a solar field piping model for 

incorporation in the SAM model. 

During FY 2007, NREL updated the TroughNet 

Web site. A major part of that work was to have all 

technical reports from subcontractors updated and 

placed on the Web. TroughNet was moved from 

the EERE Web site to the NREL site (see 

www.nrel.gov/csp/troughnet/). 

NREL conducted a trough workshop in April 2007. 

Approximately 140 researchers from around the 

world participated; presentations are online at 

www.nrel.gov/csp/troughnet/wkshp_2007.html. 

In addition, quarterly milestone reports were 

generated in support of CSP. 

FY 2007 Milestones: 

•	 Held a trough workshop. 

•	 Presented a paper on parabolic trough system 

sizing and economics at the American Society 

of Mechanical Engineers Solar Energy 

Division meeting. 

4. Planned FY 2008 Activities 

Key activities planned for FY 2007 include these: 

•	 Perform modeling and testing of inert gas 

mixtures in receiver tubes to quantify improved 

heat loss characteristics of tubes containing 

hydrogen. 

•	 Transfer receiver heat loss IR field 

measurement technology to industry. 

•	 Provide VSHOT testing support to Abengoa 

Solar, testing its advanced concentrator in 

Seville, Spain, and its PT-2 prototype in its 

U.S. location. 

•	 Provide VSHOT testing support to SkyFuel, 

Inc., as the company develops its trough 

concentrator prototype. 

•	 Perform VSHOT characterization of new 

mirror technology for Guardian Glass and 

Naugatuck Glass. 

•	 Develop two new VSHOT systems: one 

portable system for full aperture trough 

characterization in the field and at industry 

partner facilities and another for laboratory 

testing of flat and single axis curvature mirrors. 

•	 Compare VSHOT results with photogrammetry 

results. 

•	 Perform heat loss measurements of new 

Schott receiver tubes. 

•	 Fully characterize the hydrogen generation 

process within the SEGS plants and develop a 

design that removes hydrogen from the HTF 

and eliminates significant migration of 

hydrogen into the receiver annulus. 

•	 Perform a field demonstration of the new TOP 

concentrator optical alignment tool at the 

SEGS plants. 

•	 Complete and release the solicitation for 

advanced HTF/TES and negotiate and place 

contracts for R&D and demonstration work. 

•	 Complete the construction of the NREL 

outdoor optical efficiency test loop. 

•	 Perform outdoor optical tests on the 

Gossamer parabolic trough. 

•	 Provide ongoing technical support for the FOA 

awardees, including critical review of work 

progress and recommendations for future 

technical work. 

•	 Work with the NREL Technology Transfer 

Office to identify interested U.S. industry 

partners who could commercialize the 

improved solar selective coating. 

•	 Expand the range of constituents that may 

further depress the initial solidification 

temperature of molten salt mixtures and 

evaluate costs. 

•	 Evaluate the corrosion resistance of stainless 

steels and alloy steels in low-melting molten 

salt mixtures to confirm that no corrosion 

problems exist. 

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5. Major FY 2007 Publications 

B. Kelly, D. Brosseau, H. Price, and D. Kearney, 

“Adopting Nitrate/Nitrite Salt Mixtures as the 

Heat Transport Fluid in Parabolic Trough Power 

Plants,” Proceedings of the 2007 Energy 

Sustainability (ES2007) Conference, Long 

Beach, CA, 27-30 June (2007). 

L Moens and D. Blake, Mechanism of Hydrogen 

Formation in Solar Parabolic Trough Receivers, 

report no. NREL/TP-510-42468, Golden, CO: 

National Renewable Energy Laboratory, 

February (2008). 

Nexant, Inc., Collector Field Piping Optimization 

Model: Inputs to User’s Manual, prepared for the 

National Renewable Energy Laboratory under 

Subcontract LDC-6-66283-01, December 14 

(2006). 

Nexant, Inc., Thermal Energy Storage Models: 

Inputs to User’s Manuals, prepared for the 

National Renewable Energy Laboratory under 

Subcontract LDC-6-66283-01, January 5 (2007). 

H. Price, M. Mehos, C. Kutscher, and N. Blair, 

“Current and Future Economics of Parabolic 

Trough Technology,” Proceedings of the 2007 

Energy Sustainability (ES2007) Conference, 

Long Beach, CA, 27-30 June (2007). 

6. University and Industry Partners 

The following organizations received subcontract funds to support activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 

2007 

($K) 

Cost 

Share 

Nexant 

Bruce Kelly 

San Francisco, CA 

bdkelly@nexant.com 

Dry cooling analysis, power plant size 

optimization study, APS thermocline 

TES engineering design and cost 

100 

Kearney and 

Associates 

Seattle, WA 

dwk@jkearney.com 

Thermal storage and trough analysis 

support 25 

Solar Thermal R&D

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208
 

Solar Water Heating Systems Development 

The Solar Water Heating (SWH) Systems Development consists of research and technology 

development programs for solar water heaters and hybrid solar lighting systems. The program 

works with industry, the national laboratories, and others to develop and demonstrate systems 

and components that will improve the reliability and reduce the cost of these solar systems. The 

Technical Assistance Program aids builders, manufacturers, and others in designing and 

installing solar water heating systems. To ensure that safe and reliable systems are installed, the 

program supports the testing and certification activities of the Solar Rating and Certification 

Corporation. 

Although solar water heaters have been manufactured and used for some time, there are still 

barriers to their widespread use, which the DOE Solar Program is working to overcome. The 

primary issues are the cost, reliability of systems, and the unfamiliarity of related but very 

necessary trades such as builders, architects, plumbers, roofers and other mechanical 

contractors. 

SH&L research emphasizes the development of low-cost, polymer-based solar water heaters, 

with the goal of reducing the levelized cost of energy for these systems by at least 50%. The 

DOE program works with two industrial teams to develop a new generation of low-cost polymer 

water heaters that could reduce the cost of solar water heaters because of less expensive 

materials and simplified manufacturing, assembling, and installation. 

Achievements in Market Transformation for FY 2007 include: 

Solar Thermal for Zero Energy Homes 

•	 Supported industry, such as teams that introduced two low-cost systems into the solar 

water heater market with costs reduced more than 50% in comparison to the cost of 

today’s more conventional metal-and-glass solar water heaters. 

•	 Established the durability of proposed polymer components, including glazings and 

connectors. 

Hybrid Solar Lighting 

•	 Conducted field testing at the hybrid solar lighting beta sites across the United States as 

part of the Sunlight Inside Initiative and then prepared a summary of the results. 

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Solar Water Heating Systems Development
 

 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

Solar Thermal for Zero-Energy Homes 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Jay Burch (NREL, Primary Contact), 303-384-7508, jay_burch@nrel.gov 

Greg Kolb (SNL), 505-844-1887, gjkolb@sandia.gov 

DOE HQ Technology Manager:	 Bob Hassett, 202-586-8163, robert.hassett@hq.doe.gov 

FY 2007 Budgets: $2,037K (Total): $1,407K (NREL), $100K (SNL), $530K (DOE Golden 

Field Office) 

Objectives 

•	 Identify the solar thermal systems that can significantly contribute to attaining cost-neutral zeroenergy homes. 

•	 Support field trials and refinement of low-cost solar water heaters in mild climates that reduce the 

levelized cost of energy by at least 50%. 

•	 Provide technical support for the emerging U.S. solar water heater market. 

Accomplishments 

•	 Produced a strategic plan identifying how solar thermal systems can contribute to attaining costneutral zero-energy homes. 

•	 Supported industry teams such as those that introduced two low-cost systems into the solar water 

heater market in FY 2007 with costs reduced more than 50% in comparison to the cost of today’s 

more conventional metal-and-glass solar water heaters. 

•	 Established the durability of proposed polymer components, including glazings and connectors. 

•	 Produced combined photovoltaic (PV)/thermal simulation models for six different configurations. 

•	 Identified liquid desiccant-based cooling systems as preferred for solar-activated cooling, and 

explored synergies with strong liquid-desiccant as a latent heat storage mechanism. 

Future Directions 

•	 Begin development of exemplary low-cost solar water-heating systems for zero-energy homes in 

cold climates. 

•	 Continue the development of combined PV/thermal systems for zero-energy homes that will be 

cost-competitive with conventional technologies and that can be used for water heating and 

space conditioning as well as electricity production. 

•	 Develop tools for assessing and optimizing solar thermal systems addressing major end uses of 

water heating, space heating, and/or space cooling in zero-energy homes. 

1. Introduction 

Before FY 2008, the primary goal of the U.S. 

Department of Energy’s (DOE) Solar Heating and 

Cooling (SHC) subprogram was the development 

of low-cost solar water heaters that would reduce 

the levelized cost of energy (LCOE) by at least 

50%. In FY 2008, the SHC was moved from the 

Solar Energy Technologies Program (SETP) to the 

Building Technologies Program (BTP). The 

primary goal of the BTP is cost-neutral zeroenergy homes in all U.S. climate zones by 2020. 

For residential buildings, this effort is housed in 

the Building America Program. Although zeroenergy homes (ZEH) are readily attainable with 

today’s technologies, the cost is prohibitively high 

and not cost-neutral. Moving the SHC subprogram 

from the SETP to the BTP recognizes that solar 

thermal technology is a critical element of a costneutral ZEH. The new goal of SHC work is to 

develop active solar systems that cost effectively 

meet the thermal loads of ZEH, including water 

heating and space conditioning. 

The development of low-cost solar water heaters 

(SWH) will remain part of the SHC R&D effort, 

Solar Thermal R&D

Solar Water Heating Systems Development

210
 

because the water-heating load is a relatively high 

percentage of the total load (especially in ZEH), 

and it is difficult to reduce that load by other 

means. Gas tankless water heaters are becoming 

popular, but they result in only ~30% savings. 

Further reductions require SWH and are 

necessary to reach the 50% savings level and 

beyond. SHC R&D will also continue to support 

the SWH industry, which is essential in providing 

products for ZEH. 

2. Technical Approach 

Program agreements and funding are shown in 

Table 1. 

Table 1. Tasks in the SHC Subprogram 

Agreement/Task Title FY 2007 

($K) 

Solar Thermal Pathways to ZEH 607 

Low-Cost SWH for ZEH 575 

Combined PV/T Systems for ZEH 325 

2.1 Solar Thermal Pathways to ZEH 

An assessment of SWH was conducted that 

indicated the need and potential for lowering costs 

through R&D, particularly for SWH in cold 

climates. The United States was divided in 13 

climate zones, with a representative city in each 

zone for solar irradiance and system performance. 

Aggregated quantities were population-weighted. 

A market analysis was then performed using 

empirical correlations for market ramp-up and 

steady-state penetration. 

The ideal way to determine if solar thermal can 

contribute to ZEH is to model the performance and 

cost of all systems that could contribute cost 

effectively and include them in a simulation-based 

building optimization analysis. The BTP uses the 

optimization tool BEopt, which places a technology 

or “measure” into the design package for a 

building at a given savings level based on the 

marginal cost of energy for that measure being the 

lowest for all remaining options with that particular 

house at the current savings level. Solar water 

heaters were analyzed with this approach. Tools 

are under development for PV/thermal and space 

conditioning systems, and this approach cannot be 

used for those systems until the tools are available 

and integrated into BEopt. 

2.2 Low-Cost Solar Water Heaters for ZEH 

The program has supported industry teams in a 

stage-gate process to develop low-cost SWH for 

mild climates based on the use of low-cost 

polymer materials and manufacturing. Initially, six 

teams developed the low-cost concepts. After the 

conceptual development, two of the teams—from 

Davis Energy Group (DEG) and FAFCO, Inc.— 

were selected to continue and are in the last 

stages of development, refining the product and 

developing efficient manufacturing processes. 

NREL and the University of Minnesota have 

provided technical support in modeling, 

performance testing, and materials durability. 

To ensure that the products have an acceptable 

life, NREL and the University of Minnesota have 

conducted accelerated testing on the materials. 

Accelerated test methods included accelerated 

ultraviolet (UV) testing at 2 suns (in a temperature 

and humidity-controlled chamber) and at 25-50 

suns (using an outdoor concentrator with cooled 

sample mount), as well as high-chlorine baths with 

high oxidation potential. Chambers for accelerated 

temperature aging were also used. Electron 

microscopy, X-ray diffraction, X-ray photoelectron 

spectroscopy and oxidation induction techniques 

were used in polymer lifetime and scaling studies. 

Subcontracts were issued to two industry teams 

developing low-cost SWH for mild climates. Both 

teams have products approved by the Solar 

Rating and Certification Corporation (SRCC) and 

available to the market (albeit not yet in all 

intended distribution channels). The DEG 

subcontract supports large-scale field 

demonstrations in part and funds R&D to reduce 

the cost of glazing and heat exchanger 

subassemblies. The FAFCO subcontract funds 

testing and field monitoring of its low-cost, 

unglazed drainback system. 

An ongoing subcontract with the University of 

Minnesota funds heat exchangers work, including 

fundamental studies of heat exchangers and 

storage and in lifetimes and scaling of polymer 

tubing. An ongoing subcontract with Thermal 

Energy Systems Specialists, Inc., is helping to 

develop thermal modeling for the team’s systems. 

2.3 Combined PV/thermal Systems for ZEH 

To analyze the potential for a PV/thermal system 

to contribute to ZEH, the possible configurations 

are to be modeled in TRNSYS, which is 

compatible with BEopt. Both air and liquid systems 

were modeled, with variations in back-plane 

boundary conditions. A subcontract was issued to 

SunEarth, Inc., to develop the balance-of-system 

for its proposed combined PV/thermal system. 

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2.4. Industry Support 

Under the SETP Solar America Initiative (SAI), we 

maintained close connections with those leading 

local Solar Cities and Solar America Showcases 

projects, by sitting on advisory panels, 

participating on Tiger Teams, presenting at 

stakeholder meetings, and leading industry 

standards groups. Requests from SAI/Solar Cities 

have included user-friendly, Web-accessible tools 

for economic analyses of SWH savings and solar 

pool systems for municipal and school pools. 

3. Results and Accomplishments 

3.1 Solar Thermal Pathways to ZEH 

A report issued on the technical potential for 

savings from SWH served as background 

information for a report to Congress on the 

potential for solar water heating. U.S. waterheating consumption is ~4 quads per year (Q/yr). 

A conservative approach was taken, assuming 

regional solar fractions averaging ~1/2 and 

available rooftops averaging ~50%, resulting in a 

potential near 1 Q/yr. An economic analysis done 

to set SWH cost goals showed that the system 

cost required to attain cost-neutrality vs. electricity 

(a savings-to-investment ratio of 1) (see Figure 1). 

Even against electricity, the current installed newconstruction cost is $6000 for a 40-ft2

 system 

($150/ft2

), and this implies that the current 

technology is cost-neutral without rebates in less 

than 1/30th of the country. This situation becomes 

even worse for SWH when gas is the auxiliary 

fuel. It is very clear that rebates and/or lower cost 

systems are needed to reach cost neutrality for 

SWH in most of the nation. 

A report on the economics and market potential for 

SWH that contains those results was provided to 

Congress, as requested in FY 2008 congressional 

funding language. 

A strategic plan was also developed that identified 

the “critical path” solar thermal technologies and 

systems that can contribute to achieving costneutral zero-energy homes. This is the only 

program FY 2008 milestone. The plan identifies 

three system types needed to attain cost-neutral 

ZEH: (1) solar water heaters are needed to 

achieve the 50% savings level and beyond in the 

near term; (2) PV/thermal systems are needed to 

provide water heating, some space heating, and 

space cooling for the 50% savings level and 

beyond, especially when there is limited roof 

space; and (3) “triple-play” systems meeting water 

heating, space heating, and space cooling loads 

are needed for ZEH to reach cost-neutrality. 

Table 2. Milestones for Solar Heating 

and Cooling 

Milestone- Strategic Plan 

Level Description Date 

4 

Identify “critical path” solar thermal 

systems to achieve cost-neutral 

ZEH 

06/07 

Through an analysis using BEopt, it was shown 

that, for houses with natural gas, SWH becomes 

more cost-effective than other measures at levels 

of savings ≥ ~45%. At these savings levels, for 

example, walls have already been improved; 

added insulation (though inexpensive) produces 

very low additional savings. Installed prices 

assumed for SHW are shown in Table 3 and are 

intended to represent best attainable costs in new 

construction as of 2004. Today’s prices are 

probably ~25%-50% higher. Cost neutrality is 

reached at about 60%, depending on climate. This 

is slightly after the “PV-takeoff” point (where PV is 

the most cost-effective remaining measure and is 

added until savings are ~100%). Beyond this 

point, cost-neutrality cannot be achieved without 

significant further cost reductions or rebates. 

Table 3. Assumed Solar Water Heater Costs 

 as of 2004 

Name/size Installed Price 

ICS/32 ft2

 $2,654 

Glycol/40 ft2

 $4,307 

Glycol/64 ft2

 $4,768 Fig. 1. System installed cost needed to produce a 

savings-to-investment ratio of 1. 

Solar Thermal R&D

Solar Water Heating Systems Development

212
 

 In BEopt optimizations, the solar water heater was 

always paired with a gas tankless water heater 

(GTWH) as the optimal water heating system. 

However, GTWH with feedback control can cause 

unstable oscillations when the preheated water is 

too warm for the lowest available burner setting. 

Solar preheat voids the warranty on the majority of 

tankless water heaters. A paper on tankless-solar 

combinations was published suggesting that 

adding a small tank to the system can resolve the 

issue. Recent data shows, however, that the 

combination can induce other issues needing to 

be resolved. 

NREL and SNL investigated thermally activated 

residential cooling technology to identify preferred 

system types. Absorption and desiccant 

technologies were candidates. A critical feature is 

the required temperature from the solar system. 

Although absorption technologies are available in 

large, gas-driven tonnage, they are intended for 

use with gas, as high temperatures (e.g., ~200oC) 

are required for double-effect chillers. This makes 

it challenging to use them with solar. Desiccants 

can be regenerated at temperatures as low as 

140o

F, however. The technology is made more 

attractive by recent advances that include 

noncorrosive polymer systems, 20X reduction in 

flow rate through system redesign, and the 

elimination of demisters (zero-carryover). 

Liquid desiccants have a potentially important 

synergy with seasonal storage for space heating. 

By storing both the strong desiccant regenerated 

with abundant summer sun and the attendant 

sensible heat, this technology can regenerate heat 

in winter when solar resources are low. This is 

done by the reverse of the regeneration process: 

water vapor produced by the low-temperature 

sensible storage is absorbed by the strong 

desiccant in a “heat generator,” producing hightemperature heat. The net result is that the 

storage density of the desiccant tank is increased 

relative to that of water-based sensible storage by 

up to 10X, depending on the desiccant 

concentration lower limit where heat pumping is no 

longer sufficiently effective (see Figure 2). 

Comparison of Sensible and Latent desiccant storage capacities 

Desiccant storage from C = 0.55 to Cmin 

0 

200 

400 

600 

800 

1000 

1200 

1400 

Heat storage capacity, kJ / L .

Sensible storage, water 

CaCl2 Maximum 

70% Efficiency 

50% Efficiency 

30% Efficiency 

Sensible storage in 

water (ΔT = 40C) 

0.3 0.35 0.4 0.45 0.5 0.55 

Minimum Concentration, Cmin 

Fig. 2. Latent heat storage per unit volume of final 

weak desiccant, as a function of the minimum 

weak desiccant concentration. 

3.2 Low-Cost Solar Water Heaters for ZEH 

FAFCO introduced its unglazed drainback solar 

water heater to the market in February 2007 at the 

Homebuilder’s Show in Las Vegas, Nevada (see 

Figure 3). More than 1000 systems have been 

sold to date, through FAFCO’s existing distribution 

network. The company’s development subcontract 

allows for the refinement of controls, and begins to 

resolve fundamental issues in the testing of 

unglazed collectors in regard to wind affects. A 

four-system test facility is also being constructed. 

Fig. 3. The FAFCO display at the 2007 

Homebuilders’ Show, where the SHC-supported 

system was introduced to the builder market. 

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Davis Energy Group was issued a subcontract 

funding the refinement of the glazing and heat 

exchanger as well as larger-scale demonstrations. 

The polycarbonate glazing used previously added 

over $200 to the cost of the system, and the team 

has developed an acrylic alternative costing ~50% 

less. The previous heat exchanger design proved 

to be too laborious to manufacture, because of the 

in the NREL Ci5000 weatherometer (WOM), for a 

UV dose equivalent to more than 39 years in 

Florida, without losing transmittance. 

Equivalent Exposure in FL (y) 

0 2 46 8 10 

90 

Solar-Weighted Transmittance (%) 85 

80 

75 Impact Modified Acrylic 

Company B; Material 1 

Company A; Material 2 

Fiber Reinforced Polyester 

dozens of brazed connections. The new design 

will use long pieces of soft copper to eliminate the 

majority of the brazed connections. A 40-unit 

demonstration project was completed at a migrant 

housing facility (see Figure 4). The team is also 

finalizing a demonstration project funded primarily 

through the California Air Resources Board 

(CARB). CARB has set aside $235K for the 70 

project, which will install 80 systems in highpollution areas statewide. 

During FY 2007, the Materials Durability subtask 

at NREL emphasized four areas of research. 

These included (1) continued testing of polymer 

sheet glazings using NREL’s UV concentrator, (2) 

the assessment of polymer film glazing 

candidates, (3) accelerated testing of the 

mechanical properties of polymeric fittings, and (4) 

the development of a capability to conduct hail 

testing of evacuated tube collectors. 

Fig. 4. SunCache glazed integrated collector 

storage at a migrant housing camp near Davis, 

California. 

Solar-weighted transmittances as a function of UV 

dose for samples of interest to industry teams are 

shown in Figure 5. Optical performance stays 

steady after a cumulative UV dose equivalent to 

~6 years outdoor exposure in Miami, Florida. 

Although acrylic films maintain optical durability, 

they are too brittle to withstand mechanical stress. 

They also sag unduly under relatively modest 

temperatures. Two commercial ethylene 

tetrafluoroethylene (ETFE) fluoropolymer films 

were exposed at 3 sites outdoors for 6 years and 

0 500 1000 1500 2000 2500 

Total UV Dose (MJ/m2) 

Fig. 5. Optical durability of polymer sheet glazing 

samples in NREL’s UV concentrator. 

Two candidate polymer materials used for 

connectors exposed outdoors (polypropylene (PP) 

and polysulfone (PSU)) were tested for percent 

elongation at break, a parameter that is indicative 

of ductility, a material’s ability to avoid failure 

associated with brittle fracture. Results show that 

PP had superior elongation before UV exposure, 

and degraded less than PSU under UV. 

Consequently, our industrial partner chose to use 

PP fittings with its systems. A deluge of 

evacuated-tube systems has entered the U.S. 

market; the resistance of these tubes to hail 

damage is critical but unknown. In response to 

these needs, we have developed a facility for hail 

testing. Hail balls are launched by a commerciallyavailable hail gun, which is essentially a giant 

sling-shot. Testing will begin during FY 2008. 

The University of Minnesota (UM) provides 

support to the industry teams and the program in 

the areas of storage, heat exchangers, polymer 

tubing durability, and scaling. Building on previous 

work, and at the program’s request, the UM team 

explored ways to improve the thermal 

performance of storage tanks with immersed heat 

exchangers. The team designed a cylindrical 

baffle that constricts and accelerates natural 

convection flow around an immersed coil heat 

exchanger and prevents mixing of descending 

plumes with the hot tank water (see Figure 6a). 

The baffle increases the storage-side convective 

heat transfer coefficient to the heat exchanger by 

20% (Figure 6b), with a similar increase in εhx if the 

exterior film coefficient is dominant. The UM team 

also evaluated the potential of metal foam 

Solar Thermal R&D

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214

3000 
No Baffle

uncertainty Baffle

No baffle

With baffle No Baffle

uncertainty Baffle

No baffle

With baffle No Baffle

Baffle

structures to improve heat transfer to immersed 100 

heat exchangers. Experiments were conducted 

showing that the tested metal foam provides from 80 

30% to 140% enhancement of heat transfer. 

Although commercial foams are prohibitively 

expensive, UM is currently building foam-like 

structures from low-cost screens that may also 

OIT (min)

60 

40 

0 0.2 0.4 0.6 0.8 1 

Distance from Surface (mm) 

provide substantial improvements in heat transfer. 20 

0.8 0 

0.7 

0.6 

389 hours, DI water 330 hours, 5 ppm Chlorine 0.5 

uncertainty 

No baffle 

With baffle 

0 10 20 30 40 50 60 

t (min) 

HX0.4 Fig. 7. Oxidation induction time data vs. depth for ε HX

2-mm-thick polyethylene samples. 

Scaling, or the accumulation of mineral deposits 

0.3 

0.2 

0.1 

0 on surfaces, is a potential problem in polymer heat 

exchangers operated in an open loop with hard 

water. Scaling was characterized in two types of 

flow-through systems: (1) long-term testing, with a 

realistic, tap water composition and temperature, 

and (2) short-term testing, with distilled water of 

high supersaturation (S). Both PP tubes and 

copper (Cu) tubes were exposed to mildly 

supersaturated tap water at 40°C for times up to 8 

weeks. The water composition was controlled for 

calcium carbonate (S = 5). Figure 8a compares 

the accumulation of CaCO3 deposits on 

polypropylene and copper tubes for the tap-water 

case. Scale on the copper tubes was greater than 

that on the polypropylene. 

Figure 8b compares the scale accumulation in the 

Cu and PP tubes exposed to mildly 

supersaturated distilled water at room 

temperature. Under these conditions, the PP 

accumulates more scale than does the Cu. 

Compared with the long-term study in tap water, 

these rates are three orders of magnitude higher. 

The comparison between the long-term, tap water 

study and the distilled water study demonstrates 

the importance of water chemistry in evaluating 

the potential for scale. Scaling in tap water, with 

various ionic components, is very different from 

scaling in distilled or deionized water with a single 

supersaturated component. 

(a) (b) 

Fig. 6. Enhancement of immersed heat 

exchangers: (a) baffle-coil heat exchanger 

schematic; (b) heat exchanger effectiveness vs. 

time, with and without the baffle. 

Low-cost polymer heat exchangers must have 

long life. The durability of potential polymer heat 

exchangers has been shown in previous work to 

depend mostly on the diffusion of antioxidants 

from the tube. Work at UM is continuing in 

collaboration with a well-known polymer industry 

partner on the experimental verification of the 

diffusion model, determining previously unknown 

diffusion coefficients. Initial data indicate 

significant acceleration of antioxidant loss in 

chlorinated water vs. deionized water, as indicated 

in Figure 7 (oxidation induction time is a measure 

of the remaining antioxidants). The oxidation 

induction time for unexposed resin is 95 minutes. 

This work is expected to lead to a relationship 

between the antioxidant concentration and the 

polymer lifetime. 

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4 8 12 16 

CaCO3 (g/m2 ) 

1 

2 

3 

4 

0 

Time (hours) 

Fig. 8. Quantities of CaCO3 on polypropylene 

(filled squares) and copper (open triangles) as a 

function of exposure time, for (a) the tap water 

test, and (b) the distilled-water, single-species test. 

3.3 Combined PV/Thermal Systems 

PV/thermal (PV/T) simulation models have been 

developed for both liquid fin-tube and back-pass 

air PV/T systems. Six different models were 

produced, allowing variations in the back-plane 

boundary conditions and addition of a transparent 

cover that tends to thermally isolate the absorbed 

radiation from the ambient sink (see Figure 9 for 

examples). The models are being used in 

conjunction with building modeling to determine 

the extent of overlap between building loads and 

PV/T energy delivery. Early results indicate that 

there is good coincidence of available thermal 

energy with the summer cooling load in many 

climates, but poor overlap with heating loads. 

Under BTP funding, SunEarth previously 

developed and tested a prototype two-stage airbased PV/T system, as shown in Figure 10. The 

system draws outdoor air under the PV, picking up 

waste heat. The air then passes through a glazed, 

selective-surfaced air-heater section, increasing 

the outlet temperature. In this system, the hot air is 

then used for water heating with an air-to-liquid 

heat exchanger, and for space heating with direct 

injection into the air distribution system. Six 

systems have been installed in the field and are 

being monitored. The current system has been 

submitted for SRCC certification. A subcontract 

funded work on the development of the balance of 

system, including the mechanical ducting and 

dampers and the control system. 

With transparent cover 

Unglazed/no cover 

Fig. 9. Schematic air-based PV/thermal models, 

with and without a transparent front cover. 

3.4 Industry Support 

Under SAI, cities have expressed interest in 

school and municipal pool systems. Pool systems 

are a very cost-effective solar technology, with 

LCOE less than 1¢/kWh. Cities see this as a winwin situation but want assurance as to 

performance. SNL developed a Web-based 

calculator to estimate the energy savings for the 

pool system. Similarly, cities and energy-aware 

builders need to understand the benefits of solar 

water heating incentive programs. To serve this 

need, NREL developed a generic calculator for 

common SWH which is similar to PVWatts, the 

familiar PV calculator. The tool allows user input 

for system loads, location (the Typical 

Meteorological Year [TMY]2 site), system type, 

and system characteristics (e.g., area, storage 

volume, orientation, collector parameters). The 

calculator also facilitates parametrics for most user 

inputs. 

The U.S. solar industry has encountered welding 

and corrosion issues that have been investigated 

at SNL. Solutions for these and other problems 

leverage the expertise available at SNL that has 

been developed through U.S. Department of 

Defense funding, which literally dwarfs any solar 

funding. Industry also continues to encounter 

rating and certification issues for solar collectors 

and systems. NREL led efforts to determine 

methods to extrapolate test data to different sizes 

Solar Thermal R&D

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216
 

 

 

 

of the same collector model and determine rating 

conditions. Ongoing efforts include fairness 

concerns arising from differing test standards for 

glazed and unglazed collectors, which suggest a 

bias toward unglazed systems as currently used in 

SRCC procedures. 

Fig. 10. A 3-kW PV system (bottom section of the 

system) with air heaters (top section). 

4. Planned FY 2008 Activities 

•	 Issue a request for proposals (RFP) for the 

development of cold-climate SWH, and make 

at least five awards 

•	 Identify preferred PV/T and triple-play solar 

thermal systems, and establish cost goals 

•	 Begin the development of a prototype airbased PV/T system with desiccant-based 

space cooling 

•	 Continue to provide industry support. 

Lower cost thermal systems are essential to attain 

savings beyond the 50% level in Building America 

homes, and they are critical for attaining costeffective ZEH. If FY 2008 funding permits, an RFP 

will be issued for the conceptual development of 

low-cost cold-climate systems. At least five awards 

at the $100K level are expected. The projects will 

follow a stage-gate process similar to the 

successful mild-climate SWH development, 

starting with conceptual development that results 

in the product’s predicted LCOE and identifies 

significant issues. After the conceptual 

development (~1 year), projects will be fed into the 

second stage (prototype development) if they 

meet the requisite savings levels and don’t present 

costly R&D issues. The low-cost work on mildclimate systems will be phased out, with minor 

investment in support of ongoing field studies and 

manufacturing improvements. 

Development of PV/T and triple-play models for 

use in optimization studies will continue. Both 

performance and cost models are needed to 

compare the solar-driven systems with alternative 

technologies fairly. Modeling of PV/T cooling will 

begin in FY 2008. Savings from heat-only PV/T 

models will be determined in conjunction with 

building modeling to give the timing and 

magnitude of the loads. Cost goals for heat-only 

PV/T will be derived through this analysis. 

The University of Minnesota will continue work on 

polymer heat exchanger lifetime and scale rates. 

The storage and heat exchanger task will 

concentrate on how to manage thermal storage 

with the annual-storage desiccant-based systems. 

In addition, a Web-based tool for estimating SWH 

and combi-system performance will be developed 

that will allow the user to pick generic systems, 

generic systems with specific SRCC-listed 

collectors, or specific SRCC-listed SWH systems. 

NREL staff leading and serving on the standards 

committee will continue to resolve technical issues 

in rating and certification that are arising in the 

rapidly expanding U.S. solar thermal industry 

5. FY 2007 Special Recognitions and Awards 

•	 University of Minnesota Professor Jane 

Davidson received the prestigious Charles 

Abbot award from the American Solar Energy 

Society. 

•	 NREL’s Dr. Jay Burch was elected as a fellow 

of the American Solar Energy Society. 

6. Major FY 2007 Publications 

J. Davidson, S. Mantell, and L. Francis, “Thermal 

and Material Characterization of Immersed Heat 

Exchangers for Solar Domestic Hot Water,” 

Advances in Solar Energy, D.Y. Goswami, ed., 

American Solar Energy Society, vol. 17, 99-129 

(2007). 

Journal Papers 

•	 Y. Su and J. Davidson, “Transient Natural 

Convection Heat Transfer Correlations for 

Tube Bundles Immersed in a Thermal 

Storage,” ASME J. of Solar Energy 

Engineering, 129, 210-214 (2007). 

•	 F. Kulacki, J. Davidson, and M. Hebert, “On 

the Effectiveness of Baffles in Indirect Solar 

Storage Systems,” ASME J. of Solar Energy 

Engineering, 129, 494-498 (2007). 

•	 Y. Su and J. Davidson, “Multi-Zone Porous 

Medium Model of the Thermal and Fluid 

Processes during Discharge of an Inclined 

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Rectangular Storage Vessel via an Immersed 

Tube Bundle,” ASME J. of Solar Energy 

Engineering, 129, 449-457 (2007). 

Conference Papers 

•	 J. Burch and C. Christensen, “Toward 

Development of an Algorithm for Mains Water 

Temperature,” Proc. American Solar Energy 

Society, Cleveland, OH, June (2007). 

•	 J. Burch, G. Shoukas, M. Brandemuhl, and M. 

Krarti, “Test and Rate Methods for 

Thermosiphon Solar Water Heaters,” Proc. 

American Solar Energy Society, Cleveland, 

OH, June (2007). 

•	 J. Haltiwanger and J. Davidson, “Temperature 

and Flow in a Cylindrical Storage Tank with a 

Baffled Heat Exchanger: Experiments,” Solar 

2007, Annual Conference of the American 

Solar Energy Society, Cleveland (2007). 

•	 Y. Su and J. Davidson, “Discharge of Thermal 

Storage Tanks via Immersed Baffled Heat 

Exchangers: Numerical Model of Flow and 

Temperature Fields,” ASME Energy 

Sustainability, Long Beach, CA, June (2007). 

• G. Jorgensen, “Durability Testing of Polymer 

Materials Used in Solar Thermal Systems,” 

Society Of Plastics Engineers, Engineering 

Properties and Structure Division, Annual 

Technical Conference 2007 (SPE/ANTEC 

2007), Cincinnati, OH, May 6-10, 2007. 

Reports and Theses 

•	 P. Denholm, ”The Technical Potential of Solar 

Water Heating to Reduce Fossil Fuel Use and 

Greenhouse Gas Emissions in the United 

States,” NREL/TP 640-41157, Golden, CO: 

NREL, March (2007). 

•	 J. Haltiwanger, “Analysis of a Cylindrical Baffle 

in Energy Discharge of a Vertical Solar 

Storage Tank with an Immersed Heat 

Exchanger,” M.S. Thesis, University of 

Minnesota, Mechanical Engineering 

Department, Minneapolis, MN, October 

(2007). 

•	 V. Kathare, “Natural Convection in WaterSaturated Metal Foam,” M.S. Thesis, 

University of Minnesota, Mechanical 

Engineering Department, Minneapolis, MN , 

September (2007). 

•	 D. Menicucci, and A. Mahoney, “Copper 

Corrosion and Its Relationship to Solar 

Collectors: A Compendium,” SAND2007-4347, 

Albuquerque, NM: SNL, July (2007). 

• T. Merrigan, Solar Heating Strategic Plan 

(Review Draft), Golden, CO: NREL, June 22 

(2007). 

•	 U.S. Department of Energy, Solar Water 

Heating: Potential Energy Savings, Market 

Barriers, and Strategies for Wider 

Deployment, Report to Congress, Washington, 

D.C., (2007). 

•	 Z. Wu, “Scale Formation on Polypropylene 

and Copper Tubes,” Ph.D. Thesis, University 

of Minnesota, Mechanical Engineering 

Department, Minneapolis, MN, November 

(2007). 

7. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 

2007 

($K) 

Cost 

Share 

($K) 

Davis Energy Group 

Eric Lee 

Davis, CA 

elee@davisenergy.com 

Refine glazing and heat 

exchanger, field trials 135 30 

FAFCO, Inc 

Mike Rubio 

Chico, CA 

mrubio@fafco.com 

Refine new designs, test 

prototypes, field trials 135 138 

University of Minnesota 

Jane Davidson 

Minneapolis, MN 

jhd@me.umn.edu 

Stratification, pipe materials 

testing, and scaling rates 150 4001 

Thermal Energy System 

Specialists, Inc. 

Jeff Thornton 

Madison, WI 

thornton@tess-inc.com 

Develop TRNSYS and TRNSED 

models in support of industry 

teams 

50 0 

SunEarth, Inc. 

Josh Plaisted 

Fontana, CA 

jplaisted@sunearthinc.com 

Phase 2B development of 

PV/thermal system 2002 50 

1

 High degree of co-funding through university and state grants devoted to solar thermal. 2

 Phase 1 and 2A funded through the DOE Building Technologies Program. 

Solar Thermal R&D

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

Hybrid Solar Lighting 

Performing Organization: Oak Ridge National Laboratory (ORNL) 

Key Technical Contacts:	 Melissa Lapsa (ORNL), 865-576-8620, lapsamv@ornl.gov 

Curt Maxey (ORNL), 865-576-7114, maxeylc@ornl.gov 

DOE HQ Technology Manager: Robert Hassett, 202-586-8163, robert.hassett@ee.doe.gov 

FY 2007 Budgets:	 $2,000K 

Objectives 

•	 Evaluate the performance of the Sunlight Inside Initiative beta test sites across the United States. 

•	 Identify technical issues and research solutions. 

•	 Complete third-party assessment of the hybrid solar lighting (HSL) market. 

Accomplishments 

•	 Prepared a summary of the Sunlight Inside Initiative beta test site results. 

•	 Prepared a summary of technical issues and research solutions; final report is due in fiscal year 

(FY) 2008. 

•	 Completed a third-party market assessment of HSL. 

Future Directions 

Because of the late arrival of FY 2007 funds, FY 2008 activities will target the completion of the FY 2007 

scope of work. 

1. Introduction 

In the United States, artificial lighting represents 

the single largest component of electricity use in 

commercial buildings, costing building owners 

nearly $17 billion a year. Despite the high 

consumption of energy and the continued demand 

by occupants for more natural lighting, natural 

lighting from conventional options, such as 

skylights and windows, illuminates only a tiny 

fraction of the available commercial space. This 

limited use of natural lighting is a result of the 

architectural limitations of skylights and windows 

and the uncontrollable nature of sunlight itself 

(e.g., intensity fluctuations, glare, and unwanted 

heating). A significant market exists for a natural 

lighting product that can offer the benefits of 

natural light with all of the conveniences and 

control of an artificial lighting system. 

Hybrid solar lighting (HSL) technology meets this 

previously unmet need and has the potential to 

provide a product with an economic payback of 

three to four years for commercial buildings in the 

Sunbelt regions of the world. In the U.S. Sunbelt 

alone, 20 billion square feet of commercial space 

meet the requirements for implementation of an 

HSL system. Each year, this amount of applicable 

space grows by 600 million square feet of new 

construction. 

The commercialization of HSL technology will 

focus initially on a small subset of retailers 

representing jewelry, furniture, and apparel 

markets. This niche market of early adopters is 

expected to increase sales volumes of HSL 

technology, permitting cost reductions through 

economies of scale. With system price reductions, 

we anticipate that greater penetration into this 

niche market and the larger commercial building 

market (including office buildings) will occur. Fullspectrum solar energy systems, such as HSL, 

provide a new and realistic opportunity for wideranging energy, environmental, and economic 

benefits. Their development is directly in line with 

the mission of the U.S. Department of Energy 

(DOE) Solar Energy Technologies Program to 

improve America’s security, environmental quality, 

and economic prosperity through public-private 

partnerships that bring reliable and affordable 

solar energy technologies to the marketplace. 

The advantages of HSL include the following: 

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Solar Thermal R&D

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•	 Small and minimal roof penetrations, reducing 

the potential for leaks. 

•	 Separation of the infrared (IR) and ultraviolet 

(UV) energy in sunlight from the visible light, to 

prevent the transmission of IR and UV light 

into buildings. Heating, ventilation, and airconditioning (HVAC) loads are thus reduced 

by 5% to 10% in comparison to those of 

electric lighting systems. 

•	 Minimal use of precious plenum space—the 

area between the roof and the drop ceiling— 

so there is little competition with other building 

services, such as HVAC ducts, sprinkler 

systems, and electrical conduits. 

•	 Versatility of use for both direct ambient 

lighting (as in skylights) and for indirect task 

and accent lighting applications. 

• Ease of incorporation into existing building 

designs (for retrofit markets). Optical fibers 

can also be rerouted to different locations as 

lighting needs change. By intentionally 

misaligning the solar collector from the sun, 

occupants can even dim or curtail distributed 

sunlight. 

2. Technical Approach 

FY 2007 research efforts focused on two major 

areas: system reliability improvement and 

reduction of the cost of goods sold. 

2.1 System Reliability 

Early HSL prototypes appeared to be reliable, with 

respect to their ability to handle the thermal load of 

the concentrated solar energy. However, as the 

manufacturing processes for the HSL primary 

mirrors improved, the level of concentrated energy 

increased and ultimately caused the reliability of 

the systems to become severely compromised. In 

FY 2006, multiple instances of damaged fiber 

bundles in fielded units indicated a critical need for 

better thermal characterization and mitigation in 

the HSL system design. 

A series of round-robin tests was planned, and 

tests were conducted at four sites: Oak Ridge 

National Laboratory (ORNL), Utah State 

University, San Diego State University, and the 

University of Nevada at Las Vegas. Eight identical 

fiber optic receiver assemblies (including a 

receiver housing, hot mirror, mixing rod, and short 

fiber optic bundle) were constructed for use in the 

round-robin tests. Each of the bundles was to be 

tested for up to two weeks at each of the four 

locations. As a part of the preparation process for 

the round-robin tests, a test apparatus was 

developed to characterize the thermal absorption 

of the face of the fiber optic bundles. This enabled 

the bundles to be characterized before the test 

units were assembled. 

The round-robin tests began in early July 2007, 

when each of the four systems were fitted with the 

highest quality primary mirrors available. In the 

first month of testing, preliminary results began to 

show a damage pattern that suggested a probable 

cause for the system failures that were occurring 

in the field. Small pits in the face of the plastic 

mixing rod developed as a first sign of this 

damage. With continued exposure, the pits 

increased in size and number. Eventually 

(sometimes after several days of progressive 

degeneration), some of the units failed entirely. 

These results were essential to understanding the 

failure mechanism and mitigating the thermal 

stress. 

Once the failure mechanism had been identified, 

the next step was to identify a safe operating 

condition in which the units could continue to 

operate. The HSL systems at the four sites were 

defocused to varying degrees, as the tests 

continued, to try to identify a safe operating level 

of concentration. Ultimately, the units were all 

operated in a defocused condition that reduced 

the level of concentrated light by about 30%, and 

this appeared to be a reliable mode of operation. 

At the same time, efforts began to be directed 

toward developing an improved hot mirror to 

protect the mixing rod, as well as an improved 

cold-mirror coating for the elliptical secondary 

mirror. Field tests of the two alternative designs 

were conducted late in CY 2007; however, the 

tests indicated that there had been no 

improvement in performance over that of the 

previous designs. 

Since it appeared that the heating in the HSL units 

could not be eliminated at the source, it appeared 

that efforts would have to be directed toward 

extraction of the heat. Late in CY 2007, outside 

consultants were called in to assist with thermal 

management in the HSL receiver design. Twodimensional thermal models were constructed that 

corroborated many of the experimental results. 

These models are currently being used in the 

development of an alternative receiver design that 

will incorporate improvements in materials and 

airflow. The improvements are expected to 

Solar Thermal R&D

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220
 

eliminate the catastrophic failures that have been 

experienced in the existing receiver designs. 

2.2 Reduction of the Cost of Goods Sold 

Cost reduction has focused on two areas: 

manufacturing processes and system design. The 

development of the bundle characterization 

system that was used to characterize the bundles 

for the round-robin tests has become an important 

tool for quality assurance of full-system bundles. 

This has been valuable in the development of 

manufacturing processes that are resulting in 

bundles that are more uniform and higher in 

overall quality. Bundle manufacturing costs (one of 

the largest HSL production costs) have been 

reduced through processes that take less time and 

achieve more consistent results. Consequently, 

the costs associated with rework have been 

significantly reduced. 

The overall cost of HSL systems will drop 

dramatically in CY 2008 as a result of the 

development of an improved tracker mechanism. 

The details of the redesign are not available for 

release at this time, but it will be a significantly 

different design that is expected to cost less, be 

more reliable, and greatly reduce installation costs 

by eliminating the need for manual calibration 

during setup. 

Agreement Title FY 2007 

Budget ($K) 

Identify HSL technical issues 

and research solutions 1,925 

Conduct independent market 

assessment 

75 

3. Results and Accomplishments 

3.1 Prepared Summary of Sunlight Inside 

Initiative Beta Test Site Results 

Field-testing was conducted at the HSL beta sites 

across the United States as part of the Sunlight 

Inside Initiative (see Figures 1–4). Past 

evaluations of the HSL fiber optic receiver showed 

that heating of the receiver was occurring as a 

result of optical absorption of the receiver’s 

subcomponents. This heating was determined to 

be responsible for the failure of several test units 

being field-tested as part of a nationwide field trial 

program. 

- HSL site not used in 

field trial test field trial test 

- HSL site used for 

Fig. 1. U.S. locations of Sunlight Inside Initiative 

beta sites. 

Honolulu, HI 

San Diego, CA 

McKinney, TX 

Las Vegas, 

NV 

Knoxville, TN Chattanooga, 

TN 

Sacramento, 

CA 

Fredericksburg, 

VA 

St. Petersburg, 

FL 

Oceanside, 

NY 

Fig. 2. An HSL system is installed in the 

electronics area of a Texas Wal-Mart, one of the 

beta sites of the Sunlight Inside Initiative. The HSL 

is incorporated into spot lighting to highlight 

various products in the home entertainment area. 

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Fig. 3. Rooftop HSL system at a Texas Wal-Mart, 

one of the Sunlight Inside Initiative beta site 

locations across the United States. 

3.2 Prepared Summary of Technical Issues and 

Research Solutions (final report due in FY 

2008) 

An experimental effort was developed in early 

2007 to evaluate the heating and failure 

mechanisms present in the current receiver 

design. The intent was to ultimately mitigate the 

heating to a level that would support the long-term 

operation of the receivers at maximum input flux. 

A defocused configuration of the solar collector 

was tested and verified. Reconfiguration of 

existing field-trial systems has been completed, 

and the field-trial fiber receivers are no longer 

failing. To reach maximum flux, an “optical 

solution” was pursued that, although it did yield 

some improvements, was not ultimately successful 

at significantly reducing the heat being produced 

by the receiver to levels that would ensure 

survivability at maximum flux. As such, it is 

recommended that a “thermal solution” be pursued 

to dissipate the heat build-up that is occurring 

within the receiver. FY 2008 activities are focused 

on redesigning the optical receiver housing, 

conducting field testing, and preparing the final 

report. 

Fig. 4. Flexible 127-strand fiber optic bundle from 

the HSL system. 

3.3 Completed a Third-Party Market Assessment 

of HSL 

A third-party market potential analysis was 

conducted by Antares, Inc., to gauge the size and 

characteristics of the commercial market for the 

technology. The assessment identified the gross 

potential market for HSL as follows: 

•	 Core building areas (enclosed areas up to 

within 10 ft of the building exterior) 

•	 Top two floors only (distribution constraints) 

•	 Target facility primary uses: education, food 

sales, health care, lodging, retail, office, and 

public assembly 

•	 U.S. potential market in 2008 (units installed): 

new construction = 356,000 units/year; retrofit 

= 1.17 million units/year. 

4. Planned FY 2008 Activities 

Because of the late arrival of FY 2007 funds, FY 

2008 activities will target the completion of the FY 

2007 scope of work. 

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5. FY 2007 Special Recognition, Awards, and 

Patents 

Awards: 

On behalf of the ORNL solar team, Melissa Lapsa 

and David Beshears accepted the Excellence in 

Technology Transfer Award from the Southeastern 

Region of the Federal Laboratory Consortium 

(FLC), which was presented at the Southeast 

Regional Meeting, held in conjunction with the 

Midwest Region technology transfer conference in 

Nashville, Tennessee, October 25–27, 2006. 

Melissa Lapsa, ORNL Solar Technologies 

Program Manager, received notification that 

“Hybrid Solar Lighting” had been selected as a 

national winner of the 2007 Award for Excellence 

in Technology Transfer by the FLC. The award 

recognizes laboratory employees who have 

accomplished outstanding work in the process of 

transferring a technology developed by a federal 

laboratory to the commercial marketplace. 

Patent: 

U.S. Patent No. 7,231,128 B2 for Hybrid Solar 

Lighting Systems and Components was issued to 

Jeff Muhs, Duncan Earl, Dave Beshears, Curt 

Maxey, John Jordan, and Randall Lind on June 12 

(2007). 

Press Coverage: 

“Solar experts gathering at ORNL for summit,” The 

Oak Ridger, Sept. 14 (2007). (Also appeared in 

the Energy Digital, All American Patriots, RxPG 

News, U.S. Fed News, and First Science News.) 

“ORNL's Hybrid Solar Lighting Wins National 

Technology Transfer Award,” (Azom.com, The A 

to Z of Materials), June (2007). 

“Hybrid Solar Lighting Promises 50% Efficiency,” 

Sara Parker, Renewable Energy World.Com, June 

14, 2007. 

“Experts Say Buildings Can Go Green Now,” Earth 

and Sky podcast in the series, "A Clear Voice for 

Science," May 21 (2007). www.earthsky.org/clearvoices/51361/marilyn-brown-on-green-building. 

“Here Comes the Sun,” Sara C. Shoemaker, 

Business Tennessee, May (2007). 

“Hybrid solar lighting earns national technology 

transfer award,” First Science News, June (2007). 

“East Tennessee cleantech companies cultivate 

environmentally conscious market sector,” Andrew 

Eder, edera@knews.com, April 22 (2007). 

“Sunlight Directs Hybrid Solar Lighting: Fiberoptic 

Brilliance,” Popular Mechanics, March (2007). 

“Let there be light, optical cables included,” CNET 

Networks, Inc., March (2007). 

“An Even Smarter Lighting System,” Buildings, 

December (2006). 

“DOE-Funded Research Projects Win 41 R&D 100 

Awards for 2006” U.S. Department of Energy 

News, Oct. 19 (2006). 

“The sun in a hose,” Star Tribune, Minneapolis– 

St. Paul, Minn., Oct. 15 (2006). 

“Hybrid Solar Lighting Technology ... Soon to 

shine on the commercial scene!” Electrical Line 

Magazine, Vol. 12, No. 5, September/October 

(2006). 

6. Major FY 2007 Publications 

D. L. Beshears et al., “Solar Energy, Collected, 

Concentrated, Transported and Distributed As 

Light with No Energy Conversion via a Hybrid 

Solar Lighting System.” Proceedings of Solar 

2007, American Solar Energy Society, Cleveland, 

Ohio, July 7–12 (2007). 

Federal Energy Management Program, “Hybrid 

Solar Lighting Illuminates Energy Savings for 

Government Facilities,” FEMP Technology Focus, 

Publication Number DOE/EE-0315, April (2007). 

www.eere.energy.gov/femp/ 

M. Lapsa, D. Beshears, L. Maxey, and C. Ward, 

“Direct Use of Solar Energy for Lighting – Results 

of the Hybrid Solar Lighting Field Trial Program,” 

Proceedings of Solar 2007, American Solar 

Energy Society, Cleveland, Ohio, July 7–12 

(2007). 

M. V. Lapsa, L. C. Maxey, D. D. Earl, D. L. 

Beshears, C. D. Ward, and J. E. Parks, “Hybrid 

Solar Lighting Provides Energy Savings and 

Reduces Waste Heat,” Journal of Energy 

Engineering, Vol. 104, No. 4, 7-20 (2007). 

L. C. Maxey, “Flexible Sunlight—The History and 

Progress of Hybrid Solar Lighting,” chapter to be 

223

Solar Thermal R&D

Solar Water Heating Systems Development
 

 

published in 2008 in Emerging Environmental Lighting System,” ASME Energy Sustainability 

Technologies, by V. Shah, submitted June (2007). 2007 Conference, Long Beach, California, June 

27–30 (2007). 

L. C. Maxey et al., “Spectral Transmission of a 

Solar Collector and Fiber Optic Distribution Hybrid 

7. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal 

Investigator 

Location/e-mail Description/Title of Research 

Activity 

FY 2007 

($K) 

Cost 

Share ($K) 

Sunlight Direct, LLC/ 

John Morris 

Oak Ridge, TN 

morrisjd@sunlight-direct.com 

Collaborative work on HSL for 

fabrication of improved system 

components 

736 250 

Antares Group, Inc./ 

Ed Gray 

Landover, MD 

edgray@antaresgroupinc.com Market assessment and report 65 0 

University of 

Tennessee/ 

Tony Gehl and 

Philip Boudreaux 

(Post-doctoral) 

Knoxville, TN 

tonygehl@gmail.com Research support 58 0 

Solar Thermal R&D

Solar Water Heating Systems Development

224
 

 

Systems Integration and Coordination 

Energy efficiency and renewable energy will mean a stronger economy, a cleaner environment, 

and greater energy independence for the United States. Working with a wide array of state, 

community, industry, and university partners, the U.S. Department of Energy’s Office of Energy 

Efficiency and Renewable Energy (EERE) invests in a diverse portfolio of energy technologies. 

These include solar-related research, development, and deployment projects that crosscut with, 

and complement, the objectives of the DOE Solar Program. 

The National Center for Photovoltaics (NCPV), headquartered at the National Renewable Energy 

Laboratory (NREL) in Golden, Colorado, provides overall coordination of the PV Subprogram at 

the request of DOE. NREL and Sandia National Laboratories (SNL) in Albuquerque, New Mexico, 

are partners in the NCPV, and provide the management oversight for the respective projects in 

their laboratories, as well as management support for the NCPV. The Concentrating Solar Power 

(CSP) Subprogram is managed collaboratively between SNL and NREL in the virtual entity 

referred to as Sun♦Lab. NREL, SNL, and Oak Ridge National Laboratory (ORNL) in Oak Ridge, 

Tennessee, jointly participate in managing the Solar Heating and Lighting Subprogram. 

Management activities include analysis, administration, budget control, reporting, and integration 

of programs, including oversight of staff, equipment, and facilities at NREL, SNL, and ORNL. The 

management team develops inputs for new program initiatives, conducts review meetings at the 

request of DOE, and provides oversight for communications, outreach, and cross-cutting analysis 

activities. 

Small Business Innovation Research (SBIR) is a highly competitive program that encourages 

small businesses to explore their technological potential and provides the incentive to profit from 

its commercialization. By including qualified small businesses in the nation's R&D arena, hightech innovation is stimulated and the United States gains entrepreneurial spirit as it meets its 

specific research and development needs. Each year, ten federal departments and agencies 

(including DOE) are required by the SBIR Program to reserve a portion of their R&D funds for 

award to small, U.S.-owned businesses. 

Some significant accomplishments in FY 2007 are listed below. 

Communications 

•	 Maintained, expanded, and/or developed about 12 Web sites. 

•	 Supported efforts for the publication of about 350 technical publications. 

•	 Completed all preparations for the 2007 Solar Decathlon (the event occurred in FY08). 

International Activities 

•	 Supported participation in both International Energy Agency (IEA) Task 9, “Coordination 

of Renewable Energy Training and Certification Activities,” and IEA Task 10, “Urban 

Scale PV Applications." 

Small Business Innovation Research 

• Adapted metallurgical techniques for purifying silicon to produce a cheaper grade of 

silicon for PV and developed a reusable crucible for Silicon ingot casting for PV. 

225 Systems Integration and Coordination
Systems Integration and Coordination 226
 

 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

Communications and Outreach 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

 DOE Golden Field Office (DOE/GO) 

Key Technical Contacts:	 Ruby Nahan (NREL), 303-384-7401, ruby_nahan@nrel.gov 

 Don Gwinner (NREL), 303-384-6570, don_gwinner@nrel.gov 

 Susan Moon (NREL), 303-384-6631, susan_moon@nrel.gov 

DOE HQ Technology Manager: Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2007 Budgets:	 $545K (NREL), $75K (SNL) 

Objectives 

•	 Find innovative ways to reach critical audiences in a timely and accurate manner to improve 

business performance and help the Solar Energy Technologies Program (SETP) realize its vision, 

mission, and goals. 

•	 Inform and persuade audiences, move them to action, and help overcome barriers for particular 

technologies and applications. 

•	 Unify the outreach efforts of the Solar Program so that communications and knowledge transfer 

emphasize all, rather than individual solar technologies, leading to understanding, collaboration, 

and partnership to advance solar energy technologies. 

•	 Provide targeted communications support to ensure the successful launch of all activities within 

the Solar America Initiative (SAI)—including both R&D and market transformation. 

•	 Produce and maintain documents and Web sites to support the core business activities of SETP. 

Accomplishments 

•	 Completed core program and cross-cutting communications support for SETP. 

•	 Provided critical and timely support to SETP for the SAI, including both R&D and market 

transformation activities. 

•	 Maintained, expanded, and/or developed about 12 Web sites. 

•	 Supported efforts for the publication of about 350 technical publications. 

•	 Employed visual display and design expertise, creating products such as 3-D animations, 

posters, and displays for a variety of products. 

•	 Created and/or staffed several exhibits. 

•	 Completed all preparations for the 2007 Solar Decathlon (the event occurred in FY08). See the 

Solar Decathlon report for more information. 

Future Directions 

•	 Develop a plan for communications activities, associated with all SAI market transformation 

activities. 

•	 Work in conjunction with the U.S. Department of Energy’s (DOE) Public Affairs office, Office of 

Energy Efficiency and Renewable Energy’s (EERE’s) Technology Advancement Office, and 

Golden Field Office (GO) to create branding guidelines for SAI market transformation partners. 

•	 In addition to conducting operations and maintenance for all EERE solar Web sites: 

o	 Create a robust concentrating solar power (CSP) Web presence 

o	 Develop a plan for redesigning the sites to better meet the needs of critical SAI 

audiences. 

•	 Conduct a needs assessment and develop an appropriate centralized information resource to 

answer the increased volume of inquiries about solar. 

•	 Conduct all planning activities for the communications and outreach tasks for Solar Decathlon 

2009. 

227 Systems Integration and Coordination
1. Introduction 

The Solar Communications Team supports the 

communications and outreach needs of many 

elements of the Solar Energy Technologies 

Program (SETP). These include the Solar America 

Initiative (SAI), the National Center for 

Photovoltaics (NCPV), and concentrating solar 

power (CSP) and solar heating (SH) activities at 

the National Renewable Energy Laboratory 

(NREL) and Sandia National Laboratories (SNL). If 

the U.S. Department of Energy’s (DOE’s) solar 

program is to be successful in its mission to 

accelerate market acceptance of solar 

technologies, it must communicate accurate and 

timely information to target audiences such as the 

solar industry, universities, nonprofit groups, public 

utilities, the buildings industry, consumers, and 

federal, state, and local governments. The Solar 

Communications Team is made up of several 

professionals from NREL and SNL. The team’s 

accomplishments in its support of SETP’s mission 

in 2007 include these: 

•	 Supported SETP management by producing 

reports, newsletters, and strategic planning 

documents 

•	 Represented the program’s mission and 

accomplishments through Web sites, 

publications, and conference exhibiting 

•	 Provided critical support to SAI through the 

development of print materials, redesigning 

the Web site, and supporting the Golden Field 

Office (GFO) and DOE headquarters in award 

selections and media events for award 

announcements 

•	 Described technical accomplishments through 

conference papers, presentations, and 

posters; technical reports; journal articles; 

brochures; fact sheets; exhibits; displays; Web 

sites; CDs; and animated videos 

•	 Managed all nonmedia communications for 

the 2007 Solar Decathlon. 

The Solar Communications Team is a complete 

communications and design group with a wide 

variety of expertise: 

•	 Strategic communications and outreach 

planning, including audience analysis, 

branding, program plans and assessments, 

marketing, and questionnaires 

•	 Writing and editing, including technical and 

marketing products, speeches and 

presentations, journal and magazine articles, 

contractual reports, and Web sites 

•	 Graphic design (print and electronic) 

•	 Multimedia and animation development 

•	 Web site development, including needs 

assessment, content development and 

optimization, information architecture, design, 

development, database applications, virtual 

reality, blogs, forums, RSS feeds, new media, 

and statistical analysis. 

Agreement Title FY 2007 

Budget ($K)* 

Core Program Support $150K (NREL, 

$50K (SNL) 

Cross-Cutting Communications $140K (NREL) 

Solar America Cities Partnerships $100K (NREL) 

State Strategic Partnerships $100K (NREL) 

Utility Strategic Partnerships $100K (NREL) 

* Note: Communications and Outreach activities span 

many other SETP activities. Accomplishments 

discussed cover more activities than those to which 

these budgets were committed. 

2. Communications Approach 

The Solar Communications Team takes a 

comprehensive approach to its activities. We 

identify and respond to communications needs by: 

•	 Identifying effective communication objectives 

and strategies 

•	 Analyzing and understanding key target 

audiences and their perceptions of solar 

technologies 

•	 Developing audience-specific messages 

•	 Creating communications products to reinforce 

objectives and effectively deliver audiencespecific messages. 

This process of planning and analysis, developing 

and producing, and effectively transferring 

knowledge is applied to all communications 

activities. The Solar Communications Team’s 

activities fall within three primary areas: 

•	 Core Program Support and Cross-Cutting 

Communications 

•	 Solar America Initiative R&D and market 

transformation activities, including State 

Strategic, Utility Strategic, and Solar America 

Cities partnerships 

•	 Additional SETP and NCPV R&D activities 

described elsewhere in this report that do not 

discuss communications work specifically. 

Note: the FY 2007 budgets for these additional 

activities are not reflected here. 

Systems Integration and Coordination 228
 

 

3. Results and Accomplishments 

Key results and accomplishments are summarized 

under the three major activities listed in Section 2, 

Communications Approach. 

Fig. 1. The Solar Communications Team provided 

media kits for Energy Secretary Samuel Bodman’s 

announcement of the Solar America Cities awards 

in New York. 

3.1 Core Program Support and Cross-Cutting 

Communications 

•	 Completed the DOE Solar Energy 

Technologies Program Annual Report 2006. 

•	 Prepared and implemented a comprehensive 

Web maintenance plan for the EERE/SETP 

Web site, including analysis of common 

Webmaster inquiries to streamline the 

response process. We also contributed 

ongoing updates to the EERE News and 

Events databases with solar-relevant content. 

•	 Exhibited, on behalf of the SETP, at the 

International Builders' Show, which had 

110,000+ visitors. The Information Resource 

section was also completed on the 

EERE/SETP Web site in time for the show, 

where we handed out business cards with the 

URL for this section. 

•	 Attended and supported the DOE/EERE Solar 

Program Annual Review Meeting in Denver, 

Colorado. We spoke with attendees about SAI 

during poster sessions and produced 

electronic proceedings from the meeting. 

•	 Managed weekly conference calls with SETP 

managers to discuss strategic 

communications planning to ensure that 

effective communications strategies are in 

place, to reduce duplication of effort, and to 

clarify the roles and responsibilities of all 

program participants. 

•	 Responded to a variety of miscellaneous 

communication requests from DOE 

headquarters: 

o	 As a benefit to DOE's sponsorship of the 

American Solar Energy Society (ASES) 

National Solar Home Tour, we designed 

an ad for Solar Today magazine 

o	 At the request of DOE EERE Assistant 

Secretary Alexander Karsner and Tom 

Kimbis, we posted a DOE best practices 

document and coordinated with progress 

alert feeds. 

o	 We provided Energy Secretary Bodman's 

office with talking points about 

International Energy Agency solar work. 

•	 We contributed to or edited and produced 

three reports for Congress: 

o	 The Effect of Polysilicon Market 

Conditions on the PV Market 

o	 A CSP Energy Policy Act (EPAct) report 

o	 A solar heating EPAct report 

•	 We supported the development of the first 

SETP newsletter by providing content, editing, 

and posting. We continue to support 

subsequent issues. 

Fig. 2. The Solar Communications Team 

produced a variety of SETP documents in FY 

2007, like the report to Congress shown above. 

3.2 SAI R&D and Market Transformation 

•	 Designed a new solar program exhibit that 

emphasizes SAI and represented the program 

at two solar conferences: Solar 2007 (the 

annual ASES conference) and Solar Power 

229 Systems Integration and Coordination
 

 

 

2007 (the annual Solar Electric Power 

Association [SEPA] conference). We also 

developed a complementary sponsor banner 

and conference bag insert to promote SAI to 

Solar 2007 Conference attendees. At each 

conference, we spoke with conference 

attendees about SETP and SAI and directed 

them to the activities and resources 

appropriate to their interests. 

•	 Participated in a review of proposals for the 

SAI State Technical Outreach, Utility 

Technical Outreach, and Solar America Cities 

partnerships and participated in two 2-day 

merit reviews. 

•	 Participated in the Green Power Marketing 

Conference, in support of Utility Technical 

Outreach activities. 

•	 Redesigned the SAI Web site, analyzing 

content by task and restructuring the 

information architecture to include project 

pages, so activities can be tracked and 

information kept current. 

•	 Prepared and implemented a comprehensive 

Web site maintenance plan for the SAI site. 

•	 Completed and published a number of print 

and electronic products to announce and 

publicize various SAI activities: 

o	 Announced the State & Utility Technical 

Outreach on the SAI Web site 

o	 Added University and Exploratory 

Research Workshop content to the SAI 

Web site 

o	 Developed a PV Incubator Cell & 

Manufacturing Technology R&D fact sheet 

and flyer 

o	 Coordinated the Technology Pathway 

Partnership (TPP) award announcements 

for a media event and notified 

stakeholders through channels such as 

the Solar Energy Industries Association, 

SEPA, and the NCPV Hotline 

o	 Prepared the February 2007 TPP 

Workshop Proceedings for posting on the 

SAI Web site 

o Added For the Media and Awards 

sections to the SAI Web site 

o	 Managed and developed the 2007 Solar 

America Cities announcement; developed 

a media plan for DOE and worked with 

GO to implement the plan (Secretary 

Bodman announced Solar America Cities, 

the PV Incubator, and highlights of TPP 

awards at the American Council on 

Renewable Energy's Wall Street 

Renewable Energy Finance Conference, 

and EERE Assistant Secretary Karsner 

made a second announcement at a New 

York solar event); developed the media 

kit and Web content and coordinated 

development of the welcome kit content 

for city awardees 

o	 Assisted in completing the Solar America 

Showcase media kit and fact sheets for a 

kickoff activity. 

Fig. 3. The Solar Communications Team helped 

researchers tell the world about their new 

discoveries in 2007. 

3.3 Other SETP and NCPV Communications 

•	 Supported the NREL solar program and the 

NCPV by completing the FY 2007 Annual 

Operating Plan (AOP) 

•	 Assisted Sarah Kurtz and Steve Eglash in 

strategic planning for the NCPV and prepared 

10 Technology Roadmaps for use in AOP 

planning and other purposes. We also 

supported CSP strategic planning efforts by 

attending meetings as well as editing and 

preparing notes for dissemination 

•	 Contributed to, edited, and/or produced more 

than 350 presentations (including numerous 

technical illustrations and graphics), technical 

reports, subcontract reports, journal articles, 

and conference papers and posters, including 

the presentations for the annual SETP 

Program Review and Trough Workshop. 

•	 Completed an R&D100 nomination package 

for R&D Magazine on the High-Efficiency 

Metamorphic Multijunction Solar Cell 

developed by Spectrolab and NREL (this 

technology won the award); we also prepared 

material for the award banquet in Chicago. 

•	 Created and updated exhibits for the new S&T 

facility at NREL 

Systems Integration and Coordination 230
 

 

 

 

•	 Worked with NREL staff to develop a capital 

equipment plan for the Process Development 

Integration Laboratory. 

•	 Supported NREL and DOE staff for various 

public and media events at NREL, and for 

visits by Congress, industry, and other 

dignitaries. 

•	 Created a new Web site for the measurements 

and characterization work at NREL. 

•	 We prepared and implemented a 

comprehensive Web site maintenance plan for 

the NREL PV Web site, including analysis of 

common Webmaster inquiries to streamline 

the response process. We also update the 

NREL News and Events databases with solarrelated content, and we continue to support 

posting and archiving of the NCPV Hotline. 

•	 Because of our knowledge of solar 

technologies, we are asked to edit and/or write 

and produce various publications and projects, 

such as these: 

o	 A key article on the history and 

development of III-V cells at NREL and 

their impact on industry and society for the 

Technology Transfer Annual Report 

o	 A project for the NCPV on PV Conversion 

of Solar Energy for Terrestrial Applications 

o	 A factsheet on Solar Energy and Air 

Quality for the Energy Analysis Office 

o	 SAI poster for the Swedish Delegation and 

the Prime Minister’s visit to NREL. 

•	 We completed all preparations for Solar 

Decathlon 2007, including: 

o	 Writing a statement of work for an event 

management request for proposals and 

participating in the selection of the 

contractor; also, working extensively with 

the contractor to prepare for the event 

o	 Taking on sponsor relations, ensuring that 

their logistical needs and general 

participation worked smoothly 

o	 Preparing all publications and products in 

anticipation of and for the event; updating 

and publishing the 2007 Rules and 

Regulations; producing and updating the 

pre-event brochure, posters, and various 

flyers; interviewing all 20 teams for the 36-

page competition program; preparing 

extensive content for signage in the 

village; and providing most of the content 

for the media kit. 

o	 Developing a design for the Solar 

Decathlon home page and new subsites, 

such as the blog and photo database; 

updating all content to make it current for 

the event. 

4. Planned FY 2008 Activities 

•	 SETP Programmatic Communications—SETP 

management requires a variety of 

communications products to report its 

activities and results to audiences such as 

government, nongovernmental organizations 

(NGOs), the solar industry, the buildings 

industry, and consumers. Through 

management reports, Web sites, publications, 

and exhibiting, the Solar Communications 

Team will deliver messages about SETP’s 

activities and technologies to these critical 

audiences. Solar Energy Technologies 

Programmatic Communications includes the 

support of SAI R&D activities, such as Future 

Generation PV, PV Incubator, Technology 

Pathway Partnerships, and University PV 

Product and Process Development. 

•	 SAI Market Transformation—SAI’s market 

transformation activities include the Solar 

America Board of Codes & Standards, Solar 

America Cities and Showcases, and State and 

Utility Technical Outreach. As these activities 

progress toward implementation, there is a 

need to ensure that the communications 

needs of those activities are met in an overarching way. Market transformation requires a 

great deal of cooperation and collaboration 

between a variety of participants. The 

interdependent nature of this work requires 

communications tools internal to each project, 

and we must also continue to develop the 

capacity to report the progress and successes 

of various projects to all relevant stakeholders. 

•	 PV Program Management Communications— 

Solar program management at NREL and SNL 

requires a variety of products to report its 

activities to audiences such as NREL, SNL, 

and DOE management, government, NGOs, 

the solar and buildings industries, and 

consumers. Through management reports, 

Web sites, publications, and exhibiting, the 

Solar Communications Team delivers 

messages about these activities and 

technologies to critical audiences. 

•	 NREL/SNL Technology- and Activity-Specific 

Communications—These communications 

activities are not represented in the technical 

outreach agreements in the Corporate 

Planning System (CPS), but it is important to 

acknowledge each NREL and SNL SETP 

activity submitted in the FY 2008 AOP and 

represented in CPS. Each activity explicitly or 

implicitly represents needs that are met by the 

Solar Communications Team. 

231 Systems Integration and Coordination
 

5. FY 2007 Special Recognitions and Awards 

The Society of Technical Communicators 

conferred a 2007 Award of Excellence in the 

Online Competition for the TroughNet Parabolic 

Trough Solar Power Network. TroughNet is a 

technical resource for the evaluation of parabolic 

trough solar power plant technologies. The project 

was completed in FY 2006, but the award was 

given in FY 2007. 

6. Major FY 2007 Publications 

D. Gwinner et al., “DOE Solar Energy 

Technologies Program Newsletter,” published on 

SETP Web site only, July–October (2007). 

D. Gwinner et al., Report to Congress: 

Assessment of the Potential Impact of 

Concentrating Solar Power for Electricity 

Generation, DOE/GO-102007-2400, 33 pp., 

February (2007). 

S. Moon et al., DOE Solar Energy Technologies 

Program: FY 2006 Annual Report, DOE/GO102007-2436, 214 pp., July (2007). 

S. Moon et al., Powered by the Sun—2007 Solar 

Decathlon. Competition Program, DOE/GO102007-2459, 40 pp., September (2007). 

S. Pedigo et al., About the Solar America Initiative, 

Solar America Initiative, DOE/GO-102007-2444, 

2 pp., June (2007). 

S. Pedigo et al., In Focus—The Buildings Industry, 

Solar America Initiative, DOE/GO-102007-2389, 2 

pp., January (2007). 

S. Pedigo et al., PV Incubator Awards, Solar 

America Initiative, DOE/GO-102007-2445, 2 pp., 

June (2007). 

S. Pedigo et al., The Role of Utilities, Solar 

America Initiative, DOE/GO-102006-2369, 2 pp., 

October (2006). 

S. Pedigo et al., Solar America Initiative Across 

America, Solar America Initiative, DOE/GO102007-2443, 2 pp., June (2007). 

S. Pedigo et al., 2007 Solar America Cities 

Awards, Solar America Initiative, DOE/GO102007-2441, 2 pp., June (2007). 

S. Pedigo et al., Solar America Initiative Web site, 

redesign completed in September (2007). 

http://www.eere.energy.gov/solar/solar_america. 

S. Pedigo, S. Moon, and W. Bower, “Photovoltaic 

Technology Status and Prospects in the United 

States,” International Energy Agency Photovoltaic 

Power Systems Programme—Annual Report 

2006, May (2007). 

L. Poole et al., Improving Air Quality with Solar 

Energy, DOE Clean Energy and Air Quality 

Integration Initiative Fact Sheet Series, NREL/FS670-42169, September (2007). 

Systems Integration and Coordination 232
 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

International Activities 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Ruby Nahan (NREL), 303-384-7401, ruby_nahan@nrel.gov 

Ward Bower (SNL), 505-844-5206, wibower@sandia.gov 

DOE HQ Technology Manager:	 Tom Kimbis, 202-586-7055, tom.kimbis@ee.doe.gov 

FY 2007 Budgets:	 $150K (NREL), $130K (SNL) 

Objectives 

•	 Understand the drivers associated with international growth in photovoltaic (PV) sales. 

•	 Help Solar America Initiative (SAI) stakeholders with market development lessons in international 

growth. 

•	 Determine the performance of PV products abroad. 

•	 Help U.S. industry bring more affordable and reliable PV technology to the global marketplace. 

•	 Execute DOE commitments in international agreements and activities. 

Accomplishments 

•	 Supported participation in both International Energy Agency (IEA) Task 9, “Coordination of 

Renewable Energy Training and Certification Activities,” and IEA Task 10, “Urban Scale PV 

Applications." 

•	 Drawing from insights and information gained as a result of participation in IEA tasks, developed 

solar technical assistance package for large-scale installations (Solar America Showcase) and 

city projects (City Strategic Partnerships) that use new solar technologies with the potential of 

achieving DOE cost goals. 

•	 Presented updates on the U.S. solar industry at IEA meetings in Athens, Greece; Madrid, Spain; 

and Ebeltoft, Denmark. 

Future Directions 

•	 Execute SAI Market Transformation activities (e.g., technical assistance, acceptance testing, 

performance evaluations) to get new solar technologies developed through SAI’s Technology 

Pathway Partnerships adopted by the U.S. and international marketplace. 

•	 Devise specific ways to overcome newly IEA-identified barriers to international market 

transformation that may be associated with lack of consumer confidence, inadequate training, 

poor technology performance, regulatory obstacles, and high cost. 

•	 Support participation in IEA Task 10, “Urban Scale PV Applications,” for which the United States 

is the operating agent (NREL) and IEA Task 1, “Exchange and Dissemination of Information of 

Photovoltaic Power Systems” (NREL and SNL). 

1. Introduction policy impacts, sharing this information, and 

determining how to improve U.S. PV product 

The primary mission is to continually learn from performance at a lower cost. Through our IEA 

the international adoption of solar technologies involvement, as well as our strategic planning 

and improve U.S. solar technologies sold exercise, our team members also tried to provide 

domestically and abroad. Because Germany, timely data on emerging markets, nurture 

Japan, and Europe continue to drive the growth of relationships with key manufacturers and 

the solar market, our task included: keeping integrators abroad, and distribute this information, 

current on why this is happening, understanding where appropriate, to the U.S. solar industry. 

233 Systems Integration and Coordination
 

 

 

2. Technical Approach 

DOE’s international activities have involved NREL, 

SNL, and multiple university and corporate 

partners. This multi-institutional approach has 

focused on gathering useful field information in the 

United States and abroad on solar technology 

adoption (or rejection), conducting analysis on why 

this happened, and doing field performance 

assessments to determine how and why specific 

deployed solar systems are behaving in a 

particular manner. This information has then been 

disseminated to the DOE solar R&D community 

through written reports, technical papers, posters, 

and briefings. 

Based on our newly developed strategic plan, we 

enumerated four strategies to carry out this 

technical approach: 

1. Contribute international market and system 

data for improved modeling and analysis. 

2. Provide market information to DOE to increase 

the competitive edge for the U.S. solar 

industry. 

3. Use international experience as a surrogate 

for U.S. market development. 

4. Contribute to improved performance and 

reliability for U.S. solar products using 

international systems application samples for 

testing and monitoring. 

Task Title FY 2007 

Budget ($K) 

PV International (NREL) 150 

PV International (SNL) 130 

3. Results and Accomplishments 

Our multi-institutional team worked hand-in-hand 

with staff at the DOE Solar Program to define and 

detail the planned Solar America Initiative (SAI) 

Technology Acceptance activities. These activities 

are focused on reducing market barriers and 

transforming the market for wider use of solar 

energy technologies in the United States. This 

work included our team’s participation in multiple 

Technical Exchange Meetings to solicit and garner 

input from U.S. industry, consumers, and state 

and local government officials on these new 

activities. All of this input—including relevant 

elements of the recently published international 

strategic plan—were then incorporated by DOE 

into a wider Technology Acceptance plan. This 

became our new guide for future activities, and the 

plan was used as the substantive basis for the 

first, second, and ongoing third round of funding 

opportunity announcements in Technology 

Acceptance. 

•	 Presented the Task 10 status report at the IEA 

29th PV Power Systems Operating Agents 

Meeting, hosted by the European PV Industry 

Association, and attended the Executive 

Committee Meeting, April 14-20, 2007, in 

Athens, Greece. 

•	 Completed the U.S. annual contribution to the 

IEA Annual Report for PV Technology Status 

in the United States. The U.S. submission is a 

summary of R&D, policy, U.S. industry, and 

DOE program accomplishments for 2006. 

•	 Completed the IEA country report and 

presentation for the IEA ExCo Meeting in 

South Korea. 

•	 Completed the U.S. country report and 

presentation for the IEA Executive Committee 

meeting held in Zaragoza, Spain. 

•	 Reviewed and revised the final IEA National 

Survey Report written for IEA Task 1. 

•	 Attended the annual IEA PVPS Task I meeting 

in Zacatecas, Mexico, and gave presentation 

on the state of the PV industry and policy 

issues for a colloquium hosted by Zacatecas 

State government and the United Nations. 

4. Ongoing and Planned FY 2008 Activities 

SAI represents a change from DOE’s past 

international activities to present and future 

activities focused on markets and applications that 

can result in wider utilization of solar technologies 

in the United States. This transformation is well 

under way and consists of the following activities 

conducted by our team: 

•	 Organization and formation of tiger teams for 

provision of technology assistance and 

sharing of solar knowledge gleaned from the 

field among the DOE solar R&D community. 

•	 Development of specific ways to overcome 

identified market barriers (e.g., lack of 

consumer confidence, inadequate training, 

poor technology performance, regulatory 

obstacles, and high cost). 

•	 Continuation of support for U.S. participation 

in IEA Task 10, “Urban Scale PV 

Applications,” and IEA Task 1, “Exchange and 

Dissemination of Information on Photovoltaic 

Power Systems." 

•	 Continuation of support for SAI market 

transformation teams with task results through 

either workshops webinars or conferences. 

Systems Integration and Coordination 234
•	 Facilitation of IEA in North America/Pacific rim 

meetings conferences and information 

exchange. 

5. Major FY 2007 Publications 

C. Herig, “Bi-annual Report for FY 2007 IEA PV 

Power Systems Task 10: Operating Agent,” AprilAugust 2007. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2007 

($K) 

Segue Energy Consulting, LLC 

Christy Herig 

Redington Shores, FL 

cherig@tampabay.rr.com 

IEA PV Power Systems Task 10 

(Urban PV) Support 109 

Institute for Sustainable Power 

Roger Taylor 

Evergreen, CO 

roger_taylor@nrel.gov 

Coordination of Renewable 

Energy Training and Certification 

Activities and Support of IEA Task 

9 Activities 

38.8 

235 Systems Integration and Coordination
 

 

____________________________________________________________________________________ 

 

____________________________________________________________________________________ 

Small Business Innovation Research 

Performing Organization: DOE HQ Solar Energy Technologies Program 

DOE HQ Technology Manager: Alec Bulawka, 202-586-5633, alec.bulawka@ee.doe.gov 

FY 2007 Budget: $2,093K 

Objectives 

•	 Support small business energy R&D. 

•	 Implement Executive Order 13329, which involves assisting the private sector in manufacturing 

innovation. 

•	 Continue to pursue wise cost/benefit investments. 

•	 Augment the core research of the DOE Solar Program. 

•	 Support effectively the Solar America Initiative. 

Accomplishments 

•	 Developed a PV system designed for H2 production by electrolysis with the goal of reducing the 

cost of large-scale PV-generated H2 production. (project began in 2005 and finished in 2007) 

•	 Adapted metallurgical techniques for purifying silicon much more cheaply than the standard 

process, to produce a cheaper grade of silicon for photovoltaics (PV), and developed a reusable 

crucible for Silicon ingot casting for PV. (project began in 2004 and finished in 2007) 

Future Directions 

•	 Focus on material and process cost-saving techniques, as well as associated manufacturing 

diagnostics for manufacturing solar/PV (silicon and other thin films, as well as organics). 

•	 Seek new solar concentrator structural (non-cell) designs for ease of manufacturing and cost 

reduction. 

•	 Incorporate emerging innovative ways to use waste thermal energy in PV concentrators’ electric 

output. 

•	 Continue aggressive pursuit of organic PV solar cells incorporating nanotechnology. 

•	 Achieve significant cost reduction in manufacture of crystalline silicon PV products. 

•	 Seek effectiveness in PV-powered, renewable, hydrogen production as storage for PV energy. 

•	 Focus on cost reduction via improvement of non-cell mechanical ancillary hardware. 

1. Introduction 

Each year, ten federal departments and agencies 

(including DOE) are required by the Small Business 

Innovation Research (SBIR) Program to reserve a 

portion of their R&D funds for award to small, U.S.-

owned businesses. Over the life of the SBIR 

Program, the Solar Program has contributed $16 

million and received $34 million in research 

funding. 

The Solar Program has also benefited to a large 

extent from the Office of Basic Energy Sciences 

contribution in nanotechnology topics for PV in 

2006. The 2007 Solar Program is nested mainly in 

the Renewable Energy Sources SBIR category 

(Topic 2). SBIR activities fit very nicely into the 

DOE Solar Program Multi-Year Technical Plan, 

because they continue to augment and support the 

core program, in all aspects, with integrated 

solutions from the vast U.S. small business 

community. Also, this year, the community has the 

opportunity to partake actively in the Solar America 

Initiative (SAI) through carefully selected and 

tailored supportive solicitations. 

2. Technical Approach 

Renewable energy technologies have achieved 

significant advances in recent years, but further 

improvements are needed if they are to reach their 

full potential. The solar technologies included in the 

scope of this SBIR work address both solar electric 

(photovoltaic or PV) and concentrating solar power 

(CPS) systems. Grant applications for FY 2007 

were required to clearly demonstrate the applicants’ 

Systems Integration and Coordination 236
 

 

 

ability to proceed to hardware development, 

fabrication, testing and manufacture of 

technologies. 

3. Results and Accomplishments 

Several SBIR awards advanced their goals and 

produced very encouraging results of their R&D to 

date. (See table below.) 

4. Planned FY 2008 Activities 

Further development of PV and CSP systems will 

be addressed through creative and innovative 

approaches in engineering and design, and new 

materials and processes. A concerted effort has 

been made to have the SBIR activity dovetail in 

support of the SAI. 

4.1 Monitoring and Self-Diagnosing PV Systems, 

Components, and Modules 

Reliability is particularly important for new module 

and inverter technologies. Innovative methods will 

be sought to monitor PV system and component 

performance and to relate performance to actual 

weather, so as to ascertain failure and loss 

mechanisms as quickly as possible. Such 

monitoring and diagnostics can be embedded in 

system components resulting in, for example, 

state-of-health system sensors, smart metering, 

load-management controllers, and smart inverters. 

4.2 PV (Crystalline Silicon and Thin Film) 

Manufacturing Diagnostics 

Diagnostic technologies will be sought to improve 

yield and reduce cost of crystalline silicon PV 

manufacturing of cells and modules. Focus will be 

on identification and resolution of wafer stress and 

wafer cracks, wafer-handling technologies in 

production, improved interconnect technologies for 

wafer assembly, stress management, and 

improved manufacturing data tracking. Also, 

diagnostic and control technologies to improve 

yield, increase materials utilization, and reduce the 

cost of thin-film PV module manufacturing will be 

pursued. 

4.3 Non-Inverter Balance-of-System (BOS) 

Components and Net-Metering Technologies 

This effort involves improving non-inverter BOS 

components for PV applications for grid-interactive 

systems. Customized circuit breakers, simplified or 

standardized wiring methodologies for buildingintegrated PV applications, junction boxes and 

innovative inter-array wiring, as well as mounting 

methodologies and installation concepts, will be 

pursued. State-of-system health monitoring 

capabilities, system-predictive monitoring, and 

safety and logic controls for complete system code 

and standards compliance will also be solicited. 

These are only some examples of a vast 

complement of ancillary needs. 

4.4 Non-Cell Concentrator Photovoltaic System 

Components 

With the development of the high-efficiency (40%) 

multijunction solar cell, concentrating PV (CPV) 

systems will become much more cost effective. 

The SBIR focus will shift to innovation in optical 

concentration designs (refractive, reflective, and 

holographic concepts). Tracking structures, control 

logic, torque leveraging, gears, hydraulics, and 

wind-loading protection schemes will now be 

addressed. Reduction of costly steel content (yet 

maintaining structural integrity), avoidance of 

mechanical resonances under wind loading, and 

innovative ideas in cell cooling will also get 

attention. Integrated CPV concepts, building CPV, 

and luminescent concentration are also on the 

agenda. 

5. Major FY 2007 Publications 

The SBIR Program holds the awardee responsible 

for a final report at the end of both Phase 1 and 

Phase 2. The SBIR Office in Germantown, MD, 

has on file the final reports of all the projects 

awarded in the past. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2007. 

Organization/ 

Principal 

Investigator 

Location/e-mail Description/Title of Research Activity 

Luna Innovations, 

Inc. 

Roanoke, VA 

kocherginv@lunainnovations.com 

Develop an in-line high-throughput PV 

manufacturing diagnostic system capable of 

237 Systems Integration and Coordination
 

 

 

Dr. Vladimir 

Kochergin 

fast and accurate identification of the 

distribution of stress and coating uniformity, 

allowing improved process control, 

increased yield and reduced cost. 

Ultrasonic 

Technologies, Inc. 

Sergei Ostapenko 

Wesley Chapel, Florida 

sergei.ostapenko@ultrasonictech.com 

Justify a commercial prototype of the 

proprietary Resonance Ultrasonic Vibrations 

(RUV) system for use as a real-time in-line 

automatic process control tool for 

identification and rejection from a solar cell 

production line 

Advanced Cooling 

Technologies, Inc. 

Lancaster, PA 

info@1-ACT.com 

Use heat pipe technology to efficiently 

remove the heat from the device 

overcoming a key hurdle to improving the 

overall system level efficiency. 

Luminit, LLC Torrance, CA 

kyu@luminitco.com 

Develop a new thin, chromatic dispersion 

corrected, high efficiency, rugged, and lowcost flexible spectrum splitting holographic 

concentrator (SSHOC). 

SVV Technology 

Innovations Inc. 

Dr. Sergey Vasylyev 

McClellan, CA 

vasilyev@svvti.com 

Improve the sunlight concentration and 

optical efficiency in photovoltaic modules 

through the use of a novel reflective lens 

concept. 

Nanosolar, Inc. Palo Alto, CA 

bsager@nanosolar.com 

Construct foil-based solar cells with a 

relative 25% increased active-area power 

conversion efficiency. 

TDA Research, Inc. 

Michael D. Diener 

Wheat Ridge, CO 

mikee@tda.com 

Develop new fullerene-based n-type 

materials for solvent- processable low-cost 

organic photovoltaics (OPV). 

MWOE Solar, Inc. Toledo, OH 

Develop process that will interconnect the 

cells after all thin-film deposition steps are 

complete, by utilizing a sequence of ink-jet 

printing and scribing steps. 

NanoSonic, Inc. Blacksburg, VA 

540-953-1785 (phone) 

Develop flexible mirror technology 

And environmental coating materials for the 

mirror surfaces. 

GT Solar, Inc. 

Dr. P. Santhana 

Raghavan 

Merrimack, NH 

raghavan@gtsolar.com 

Develop low cost processes for producing 

crystalline (multicrystalline and single 

crystal) silicon ingots and use of reusable 

crucibles. 

MetroLaser, Inc. 

Bauke Heeg 

Irvine, CA 

bheeg@metrolaserinc.com 

Develop process to provide a direct means 

to extract energy from waste heat as well as 

from solar radiation. 

GT Solar, Inc. 

Dr. P. Santhana 

Raghavan 

Merrimack, NH 

raghavan@gtsolar.com Produce solar grade polysilicon directly 

from metallurgical grade silicon (MGSi). 

Crystal Systems, 

Inc. 

Dr. David B. Joyce 

Salem MA 

djoyce@crystalsystems.com 

Adapted metallurgical techniques for 

purifying silicon much more cheaply than 

the standard process, to produce a cheaper 

grade of silicon for photovoltaics (PV). 

UQM Technologies, 

Inc. 

Frederick, CO 

303-278-2002 

Improve power density and reliability for 

next-generation, grid-capable inverter 

technology. 

Amonix Torrance, CA 

info@amonix.com 

Develop a PV system designed for H2 

production by electrolysis. The project’s 

aim was to reduce the cost of large-scale 

PV-generated H2 production. 

Systems Integration and Coordination 238
 

 

Funding Table 

Below are the complete budgets for specific NREL PV conversion technologies, referenced in the 

Fundamental Research section of the FY 2008 Annual Report. 

Conversion Technologies Research Areas FY07 Budget ($K) Estimates 

Wafer Silicon Silicon Materials & Devices 1,272 

Processes & Advanced Concepts 764 

Concentrator Crystalline Cells 20 

Analytical Microscopy 140 

Electro-Optical Characterization 190 

Surface Analysis 33 

TOTAL 2,419 

Film Silicon Film Silicon 1,272 

Thin-Film Polycrystalline Compounds 137 

Processes & Advanced Concepts 509 

Concentrator Crystalline Cells 20 

Analytical Microscopy 80 

Electro-Optical Characterization 40 

Surface Analysis 33 

TOTAL 2,091 

OPV Processes & Advanced Concepts 509 

Exploratory Research – OPV 205 

Electro-Optical Characterization 44 

Surface Analysis 6 

TOTAL 764 

CdTe Thin-Film Polycrystalline Compounds 1,302 

Fundamental R&D 535 

Processes & Advanced Concepts 255 

Concentrator Crystalline Cells 40 

Analytical Microscopy 70 

Electro-Optical Characterization 60 

TOTAL 2,262 

239 Appendix: Funding Table
 

Conversion Technologies Research Areas FY07 Budget ($K) Estimates 

CIGS Thin-Film Polycrystalline Compounds 1,097 

Fundamental R&D 180 

Silicon Materials & Devices 30 

Processes & Advanced Concepts 509 

Concentrator Cyrstalline Cells 60 

Analytical Microscopy 70 

Electro-Optical Characterization 44 

Surface Analysis 120 

TOTAL 2,110 

CPV Concentrator Cyrstalline Cells 2,229 

Fundamental R&D 405 

Analytical Microscopy 40 

Electro-Optical Characterization 36 

Surface Analysis 27 

Cell and Module Performance 62 

TOTAL 2,799 

Appendix: Funding Table 240
 

 

Performing Organizations By Name 

NAME PAGE
 

Advanced Cooling Technologies, Inc. ...... 238
 

AFG Industries ............................................ 81
 

Alternative Energy Institute ....................... 151
 

American Wind Energy Association ......... 151
 

Amonix, Inc............................. 11, 73, 80, 238
 

Antares ..................................................... 224
 

Appalachian State University .................... 151
 

Arizona State University ......... 12, 80, 81, 142
 

Array Technologies ..................................... 80
 

ATS Ohio, Inc. ............................................ 81
 

BCS, Inc.................................................... 179
 

Bekaert Corporation ................................... 81
 

BEW Engineering ............................... 99, 142
 

Bluepoint Associates .................................. 81
 

Boeing Company .................................. 73, 80
 

BP Solar International, Inc...... 73, 81, 88, 151
 

Brookhaven National Laboratory (BNL) ..... 58
 

California Institute of Technology

 (Caltech) ........................................... 11, 80
 

Carlisle Syntec, Inc..................................... 81
 

Carnegie Mellon........................................ 154
 

Central State University .............................. 11
 

Ceradyne Thermo Materials ....................... 81
 

City of Ann Arbor, MI ................................ 165
 

City of Austin, TX...................................... 165
 

City of Berkeley, CA ................................. 165
 

City of Boston, MA .................................... 165
 

City of Madison, WI .................................. 165
 

City of New Orleans, LA ........................... 165
 

City of New York, NY ................................ 165
 

City of Pittsburgh, PA ............................... 165
 

City of Portland, OR .................................. 165
 

City of Salt Lake, UT ................................. 165
 

City of San Diego, CA ............................... 165
 

City of San Francisco, CA ........................ 165
 

City of Tucson, AZ .................................... 165
 

Clean Energy Group ......................... 174, 177
 

Clean Energy States Alliance, Inc. ........... 177
 

Coal Creek Design, Inc. .............................. 81
 

Colorado Code Consulting, LLC ............... 154
 

Colorado School of Mines .................... 82, 95
 

Colorado State University ........................... 95
 

Conergy, Inc. .............................................. 82
 

Cornell University...................................... 154
 

Cryo Industries ............................................ 80
 

Crystal Systems ........................................ 238
 

Davis Energy Group ................................. 218
 

DEERS ....................................................... 82
 

DOE Golden Field Office (DOE/GO) ... 71, 89,
 

................ 115, 121, 125,149, 152, 157, 227 

DOE HQ Solar Energy Technologies

 Program ................................................. 236
 

NAME PAGE
 

Dow Chemical Company................. 73, 81, 88
 

Dow Corning Corporation................ 81, 82, 88
 

Duke University ........................................... 11
 

ECO Northwest ......................................... 102
 

Energy Conversion Devices, Inc. ................ 82
 

Electric Power Research Institute ............... 99
 

Energy Matters .......................................... 177
 

Energy Photovoltaics .................................. 95
 

Evergreen Solar, Inc. .................................. 88
 

Exeltech, Inc................................................ 81
 

FAFCO, Inc. .............................................. 218
 

Fat Spaniel Technologies, Inc. .................... 81
 

Ferro Corporation ........................................ 81
 

First Solar, LLC ..................................... 88, 95
 

Fisk University............................................. 82
 

Florida Solar Energy Center (FSEC) 

....... 95, 117, 120, 124, 142, 164, 170, 171 

Fronius USA, LLC ....................................... 81 

General Electric (GE) 

Company .............................. 73, 81, 88, 99 

Georgia Institute of Technology 

(Georgia Tech) ..........................11, 81, 154
 

Georgia Tech Research Institute ................ 81
 

Gilman, Paul ...................................... 105, 196
 

Global Energy Decisions ............................. 99
 

Global Solar Energy .................................... 96
 

GreenRay, Inc. ...................................... 73, 81
 

GT Solar, Inc. ............................................ 238
 

Home Power Magazine ............................. 151
 

Howard University ....................................... 11
 

International Brotherhood of Electrical
 

Workers (IBEW) ..................................... 151
 

IBIS Associates ........................................... 81
 

Imperial Irrigation District ............................ 80
 

Innovators.................................................... 80
 

Institute for Sustainable Power ................. 235
 

Interstate Renewable Energy Council
 

(IREC) ................................... 142, 143, 151
 

Janzou Consulting ............................. 105, 196
 

Kansas State University ............................ 154
 

Kearney and Associates ........................... 208
 

Komax Systems, York ................................. 81
 

Konarka Technologies, Inc.................... 73, 81
 

Lawrence Berkeley National 

Laboratory (LBNL) ......................... 100, 160
 

Light Prescriptions ....................................... 80
 

Luminit, LLC .............................................. 238
 

Luna Innovations ....................................... 237
 

Madison Energy Consultants .................... 177
 

Malaspina College ..................................... 151
 

Massachusetts Institute of 

Technology (MIT) ............................. 82, 154
 

241 Appendix: Performing Organizations By Name
 

NAME PAGE
 

MetroLaser, Inc. ........................................ 238
 

Miasolé, Inc. ................................................ 81
 

Midwest Renewable Energy Association . 151
 

Morse Associates, Inc .............................. 193
 

MWOE Solar, Inc...................................... 238
 

Nanosolar ............................... 73, 82, 96, 238
 

NanoSonic, Inc. ............................ 73, 96, 238
 

NASEO ..................................................... 177
 

National Association of Regulatory
 

Utility Commissioners (NARUC).... 174, 177 

National Conference of State 

Legislatures (NCSL) ...................... 174, 177 

National Electrical Contractors 

Association ............................................ 151 

National Joint Apprenticeship and 

Training Committee ............................... 151 

National Renewable Energy Laboratory 

(NREL)............................... 4, 13, 20, 25, 30 

34, 37, 62, 69, 71, 73, 80, 81, 82, 83, 89, 

97, 100, 103, 111, 115, 125, 131, 137, 141, 

151, 152, 157, 160, 162, 170, 171, 178, 

184, 190, 191, 194, 201, 210, 227, 233 

Navigant Consulting ................................... 99 

New Mexico State University (NMSU) 

...... 120, 137, 142, 143, 148, 164, 170, 171 

New York Institute of Technology............. 155 

New York State Energy Research and 

Development Authority (NYSERDA)148, 151 

Nexant ...................................................... 208 

Nimmons, John & Associates, Inc............ 177 

North American Board of Certified

 Energy Practitioners (NABCEP) ... 148, 149 

North Carolina A&T State University .......... 11 

North Carolina Central University ............... 11 

North Carolina State University (NCSU)/ 

North Carolina Solar Center .... 11, 148, 151 

Northern Plains Power ...................... 106, 110 

Northwestern University ............................. 11 

Oak Ridge National Laboratory (ORNL) ... 219 

Oregon State University ............................. 11 

Pacific Northwest National Laboratory 

 (PNNL)..................................................... 96
 

Palo Alto Research Center ......................... 81
 

Pennsylvania State University ............ 11, 155
 

PowerLight Corporation ...................... 88, 151
 

PowerMark Corporation .................... 114, 142
 

Primestar Solar ........................................... 24
 

PV Powered, Inc. .................................. 80, 82
 

REC Silicon, Inc. ......................................... 81
 

Recticle UREPP N. America ....................... 81
 

Sandia National Laboratories ........ 71, 73, 81,
 

81, 82, 97, 103, 106, 111, 118, 121, 125, 

137, 142, 151, 162, 170, 171, 190, 191, 

194, 197, 201, 210, 227, 233 

Santa Clara University .............................. 155 

NAME PAGE
 

Sanyo Energy USA Corporation ................. 81
 

Satcon Technology Corporation ................. 82
 

SCHOTT Solar, Inc. .................................... 88
 

Segue Energy Consulting, LLC ................. 235
 

Sharp Solar ............................................... 151
 

Sherwood Associates................................ 142
 

Shingleton Design LLC ............................... 88
 

Silicon Genesis Corporation ........................ 82
 

SMA America, Inc. ...................................... 82
 

SMUD .......................................................... 81
 

Solaicx, Inc............................................ 81, 82
 

Solar Electric Power Association 

(SEPA) ........................................... 174, 177
 

Solar Energy International ......................... 151
 

Solar Rating Certification Corporation ...... 151
 

Solar Systems ........................................... 189
 

SolarWorld Industries America ................... 88
 

SolFocus ............................................. 81, 189
 

Solectric Renewables LLC .......................... 82
 

Soliant Energy, Inc. ............................... 73, 82
 

Sonenthal and Overall............................... 177
 

Southern California Edison ......................... 80
 

Southern University and A&M College ........ 11
 

Southwest Technology Development 

Institute (SWTDI) .................. 124, 148, 151 

Specialized Technology 

Resources, Inc............................. 78, 81, 82 

Spectrolab, Inc. ............................... 12, 80, 82 

Spire Corporation ................................ 88, 130 

State University of New York (SUNY), 

Albany – Research Foundation ..... 137, 142
 

SunEarth ................................................... 218
 

SunEdison ........................................... 82, 151
 

Sunlight Direct, LLC .................................. 224
 

Sunlink, LLC ................................................ 82
 

SunPower Corporation ..... 73, 82, 88, 99, 151
 

Sunset Technologies ................................. 114
 

Suntechnics Energy System, Inc. ............... 82
 

SVV Technology Innovations, Inc. ............ 238
 

Syracuse University .................................... 82
 

Sylarus Technologies, LLC ......................... 80
 

TDA Research ........................................... 238
 

Team Montreal .......................................... 155
 

Technische Universität Darmstadt ............ 155
 

Texas A&M University ....................... 117, 155
 

Texas Tech ................................................. 12
 

Thermal Energy System Specialists, Inc. . 218
 

Tucson Electric Power ...................... 137, 142
 

Underwriters Laboratories ................... 12, 142
 

Ultrasonic Technologies, Inc..................... 238
 

UQM Technologies, Inc. ............................ 238
 

United Solar Ovonic ........................ 73, 82, 96
 

Universidad de Puerto Rico ...................... 155
 

University of Central Florida ........................ 81
 

University of Cincinnati .............................. 156
 

Appendix: Performing Organizations By Name 242
NAME PAGE
 

University of Colorado at Boulder . 12, 81, 155
 

University of Delaware .......................... 12, 81
 

University of Illinois ................................... 156
 

University of Maryland .............................. 156
 

University of Minnesota ............................ 218
 

University of Missouri – Rolla ................... 156
 

University of Nevada, Las Vegas 

(UNLV)............................................... 80, 96
 

University of Oregon ....................... 12, 82, 96
 

University of South Florida ......................... 96
 

University of Tennessee ........................... 224
 

University of Texas at Austin .................... 156
 

University of Texas at Brownsville .............. 12
 

University of Texas at El Paso.................... 12
 

University of Toledo .............................. 12, 96
 

University of Utah ....................................... 96
 

University of Wisconsin, Madison ..... 105, 196
 

Xantrex Technologies, Inc........ 80, 81, 82, 88
 

243 Appendix: Performing Organizations By Name
Appendix: Performing Organizations By Name 244
Performing Organizations By State/Country 

NAME PAGE
 

ARIZONA 

Arizona State University/UL .... 12, 80, 81, 142 

City of Tucson ........................................... 165 

Global Solar Energy ................................... 96 

PowerMark Corporation .................... 114, 142 

Sunset Technologies ................................ 114
 

Tucson Electric Power ...................... 137, 142
 

Xantrex Technologies, Inc.......................... 88
 

AUSTRALIA 

Solar Systems ........................................... 189
 

CALIFORNIA 

Amonix, Inc. ............................ 11, 73, 80, 238 

Array Technologies ..................................... 80 

Bekaert Corporation ................................... 81 

BEW Engineering ............................... 99, 142 

Bluepoint Associates .................................. 81 

Boeing Company .................................. 73, 80 

California Institute of Technology
 

(Caltech) ............................................ 11, 80 

City of Berkeley, CA ................................. 165
 

City of San Diego, CA ............................... 165
 

City of San Francisco, CA ........................ 165
 

Davis Energy Group ................................. 218 

DEERS ....................................................... 82
 

Electric Power Research Institute ............... 99
 

FAFCO, Inc............................................... 218 

Fat Spaniel Technologies, Inc. ................... 81
 

Imperial Irrigation District............................ 80
 

Lawrence Berkeley National 

Laboratory (LBNL) ......................... 100, 160 

Light Prescriptions ...................................... 80
 

Luminit, LLC .............................................. 238
 

MetroLaser, Inc. ........................................ 238 

Miasolé, Inc. ................................................ 81
 

Nanosolar ............................... 73, 82, 96, 238
 

Navigant Consulting ................................... 99
 

Nexant ...................................................... 208 

Palo Alto Research Center ......................... 81
 

PowerLight Corporation .............................. 88 

Primestar Solar ........................................... 24
 

Santa Clara University .............................. 155 

Silicon Genesis Corporation ....................... 82
 

SMA America, Inc. ...................................... 82
 

SMUD ......................................................... 81
 

Solaicx, Inc. .......................................... 81, 82
 

SolarWorld Industries America ................... 88 

SolFocus ............................................. 81, 189
 

Soliant Energy, Inc. .............................. 73, 82
 

Southern California Edison ......................... 80
 

NAME PAGE
 

Spectrolab, Inc. ............................... 12, 80, 82
 

SunEarth ................................................... 218
 

Sunlink, LLC ................................................ 82
 

SunPower Corporation ..... 73, 82, 88, 99, 151
 

Suntechnics Energy System, Inc. ............... 82
 

SVV Technology Innovations, Inc. ............ 238
 

Xantrex Technologies, Inc........ 80, 81, 82, 88 

CANADA 

Malaspina College ..................................... 151
 

Team Montreal .......................................... 155
 

Xantrex Technologies, Inc............... 80, 81, 82
 

COLORADO 

Coal Creek Design ...................................... 81 

Colorado Code Consulting, LLC ............... 154
 

Colorado School of Mines ..................... 82, 95
 

Colorado State University ........................... 95 

DOE Golden Field Office (DOE/GO) ..... 71, 89
 

.............. 115, 121, 125, 149, 152, 157, 227 

Global Energy Decisions ............................. 99
 

Institute for Sustainable Power ................. 235
 

Janzou Consulting ............................. 105, 196
 

National Conference of State 

Legislatures (NCSL)....................... 174, 177 

National Renewable Energy Laboratory 

(NREL) .............................. 4, 13, 20, 25, 30 

34, 37, 62, 69, 71, 73, 80, 81, 82, 83, 89, 

97, 100, 103, 111, 115, 125, 131, 137, 141, 

151, 152, 157, 160, 162, 170, 171, 178, 

184, 190, 191, 194, 201, 210, 227, 233 

Sherwood Associates................................ 142 

Solar Energy International ......................... 151 

TDA Research ........................................... 238 

University of Colorado at Boulder .12, 81, 155 

UQM Technologies ................................... 238 

CONNECTICUT 

Specialized Technology 

Resources, Inc............................. 78, 81, 82 

DELAWARE 

General Electric (GE) 

Company ............................... 73, 81, 88, 99
 

University of Delaware .......................... 12, 81
 

DISTRICT OF COLUMBIA 

American Wind Energy Association .......... 151 

DOE HQ Solar Energy Technologies 

Program ................................................. 236
 

245 Appendix: Performing Organizations By State/Country
 

NAME PAGE
 

Energy Matters ......................................... 177
 

Howard University....................................... 11 

International Brotherhood of Electrical
 

Workers (IBEW) .................................... 151
 

Madison Energy Consultants .................... 177
 

Morse Associates, Inc .............................. 193 

NASEO ..................................................... 177
 

National Association of Regulatory
 

Utility Commissioners (NARUC).... 174, 177
 

National Joint Apprenticeship and
 

Training Committee ............................... 151
 

Nimmons, John & Associates, Inc............ 177
 

Solar Electric Power Association 

(SEPA) ........................................... 174, 177
 

Sonenthal and Overall .............................. 177
 

FLORIDA 

Florida Solar Energy Center (FSEC) 

........ 95, 117, 120, 124, 142, 164, 170, 171
 

Segue Energy Consulting, LLC ................ 235 

Solar Rating Certification Corporation
 

(SRCC) .................................................. 151
 

Ultrasonic Technologies, Inc. ................... 238
 

University of Central Florida ....................... 81
 

University of South Florida ......................... 96 

GEORGIA 

Ceradyne Thermo Materials ....................... 81 

Georgia Institute of Technology 

(Georgia Tech) .......................... 11, 81, 154 

Georgia Tech Research Institute ................ 81
 

GERMANY 

Technische Universität Darmstadt............ 155 

ILLINOIS 

Gilman, Paul ..................................... 105, 196
 

Northwestern University ............................. 11 

Underwriters Laboratories .................. 12, 142
 

University of Illinois ................................... 156 

KANSAS 

Kansas State University ........................... 154
 

LOUISIANA 

City of New Orleans, LA ........................... 165
 

Southern University and A&M College ....... 11 

MAINE 

Cryo Industries ............................................ 80
 

MARYLAND 

Antares ..................................................... 224 

BCS, Inc.................................................... 179 

BP Solar International, Inc.............. 73, 81, 88 

NAME PAGE
 

National Electrical Contractors 

Association ............................................. 151
 

SunEdison ........................................... 82, 151
 

University of Maryland............................... 156
 

MASSACHUSETTS 

City of Boston, MA .................................... 165
 

Crystal Systems ........................................ 238
 

Evergreen Solar, Inc. .................................. 88 

GreenRay, Inc. ...................................... 73, 81
 

IBIS Associates ........................................... 81
 

Konarka Technologies, Inc.................... 73, 81
 

Massachusetts Institute of Technology 

(MIT)................................................. 82, 154
 

Satcon Technology Corporation ................. 82
 

SCHOTT Solar, Inc. .................................... 88 

Solectric Renewables LLC .......................... 82
 

Spire Corporation ................................ 88, 130
 

MICHIGAN 

City of Ann Arbor, MI ................................. 165
 

Dow Chemical Company................. 73, 81, 88
 

Dow Corning Corporation................ 81, 82, 88
 

Energy Conversion Devices, Inc................. 82 

Fronius USA, LLC ....................................... 81
 

Recticle UREPP N. America ....................... 81
 

United Solar Ovonic ........................ 73, 82, 96
 

MINNESOTA 

University of Minnesota ............................. 218
 

MISSOURI 

University of Missouri - Rolla..................... 156
 

NEVADA 

University of Nevada, Las Vegas 

(UNLV) ............................................... 80, 96
 

NEW HAMPSHIRE 

GT Solar, Inc. ............................................ 238
 

NEW JERSEY 

Energy Photovoltaics .................................. 95
 

Sharp Solar ............................................... 151
 

NEW MEXICO 

Conergy, Inc................................................ 82
 

Innovators.................................................... 80
 

New Mexico State University (NMSU)
 

...... 120, 137, 142, 143, 148, 164, 170, 171
 

Sandia National Laboratories .........71, 73, 81,
 

81, 82, 97, 103, 106, 111, 118, 121, 125, 

137, 142, 151, 162, 170, 171, 190, 191, 

194, 197, 201, 210, 227, 233 

Appendix: Performing Organizations By State/Country 246
 

NAME PAGE
 

Southwest Technology Development 

Institute (SWTDI) ................... 124, 148, 151
 

NEW YORK 

Brookhaven National Laboratory (BNL) ..... 58 

City of New York, NY ................................ 165
 

Cornell University...................................... 154
 

General Electric (GE) 

Company ............................... 73, 81, 88, 99
 

Interstate Renewable Energy Council

 (IREC).................................... 142, 143, 151
 

New York Institute of Technology............. 155
 

New York State Energy Research and
 

Development Authority (NYSERDA)148, 151
 

North American Board of Certified

 Energy Practitioners (NABCEP) ... 148, 149
 

Shingleton Design LLC ............................... 88 

State University of New York (SUNY), 

Albany – Research Foundation ..... 137, 142
 

Syracuse University .................................... 82 

NORTH CAROLINA 

Appalachian State University .................... 151 

Duke University........................................... 11
 

North Carolina A&T State University .......... 11 

North Carolina Central University ............... 11 

North Carolina State University (NCSU)/
 

North Carolina Solar Center .... 11, 148, 151
 

OHIO 

ATS Ohio, Inc. ............................................ 81 

Central State University .............................. 11 

Ferro Corporation ....................................... 81
 

First Solar, LLC ....................................... 8, 95 

MWOE Solar, Inc...................................... 238
 

Sylarus Technologies, LLC ......................... 80
 

University of Cincinnati ............................. 156 

University of Toledo .............................. 12, 96 

OREGON 

City of Portland, OR .................................. 165
 

ECO Northwest ......................................... 102
 

Home Power Magazine ............................ 151
 

PV Powered, Inc. .................................. 80, 82
 

Oregon State University ............................. 11 

University of Oregon ....................... 12, 82, 96 

PENNSYLVANIA 

Advanced Cooling Technologies, Inc. ...... 238 

Carlisle Syntec, Inc..................................... 81 

Carnegie Mellon University ....................... 154 

City of Pittsburgh, PA ............................... 165
 

Komax Systems, York ................................ 81 

Pennsylvania State University ............ 11, 155 

NAME PAGE
 

PUERTO RICO 

Universidad de Puerto Rico ...................... 155
 

SOUTH DAKOTA 

Northern Plains Power ...................... 106, 110
 

TENNESSEE 

AFG Industries ............................................ 81 

Fisk University....................................... 11, 82
 

Oak Ridge National Laboratory (ORNL) ... 219
 

Sunlight Direct, LLC .................................. 224
 

University of Tennessee............................ 224
 

TEXAS 

Alternative Energy Institute ....................... 151
 

City of Austin, TX ...................................... 165
 

Concurrent Designs .................................. 144
 

Exeltech, Inc................................................ 81
 

Sanyo Energy USA Corporation ................. 81
 

Texas A&M University ....................... 115, 155
 

Texas Tech ................................................. 12 

University of Texas at Austin..................... 156
 

University of Texas at Brownsville .............. 12 

University of Texas at El Paso .................... 12 

UTAH 

City of Salt Lake, UT ................................. 165
 

University of Utah ........................................ 96 

VERMONT 

Clean Energy Group ......................... 174, 177
 

Clean Energy States Alliance, Inc............. 177
 

VIRGINIA 

Luna Innovations ....................................... 237
 

NanoSonic, Inc..............................73, 96, 238
 

WASHINGTON 

Kearney and Associates ........................... 208
 

Pacific Northwest National Laboratory
 

(PNNL) ..................................................... 96 

REC Silicon, Inc. ......................................... 81
 

WISCONSIN 

City of Madison, WI ................................... 165
 

Midwest Renewable Energy Association .. 151
 

Thermal Energy System Specialists, Inc. 218
 

University of Wisconsin, Madison ..... 105, 196
 

247 Appendix: Performing Organizations By State/Country
Appendix: Performing Organizations By State/Country 248
 

Acronyms and Abbreviations 

A2LA American Association for Laboratory Accreditation 

AC alternating current 

AES Auger electron spectroscopy 

AFM atomic force microscopy 

AIC aluminum-induced crystallization 

AOP Annual Operating Plan 

APD antiphase domain 

APS Arizona Public Service 

AR antireflection 

ASES American Solar Energy Society 

ASHRAE American Society of Heating, Refrigeration, and Air-conditioning Engineers 

a-Si amorphous silicon 

ASOS Automated Surface Observing System 

ASRC Atmospheric Sciences Research Center (at State University of New York) 

ASRM advanced solar reflective mirror 

ASSET Analysis of State Energy Tradeoffs Databank 

ASTM American Society for Testing and Materials 

ASU Arizona State University 

BES Basic Energy Sciences (within U.S. DOE Office of Science) 

BEW Behnke, Erdman & Whitaker Engineering 

BIPV building-integrated photovoltaics 

BLM Bureau of Land Management 

BNL Brookhaven National Laboratory 

BOS balance of systems 

BSC Basic Sciences Center (within the National Renewable Energy Laboratory) 

BSF back-surface field 

Btu British thermal unit 

BU Boston University 

CAD computer-assisted design 

C-AFM conductive atomic force microscopy 

Caltech California Institute of Technology 

CBD chemical bath deposition 

CdTe cadmium telluride 

CEC California Energy Commission 

CEG Clean Energy Group, Inc. 

CET Center for Ecological Technology 

CIGS copper indium gallium diselenide 

CIGSS copper indium gallium sulfur selenide 

CIS copper indium diselenide 

CL cathodoluminescence 

CNT carbon nanotube 

COP coefficient of performance 

COSE cost of saved energy 

COTS commercial off the shelf 

CPS Corporate Planning System 

CPUC California Public Utilities Commission 

CPV concentrating photovoltaics 

CRADA Cooperative Research and Development Agreement 

Csave cost of saved energy 

CSDS Concentrating Solar Deployment System 

c-Si crystalline silicon 

CSR Climatological Solar Radiation 

249 Appendix: Acronyms and Abbreviations
 

 

CSS close-spaced sublimation 

CSP concentrating solar power 

CU University of Colorado 

CVD chemical vapor deposition 

CY calendar year 

CZ Czochralski 

DC direct current 

DEG/SE Davis Energy Group/SunEarth 

DETL Distributed Energy Technologies Laboratory (at Sandia National Laboratories) 

DFMA design for manufacturing and assembly 

DFMECA design failure mode effects and criticality analysis 

DFR design for reliability 

DJ dual junction 

DLR German Aerospace Center 

DLTS deep-level transient spectroscopy 

DMA dynamic mechanical analysis 

DNI direct normal incident 

DoD Department of Defense 

DOE Department of Energy 

DSC differential scanning calorimetry 

DSP digital signal processing 

EAO Energy Analysis Office 

EBSD electron backscatter diffraction 

EERE Energy Efficiency and Renewable Energy (U.S. Department of Energy office) 

EFG Edge-defined, Film-fed Growth 

Eg bandgap energy 

EH&S environmental health and safety 

EIA Energy Information Administration 

EM&D Electronic Materials and Devices 

ENEA Italian National Agency for New Technologies, Energy and the Environment 

EPA Environmental Protection Agency 

EPAct Energy Policy Act 

EPC Engineer, Procure, Construct 

EPS environmental portfolio standard 

EPV Energy Photovoltaics 

EUL enhanced use leasing 

EVA ethylene vinyl acetate 

EVMS Earned Value Management System 

FAQ frequently asked questions 

FF fill factor 

FFPT fixed focal point trough 

FIB focused ion beam 

FOA Funding Opportunity Announcement 

FOUP Front-Opening Unified Pod 

FR flame retardant 

FSEC Florida Solar Energy Center (at University of Central Florida) 

FTIR Fourier transform infrared 

FY fiscal year 

FZ float zone 

GB grain boundary 

GE General Electric 

GIS geographical information system 

GMS gas management system 

GO Golden Field Office (U.S. Department of Energy) 

GOES Geostationary Operational Environmental Satellite 

GPRA Government Performance and Results Act 

Appendix: Acronyms and Abbreviations 250
 

 

 

 

 

GPS 

GSE 

GSIP 

GW 

HALT 

HCE 

HBCU 

HEM 

HFSF 

HFSS 

HIPSS 

HiPerf PV 

HQ 

HRII 

HRTEM 

HSL 

HVAC 

HWCVD 

IBAD 

IC 

ICP 

ICS 

IDIP 

IEA 

IEC 

IEC 

IEEE 

IEP 

IMA 

IPO 

IPP 

IR 

IREC 

IRR 

ISES 

ISET 

ISIS 

ISO 

ISP 

IST 

ITN/ES 

ITO 

I-V 

JEDI 

JGCRI 

Jsc 

J-V 

KIESD 

kW 

kWhe 

kWht 

LACSS 

LBNL 

LCA 

LCOE 

LD 

Global Positioning System 

Global Solar Energy 

Government Solar Installation Program 

gigawatt 

highly accelerated lifetime testing 

heat collection element 

Historically Black Colleges and Universities 

heat exchanger method 

High-Flux Solar Furnace 

high-flux solar simulator 

high-intensity pulsed solar simulator 

High-Performance Photovoltaics Project 

headquarters 

High-Reliability Inverter Initiative 

high-resolution transmission electron microscopy 

hybrid solar lighting 

heating, ventilating, and air-conditioning 

hot-wire chemical vapor deposition 

ion-beam-assisted deposition 

integrated circuit 

inductively coupled plasma 

integral collector storage 

In-Line Diagnostics and Intelligent Processing 

International Energy Agency 

Institute of Energy Conversion (at University of Delaware) 

International Electrotechnical Commission 

Institute of Electrical and Electronics Engineers 

Independent Energy Producer 

impact-modified acrylic 

initial public offering 

independent power producer 

infrared 

Interstate Renewable Energy Council 

internal rate of return 

International Solar Energy Society 

International Solar Electric Technologies 

Integrated Surface Irradiance Study 

International Standards Organization 

Institute for Sustainable Power 

Industrial Solar Technology 

ITN Energy Systems 

indium tin oxide 

current voltage 

Jobs and Economic Development Impact 

Joint Global Change Research Institute 

short-circuit current 

current density voltage 

Kentucky Institute for the Environment and Sustainable Development 

kilowatt 

kilowatt hour electric 

kilowatt hour thermal 

large-area, continuous-solar simulator 

Lawrence Berkeley National Laboratory 

life-cycle analysis 

levelized cost of energy 

laser diode 

251 Appendix: Acronyms and Abbreviations
 

 

LED light-emitting diode 

LEED Leadership in Energy and Environmental Design 

LIPA Long Island Power Authority 

LOI letter of interest 

LP QCM liquid-phase quartz crystal microbalance 

MBE molecular beam epitaxy or mean bias error 

MBMDPE metallocene-based multi-density polyethylene 

mc multicrystalline 

MDC McDonnell Douglas Corporation 

MEG Multiple-exciton generation 

MLTE module long-term exposure 

MOCVD metal organic chemical vapor deposition 

MPP model power plant 

MPPT maximum power point tracking 

MSR Million Solar Roofs 

MT market transformation 

MTBF mean time between failure 

MURA Minority University Research Associates 

MW megawatt 

MYPP Multi-Year Program Plan 

MYTP Multi-Year Technical Plan 

NABCEP North American Board of Certified Energy Practitioners 

NAHB National Association of Home Builders 

NARUC National Association of Regulatory Utility Commissioners 

NASA National Aeronautics and Space Administration 

NCPV National Center for Photovoltaics 

nc-Si nanocrystalline silicon 

NEC National Electrical Code 

NEMS National Energy Modeling System (of the International Energy Agency) 

NEPA National Environmental Policy Act 

NETL National Energy Technology Laboratory 

NGO non-governmental organization 

NIR near infrared 

NIST National Institute of Standards and Technology 

NMSU New Mexico State University 

NOCT normal operating cell temperature 

NRCC Northeast Regional Climate Center 

NREL National Renewable Energy Laboratory 

NSRDB National Solar Radiation Data Base 

NSTTF National Solar Thermal Test Facility (at Sandia National Laboratories) 

NTUA Navajo Tribal Utility Authority 

NWS National Weather Service 

NYSERDA New York State Energy Research and Development Authority 

OATS Outdoor Accelerated-weathering Testing System 

O&M operations and maintenance 

OMB Office of Management and Budget 

OMCVD organometalic chemical vapor deposition 

OPV organic photovoltaics 

ORC Organic Rankine Cycle 

ORNL Oak Ridge National Laboratory 

OTF Outdoor Test Facility (at National Renewable Energy Laboratory) 

OWIP Office of Weatherization and Intergovernmental Programs 

PAE planning, analysis, and evaluation 

PBA Office of Planning, Budget, and Analysis 

PC polycarbonate 

PCD photoconductive decay 

Appendix: Acronyms and Abbreviations 252
PCU power conversion unit 

PDIL Process Development and Integration Laboratory 

PEC photoelectrochemical 

PECVD plasma-enhanced chemical vapor deposition 

PED pulsed electron-beam deposition 

PERT Performance and Energy Ratings Testbed 

PET polyethylene terephthalate 

PI principal investigator 

PIER Public Interest Energy Research (program of the California Energy Commission) 

PLD pulsed laser deposition 

PMMA polymethyl methacrylate 

PNNL Pacific Northwest National Laboratory 

PP polypropylene 

PPR polypropylene random copolymer 

PTL Photovoltaic Testing Lab (at Arizona State University) 

PV photovoltaics 

PVD physical vapor deposition 

PVME polyvinylmethylether 

PVMR&D PV Manufacturing R&D 

PVPS Photovoltaic Power Systems Programme (of the International Energy Agency) 

PVSAC Photovoltaic Systems Assistance Center 

PVSAM PV Systems Analysis Model 

PVSC Photovoltaic Specialists Conference 

PVSOL PV System Optimization Laboratory (at Sandia National Laboratories) 

QCM quartz crystal microbalance 

QD quantum dot 

QDLED quantum dot light-emitting diode 

QE quantum efficiency 

QSSPC quasi-steady-state photoconductance 

RCPCD resonant-coupled, photoconductive decay 

R&D research and development 

REAP Renewable Energy Academic Partnership 

REC renewable energy certificate 

RES Regional Experiment Station 

RFP request for proposal 

RFQ request for qualifications 

RITH roof-integrated thermosiphon 

RMOTC Rocky Mountain Oilfields Testing Center 

RMSE root mean square error 

RO reverse osmosis 

ROI return on investment 

ROWPU reverse osmosis water purification unit 

RPS renewable portfolio standard 

RSI renewable systems integration 

RSM reciprocal space map 

RT room temperature 

RTA rapid thermal annealing 

RTSE real-time spectroscopic ellipsometry 

RUS Rural Utilities Service (of the U.S. Department of Agriculture) 

SAC Solar America Cities 

SAI Solar America Initiative 

SAIC Science Applications International Corporation 

SAM Solar Advisor Model 

SAS Solar America Showcases 

SBC systems benefit charge 

SBIR Small Business Innovation Research 

253 Appendix: Acronyms and Abbreviations
 

 

 

SDA Systems-Driven Approach 

SDHW solar domestic hot water 

SDSU South Dakota State University 

SEGIS Solar Energy Grid Integration Systems 

SEIA Solar Energy Industries Association 

SEM scanning electron microscope 

SEPA Solar Electric Power Association 

SERES Southeast Regional Experiment Station (at University of Central Florida) 

SERF Solar Energy Research Facility (at National Renewable Energy Laboratory) 

SETP Solar Energy Technologies Program 

SES Stirling Energy Systems 

SHC solar heating and cooling 

SHGR Solar Hydrogen Generation Research 

SHJ silicon heterojunction 

SHW solar hot water 

SIF stress intensity factor 

SIMS secondary ion mass spectrometry 

SKPM scanning Kelvin probe microscopy 

SMIF Standard Mechanical InterFace 

SMUD Sacramento Utility District 

SNL Sandia National Laboratories 

Solar PACES Solar Power and Chemical Energy Systems 

SolarDS Solar Deployment Systems (model) 

SOW statement of work 

SPC solid-phase crystallized 

SPIE International Society for Optical Engineering 

SRCC Solar Rating and Certification Corporation 

SRP Salt River Project 

SSE Surface Meteorology and Solar Energy (a NASA project) 

SSI Shell Solar Industries 

STC Standard Test Conditions 

STCH solar thermochemical hydrogen 

S&TF Science & Technology Facility (at National Renewable Energy Laboratory) 

SUNY State University of New York 

SURFRAD Surface Radiation Budget Network 

SWH solar water heating 

SWRES Southwest Regional Experiment Station (at New Mexico State University) 

SWTDI Southwest Technology Development Institute (at New Mexico State University) 

TA technical assistance 

TBD to be determined 

TCA thermal cycle annealing 

TCC transparent conductive coating 

TCO transparent conducting oxide 

TDMS thermal-desorption mass spectrometry 

TEM transmission electron microscopy; also technical exchange meeting 

TEP Tucson Electric Power 

TES thermal energy storage 

TIO Technology Improvement Opportunity 

TMY typical meteorological year 

TOP theoretical overlay photographic 

TOU time of use 

TPD temperature-programmed desorption 

TPP Technology Pathway Partnership 

TRNSYS TRaNsient SYstem Simulation Program 

TRPL time-resolved photoluminescence 

TVA Tennessee Valley Authority 

Appendix: Acronyms and Abbreviations 254
 

 

TW 

UHV 

UL 

ULRF 

UN 

UNLV 

UNM/ME 

U of L 

UPS 

USAID 

USDA 

USGBC 

UV 

VASE 

VB 

VBM 

Voc 

VSHOT 

VTD 

WCPEC 

WGA 

WIP-I 

WMO 

WOM 

WREC 

WRR 

WVTR 

XPS 

XRD 

YDR 

ZEH 

terrawatt 

ultrahigh vacuum 

Underwriters Laboratories 

University of Louisville Research Foundation 

United Nations 

University of Nevada Las Vegas 

University of New Mexico Mechanical Engineering Department 

University of Louisville 

ultraviolet photoelectron spectroscopy 

U.S. Agency for International Development 

U.S. Department of Agriculture 

U.S. Green Building Council 

ultraviolet 

variable-angle spectroscopic ellipsometry 

valence band 

valence band maximum 

open-circuit voltage 

Video Scanning Hartmann Optical Test 

vapor transport deposition 

World Conference on Photovoltaic Energy Conversion 

Western Governors' Association 

Weatherization and Intergovernmental Program-International 

World Meteorological Organization 

weatherometer 

World Renewable Energy Congress 

World Radiometric Reference 

water vapor transport rate 

X-ray photoelectron spectroscopy 

X-ray diffraction 

yield, durability, and reliability 

zero energy homes 

255 Appendix: Acronyms and Abbreviations
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