DOE Solar Energy 

Technologies Program FY2006 

ANNUAL
 REPORT
 
 

 

 

 

 

Cover Photos 

Front cover, clockwise from upper left: 

GE manufactured this 2.4-kW PV system, which is installed on the roof of the Highlands Patrol 

HQ building at the Aspen Mountain Resort in Aspen, CO, at an elevation of 11,000 feet. Aspen 

Skiing Co., PIX14729. 

In February 2006, President George W. Bush toured UNI-SOLAR's PV manufacturing plant in 

Michigan to highlight his Solar America Initiative. United Solar Ovonic, PIX14727. 

Arizona Public Service began initial operation of a 1-MW concentrating solar power (CSP) trough 

plant in FY 2006—the first commercial CSP plant built in the United States since 1991. Arizona 

Public Service. 

This manufacturing line is at Shell Solar Industries in Camarillo, CA, a partner in the PV 

Manufacturing R&D Project. Shell Solar Industries, PIX13855. 

The Science and Technology Facility at NREL, completed in FY 2006, is a 71,000-square-foot, 

state-of-the-art facility designed to help accelerate the development and commercialization of 

promising new energy technologies. Patrick Corkery, PIX14765. 

NREL researchers use hot-wire chemical vapor deposition to produce high-efficiency PV devices 

for testing and study. Richard Matson, PIX14602. 

Back cover: 

Series of photos showing activities and events of the Solar Decathlon, which was held on the 

National Mall in Washington, D.C., during October FY 2006. Upper-right photo: Secretary of 

Energy Samuel W. Bodman (center) and Under Secretary of Energy David Garman (right) 

congratulate Jeff Lyng, a student leader of the victorious University of Colorado team. 
 

DOE Solar Energy Technologies Program 

The Solar Energy Technologies Program, within the U.S. Department of Energy's Office of Energy 

Efficiency and Renewable Energy (EERE), is responsible for developing solar energy technologies 

that can convert sunlight to useful energy and make that energy available to satisfy a significant 

portion of our nation's electricity needs in a cost-effective way. The Solar Program supports research 

and development that addresses a wide range of applications, including on-site electricity 

generation, thermal energy for space heating and hot water, and large-scale power production. 

In the body of this report, you will read about R&D and achievements from across the Solar Program. 

The work performed at the participating DOE national laboratories—National Renewable Energy 

Laboratory (NREL), Sandia National Laboratories, Oak Ridge National Laboratory (ORNL), and 

Brookhaven National Laboratory—is highlighted, along with the vital contributions of our industry and 

university partners. 

An Expanding Industry 

The recognition by the U.S. public—and our national, state, and local leaders—that domestically 

produced solar and other renewable energy options are synonymous with energy security and 

economic prosperity grows more palpable each day. The demand for solar energy systems is 

soaring. Backing that demand is a strong commitment to allocate Federal research dollars to 

continuing to advance the science underlying solar technologies and move those technologies to the 

marketplace. 

Based in large part on 30 years of accomplishments within the Solar Program's research facilities 

and partnerships, photovoltaic (PV) systems are being installed in the United States and around the 

world at a record pace. In 2006, we opened the Science & 

Technology Facility at the National Renewable Energy 

Laboratory (Fig. 1). This building represents a new paradigm 

of laboratory scientists working side by side with members of 

the PV industry to ultimately produce the most efficient and 

cost-effective PV systems possible. 

With the commissioning of Arizona Public Service’s 1-MW 

trough plant in 2006, the concentrating solar power (CSP) 

industry produced the first commercial CSP plant built in the 

United States since 1991. Following that, construction began 

on Nevada Solar One, a 64-MW trough plant (that 

subsequently went online in June 2007). Both projects use a 

solar collector that was developed collaboratively by 

Solargenix and the Solar Program. 

Fig. 1. U.S. Secretary of Energy Samuel W. Bodman (center) 

cuts the ribbon with Colorado Congressman Bob Beauprez (left) 

and Colorado Senator Ken Salazar (right) to open the DOE 

National Renewable Energy Laboratory's Science & Technology 

Facility, in Golden, CO. 

i 
Solar America Initiative 

Early in 2006, the Solar America Initiative (SAI) was announced in support of the President’s 

Alternative Energy Initiative, laying the groundwork for SAI activities to begin in FY 2007. The Solar 

Program leads and implements the SAI. 

The SAI is quite simply a new way of doing business for the Solar Program. It ramps up DOE’s 

business strategy of partnering with U.S. industry to accelerate commercialization of improved PV 

systems that can meet aggressive cost and installed capacity goals. The initiative has two areas of 

emphasis: 

•	 Research and Development focuses on PV component R&D and system designs, including lowcost approaches for manufacturing. 

•	 Market Transformation centers on non-R&D activities aimed at reducing market barriers and 

promoting market expansion and complements the core R&D and engineering activities. 

SAI will employ public-private partnerships to pursue component and system technologies. Industryled project teams will demonstrate manufacturing approaches that deliver low-cost, high-reliability 

commercial products. Ultimately, by 2015, the efforts of the SAI will contribute to making PV 

electricity cost competitive with traditional energy sources in all U.S. sectors. 

Mission and Goals 

We in the Solar Program are committed to developing solar technologies that provide the country 

with economic energy options and help U.S. industry remain the world leader in these technologies. 

Research, design, and development of technology are combined with value analysis, an integratedsystems approach, and partnering to attain the Solar Program's goals and objectives. 

Our mission is 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. Our goals are to reduce the cost of solar energy to the point that it becomes 

competitive in relevant energy markets (e.g., buildings and power plants) and for solar technology to 

reach a level of market penetration to enable a sustainable solar industry. 

Program Areas 

In FY 2006, the Solar Program consisted of three subprogram areas. The first two, Photovoltaics and 

Solar Thermal, are technical and cover five key activity areas: 

Photovoltaics 

• Fundamental Research 

•	 Advanced Materials and Devices 

• Technology Development 

Solar Thermal 

•	 Concentrating Solar Power 

•	 Solar Heating and Lighting 

The third subprogram, Systems Integration and Coordination, covered crosscutting activities that 

reflected a Systems-Driven Approach to managing the Solar Program. This subprogram provided a 

framework and the analysis tools to explore alternative pathways and identify critical technology 

needs to guide planning and management of the entire solar portfolio. 

ii 
Awards and Patents 

Among the nation's premier awards for technological innovation are those presented by R&D 

Magazine. In FY 2006, Solar Program researchers at ORNL received an R&D 100 Award for their 

hybrid solar lighting (HSL) system. The system uses a roof-mounted solar collector and small fiber 

optics to transfer sunlight to hybrid fixtures with electric lamps. A control system enables sunlight to 

power the light and illuminate about 1,000 square feet during sunny daylight hours while clouds and 

darkness allow the system to revert to providing regular electrical light. 

Developing intellectual property, and acquiring patent protection for the work, is another critical 

component of the Solar Program's role in moving technologies into the marketplace. In FY 2006, the 

Electronic Materials and Devices project at NREL led the entire laboratory in generation of new 

intellectual property, filing 12 patents, which is more than a third of all of the records of invention from 

NREL. During the year, four of the inventions reported in earlier years were granted patents. 

The Future is Now 

FY 2006 got off to a rousing start with the Solar Decathlon, which was competed in October 2005 

(Fig. 2). Following on the success of the first Solar Decathlon in 2002, the event featured teams of 

college students vying to design and build the most effective solar-powered house. With more than 

100,000 visitors touring the homes on the National Mall in Washington, D.C., and hundreds of news 

stories in national and local media, the event captured the attention of the American public. It put 

solar technologies on center stage for several weeks before, during, and after the competition. More 

to the point, the two Solar Decathlons, and the next one slated for October 2007, have opened the 

door to new technologies and a new generation of young people schooled in the ways of energyefficient building and the freedom inherent in solar-powered homes. 

Fig. 2. Early in FY 2006, hundreds of college students from the United States and around the world 

celebrated their moment in the sun at the Solar Decathlon. "Every one of these houses is a marvel of 

engineering and design, and a model of creativity and innovation," said U.S. Secretary of Energy 

Samuel W. Bodman. 

iii 
 

 

Halfway through the year came new opportunities and the beginning of an action plan for expanding 

domestic solar energy production under the Solar America Initiative. By year's end, we saw this as a 

transitional year for the Solar Program, leading to a fundamental change in our way of doing 

business for FY 2007 and beyond. 

So what do the coming years hold in store? Our plans are ambitious—and directed toward markets 

whose potential size can be measured in gigawatts rather than megawatts. We must meet levelized 

energy cost goals for solar energy that will open those markets, and the Solar America Initiative 

provides a roadmap for doing that. 

We will continue to use analytical techniques and models, based on the Systems-Driven Approach, 

to optimize our research portfolio. We will invest in partnerships with the private and public sectors, 

using the balance of near-, mid-, and long-term research and related activities that will have the most 

impact on gigawatts installed. Risk is being factored into this analysis, as well as the use of outside 

experts to ensure our analysis is robust. 

As in the past, our annual operating plan and subcontracts will contain robust milestones, as defined 

in the stage-gate model for both commercialization and research paths. But added to this will be a 

new emphasis on next-generation technology and open-ended, outside-the-box research. Workforce 

development is also a major priority to get the pipeline flowing with people who can help bring the 

technologies to the next level. 

We'll be on the lookout to knock down barriers to installing solar energy systems, such as integrating 

solar energy systems with the power grid. We want solar power to be affordable, but also easy to get 

and use. Under the Market Transformation component of the SAI, such as the Solar America Cities 

activities, we will address these issues. 

All of this is marching toward our ultimate goal of zero energy homes and buildings that are selfcontained and self-sustaining from an energy perspective. We have them now, but they are not yet 

affordable. Our goal is to improve the efficiency of the building by 70% so the solar power goes 

further. 

Based on 30 years of success, we are fortunate to be here at the right time and place. We plan to 

get more and more solar out there—for energy security and to make a huge difference in the future 

for climate change. 

Steven Chalk 

Solar Energy Technology Program Manager (acting) 

Office of Energy Efficiency and Renewable Energy 

U.S. Department of Energy 

iv 
 

DOE Solar Program FY 2006 Annual Report Table of Contents 

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

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

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

Measurements and Characterization ........................................................................................ 4 

Solar Resource Characterization............................................................................................. 20 

Environmental Health and Safety............................................................................................ 24 

Crystalline Silicon Project........................................................................................................ 28 

Electronic Materials and Devices ............................................................................................ 34 

High-Performance Photovoltaics............................................................................................. 44 

Advanced Materials and Devices ............................................................................................... 51
 

Thin Film PV Partnership......................................................................................................... 52 

PV Module Reliability R&D...................................................................................................... 62 

Inverter and BOS Development............................................................................................... 66 

PV Manufacturing R&D ........................................................................................................... 70 

Technology Development ........................................................................................................... 79 

PV System Evaluation and Optimization................................................................................. 80 

PV Systems Engineering and Performance............................................................................ 84 

Domestic PV Applications ....................................................................................................... 88 

PV Systems Analysis............................................................................................................... 91 

Building-Integrated Photovoltaics............................................................................................ 95
 

Million Solar Roofs Initiative .................................................................................................. 100 

Regional Experiment Stations ............................................................................................... 103 

Solar Thermal R&D Subprogram Overview.......................................................................................... 107 

Concentrating Solar Power....................................................................................................... 111
 

Dish/Engine System R&D...................................................................................................... 112
 

Parabolic Trough R&D........................................................................................................... 115 

Advanced Optical Reflector R&D .......................................................................................... 125 

CSP Systems Analysis .......................................................................................................... 129 

Solar Heating and Lighting ....................................................................................................... 133 

Low-Cost Polymers ............................................................................................................... 134 

Materials Durability ................................................................................................................ 139 

Industry Manufacturing Assistance ....................................................................................... 142 

Hybrid Solar Lighting ............................................................................................................. 145 

Systems Integration and Coordination................................................................................................. 151 

Systems-Driven Approach ........................................................................................................... 153 

Communications and Outreach ................................................................................................... 159 

International Activities .................................................................................................................. 165 

Process Integration, Capital Equipment, and Facilities ............................................................... 168 

v 
EERE Crosscutting Activities ................................................................................................................ 173 

Small Business Innovation Research ...................................................................................... 175 

Congressionally Directed Projects 

Conductive Coatings for Solar Cells Using Carbon Nanotubes ..................................... 179 

Dynamic Shading System with Integrated Concentrator Solar Module.......................... 182 

Missouri Alternative and Renewable Energy Technology Center .................................. 183 

Carbon Nanostructure-Based Screens for PV Panels.................................................... 184 

Tools for Nanotechnology Education Development Program......................................... 185 

PV Charging System for Remote Area Operations ........................................................ 186 

Brightfield Solar Energy .................................................................................................. 187 

National Orange Show Photovoltaics Demonstration..................................................... 188 

Photonics Research and Development........................................................................... 189 

Appendices 

Performing Organizations by Name............................................................................................. 191 

Performing Organizations by State .............................................................................................. 193 

Acronyms and Abbreviations ....................................................................................................... 197 

vi 
 

 

 

Photovoltaic R&D Subprogram Overview 

Richard J. King, Team Leader, Photovoltaic R&D 

The majority of the Photovoltaic Subprogram’s activities are carried out through two primary 

research centers: the National Renewable Energy Laboratory (NREL) in Golden, CO, and Sandia 

National Laboratories (SNL), in Albuquerque, NM. Brookhaven National Laboratory (BNL), in 

Upton, Long Island, NY, provides program support in the area of environmental health and safety. 

NREL, SNL, and BNL are all partners in the National Center for Photovoltaics (NCPV), which 

provides guidance to DOE PV research efforts. In addition, the DOE Golden Field Office (GO), in 

Golden, CO, administers and manages contracting activities assigned by headquarters. 

PV Subprogram research is focused on increasing domestic capacity by lowering the cost of 

delivered electricity and improving the efficiency of modules and systems. We emphasize longterm innovative research, thin-film development, manufacturing R&D, and systems development 

and reliability. Long-term research is focused on “leapfrog” technologies such as polymers and 

nanostructures. In thin films, new levels of efficiency and stability in prototype modules have 

been achieved, as well as higher laboratory cell efficiencies. Near-term research is focused on 

reducing cost through manufacturing advancements and by improving system reliability. 

Goals and Objectives 

The goals of the PV Subprogram follow the lead of the Solar America Initiative. The aim is to 

reduce the cost of PV technologies to the point that PV-generated electricity is cost competitive 

with conventional electricity sources by 2015. Specifically, the 2015 PV goals are to reduce costs 

to 8¢–10¢/kWh in the residential sector, 6¢–8¢/kWh in the commercial sector, and 5¢–7¢/kWh in 

the utility sector. Achieving these goals will require reducing installed PV system costs by 50%– 

60% between 2005 and 2015, from $5.5–$8.50/Wp to $2.25–$3.50/Wp in 2005 U.S dollars. 

Results and Accomplishments 

July 7, 2006, marked the ribbon-cutting ceremony for NREL's new Science & Technology Facility. 

The 71,000-square-foot, state-of-the-art facility is designed to help accelerate the development 

and commercialization of promising new energy technologies, particularly in solar, hydrogen, and 

building-related energy technologies. The facility has space for 75 full-time researchers and 

features an 11,500-square-foot Process Development and Integration Laboratory, which will allow 

NREL and industry researchers to work together to develop new PV manufacturing processes. 

This cooperative research will help reduce the time it takes to move new technologies from the 

laboratory bench to commercial manufacturing. 

In existing research areas, laboratory researchers made rapid performance improvements on a 

variety of fronts. Crystalline silicon heterojunction solar cells with amorphous silicon (a-Si:H) 

layers were deposited by hot-wire chemical vapor deposition. The research team achieved an 

NREL-confirmed conversion efficiency of 17.83% for a 1-square-centimeter cell with both a front 

heterojunction emitter and a back heterojunction contact fabricated entirely below 200°C at 

NREL. This is the best published cell efficiency on a p-type Si wafer by the a-Si:H/c-Si 

heterojunction technology. Researchers also fabricated high-efficiency (19.52% confirmed) 

copper indium gallium diselenide (CIGS)-based solar cells using a single-layer, NREL-developed, 

chemical-bath-deposited CdZnS buffer layer. NREL has been the world leader in fabricating the 

most efficient CIGS thin-film solar cells since 2002. 

Boeing Spectrolab demonstrated a 40.7%-efficient GaInP/GaInAs/Ge cell that was verified by 

NREL at 236 suns. Researchers have been working toward the "40% barrier" for the past two 

decades. In the 1980s, multijunction solar cells achieved about 16% efficiency, and NREL broke 

the 30% barrier in 1994. Today, most satellites use these multijunction solar cells, and 

1 Photovoltaic R&D
 

Spectrolab, a subsidiary of The Boeing Company, recently produced its two millionth solar cell 

using this multijunction technology. The new Spectrolab cell, developed with DOE funding, could 

lead to more affordable solar power systems, costing as little as $3/watt to install and producing 

electricity at a cost 8¢ to 10/¢kWh. 

The Thin Film PV Partnership supported manufacturing advances of key thin-film technologies 

during the fiscal year. This is viewed as the Partnership’s 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 of technologies that have been successfully 

developed by DOE funding to the private sector. Two Technology Partners expanded 

manufacturing facilities in the United States (First Solar 85 MWp and Uni-Solar 60 MWp). A third 

Technology Partner, Global Solar, announced plans to expand in 2007. Production of thin films in 

the United States grew from 12 MWp in 2003 to an estimated more than 70 MWp in 2006. 

The PV Manufacturing R&D Project completed the development (achieved manufacturing-lineready status) of at least three in-line diagnostic processes initiated in FY 2002 awards from "InLine Diagnostic, Intelligent Processing (IDIP) Solicitation." At least five of the U.S. PV industry 

partnerships involved in the IDIP solicitation reported a minimum of 22 in-line diagnostic 

processes that have been implemented on U.S. PV production lines. 

Solar Program staff members are also active participants in developing the codes and standards 

so critical to the safety and consumer acceptance of PV systems. As part of this work, the 2005 

National Electrical Code was published with the 42 changes proposed by the SNL “Industry 

Forum” with new allowances for ungrounded PV arrays and improved disconnect requirements. 

In California, one the world's largest markets for PV systems, the Los Angeles Department of 

Water and Power revised its solar energy rebate program from one providing a rebate amount 

based on system size to one based on the estimated energy output predicted by NREL's 

PVWATTS model. Consequently, rebate amounts will now depend on parameters that determine 

energy production: size, tilt, azimuth, fixed or tracking, and location of the PV system. 

Professional Recognition 

A mark of the impact of a research group is the contribution its members make to the broader 

scientific community. Scientists, researchers, and managers within the NCPV are active, working 

members of numerous professional organizations and are widely recognized for their roles. Citing 

only a few examples from 2006, Sally Asher was elected a chair of the Applied Surface Science 

Division of the American Vacuum Society (AVS) and is program committee co-chair for the 54th 

AVS International Symposium. Pete Sheldon was elected a director of the AVS. David Ginley 

served as general chair of the Fall 2005 Materials Research Society Meeting; subsequently he 

was selected to be secretary of the society. Timothy Coutts served as program chair of the 4th 

World Conference on Photovoltaic Energy Conversion; he has been selected to be general chair 

of the 33rd IEEE Photovoltaics Specialists Conference. 

Finally, Lawrence Kazmerski received two prestigious awards in 2006. Pennsylvania State 

University honored him with the Nelson W. Taylor Award for Materials Science. He also received 

the World PV Award at the Fourth World Conference on Photovoltaic Energy Conversion for his 

outstanding contributions to the worldwide advancements of PV science and technology. The 

award, sponsored by professional organizations from the European, Asian-Pacific Rim, and U.S. 

PV communities, recognizes superior and sustained leadership in solar photovoltaics. Kazmerski 

is director of the NCPV and was the first staff member hired to do PV research for NREL's 

predecessor, the Solar Energy Research Institute. 

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 2006 marked a host of accomplishments in the Fundamental Research area, including: 

Measurements and Characterization 

•	 Provided measurement support in the areas of analytical microscopy, surface analysis, 

electro-optical characterization, and cell and module performance to more than 70 PV 

research partners in industry, academia, and NREL. 

•	 Maintained International Standards Organization accreditation for primary and secondary cell 

and module calibrations. 

•	 Relocated staff and characterization labs (Surface Analysis, Electro-Optical Characterization, 

and Analytical Microscopy areas) to the new Science and Technology Facility. 

Solar Resource Characterization 

•	 Completed a draft 15-year National Solar Radiation Data Base (NSRDB) and distributed for 

review. Completed plan for final NSRDB update and began final validation and production. 

Environmental Health and Safety 

•	 Promoted and established international collaborative life-cycle environmental assessments of 

PV energy technologies, enhancing the quality and quantity of PV environmental 

assessments. 

Crystalline Silicon Project 

•	 Achieved a record efficiency for p-wafer silicon heterojunction solar cells with a confirmed 

efficiency of 18.2%. This 1 cm2

 cell has a-Si contacts on both sides and an open-circuit 

voltage of 0.667 V. 

•	 Modeling showed that 18%–20%-efficient low-cost cells with screen-printed contacts using 

100 to 200 μm-thick c-Si wafers can reduce the levelized cost of electricity to 5–10 ¢/kWh. 

Ele tronic Materials and Devices c 

•	 Applied for six patents on the direct printing of precursors for CIS solar cell absorbers and 

metallization for Si solar cell contacts. 

•	 Achieved 19.52%-efficient CIGS/CdZnS solar cell; 17.1%-efficient, 1-μm, thin CIGS solar cell; 

and 15.02%-efficient thin CdTe solar cell. 

Hig h-Performance Photovoltaics 

•	 The Institute of Energy Conversion demonstrated an 11.9% CIGSS (1.5 eV) top cell material 

of the polycrystalline thin-film tandem. 

•	 Boeing Spectrolab demonstrated a 40.7%-efficient GaInP/GaInAs/Ge cell that was verified by 

NREL at 236 suns. 

3

Photovoltaic R&D

Fundamental Research
 

 

 

____________________________________________________________________________ 

 

 

 

 

Measurements and Characterization 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Peter Sheldon, 303-384-6533, peter_sheldon@nrel.gov 

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

FY 2006 Budget: $6,728K 

Objectives 

•	 Provide routine and specialized measurement and characterization support for 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 our International Standards Organization (ISO) accreditation for primary and 

secondary cell and module calibrations. 

•	 Completed capability to evaluate multiple-junction concentrator cells and modules to 1000X with 

lowest possible uncertainty. 

•	 Investigated the structural properties of site-selected c-Si/a-Si interfaces in Si heterojunction cells 

with new record efficiencies. 

•	 Investigated local open-circuit voltage (Voc) and local current flow in amorphous and 

nanocrystalline mixed-phase silicon solar cells. 

•	 Conducted study correlating composition and structure of moisture barrier layers grown on 

flexible substrates with growth conditions, water vapor transport rates, and adhesion properties. 

•	 Studied the reaction kinetics of nanoscale CuxTe films, an important component of back contacts 

in CdTe-based devices. 

• Organized the 16th Workshop on Crystalline Silicon Solar Cell & Modules: Materials and 

Processes.
 

•	 Developed models to help understand crack propagation and wafer breakage in Si wafers. 

• Applied spectroscopic ellipsometry to facilitate improvement of Si heterojunction solar cells. 

•	 Relocated staff and characterization labs (Surface Analysis, Electro-Optical Characterization, and 

Analytical Microscopy areas) to the Science and Technology Facility (S&TF). Fitted up new 

laboratories and restored to operational status. 

Future Directions 

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

performance, electro-optical characterization, and surface analysis to at least 70 PV research 

partners in industry, academia, and NREL. 

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

•	 Develop integrated plan to provide priority support to Solar America Initiative (SAI) Technology 

Pathway Partnership (TPP) awardees that meets their R&D needs within the context of available 

resources. 

•	 Investigate the atomic structure of the c-Si/a-Si interface and the thickness and crystallinity of the 

a-Si layer in Si heterojunction cells as a function of cell processing conditions. 

•	 Develop luminescence mapping capability for industrial silicon wafers. 

Photovoltaic R&D

Fundamental Research

4
 

 

____________________________________________________________________________ 

 

 

 

 

• Organize the 17th Workshop on Crystalline Silicon Solar Cell & Modules: Materials and 

Processes: identify priority R&D issues for the Si PV industry.
 

•	 Improve understanding of CdTe back contact reaction kinetics by developing a quantitative model 

for surface-segregation phenomena. 

•	 Investigate materials chemistry of copper indium gallium diselenide (CIGS) on flexible substrates, 

leading to an improved understanding of long-term reliability. 

•	 Complete study of the kinetics of microcrack propagation and improve our understanding of how 

thermal profiling and mechanical stresses, associated with conventional processing, impact 

propagation. 

•	 Assess the technical shortcomings of minority-carrier lifetime measurement techniques used to 

determine material quality of mc-Si; apply improved understanding to facilitate better 

measurements of material quality for the PV industry. 

•	 Develop enhanced cell and module measurement capabilities that improve measurement turnaround time and uncertainty necessary to support the SAI (requires capital equipment funding). 

1. Introduction 

The Measurements and Characterization Division 

provides test, measurement, and analysis support 

and research for the National Photovoltaics 

Program. It supports all 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 project assists 

clients with the test and analysis of thousands of 

materials and device samples, helping them to 

understand and direct work on their research and 

commercial product development. 

These activities address one or more of the three 

areas crucial to meeting the 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/module reliability. This is accomplished by 

selecting projects that address key issues for a 

broad spectrum of technologies, including c-Si, aSi, thin Si, copper indium diselenide (CIS), CdTe, 

III-Vs, and future-generation materials. 

Fig. 1. Schematic showing Measurements and 

Characterization research areas of emphasis. 

As shown in Fig. 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. 

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 non-support research 

activities pursued in FY 2006 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. Nevertheless, 

during the past year, we have collaborated with 

well over 70 research groups from industry, 

universities, and national laboratories. FY 2006 

priority milestones in each task are listed below. 

2.1 Analytical Microscopy Task 

•	 Investigate the structural properties of siteselected c-Si/a-Si interfaces in recordefficiency Si heterojunction cells. 

•	 Investigate local Voc and local current flow in 

amorphous and nanocrystalline mixed-phase 

silicon solar cells. 

•	 Complete investigation of screen-printed 

contacts on industrial Si Cells. 

5

Photovoltaic R&D

Fundamental Research
 

 

 

 

 

 

 

 

 

•	 Commission a focused ion beam (FIB) 

workstation and develop transmission electron 

microscopy (TEM) sample preparation 

techniques for PV thin films. 

•	 Relocate a portion of research operations to 

the S&TF. 

A summary of progress on these milestones is 

outlined in section 3.1. 

2.2 Cell and Module Performance Task 

•	 Complete capability to evaluate multiplejunction concentrator cells and modules to 

1000X with lowest possible uncertainty. 

•	 Maintain ISO 17025 accreditation for primary 

and secondary cell and module measurements. 

A summary of progress on these milestones is 

outlined in section 3.2. 

2.3 Electro-Optical Characterization Task 

• Organize the 16th Workshop on Crystalline 

Silicon Solar Cell & Modules: Materials and 

Processes. 

•	 Develop models to help understand crack 

propagation and wafer breakage in Si wafers. 

•	 Apply spectroscopic ellipsometry to facilitate 

development of improved Si heterojunction 

solar cells. 

•	 Relocate a portion of research operations to 

the S&TF. 

A summary of progress on these milestones is 

outlined in section 3.3. 

2.4 Surface Analysis Task 

•	 Study relationship between moisture barrier 

deposition fundamentals and ultimate barrier 

performance characteristics. 

•	 Study the reaction kinetics of nanoscale 

CuxTe films. 

•	 Conduct studies of wet-chemical processing of 

PV material surfaces leading to better control 

of deposition processes. 

•	 Design and specify a cart-based Auger 

electron spectroscopy tool for use at S&TF. 

•	 Relocate a portion of research operations to 

the S&TF. 

A summary of progress on these milestones is 

outlined in section 3.4. 

Budget allocations by task are provided below. 

Task Title FY 2006 

Budget ($K) 

Analytical Microscopy 1,708 

Cell and Module Performance 1,268 

Electro-Optical Characterization 1,692 

Surface Analysis 1,380 

Management/Maintenance 680 

3. Results and Accomplishments 

Research results outlined in this section address 

only FY 2006 priority milestones, which represent 

only a portion of all support and research activities 

within the division. A more complete summary of 

all division research activities can be found in our 

bimonthly reports. Highlights for each task are 

outlined below. 

3.1 Analytical Microscopy Task 

Investigation of the structural properties of siteselected c-Si/a-Si interfaces in Si heterojunction 

cells with new record efficiencies: 

In collaboration with NREL’s Si Group, the 

structural properties of site-selected c-Si/a-Si 

interface in Si heterojunction (SHJ) cells with new 

record efficiency of 18.2% were investigated. 

These cells have the best published cell efficiency 

in a p-type Si wafer by the a-Si:H/c-Si 

heterojunction technology and exceeds NREL’s 

FY 2006 AOP milestone of 18%. The 

improvement over the previous best cell (17.8%) 

results mainly from achieving a thinner amorphous 

silicon emitter that reduces parasitic absorption 

losses. 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 FIB and high-resolution transmission 

electron microscopy (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 2(a) is a scanning electron microscope 

(SEM) image of a site-selected cross-sectional 

TEM foil made from a 18.2% Si device, showing 

three different areas: (112) facets, (111) top, and 

(111) bottom. These three areas correspond to the 

textured surface structure. The Ag layer is the 

contact layer. Figure 2(b) is a HRTEM image from 

a (112) facet area, showing that the a-Si layer is 

very uniform and around 4.2 nm thick, which is 

much thinner than that in the previous record Si 

cells (about 5–6 nm). Figure 2(c) is a HRTEM 

image taken from a (111) top area. The dashed 

line indicates the location of the a-Si layer. 

However, the a-Si layer is not seen. Instead of an 

a-Si/c-Si interface, an In2O3/c-Si interface is 

observed. The HRTEM images taken from the 

(111) bottom areas showed similar features. 

In summary, we developed an approach that 

enables thinner a-Si layers than in previous SHJ 

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Si cells, resulting in higher efficiency devices. In 

the (112) facet areas, the a-Si layer is uniform in 

thickness and the c-Si/a-Si:H interface is 

atomically abrupt. However, the a-Si layers at the 

top and bottom (111) facet regions are not clear 

and no abrupt a-Si/c-Si interfaces were observed, 

providing guidance for future cell improvement. 

Fig. 2. (a) SEM image of a site-selected crosssectional TEM foil made from a Si cell with 18.2% 

efficiency, showing three different areas: (112) 

facets, (111) top, and (111) bottom; (b) HRTEM 

image from a (112) facet area; (c) HRTEM image 

taken from a (111) top area. 

Investigate local Voc and local current flow in 

amorphous and nanocrystalline mixed-phase 

silicon solar cells: 

Amorphous silicon (a-Si:H) solar cells made close 

to the transition from amorphous to nanocrystalline 

phases, but still in the amorphous regime, show 

an improved initial performance and stability. On 

the other hand, nanocrystalline silicon (nc-Si:H) 

solar cells made close to the transition, but in the 

nanocrystalline regime, also show good 

performance. The devices made in the transition 

region are called mixed-phase solar cells. In 

collaboration with United Solar, Inc., we have 

measured the microelectrical properties of local 

Voc and local current flow in the mixed-phase n-i-p 

silicon solar cells by scanning Kelvin probe 

microscopy (SKPM) and conductive atomic force 

microscopy (C-AFM). Figure 3 shows the SKPM 

electrical potential and AFM topographic images, 

and a line profile of the Voc distribution along the 

arrow shown in Fig. 3(a). 

From both the SKPM and AFM images, we 

observed that the nc-phases aggregate in the aSi:H matrix. Each aggregate is ~500 nm in size 

and contains many small nanometer-sized grains. 

Under illumination of 1.85 eV laser light, reduced 

Voc is observed when probing the nc-Si:H 

aggregates. Voc gradually increases, over a 

distance of 1 μm, as one probes farther away from 

the aggregate into the surrounding a-Si:H matrix. 

The minimum Voc values in the nc-Si:H 

aggregates, in the mixed phase, is larger than the 

Voc of the nc-Si:H single-phase device. This and 

the Voc changes observed could be caused by 

charge redistribution near the a-Si:H/nc-Si:H 

boundary in the i-layer bulk. Although there is 

some lateral electrical interaction, a clear 

distinction between the amorphous and 

nanocrystalline regions has been observed. 

We also measured local current flow or local 

conductivity by using C-AFM. We found that the 

local current value of the nc-Si:H phase is much 

larger than that of the surrounding a-Si:H matrix, 

and the transition interface between the high and 

low currents is sharp. The forward biased C-AFM 

images show that the current is very low over the 

entire surface of the fully a-Si:H region. High 

current spikes are observed in the mixed-phase 

region, where the current spikes correspond to ncSi:H aggregates. The density of the current spikes 

increases from the mixed phase to the heavy ncSi:H regions. A thick a-Si:H buffer layer, inserted 

between the p and i layer, significantly reduced the 

magnitude of the current spike in the nc-Si:H 

region. The C-AFM and the SKPM measurements 

suggest that the mixed-phase cells can be 

considered as a two-phase, parallel-connected 

diode structure. 

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Fig. 3. (a) SKPM image and (b) the corresponding 

AFM image taken on a-Si:H and nc-Si:H mixedphase solar cells. (c) is an example local Voc line 

profile along the arrows in (a), as deduced from 

the SKPM measurement. 

Electron backscatter diffraction (ESBD) studies of 

thin-film Si: 

EBSD is based on the fully automated acquisition 

of diffraction patterns produced by backscattered 

electrons under diffraction conditions in scanning 

electron microscopy. EBSD provides maps of the 

orientation of crystalline phases with very high 

resolution and can be used to investigate the 

misorientation of individual grain boundaries 

(GBs), identification of special boundaries, grain 

distribution, preferential orientation, deformation, 

and strain. 

In collaboration with NREL’s Si Group, we have 

investigated the microstructure of Si thin-film 

devices as a function of deposition and postdeposition processing conditions. These films are 

based on the recrystallization of amorphous silicon 

films in the solid phase. We studied the impact of 

rapid thermal annealing (RTA) and hydrogen 

passivation. The RTA was performed at 900°C for 

4 minutes, while the hydrogen passivation was 

carried out at 550°C. We performed EBSD 

measurements on both the aluminum-induced 

crystallization (AIC) seed layers and the epilayers 

at different stages of the processing (1) after 

deposition, (2) prior to post-deposition treatments, 

(3) after RTA, and (4) after hydrogen passivation. 

Figure 4 illustrates the results of the EBSD 

measurements for the AIC seed layer prior to postdeposition treatments. A map of the band contrast 

calculated from the diffraction pattern reflects the 

microstructure of the film far better than standard 

secondary-electron imaging. Below this, a map 

shows the grain boundary distribution. To the 

right, the orientation maps along the in-plane and 

out-of-plane directions are shown. 

Fig. 4. (Top left) The microstructure of an Alinduced crystallized Si seed layer. (Bottom left) 

Map outlining the grain boundaries. Orientation 

maps along the in-plane (X) and out-of-plane (Z) 

directions are shown in the top right and bottom 

right, respectively. 

Prior to post-deposition treatments, the seed layer 

exhibits nearly perfect bimodal distribution toward 

<100> and <111>, as indicated by the pole 

figures. We find that most of the GBs on the 

orientation map are Σ3 and Σ9. These are 

twinning boundaries and they are regarded as 

intra-grain boundaries. After these special 

boundaries are dismissed, grain diameters in the 

10-μm range are standard for the seed layer. The 

epilayer develops larger grains than the underlying 

seed layer and is preferentially oriented toward 

<100>; the domains remaining <111>-oriented 

result from twinning. 

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After RTA, the seed layer shows the <100>/<111> 

bimodal distribution. The RTA treatment 

stimulates the generation of twinning boundaries 

and other boundaries in what seems to be 

previously well-developed grains, resulting in 

smaller grains. On the epilayer, the angle spread 

along <100> is slightly higher than before RTA, 

suggesting local recrystallization. After hydrogen 

passivation, the bimodal distribution in the seed 

layer is not as well defined as before. The results 

for the epilayer after hydrogen passivation are 

similar to those obtained after RTA. 

Investigate screen-printed contacts on industrial Si 

cells (in collaboration with BP Solar, Ferro, and 

Applied Materials): 

SKPM and C-AFM, combined with SEM, were 

used to investigate the firing temperature effect on 

cast Si solar cells with screen-printed Ag front 

contacts and Al back surface field (Al-BSF). We 

analyzed samples with firing temperatures lower 

and higher than the estimated optimal 

temperature. For the samples with low firing 

temperatures, the SKPM measurements indicate 

that the p-n junction is located 400 nm below the 

surface of the wafer. Both under and beside the 

screen-printed Ag contact, the electric field 

induced by a reverse bias voltage of –1 V is 

1.1E4 V to 1.4E4 V/cm and spreads over 900 to 

1100 nm. In comparison, for the samples with the 

high firing temperatures, the p-n junction is located 

500 nm below the surface of the wafer and the 

electric field induced by a –1 V bias voltage is 

1.3E4 V to 1.6E4 V and spreads over 1100 to 

1500 nm. The C-AFM combined with SEM 

analysis of the Ag/Si interface reveals that the bulk 

of the screen-printed contact consists of a mixture 

of conductive (Ag) and insulating (glass frit) parts. 

Further, SEM analysis using the doping contrast 

mode were performed to investigate the depth of 

the Ag penetration toward the p-n junction and to 

confirm the location of the p-n junction. For the 

low-firing-temperature samples, SKPM 

measurements at the Al-BSF side indicate a p/p+ 

junction 200 nm below the Al/Si interface. Under a 

forward-bias voltage of 1 V, the electric field 

induced at this junction is 1E4 V/cm. These data 

are being used to help formulate improved 

contacting inks and optimize firing parameters to 

yield higher performance contacts. 

Commission a focused ion beam (FIB) work 

station and develop TEM sample preparation 

techniques for PV thin films: 

We have commissioned a FEI Nova 200 NanoLab 

dual-beam SEM/FIB. This dual-beam instrument 

consists of an FIB column and a SEM column on 

the same platform. Supporting other analytical 

tools such as TEM, the dual-beam FIB performs 

precise, site-specific sample preparation for both 

TEM and SEM. This technique allows the 

preparation of electron transparent TEM samples 

from thin-film/substrate material combinations that 

were either extremely difficult or not possible using 

previous preparation techniques. 

3.2 Cell and Module Performance Task 

Complete capability to evaluate multiple-junction 

concentrator cells and modules to 1000X with 

lowest possible uncertainty: 

The capability of the Spectrolab high-intensity 

pulsed solar simulator (HIPSS) has been 

enhanced, by expanding the current ranges; 

spectral adjustment (through lamp voltage 

adjustment); and intensity adjustment (through 

variable apertures). The test device's current 

range was expanded to 0.1A–60A full scale, and 

the single fixed-range reference cell channel was 

expanded to two reference cell channels with 

current ranges from 0.005A to 2A. This allows the 

I-V characteristics to be measured from 1 sun to 

2,000 suns for all PV technologies of interest. 

Other options were also investigated to enhance 

the test bed capabilities, such as modifying the 

sweep circuit to be able to reverse the sweep 

direction to detect bias rate artifacts or using filters 

to further adjust the spectrum. The spatial 

nonuniformity was also mapped to understand and 

minimize uniformity-related error sources. A 

stage-gate analysis was performed with the 

conclusion that additional funds for a spectrally 

adjustable solar simulator would be required to 

further reduce the uncertainty for high-efficiency 

cell designs where the current matching of more 

than the top two junctions is required. 

Maintain ISO 17025 accreditation for primary and 

secondary cell and module calibrations. Complete 

periodic audits, maintenance of quality systems, 

calibrations, softwar,e 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 reference cells and 

modules they use to measure their products. 

Certified module-qualification facilities such as 

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Arizona State PV Testing Laboratory and Florida 

Solar Energy Center (FSEC) 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 world 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. 

This process took two years to complete and 

involved establishing a very structured quality 

system, detailed work procedures, 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. 

Fig. 5. NREL A2LA accreditation certificate 

#2236.01 

Other activities in support of the DOE PV program: 

PV cell and module calibration service. Performed 

5,285 standardized spectral responsivity, linearity, 

and current-versus-voltage calibrations on 1,620 

different cells and modules of all technologies in 

support of the DOE PV program. Thirteen 

concentrator prototype modules from six 

companies were evaluated, generating more than 

77,592 current-versus-voltage curves with 

accompanying irradiance and other meteorological 

data. Direct-beam spectra also accompany the 

data set for 15 sunny days. 

Consolidated concentrator cell characterization 

activities from two buildings to a single laboratory, 

leading to improved operational efficiencies. 

American Society for Testing and Materials 

(ASTM) and International Electrotechnical 

Commission (IEC) standards – Attended 

committee meetings and participated in standards 

development. Shepherded standards for linearity 

determination, rating concentrator modules and 

systems, and spectral responsivity measurements. 

Underwriters Laboratories (UL) Cooperative 

Research and Development Agreement – UL 

approached NREL and requested assistance in 

performing portions of Module Qualification and 

Certification tests. Customers requesting 

certification interact with UL. NREL performs tests 

for UL. The Cell and Module Performance group 

performs all current-voltage (I-V) measurements 

required at various stages of test sequence. This 

required that the capability be developed to 

measure following IEC standards 61646 and 6215 

to measure the I-V characteristics at 0.2 suns and 

at normal operating cell temperature (NOCT). 

Options for measuring module 

coefficients outdoors following 

standards were also evaluated. 

temperature 

IEC 60904 

3.3 Electro-Optical Characterization 

Organize the 16th Workshop on Crystalline Silicon 

Solar Cell & Modules: Materials and Processes: 

The 16th Workshop on Crystalline Silicon Solar 

Cells and Modules was held in Denver, Colorado, 

August 6–9, 2006. Participants came from 14 

different countries and the workshop was attended 

by 157 scientists and engineers from 39 research 

institutions, DOE HQ and GO, 34 international PV 

and semiconductor companies, and two DOE 

national laboratories (SNL and NREL). 

The 3.5-day workshop is geared to help the PV-Si 

industry by (1) bringing together the industry, 

research, and academic communities, (2) 

disseminating scientific and technical information 

by nurturing collective views on critical research 

areas, and (3) providing feedback to NREL/DOE 

on important research tasks, as perceived by the 

PV community. This is achieved at the workshop 

through a combination of oral presentations by 

invited speakers, poster presentations, and 

discussion sessions. This year’s sessions 

reviewed recent advances in crystal growth 

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technologies, impurities and defects in 

semiconductors, feedstock issues, solar cell 

processing, thin-film Si and heterojunction 

devices, solar cell metallization, and module 

reliability issues. The theme of the workshop— 

“Getting More (Watts) for Less ($i)”—reflected the 

growing need for maximizing the use of silicon to 

obtain the largest amount of PV energy. A rump 

session, “Toward 100 μm Wafer Thickness and 

Beyond,” was held on the evening of August 6, 

which allowed attendees to discuss the issues and 

potential solutions to reducing the wafer thickness 

for increased cell efficiency and lower Si 

consumption. 

Develop models to help understand crack 

propagation and wafer breakage in Si wafers: 

Wafer breakage is the most crucial issue in current 

commercial, low-cost solar cell production 

because typically about 10% of the wafers break 

during cell fabrication. It is now recognized that 

wafer breakage primarily arises because of the 

presence of microcracks either on the edges or 

the surfaces of the wafer. Figure 6 is a SEM 

micrograph of a crack typically seen on the edge 

of a wire-sawn and textured PV-Si wafer. Similar, 

but typically smaller, microcracks also exist on the 

wafer surfaces. Stresses produced by wafer 

handling or cell processing can propagate an 

existing crack or initiate (and then propagate) a 

new crack. 

Fig. 6. A SEM photograph of a microcrack in wiresawn and textured multicrystalline PV-Si wafer. 

We have developed a new technique for screening 

wafers that have fatal cracks. In this technique, 

controlled stresses (representative of those 

experienced by a wafer during cell fabrication) are 

applied to a wafer to determine the propensity of 

the wafer for breakage. We have built a 

rudimentary machine to establish a proof of 

concept. Initial results are very positive. The 

wafer-screening machine is also an excellent tool 

for performing experiments to understand the 

mechanics of wafer breakage, the focus of our 

current work. Experimental results obtained in this 

machine can be combined with theoretical 

modeling to learn how microcracks propagate 

under various stress distributions produced by 

wafer processing, handling, and encapsulation. 

Because wafer breakage is directly related to the 

kinetics of microcrack propagation, we are 

developing a theoretical model, which can be used 

to investigate propagation of microcracks under 

various stress distributions that are prevalent in 

solar cell processing. Such stress distributions 

occur in wafer handling (using various pick and 

place methodologies) and during high-temperature 

solar cell fabrication steps. 

The new modeling software is a combination of a 

thermal modeling program that we developed for 

the study of dislocation generation by thermal 

stresses in silicon and the COMSOL Multiphysics, 

finite element modeling package. Figure 7 

illustrates calculated results from this model. 

Figure 7a shows von Misses stress distributions 

around a microcrack of 2 μm, in a 125-mm x 

125-mm silicon wafer under a tensile stress of 

100 MPa. It is seen that large stresses exist near 

the crack tip. Figure 7b shows stress distributions 

for a 20-μm crack. The calculated stress intensity 

factor (SIF) values for the crack sizes of 2 μm and 

20 μm are 0.28 MPa m1/2 and 0.98 MPa m1/2, 

respectively. A rule of thumb in fracture 

mechanics is that when the SIF reaches fracture 

toughness, the crack will become unstable and the 

wafer will break. The fracture toughness of a 

silicon wafer has a value of 0.9 MPa m1/2. Hence, 

the wafer with a 20-μm crack size will break under 

a tensile stress of 100 MPa. 

Our model is also applicable to stresses produced 

by thermal processing. The end result of this 

project will be a methodology that the PV industry 

can use to minimize wafer breakage. Such a 

methodology will include treatment of the wafers 

(e.g., etching) and optimization of temperature 

profiles during cell processing to minimize thermal 

stress effects, and establishing stress distributions 

that can be least harmful to the wafer/cell and 

prevent its breakage during wafer handling. 

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Fig. 7. Calculated stress distributions in 125-mm x 

125-mm silicon wafer caused by the presence of 

microcracks, in response to a tensile stress of 100 

MPa. Figures (a) and (b) correspond to 

microcracks of 2 μm and 20 μm, respectively. 

Figure (a) shows a 25-mm x 25-mm section, and 

(b) shows a 50-mm x 50-mm section in the vicinity 

of the cracks. The deformation of the wafer in 

both micrographs is magnified by a factor of 100. 

Metallization firing and SiN:H studies (in 

collaboration with BP Solar, Ferro, and Applied 

Materials): 

Metallization firing is the most complicated 

process step of a Si solar cell fabrication. A firing 

process step performs three separate functions: 

(1) dissolution of SiN:H by the front metallization 

followed by Si-Ag interactions at the front contact; 

(2) diffusion of hydrogen from the interface into the 

bulk of the cell for impurity and defect passivation; 

and, (3) alloying of the back Al contact to form a 

back surface field (BSF). To achieve the highest 

efficiency, each of these functions must be 

maximized. We are studying each of these 

functions to establish one process cycle that can 

maximize all of them to produce the highest 

efficiency cells. These studies require a furnace 

with a capability to apply a controlled optical flux 

as a function of time, a method to monitor the 

temperature distribution in the cell (in particular, 

under the metallization), and ability to characterize 

fired samples under different process conditions. 

To accomplish these, we have built an optical 

processing furnace with a capability to exhaust 

effluent, monitor the temperature distribution of the 

entire solar cell using multiple thermocouples 

attached to the cell itself, and control the entire 

process cycle. Characterization of fired cells is 

done by various groups in the M&C Division and is 

facilitated by a new procedure that we have 

developed for cross-sectioning a large area of a 

solar cell, using chemical mechanical polishing. 

Two important findings were that: (1) for a given 

optical flux, screen-printed cells exhibit a large 

temperature difference between regions with and 

without front metallization. For example, using an 

optical flux density profile that produced a 

maximum temperature of 812°C, away from the 

buss bar, yielded a temperature of 786°C under 

the buss bar (this represents near optimum firing 

conditions). Perhaps more significant is that these 

temperatures are far below the eutectic point of 

Ag-Si (835°C) and the melting point of Ag 

(961.9°C), yet they yield low-resistance ohmic 

contacts. This can only be explained by invoking 

mechanisms that can depress the eutectic melting 

point of Ag-Si, such as the presence of other 

metals and interface energy. It also suggests a 

need for carefully designed temperature 

measurements during solar cell processing. 

Applied spectroscopic ellipsometry to facilitate 

development of improved Si SHJ solar cells: 

Among the highest-efficiency PV modules 

commercially available today are Sanyo’s HITTM 

modules, which are based on silicon 

heterojunction technology. NREL’s silicon 

materials team is rapidly developing the 

technology to challenge Sanyo’s lead in the SHJ 

area. In FY 2006, the team achieved 18.2% 

efficiency on a p-type float-zone silicon wafer. 

One of the challenges in SHJ R&D is measuring 

the film thickness and material properties of the 

extremely thin (2–6 nm) amorphous silicon (a-Si) 

layers used in SHJ devices. Because the material 

properties are both thickness- and substratedependent, the only reliable way to measure them 

is to measure the films incorporated into the actual 

devices. We have applied in-situ and ex-situ 

spectroscopic ellipsometry to provide accurate and 

timely measurements of film thickness and optical 

and electronic properties of a-Si films used in SHJ 

devices. In-situ real-time spectroscopic 

ellipsometry (RTSE) has been used to gain insight 

into the film growth mechanisms, as well as how 

the material properties change with changes in the 

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deposition conditions. Ex-situ variable-angle 

spectroscopic ellipsometry (VASE) has been used 

to measure the properties of the a-Si layers in 

partially or fully completed SHJ devices. By 

measuring the thickness and absorption coefficient 

of the i-, n-, and ITO-layers in a SHJ device, we 

are able to calculate the optical absorption in 

these layers. This information can be used to 

pinpoint efficiency losses and targets for improving 

efficiency. Figure 8 shows a comparison of the 

optical losses that are due to absorption in the iand n-layers with the difference in quantum 

efficiency between two devices that are identical 

except for the presence of the i- and n-layers 

forming the front junction. The agreement 

between these two disparate measurement 

techniques is excellent, indicating that light 

absorbed in the i- and n-layers does not contribute 

to the photocurrent in the SHJ cell. 

Fig. 8. Green diamonds; difference in internal 

quantum efficiency (IQE) between standard 

diffused junction Si PV cell and equivalent SHJ 

cell. Blue line; absorption in i- and n-layers 

determined from ellipsometry. 

Apply Dessis 2-D device modeling software to 

elucidate fundamental limitations in crystalline and 

polycrystalline photovoltaic device designs: 

Solar cell modeling has generally been limited to 

one-dimensional models that calculate simple 

current-voltage curves. A new effort within our 

group has focused on developing fully twodimensional solar cell modeling with the ability to 

simulate multiple experiments or measurements 

including current-voltage, quantum efficiency, 

time-resolved photoluminescence, near-field 

scanning optical microscopy, electron-beaminduced current, and cathodoluminescence. This 

computational effort has been applied to diverse 

solar cell problems in FY 2006. 

For example, in CdTe solar cells the electric field 

of the CdTe/CdS junction can quickly alter the 

spatial profiles of the excess electrons and holes, 

thereby distorting recombination rates and lifetime 

measurements. Simulations of time-resolved 

photoluminescence (TRPL) experiments on 

completed CdTe solar cells tracked the complex 

carrier dynamics following a short laser pulse into 

a junction and indicated the conditions under 

which meaningful lifetime values can be extracted. 

This led to a CdTe model that simultaneously 

reproduces experimental current density voltage 

(J-V) data, TRPL data, and trends between device 

performance and lifetime. CdTe device modeling 

also indicates how lifetime measurements are 

affected by grain boundaries and surface 

recombination, and conversely, to what degree 

lifetime measurements can resolve the impact of 

these different recombination mechanisms on 

device performance. 

In another thin-film technology area, researchers 

have recently proposed that CuInGaSe2 solar cells 

are composed of nanodomains caused by 

compositional fluctuations and/or phase 

separation. These nanodomains may form a 

three-dimensional network of p-n regions that 

separate charge, alter solar cell operation, and 

possibly improve device efficiency. Figure 9 

illustrates a 2-D calculation of the hole current 

density under short-circuit conditions for a 

hypothetical CIGS device with micron-sized n-type 

domains embedded within p-type material. 

Additional calculations using much smaller 

domains (ranging from 10 nm to 1 μm) are 

currently being evaluated to determine how charge 

separation, band offset, and ultimately solar cell 

performance changes for different-sized domains. 

This is part of a larger ongoing effort to explore if 

there are two-dimensional device designs that can 

be exploited to enhance solar cell efficiency. 

Fig. 9. Hole current density calculated for micron-size 

n-type domains within a p-type matrix in a CIGS solar 

cell. Cell is in short circuit. 

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Relocated Electro-Optical laboratories to the S&TF: 

The Electro-Optical Characterization Team moved 

approximately 70% of its laboratory facilities from 

the Solar Energy Research Facility (SERF) to the 

S&TF during FY 2006. The laboratories moved 

included Fourier Transform Infrared (FTIR), 

Photoconductive Decay (PCD) Lifetime, DeepLevel Transient Spectroscopy (DLTS), VASE, and 

Electro-Optical Technique Development. 

The moves were performed in two phases, with 

the FTIR, DLTS, and VASE labs moving in late 

June and the PCD and Electro-Optical labs 

moving in late July. The lab moves were well 

planned and efficiently executed, yet still 

consumed significant portions of staff time prior to, 

during, and after the moves. Prior to moving, staff 

were involved in move planning, utilities 

specification and fit-up in the new labs, and 

equipment decommissioning and packing. Staff 

supervised the movers to ensure delicate 

equipment was safely moved. After moving, staff 

were responsible for unpacking, set-up, and 

recommissioning of lab equipment. Finally, the old 

labs in the SERF had to be decommissioned and 

made ready for their new occupants. Downtime 

was as short as one week for some FTIR lab 

equipment, and as long as several weeks for 

sophisticated pulsed lasers used for the PCD 

lifetime measurements. All lab facilities were fully 

up and running by the completion of FY 2006. 

3.4 Surface Analysis Task 

Study relationship between moisture barrier 

deposition fundamentals and ultimate barrier 

performance characteristics: 

Flexible polymer substrates coated with inorganic 

oxide moisture barriers are a potential 

replacement for glass backsheets in thin-film PV 

modules. These coatings may also be suitable for 

direct application to cells. Silicon oxynitride 

(SiOxNy) deposited by plasma-enhanced chemical 

vapor deposition (PECVD) on polyethylene 

terephthalate (PET) represents one potential new 

backsheet candidate. Studies in FY 2005 using 

X-ray photoelectron spectroscopy (XPS), showed 

that plasma pretreatment of PET surfaces prior to 

deposition induces chain scission of the PET 

molecular structure, resulting in the formation of 

low-molecular-weight, polar fragments. These 

fragments were found to be volatilized or diffused 

into bulk PET on heating above 75°C and were 

also found to be water soluble. Non-removal of 

these fragments led to a weak interfacial layer that 

delaminated either during the initial peel tests or 

after damp-heat testing. Work in FY 2006 explored 

several fundamental deposition parameters and 

their relationship to the subsequent SiOxNy film 

properties and interfacial stability. The mobility of 

the fragments at relatively low temperatures 

implies that if the deposition temperature is high 

enough, these fragments should be removed 

during deposition. A new calibration curve for the 

substrate heater versus platen temperature led to 

substantially higher deposition temperatures, 

resulting in films with no observable damaged 

layers at the PET/SiOxNy interface as measured 

by XPS. In addition, careful mapping of the film 

composition shows that there is a large difference 

in thickness over the entire 12-in x 12-in substrate. 

Film composition was similarly mapped by XPS 

depth profiling and differences in nitrogen 

composition were observed for the SiOxNy films. 

These differences provide the opportunity to study 

the effect of barrier thickness and composition 

using a combinatorial approach. To facilitate using 

a combinatorial approach, we designed, built, and 

implemented a small-area water vapor transport 

rate (WVTR) cell for the MOCON analyzer. The 

new design allows us to use a more uniform film 

area to test the barrier performance, and also to 

attain a better correlation with the true film 

thickness and composition. 

Better understanding of the deposition system has 

allowed us to reproducibly fabricate SiOxNy 

barriers with excellent adhesion to the PET, such 

that, during pull tests, cohesive failure often occurs 

in the PET rather than at the interface. Initial 

barrier performance is also excellent. However, 

peel strength degrades with continued damp-heat 

testing, indicating that the interface between the 

PET and barrier still degrades under the 

85°C/85% humidity conditions. It should be noted, 

however, that films have excellent barrier 

properties prior to adhesion loss during damp-heat 

testing. Properties of the PET itself are thought to 

be contributing to SiOxNy/PET interface failure. 

We have shown that PET swells when exposed to 

moisture, and since the WVTR test requires that 

the uncoated PET side be in contact with the 

moisture, it may be that mechanical and chemical 

changes in the PET are causing the loss of 

adhesion during damp-heat stress. We are 

currently testing PET films with barrier coatings on 

both sides to try and alleviate this problem. In 

addition, deposition of SiOxNy barriers directly on 

Al/glass mirrors is planned as a parallel study of 

barrier performance, leading into direct coating of 

cells. Parts of this work were presented and 

4th published in the World Conference on 

Photovoltaic R&D

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14
 

 

 

 

 

 

Photovoltaic Energy Conversion Proceedings. 

This work will continue in FY 2007 with parallel 

studies of barriers deposited directly on Al mirrors. 

Design and specify a cart-based Auger electron 

spectroscopy tool for use in the S&TF: 

Extensive planning meetings to define the scope 

of capabilities for this tool began during the first 

quarter of the year. During the second quarter, the 

technical advisory committee developed detailed 

technical specifications for the tool. The technical 

specifications were distributed in a statement of 

work (SOW) through a formal competitive bid 

process. Nine vendors were identified, and two 

responded with actual bids for construction of the 

system. The technical review committee analyzed 

the bids and was unanimous in its selection of the 

winning bid, submitted by DCA Instruments. DCA 

addressed all the points in the NREL SOW and 

even suggested an improvement to one item. In 

addition, the bid was within the budgeted amount 

for this tool. The procurement moved swiftly 

through NREL’s Contracts and Business services, 

and the purchase request was placed with DCA 

Instruments on September 28, 2006. The 

milestone to specify, complete a competitive bid, 

and place the order for this tool was met. Since 

the end of the fiscal year, this activity has 

progressed through refinement of technical 

drawings to the construction phase. Delivery of the 

tool is expected at the beginning of the third 

quarter of FY 2007. 

Move Surface Analysis Cluster Tool to the S&TF: 

The contents of the Surface Analysis laboratory, 

including the five major pieces of equipment 

comprising the cluster tool, were moved from 

SERF E130 to S&TF 140 in late July. Prior to 

disassembly and transfer of the equipment, the lab 

was cleaned and sampled for hazardous 

materials. All areas sampled were found to be 

below threshold limits in accordance with good 

laboratory hygiene practices. Following the 

physical move to the new laboratory, reassembly 

of components and restarting of vacuum systems 

were performed. In addition, various components 

and subsystems on the cluster tool were serviced. 

Within four weeks of the move date, the PHI 670 

Auger tool, PHI 5600 XPS/UPS, ultrahigh vacuum 

(UHV) transfer system, and glove box were 

operational. The UHV deposition system was sent 

off site for chamber cleaning and is being 

reassembled. The reassembled cluster tool 

equipment passed the readiness verification 

review on September 13, 2006, and the laboratory 

resumed full operations, completing the FY 2006 

milestone. 

Study the reaction kinetics of nanoscale CuxTe 

films: 

Copper telluride is being explored as a potential 

back-contact material for tandem thin-film PV 

devices in, which the top cell is based on a CdTeCdS junction. Copper telluride has good electrical 

properties for a back contact to a CdTe-based 

solar cell. If sufficiently thin, CuxTe films can be 

deposited on CdTe and the optical transmission of 

the CuxTe back contact should be high enough to 

allow light into the bottom cell of the tandem PV 

device. Much of the research into CuxTe back 

contacts is currently focused on understanding 

deposition and processing of this material on 

CdTe substrates. In addition, CuTe is an ideal 

prototypical system for learning about fundamental 

properties of other PV-relevant chalcogenides 

such as CuxSe and CuxS, which are relevant to 

CIGS deposition and processing. Measurements 

were performed to probe the reaction kinetics of 

nanometer-scale thin films of CuxTe. These 

measurements were performed in the surfaceanalysis deposition system using thermaldesorption mass spectrometry (TDMS). Initial 

measurements revealed that separately deposited 

ultrathin-film Cu and Te react to form CuxTe (with 

x ~2), and that the CuxTe decomposes via the 

CuxTe = xCu +1/2Te2 reaction at temperatures 

above about 700 K. This reaction appears to obey 

first-order kinetics with respect to the amount of 

CuxTe that is present. This is combined with 

parallel studies of a surface-segregated 

metastable CuxTe phase found on the CdTe 

(111)-B surface. Preliminary research indicates 

that this phase may be responsible for ohmic 

behavior of Cu in CdTe back contacts. 

Understanding the reaction kinetics is necessary 

for developing models to predict formation of this 

phase and subsequent process tolerances 

required to maintain long-term CdTe/CdS device 

stability. A manuscript detailing the surfacesegregated CuxTe phase is in preparation. 

Conducted studies of wet-chemical processing of 

PV material surfaces, leading to better control of 

deposition processes: 

Previously, we have duplicated a chemical bath 

deposition (CBD) reactor in our cluster tool to 

study the interaction and chemistry of the CBD 

CdS process with CIGS surfaces. Using our 

dedicated setup, we have shown various chemical 

and electronic changes in the CIGS surface as a 

result of interaction with the aqueous NH3 bath. In 

15

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addition, we developed a surfactant-assisted 

method that provides a more uniform CdS 

deposition and consequently improved CdS/CIGS 

junction performance. Experiments at the start of 

FY 2006 looked at an ammonia-free process for 

CdS deposition. Initial results indicated that CdS 

produced in this fashion contains smaller amounts 

of oxygen than the standard ammonia process. 

Unfortunately, it was not possible to have devices 

made on this material due to limited resources. 

For the remainder of the year, we focused on 

better control of the CBD process. As currently 

performed, the CBD reaction is a batch process 

and the resulting films can be subject to significant 

variations from run to run. We have begun testing 

a liquid-phase quartz crystal microbalance 

(LP QCM) sensor for film thickness and endpoint 

detection of the CBD process. The instrument has 

revealed interesting and potentially important 

issues with nucleation of chemical bath-grown 

CdS films. Problems anticipated with the use of 

this type of instrument with the NREL CdS 

process, including excessive noise from stirring, 

bubble formation on the sensor head, and rapidly 

changing temperature, were found to be 

manageable. Using this system, we have 

demonstrated that a liquid-phase QCM is able to 

measure deposition rates in the cluster tool CBD 

reactor, despite the non-ideal conditions typical of 

the NREL CdS reaction. The sensor has shown 

that the CdS CBD deposition rate in the standard 

NREL process is highly nonlinear and that the 

variability of the rate from run to run is high. The 

QCM was also used to test if the surfactantassisted CBD method developed in our lab can be 

extended to CdTe technology. The QCM was used 

to prepare CdS films of known thickness on 

TCO/glass substrates for further processing into 

CdTe devices by collaborators within NREL 

(X. Wu) and at the Institute for Energy Conversion 

(B. McCandless). Although previous work with the 

CdS/CIGS material system showed significant 

improvements with the surfactant-assisted 

method, initial results for CdTe/CdS devices grown 

on two different Cd2SnO4/glass substrates 

showed a substantial decrease in efficiency. It was 

not clear at the end of FY 2006 if this difference 

was attributable to the choice of TCO substrate or 

a more fundamental difference in the reaction 

chemistry of CdS and CdTe. We are currently 

awaiting results from devices grown on 

commercial TEK15 TCO/glass substrates to help 

resolve this. 

4. Planned FY 2007 Activities 

A list of selected FY 2007 planned activities is 

given below. A more complete list of planned 

activities and milestones can be found in the 

Measurements and Characterization FY 2007 

Annual Operating Plan. In FY 2007, we will 

complete the following milestones: 

•	 Provide measurement support in the areas of 

analytical microscopy, cell and module 

performance, electro-optical characterization, 

and surface analysis to at least 70 PV 

research partners in industry, academia, and 

NREL. 

•	 Maintain ISO accreditation for primary and 

secondary cell and module calibrations. 

•	 Develop integrated plan to support SAI TPP 

awardees that meets their R&D needs within 

the context of available resources. 

•	 Investigate the atomic structure of the c-Si/aSi interface, and the thickness and crystallinity 

of the a-Si layer in Si heterojunction cells, as a 

function of cell processing conditions. 

•	 Develop luminescence mapping capability for 

industrial silicon wafers. 

• Organize the 17th Workshop on Crystalline 

Silicon Solar Cell & Modules: Materials and 

Processes: identify priority R&D issues for the 

Si PV industry. 

•	 Improve understanding of CdTe back-contact 

reaction kinetics by developing a quantitative 

model for surface-segregation phenomena. 

•	 Investigate materials chemistry of CIGS on 

flexible substrates, leading to an improved 

understanding of long-term reliability. 

•	 Complete study of the kinetics of microcrack 

propagation and improve our understanding of 

how thermal profiling and mechanical 

stresses, associated with conventional 

processing, impact propagation. 

•	 Assess the technical shortcomings of minoritycarrier lifetime measurement techniques used 

to determine material quality of mc-Si; apply 

improved understanding to facilitate better 

measurements of material quality for PV 

industry. 

•	 Develop enhanced cell and module 

measurement capabilities that improve 

measurement turnaround time and uncertainty 

necessary to support the SAI (requires capital 

equipment funding). 

Photovoltaic R&D

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16
 

 

 

 

 

 

5. FY 2006 Special Recognitions and Awards 

•	 Sally Asher was elected a chair of the Applied 

Surface Science Division of the AVS and is 

program committee co-chair for the 54th AVS 

International Symposium. 

•	 Pete Sheldon was elected a director of the 

AVS. 

•	 The Cell and Module Performance team 

received the 2006 NREL Staff Outstanding 

Team Award. 

6. Major FY 2006 Publications 

R.K. Ahrenkiel and S.W. Johnston, "Analysis of 

Microwave Reflection for Measuring Recombination 

Lifetime in Silicon Wafers," 16th Workshop on 

Crystalline Silicon Solar Cells & Modules: Materials 

and Processes, August 6-9, 2006, Denver, CO, USA. 

M.M. Al-Jassim, K.M. Jones, H.R. Moutinho and Y. 

Yan, “The Structural, Chemical and Microelectrical 

Properties of Screen-Printed Contacts on Crystalline 

Si Cells,” Invited talk, The 19th Australian Conf. on 

Microscopy and Microanalysis, Sydney, Australia, 

Feb. 5-9, 2006. 

A. Barnett, C. Honsberg, D. Kirkpatrick, S. Kurtz, D. 

Moore, D. Salzman, R. Schwartz, J. Gray, S. 

Bowden, K. Goossen, M. Haney, D. Aiken, M. 

Wanlass, K. Emery, “50% Efficient Solar Cell 

Architectures and Designs,” Proc. 4th World Conf. on 

Photovoltaic Energy Conversion (Hawaii, 2006). 

W. Choi, A.T. Findikoglu, M.J. Romero, and M.M. AlJassim, “Effect of Grain Alignment on Carrier 

Transport in Aligned Crystalline Silicon Films on 

Polycrystalline Substrates,” submitted to J. Mat. Res. 

S.H. Demtsu, D.S. Albin, J.W. Pankow, A. Davies, 

“Stability Study of CdS/CdTe Solar Cells Made with 

Ag and Ni Back-Contacts,” Solar Energy Materials & 

Solar Cells (2006), 90(17), 2934-2943. 

K. Emery, A. Anderberg, J. Kiehl, C. Mack, T. 

Moriarty, L. Ottoson, and S. Rummel, “PV Cell and 

Module Calibration Activities at NREL,” DOE Solar 

Program Review Meeting (Denver, 2005). 

K. Emery, S. Winter, S. Pinegar, and D. Nalley, 

“Proc 4th World Linearity Testing of Photovoltaic 

Cells,” Proc. 4th World Conf. on Photovoltaic Energy 

Conversion (Hawaii, 2006). 

M. Gloeckler, J.R. Sites, and W.K. Metzger, “GrainBoundary Recombination in Cu(In,Ga)Se2 Solar 

Cells,” Journal of Applied Physics 98, 113704 (2005). 

M.A. Green, K. Emery, D.L. King, Y. Hishikawa, and 

W. Warta “Solar Cell Efficiency Tables (version 27),” 

Progress in Photovoltaics Research and 

Applications, vol. 14, pp. 45-51, 2006. 

M.A. Green, K. Emery, D.L. King, Y. Hishikawa, and 

W. Warta, “Solar Cell Efficiency Tables (version 28),” 

Progress in Photovoltaics Research and 

Applications, vol. 14, pp. 451-461, 2006. 

S.-H. Han, C. Persson, F.S. Hasoon, H.A. Al-Thani, 

A.M. Hermann, D.H. Levi, “Optical Properties and 

Electronic Structures of (4CuInSe2)y(CuIn5Se8)1−y,” 

Phys Rev B 74, 85212-85222, 2006. 

S.-H. Han, F.S. Hasoon, H.A. Al-Thani, A.M. 

Hermann, D.H. Levi, “Effect of Cu Deficiency on the 

Optical Properties and Electronic Structure of CuIn1­

xGaxSe2,” J. Phys. Chem. Solids 66, 1895 (2005). 

M.M. Hilali, K. Nakayashiki, C. Khadilkar, R.C. 

Reedy, A. Rohatgi, A. Shaikh, S. Kim, S. Sridharan, 

“Effect of Ag Particle Size in Thick-Film Ag Paste on 

the Electrical and Physical Properties of Screen 

Printed Contacts and Silicon Solar Cells,” J. 

Electrochem. Soc., 153(1), (2006), A5-A11. 

C.-S. Jiang, D.J. Friedman, H.R. Moutinho, M.M. AlJassim, “Profiling the Built-In Electrical Potential in IIIV Multijunction Solar Cells,” Proc. 4th World Conf. on 

Photovoltaic Energy Conversion (Hawaii, 2006). 

C.-S. Jiang, H.R. Moutinho, M.M. Al-Jassim, L.L. 

Kazmerski, B. Yan, J.M. Owens, J. Yang, and S. 

Guha, “Distribution of Local Open-Circuit Voltage on 

Amorphous and Nanocrystalline Mixed-Phase Si:H 

and SiGe:H Solar Cells,” Proc. 4th World Conf. on 

Photovoltaic Energy Conversion (Hawaii, 2006). 

C.-S. Jiang, H.R. Moutinho, M.J. Romero, M.M. AlJassim, and L.L. Kazmerski, “Electrical Charge 

Trapping at Defect on the Si(111)7 ́7 Surface,” Appl. 

Phys. Lett. 88, 061909 (2006). 

S.W. Johnston and S.R. Kurtz, "Comparison of a 

Dominant Electron Trap in N-Type and P-Type 

GaNAs Using Deep-Level Transient Spectroscopy," 

J. Vac. Sci. Technol. A 24(4), Jul/Aug 2006. 

K.M. Jones, Y. Yan, A. Ebong and M.M. Al-Jassim, 

“Dual Beam FIB and Z-Contrast STEM of Al-Si Alloy 

Layers in Silicon Solar Cells,” ICM Proceedings Sept 

3-9, 2006, Sapporo Japan. 

G.J. Jorgensen, K.M. Terwilliger, J.A. DelCueto, S.H. 

Glick, M.D. Kempe, J.W. Pankow, F.J. Pern, T.J. 

McMahon, “Moisture Transport, Adhesion and 

Corrosion Protection of PV Module Packaging 

Materials,” Solar Energy Materials & Solar Cells 

(2006), 90(16), 2739-2775. 

S. Kurtz, M. Wanlass, C. Kramer, M. Young, J. 

Geisz, S. Ward, A. Duda, T. Moriarty, J. Carapella, P. 

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Ahrenkiel, D. Albin, K. Emery, K. Jones, M. Romero, 

A. Kibbler, J. Olson, D. Friedman, W. McMahon, A. 

Ptak, “A New GaInP/GaAs/GaInAs, Triple-Bandgap, 

Tandem Solar Cell for High-Efficiency Terrestrial 

Concentrator Systems,” DOE Solar Program Review 

Meeting (Denver, 2005). 

D.H. Levi, C.W. Teplin, E. Iwaniczko, Y. Yan, T.H. 

Wang, and H.M. Branz, “Real-Time Spectroscopic 

Ellipsometry Studies of the Growth of Amorphous 

and Epitaxial Silicon for Photovoltaic Applications,” J. 

Vac. Sci. Tech. A24(4), 1676-1683, 2006-09-11. 

D.H. Levi, E. Iwaniczko, M. Page, Q. Wang, H. 

Branz, and T. Wang, “Silicon Heterojunction Solar 

Cell Characterization and Optimization Using In Situ 

and Ex Situ Spectroscopic Ellipsometry,” Proc. 4th 

World Conf. on Photovoltaic Energy Conversion 

(Hawaii, 2006). 

G. Li, V. Shrotriya, J. Huang, Y. Yao, T. Moriarty, K. 

Emery and Y. Yang, “High-Efficiency Solution 

Processable Polymer Photovoltaic Cells by SelfOrganization of Polymer Blends,” Nature Materials, 

vol. 4, no. 11, pp. 864-868, 2005. 

X. Li, S.E. Asher, S. Limpijumnong, B.M. Keyes, C.L. 

Perkins et al., “Impurity Effects in ZnO and NitrogenDoped ZnO Thin Films Fabricated by MOCND,” J. 

Crystal Growth 287, (2006) 94. 

A.H. Mahan, B. Roy, R.C. Reedy, Jr., D.W. Readey, 

D.S. Ginley, “Rapid Thermal Annealing of Hot Wire 

Chemical-Vapor-Deposited a-Si:H Films: The Effect 

of the Film Hydrogen Content on the Crystallization 

Kinetics, Surface Morphology, and Grain Growth,” 

Article No. 023507, J. Appl. Phys., 99(2), (2006). 

W.K. Metzger, D. Albin, M.J. Romero, P. Dippo, and 

M. Young, “CdCl2 Treatment, S Diffusion, and 

Recombination in Polycrystalline CdTe,” Journal of 

Applied Physics, 99, 103703 (2006). 

W.K. Metzger, M.J. Romero, P. Dippo, M. Young, 

“Understanding Recombination in CdTe Solar Cells 

with Time-Resolved Photoluminescence,” Proc. 4th 

World Conf. on Photovoltaic Energy Conversion 

(Hawaii, 2006). 

H.R. Moutinho, R.G. Dhere, C.-S. Jiang, M.M. AlJassim, and L.L. Kazmerski, “Electrical Properties of 

CdTe/CdS Solar Cells Investigated with Conductive 

Atomic Force Microscopy,” Thin Solid Films 514, 150 

(2006). 

H.R. Moutinho, R.G. Dhere, C.-S. Jiang, T. Gessert, 

A. Duda, M. Young, W.K. Metzger, and M.M. AlJassim, “The Role of Cu on the Electrical Properties 

of CdTe/CdS Solar Cells – A Cross-Sectional 

Conductive Atomic Force Microscopy Study,” 

submitted to JVST A. 

H.R. Moutinho, R.G. Dhere, C.-S. Jiang, and M.M. 

Al-Jassim, “Study of the Processing of CdTe/CdS 

Solar Cells Using Conductive Atomic Force 

Microscopy,” presented at the 2005 MRS Fall 

Meeting (Boston, 2005). 

H.R. Moutinho, B. To, C.-S. Jiang, Y. Xu, B.P. 

Nelson, C.W. Teplin, K.M. Jones, J. Perkins, and 

M.M. Al-Jassim, “How Deposition Parameters Control 

Growth Dynamics of nc-Si Deposited by Hot-Wire 

Chemical Vapor Deposition,” J. Vac. Sci. Technol. A 

24, 95 (2006). 

H.R. Moutinho, R.G. Dhere, C.-S. Jiang, T. Gessert, 

A. Duda, M. Young, W.K. Metzger, X. Li and M.M. AlJassim, “Cross-Sectional Conductive Atomic Force 

Microscopy of CdTe/CdS Solar Cells: Effects of 

Etching and Back-Contact,” Proc. 4th World Conf. on 

Photovoltaic Energy Conversion (Hawaii, 2006). 

C.R. Osterwald, J. Adelstein, J.A. del Cueto, B. 

Kroposki, D. Trudell, T. Moriarty, ”Comparison of 

Degradation Rates of Individual Modules Held at 

Maximum Power,” Proc. 4th World Conf. on 

Photovoltaic Energy Conversion (Hawaii, 2006). 

C. R. Osterwald, J. Adelstein, J.A. del Cueto, W. 

Sekulic, D. Trudell, P. McNutt, R. Hansen, S. 

Rummel, A. Anderberg and T. Moriarty, “Resistive 

Loading of Photovoltaic Modules and Arrays for 

Long-Term Exposure Testing,” Progress in 

Photovoltaics Research and Applications, vol. 14, 

pp. 567-575. 

J.W. Pankow, S.H. Glick, "Plasma Surface 

Modification of Polymer Backsheets: Origins of 

Future Interfacial Barrier/Backsheet Failure,” Proc. 

4th World Conf. on Photovoltaic Energy Conversion 

(Hawaii, 2006), pp 2250-2253. 

C.L. Perkins and F.S. Hasoon, “Surfactant-Assisted 

Growth of CdS Thin Films for Photovoltaic Applications,” J. Vac. Sci. Technol. A 24(3), (2006) 497. 

A.J. Ptak, D.J. Friedman, S.R. Kurtz, R.C. Reedy, M. 

Young, D.B. Jackrel, H.B. Yuen, S.R. Bank, M.A. 

Wistey, J.S. Harris Jr., “Calcium Impurities in 

Enhanced-Depletion-Width GaInNAs Grown by 

Molecular-Beam Epitaxy,” J. Vac. Sci. Technol. A, 

24(3), (2006), 1540. 

I.L. Repins, B.J. Stanbery, D.L. Young, S.S. Li, W.K. 

Metzger, C.L. Perkins et al., “Comparison of Device 

Performance and Measured Transport Parameters in 

Widely-Varying Cu(In,Ga)(Se,S) Solar Cells,” 

Progress in Photovoltaics, 14 (1), (2006) 25. 

Photovoltaic R&D

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18
 

M.J. Romero, C.-S. Jiang, J. Abushama, H.R. 

Moutinho, M.M. Al-Jassim, and R. Noufi, 

“Electroluminescence Mapping of CuGaSe2 Solar 

Cells by Atomic Force Microscopy,” Appl. Phys. Lett. 

89, 143120 (2006). 

M.J. Romero, C.-S. Jiang, H.R. Moutinho, and M.M. 

Al-Jassim, “Nanoprobes for Future Generations of 

Photovoltaics,” DOE Solar Program Review Meeting 

(Denver, 2005). 

M.J. Romero, C.-S. Jiang, J. Abushama, H.R. 

Moutinho, R. Noufi, and M.M. Al-Jassim, 

“Electroluminescence of CuGaSe2 Solar Cells 

Investigated by Atomic Force Microscopy, Appl. 

Phys. Lett. 89, 143120 (2006). 

M. J. Romero, J. van de Lagemaat, I. Mora-Sero, G. 

Rumbles, and M. M. Al-Jassim, “Imaging of Resonant 

Quenching of Surface Plasmons by Quantum Dots,” 

Nano Letters (in press). 

S. Rummel, A. Anderberg, K. Emery, “Results from 

the Second International Module Intercomparison,” 

DOE Solar Program Review Meeting (Denver, 2005). 

S. Rummel, A. Anderberg, K. Emery, D. King, G. 

Tamizh Mani, T. Arends, G. Atmaram, L. Demetrius, 

W. Zaaiman, N. Cereghetti, W. Herrmann, W. Warta, 

F. Neuberger, K. Morita, and Y. Hishikawa, “Results 

from the Second International Module InterComparison,” Proc. 4th World Conf. on Photovoltaic 

Energy Conversion (Hawaii, 2006). 

V. Shrotriya, G. Li, Y. Yao, T. Moriarty, K. Emery, and 

Y. Yang, “Accurate Measurement and 

Characterization of Organic Solar Cells,” Advanced 

Functional Materials, vol. 16, pp. 2016-2023, 2006. 

B. Sopori, P. Rupnowski, D. Balzar,and P. Sheldon, 

“Dislocation Generation In Si: A Thermo-Mechanical 

Model Based On Measurable Parameters,” Conf. 

Record, Proc. 4th World Conf. on Photovoltaic 

Energy Conversion (Hawaii, 2006), 936. 

B. Sopori, R. Reedy, K. Jones, L. Gedvilas, B. Keyes, 

Y. Yan, M. Al-Jassim, V. Yelundur, A. Rohatgi, 

“Damage-Layer-Mediated H Diffusion During Sin:H 

Processing: A Comprehensive Model,” Conf. Record, 

Proc. 4th World Conf. on Photovoltaic Energy 

Conversion (Hawaii, 2006). 

B. Sopori, “Recent Advances in Si Solar Cells: 

Device Design and Processing,” Tutorial Book, Proc. 

4th World Conf. on Photovoltaic Energy Conversion 

(Hawaii, 2006). 

G.J. Teeter, “Physical-Vapor Deposition FluxDistribution Calculations for Static and Rotating 

Substrates: Derivation of the Deposition Geometry 

for Optimal Film-Thickness Uniformity,” Vac. Sci. 

Technol. A, 24(4), (2006), 1112-18. 

G.J. Teeter, “Conceptual Design of a Deposition 

System for Uniform and Combinatorial Synthesis of 

Multinary Thin-Film Materials Via Open-Boat Physical 

Vapor Deposition,” Vac. Sci. Technol. A, 24(4), 

(2006), 1119-27. 

M. Wanlass, P. Ahrenkiel, D. Albin, J. Carapella, A. 

Duda, K. Emery, D. Friedman, J. Geisz, K. Jones, A. 

Kibbler, S. Kurtz, W. McMahon, T. Moriarty, J. Olson, 

A. Ptak, M. Romero, and S. Ward, “Monolithic, UltraThin GaInP/GaAs/GaInAs Tandem Solar Cells,” 

Proc. 4th World Conf. on Photovoltaic Energy 

Conversion (Hawaii, 2006). 

X. Wu, J. Zhou, J.C. Keane, R.G. Dhere, D.S. Albin, 

T.A. Gessert, C. DeHart, A. Duda, J.J. Ward, Y. Yan, 

G. Teeter, D.H. Levi, S. Asher, C. Perkins, H.R. 

Moutinho, B. To, K. Emery, T. Moriarty, Z. Zhang, S. 

Wei, T. Coutts, R. Noufi, “Advances in CdTe R&D at 

NREL,” DOE Solar Energy Program Review Meeting 

(Denver, 2005). 

B. Yan, C.-S. Jiang, H.R. Moutinho, M.M. Al-Jassim, 

J. Yang, S. Guha, “Local Current Flow in MixedPhase Silicon Solar Cells and Correlation to LightInduced Open-Circuit Voltage Enhancement”, Mater. 

Res. Soc. Symp. Proc. Vol. 910, A23.06 (2006). 

Y. Yan, R. Noufi, and M.M. Al-Jassim, “GrainBoundary Physics in Polycrystalline CuInSe2 

revisited: Experiment and Theory,” Phys. Rev. Lett. 

96, 205501 (2006). 

Y. Yan, M. Page, T.H. Wang, M.M. Al-Jassim, H.M. 

Branz, and Q. Wang, "Atomic Structure and 

Electronic Properties of c-Si/a-Si:H Heterointerfaces," 

Appl. Phys. Lett. 88, 121925 (2006). 

Y. Yan, M.M. Al-Jassim, and S.-H Wei, “Doping of 

ZnO by Group-Ib Elements,” Appl. Phys. Lett. 89, 

181912 (2006). 

Y. Yan, J. Zhou, X.Z. Wu, H.R. Moutinho, and M.M. 

Al-Jassim, “Structural Instability of Sn-Doped In2O3 

Thin Films During Thermal Annealing at Low 

Temperature,” Thin Solid Films, submitted, 2006. 

Y. Yan, K.M Jones, R. Noufi, and M.M. Al-Jassim, 

“Argon Ion Beam and Electron Beam-Induced 

Damage in Cu(In,Ga)Se2 Thin Films,” Thin Solid 

Films, submitted 2006. 

Y. Yan, K.M. Jones, R. Noufi, and M.M. Al-Jassim, 

“Z-Contrast Imaging of Nanodomains in CuInSe2 

Polycrystalline Films,” 16 international Microscopy 

Congress, Sapporo, Japan, September, 2006. 

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____________________________________________________________________________________ 

 

 

____________________________________________________________________________________ 

 

 

 

 

 

Solar Resource Characterization 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Dave Renné, 303-384-7408, david_renne@nrel.gov 

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

FY 2006 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. 

•	 Develop methods and plans for a 1991–1997 10-km gridded solar product based on the 

microstructures of 1-degree NASA solar data grid. 

•	 Implement Task 36 “Solar Resource Knowledge Management” under the International Energy 

Agency (IEA) Solar Heating and Cooling (SHC) Programme. 

Accomplishments 

•	 Completed a draft 15-year NSRDB and distributed for review. Completed plan for final NSRDB 

update and began final validation and production. 

•	 Technical results in several topical areas coming out of Task 36 “Solar Resource Knowledge 

Management.” 

Future Directions 

•	 Distribute the 15-year NSRDB update. 

•	 Produce a Typical Meteorological Year 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 DOE Solar Program Multi-Year 

Technical Plan. This includes access to data and 

characterization of the solar resource, as well as 

the needs of designers, modelers, and resource 

assessment interests, both in the United States 

and internationally. This is a multi-year project to 

update the 1961–1990 National Solar Radiation 

Data Base (NSRDB) and to implement the IEA 

“Solar Resource Knowledge Management” Task 

for benchmarking international solar resource data 

sets. Work performed in FY 2005 included: (1) 

recommendations for an NSRDB update and (2) 

development of an updated plan and Annex and 

IEA approval of the “Solar Resource Knowledge 

Management” task. 

In 1992, NREL released the 1961–1990 NSRDB, 

a 30-year, 239-station data set of measured and 

modeled solar radiation and accompanying 

meteorological data for the United States. In 2003, 

NREL investigated the feasibility of producing a 

1991–2000 update of the NSRDB and devised a 

proof-of-concept project to investigate solutions to 

several obstacles, including the switchover by the 

National Weather Service (NWS) to the 

Automated Surface Observing System for routine 

meteorological observations. 

In 1998, NREL hosted the first workshop on 

satellites for solar resource assessments, bringing 

together international researchers on the topic. 

Two follow-up workshops were held, one in 2000 

and one in 2003, leading to the development of a 

concept paper and work plan for an IEA “Solar 

Resource Knowledge Management” task. In June 

2005, this task was approved as Task 36 under 

the Solar Heating and Cooling Programme, and 

NREL was selected as the Operating Agent. This 

task links NREL’s domestic NSRDB research 

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activities with the international solar resource 

assessment work conducted by several agencies 

around the world. 

2. Technical Approach 

Two tasks are under way in the Solar Resource 

Characterization Project: (1) a domestic task 

focused on updating the NSRDB 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). 

FY 2006 work centered on producing a draft 

NSRDB for review and moving ahead with final 

production. 

The IEA/SHC Solar Resource Knowledge 

Management task provides a collaborative 

mechanism to allow researchers from a number of 

international research institutions to compare and 

benchmark various approaches for assessing 

solar resources, allowing for the new NSRDB to 

be benchmarked against these other methods. 

Two task experts meetings (November 2005 and 

July 2006) have been held, where experts from 

the participating countries presented research 

results and future plans on topics directly related 

to the task. A third task meeting will be held in 

March 2007, and a mid-term review of technical 

results will be held in November 2007 

Total project funding for FY 2006 was $420K, 

broken down in the following table: 

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 foundation work in FY 2005, we 

produced a draft NSRDB with all fields and 

stations for the purpose of review distribution. 

About 10 participants volunteered to review the 

data set, which included our design, methods, 

procedures, and output fields. From this review 

came validation of the overall design, as well as a 

few problem reports that were corrected. 

The draft NSRDB included about 1400 sites with 

hourly data fields for the period 1985–2005, 

allowing some overlap with the original 1961–1990 

NSRDB for comparisons. We developed a tiered 

classification scheme for categorizing the sites 

based on data completeness and data quality. 

Class I sites are those with a complete 15-year 

period of record, with no missing hourly solar 

radiation and key meteorological data fields. 

Class II stations are those that have gaps in the 

data, but hold enough data to be useful for some 

applications (a minimum of three years). Figure 1 

shows a preliminary map of NSRDB sites 

compared with the 1961–1990 NSRDB. 

Task Title FY 2006 

Budget ($K) 

IEA Task 36 Solar Resource 

Knowledge Management 100 

NSRDB Update 320 

3. Results and Accomplishments 

3.1 National Solar Radiation Data Base 

The changeover to automated stations by the 

National Weather Service eliminated the human 

observed total and opaque sky cover amounts 

used for inputs to the METSTAT model, which 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 

derived from Geostationary Operational 

Environmental Satellite [GOES] satellite data). 

Fig. 1. Preliminary map of NSRDB sites 

Validation work on the NSRDB uncovered 

problems with input cloud cover data due to the 

changes in weather service observations. Some 

work was done to enhance the cloud data, as well 

as to define higher uncertainties for modeled data 

under certain conditions. 

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3.2 “Solar Resource Knowledge Management” IEA 

Task 36 

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 NASA Surface Meteorology and Solar 

Energy (SSE) models, which are also being 

used for the NSRDB updates 

•	 Accessibility and coherence of ancillary model 

input data such as atmospheric conditions and 

land surface parameters 

• Sensitivity analyses 

•	 Ground truth validations with high-quality data 

•	 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: 

•	 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 

•	 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., a database) will comprise a Web 

server and 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 (entry point) will be easy to 

maintain, transfer, operate, and duplicate (to 

ensure reliability). This service will be maintained 

by Task 36 partners, and in some cases may 

involve possible commercial revenues. 

Subtask C: Improved techniques for solar 

resource characterization and forecasts. This 

subtask covers R&D work and mainly focuses 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 ground stations at two locations in 

Oregon are shown in Figure 2. 

Fig. 2. Comparison of DLR satellite-derived direct 

normal irradiance estimates with ground 

measurements collected at Burns and Eugene, 

Oregon (USA): From Stackhouse, et al., IEEE 

International Geoscience and Remote Sensing 

Symposium (IGARSS), Denver, July-August 2006. 

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4. Planned FY 2007 Activities 

At the current level of funding, the planned 

distribution of the updated 1991–2005 NSRDB will 

occur in 2007. We plan annual updates of the 

NSRDB through 2009. In 2011, a 2001–2010 

decade update will be produced, funding 

permitting. Additional products, such as Typical 

Meteorological Year and Data Manuals, will also 

be produced. 

During 2007, participants in IEA Task 36 will focus 

on 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. A technical 

workshop will be held at the Joint Research 

Center in Ispra, Italy, in March 2007, and mid-term 

review with the IEA/SHC Executive Committee will 

be held at a location to be determined in 

November 2007. 

5. Major FY 2006 Publications 

Wilcox, S., M. Anderberg, W. Beckman, A. 

DeGaetano, R. George, C. Gueymard, W. Marion, 

D. Myers, R. Perez, M. Plantico, D. Renne, 

P. Stackhouse, F. Vignola. “Toward Production of 

a National Solar Radiation Database,” Proc. Solar 

2006, American Solar Energy Society, 2006. 

David S. Renné, Richard Meyer, Hans-Georg 

Beyer, Lucien Wald, Richard Perez, and Paul 

Stackhouse, “Solar Resource Knowledge 

Management: A New Task of the International 

Energy Agency,” Proc. Solar 2006, American 

Solar Energy Society, 2006. 

P.W. Stackhouse, Jr., D. Renné, H. -G. Beyer, L. 

Wald, R. Meyer, M. Schroedter-Homscheidt, R. 

Perez, and M. Suri “Towards Designing an 

Integrated Earth Observation System for the 

Provision of Solar Energy Resource and 

Assessment,” Proc. IGARRS Conference, 2006. 

. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity FY 2005 ($K) 

State University of New 

York, Albany 

Richard Perez 

Albany, NY 

perez@asrc.cestm.albany.edu 

Produce 10-km gridded data for the 

United States; Investigate methods of 

interpolating 1-degree grid to 10-km grid. 

30 

University of Oregon 

Solar Monitoring 

Laboratory 

Frank Vignola 

Eugene, Oregon 

fev@darkwing.uoregon.edu 

Develop procedures for correcting rotating 

shadowband radiometer data and apply 

the corrections to NSRDB-measured solar 

data. 

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____________________________________________________________________________________ 

 

 

 

 

 

 

____________________________________________________________________________________ 

Environmental Health and Safety 

Performing Organization: Brookhaven National Laboratory (BNL) 

Key Technical Contact: Vasilis Fthenakis, 631-344-2830, vmf@bnl.gov 

DOE HQ Technology Manager: Alec Bulawka, 202-586-5633, alec.bulawka@ee.doe.gov 

FY 2006 Budget: $400K 

Objectives 

•	 Assist in preserving the safe and environmentally friendly nature of photovoltaics and in 

minimizing environmental health and safety (EH&S) risks and associated costs, to ensure the 

public support and economic viability of PV systems. 

•	 Identify potential EH&S barriers of PV materials, processes, or applications and define strategies 

to overcome such barriers. 

•	 Maintain the EH&S Research Center as the world’s best source on PV EH&S, providing accurate 

information related to EH&S issues and perceptions. 

Accomplishments 

•	 Conducted a comparative study of Greenhouse Gas Emissions during the Life Cycle of PV and 

nuclear fuel cycles; Energy Policy, in press. 

•	 Conducted a life-cycle analysis (LCA) of the Amonix c-Si PV concentrator system. 

•	 Promoted and established international collaborative life-cycle environmental assessments of PV 

energy technologies, enhancing the quality and quantity of PV environmental assessments. 

•	 Optimized a Cd/Te ion-exchange separation and filled patent application 11/421,343 for “System 

and Method for Separating Tellurium from Cadmium Waste,” May 31, 2006. 

•	 Advanced the recovery of 99.9%-pure Cd in the CdTe recycling program at a projected cost of 

0.1 ¢/Wp. 

•	 Assisted First Solar, United Solar Ovonic, DayStar Technologies, and the University of Toledo 

with site-specific EH&S issues. 

•	 Co-organized and co-chaired, with General Motors, the three-day Symposium “Life-Cycle 

Analysis for Green Materials and Process Selection,” Materials Research Society (MRS), Boston, 

Nov. 2005. 

•	 Answered several requests for EH&S information from the public and the industry. 

Future Directions 

EH&S research at BNL will support the Solar American Initiative (SAI) objectives by: 

•	 Defining low-cost recycling for manufacturing and spent modules 

•	 Assisting the industry in preventing accidents and releases of hazardous materials to the 

environment, and guiding them toward environmentally friendly material and process options 

•	 Extending EH&S research and LCA to III-V PV concentrators 

•	 Accurately defining the environmental profiles of solar electric and solar thermal technologies as 

they scale up to meet the SAI challenge 

•	 Answering inquiries from the industry, legislators, and the public about EH&S issues in solar 

energy cycles. 

In addition, research at BNL will identify and characterize EH&S hazards associated with emerging 

materials, including nano-material forms, for the U.S. Department of Energy, its contractors, and the 

private sector. 

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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 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 public support and economic viability of 

PV systems. Minimization of EH&S risks and 

costs is paramount for achieving the Solar 

Program’s goal of $0.06/kWhr by 2020, while 

having the support of the public is a prerequisite 

for existence and growth to the scale that would 

support this low cost. 

Also, the Center serves as the world’s best source 

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 activities are Hazard Identification 

and Characterization, Hazard Management, 

Industry Outreach, and Information Dissemination. 

Ongoing efforts are required because the PV 

industry is undergoing changes in type and 

quantities of materials, manufacturing processes 

and scale, and because continuous vigilance is 

required in safety and loss prevention. 

Task 1: Identification and Characterization of 

EH&S Issues. In FY 2006, we conducted and 

published: (1) an LCA of the Amonix highconcentrator PV system; (2) an LCA-based 

comparison of PV with nuclear power systems; (3) 

a study of energy payback times, greenhouse 

gases, and external cost of PV; and (4) a 

comparison on the environmental metrics of gridconnected and ground-based PV systems. 

Task 2: Hazard Management. In FY 2006, we 

advanced the recycling of CdTe PV by 

accomplishing a recovery of 99.9%-pure cadmium 

through optimized separations and electrowining, 

at a projected cost of 0.1¢/W. 

Task 3: Industry Outreach and Support to DOEHQ and NCPV. The industry outreach activities 

include frequent interactions with EH&S 

personnel, site visits, guidance with 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 as the PV industry as installations 

grow to levels that attract public interest and 

scrutiny. 

Task Title FY 2006 

Budget ($K) 

1. Hazard Identification and 

Characterization 180 

2. Hazard Management and 

Recycling 90 

3. Industry Outreach/DOE/NCPV 78 

4. Information Dissemination 52 

3. Results and Accomplishments 

Task 1 

•	 Completed and published LCAs of commercial 

CdTe PV systems. 

•	 Conducted LCA-based comparisons of 

greenhouse-gas emissions and risks in the PV 

and nuclear fuel life cycles. 

•	 Completed and published an LCA of 

crystalline Si concentrator systems. 

•	 Contributed to several cooperative LCAs with 

researchers in Europe. 

Task 2 

•	 Increased the recovery rate and purity of Cd 

and Te from actual CdTe manufacturing scrap. 

•	 Conducted a safety analysis of silane storage 

systems with United Solar Ovonic, and 

presented it at a conference. 

Task 3 

•	 Provided facility-specific assistance to First 

Solar, United Solar Ovonic, and DayStar 

Technologies. 

•	 Organized a PV EH&S task workshop for the 

International Energy Agency (IEA). 

Task 4 

•	 Answered several requests for EH&S 

information from different agencies, business 

partners, citizen organizations, and the media. 

•	 Organized an MRS symposium on LCA. 

•	 Published and presented extensively. 

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4. Planned FY 2007 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 2007 include: 

•	 Life-cycle investigation of CdS alternatives in 

CIGS PV systems 

•	 Life-cycle investigation of greenhouse gas 

emissions in crystalline silicon etching 

operations 

•	 LCA-based study of CIGS PV module 

manufacturing efficiencies (pending industry 

data), or LCA-based comparisons of CIGS, 

CdTe and a-Si PV module manufacturing 

efficiencies based on energy use, 

thermodynamics, and kinetics. 

Task 2: Hazard Management/Recycling 

These activities are pivotal to preserving the safe 

and environmentally friendly nature of the PV 

industry as it moves toward large-scale 

manufacturing. In FY 2007, research at BNL will 

focus on: 

•	 Improving the purity of Te and Cd, which are 

recycled from CdTe manufacturing scrap and 

spent modules 

•	 Scaling up Cd/Te/Cu/Fe separations and Cd 

and Te recovery processes to study the actual 

variability in manufacturing scrap composition 

•	 Assisting the industry in developing a recycling 

infrastructure 

•	 Assisting the industry in implementing 

recycling options. 

Task 3: Industry Outreach/Support to DOE and 

NCPV 

•	 Start IEA PV EH&S Task 12; serve as the lead 

organizer and U.S representative to the task. 

•	 Guide the industry and R&D labs on accident 

prevention and pollution prevention. 

•	 Support DOE and NCPV as needed. 

Task 4: Information Dissemination 

The results of BNL’s research will be disseminated 

with new publications, e-mail, and the Internet. 

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 challenge of 

the Solar American Initiative toward cost-effective 

production of solar electricity by 2020. 

BNL staged MRS Symposium R: Life Cycle 

Analysis for New Energy Conversion and Storage 

Systems to take place in Nov. 2007. NREL and 

the EPA will co-organize the event. 

5. FY 2006 Special Recognitions, Awards, and 

Patents 

Filed patent #11/421,343, “System and Method for 

separating Te from Cd Waste.” 

Vasilis Fthenakis received the U.S. DOE 

Certificate of Appreciation “for superior technical, 

management and communications skills exhibited 

in photovoltaic environmental research and in 

effective dissemination of research results,” 

March 2006. 

6. Major FY 2006 Publications 

Fthenakis V.M., Fuhrmann M., Heiser J., Lanzirotti 

A., Fitts J., and Wang W., "Emissions and 

Redistribution of Elements in CdTe PV Modules 

during Fires," Progress in Photovoltaics: Research 

and Applications 13, 713–723, 2005. 

Mason J., Fthenakis V.M., Hansen T., and Kim C., 

"Energy Pay-Back and Life Cycle CO2 Emissions 

of the BOS in an Optimized 3.5 MW PV 

Installation," Progress in Photovoltaics: Research 

and Applications 14, 179–190, 2006. 

Fthenakis V.M and Wang W., "Extraction and 

Separation of Cd and Te from Cadmium Telluride 

Photovoltaic Manufacturing Scrap," Progress in 

Photovoltaics: Research and Applications 14 

363–371, 2006. 

Fthenakis V.M. and Alsema E., "Photovoltaics 

Energy Payback Times, Greenhouse Gas 

Emissions and External Costs: 2004–early 2005 

Status," Progress in Photovoltaics Research and 

Applications 14 275–280, 2006. 

Fthenakis V.M. and Kim H.C., "Greenhouse Gas 

Emissions from Solar Electric and Nuclear Power: 

A Life Cycle Study," Energy Policy, in press. 

Kim H.C. and Fthenakis V.M, "Amonix HighConcentrator Photovoltaic System: Life Cycle 

Energy Demand and Greenhouse Gas 

Emissions," Proceedings IEEE 4th World 

Conference on Photovoltaic Energy Conversion, 

Hawaii, May 8–12, 2006, 628–631. 

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Fthenakis V.M., "Quantifying the Life-Cycle 

Environmental Profile of Photovoltaics and 

Comparisons with other Electricity-Generation 

Technologies," Proceedings IEEE 4th World 

Conference on Photovoltaic Energy Conversion, 

Hawaii, May 8–12, 2006, 2477–2480. 

de Wild-Scholten M.J., Alsema E., ter Horst E.W., 

Bachler M., and Fthenakis V.M., "A Cost and 

Environmental Impact Comparison of GridConnected Rooftop and Ground-Based PV 

Systems," Proceedings 21st European 

Photovoltaic Solar Energy Conference, Dresden, 

Germany, 4–8 September 2006, 3167–3172. 

Alsema E., de Wild-Scholten M.J. and Fthenakis 

V.M., "Environmental Impacts of PV Electricity 

Generation — A Critical Comparison of Energy 

Supply Options, Proceedings 21st European 

Photovoltaic Solar Energy Conference, Dresden, 

Germany, 4–8 September 2006, 3201–3207. 

Fthenakis V.M., Colli A., Arellano A., Kirchsteiger 

C., and Ale B., "Evaluation of Photovoltaics in a 

Comparative Context," Proceedings 21st European 

Photovoltaic Solar Energy Conference, Dresden, 

Germany, 4–8 September 2006, 3194–3201. 

Fthenakis V.M., "CdTe Photovoltaics: Life-cycle 

Environmental Profile," European Material 

Research Society Meeting, Symposium O, Invited 

Paper, Nice, France, May 29–June 2, 2006. 

Fthenakis V.M., "Photovoltaics Life Cycle 

Analysis," Invited Plenary Presentation, 

Renewable Energy 2006, Chiba, Japan, 

October 11, 2006. 

Fthenakis V.M., "International Energy Agency 

Workshop of PV-EH&S," held in conjunction with 

the 21st European Photovoltaic Solar Energy 

Conference, Dresden, Germany, Aug./Sept. 2006. 

Fthenakis V.M., Carlisle C., and Chan W., "Silane 

Safety in Amorphous Silicon and Silicon Nitride 

Operations," Proceedings 21st European 

Photovoltaic Solar Energy Conference, Dresden, 

Germany, 4–8 September 2006, 1761–1783. 

Fthenakis V.M., Wang W., Meader A., and Squires 

K., "Recycling of CdTe Photovoltaic Modules: 

Recovery of Glass, Cadmium and Tellurium," 

Proceedings 21st European Photovoltaic Solar 

Energy Conference, Dresden, Germany, 4–8 

September 2006, 2539–2541. 

Wang W. and Fthenakis V.M., "Recovery of 

Tellurium from Cadmium Telluride Photovoltaic 

Module Manufacturing Scrap and other Sources," 

The Minerals, Metals & Materials Society 135th 

Annual Meeting & Exhibition," San Antonio, Texas, 

March 12–16, 2006. 

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Crystalline Silicon Project 

Performing Organizations: National Renewable Energy Laboratory (NREL)

 DOE Golden Field Office (DOE/GO) 

Key Technical Contacts: David Mooney (Primary Contact, Project Lead) 

303-384-6782, david_mooney@nrel.gov 

Glenn Doyle (DOE/GO), DOE PV Center of Excellence 

 303-275-4706, glenn.doyle@go.doe.gov 

 Howard Branz (NREL) C-Si PV: Materials and Device R&D, 

303-384-6694, howard_branz@nrel.gov 

 Richard Matson (NREL) University C-Si Research Project 

 303-384-6431, rick_matson@nrel.gov 

 Brent Nelson (NREL) Science & Technology Facility 

303-384-6407, brent_nelson@nrel.gov 

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

FY 2006 Budgets: $4,397K (NREL), $950K (DOE/GO) 

Objectives 

•	 Further the fundamental understanding and implementation of performance-enhancing features 

of low-cost, high-efficiency crystalline silicon (c-Si) solar cells. 

•	 Support the Crystalline Si Center of Excellence for optimizing solar cells through 

university/industry collaborations on production processes.
 

•	 Direct university research addressing fundamental technological concerns to the c-Si PV industry. 

•	 Design and procure a c-Si cluster tool for conducting process integration R&D in the new NREL 

Science & Technology Facility. 

•	 With the introduction in 2006 of the Solar America Initiative (SAI), c-Si R&D efforts will address, 

as required, levelized cost of energy targets (in residential, commercial, and utility markets) and 

manufacturing/installed capacity targets under the SAI. Assessment of selected Technology 

Pathway Partnerships (TPPs) will be conducted and R&D opportunities that are complementary 

to TPP goals will be considered. 

Accomplishments 

•	 Achieved a record efficiency for p-wafer silicon heterojunction solar cells with a confirmed 

efficiency of 18.2%. This 1 cm2

 cell has a-Si contacts on both sides and an open-circuit voltage of 

0.667 V (NREL Silicon Materials and Devices). 

•	 Synchrotron measurements provided first evidence that transition metals interact within silicon 

during the precipitation process to form complex silicides, a process subsequently termed 

"internal eutectic gettering" (University of California, Berkeley). 

•	 Modeling showed that 18%–20%-efficient low-cost cells with screen-printed contacts using 100 to 

200 μm-thick c-Si wafers can reduce the levelized cost of electricity to 5–10 ¢/kWh (Georgia 

Institute of Technology, Rohatgi). 

•	 Solar cell processing equipment to scale up experimental cell areas from 4 cm2

 to 149 cm2 has 

been installed at the Georgia Tech. 

•	 A Georgia Tech (Danyluk)/NREL collaboration to implement CAMX software for data collecting, 

distribution, and processing is active and will benefit researchers as well as the PV industry's 

manufacturing processes. 

•	 Research in cell processing coupled with development of new processes and controls for 

manufacturing 4 cm2

 commercial cells has resulted in significant cost reductions in processing 

cells with efficiencies in the 16%–20% range. Application of these process improvements to 

larger, thinner wafers continues (DOE Center of Excellence). 

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28
 

 

 

 

 

 

 

•	 Used the scalable hot-wire chemical vapor deposition (CVD) technique to deposit 11 microns of 

epitaxial Si at 110 nm/min on a Si wafer at the glass-compatible temperature of 615°C. With 

quality improvements and a suitable seed layer on glass this technique could be used to develop 

thin crystal Si layers on inexpensive substrates (NREL Silicon Materials and Devices). 

•	 Project management oversaw the construction of a cluster tool to support silicon research to be 

delivered to NREL in January 2007. 

Future Directions 

Note: Following the formation of the SAI, R&D on c-Si will no longer take place within the Crystalline 

Silicon Project. Instead the efforts will be distributed within the National Center for Photovoltaics 

(NCPV) in a way that aligns with complementary R&D efforts and the NCPV organizational structure. 

•	 Study and mitigate factors limiting the high-yield manufacturing of cost-effective PV devices by 

identifying and addressing issues related to c-Si materials, cells, and modules. 

•	 The University Crystalline Silicon Photovoltaic R&D (Center of Excellence) award was recompeted 

during 2006. Georgia Tech was selected for negotiation of a new award. Completion of the current 

award scope ended in December 2006. 

•	 The c-Si university c-Si research effort will be (1) winding down in anticipation of its resurrection 

under the SAI and (2) continuing at a considerably reduced funding level in FY 2007 in the form of a 

consortium of six universities, NREL, and at least one PV company investigating the mechanisms for 

defect cluster formation in Si solar cells. 

•	 NREL’s Silicon Materials and Devices Group will use our improving heterojunction passivation and 

contacting technologies in a variety of device configurations once single-crystal efficiencies on both na dn p-type wafers are brought near 20%. This technology can be particularly valuable on 

multicrystalline and thin crystal silicon materials and in interdigitated cell configurations. 

•	 NREL’s Silicon Materials and Devices Group will grow epitaxial Si layers and solar cells on a variety 

of Si seed layers on glass to test the viability of our epitaxy at glass-compatible temperatures. 

1. Introduction 

Crystalline silicon solar cells have demonstrated a 

long and consistent history of continued 

performance improvements and cost reductions. 

The consensus in the global c-Si PV community is 

that this trend will continue with appropriate 

investment Si PV R&D. Given the abundance of 

possible solar-grade and purer silicon, the 

evolving methods for expanding the utility of the 

anticipated silicon feedstock, and a considerable 

technological infrastructure to leverage any 

improvements in the cost and/or performance 

characteristics of c-Si PV, the global bet (with a 

≥90% market share) is placed on c-Si PV for the 

foreseeable future—at least the next decade. As 

such, there is a clear case for a very significant 

increase in U.S. engagement in the global c-Si PV 

competition in parallel with its existing PV R&D 

programs. 

There were four distinct components within the 

DOE c-Si solar cell research effort for FY 2006: (1) 

the NREL in-house (fundamental and exploratory) 

research effort; (2) the DOE-funded PV Center of 

Excellence at Georgia Tech; (3) the subcontracted 

university research effort; and (4) NREL's new 

Science & Technology Facility (S&TF), where 

integrated material and device research, as well 

as cell manufacturing R&D, will be performed by 

individuals and groups throughout the c-Si 

research community. 

2. Technical Approach 

2.1 Silicon Materials and Devices Group at NREL 

This group researches options for both near-term 

and future photovoltaic technology improvements 

using both wafer and film forms of silicon. Our 

main project in wafer silicon photovoltaics is the 

development of silicon heterojunction (SHJ) 

surface passivation and solar cell devices. The 

SHJ is fabricated by putting ultrathin hydrogenated 

amorphous silicon (a-Si:H) passivation layers on 

c-Si; this is a key step toward fabrication of highefficiency silicon solar cells at low temperatures 

(<250oC). We deposit the a-Si:H layers by hot-wire 

chemical vapor deposition (HWCVD) to avoid any 

ion-bombardment damage of the high-quality Si 

wafers that are employed. 

A longer-term, high-risk goal is to develop crystal 

Si films on glass that can be used to fabricate 15% 

PV cells. We aim for crystal Si efficiencies at 

29

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costs per unit area comparable to the thin-film 

manufacturing cost potential (~$100/m2

). 

Development of this wafer equivalent on glass 

requires excellent Si seed layers on the glass and 

a capability for rapid epitaxial thickening with 

about 10 microns of Si at glass-compatible 

temperatures below 700°C. We are using 

HWCVD for epitaxial deposition because it is a 

promising candidate capable of high-rate epitaxy 

and can be scaled for large-area manufacturing. 

16th Workshop on Crystalline Silicon Solar Cells 

and Modules: Materials and Processes. Invaluable 

to the c-Si community at large, these annual 

NREL-sponsored workshops are a technical and 

practical mainstay for the whole community, 

theoreticians and industrialists alike. 

2.2 DOE/GO Center of Excellence 

Negotiation of this new award is ongoing, but the 

key research objectives are to advance the current 

state of c-Si solar cell technology to make it more 

competitive with conventional energy through R&D 

in areas such as: low-cost, high- performance 

screen-printed metallization; gettering and 

passivation of defects in low-cost c-Si materials; 

cost-effective formation of rear contacts with low 

back surface recombination velocities/high back 

surface reflectance; and low-cost fabrication of 

thin c-Si solar cells. The project is designed to 

enhance fundamental and applied research 

appropriate for education and advanced degrees, 

while also performing industry-relevant research. 

2.3 University Crystalline Silicon Research Project 

This work complements the foregoing R&D by 

providing applied and exploratory research in c-Si 

on topics that serve industry's technical concerns. 

The topics are determined by a consensus among 

the c-Si PV industry, universities, and NREL staff 

and management. Current topics include 

development of improved silicon nitride 

hydrogenation, methods for handling and 

processing thin wafers with high yield, 

neutralization of bad regions in wafers, rearsurface passivation, hybrid heterojunction 

emitters, and innovative c-Si technologies. 

Task Title FY 2006 

Budget ($K) 

NREL c-Si Materials and Devices 

Group 2,470. 

University c-Si PV Research Project 500 

Initiative in PV Manufacturing 100 

DOE/GO Center of Excellence 

Georgia Tech 950 

Process integration (S&TF): c-Si 

component 580. 

Technical coordination 743 

3. Results and Accomplishments 

3.1 Silicon Materials and Devices Group (NREL) 

The group obtained a high of 667 mV on textured 

p-type float-zone (FZ) c-Si wafers in the doubleheterojunction structure (front n/i SHJ emitter and 

back i/p SHJ contact). This result indicates that 

both back- and front-surface passivation are 

excellent. For comparison, replacing the SHJ back 

contact on a p-type c-Si wafer with an Al backsurface field (BSF) yields a Voc of only 636 mV. 

Although traditional alloyed BSF contacts have 

excellent contact-resistance characteristics, 

HWCVD a-Si:H back contacts are superior for 

their combined passivation and current-transport 

capabilities. The 18.2% conversion efficiency we 

obtain with HWCVD is the best yet reported on ptype crystalline Si. 

Other research focused on improvements to 

crystalline silicon on glass. We found that HWCVD 

a-Si:H films crystallize about five times faster than 

plasma-enhanced chemical vapor deposition 

(PECVD) a-Si:H. Because these rapidly 

crystallizing HWCVD films were also grown at

higher rates, up to 110 Å/s, they might replace 

PECVD films in thin polycrystalline Si 

photovoltaics or other devices crystallized from 

a-Si:H. However, grain sizes may be slightly 

smaller than films crystallized from PECVD a-Si:H. 

3.2 DOE Center of Excellence for Photovoltaic 

Research, Education, and Collaboration Program 

Results included fabricating: (1) a 42-cm2 

Czochralski (CZ) silicon cell of 18.6% efficiency on 

low-cost materials using conventional furnace 

processing and photolithography; (2) 4-cm2

 cells 

with a target efficiency of 17%–20% by 

implementing an optimized P-diffusion profile in 

rapid thermal processing and screen-printed Aldoped back surface field with in-situ oxide emitter 

passivation; (3) 4-cm2

 commercial cells with target 

efficiency of 16%–19% on commercial substrates 

by more effective monitoring/control of wafer 

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30
 

 

 

 

 

 

 

 

 

 

 

temperatures during belt furnace processes and 

stabilization of the belt furnace before processing 

to improve uniformity/reproducibility of results in 

conjunction with Ag paste with a n+ emitter, lowfrequency PECVD SiN film, and metallization firing 

in a belt furnace or rapid thermal processing; (5) a 

selective emitter and bifacial and intermediateband solar cells cells on commercial materials with 

target efficiencies of 17%–20% on FZ and CZ Si 

using high sheet resistance emitters and surface 

texturing: 17%-efficient bifacial cells on FZ Si. 

3.3 University c-Si Research Project 

Beyond the technological mandates for lower cost, 

higher performing, and more durable solar cells 

and modules, provisions of the DOE Solar 

Program Multi-Year Technical Plan (MYTP) 

specifically call for fundamental R&D involving our 

colleges and universities and, as a corollary, the 

development of the next generation of solar 

technologists as a complement to the NREL PV 

research. This directed, yet fundamental and 

exploratory, research project covers a spectrum of 

R&D, ranging from synchrotron studies of atomiclevel defects in solar-grade c-Si to collaborative 

manufacturing research efforts, and from 

theoretical studies of the role of hydrogen in 

passivation to characterizing the effect of crucible 

contaminants, wafer sawing, and device 

processing on device performance. Some results 

of these studies include the following. 

Texas Tech. Researchers conducted theoretical 

studies focused on the identification and 

characterization of electrically active defect 

centers in Si PV devices as well as on the origin of 

their electrical activity and the possibility of 

passivation with hydrogen. At Lehigh University, 

Texas Tech's experimental counterpart, 

researchers focused on the detection and 

measurement of H passivation of Si from SiN 

antireflection AR coatings. 

UC Berkeley. This group observed and studied a 

formerly unknown alloy phase with fluorite-type 

structure containing Ni, Fe, Cu, and Si, which are 

found as precipitates in multicrystalline silicon. The 

analysis of extended X-ray absorption finestructure microspectroscopy (m-EXAFS) 

measurements provided first evidence that 

transition metals interact during precipitation within 

silicon and form complex silicides. This finding 

may have far-reaching consequences for both 

understanding precipitation behavior of transition 

metals in silicon and for reduction of their 

detrimental impact on solar cell efficiency. 

Georgia Tech (Rohatgi). Researchers developed 

and applied their PV module manufacturing cost 

model in conjunction with the Solar Advisor Model 

from NREL to show that 18%–20%-efficient lowcost cells with screen-printed contacts using 100– 

200-μm-thick c-Si wafers can reduce the levelized 

cost of electricity to 5–10 ¢/kWh. By controlling the 

contact firing process, efficiencies approaching 

19% on 4-cm 2

 FZ Si cells and exceeding 17% on 

149-cm2

 FZ Si cells were achieved. A model to 

predict the impact of material inhomogeneity on 

the Voc of mc-Si cells was also developed. 

Georgia Tech (Danyluk) and University of South 

Florida (USF). This group developed a model for 

handling stresses in c-Si wafers produced by a 

Bernoulli gripper, measured breakage stresses in 

150–200-mm-thick BP wafers, and developed 

methods to extract residual stresses from 170­

micron-thick polycrystalline wafers. USF 

performed Finite Element Analyses modeling of 

different vibration modes to assess the sensitivity 

of the resonance ultrasonic vibration method 

versus crack length. They also have been working 

extensively with a number of PV industrialists on 

the issues of handling thin Si wafers. Such 

relationships are critical and speak well of the 

relevance and effectiveness of the project. 

Duke University. Performed theoretical studies of 

the mechanisms of low-temperature precipitate 

dissolution using optical processing and vacancy 

injection. Al gettering of metallic precipitates, 

carried out using optical processing, is able to 

accomplish the same effect that takes tens of 

hours under thermal annealing at 700°C. Possible 

mechanisms involved in optical-processing 

gettering were proposed and demonstrated via 

physical modeling and simulations. 

California Institute of Technology. Having 

previously developed processes for the formation 

of large-grained polycrystalline templates for 

epitaxial growth and low-temperature Si epitaxy 

via HWCVD, this year CalTech focused on 

growing high-quality p/n junctions with poly-Si 

growth via HWCVD. After evaluating several 

different growth processes for n/p and p/n junction 

formation with and without dilution, they were able 

to obtain best-quality p/n junctions by growth at 

250°C without introducing hydrogen for a record 

open-circuit voltage of 430 mV. 

North Carolina State University (NCSU). The coprecipitation dynamics of O and C in 

multicrystalline sheet silicon were examined 

experimentally. A model based on the synergetic 

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Photovoltaic R&D

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role of intrinsic point defects on O/C precipitation 

was proposed by comparing experimental results 

with numerical modeling. 

3.3 Crystalline Silicon PV Research Project 

Management 

This supports the management activities needed 

for high-quality research within project budgets. 

Activities include peer reviews, solicitations for 

proposed research, budget planning, contract 

negotiation, contract monitoring, reporting of 

project results through conferences and 

publications, and partnering with other 

government, state, and private entities to leverage 

related research. 

3.4 Science and Technology Facility 

The silicon cluster at the S&TF was substantially 

completed in FY 2006. It consists of a central 

robot in a vacuum chamber with ten ports around 

the periphery. Eight of the ten ports are being 

completed with the cluster tool. Of the remaining 

two, one is for the transport pod interface and one 

is left open for future expansion—probably an 

analytical chamber. The eight capabilities 

substantially complete are a load lock, plasmaetching chamber, sputtering chamber for 

transparent conducting oxides, PDCVY chamber 

for depositing silicon nitride passivation layers, two 

PECVD a-Si:H chambers, and three combinatorial 

chambers for depositing thin silicon layers by 

either PECVD or HWCVD (see Fig. 1). 

 Fig. 1. The silicon cluster tool at the S&TF 

4. Planned FY 2007 Activities 

In accordance with the formation of the SAI, 

activities included under the c-Si Project in 

FY 2006 have been redistributed within the NCPV 

for FY 2007, thus dissolving the intended 2006 

DOE c-Si Project as such. Crystalline silicon R&D 

will remain a strong, well-coordinated activity in 

the NCPV, however, as these activities will be 

included in areas of the NCPV that align with their 

function and that best complement c-Si activities 

funded under SAI. Planned activities are to: 

•	 Issue a request for letters of interest for new 

university c-Si research projects. 

•	 Finalize current research and development on 

high-efficiency, low-cost c-Si production 

processes. 

•	 Extend three of the six university projects to 

the end of FY 2007 (Texas Tech/Lehigh, 

NCSU, and Georgia Tech/USF). Integrate 

these into a consortium of other universities 

(Duke, Washington State University, UC 

Berkeley) and NREL in-house research 

groups in a project to characterize and 

neutralize the performance-crippling defect 

clusters found in multicrystalline Si. 

5. Major FY 2006 Publications 

M.-H. Du, H.M. Branz, R.S. Crandall, and S.B. 

Zhang, “Self-trapping enhanced carrier 

recombination at light-induced boron-oxygen 

complexes in silicon” Phys. Rev. Lett. 97, 256602 

(2006). 

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

Jones, and H.M. Branz, “Significant improvement 

in silicon chemical vapor deposition epitaxy above 

the surface dehydrogenation temperature,” J. 

Appl. Phys. 100, 93520 (2006). 

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

Stradins, and H.M. Branz, “Breakdown physics of 

low-temperature silicon epitaxy from silane 

radicals” submitted to Phys. Rev. B 74, 235428 

(2006). 

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

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

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

hydrogenated amorphous silicon” Appl. Phys. Lett. 

89, 161910 (2006). 

Y. Yan, M. Page, T.H. Wang, M.M. Al-Jassim, 

H.M. Branz, and Q. Wang, "Atomic structure and 

electronic properties of c-Si/a-Si:H 

heterointerfaces," Appl. Phys. Lett. 88, 121925 

(2006). 

G. Yue, B. Yan, G. Ganguly, J. Yang, S. Guha, 

C.W. Teplin, “Material structure and metastability 

of hydrogenated nanocrystalline silicon solar 

cells,” Appl. Phys. Lett. 88, 263507 (2006). 

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32
 

 

 

 

 

 

 

 

C.W. Teplin, D.S. Ginley, H.M. Branz, “A new 

approach to thin crystal silicon films on glass: 

Biaxially textured silicon on foreign template 

layers,” J. Non-Cryst. Solids 352, 984-988 (2006). 

T.H. Wang, E. Iwaniczko, M.R. Page, D.H. Levi, Y. 

Yan, H.M. Branz, and Q. Wang, “Effect of emitter 

deposition temperature on surface passivation in 

hot-wire chemical vapor deposited silicon 

heterojunction solar cells," Thin Solid Films 501, 

284-287 (2006). 

A. Carvalho, R. Jones, M. Sanati, S.K. Estreicher, 

J.Coutinho, and P.R. Briddon, "First-principles 

investigation of a metastable boron-oxygen 

interstitial pair in Si," Phys. Rev. B 73, 245210 

(2006). 

Residual Stresses in Polycrystalline Sheet Silicon 

and Their Relation to Electron-Hole Lifetime.” He, 

S., Danyluk, S., Tarasov, I., and Ostapenko, S., 

Appl. Phys. Lett., 89 (11), 2006, p. 111909. 

A. Belyaev, O. Polupan, W. Dallas, S. Ostapenko, 

D. Hess, and J. Wohlgemuth, “Crack Detection 

and Analyses Using Resonance Ultrasonic 

Vibrations in Full-Size Crystalline Silicon Wafers,” 

Appl. Phys. Lett. 88, 111907-3 (2006). 

X. Brun and S.N. Melkote, “Experiments and 

Modeling of Silicon Wafer Handling Using a 

Bernoulli Gripper,” Proceedings of the 

International Symposium on Flexible Automation, 

July 10-12, 2006, Osaka, Japan. 

M. Sanati and S.K. Estreicher. "Oxygen-Boron 

Complexes in Si," Physica B 133, 376-377 (2006). 

A. Carvalho, R. Jones, M. Sanati, S.K. Estreicher, 

J.Coutinho, and P.R. Briddon, "First-principles 

investigation of a metastable boron-oxygen 

interstitial pair in Si," Phys. Rev. B 73, 245210 

(2006). 

D. West and S.K. Estreicher. "First-principles 

calculations of vibrational lifetimes and decay 

channels," Phys. Rev. Lett. 96, 115504 (2006). 

6. University and Industry Partners 

These organizations partnered in the project’s research activities during FY 2006 (no cost share). 

University c-Si PV Research Project 

University/Principal 

Investigator Location/e-mail Description/Title of Research Activity FY 2006 ($K) 

Caltech 

Harry Atwater 

Pasadena, CA 

haa@caltech.edu Si Passivation and CVD of Si Nitride 37.5 

UC Berkeley 

Eicke Weber 

Berkeley, CA 

weber@gsonet.org Efficiency Improvement of Si Solar Cells 101.4 

Georgia Tech 

Ajeet Rohatgi 

Atlanta, GA 

ajeet.rohatgi@ee.gatech.edu 

Fundamental R&D for Improved 

Crystalline Solar Cells 

101.2 

Texas Tech 

Stefan Estreicher 

Lubbock, TX 

Stefan.estreicher@ttu.edu Hydrogen Passivation of Si Solar Cells 97.8 

NCSU 

George Rozgonyi 

Raleigh, NC 

rozgonyi@ncsu.edu Improved Efficiency and Yield R&D 71.2 

Georgia Tech 

Steven Danyluk 

Atlanta, GA 

steven.danyluk@ma.gatech.edu 

Birefringence of Stresses in Thin Si 

Sheet 100.8 

Georgia Tech 

Steven Danyluk 

Atlanta, GA 

steven.danyluk@ma.gatech.edu Initiative in Photovoltaic Manufacturing 100.0 

DOE Center of Excellence in Crystalline Silicon Project 

University/Principal 

Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2006 

($K) 

Georgia Tech 

Ajeet Rohatgi 

Atlanta, GA 

ajeet.rohatgi@ee.gatech.edu 

University Photovoltaic Research, 

Education, and Collaboration 

Program 

950 

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____________________________________________________________________________________ 

 

 

____________________________________________________________________________________ 

 

Electronic Materials and Devices 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: John Benner, 303-384-6496, john_benner@nrel.gov 

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

FY 2006 Budget: $8,048K 

Objectives 

•	 Apply combinatorial methods to identify optimum material and demonstrate conductivity 

>6200 S/cm in an In-Ti-O system. 

•	 Initiate deposition and processing of CIGS using inkjet-written precursor layers. 

•	 Complete specification and engineering design of copper indium gallium diselenide (CIGS) 

platform for the Science and Technology Facility (S&TF). 

•	 Demonstrate 17%-efficient thin (<1 micron) CIGS solar cell. 

•	 Demonstrate 40%-efficient PV conversion. 

Accomplishments 

•	 New combinatorial capabilities for Raman, work function, deposition, and elemental analysis. 

•	 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 organic photovoltaics (OPV). Obtained a 4.2%­

efficient bulk heterojunction cell and >3% inverted OPV solar cells using ZnO anodes. 

•	 19.52%-efficient CIGS/CdZnS solar cells. 

•	 17.1%-efficient, 1-μm, thin CIGS solar cell and 15.02%-efficient thin CdTe cells. 

• Cd1-xMgxTe/CdS solar cells for tandem cell applications 

•	 Lowered series resistance of inverted three-junction cells for 40% performance under
 

concentration. 

•	 Demonstrated GaInNAs 1-eV cells with good depletion widths for use in four-junction cells 

•	 Achieved record efficiency in lattice-mismatched GaAsP on silicon for low-cost multijunction cells. 

Future Directions 

•	 Transfer Si ink technology and develop 10% CIS solar cell from solution precursors. 

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

•	 Install and operate polycrystalline thin-film cluster tool in the S&TF. 

•	 Achieve >40% efficiency concentrator solar cell. 

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

1. Introduction 

The Electronic Materials and Devices Project 

carries out research in semiconductor materials, 

device properties, and fabrication processes to 

improve the efficiency, stability, and cost of 

photovoltaic solar energy conversion. This 

research can be characterized in three forms. 

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 PV. Through these 

activities, the project supports both flat-plate and 

concentrator 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. 

Our base of operations in the United States 

presents several unique opportunities for our PV 

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34
 

 

 

 

 

 

 

 

 

 

community. First, our industry leads the world in 

the development of thin-film technologies. This is 

the fastest growing segment of the PV market and 

is widely perceived to hold significant production 

cost advantages. Second, the U.S. solar 

resources are well suited to the use of 

concentrator system technologies for large-scale 

power generation. Finally, 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. Exploration and development of 

technologies to exploit these three opportunities 

compose the three primary tasks of the Electronic 

Materials and Devices (EM&D) Project. 

2. Technical Approach 

The project is composed of three primary research 

tasks and management. The management task 

coordinates project planning and operations within 

the PV Subprogram and interactions with projects 

of related interests from other agencies and 

private sources. Funds are also consolidated in 

this task for planned major costs for equipment 

upgrades and unanticipated major repairs. The 

research tasks and areas of investigation follow. 

2.1 Process and Advanced Concepts 

•	 Develop combinatorial materials science 

deposition, diagnostics, and data analysis 

tools: application to transparent conducting 

oxide (TCO) materials. 

•	 Inkjet processing of electronic materials: 

application to metallization and semiconductor 

materials. 

•	 Organic and nanocomposite solar cells 

•	 In-situ diagnostics for thin-film growth and new 

analytical diagnostics 

•	 Cooperative Research and Development 

Agreements (Heliovolt, Evergreen Solar). 

2.2 Thin-Film Polycrystalline Compounds 

•	 Examination of device performance in 

progressively thinner absorber layers. 

•	 TCOs for thin-film solar cells 

•	 Develop simplified and improved processes 

for CdTe and CIS manufacture. 

•	 Thin-film intrinsic device stability 

•	 Wide-bandgap absorbers for polycrystalline 

thin-film tandem solar cells. 

2.3 Concentrator Crystalline Cells 

•	 Inverted growth of a lattice-mismatched cell for 

separation from the substrate 

•	 Dilute nitrides for four-junction 

GaInP/GaAs/GaInAsN/Ge or similar cell 

•	 GaAsP cells on silicon. 

Task Title FY 2006 

Budget ($K) 

Processes and Advanced 

Concepts 2,379 

Thin-Film Polycrystalline 

Compounds 3,195 

Concentrator Crystalline Cells 2,214 

EM&D Technical Coordination 260 

3. Results and Accomplishments 

3.1 Process and Advanced Concepts 

The Process and Advanced Concepts Team 

works with other groups at NREL to explore new 

processing approaches, such as combinatorial 

science, ink-based electronic materials deposition, 

and hybrid nanostructures for solar energy 

conversion. In addition, we facilitate an integrated 

approach between staff and engineers to develop 

new tools and to install tools in National Center for 

Photovoltaics (NCPV) laboratories. 

Combinatorial materials science offers a powerful 

approach to understanding the science and 

technology of multicomponent systems. Often 

information can be acquired 20 to 50 times faster 

than when using conventional approaches. To 

implement this, we are developing a suite of 

deposition, analysis and database, and mining 

tools to be broadly applicable to NCPV activities. 

The basic scientific approach can be viewed as 

consisting of three basic areas: (1) deposition of 

libraries, (2) analysis of libraries, and (3) mining of 

data. 

Deposition of Libraries. We have developed a 

number of deposition capabilities for producing 

libraries, including two sputter systems, which 

produce compositionally graded samples, and a 

multihead inkjet printing system, which can deposit 

samples with either continuously graded or 

discrete local compositions. The tools so far 

developed have shown a versatile capability for 

depositing optoelectronic materials, and our focus 

has been on TCO materials. These capabilities 

have let us rapidly develop state-of-the-art 

materials, attracting the interest of companies 

such as First Solar, HP, Gentex, Evergreen Solar, 

and Heliovolt. 

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Analysis of Libraries. A major focus in the 

program has been the development of analytical 

tools specific to combinatorial research and to 

coordinate this effort with NREL’s Measurements 

and Characterization Division to ensure that 

eventually most tools will be able to handle 

combinatorial libraries. We have continued to 

develop tools to facilitate the analysis of key 

optoelectronic properties, as well as to correlate 

those to compositional, structural parameters as a 

function of process conditions. This year, we have 

worked on developing an improved conductivity 

mapping tool, an in-house micro-Raman tool, a 

work-function mapping tool, and new composition 

mapping tools. 

Mining of Data. This consists of two separate 

areas. First is the development of information 

archiving and display for the vast amounts of data 

being acquired. We have been successful in 

developing databases and data-handling 

approaches that make data taking and initial 

analysis quite facile. We have also initiated a 

project with the NREL Scientific Computing Center 

to investigate data base structures and inputoutput approaches compatible with the 

combinatorial methodology and tools. This 

potentially will provide a generic database 

approach for the NCPV. The second area is in the 

development of smart software tools to analyze 

multidimensional phase space so as to extract key 

data and trends. This is more complex, and we are 

prototyping initial tools to better understand what 

is most suitable to electronic materials needs. 

We now have increasingly sophisticated tools for 

analyzing the combinatorial data to extract key 

electronic properties. For TCOs, we have 

developed tools to aid in the display and analysis 

of optical data. In Fig. 1, we use color intensity to 

show an optical reflectivity map from 0.3–25 μm 

for a combinatorial TCO library. From the plasma 

wavelength (λp), which is determined by 

simultaneous fitting of the reflection and 

transmission data to the Drude (free-carrier) model 

and overlaid in black, one can determine the 

electrical carrier concentration. 

Fig. 1. Air annealing of IZO libraries from RT to 

600°C showing a remarkable stability of the 

amorphous phase and the formation of a new 

phase at the amorphous/InO phase boundary. 

A second major area of investigation is 

development of new technologies for very low-cost 

processing. This includes investigation of 

solution-based precursors for atmospheric 

processing, inkjet delivery of those precursors, 

highly processible organic solar cells, and new 

processes to make solar-grade silicon from thinfilm precursors. A key current focus is to develop 

inkjet-printable precursors for solar cell materials, 

including materials for noncontact deposition of 

contacts for Si solar cells and precursors to CISbased solar cell absorbers. We are also initiating 

efforts to direct-print organic materials for OPV 

devices. This approach has a number of inherent 

advantages, including that it is very materials 

efficient and allows direct patterning, writing on 3D 

and flexible surfaces, and the use of multiple 

sources to write complex compositions or layers. 

In the area of contacts for solar cells, we have 

developed a new set of metals and a new reaction 

layer that is Pb free and burns through SiNx 

antireflection layers as low as 600oC. 

A key activity area this year has been the initial 

development of solution-based binary and ternary 

precursors to CIS materials. In theory, combining 

solution precursors with rapid thermal processing 

techniques might offer a new route for 

manufacture of CIS-based solar cells. We have 

developed a set of initial precursors (five 

disclosures) and the process to phase-pure CIS as 

shown in Fig. 2. 

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36
 

 

 

 

 

 

 

Fig. 2. X-ray diffraction illustrates the formation of 

phase-pure CIS from solution-based precursors 

sprayed at 175-180°C combined with rapid thermal 

processing for 5 min. at 500°C in argon. This work 

has led to a close developmental effort with Helivolt 

looking at the potential for using solution-based 

precursors combined with FASST®

 processing. 

In the OPV area, we have developed a world-class 

processing capability allowing for the very 

controlled processing of organic-inorganic 

composite structures. Using these tools, we have 

already obtained a 4.2% bulk heterojunction 

organic solar cell and believe this will enable us to 

rapidly move forward exploring new inorganic, 

organic, and interfacial device structures. We 

are also combining this task with the two 

previously discussed ones to use inkjet printing as 

a combinatorial tool to rapidly explore organic 

device configurations and process conditions. 

Along the lines of developing new process 

methodologies for low-cost, high-efficiency solar 

cells, we have been investigating the methodology 

of the nucleation of amorphous Si when it 

crystallizes to crystalline silicon. Work has been 

done by in-situ transmission electron microscopy 

and X-ray diffraction analysis, combined with other 

analytical approaches; an initial paper has been 

accepted and a model has been proposed and is 

being validated. Figure 3 shows some of the 

differences observed in the behavior of high- and 

low-hydrogen hot-wire material and of plasmaenhanced chemical vapor deposition (PECVD) 

materials under similar annealing conditions. 

Finally, the engineering team has been 

exceptionally busy in keeping up the design, bid, 

and installation of equipment in the new S&TF. 

System development has been delayed due to 

limited resources. This will continue as both a 

priority and challenge next year. 

Fig. 3. Scanning electron microscopy images of 

silicon films crystallized by annealing. Amorphous 

films were grown by hot-wire chemical vapor 

deposition with both low and high hydrogen 

content and by PECVD. 

3.2 Thin-Film Polycrystalline Compounds 

The Polycrystalline Thin Film Team currently has 

within its technology process portfolio the ability to 

fabricate the world's highest efficiency CIGS and 

CdTe solar cell devices. These processes were 

developed with emphasis necessarily placed first 

on efficiency, as this defines the potential product 

and must precede manufacturing concerns in cost 

and reliability. Recent and planned infrastructure 

improvements will make it possible for us to 

address these shortcomings in the future. New 

tools planned for the S&TF (e.g., vapor transport, 

flexible layer interchange modules) will provide us 

with increased processing latitude necessary to 

develop thinner and improved device structures 

necessary to meet SAI module performance goals 

by 2015. 
 

 

 

 

 

 

 

 

The project leads the development of thin-film 

CdTe, CIGS, and related materials for use in highperformance and stable single-junction solar cells. 

The objectives are to support near-term 

manufacturing, build the knowledge and 

technology base for future manufacturing 

improvements, and sustain innovation that 

supports progress toward the future and the longterm Solar Program goal of 15%-efficient 

commercial modules. Over the past decade, we 

have steadily improved the quality of 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 

all of the above factors might become important. 

The price of indium has risen sharply in recent 

months, and this can have an adverse impact on 

the prospects of our CIS industries. One solution 

is to reduce the thickness of the absorber without 

compromising high efficiency. Presently, our 

absorbers are 2.5–2.75-μm thick, and reducing the 

thickness to 0.5 μm would be desirable. However, 

severe losses are encountered because of 

incomplete generation and enhanced 

recombination. Figure 4 displays this challenge as 

shown in the optical properties of a thin CIGS cell. 

tandem solar cells of semi-transparent CdTe on 

top of CIS set the record at 15.3%. 

High-efficiency (19.52% confirmed) CIGS-based 

solar cells have been fabricated by using a singlelayer, NREL-developed, chemical-bath-deposited 

(CBD) CdZnS buffer layer. The CdZnS buffer 

layer allows higher-energy photons to reach the 

junction in order to increase the short-circuit 

current above that obtained for the CdS layer, 

which was confirmed by comparing the absolute 

external quantum efficiencies for both CIGS/CdS 

and CIGS/CdZnS devices. It was clearly evident 

from the absolute external quantum efficiencies 

that we gained significant current between 300 

80 

60 

40 

20 

0 

%T, A, QE

QE 

Absorption 

T 

R of Cell 

and 500 nm, when a CdZnS buffer layer was 

used. We also did not use an i-ZnO layer for the 

CdZnS buffer layer, which makes it commercially 

favorable technique. The CBD CdZnS thin film 

was obtained from a solution containing CdSO4, 

ZnSO4, thiourea, ammonia, water, and isopropanol. The compositional ratio of Cd:Zn = 

80:20, as analyzed by inductively coupled plasma 

(ICP) analysis. 

The devices were measured by the Cell 

Performance Characterization Group at NREL. 

The cell parameters, in order of open-circuit 

voltage (Voc, current density, fill factor (FF), and 

efficiency (η) are 0.7052 V, 35.515 mA/cm2

, 

77.90%, and 19.52%, respectively. At present, we 

are optimizing the processing condition to obtain 

even higher current and fill factor of about 80%, 

which will produce >20% devices. 

Our group has been the world leader in fabricating 

the most efficient CIGS thin-film solar cells (>19% 

since 2002). The ability to produce very high 

efficiency solar cells is one of the yardsticks by 

which a technology will be judged. Other criteria 

might include material cost, ease of fabrication, 

and throughput. For high-volume production of PV, 

400 600 800 1000 1200 1400nm 

Wavelength (nm) 

Fig. 4. Reflection, absorption, transmission, and 

quantum efficiency of a CIGS solar cell at 0.4-μm 

thickness. 

We have modified our three-stage process to 

deposit thinner CIGS layers. For 1-μm-thick 

absorbers, we have fabricated several solar cells 

with efficiencies ≥17%. The parameters of the 

best solar cell are as follows: Voc=0.678 V; 

Jsc=31.93 mA/cm2

; FF=79.2%, and η=17.15%. 

This is an impressive result for a solar cell that is 

less than half the thickness of our standard cells. 

This achievement meets the FY 2006 milestone of 

demonstrating a 1-μm-thin, 17%-efficient CIGS 

solar cell (Kannan Ramanathan). 

Much of the past NREL development of CdS/CdTe 

high-efficiency devices focused on using relatively 

thick CdTe (~8 μm) layers. It has been argued, 

however, that manufacturing cost and material 

availability concerns, particularly for Te, require 

much thinner CdTe devices. About 2-μm-thick 

CdTe cells with efficiencies of 13%–14% by 

sputtering and electrodeposition have been 

demonstrated. However, these two techniques 

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38
 

 

 

 

 

 

 

 

 

 

 

 

 

 

have very low deposition rates. Deposition of 

~2-μm-thick CdTe film by sputtering requires more 

than 1 hour. CdTe cells that are 12%–13%­

efficient with a 2–4-μm-thick CdTe layer have 

been prepared by close-spaced sublimation (CSS) 

and vapor transport deposition with high 

deposition rates. However, the efficiencies of 

CdTe cells prepared by these two techniques 

need to be improved further. Recent work by our 

group toward reducing CdTe film thickness 

reported that relatively high performance could be 

maintained in CdTe devices with a much reduced 

CdTe film thickness (3.5 μm). 

The NREL Polycrystalline Device Team has 

developed the techniques to prepare highefficiency thin CdTe solar cells by CSS as follows: 

(1) use of modified device structure, 

CTO/ZTO/nano-CdS/poly-CdTe, developed at 

NREL; (2) systematic study of the effects of CdTe 

deposition conditions on film thickness, grain size, 

and pinhole density of CdTe film; and (3) 

optimization of postdeposition CdCl2 treatment 

and back contact. As a result, we have achieved 

a 3.5-μm-thick CdTe cell with an NREL-confirmed 

total-area efficiency of 15.02% (Voc=829.2 mV, 

Jsc=24.13 mA/cm2

, FF=75.06%). The deposition 

time of the CdTe film in this cell was 1 minute. 

To better understand the impact that reduced film 

thickness might have on device stability, we 

recently modified our baseline CdTe process to 

provide a process window for making devices in 

the 11%–12% range with thickness values of 2– 

3 μm. These devices will subsequently be used for 

accelerated stress studies. Thinner CdTe devices 

appear to show considerably more sensitivity to 

precontact etches. The best performance at 

1.9 μm (VOC=0.811, JSC=21.9, FF=63.7, η=11.3%) 

was obtained without a precontact etch. Slightly 

higher performance (VOC=0.826, JSC=22.5, 

FF=64.6, η=12.0%) at 2.3 μm did, however, 

require a slight Br:MeOH etch. Film adhesion was 

also observed to significantly improve with 

reduced CdTe film thickness. No film delamination 

was observed during processing, even with 

excessively long vapor CdCl2 treatments. 

We have developed solar cells based on Cd1­

xMgxTe (CMT) alloy films for use as a top cell in 

two-junction tandem solar cells. Previously we 

had reported efficiencies in the range of 5% to 6 % 

for the devices using the CMT alloy films. CMT 

solar cells were fabricated using polycrystalline 

Cd1-xMgxTe films prepared by co-evaporation of 

CdTe and Mg, a method developed at NREL. The 

postdeposition chloride treatment was carried out 

in the ambient of CdCl2 and MgCl2 vapor mixture 

instead of CdCl2 vapor alone. We also have 

varied the partial pressure of oxygen in the 

ambient. Overpressure of Mg and minimized 

oxygen levels both contributed to preventing the 

loss of Mg from the Cd1-xMgxTe alloy. Even 

though we have deposited Cd1-xMgxTe alloy films 

in a wide range of bandgaps, 1.5 to 2.3 eV, the 

work reported here concentrates on the bandgap 

range of 1.5 to 1.7 eV for two-junction tandem 

solar cell applications. The first sets of devices 

fabricated using the modified postdeposition 

treatment have shown considerable improvement 

in device performance. 

The devices were measured by the Cell 

Performance Characterization Group at NREL as 

summarized in the following table. 

Alloy Eg 

(eV) 

Voc 

(volt) 

Jsc 

(mA/cm2) 

FF Eff. 

Cd0.93Mg0.07Te 1.60 0.796 19.51 51.78 8.04 

Cd0.92Mg0.08Te 1.62 0.845 16.38 52.36 7.25 

CdTe 1.49 0.779 21.09 56.89 9.35 

These initial results with modified postdeposition 

processing demonstrate the potential for high 

device performance of polycrystalline Cd1-xMgxTe 

films fabricated by the NREL-developed technique 

and exceed the milestone for this project for the 

current fiscal year. We are working on 

optimization of the device processing and detailed 

characterization of these devices and expect 

further improvement in device performance. 

3.3 Concentrator Crystalline Cells 

We have embarked on a new approach for 

ultrahigh-efficiency concentrator tandem solar 

cells based on inverted III-V heteroepitaxial 

structures that combine both lattice-matched and 

lattice-mismatched component subcells in a 

monolithic structure. In an ideal tandem solar cell, 

the top solar cell produces most of the total power. 

Each cell underneath contributes progressively 

less, but all serve to boost the total efficiency. 

Thus, the design of a process to produce the 

tandem cell must ensure that the top cell is of the 

very best quality. In conventional designs, where 

the cell is grown on a substrate from the bottom 

cell to the top, all current designs to develop a 

bottom cell at the optimum bandgap of 1 eV 

degrade the crystalline structure of the top cell. In 

the new inverted cell, the lattice-matched GaInP 

and GaAs cells are grown upside down on the 

GaAs wafer, as shown on the left panel of Fig. 5. 

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A transparent grade changes the lattice constant, 

in preparation for growth of the GaInAs (1 eV) 

bottom cell. After growth, the sample is attached 

to a convenient handle, the original substrate is 

removed, and the grids are applied (right). 

These ultrathin devices have many systems-level 

advantages and a realistic potential to exceed 

40%-efficient terrestrial concentrator conversion. 

In initial work, we have already demonstrated a 

record efficiency of 37.9% for concentrator tandem 

cells using our new approach. 

Fig. 5. Inverted growth and handle-mounted thinfilm, high-efficiency solar cell 

The achievement of a 40%-efficient cell this year 

relies on our ability to identify and mitigate all 

series resistance sources in the multijunction solar 

cells. We recently installed and adapted a new 

flash simulator that already has helped identify 

and remove one source of series resistance. 

Our record cell achieved 37.9% efficiency at about 

10 suns of concentration. We estimated that a 

similar cell operating at about 300 suns should 

achieve about 40% efficiency and, therefore, set a 

40% milestone for this year. Unfortunately, the 

repair of a system failure necessitated redesigning 

the cell recipe from scratch. 

After the redesign was completed, we found that 

the internal series resistance of the cell was too 

high to allow efficient operation at 300 suns. 

However, measurement of the series resistance is 

difficult: some cells have shown low series 

resistance in forward bias and higher resistance 

when tested under concentrated sunlight. To 

quantify the series resistance quickly, we needed 

a flash simulator that we could access on a daily 

basis. Fortunately, members of measurements 

team (Keith Emery and James Kiehl) were willing 

to donate the flash simulator they had obtained 

under a project with a Russian group. We moved 

the simulator to the Solar Energy Research 

Facility (SERF) and worked through numerous 

issues with reliable operation of the system. 

The system is now demonstrating its utility, 

allowing us to quantify the series resistance in our 

cells. We found that the series resistance in the 

GaInP top cell is probably coming from a Zndoped AlGaInP layer. The phosphine cylinder we 

are currently using is almost gone, and it is known 

that the impurities are concentrated at the end of 

the life of the cylinder. We were already using a 

purifier, but found that the addition of a second 

purifier on the phosphine line reduced the series 

resistance of the GaInP cell, presumably because 

of a cleaner Zn-doped AlGaInP layer, which is 

known to be especially sensitive to oxygen 

contamination. Although the triple-junction cell was 

quickly implemented in FY 2005, the structure has 

about 50 layers, each of which has the potential to 

introduce series resistance. Identification and 

elimination of each series resistance will take time, 

but will progress much more quickly now that the 

flash simulator can be used as a reliable tool. 

Our second primary area of investigation 

continues the development of 1.0-eV material for 

the fourth junction of a high-performance GaInP, 

GaAs/1-eV material/Ge solar cell. Theoretically, 

GaInNAs has the potential to contribute to a 40%­

efficient four-junction solar cell. The use of 

molecular beam epitaxy (MBE) growth has been 

shown to dramatically improve the photocurrent 

from the GaInNAs junctions, relative to 

organometalic chemical vapor deposition 

(OMCVD). This is probably because of lower 

carbon and hydrogen concentrations. We have 

achieved depletion widths in excess of 1.5 μm for 

bandgaps in the 1.05–1.10-eV range. 

One strategy for increasing the photocurrent for 

GaInNAs cells is using a p-i-n structure with a 

wide depletion width. The use of MBE growth 

results in background carrier concentrations that 

are dramatically lower than those obtained by 

OMCVD. We believe that this may be related to 

the lower carbon and hydrogen contamination for 

the MBE material. Recent results show that the 

background carrier concentration, and hence 

depletion width, depend greatly on the ion content 

of the rf-plasma source used for nitrogen. The use 

of biased plates at the nitrogen source aperture to 

deflect ions away from the growing film 

dramatically reduces the carrier concentration. As 

a result, wide-depletion-width samples have been 

grown, even at the high nitrogen concentrations 

necessary to achieve low bandgaps. 

Photovoltaic R&D

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40
 

 

 

 

 

 

 

 

 

Multijunction solar cells employing III-V top 

junctions with a silicon bottom junction are very 

attractive based on the potential for very high 

efficiency, coupled with relatively low substrate 

cost. A 1.7-eV top junction on an active silicon 

junction has theoretical efficiencies of 34% at 

1 sun AM0 and 44% under 500 suns concentration 

AM1.5G. Increasing the number of junctions has 

the potential for even greater efficiencies. AlGaAs 

and GaAsP have long been prime candidates for 

top junctions on silicon-based multijunction solar 

cells. Organometallic vapor phase epitaxy 

(OMVPE) is a commonly used technique that can 

be employed to fabricate such devices. 

Unfortunately, many challenges to high-quality 

epitaxial growth of these III-V materials on Si exist. 

The most significant is the lattice mismatch and 

thermal expansion mismatch between silicon and 

most III-V materials. Other important challenges 

include silicon surface cleanliness, antiphase 

domain (APD) formation, and interdiffusion. 

Excellent-quality GaAs0.8P0.2 single-junction solar 

cells grown on GaAs substrates have been 

demonstrated using thick compositionally graded 

buffer layers. These mismatched solar cells had 

threading dislocation densities lower than 106 cm-2 

with efficiencies as high as 17.8%, but the growth 

of such cells on Si has proven much more 

challenging. A tandem GaAs0.7P0.3/Si solar cell 

using thermal cycle annealing (TCA) has been 

demonstrated with two-terminal AM0 efficiencies 

of 9.2%. We explore the use of compositionally 

graded buffer layers to grow GaAs0.7P0.3 solar 

cells on Si substrates. In our approach, we grade 

to a composition that is in compression at the 

growth temperature such that, on cooling, the 

strain will be relieved. This is shown in Fig. 6. 

The strain state and composition of these cells was 

determined from (224) grazing incidence reflection 

X-ray diffraction reciprocal space maps (RSM). The 

actual P composition in the GaAs0.7P0.3 was 

adjusted from 25% to 31% to vary the bandgap from 

1.7 to 1.8 eV. The passivating Ga0.6In0.4P layers 

were carefully lattice matched to the GaAs0.7P0.3 

junction material using this information. The thermal 

expansion mismatch of III-V grown on Si tends to 

stress the layer toward tension on cooling. The fact 

that the X-ray data show very little strain at room 

temperature indicates that the layers were grown 

with significant residual compressive strain at 

growth temperature. When III-V layers are grown to 

be stress free on Si at growth temperature, large 

tensile stress on cooling can result in cracking of 

the grown film, which these cells did not exhibit. 

Fig. 6. Schematic of a GaAsP-on-Si solar cell 

We have demonstrated lattice-mismatched p-on-n 

GaAs0.7P0.3 cells on silicon using a compositional 

step-graded buffer. The performance of our devices, 

with efficiencies of about 10%, rivals or surpasses 

previous reports of AlGaAs and GaAsP solar cells 

grown on Si using thermal cycle annealing. The 

internal quantum efficiency (QE) of some 

GaAs0.7P0.3 solar cells exceeded 80%. The wide 

depletion regions in cells with undoped bases help 

to achieve the highest QEs. Intentional Se doping 

in the base of MG228 show that the QE remains 

relatively high, even for narrower depletion widths. 

However, further reduction in threading dislocation 

density will be needed to realize the predicted 

efficiencies of this potentially low-cost structure. 

4. Planned FY 2007 Activities 

During FY 2007, much of our attention will be on 

relocating facilities and building new tools in the 

new S&TF. This is an important milestone for the 

PV Subprogram, requiring significant attention 

during the first half of the year. Despite this 

interruption, this project will also complete several 

other accomplishments, including: 

•	 Install, debug, and operate the silicon cluster 

tool, the first major tool installed in the Process 

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Development and Integration Laboratory 

(PDIL) at the S&TF. 

•	 Demonstrate inkjet printing on whole cells with 

ohmic contracts processed by rapid thermal 

processing. 

•	 Validate readiness of the CIGS cluster tool by 

performing acceptance tests at NREL. 

•	 Evaluate inverted triple-junction solar cell 

under 300 suns illumination 

5. FY 2006 Special Recognitions, Awards, and 

Patents 

Numerous project staff have been chosen by their 

peers to lead professional organization activities 

as general chair, program chair, session 

organizer, session chair, tutorial instructor, and 

similar honors. Two of the more notable of these 

recognitions are: 

•	 Dr. David Ginley served as General Chair of 

the Fall 2005 Materials Research Society 

Meeting. Subsequently he was selected to be 

Secretary of the Society. 

•	 Dr. Timothy Coutts served as Program Chair 

of the 4th World Conference on Photovoltaic 

Energy Conversion. He has been selected to 

be General Chair of the 33rd IEEE 

Photovoltaics Specialists Conference. 

The project also leads the entire lab in generation 

of new intellectual property, filing 12 patents, 

which is more than a third of all of the records of 

invention from NREL in FY 2006. During the year, 

four of the inventions reported in earlier years 

were granted patents. Titles of these, and the first 

listed inventor, include: 

•	 Method for Producing High Carrier Concentration P-Type Transparent Conducting 

Oxides, X. Li 

•	 Stacked Switchable Element and Diode 

Combination with a Low Breakdown Switchable Element, Q. Wang 

•	 High Resolution Metal Deposition by Ink Jet 

Printing of Organometallic Silver Compounds 

from Aqueous and Organic Solvents under 

Mild Reducing Conditions at Low Temperature 

in Air, D. Ginley. 

6. Major FY 2005 Publications 

Teplin, C.W.; Ginley, D.S.; Branz, H.M., "A new 

approach to thin film crystal silicon on glass: 

Biaxially-textured silicon on foreign template 

layers." Journal of Non-Crystalline Solids 2006, 

352, (9-20), 984-988. 

Mahan, A.H.; Roy, B.; Reedy, R.C., Jr.; Readey, 

D.W.; Ginley, D.S., "Rapid thermal annealing of 

hot wire chemical-vapor-deposited a-Si:H films. 

The effect of the film hydrogen content on the 

crystallization kinetics, surface morphology, and 

grain growth," Journal of Applied Physics 2006, 

99, (2), 023507/1-023507/9. 

van Hest, M.F.A.M.; Dabney, M.S.; Perkins, J.D.; 

Ginley, D.S.; Taylor, M.P., "Titanium-doped indium 

oxide: A high-mobility transparent conductor," 

Applied Physics Letters 2005, 87, (3), 032111/1­

032111/3. 

van Hest, M.F.A.M.; Dabney, M.S.; Perkins, J.D.; 

Ginley, D.S., "High-mobility molybdenum doped 

indium oxide," Thin Solid Films 2005, 496, (1), 

70–74. 

Olson, D.C.; Piris, J.; Collins, R.T.; Shaheen, S.E.; 

Ginley, D.S., "Hybrid photovoltaic devices of 

polymer and ZnO nanofiber composites." Thin 

Solid Films 2005, 496, (1), 26-29. 

Mitchell, W.J.; Kopidakis, N.; Rance, W.L.; 

Rumbles, G.; Ginley, D.S.; Shaheen, S.E., "Phenyl 

cored thiophene dendrimers: synthesis and 

application in photovoltaic devices." PMSE 

Preprints 2006, 95, 425-426. 

Kaydanova, T.; van Hest, M.F.A.M.; Miedaner, A.; 

Curtis, C. .; Alleman, J.L.; Dabney, M.S.; Garnett, 

E.; Shaheen, S.; Smith, L.; Collins, R.; Hanoka, 

J.I.; Gabor, A.M.; Ginley, D.S., "Direct write 

contacts for solar cells," Conference Record of the 

IEEE Photovoltaic Specialists Conference 2005, 

31st, 1305-1308. 

Y. Yan, R. Noufi, and M.M. Al-Jassim, “GrainBoundary Physics in Polycrystalline CuInSe2 

revisited: Experiment and Theory,” Phys. Rev. 

Lett. 96, 205501 (2006). 

M.J. Romero, C.-S. Jiang, J. Abushama, H.R. 

Moutinho, M.M. Al-Jassim, and R. Noufi, 

"Electroluminescence Mapping of CuGaSe2 Solar 

Cells by Atomic Force Microscopy," Appl. Phys. 

Lett. 89, 143120 (2006). 

Miguel A. Contreras, Manuel J. Romero, R. Noufi, 

"Characterization of Cu(In,Ga)Se2 Materials Used 

in Record Performance Solar Cells," Thin Solid 

Films 511-512 (2006) 51-54. 

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

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

R. Noufi, “Phase Control of CuxTe Flm and Its 

Effects on CdS/CdTe Solar Cell," Thin Solid Films, 

Special Edition, 2006 Spring EMRS, 2006. 

Photovoltaic R&D

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42
 

X. Wu, J. Zhou, A. Duda, J.C. Keane, T.A. 

Gessert, Y Yan, and R. Noufi, “13.9%-Efficient 

CdTe Polycrystaline Thin-Film Solar Cells with an 

Infrared Transmission of ~50%,” Prog. in 

Photovoltaics: Research and Applications, 14 pp. 

471-483 (2006). 

Rommel Noufi and Ken Zweibel, "High-Efficiency 

CdTe And CIGS Thin-Film Solar Cells: Highlights 

and Challenges," Proceedings of the 4th World 

Conference on Photovoltaic Energy Conversion 

(Hawaii, 2006). 

Xiaonan Li, S.E. Asher, S. Limpijumnong , S.B. 

Zhang, S.-H. Wei, T.M. Barnes, T.J. Coutts, and 

R. Noufi, "Unintentional Doping and Compensation 

Effects of Carbon in Metal-organic Chemical-vapor 

Deposition Fabricated ZnO Thin Films,” J. Vac. 

Sci. Technol. A24, 1213-17 (2006). 

J. Geisz, J. Olson, M. Romero, C. Jiang, and 

A. Norman “Lattice-mismatched GaAsP Solar 

Cells Grown on Silicon by OMVPE,” Proceedings 

of the 4th World Conference on Photovoltaic 

Energy Conversion (Hawaii, 2006). 

D. Jackrel, A. Ptak, S. Bank, H. Yuen, M. Wistey, 

D. Friedman, S. Kurtz, and J. Harris “GaInNAsSb 

Solar Cells Grown by Molecular Beam Epitaxy,” 

Proceedings of the 4th World Conference on 

Photovoltaic Energy Conversion (Hawaii, 2006). 

M. Luther, S.W. Johnston, S.R. Kurtz, R.K. 

Ahrenkiel, and R.T. Collins “Temperaturedependent dark current measurements in GaAsN 

heterojunction diodes,” Appl. Phys. Lett. 88, 

263502 (2006). 

A.J. Ptak, D.J. Friedman, Sarah Kurtz, and R.C. 

Reedy, “Low-acceptor-concentration GaInNAs 

grown by molecular-beam epitaxy for high-current 

p-i-n solar cell applications,” J. Appl. Phys. 98, 

094501 (2005). 

M. Wanlass, P. Ahrenkiel, D. Albin, J. Carapella, 

A. Duda, K. Emery, D. Friedman, J. Geisz, 

K. Jones, A. Kibbler, J. Kiehl, S. Kurtz, 

W. McMahon, T. Moriarty, J. Olson, A. Ptak, 

M. Romero, and S. Ward “Monolithic, Ultra-Thin 

GaInP/GaAs/GaInAs Tandem Solar Cells,” 

Proceedings of the 4th World Conference on 

Photovoltaic Energy Conversion (Hawaii, 2006). 

43

Photovoltaic R&D

Fundamental Research
 

 

 

 

 

____________________________________________________________________________________ 

 

 

 

 

___________________________________________________________________________________ 

 

High-Performance Photovoltaics 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Martha Symko-Davies, 303-384-6528, martha_symko_davies@nrel.gov 

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

FY 2006 Budget: $5,143K 

Objectives 

The High-Performance Photovoltaics (HiPerf PV) Project aims to explore the ultimate performance limits 

of PV technologies, approximately doubling their sunlight-to-electricity conversion efficiencies during its 

course. This work includes developing: 

•	 Thin-film tandem cells and modules toward 25% and 20% efficiencies. 

•	 Precommercial multijunction concentrator modules able to convert more than one-third of the 

sun’s energy to electricity. 

•	 High-risk/high-payoff third-generation PV technologies, primarily high-efficiency and excitonbased solar cells, aimed at substantially surpassing the performance of existing solar cell 

technologies. 

•	 Scientific and technical research opportunities for minority undergraduate and graduate students 

in solar energy technologies via the Minority University Research Associates Project. 

Accomplishments 

•	 The Institute of Energy Conversion (IEC) demonstrated an 11.9% CIGSS (1.5eV) top cell material 

of the polycrystalline thin-film tandem. 

•	 Boeing Spectrolab demonstrated a 40.7%-efficient GaInP/GaInAs/Ge cell that was verified by 

NREL at 236 suns. 

•	 Researchers investigated the design of shallower acceptors in ZnO and proposed new concepts 

to overcome p-type doping difficulty in wide-gap semiconductors such as ZnO, which is an 

important transparent conducting oxide (TCO) for solar cells. By manipulating the wavefunction 

character of the defect states, they can design defect complexes that can significantly lower the 

acceptor transition energy levels, thus providing a new opportunity to make p-type ZnO. 

•	 The University of Delaware has provided a model for defect formation during the growth of the IIInitrides during both molecular beam epitaxy (MBE) and metal organic chemical vapor deposition 

(MOCVD), allowing further improvements in material and solar cells. 

Future Directions 

The project will merge into University and Exploratory Research to address key R&D issues in support of 

the goals of the Solar America Initiative. These include: 

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

•	 Designing approaches for fabricating solar cells with >50% efficiency, in quantity, in 5 years. 

1. Introduction wide range of complex issues and provides initial 

modeling and baseline experiments of several 

The HiPerf PV Project aims to explore the ultimate advanced concepts. 

performance of PV technologies, approximately 

doubling their sunlight-to-electricity conversion Categories within the HiPerf PV Project are: (1) 

efficiencies during its course. The project is subcontracted research in polycrystalline thin-film 

expected to enable progress of high-efficiency tandems; (2) subcontracted research in III-V 

technologies toward commercial prototype multijunction concentrators; (3) subcontracted 

products. This begins with the investigations of a Future Generation research; (4) high-efficiency 
 

 

 

 

 

 

 

 

novel concepts conducted by NREL’s in-house 

Energy Sciences Division, and (5) the Minority 

University Research Associates (MURA) task. 

Near-term milestones for the R&D tasks under the 

project follow and are listed in the DOE Solar 

Program Multi-Year Technical Plan (MYTP). 

Throughout the project’s term, there will be 

opportunities to reach established program goals 

by both disruptive technology advances and/or 

multiple incremental improvements. 

This development of R&D will lead the pathway 

toward new record cell efficiencies and 

commercial prototype products. For concentrating 

photovoltaics (CPV), gaining a position in the 

marketplace could portend the emergence of CPV 

systems in the next 2–5 years at installed system 

costs of $3 per watt. 

2. Technical Approach 

The project consists of three phases for the 

polycrystalline thin-film tandems and III-V 

multijunction concentrators, which focus on a 

specific approach to solving the challenges 

associated with high efficiencies. The first phase is 

critical as it provides a means to accelerate toward 

the most promising paths for implementation, 

followed by commercial prototype products. 

The HiPerf PV Project funds in-house and 

university teams developing high-risk innovative 

concepts (such as organic solar cells and novel 

solar conversion processes) with the potential for 

ultra-high efficiency (>50%) and very low cost. 

These tasks are well leveraged by related science 

supported by DOE’s Office of Science, Basic 

Energy Sciences. 

The MURA task provides scientific and technical 

research opportunities for minority undergraduate 

students to work on various solar energy 

technology projects. 

Task Title FY 2006 

Budget ($K) 

High-Performance PV 

Management 1,123 

Thin-Film Polycrystalline Tandems 790 

III-V Multijunction Concentrators 870 

Future Generation Project 508 

MURA 335 

High-Efficiency Concepts 1,520 

3. Results and Accomplishments 

All results reflect an MYTP milestone and will be 

discussed after the milestone is stated. 

3.1 High-Performance PV Management 

•	 Assessed research on exploring pathways to 

high-efficiency PV MYTP: Task 1 of Section 

4.1.2 

The subcontracts under the Polycrystalline ThinFilm Tandems and the III-V Multijunction 

Concentrators are ending for the most part in 

FY2007. The Future Generation and MURA 

subcontracts are targeted to end in FY 2008. 

3.2 Thin-Film Polycrystalline Tandems 

Oregon State has identified several new materials 

of interest as window and absorber materials for 

PV applications, and progress has been made in 

developing processes for thin-film deposition. With 

bandgaps >2 eV, the materials Cu3TaQ4 (Q = S, 

Se) are two inexpensive candidates as p-type 

window materials. A pulsed laser deposition (PLD) 

process has been developed for deposition of the 

sulfide, and initial characterization of electrical and 

optical properties has been completed. Progress 

in deposition of films of the potential absorber 

materials Fe2MS4 (M = Si, Ge) has also been 

made via electron-beam deposition and annealing 

in sulfur atmospheres. Notably, control of carrier 

concentration has been demonstrated by doping 

of the M site, providing additional impetus to 

develop this sulfide system. Wide-bandgap 

BuCuTeF films have continued to be of interest as 

transparent back contacts for CIGS and CdTe 

cells, and incorporation of BCTF films in CIGS 

structures has been investigated. 

Improved efficiency has been demonstrated by 

IEC for the Cu(InGa)(SeS)2 absorber layer. This 

process uses a bilayer evaporation process, which 

results in through-film S and Se compositional 

gradients. The resulting devices have higher fill 

factors, up to 78%, than previous Cu(InGa)(SeS)2 

cells. This is attributed to improved current 

collection. The best cell had VOC = 0.77V, JSC = 

20.6 mA/cm2

, FF = 75.2%, and efficiency = 11.9%. 

The complete cell structure for each is: 

glass/Mo/Cu(InGa)(SeS)2/ZnO/ITO/Ni-Al grid / 

MgF2. This Cu(InGa)(SeS)2 absorber layer had 

average composition over the top ~1 μm, as 

measured by energy dispersive x-ray 

spectroscopy, of 23.9% Cu, 11.8 % In, 13.9% Ga, 

28.5% Se, and 22.2% S. This composition 

indicates a bandgap energy (Eg) of 1.61 eV. 

However, because of the compositional gradient in 
 

 

 

 

 

 

 

 

 

 

 

 

 

the film, the bandgap is not uniform through the 

film thickness. Therefore, a more relevant 

measure of Eg is obtained from the long 

wavelength edge of the quantum efficiency (QE) 

by comparison with a CuInS2 device, which has a 

known bandgap of 1.53 eV and a steep edge in 

the QE. In this case, the Cu(InGa)(SeS)2 cell has 

the same bandgap of 1.53 eV. 

3.3 III-V Multijunction Concentrators 

•	 Demonstrated a 40.7%-efficient III-V 

multijunction cell under concentration. MYTP: 

Task 1 of Section 4.1.2 

Boeing Spectrolab achieved a new world record 

efficiency of 40.7% for a three-junction terrestrial 

concentrator cell. This is the highest NRELconfirmed efficiency ever measured for any PV 

device. A large experimental matrix of threejunction GaInP/GaInAs/Ge terrestrial concentrator 

cells was carried out, using metamorphic and 

lattice-matched configurations, optimization of 

current ratio, and a variety of high-efficiency 

semiconductor device structures, cell sizes, grid 

patterns, and fabrication processes. A 

metamorphic Ga0.44In0.56P/Ga0.92In0.08As/Ge 

three-junction solar cell from these experiments 

reached a record 40.7% efficiency at 240 suns. 

This metamorphic device is the first solar cell to 

reach over 40% in efficiency, and has the highest 

solar conversion efficiency for any type of 

photovoltaic cell developed to date. Spectrolab 

also demonstrated first-prototype four-junction 

cells with initial efficiencies at >35%. 

Amonix developed an improved optical system 

specifically fitted for the existing Amonix Fresnel 

lens that was designed to provide a concentrated 

sunlight distribution pattern for the back-contact 

silicon solar cell. The optical paths of the new 

system were designed for better tracking 

tolerance, which yields more energy production 

per installed kilowatt. Amonix has designed and 

fabricated a single-plate multijunction module 

(>28% efficiency), which is being field-tested. 

Since this field-tested module installation, another 

module has been built and tested at the factory 

using the improved optics and the latest 

Spectrolab cells. Initial readings have shown an 

efficiency of nearly 30% at equilibrium 

temperature. 

The University of Delaware efforts are directed 

toward the InGaN material system. This offers the 

potential for increased solar cell efficiencies, most 

immediately through the realization of highbandgap solar cells (>2.4 eV), which are required 

for ultra-high efficiency tandems. This 2.4 V opencircuit voltage was in fact achieved using 

In0.05Ga0.95N with a bandgap of 3.3 eV. The 

increased voltage was achieved by improving the 

phase separation in the InGaN MOCVD-grown 

material. Although phase separation increases at 

high In compositions, methods to suppress this 

phenomenon have been identified by controlling 

the growth process. Further, models for defect 

formation during the growth of the III-nitrides 

during both MBE and MOCVD have been 

developed, allowing further improvements in 

material and solar cells. 

The California Institute of Technology is focused 

on a “Four Junction Solar Cell with 40% Target 

Efficiency by Wafer Bonding and Layer Transfer.” 

Integration of dissimilar materials to form 

multijunction solar cells requires a method to 

accommodate the large lattice mismatch between 

the constituent layers, and this method should 

maintain high crystalline quality in the active layers 

and enable an ohmic electrical contact at the 

interface. Direct wafer bonding of III-V compound 

semiconductors lattice-matched to InP and GaAs 

can enable formation of highly lattice-mismatched 

interfaces with high electronic quality. They 

demonstrated the first multijunction solar cell with 

an interface formed by direct wafer bonding. The 

cell is a two-junction GaAs/InGaAs/InP cell with a 

direct covalently bonded interface between the 

GaAs subcell and InGaAs/InP subcell. The opencircuit voltage of the direct bonded two-junction 

cell is equal to the sum of the open-circuit voltages 

of the constituent, indicating a bonded two-junction 

cell with high electronic quality. 

3.4 Future Generation 

The provisions of the MYTP (Sect. 4.1.1) 

specifically call for fundamental R&D involving our 

colleges and universities and, as a corollary, the 

development of the next generation of solar 

technologists. The following accomplishments 

support this activity. 

The University of Delaware developed a new 

model that includes internal optical absorption and 

recombination within a finite intermediate band (as 

opposed to the infinitesimally narrow band 

typically assumed). In addition to showing that 

such transitions are required to realize physically 

consistent efficiency results, the results 

demonstrate that the efficiency is a slowly varying 

function of the intermediate band width. The ability 

to implement a solar cell with multiple bands 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

depends critically on realizing a material that has a 

band structure as close to ideal as possible, but 

also one in which the absorption coefficients 

match those from detailed balance calculations. 

To model the absorption coefficients, the group 

developed a model of the density of states for a 

quantum dot solar cell, using a piecewise 

continuous parabolic density of states while 

assuming that all transitions are direct. 

Calculations showed that by introducing 

asymmetry into the oscillator strengths, absorption 

coefficients can be designed that show very little 

overlap, and together they cover the range of high 

solar irradiance so as to lead to solar cells with 

high efficiencies. 

Northwestern University attacked two major 

bottlenecks in TCO electrode growth for 

photovoltaic cells: (1) enhancing the 

mobility/conductivity of TCO films grown on 

amorphous glass substrates and (2) optimizing 

TCO surface properties for maximum electrode 

performance. It was shown that: 

•	 MOCVD-derived MgO template layers, which 

grow spontaneously with high degrees of 

texture on glass, can be used to template 

MOCVD CdO films with higher crystallinity and 

mobility than is normally possible on simple 

glass substrates. 

•	 Highly conductive In-doped CdO electrode 

films grown by MOCVD can be enhanced in 

work function and corrosion resistance by 

coating with thin layers of ion-beam-assisted 

deposition (IBAD)-derived ITO films. Films 

with one-third the sheet resistance of 

commercial ITO are produced that contain 

only 15% of the In of commercial ITO films 

3.5 Novel High-Efficiency Concepts 

The High-Efficiency Concepts effort was 

recompeted to target emerging state-of-the-art, 

high-efficiency concepts. This group listed in the 

following table is from NREL's Energy Sciences 

Division and works directly with NCPV scientists. 

Researchers have developed a comprehensive 

theoretical understanding of these basic materials 

properties in the TCOs In2O3 and ZnO, and 

predict their variation with process parameters 

during crystal growth. The theoretical tools 

developed are prerequisite for the design of new 

PV materials. 

Researchers determined that photoelectrons in 

TiO2 recombine with oxidized redox species in the 

electrolyte via surface states rather than from the 

conduction band, etc. (Zhu, et al., J. Phys Chem. 

B., in press). In addition, researchers discovered 

that the charge-collection efficiency and lightharvesting efficiency are markedly enhanced in 

sensitized oriented nanotube arrays. 

Researchers have investigated the influence of a 

number of chemical treatments on the optical 

properties of PbSe and PbS quantum dot (QD) 

films and on the behavior of PV devices made with 

QD arrays. In addition, they have begun 

fabricating and characterizing PV devices in which 

a thin absorber layer of PbS QDs is deposited on 

a planar conducting oxide surface. The device 

operates in similar fashion to a Gratzel-type cell 

where photoexcited electrons in the QDs are 

injected into the oxide, and the QDs are 

subsequently reduced by an ionic species in an 

electrolyte after charge injection. The advantages 

of this device configuration versus a device with a 

QD-sensitized porous oxide are the ability to better 

control the interface between the QDs and oxide 

surface, a simpler fabrication process, and a 

geometry that is easier to model. Ideally, we would 

like to make devices with just a monolayer of QDs 

toallow the most efficient charge transfer. 

Researchers investigated the design of shallower 

acceptors in ZnO. They proposed new concepts to 

overcome p-type doping difficulty in wide-gap 

semiconductors such as ZnO, which is an 

important TCO for solar cells. They show that by 

manipulating the wavefunction character of the 

defect states, they can designed defect complexes 

that can significantly lower the acceptor transition 

energy levels, thus pr oviding a new opportunity to 

make p-type ZnO. 

Researchers investigated light-induced 

recombination centers in p-type CZ Si. They 

identified the microscopic mechanism for the 

generation of non-radiative recombination centers 

in boron-doped, oxygen-rich p-type CZ silicon. 

Boron forms a complex with O2 dimer, and under 

illumination, the complex reconfigures between 

bistable configurations, causing non-radiative 

recombinat ion, thereby reducing solar cell 

efficiency. 

Researchers studied monolithic ultra-thin latticemismatched solar cells with optimal bandgaps: 

The underlying concepts are part of an invention 

(NREL IR #05-17 by Wanlass/Mascarenhas). This 

effort enhances the possibility of designing very 

high efficiency monolithic multi-bandgap tandem 
 

 

 

 

 

 

 

 

 

solar cells. Tandem designs involving latticemismatched materials typically suffer from epilayer 

bowing problems. Conventional cell designs are 

based on non-optimal bandgaps. They researched 

approaches directed at helping circumvent these 

limitations. 

Investigat or

Principal Title/Research A ctivity
 

Arthur Frank Dye Cell Research
 

Arthur Nozik Quantum Dots 

Angelo

Mascarenhas Solid State Spectroscopy
 

Su-Huai Wei Computational Materials 

Science 

Alex Zunger Solid State Theory
 

NREL High -Efficie ncy Concepts Group 

3.6 The MURA Program 

This includes eight minority-serving universities 

(six Historically Black Colleges and Universities 

and two Hispanic-serving universities). 

Accomplishments in 2006 include development of 

a software tool, Tonatiuh, for the design and 

analysis of solar concentrating systems. Tonatiuh 

is well under way to being released in 2007. When 

finished, Tonatiuh will become a very valuable tool 

for assisting solar researchers in the design and 

analysis of solar concentrating systems (University 

of Texas at Brownsville). At Fisk University, 

semiconductor QDs have been fabricated using 

both pulsed electron-beam deposition (PED) and 

PLD techniques via direct ablation of devicequality target materials. ZnO nanowires have been 

grown routinely via a vapor-liquid-solid process at 

Fisk. Their sizes, density, and growth direction 

with respect to the substrate can be controlled 

through the growth conditions. And, direct 

deposition of QDs on ZnO nanowires by PED has 

been achieved. A comparison of the photoinduced current response of cells consisting of 

ZnO nanowires sensitized by QDs synthesized 

using wet chemistry methods and from direct 

deposition showed enhanced charge transport. 

The Renewable Energy Academic Partnership 

(REAP) Review Meeting was held August 7, 2006, 

in conjunction with the 16th Crystalline Silicon 

Workshop in Denver, CO. Presentations 

generated interesting discussions, which 

demonstrated great enthusiasm by participants 

toward the individual projects. The DOE NREL 

MURA Program continues to re ceive worldwide 

re cognition for its unique efforts. 

4. Planned FY 2007 Activities 

The planned activities directly support the MYTP 

under Task 1, sections 4.1.1.5 and 4.1.2.5. 

The subcontracted R&D in this area will be ending 

during FY 2007 and into FY 2008. The HiPerf PV 

Project will merge into the University and 

Exploratory Research Program. 

•	 Finalize subcontracts under "Exploring and 

Accelerating Pathways towards High 

Performance PV: Phase I-B" through 

FYs 2006/2007. 

•	 Demonstrate a 41%-efficient III-V multijunction 

cell under concentration. 

•	 Continue modeling of the enhanced 

performance of quantum-dot-based solar cells 

to see how far one can push the multipleexciton-generation effect in various PV cell 

configurations to maximize cell efficiency. 

•	 Target 10% efficiency for organic solar cells. 

•	 Continue R&D of ultra-high efficiency solar 

cells targeting >50% efficiency. 

•	 MURA: Ensure progress on projects currently 

under way and invite additional universities to 

participate in the REAP Conference through 

partnerships with other similar programs. 

5. Major FY 2006 Publications 

M. Symko-Davies and R. McConnell, “Progress in 

High Performance PV: Future Generation PV," 

Proceedings of the 4th World Conference on 

Photovoltaic Energy Conversion (Hawaii, 2006). 

R. McConnell and M. Symko-Davies, 

“Multijunction PV for High Performance 

Concentrators, Proceedings of the 4th World 

Conference on Photovoltaic Energy Conversion 

(Hawaii, 2006). 

M. Symko-Davies, R. McConnell, K. Tanabe, A.F. 

Morral, H.A. Atwater, "Direct-bonded 

GaAs/InGaAs tandem solar cell," Appl. Phys. Lett. 

89, 102106 (2006). 

M.J. Griggs, D.C. Law, R.R. King, A.C. Ackerman, 

J.M. Zahler, H.A. Atwater, "Design Approaches 

and Materials Processes for Ultrahigh Efficiency 

Lattice Multi-junction Solar Cells," Proceedings of 

4th World Conference on Photovoltaic Energy 

Conversion (Hawaii, 2006). 

O. Jani, C. Honsberg, Y. Huang, J.O. Song, I. 

Ferguson, G. Namkoong, E. Trybus, A. Doolittle, 

S. Kurtz, “Design, Growth, Fabrication and 

Characterization of High-Band Gap InGaN/GaN 
 

 

 

 

Solar Cells,” Proceedings of 4th World Conference 

on Photovoltaic Energy Conversion (Hawaii, 2006) 

B. Fluegel, S. Francoeur, and A. Mascarenhas, 

"Spin-Orbit Bowing in GaAs1-xBix," Phys. Rev. 

Lett. 97, 067205 (2006). 

J. Li, S.-H. Wei, S.-S. Li, Jian-Bai Xia, "Design of 

shallow acceptors in ZnO: First-principles bandstructure calculations,” Phys. Rev. B 74, (Rapid 

Communication), 081201(R) (2006). 

Y. Yan, M. M. Al-Jassim, and S.-H. Wei, Doping of 

ZnO by group-Ib elements,” Appl. Phys. Lett. 89, 

181912 (2006). 

T. J. Coutts, X. Li, T. M. Barnes, B. M. Keyes, C. 

L. Perkins, S. E. Asher, S. B. Zhang, S.-H. Wei, 

and S. Limpijumnong, "Synthesis and 

characterization of nitrogen-doped ZnO films 

grown by MOCVD,” (Book Chapter) in ZnO Bulk, 

Thin-Films, and Nanostructures--Processing, 

Properties and Applications, edited by C. Jagadish 

and S.J. Pearton, (Elsevier Science, New York, 

2006), p. 43. 

M.-H. Du, H. M. Branz, R. S. Crandall, and S.B. 

Zhang, Phys. Rev. Lett. 97, 256602 (2006). 

S. Lany and A. Zunger, "Dopability, intrinsic 

conductivity, and non-stoichiometry of transparent 

conducting oxides," Phys. Rev. Lett. (In Press). 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity FY 2006 

($K) 

Georgia Institute of 

Technology 

Ajeet Rohatgi 

Atlanta, GA 

Ajeet.Rohatgi@ece.gatec.edu 

Thin-Film Si Bottom Cells for Tandem 

Device Structures 60 

University of Delaware 

Bill Shafarman 

Newark, DE 

wns@udel.edu 

High-Performance PV Polycrystalline ThinFilm Tandem Cells 209 

University of Toledo 

Alvin Compaan 

Toledo, OH 

adc@physics.utoledo.edu 

Sputtered II-VI Alloys and Structures 

for Tandem PV 217 

University of Oregon 

David Cohen 

Eugene, OR 

dcohen@darkwing.uoregon.com 

Identifying the Electronic Properties 

Relevant to Improving the Performance of 

High Band-Gap Copper-Based I-III-VI2 

Chalcopyrite Thin Film PV Devices 

139 

Oregon State University 

Douglas Keszler 

Corvallis, OR 

Douglas.keszler@orst.edu 

Novel Materials Development for 

Polycrystalline Thin-Film Solar Cells 165 

Spectrolab, Inc. 

Raed Sherif 

Sylmar, CA 

rsherif@spectrolab.com 

Ultra-High-Efficiency Multijunction Cell and 

Receiver Module 223 

Amonix, Inc. 

Vahan Garbushian 

Torrence, CA 

drvahan@earthlink.net 

Design and Demonstration of a Greater 

than 33% Efficiency High-Concentration 

Module Using 40% III-V Multijunction 

Devices 

232 

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 

174 

JX Crystals 

Lew Fraas 

Issaquah, WA 

lfraas@jxcrystals.com 

Toward 40% Efficient Mechanically 

Stacked III-V Terrestrial Concentrator 

Cells 

33 
Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity FY 2006 

($K) 

University of Delaware 

Christiana Honsberg 

Newark, DE 

honsberg@ece.gatech.edu 

Novel High Efficiency PV Devices Based 

on the III-N Material System 145 

Ohio State University 

Steve Ringel 

Colombus, OH 

ringel@ee.eng.ohiostate.edu 

Optimized III-V Multijunction Concentrator 

Solar Cells on Patterned Si and Ge 

Substrates 

35 

Underwriters Lab/ 

Arizona State University 

Liang Ji 

Phoenix, AZ 

Liang.ji@us.ul.com 

Development of IEC Design Qualification 

Standard for Concentrator PV Modules 15 

Princeton University 

Steve Forrest 

Princeton, NJ 

forrest@ee.princeton.edu 

Approaching 10% Efficient Cells Using 

Tandem Organic PV Cell with Enhanced 

Optical Coating 

80 

University of ColoradoBoulder 

Josef Michl 

Boulder, CO 

michlj@colorado.edu Ultra-High Efficiency Excitonic Solar Cells 148 

Northwestern University 

Tom Mason 

Evanston, IL 

tmason@northwestern.edu 

Interface and Electrodes for NextGeneration Organic Solar Cells 115 

University of Delaware 

Christiana Honsberg 

Newark, DE 

honsberg@ee.udel.edu 

Theoretical and Experimental Investigation 

of Approaches to >50%-Efficient Solar 

Cells 

165 

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 38 

University of Texas, El 

Paso 

Gregory Lush 

El Paso, TX 

glush@gerdau.com 

Investigation, fabrication, characterization, 

and modeling of solar cells 42 

Fisk University 

Richard Mu 

Nashville, TN 

rmu@fisk.edu 

Development of Si quantum dots for 

advanced solar cells with maximum 

efficiency 

47 

Howard University 

J.M. Momoh 

Washington, DC 

jmomoh@msn.com 

Developing automation/strategies to 

improve power management and 

distribution of renewable energy resources 

42 

N. Carolina Central 

University 

Joe Dutta 

Durham, NC 

jmd@nccu.edu 

Fabricating and characterizing bulk and 

non-phase PV materials for student 

research 

42 

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. 

35 

N. Carolina A&T State 

University 

G. Shahbazzi 

Greensville, NC 

ash@ncat.edu 

Modeling performance of a grid-connected 

PV system in a residential area 34 

Central State University 

Clark Fuller 

Wilberforce, OH 

cfuller@prodigy.net 

Renewable energy technology and 

technology transfer in developing countries 

51 

4* 

* Funded with prior year (FY 2005) funds. 
 

 

 

 

 

 

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 2006 include the following. 

Thin Film PV Partnership 

•	 Two Technology Partners expanded manufacturing facilities in the United States (First Solar 

85 MWp and Uni-Solar 60 MWp). 

•	 Production of thin films in the United States grew from 12 MWp in 2003 to an estimated >70 

MWp in 2006. 

PV Module Reliability R&D 

•	 Upgraded and maintained accelerated module testing capabilities essential to industry 

partners and progressed toward becoming an accredited Certified Testing Body Testing 

Laboratory. 

•	 Reported results of high-voltage stress testing (module leakage currents using the High 

Voltage StressTestbed) for potential high-voltage applications by industry. 

Inverter and BOS Development 

•	 Completed Phase II of the High-Reliability Inverter Initiative (HRII) with hardware beta 

deliverables by GE and Xantrex. 

•	 Assessed HRII beta inverter and controller prototypes for conformity to utility interconnection 

requirements, performance objectives, and manufacturing objectives. 

PV Manufacturing R&D 

•	 Completed the development (achieve manufacturing-line-ready status) of at least three in-line 

diagnostic processes initiated in FY 2002 awards from "In-Line Diagnostic, Intelligent 

Processing (IDIP) Solicitation" with at least five of the U.S. PV industry partnerships involved 

in the IDIP solicitation having reported a minimum of 22 in-line diagnostic processes that 

have been implemented on U.S. PV production lines. 

•	 Conducted a stage-gate evaluation of project participants to assess and determine the needs 

for additional manufacturing R&D and select areas for elimination or support. 

51

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

Thin Film PV Partnership 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

 DOE Golden Field Office (DOE/GO) 

Key Technical Contact: Harin S. Ullal, 303-384-6486, harin_ullal@nrel.gov 

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

FY 2006 Budget: $7,500K (NREL) 

Objectives 

•	 Support the Solar America Initiative Technology Partnership Pathway Funding Opportunity 

Announcement to achieve levelized electricity cost 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 on which these advanced PV technologies can be successful in 

improving manufacturing and continue to progress in terms of performance, reliability, and 

reduced cost for products meant to compete in the PV marketplace. 

•	 Sustain innovation to support progress toward ambitious long-term PV cost and performance 

goals (e.g., 15% modules at under $50/m2

 and capable of lasting 30 years) appropriate for costcompetitive PV electricity. 

Accomplishments 

•	 Met two important OMB/DOE/EERE/SETP Joule milestones. 

•	 Two Technology Partners expanded manufacturing facilities in the United States (First Solar 

85 MWp and Uni-Solar 60 MWp). 

•	 Production of thin films in the United States grew from 12 MWp in 2003 to an estimated >70 MWp 

in 2006. 

Future Directions 

•	 Continue to address key issues supporting the transition to successful first-time manufacturing or 

major production expansion in each thin film. 

•	 Significantly reduce CIS and CdTe layer thicknesses in cells and support transfer of this to future 

manufacturing technologies. 

•	 Direct thin-film CdTe solar cell research toward higher open-circuit voltage. 

•	 Investigate nanocrystalline bottom cells for thin-film silicon multijunction solar cells. 

1. Introduction 

Thin-film PV technologies are regarded as having 

good potential to meet ambitious cost and 

performance goals consistent with the Solar 

America Initiative Technology Partnership 

Pathway to achieve long-term goals for levelized 

cost of energy by 2015. The Thin Film PV 

Partnership Program is designed to accelerate 

progress toward those goals. It includes 

subcontracted R&D in CIS, CdTe, amorphous 

silicon, and new thin films such as film silicon. 

The Partnership works closely with NREL’s inhouse research, facilitating collaborative activities 

through the Partnership’s National Research 

Teams. Three National R&D Teams work in 

material-specific areas—a-Si/thin-film c-Si, CdTe, 

and CIGS)—and there are crosscutting teams in 

Thin Film Module Reliability and environmental 

health and safety (EH&S), the latter with 

Brookhaven National Laboratory. The National 

Teams are made up of leading researchers from 

academia, U.S. industry, and NREL and other 

national laboratories (e.g., Pacific Northwest 

National Laboratory) who work together to define 

and carry out shared activities and common goals. 

2. Technical Approach 

The Partnership had 22 subcontracts during 

FY 2006 (see Section 6). Eight subcontracts 

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52
ended in 2005. The subcontract areas were 

broken down as shown in Table 1. 

Table 1. Thin Film PV Partnership Funding 

Task Title FY 2006 

Budget ($K) 

Project Management and Team 

Coordination 971 

Thin Film Center of Excellence 971 

Amorphous and Thin Film Silicon 972 

CIS Devices 1090 

CdTe Devices 1090 

Module Testing and Analysis 1040 

Three groups were major Technology Partner 

subcontracts: Global Solar in CIS; First Solar in 

CdTe; and United Solar Ovonic (Uni-Solar) in a-Si. 

Shell Solar terminated their CIS research and 

technology development and have redirected their 

activities elsewhere. The rest were R&D Partners, 

which were either small businesses making 

progress toward pilot production or universities 

supporting the 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 the fiscal year. 

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 

of technologies that have been successfully 

developed by DOE funding to the private sector. 

This evolution has been more than two decades in 

the making and is not yet accomplished. However, 

with the substantial growth in CY 2006 to more 

than 70 MW (from only 12 MW in the United 

States in 2003), thin films are in this important 

transition. Based on surveys of the Partnership’s 

Technology Partners, it is expected that this may 

again double in CY 2007 to about 140 MW of 

annual U.S. production. If so, this will indicate the 

arrival of these key, potentially lower-cost 

technology options—and even the resumption of 

U.S. leadership in the PV marketplace (because 

thin films may take a leading role, going forward). 

Table 2 summarizes the worldwide production 

capacity of thin-film PV modules. It is estimated 

that by the year 2010, worldwide thin-film PV 

production capacity will be over 1700 MW, with 

U.S. production capacity estimated at ~1 GW, for 

about 56% of the world market share. 

Table 2. Estimated Worldwide Production Capacity of Thin Film PV Modules by 2010 

53

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The following summarizes highlights from 

FY 2006. 

3.1 First Solar 85-MWp Factory Expansion 

First Solar completed an aggressive expansion in 

2006 with an installed manufacturing capacity of 

85 MW and expected sales of about 50 MW in 

2006. Also, worldwide production capacity of First 

Solar is expected to be 185 MW with projected 

sales of over 100 MW in 2007, making it one of 

the top ten PV companies in the world, and the 

number one thin-film PV company in the world. 

Fig. 1. First Solar’s 1400-kW thin-film CdTe solar 

field deployed in Germany. 

Substantial progress has been made in terms of: 

(1) the new 85-MWp coater, which is now 

fabricating the majority of products; (2) reducing 

maintenance costs by substantially enhancing 

materials utilization rates; and (3) automating and 

improving most aspects of production. First Solar 

plans to move to a cost structure that would allow 

the installation of $3/Wp ground-mounted PV 

systems in the not-too-distant future. First Solar 

also has expansion plans in Asia. An 

announcement is expected sometime in CY 2007. 

First Solar’s initial public offering (IPO) raised 

more than $400 million in 2006, the largest 

amount ever for a thin-film PV company. 

The DOE Solar Program and NREL, the National 

Center for Photovoltaics (NCPV), and the Thin 

Film PV Partnership have supported the research 

and development of this very promising thin 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. The 

deposition process won a prestigious R&D 100 

Award in 2003, which 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 David Garman, Under Secretary, 

U.S. Department of Energy. 

3.2 Uni-Solar 60-MWp Factory Expansion 

The Uni-Solar a-Si factory is working at full 

capacity of about 2 MWp/month. Due to the silicon 

shortage, module prices have been rising, and 

profitability is increasing. Recently, Uni-Solar built 

a second 30-MWp plant in Michigan, bringing its 

total manufacturing capacity to 60 MW. In 

describing the competitiveness of Uni-Solar 

technology, company President Subhendu Guha 

made the case that their peel-and-stick roofing 

material is directly competitive with all other 

rooftop PV approaches (including c-Si and CdTe) 

because of the ease of installation (e.g., reduced 

balance of system costs) and superior aesthetics 

and durability (see Fig. 3). He mentioned two 

major “wins” over such competition for large 

commercial rooftop projects, one for 1 MW on the 

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. 

Of interest, First Solar and Uni-Solar have 

different, but complementary, focus markets: UniSolar on commercial roofs and First Solar for 

large, ground-mounted systems. In both markets, 

they are quite competitive compared to crystalline 

silicon technology. 

3.3 Global Solar to Expand Capacity to 60 MW by 

2008 

Global Solar has announced expansion plans of 

60 MW of thin-film CIGS modules in 2008. All the 

necessary equipment for the manufacture of the 

thin-film CIGS modules have been ordered and 

are expected to be delivered by late 2007. Some 

of the new encapsulation/packaging of the CIGS 

modules have shown exceptional stability, 

especially in the damp-heat tests. Tests are also 

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54
 

being conducted at the Tucson Electric Power in 

Springerville, AZ. 

Global Solar Energy (GSE) fabricated a 10.2%­

efficient, 88.9-W thin-film CIGS power module, the 

highest-wattage CIGS module in the world. ITN 

Energy Systems (ITN/ES), Littleton, CO, 

developed the intelligent processing system for 

improved processing conditions and yields for cell 

and module fabrication that helped produce this 

module. The module parameters are as follows: Isc 

= 4.07 Amp, Voc = 36 V, FF = 0.606, area = 8709 

cm2

. Stainless steel (ss) web lengths of 1000 feet 

were used for the roll-to-roll processing of the 

devices. The typical cell structure is 

ITO/CdS/CIGS/Mo/ss. 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 the 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 National Research Teams 

There are three active national research teams— 

one each in a-Si, CIGS, and CdTe. Each team 

holds an annual meeting. The team members 

consist of scientists, engineers, managers, 

professors, and students representing academia, 

the Air Force, the thin-film PV industry, and the 

national laboratories (NREL and Pacific Northwest 

National Laboratory [PNNL]). At these meetings, 

industry representatives report on the progress 

and future plans of their respective groups. For 

example, in 2006, Uni-Solar presented data on its 

30-MW plant in Auburn, MI, with plans to expand 

to 60 MW in 2006 and 180 MW in 2008. First Solar 

presented its expansion plans to 85 MW in 2006 

and another 100-MW plant in Germany in 2007, 

for a cumulative worldwide production capacity of 

185 MW by 2007. Global Solar presented plans to 

expand its production capacity to 60 MW in 

Tucson, AZ, in 2008. 

The commercial success of Uni-Solar is a driving 

force behind the a-Si Team's activities. An open 

question is whether Uni-Solar will switch its 

manufacturing operations from triple-junction 

amorphous silicon to a-Si:H/nc-Si:H multijunctions. 

Uni-Solar, which also conducts extensive in-house 

research on nc-Si Solar cells, currently believes 

that nc-Si remains an attractive option for future 

manufacturing if cell performance can be further 

improved. But company personnel consider the 

performance of a-Si/nc-Si multijunctions to be only 

equivalent, not superior, to a-Si:H/a-SiGe:H 

multijunctions. Providing fundamental researchers 

with such feedback from industry is very important. 

Many researchers in Japan and Europe assume 

a priori that the performance of nc-Si:H cells is 

superior to a-SiGe:H cells. There is also renewed 

interest in producing a-Si:H single or multijunctions 

(or a-Si:H/nc-Si:H) on glass superstrates, but 

current resources within the team are somewhat 

limited for effectively supporting such activities 

(e.g., at EPV or at Applied Materials). 

The CIGS Team focuses on developing thin 

absorber layers of about 1.0 micron, or even 

thinner to about 0.5 micron, for future module 

fabrication. Thus far, NREL scientists have 

fabricated total-area efficiency of 17.1% for a thinfilm CIGS solar cell using an absorber thickness of 

about 1.0 micron. Modeling should provide some 

answers, especially lower Jsc for the thin absorber 

cells. Additional presentations were made by Air 

Force Research Laboratory personnel on their 

thin-film PV activities, namely, a-Si and CIGS; and 

NREL, with 19.5% CIGS solar cells using CdZnS 

buffer layers, device physics of CIGS solar cells, 

and nanodomains of CIGS absorbers. IEC 

presented an overview of its thin absorber 

research that has been performed by researchers 

worldwide. 

In the area of CdTe, the Device Physics Subteam 

described measurements and analysis that 

elucidated device physics specific to thin-film 

polycrystalline CdTe PV devices. The Stability 

Subteam identified several modes of changed 

device performance that have been observed to 

varying degrees in a wide variety of CdTe PV 

devices subjected to conditions of elevated 

temperature, electrical bias, illumination, or 

environmental stress—conditions that are 

intended to accelerate the type of degradation that 

could occur in the field. The Materials Chemistry 

Subteam addressed issues relating to the impact 

of Cu, O2, Cl, and other impurities on CdTe PV 

device performance; another focus is on 

developing thin CdTe absorber layers of about 

1.0 micron for fabrication of solar cells. Total-area, 

solar cell efficiency of 14% has been achieved for 

thin-film CdTe devices by researchers at the 

University of Toledo. 

3.5 University Technical Highlights 

The University Center of Excellence (Institute of 

Energy Conversion, IEC, University of Delaware) 

continues to provide both valuable insights and 

services to the fabrication of thin-film solar cells. 

55

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Recently, IEC implemented vapor-transport 

deposition of CdTe solar cells and has fabricated 

and analyzed 450 of the solar cells fabricated. A 

significant effort of this work has been to 

characterize the role of impurities (in the CdTe 

absorber and during “contacting”) on cell 

performance. 

Regarding CuInGaSe2 (CIGS) solar cells, IEC, at 

the urging of NREL, has put significant effort into 

working on the reaction kinetics of selenization 

and sulfurization reactions. This now includes 

CuInS2 solar cells and compares their 

characteristics to similar-bandgap CuInGaSe2 

cells. While historically IEC has also developed 

much know-how and understanding related to coevaporated CIGS solar cells, it had been 

expressed by the community that there was not 

enough fundamental support for those companies 

practicing CIGS formation by selenization 

(sulfurization) of metallic precursors. One key 

aspect of the scheme of producing CIGS by this 

method is to shorten the selenization 

(sulfurization) reaction times. Understanding the 

reaction kinetics is critical toward accomplishing a 

processing time reduction. 

In the area of Si film solar cells, IEC recently used 

its deposition capabilities to produce heterojunction 

“HIT” solar cells. A cell with a new heterojunction 

wrap-through emitter design was fabricated and 

delivered to NREL, where it was measured as 

11.8% efficient. IEC had previously worked on Alinduced recrystallized Si film layers as the 

absorber layer for solar cells. While carried out 

with much talent at IEC, this work (not unlike 

similar work performed by other institutions 

outside the United States) has not yet resulted in 

cells with a competitive performance advantage 

over existing cells. 

IEC maintains the capability to produce state-ofthe art, or near state-of-the-art, solar cells in all 

thin-film PV technologies using a variety of 

deposition approaches, which continues to enable 

start-up companies to complete solar cells with the 

companies' own materials. 

Solar cell making continued at the University of 

Toledo (a-Si [Deng and Collins] and CdTe 

[Compaan, Karpov, and Collins]); FSEC (CIGSS 

cells [Dhere]); and in-house at NREL and IEC. 

Device making by university groups requires a 

significant long-term investment for enabling such 

cell fabrication, but also confers four major 

benefits: (1) commercial spin-off opportunities are 

created (e.g., Midwest Optoelectronics from 

Toledo); (2) improved understanding of solar cell 

physics can be obtained, because the university 

cell makers will usually reveal more detail than 

industrial groups about their cell fabrication; (3) 

specialized cells for specialized measurements 

can be fabricated that resemble regular cells; (4) 

options for changes in processing can be explored 

before industry has to invest in expensive 

modifications of pilot or production equipment. 

Beneficiaries of this were the University of Nevada 

(Heske, chemical composition and energybandgap measurements of solar cells), Syracuse 

University (Schiff, time-of-flight measurements, 

project ended 9/30/06), the University of Oregon 

(Cohen, defect spectroscopes), and PNNL (Olsen, 

encapsulation research). Each of these groups at 

times required special cell structures to carry out 

their specialized experiments. Aside from NREL 

in-house work, the work at PNNL is the only effort 

dealing with cell/module packaging and 

encapsulation issues. This is an important area, as 

many current industrial start-ups make 

preparations for producing a flexible CIGS product 

on foil substrates. Low-cost, flexible transparent 

packaging schemes for CIS have to provide better 

protection than for a-Si (nc-Si) cells, as CIGS cells 

are apparently more moisture sensitive. The 

University of Utah (Taylor, now at Colorado School 

of Mines) provides valuable insights into lightinduced degradation mechanisms (i.e., StaeblerWronski effect) in a-Si:H alloys and nc-Si:H. At the 

University of South Florida, Tampa, FL, 

researchers are investigating the doping of the 

CdTe absoprber film with P. They are also 

studying the effect of a new TiO2 buffer layer and 

a TiSe2 back contact by sputtering. Colorado State 

University (CSU) is expanding its activities to 

make 1-sq. ft. prototype CdTe submodules using 

its in-line system based on the close-spaced 

sublimation process. CSU has already made 

12%–13%-efficient thin-film CdTe solar cells. 

These cells are also being investigated for their 

stability under light and bias conditions. Device 

analysis on both CdTe and CIGS solar cells is 

performed at CSU and the feedback is given to the 

NREL university and industry groups. Colorado 

School of Mines has done studies of basic 

electronic properties of CdTe-based solar cells, 

such as deep electronic states using admittance 

spectroscopy techniques. 

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56
 

 

 

3.6 Completion of Two Critical OMB/DOE/EERE 

Joule Milestones 

Two OMB/DOE/EERE/SETP Joule milestones 

were completed within the Partnership. One is 

related to achieving a higher efficiency thin-film 

module of 11.2% by the end of the fiscal year. This 

milestone was achieved by Shell Solar Industries 

(a Technology Partner) for selenized CIGS thinfilm modules. The other Joule milestone 

concerned the testing the various thin-film 

modules made by U.S. industry for reliability. The 

modules are being tested at the Florida Solar 

Energy Center and Texas A&M University. 

3.7 Flow of Venture Capital to Thin-Film Industry 

Accelerates in FY 2006 

We note the acceleration of private and venture 

capital funding to thin-film start-ups, most of which 

were spun off or supported by NREL in-house and 

Thin Film Partnership research and National R&D 

Teams. We also note the budget pressures 

resulting from this evolution. 

The success of PV in the marketplace has 

generated a wave of private funding interest for 

start-ups of all kinds in PV, and in particular for 

those involved with CIGS. Announcements of 

major investments have come from: Wurth Solar 

(55M euro), Miasole ($32M), Nanosolar ($75M), 

Ascent Solar ($16M – IPO), and Heliovolt ($8M). 

Wurth Solar is a German company that bases its 

technology on multisource evaporation, harkening 

back to the original CIGS work at Boeing and 

within NREL (all DOE supported). Wurth had 

about 1–2 MWp of CIGS production capacity and 

makes the most efficient thin-film products in the 

world (about 11% total area efficiency). They have 

now increased their manufacturing capacity to 

15 MW per year, perhaps the largest CIGS 

production capacity in the world to date. 

The other three are U.S. start-ups that are 

precommercial; in fact, they are pre-prototype 

module development. Their ideas are based on 

reducing the capital cost and raising the 

throughput of CIGS versus existing approaches. 

Together with NREL support, they are making 

decent, but not outstanding, cells (8%–12%). 

NREL support has been mostly from consultation 

or Cooperative Research and Development 

Agreements with in-house CIGS experts and the 

NREL Measurements and Characterization Group; 

and work with the NREL National Research CIS 

Team. We have started a new subcontract with 

one (Nanosolar) to do work in high-throughput 

selenization of flexible-based CIGS films, a known 

bottleneck in selenization approaches. Overall 

budget shortfalls in the Thin Film Partnership are 

preventing us from seeking out additional 

subcontracts with promising new start-ups, such 

as Miasole, Ascent Solar, Solo Power, Solyandra 

and Heliovolt, and another start-up, Daystar ($9M 

from a public offering in 2004). Thus we are 

seeking other forms of collaboration and support. 

To illustrate the relationships involved: Daystar’s 

founder, John Tuttle, is an ex-NREL CIS scientist; 

Heliovolt's founder Billy Stanbery, was funded by 

the Partnership at Boeing and later at the 

University of Florida; Nanosolar's Vice President of 

Engineering Chris Eberspacher was funded by the 

Partnership at Unisun and ARCO Solar; and 

Miasole received direct NREL in-house support via 

Rommel Noufi and his CIGS team. Bulent Basol, 

cofounder of Solo Power, was supported while at 

ISET to develop low-cost, thin-film CIGS solar 

cells. Joe Armstrong, chief technical officer of 

Ascent Solar, was funded at Martin Marietta and 

ITN Energy Systems, while Prem Nath, currently 

senior vice president of manufacturing at Ascent 

Solar, was funded at Uni-Solar for product 

development and module reliability. Ken Zweibel, 

former manager of the Thin Film Partnership, is 

now chairman and president of yet another startup, Primestar Solar, which is working on thin-film 

CdTe PV technology. 

The advent of substantial private funding for CIGS 

and CdTe PV start-ups is a major change in the 

development path of thin films. Prior to this, venture 

money was almost nonexistent, which prevented 

this channel of development. The change is very 

favorable for thin-film PV in general, and CIGS in 

particular, and allows us to leverage the exceptional 

in-house NREL CIGS and CdTe expertise and 

characterization capabilities as a major method of 

supporting outside activities (complementing 

support via the Partnership subcontracts). 

However, we also foresee the possibility of some 

new difficulties. Start-ups are notoriously hurried to 

develop technology, which leaves them vulnerable 

to pitfalls (e.g., in manufacturing and reliability). 

None of these start-ups have the resources to test 

their new products in any depth. Thus we foresee 

a period when we may need to support them with 

our own testing capabilities, if only to avoid 

potential black eyes from first-time manufacturing 

and field failures. We also foresee the potential for 

these companies to seek local political support, 

which may in turn lead to undesirable pressure to 

create new earmarks. This is unfortunate collateral 

damage from our own budget shortfalls. 

57

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3.8 Thin Film Partnership Management 

The Partnership had several management 

accomplishments of note during the fiscal year, as 

discussed below. 

Web Site. We continue to update the Partnership 

Web site to make it much more accessible. We 

are now: 

•	 Including descriptive text with each entry. 

•	 Making the whole site searchable by keywords 

and authors, which is a very powerful tool. 

•	 Adding a “most recent” list of the last ten items 

posted for those who want to see what's new. 

•	 Adding a “Features” link to the home page, for 

newsworthy items such as the recent capacity 

announcements. 

With the new excitement in thin-film PV, we expect 

the site to be used more frequently. It now 

averages more than a thousand hits per day 

(www.nrel.gov/ncpv/thin_film). 

PV Materials FAQ. We added a FAQ to the NREL 

site that examines the question, posed as “The 

Terawatt Challenge” by Hoffert and Lewis: Are 

materials a constraint preventing PV from meeting 

climate change problems? The answer is that PV 

can meet climate change problems, with the 

example examined being 75 TWp by mid-century. 

Of commodity materials, glass would be the 

largest growth, but is not materials limited. Of the 

specialty semiconductor and contact materials, 

silver (for grids), indium, and tellurium are 

constrained and selenium is marginally 

constrained. However, the FAQ outlines a strategy 

for making thinner cells, recycling waste and endof-life modules, and refining more byproduct from 

existing ores to allow the CIS and CdTe 

technologies to make the needed amounts. The 

silicon-based technologies are unconstrained and 

could also meet the TW challenge. These findings 

are part of the effort to refine our understanding of 

future PV issues in relation to big picture issues 

such as climate change. 

Energy Payback FAQ Revision. We completed a 

revision of the Energy Payback FAQ for the NREL 

Web site. The changes involved: 

•	 Adding a well-documented payback period for 

the balance of systems at Tucson Electric) as 

an example of how ground-mounted systems 

have about the same energy payback as roofmounted ones. 

•	 Offering further evidence that including the 

wafer payback cost does not radically hurt c-Si 

payback. 

•	 Adding some verbiage to help people 

understand how energy input is properly paid 

back in the form of PV electricity. 

The FAQs are at (www.nrel.gov/ncpv/faq.html). 

Tracking Annual 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 versions are 

posted on our Web site and can be found via the 

search page. Table 5 summarizes the thin-film PV 

companies in the United States. There are 12 aSi/thin Si companies, 6 CdTe companies, and 12 

CIGS companies shown in the table. Another four 

U.S. CIGS PV companies are to be announced in 

2007. Worldwide, the estimate for CIGS PV 

companies is about 33. 

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58
Table 3. Best Large-Area, Thin Film Modules 

(standard conditions, aperture area) 

Company Device Size 

(cm2

) 

Efficiency Power/Watts 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 10.2% 67 2/04 

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 reported by company, but not independently measured (to our knowledge) 

Table 4. Commercial Thin Film Modules, Data Taken from Web sites 

(total-area efficiencies) 

Rated Module 

Efficiency (%) Description 

Rated 

Output 

(Wp) 

Estimated Price 

($/Wp) 

Temperature 

coefficient* 

11.0 Würth Solar WS31050/80 (CIS) 80 Above $3 -0.36 %/oC 

9.4 First Solar FS65 (CdTe) 67.5 Below $3 -0.25 %/oC 

6.9 Antec-Solar ATF50 (CdTe) 50 Below $3 -0.18%/oC 

6.3 Kaneka GEA/GSA 

(single-junction a-Si) 60 Below $3 -0.2%/oC 

6.4 Mitsubishi Heavy MA100 (singlejunction a-Si, VHF deposition) 100 Below $3 -0.2 %/oC 

6.3 Uni-Solar US-64 (triple-junction 

amorphous silicon) 64 $3.10–$3.40 -0.21%/oC 

5.3 RWE Schott ASI-F32/12 

(same bandgap a-Si tandem) 32.2 Varies -0.2%/oC 

Compiled by Bolko von Roedern; 9/2006
 

*Temperature coefficients will vary slightly depending on local spectral content. 

Disclaimer: Listing could be outdated or incomplete (missing manufacturers and/or some "best" product); 

prices are estimates for large quantities. 

59

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Table 5. Thin Film PV Companies – USA 

a-Si CdTe CIS 

Uni-Solar – MI First Solar – OH Global Solar – AZ 

Applied Materials – CA Primestar Solar – CO Miasole – CA 

Power Films – IA AVA Tech – CO Energy PV – NJ 

Energy PV – NJ Solar Fields – OH Ascent Solar – CO 

V Systems – CO Canrom – NY ISET – CA 

XsunX – CO Ascentool – CA ITN/ES – CO 

Gen3 Solar – CA Daystar – NY 

Innovalight – CA Nanosolar – CA 

Nano PV – NJ Heliovolt – TX 

Solexant – CA Solo Power – CA 

Proto Flex – CO Solyndra – CA 

New Solar Ventures – NM RESI – NJ 

4. Planned FY 2007 Activities 

In FY 2007, the Thin Film PV Partnership will 

continue to address key issues supporting the 

successful first-time manufacturing or explosive 

manufacturing growth of each thin film. These 

will be especially critical in FY 2007, which is 

expected to be a key year in thin-film growth, 

with U.S. production rising from about 12 MW in 

CY 2003 to over 70 MW in CY 2006, and 

perhaps doubling again in CY 2007 to about 140 

MW. Any setbacks in manufacturing yield or 

outdoor reliability could lead to multi-year 

setbacks or even technology abandonment in 

extreme cases. 

5. Major FY 2006 Publications 

We have published several subcontract reports 

and also have posted them on the Partnership 

Web site. 

B. von Roedern, H.S. Ullal, and K. Zweibel, 

“Polycrystalline thin Film Photovotaic: From the 

Laboratory to Solar Fields," Proceedings of the 

4th World Conference on Photovoltaic Energy 

Conversion (Hawaii, 2006). 

B. von Roedern, “Thin Film PV Module Review," 

Refocus Magazine, July/August 2006, p 34. 

H.S. Ullal; “Thin Film Solar Electric 

Technologies”, Solar Power 2006, San Jose, 

CA; October 2006. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2006 

($K) 

Cost 

Share 

($K) 

Colorado State University 

Jim Sites 

Ft. Collins, CO 

sites@lamar.colostate.edu 

Characterization & analysis of 

CIS and CdTe devices 170 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 

309 0 

Energy Photovoltaics 

Alan Delahoy 

Lawrenceville, NJ 

a.delahoy@epv.net 

Advanced CIGS photovoltaic 

technology 320 96 

First Solar, LLC 

Peter Meyers 

Perrysburg, OH 

pmeyers@firstsolar.com 

Expanding the Limits of CdTe PV 

Performance 143 7.5 

First Solar, LLC 

Roger Green 

Perrysburg, OH 

rgreen@firstsolar.com 

Research leading to highthroughput processing of thin-film 

CdTe PV technology 

655 655 

Florida Solar Energy 

Center 

Neelkanth Dhere 

Cocoa, FL 

dhere@fsec.ucf.edu 

CIGSS solar cells by selenization 

and sulfurization 166 10 

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60
 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2006 

($K) 

Cost 

Share 

($K) 

Florida Solar Energy 

Center 

Neelkanth Dhere 

Cocoa, FL 

dhere@fsec.ucf.edu 

Module reliability testing in hot 

and humid climate 111 0 

Global Solar Energy Tucson, AZ 

swiedman@globalsolar.com 

Cost and reliability improvements 

for CIGS based on flexible 

substrates 

440 440 

International Solar Electric 

Technologies 

Vijay Kapur 

Inglewood, CA 

vkkapur@isetinc.com 

Lab to large-scale transition for 

non-vacuum thin-film CIGS solar 

cells 

180 18 

NanoSolar 

Chris Eberspacher 

Palo Alto, CA 

chris@nanosolar.com 

High-productivity annealing for 

thin-film CIS PV 91 4.5 

Pacific Northwest National 

Laboratory 

Larry Olsen 

Richland, WA 

Larry.Olsen@pnl.gov 

Barrier coatings for thin-film cell 

protection 120 0 

Shell Solar Industries 

Dale Tarrant 

Camarillo, CA 

Dale.tarrant@shellsolar.com 

Process R&D for CIS-based thinfilm PV 555 555 

Syracuse University 

Eric Schiff 

Syracuse, NY 

easchiff@syr.edu 

Transport, interfaces, and 

modeling in a-Si:H-based solar 

cells 

0 0 

Texas A&M University 

Mike Davis 

College Station, TX 

mdavis@esl.tamu.edu 

Outdoor monitoring and highvoltage bias testing of thin-film 

PV modules in hot and humid 

climate 

45 0 

U. of Delaware, Institute of 

Energy Conversion 

Robert Birkmire 

Newark, DE 

rwb@strauss.udel.edu Thin Film Center of Excellence 1190 0 

United Solar Ovonic 

Subhendu Guha 

Auburn Hills, MI 

sguha@uni-solar.com 

High-efficiency amorphous and 

nanocrystalline-based solar cells 

and modules 

510 510 

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 

100 0 

University of Oregon 

Dave Cohen 

Eugene, OR 

dcohen@oregon.uoregon.edu 

Innovative characterization of 

amorphous and thin-film silicon 

for improved module 

performance 

119 0 

University of South Florida 

Chris Ferekides 

Tampa, FL 

ferekide@eng.usf.edu 

High-efficiency CdTe cells by 

CSS 120 8 

University of Toledo 

Al Compaan 

Toledo, OH 

ADC@physics.utoledo.edu 

Fabrication & physics of CdTe 

devices by sputtering 303 91 

University of Toledo 

Xunming Deng 

Toledo, OH 

dengx@physics.utoledo.edu 

Fabrication and characterization 

of advanced triple-junction 

amorphous-silicon-based solar 

cells 

332 96 

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 

121 0 

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____________________________________________________________________________________ 

 

 

 

____________________________________________________________________________________ 

PV Module Reliability R&D 

Performing Organizations: National Renewable Energy Laboratory (NREL)

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Carol Riordan (NREL Primary Contact), 303-384-6780, 

carol_riordan@nrel.gov 

Carl Osterwald (Exploratory Reliability & Performance R&D), 303-384­

6764, carl_osterwald@nrel.gov 

Tom McMahon (Module Packaging Research and Reliability), 303-384­

6762, tom_mcmahon@nrel.gov 

David King (SNL Primary Contact, Module Reliability Characterization), 

505-844-8220, dlking@sandia.gov 

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

FY 2006 Budgets:	 $2,869K (NREL), $0 (SNL) 

Objectives 

The key FY 2006 objectives of this Module Reliability R&D Project were 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 modules. 

•	 Use selected indoor and outdoor accelerated exposure testing to discover and/or replicate 

observed outdoor failures and performance degradation. 

•	 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. 

Accomplishments 

•	 Upgraded and maintained accelerated module testing capabilities essential to industry partners 

and progressed toward becoming an accredited Certified Testing Body Testing Laboratory. 

•	 Reported results of high-voltage stress testing (module leakage currents using the High Voltage 

StressTestbed) for potential high-voltage applications by industry. 

•	 Reported on adhesive and cohesive strength of the layers within thin-film module structures of the 

principal technologies. 

•	 Collaborated with numerous industry partners to develop new encapsulants, provide adhesion 

and water vapor transmission values, water ingress modeling, and infrared imaging for cracked 

cells and shunt problems; filed record of invention. 

Future Directions 

•	 The current version (pre-appropriations) of the FY 2007 Annual Operating Plan specifies 

continuing R&D to characterize indoor and outdoor performance and reliability of precommercial 

and commercial PV modules with the objective of identifying, analyzing, understanding and 

ameliorating module degradation and failure mechanisms for a range of technologies and 

operating conditions (temperature, humidity, irradiance) in the quest for long (e.g., 30-year) PV 

system lifetimes and low (e.g., 0.5%–1%/year) degradation rates that allow the PV industry to 

reach DOE cost goals for solar electricity. 

•	 Assuming the launch of the Solar America Initiative, these module performance and reliability 

R&D agreements will play a major part in the test and evaluation of deliverables from the 

Technology Pathway Partnerships, including application and development of test and evaluation 

protocols for module performance and energy modeling. 

Photovoltaic R&D

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62
 

 

 

 

 

 

 

1. Introduction 

One of the top research priorities identified by the 

PV industry year after year is module performance 

and reliability, as an essential ingredient for 

product credibility and consumer confidence. In 

addition, the relatively recent application of the 

Systems-Driven Approach used to identify 

Technical Improvement Opportunities (using the 

Solar Advisor Model) for program planning 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 kWhr of electricity over the system’s 30-year 

lifetime to meet the DOE cost goals. PV modules 

are the most important system component when 

cost, performance, and reliability are considered. 

The modules make up 55% to 65% of the total 

system price/costs and directly determine the 

overall system conversion efficiency. Thus, this 

project addressing module reliability, packaging, 

performance and characterization R&D—a joint 

effort of NREL and SNL—continues to be an 

essential element of the DOE Photovoltaics 

Subprogram. 

2. Technical Approach 

The technical approach in this project consists of 

short- and long-term outdoor module performance 

testing and characterization, selected outdoor 

stress testing (e.g., high-voltage environments), 

accelerated indoor environmental (e.g., temperature, humidity) stress testing, performance 

analyses/characterization/modeling, failure/ degradation analyses, and module packaging R&D 

(e.g., moisture ingress analysis and amelioration) 

to help mitigate failures/degradation and/or reduce 

module costs and improve performance. To 

conduct such 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 2006, the work was accomplished under 

these agreements: 

Agreement Title FY 2006 

Budget ($K) 

Exploratory Reliability & 

Performance R&D (NREL) 1,456 

Module Packaging Research & 

Reliability (NREL) 

1,413 

Module Reliability Characterization 

(SNL) 0* 

*Initial FY 2006 spend plan and agreement planning 

were for a $500K budget at SNL; however budget 

reduction resulted in the SNL module reliability effort 

being minimized and consolidated with complementary 

activities in the System Test & Evaluation Project. 

Capabilities were maintained in anticipation of an 

expanded effort in FY 2007 in support of the Solar 

America Initiative. 

3. Results and Accomplishments 

Results and accomplishments for the major 

activities are as follows. 

Exploratory Reliability and Performance R&D 

(Osterwald/NREL) 

•	 Upgraded and maintained accelerated module 

testing capabilities (e.g., environmental 

chamber upgrades, new hail gun) essential to 

industry partners, and made progress toward 

becoming an accredited Certified Testing 

Body Testing Laboratory (quality system 

development) in a Cooperative Research and 

Development Agreement (CRADA) with 

Underwriters Laboratories (9/306). 

•	 Reported analysis of outdoor module 

performance for module technologies under 

test in the Performance and Energy Ratings 

Testbed (PERT) showing effective efficiency 

and energy production compared to 

nameplate. (Oral presentation/paper 4th World 

Conference on Photovoltaic Energy 

Conversion 5/06); PERT system upgrades 

initiated.) 

•	 Reported results of high-voltage stress testing 

(module leakage currents using the High 

Voltage Stress Testbed) for potential highvoltage applications by industry (Oral 

Presentation/paper at 4th World Conference 

on Photovoltaic Energy Conversion (5/06); 

tests continue (9/06). 

•	 Reported comparisons of module degradation 

/failure for 2.5x irradiance exposure versus 1x 

exposure using the Outdoor Accelerated Test 

System to assess accelerated exposure 

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capability (initial report 3/06); tests suspended 

due to resources for equipment repair (9/30). 

•	 Continued support of the Thin-Film 

Partnership thin-film modules hot & humid 

outdoor exposure testing experiment (and 

other subcontracted module research) 

(comprehensive review and analysis of all 

data submitted by Florida Solar Energy Center 

completed, 9/30/06; Texas A&M has not been 

submitting data as required under their 

subcontract; ongoing). 

Feedback from the DOE Solar Program Peer 

Review of this area of R&D included statements 

such as: “[This R&D is] 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." The DOE-conducted peer review 

scored this R&D across the board as 4.0 on a 

4.0-point scale. 

Module Packaging Research & Reliability R&D 

(McMahon/NREL) 

•	 Reported on adhesive and cohesive strength 

of the layers within thin-film module structures 

of the principal technologies; many thin-film 

structures measured. (Oral presentation/paper 

4th at World Conference on Photovoltaic 

Energy Conversion 5/06; published in Solar 

Energy Materials and Solar Cells (2006). 

•	 With NREL Measurements and 

Characterization staff, researched and 

reported on properties of barrier coatings; 

reported on micro- and macro-conformality 

9/06). Completed report on efficacy of 

plasma-enhanced chemical vapor deposition 

oxide/nitride/carbide thin-film moisture barriers 

deposited on mirrors, PET (polyethylene 

terephthalate), and thin-film cells (12/05); 

analysis led to future experimental design. 

•	 Laminated and performed accelerated testing 

of CdTe-based cells and CIGS mini-modules 

using a variety of encapsulants/processing 

cycles to determine factors affecting device 

performance; reported R&D results to internal 

and external thin-film collaborators (e.g,. Thinfilm Partnership National Team meetings) 

(9/06). 

•	 Collaborated with numerous industry partners 

to develop new encapsulants, provide 

adhesion and water vapor transmission 

values, water ingress modeling, and infrared 

imaging for cracked cells and shunt problems; 

record of invention filed; specific industry 

collaboration being formalized in CRADA; Oral 

presentation/paper at the DOE Solar 

Technologies Program Review, 11/05. 

•	 Co-chaired DOE’s Accelerated Testing 

Workshop (2/06), giving one of the nine 

presentations; assisting with final report being 

prepared by DOE (9/06); very strong industry 

interest in continued R&D and future 

workshops. 

In the DOE Solar Program Peer Review, the 

Module Packaging Research and Reliability R&D 

received an average score of 3.8 on a 4.0-point 

scale with comments such as, “The relevance of 

the research is thought to be excellent and critical 

to meeting DOE goals and objectives as well as 

reducing the cost of these systems. The approach 

is seen as excellent and uses a well thought out 

plan that is highly focused on an area of the 

technology that is key to the future success of the 

U.S. PV Program.” 

4. Planned FY 2007 Activities 

FY 2007 planned activities are given in the draft 

(pre-appropriations) FY 2007 Annual Operating 

Plan, which is organized differently from previous 

years. 

Module Reliability and Performance R&D will be 

performed under the Technology Evaluation 

Activity, PV System Testing and Evaluation 

Project, with Agreements on “Module and Array 

Testing” and “Module Failure Analysis” 

emphasizing accelerated stress testing, module 

performance testing and analysis, manufacturer 

support, performance and energy modeling, 

development of field protocols, array reliability, 

and application of testing and analytic capabilities 

to diagnose module failure mechanisms. This 

same agreement also includes related tasks on 

inverter, balance of systems, and systems testing 

and evaluation. 

Module Packaging and Reliability R&D will be 

performed under the Applied Research Activity, 

Electronic Materials and Devices Project, in the 

“Cell and Module Stability and Reliability” 

agreement. Proposed work under this agreement 

includes providing measures of water vapor 

transmission, adhesion, and mechanical 

properties for new and existing packaging 

materials for a range of temperatures and 

Photovoltaic R&D

Advanced Materials and Devices

64
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

humidity, before and after stress; modeling 

moisture ingress for various module structures; 

R&D on thin-film moisture barriers; assembly of 

failure diagnostic information on modules from 

different test sites and identification of dominant 

failure mechanisms; and R&D on intrinsic device 

stability for fabrication processes, such as reduced 

film thickness. 

5. FY 2006 Special Recognitions, Awards, and 

Patents 

Record of invention filed: EPDM-Based Advanced 

Packaging Materials for Photovoltaic Modules. 

6. Major FY 2006 Publications 

C.R. Osterwald, J. Adelstein, J.A. del Cueto, 

B. Kroposki, D. Trudell, and T. Moriarty, 

“Comparison of Degradation Rates of Individual 

Modules Held at Maximum Power,” Proceedings 

of the 4th World Conference on Photovoltaic 

Energy Conversion (Hawaii, 2006), pp. 2085–2088. 

J.A. Del Cueto and B.R. Sekulic, “An Unlikely 

Combination of Experiments with a Novel HighVoltage CIGS Photovoltaic Array,” Proceedings of 

the 4th World Conference on Photovoltaic Energy 

Conversion (Hawaii, 2006), pp. 2054-2057. 

C.R. Osterwald, J. Adelstein, J.A. del Cueto, 

W. Sekulic, D. Trudell, P. McNutt, R. Hansen, 

S. Rummel, A. Anderberg and T. Moriarty, 

“Resistive Loading of Photovoltaic Modules and 

Arrays for Long-Term Exposure Testing,” Prog. 

Photovolt: Res. Appl. 2006, 14:567–575. 

G.J. Jorgensen, J. Del Cueto, S. Glick, M.D. 

Kempe, J. Pankow, F.J. Pern, K.M. Terwilliger, 

T.J. McMahon, “Moisture Transport, Adhesion, 

and Corrosion Protection of PV Module Packaging 

Materials,” Solar Energy Materials & Solar Cells, 

90 (2006), 2739–2775. 

T. McMahon and G. Jorgensen, “Adhesion And 

Thin-Film Module Reliability,” Proceedings of 4th 

World Conference on Photovoltaic Energy 

Conversion (Hawaii, 2006). 

M.Kempe et al., "EVA Potential Problems for 

Photovoltaic Packaging,” Proceedings of the 4th 

World Conference on Photovoltaic Energy 

Conversion (Hawaii, 2006). 

M. Kempe, “Modeling of rates of moisture ingress 

into photovoltaic modules,” Sol. Energy Mat. and 

Sol. Cells, 90 (2006) 2720. 

F.J. Pern and G.J. Jorgensen, “Development of 

Damp-heat Resistant Self-primed EVA and NonEVA Encapsulant Formulations at NREL,” Solar 

Energy Technologies Program Review, Denver, 

CO, Nov. 2005. 

7. University and Industry Partners 

There were no subcontracts in this project in 

FY 2006. Both NREL and SNL researchers 

interact extensively with industry and university 

collaborators to test and characterize module 

performance and reliability, as well as examine 

failure and degradation mechanisms and perform 

R&D on module packaging (e.g., backsheet and 

encapsulant formulation/testing) and reliability. 

Collaborators and contacts include, but are not 

limited to companies, universities, and institutes 

such as: SunPower, GE, United Solar Ovonic, 

Shell, BP Solar, PowerLight, Miasolé, SolFocus, 

Texas A&M, FSEC, AKT, Planar Systems, 

Madico, Deerfield Urethane, DuPont, PPG, Dow 

Chemical and Dow Corning, BRP, Pilkington 

Glass, Saint Gobain, Applied Films, Fraunhofer 

Institute, InnoSense LLC, First Solar, SRS 

Building Energy, SBM Solar, and Advent Solar. 

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____________________________________________________________________________________ 

 

 

 

 

____________________________________________________________________________________ 

Inverter and BOS Development 

Performing Organization: Sandia National Laboratories (SNL) 

Key Technical Contact: Ward Bower, 505-844-5206, wibower@sandia.gov 

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

FY 2006 Budget: $380K 

Objectives 

Improve inverters and balance of systems (BOS) through the High-Reliability Inverter Initiative (HRII) for 

PV, to include: 

•	 Mean time between failure (MTBF) of >10 years 

• Inverter efficiency >94% 

•	 Inverter cost less than $0.90/watt 

•	 Meet Underwriters Laboratories (UL) 1741 certification requirements. 

•	 Meet FCC Part 15, Class B for electromagnetic emanations requirements. 

•	 Meet National Electrical Code (NEC®

) requirements. 

•	 Design for high-volume (>10,000/yr) production. 

•	 Provide modularity and expandability to function with other distributed energy resources. 

•	 Improve inverter and BOS designs that allow full-system integration while maintaining flexibility. 

•	 Influence codes, standards, and certifications through development, validation, and verification. 

•	 Establish the groundwork for high-tech R&D with 20-year MTBF inverter/system-integrated 

inverter and BOS goals. 

Accomplishments 

•	 Completed Phase II of the HRII with hardware beta deliverables by GE and Xantrex. 

•	 Continued the HRII Phase III with GE and Xantrex. 

•	 Assessed HRII beta inverter and controller prototypes for conformity to utility interconnection 

requirements, performance objectives, and manufacturing objectives. 

•	 Conducted updated verification and validation of prototypes, through laboratory evaluations, 

environmental testing, and performance measurements. 

•	 Completed development of an innovative high-reliability micro-inverter topology eliminating shortlife components. 

Future Directions 

•	 Fold the results of the work completed for the “High-tech Inverter Initiative” into the Solar America 

Initiative (SAI) Funding Opportunity Announcement (FOA) for Technology Pathway Partnerships 

(TPPs). 

•	 Conduct cooperative work with SAI TPP recipients as needed to help meet the goals of the SAI. 

•	 Conduct high-tech studies for inverters, BOS, systems strategies, and energy management to 

help assess needs for future generations of inverters, BOS and complete systems. 

•	 Conduct studies on inverter and BOS developments and formulate strategies to facilitate buildingintegrated and vertically integrated systems. 

1. Introduction surrounded by, and integrated into, total system 

controls. Given the number of functions the 

Inverters for PV systems are much more than just inverter must perform today, much improved 

the power electronics to convert the DC power reliability, higher performance, and lower costs are 

from PV arrays to load-compatible AC power. essential. Higher-quality inverters, even at 

They are actually the power conversion devices constant costs, can reduce the levelized cost of 

Photovoltaic R&D

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66
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

energy (LCOE) of installed PV systems, as 

indicated in DOE prediction models (such as the 

PV Systems Analysis Model) being developed 

within the Solar Energy Technologies Program. 

The expected outcome is consistent with the SAI 

and is critical to achieving its $.06/kWh energy 

production goal for installed PV systems. Further, 

given that today’s "value to the consumer" of 

installing a PV system is often dependent on 

rebates and incentives, and not just the value of 

the energy produced, an out-of-warranty failure of 

a multifunction inverter can often mean that the 

system will never work again (end of life). 

Inverters and their associated control circuits and 

functions are still, in many respects, in their 

infancy in terms of design, system integration, 

communications, performance, and especially 

reliability. The lifetimes of the inverter (controller 

of the system) must be improved to better match 

the lifetimes of PV modules (typically 30 years) 

and other BOS components. 

Today’s technical barriers associated with 

inverters involve matching the MTBF of PV 

modules, while maintaining low costs and high 

performance. These barriers are nearly 

unprecedented in terrestrial applications of power 

electronics because most electronic products are 

designed with relatively shorter MTBF. One 

longer-lived power electronics comparison is a 

variable-speed drive for industrial motors. The 

motor load has well-characterized impedances 

and characteristics. Higher-quality, industrialgrade components are used, and cost is not as 

important as it is for PV applications. Higher costs 

are acceptable because of the value added and 

the major loss of revenue when failures occur. 

Many electronic devices sold today are designed 

with a MTBF of just a few years. That is not 

acceptable for the inverter (controller) used in PV 

applications. Another important difference with PV 

systems is that the inverter/system is classified in 

the NEC as an “energy source.” That 

classification, along with the many unique 

characteristics of PV power systems, prompted a 

special section in the NEC for PV installations. 

Inverters with short lifetimes may be repaired or 

replaced, but both options represent costs that 

may negate most of the revenue received for 

power generation. Replacement of an inverter in a 

15-year-old system will likely also require costs 

associated with redesign of the BOS and a 

reinspection to meet existing code. It will not be 

like changing a light bulb. The High-Reliability 

Inverter Initiative took a first step toward higher 

reliability at no increase in unit cost, namely the 

improvement of MTBF to more than 10 years. 

This advance had a significant positive impact on 

calculated LCOE of PV systems. 

The objectives of the Inverter and Balance-ofSystems Project were to focus on power 

electronics and BOS hardware, to support 

engineering advancements through 

characterization feedback of newly developed 

power electronics and BOS hardware, and to 

begin establishing the suitability for incorporation 

of new inverters and BOS into completely 

integrated systems. The work was closely tied to 

objectives derived from the DOE Systems-Driven 

Approach Workshop, the DOE Workshop on a 

Systems-Driven Approach to Inverter Research 

and Development, and the DOE High-Tech 

Inverter Workshop, and will also tie to the Solar 

America Initiative Technology Pathway 

Partnership work. Each of the inverter-related 

workshops resulted in consensus prioritization that 

guided the High-Reliability Inverter Initiative and 

later the drafting of a High-Tech Inverter, Balanceof-System, and Systems R&D: A 5-Year Strategy 

that was folded into the SAI FOA for the TPPs. 

The workshop reports are still applicable to the 

future work for improving inverters and controllers. 

Many project objectives have transformed into 

direct aids to the development of certification, 

codes, and standards for PV inverters, BOS, and 

systems applications through SNL validations, 

verification, and modeling. One important related 

standard change was related to the test 

procedures needed to list a transformerless 

inverter. 

Some of the inverter- and BOS-related activities in 

this project are also applicable to other renewable 

energy technologies such as fuel cells. One 

Inverter and BOS Project goal was to strive to 

involve U.S. PV inverter manufacturers and key 

charge-controller manufacturers to examine key 

products to determine impacts on both BOS and 

PV applications. The Inverter and BOS Project 

strived to improve system reliability and efficiency, 

and improve LCOE through improved utilization of 

power electronics and storage and the 

development of selected BOS (sometimes nonpower electronics) components. The BOS Project 

further sought to develop fully integrated, 

consumer-friendly PV systems through the 

development of vertically integrated designs that 

are suitable for high-volume manufacturing. 

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2. Technical Approach 

The technical approach for this work followed a 

process by which technology development efforts 

were driven by well-defined and well-documented 

requirements based on analyses of present and 

potential markets, technology trade-off studies, 

and R&D reviews. All technical targets for R&D for 

the components and systems that are funded 

through the Solar Energy Technologies Program 

are derived from a common market perspective 

and national energy goals, and the resultant 

technologies are tested and validated in the 

context of established criteria for each market. 

Coordination with industry and potential users of 

the technology is a key to ensuring that products 

meet the market needs. 

Task Title FY 2006 

Budget ($K) 

High-Reliability Inverter 

Initiative 380 

Inverter Development and 

Manufacturing R&D 0 

3. Results and Accomplishments 

General Electric conducted in-house testing and 

Xantrex delivered Phase III prototypes of highreliability inverters to SNL's Distributed Energy 

Technologies Laboratory (DETL). Xantrex 

delivered the advanced alpha prototype to SNL in 

FY 2006 for additional evaluations. Benchmark 

evaluations and validations were completed at the 

DETL, and SNL engineers recommended further 

improvements. 

GE completed beta prototype testing, but 

abandoned the design in favor of a new lower-cost 

redesign to be funded entirely by GE. GE’s plans 

to vertically integrate its PV module manufacturing 

capabilities and the new inverter development into 

its existing new-construction housing market has 

been delayed pending development of a lowercost inverter based on many of the lessons 

learned in this project. 

Xantrex expects to use the fundamental highreliability design as a basis for its next-generation 

family of products and has extensive and critically 

timed commercialization plans for the products 

developed out of this program. Xantrex used the 

HRII inverter and charge controller in its XW 

battery-based integrated system and continues to 

improve its beta prototype prior to full production. 

Figure 1 shows the Xantrex XW Battery-based 

Integrated System. Both General Electric and 

Xantrex are currently finalizing work for Phase III 

of the High-Reliability Inverter Initiative. 

Fig. 1. The Xantrex XW Battery-based 

Integrated Power System 

Advancements shown in Fig. 2 for the microinverter development provided proof of concept for 

an innovative circuit using no electrolytic 

capacitors. The calculated MTBF was over 

250,000 hours, the performance was better than 

expected, and the distribution of heat was as 

calculated. The cost of the inverter was estimated 

at less than $.30/W in 10,000 quantities. One 

important characteristic of the innovative topology 

is the elimination of AC ripple on the PV array 

through high-speed, feed-forward control. The 

ripple was measured at about 60% rated operating 

level and was 0.3% of average DC current. The 

low ripple will improve maximum-power-point 

tracking effectiveness. The innovative topology 

appears to be applicable to higher-power inverters 

and could significantly impact future designs. 

Note: Form-factor Design Is 

Intended To Fit Within a Frame or 

Mounting Structure Of PV Module 

This Bench Prototype was 

Constructed for Initial 

Assessment of Losses, 

Performance and Thermal 

Analysis. It Uses Discrete 

Control Components 

Fig. 2. Micro-inverter thermal analysis 

prototype 

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Summary of FY 2006 Results 

Milestone or Deliverable Due 

Date Results 

Complete Phase II 

prototype evaluations to 

establish and verify inverter 

performance. 

2/1/06 Completed 

on time. 

Complete high-reliability 

commercialized inverter 

designs and verifications of 

performance and design. 

9/30/06 

Work 

continuing 

after SNL 

evaluations. 

Initiate contracts for “Hightech Inverter, BOS & 

Systems R&D Strategies.” 

9/30/06 Folded into 

SDA TPPs. 

Send RFP for high-tech 

R&D. 9/30/06 Folded into 

SAI TPPs. 

Review and select winning 

proposals to initiate hightech R&D strategies. 

9/30/06 Folded into 

SAI TPPs. 

Conduct High-tech Inverter 

to Systems Link Workshop 9/28/06 Cancelled 

Complete Final Reports on 

High-reliability prototypes, 

evaluations & verifications 

9/30/06 

Delayed to 

include final 

beta data. 

Deliver commercial quality 

high-reliability (>10 year) 

inverters to SNL. 

9/30/06 

Delays due 

to funding 

until 6/07. 

4. Planned FY 2007 Activities 

The planned “High-Tech Inverter, Balance-ofSystem, and Systems R&D” was folded in the SAI 

TPP program for FY 2007 and beyond. Proposals 

and cooperative agreements are expected to 

include R&D to develop improved inverters and 

BOS with at least a 20-year MTBF, and then fully 

integrate those components into optimized system 

designs. The resulting cooperative agreements are 

expected to optimize the performance of PV 

systems through factory-assembled and vertically 

designed and integrated systems. 

SNL’s micro-inverter development was completed 

with demonstration of a prototype that showed 

feasibility with the inverter mechanical form factor, 

cost projections, and thermal issues related to 

mounting the inverter within the frame of a PV 

module. 

5. Major FY 2006 Publications 

Bower, W., West, R., Dickerson, A., “Innovative 

PV Micro-inverter Topology Eliminates Electrolytic 

Capacitors for Longer Lifetime,” Proceedings of 

the 4th World Conference on Photovoltaic Energy 

Conversion (WCPEC), Waikoloa, HI, May 2006. 

Whitaker, C., Newmiller, J., Bower, W., “Inverter 

Performance Certification: Results from the 

Sandia Test Protocol,” 4th WCPEC, Waikoloa, HI, 

May 2006. 

Hudson, R., Edmunds, M., “Development of a 

High Reliability Inverter,” Proceedings of the DOE 

2005 Solar Program Review, Denver, CO, Nov 

2005. 

Smolenski, J., “GE High Reliability Photovoltaic 

Inverter Program,” Proceedings of the DOE 2005 

Solar Program Review, Denver, CO, Nov 2005. 

Bower, W., “Overview of Sandia’s High-reliability 

Inverter Initiative,” Proceedings of the DOE 2005 

Solar Program Review, Denver, CO, Nov 2005. 

Bower, W., West, R., Dickerson, A., “Development 

of an Innovative Micro-inverter Topology,” 

Proceedings of the DOE 2005 Solar Program 

Review, Denver, CO, Nov 2005. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/Principal 

Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2006 

($K) 

General Electric 

Joseph Smolenski 

Niskayuna, NY 

smolenski@crd.ge.com Conduct Phase III of the HRII. 210 

Xantrex Technologies 

Ray Hudson 

Livermore, CA 

Ray.Hudson@xantrex.com Conduct Phase III of the HRII. 100 

Xantrex Technologies 

Rick West 

Livermore, CA 

Rick.West@xantrex.com 

Develop/show feasibility of a novel 

micro-inverter. 12 

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____________________________________________________________________________________ 

 

 

 

 

 

PV Manufacturing R&D 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Richard Mitchell, 303-384-6479, richard_mitchell@nrel.gov 

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

FY 2006 Budget: $4,944K (NREL) 

Objectives 

•	 Improving 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 

•	 As part of the annual DOE Solar Program Review, conducted an evaluation of manufacturing 

progress in crystalline silicon technologies by U.S. industry participants in the PV Manufacturing 

R&D project. (1st Q JOULE milestone) 

•	 Completed reviews and required redirections for remaining “In-Line Diagnostics and Intelligent 

Processing in Manufacturing Scale-Up” subcontracts. 

•	 Completed reviews, required redirections, and renewals for “Large-Scale Module and Component 

Yield, Durability, and Reliability (YDR)” subcontracts. 

•	 Analyzed 2005 U.S. PV Industry Cost/Capacity data on progress to produce capacity-weighted, 

industry average results and reported on progress at the 2006 4th IEEE World Conference on 

Photovoltaic Electric Conversion. 

•	 Verified, using standard laboratory measurements, a conversion efficiency of 14.0% for a U.S.­

made commercial crystalline silicon PV module. (4th Quarter JOULE milestone) 

•	 Completed the development (achieve manufacturing-line-ready status) of at least three in-line 

diagnostic processes initiated in FY 2002 awards from "In-Line Diagnostic, Intelligent Processing 

(IDIP) Solicitation" with at least five of the U.S. PV industry partnerships involved in the IDIP 

solicitation having reported a minimum of 22 in-line diagnostic processes that have been 

implemented on U.S. PV production lines. 

•	 As part of the annual DOE Solar Program Review, conducted a stage-gate evaluation of U.S. 

industry participants in the PV Manufacturing R&D Project to assess and determine the needs for 

additional manufacturing R&D and select areas for elimination or support. 

•	 Spire – Completed design and detailed drawings of a new large-area solar simulator capable of 

handling utility-scale modules up to 1.37 m x 2.00 m. 

•	 RWE Schott Solar – Designed, demonstrated and certified a new lower-cost rafter-jack module 

mounting system for the residential retrofit PV market. 

•	 Specialized Technology Resources – Completed environmental testing of prototype modules for 

the development of improved thin-film encapsulants. 

•	 BP Solar – Completed process equipment specifications for sawing, demounting, and handling 

100-micron wafers cut on 29- micron centers. 

•	 Energy Conversion Devices – Completed testing of on-line PV capacitive diagnostic system to 

stabilize and optimize a-Si deposition. 

•	 Energy Conversion Devices – Transferred the Online Diagnostic Hardware and Display/Analysis 

Programs to the United Solar Ovonic Manufacturing Team to be used as a production tool with 

standard operating procedures. 

•	 Shell Solar – Demonstrated prototype 10%-thinner cutting wire with no yield change at wafering. 

•	 Dow Corning – Demonstrated integrated-cell package technology, including the cell, adhesive, 

and encapsulant components developed in this subcontract. 

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____________________________________________________________________________________ 

 

 

 

•	 SunPower – Completed reliability testing and evaluation of improved modules and test coupons. 

•	 Xantrex Technology – Completed low-power electronics and control design, which meets the 

25%-reduction cost goal for related inverter subassemblies. 

•	 BP Solar – Completed statistical analysis of the causes of wafer/cell breakage on production line. 

•	 Schott Solar – Completed fabrication of prototype for building-integrated PV laminate for 

commercial applications. 

•	 Shingleton Design – Demonstrated improvements to control and drive systems for one-axis 

trackers with goal of reducing installation and commissioning costs by 40% over the course of the 

subcontract 

•	 BP Solar – Established thermal model and began to analyze the dynamics of the production line 

casting process. 

•	 First Solar – Completed development of improved back-electrode design and implementation of 

improved wet spray activation process. 

•	 PowerLight – Completed initial production run with improved PowerGuard tile design as 

developed under Phase I. 

•	 Evergreen Solar – Demonstrated 15%-efficient cells in production. 

Future Directions 

•	 Complete stage-gate review of individual progress versus milestones and required redirection for 

YDR subcontracts. 

•	 Conduct end-of-year measurements to meet the FY 2007 EERE Efficiency Joule Milestone for 

U.S.-made, commercial crystalline silicon PV modules of 14.5% conversion efficiency. 

•	 Achieve the Solar Program’s JOULE Milestone on module efficiency and manufacturing cost 

•	 Analyze U.S. PV Industry Cost/Capacity data on progress to produce capacity-weighted, industry 

average results 

•	 Complete a DOE Solar Program Internal Review of the SolarWorld, BP Solar, SCHOTT Solar, 

Dow Corning, GE Energy, SunPower, Evergreen Solar, and First Solar subcontracts under the 

“Large-Scale Module and Component Yield, Durability, and Reliability” solicitation. 

•	 Evaluate the scope of subcontracted research under “Large-Scale Module and Component Yield, 

Durability, and Reliability” solicitation with identification of Technology Pathway Partnership 

awards 

•	 Complete reviews and required redirection for remaining subcontracts under the “Large-Scale 

Module and Component Yield, Durability, and Reliability” solicitation. 

1. Introduction 

The PV Manufacturing R&D (PVMR&D) Project 

assists the U.S. PV industry through a cost-shared 

manufacturing R&D partnership with the U.S. DOE 

and members of the U.S. PV industry. 

Subcontracted research focuses on U.S. industry 

improvement of processes and products, resulting 

in: (1) a substantial reduction of associated 

manufacturing costs; (2) providing 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 

directly supports the DOE Solar Program under 

“Advanced Materials and Devices.” Each 

subcontractor enhances existing manufacturing 

technologies through cost-shared development 

efforts geared toward achieving the overriding 

PVMR&D goals. Work areas include: 

improvement of module manufacturing processes 

to increase module reliability; system and systemcomponent packaging, system integration, 

manufacturing, and assembly; product 

manufacturing flexibility; and 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 on PV manufacturing technologies. The 

approach for the FY 2006 work effort was divided 

into three areas: (1) Project Management and 

Support; (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 (YDR).” 

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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; (3) 

coordination of NREL in-house activities in support 

of the PVMR&D industrial partners; and (4) 

evaluation of current trends in the PV 

manufacturing industry through collection of data 

for cost/capacity and recapture of R&D funding. 

Table 1. PVMR&D Project Tasks and Budget 

Task Title FY 2006 

Budget ($K) 

PV Manufacturing R&D Technical 

Coordination 1,670 

In-Line Diagnostics and Intelligent 

Processing 

382 

Module Yield, Durability, and 

Reliability 2,892 

2.2 In-Line Diagnostics and Intelligent Processing 

The IDIP subtask consists of the FY 2006 costshared PV manufacturing R&D subcontracts listed 

in Tables 2 and 3, awarded under the FY 2001 

IDIP competitive solicitation. This solicitation was 

directed at: improvement of module manufacturing 

processes; system and system component 

packaging, system integration, manufacturing and 

assembly; product manufacturing flexibility; and 

balance-of-system development. These 

subcontracts emphasize 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. 

Table 2. FY 2006 IDIP Subcontractors Module 

Manufacturing 

Subcontractor Title of Subcontract 

BP Solar 

Large-Scale PV Manufacturing 

Using Ultra-Thin Polycrystalline 

Silicon Solar Cells 

Energy 

Conversion 

Devices, Inc. 

Implementation of a 

Comprehensive On-Line ClosedLoop Diagnostic System for Rollto-Roll Amorphous Silicon Solar 

Cell Production 

Spire 

Corporation 

Development of Automated 

Production Line Processes for 

Solar Brightfield Modules 

Table 3. FY 2006 IDIP Subcontractors, System 

Components 

Subcontractor Title of Subcontract 

RWE Schott 

Solar, Inc. 

Plug and Play Components for 

Building-Integrated PV Systems 

Specialized 

Technology 

Resources, Inc. 

Development of New Low-Cost, 

High-Performance, PV Module 

Encapsulant/Packaging Materials 

2.3 Yield, Durability, and Reliability 

The FY 2006 YDR subtask comprises the costshared PVMR&D subcontracts in Table 4 resulting 

from a FY 2003 competitive solicitation. The focus 

is improving module manufacturing processes to 

increase module reliability, system and systemcomponent packaging, system integration, 

manufacturing and assembly; product 

manufacturing flexibility; and BOS development, 

including storage and quality control. It 

emphasizes enhancing reliability of the module, 

system components, and complete system. 

Table 4. FY 2005 YDR Subcontractors 

Subcontractor Title of Subcontract 

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 

GE Energy Solar Cell Design for Manufacturability 

PowerLight 

Corporation 

Accelerating PV Cost Effectiveness 

Through Systems Design, 

Engineering, and Quality Assurance 

SolarWorld Manufacturing Improvements in CZ 

Silicon Module Production 

SunPower Automated Manufacturing of High 

Efficiency Modules 

Xantrex 

Advanced, High Reliability, System 

Integrated 500-kW Photovoltaic 

Inverter Development 

First Solar 

Implementation of Reliable 

Manufacturing of Higher Efficiency 

Module 

Shingleton 

One-Axis Trackers – Improved 

Reliability, Durability, Performance, 

and Cost Reduction 

BP Solar 

Development of Large High-Voltage 

PV Modules with Improved Reliability 

and Lower Cost 

SCHOTT Solar 

Subcontracts under “PV Module And 

Component Yield, Durability, And 

Reliability” solicitation 

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3. Results and Accomplishments 

3.1 PV Manufacturing R&D Management 

To measure progress toward contributing to the 

Solar Program, the PVMR&D Project completed 

its FY 2006 milestone to “Analyze U.S. PV 

Industry Cost/Capacity/Recapture data and 

produce capacity-weighted, industry average 

results.” This milestone provides input to DOE 

and NREL decision makers on the growth of the 

fraction of production silicon versus thin films. The 

manufacturing plant utilization for Si modules has 

to date been quite stable from year to year, while 

thin-film manufacturing plant utilization has 

fluctuated much more. There was a pause in the 

growth of Si production in 2003–2005, attributable 

to a silicon feedstock shortage. This growth pause 

is projected to continue into 2006, but a return to 

normal growth is anticipated in 2007. 

U.S. PV Industry. Both historical and projected 

values for manufacturing cost and capacity were 

compiled in collaboration with PV industry 

partners. An evaluation of the FY 2005 data, 

completed in May of 2006, indicates progress 

toward achieving the Solar Program’s cost goals, 

as well as demonstrating cost savings directly 

1000 Production Production Ratio Plant Utilization Production (MW) 100 

10 

x-Si 1 Thin Film related to project participation. 1.0 

Figure 1 shows the progress in combined 

crystalline-Si/thin films/concentrator module 

manufacturing production cost versus capacity 

from 1992 to 2005, as well as the projections to 

2010. From 1992 to 2005, the average module 

manufacturing cost decreased 54% to $2.73/Wp 

(in 2005 dollars), an average 5.7%/year decrease, 

while the production capacity increased 18.5-fold 

to 251 MW, an average 25%/year increase. These 

numbers represent a slight slowdown in cost 

decrease and capacity increase reported 

previously for the 1992–2003 data set. This 

0.5 

Manufacturing Plant Utilization 2005 data 0.0 

1.0 1995 2000 2005 

0.8 

Year thin films

0.6 

x-Si 

0.4 

Production Ratio 0.2 x-Si/(x-Si+Thin Films) 

change is attributable to a recent temporary 0.0 

1995 2000 2005 shortage in silicon feedstock as discussed further Year 

below. 

Fig. 2. Manufacturing production levels, plant 

utilization (production/capacity), and production 6 1992 Overall PV Industry: ratio for crystalline silicon and thin-film PV. 

"Average" Module

Manufacturing Cost ($/Wp)

1993 Crystalline Silicon, Thin Films, 

and Concentrators 5 1994 The relationship between production level and 1995 cost is shown in Fig. 3 in the form of “experience 4 1996 

1998 curves.” In this analysis, the dependence of cost 2005 Data 1999 2003 

3 2000 on cumulative production (i.e. “experience”) is 14 PV Manufacturing 2005

R&D participants with 2001 2006 considered. It is often observed empirically that 

active manufacturing 2002 2 2004 2007 cost decreases according to an inverse exponent lines in 2005. 2008 Direct module manu­ 2009 of the cumulative production. The value of the facturingcost only 

1 (2005 Dollars) 2010 exponent determines the “progress ratio,” the 

2 3 4 5 6 7 8 2 3 4 5 6 7 8 2 

10 100 1000 

Total PV Manufacturing Capacity (MW/yr) 

Fig. 1. U.S. PV module manufacturing cost 

versus capacity

Figure 2 shows the production levels and 

manufacturing plant utilization (production/ 

capacity) over the same time period, for both thinfilm and silicon modules. Also shown is the 

fraction by which the cost falls for each doubling in 

cumulative production. Figure 3 shows that during 

the 1992–2003 period, silicon module production 

cost followed a fairly stable learning curve with an 

87% progress ratio. In 2004–2005 the cost 

actually rose, attributable to the silicon feedstock 

shortage as previously noted. This rise in cost is 

projected to be only a temporary anomaly, and the 

overall trend of costs falling with a roughly 87% 

progress ratio is forecast to continue through 
 

 

 

 

 

 

 

 

 

 

2010. For thin-film production, the data are less 

well described by a learning curve due to an 

anomalous rise in costs in 2001–2003 related to 

redesigns of the modules during that time period. 

The fit to a learning curve is shown in Fig. 3 as the 

dashed line, with a progress ratio of 81% from 

1992 to 2010. 

6 

7 

8 

1 

2 

3 

4 

5 

6 

7 

8 

10

Module Manufacturing Cost (2005$/Wp 

x-Si

 Thin Film

 PR=87%

 PR=81% 

1992 

1993 

2005 2010 

2005 

2010 

2005 data 

100	 101 102 103 104 

Cumulative Production (MW)

Fig. 3. Experience curve plot of module cost vs. 

cumulative production for x-Si and thin-film 

modules. The solid line represents a progress 

ratio=87% fit to the 1992–2003 x-Si data. 

3.2 In-Line Diagnostics and Intelligent Processing 

Under this subtask, the PVMR&D milestone to 

“complete reviews and required redirection for 

remaining subcontracts” focused on guiding the 

IDIP project to a successful conclusion. This 

milestone was completed in December 2005. 

Other significant achievements under this subtask 

were accomplished by individual subcontractors, 

and are described in the following. 

Specialized Technology Resources, Inc. 

“Development of New Low-Cost, HighPerformance PV Module Encapsulant/ Packaging 

Material” 

•	 Cost reduction opportunities for the 

manufacturing of the faster-curing encapsulant 

were identified and initiated. A tension 

management system/winder, part of the cost 

reduction solution, has been fabricated and 

cleared for production utilization. 

•	 A new flame-retardant (FR) technology has 

been developed with PN Solutions to maintain 

the electrical insulation properties of the 

encapsulant. A promising FR formulation was 

manufactured, with samples submitted for 

module qualification and flammability testing. 

Energy Conversion Devices, Inc. 

“Implementation of a Comprehensive On-Line 

Closed-Loop Diagnostic System for Roll-to-Roll 

Amorphous Silicon Solar Cell Production” 

•	 Designed an improved second-generation 

component cell PV capacitive diagnostic tool 

in which: all but one of a dozen electrical 

vacuum feedthroughs have been eliminated; 

all water temperature stabilization systems 

have been removed from the vacuum; the 

system can be quickly and easily removed; the 

electronics have been professionally 

packaged and software and data acquisition 

hardware updated to the latest versions. 

•	 Designed an improved second-generation 

component cell spectrometer. 

•	 Designed an improved reflection spectrometer 

system including: increased signal-to-noise 

from optics changes; incorporation of an 

infrared spectrometer to provide absolute 

thickness measurements; and implementing a 

2-D spectrometer array to measure, online, 

the complete longitudinal and transverse 

deposition profile of each cathode. 

Schott Solar, Inc. 

“Plug and Play Components for BuildingIntegrated PV Systems” 

•	 Developed a dark I-V test station prototype to 

test the ASE-300 module performance and 

ultimately become an in-process inspection tool. 

•	 Developed a new design for free-standing 

mounting system bracket, allowing module to 

be completely free to rotate to shallower angles 

in response to wind forces and preventing it 

from over-rotation; this design has been 

evaluated/validated rigorously, including wind 

tunnel testing on scale-model array design. 

Spire Corporation 

“Development of Automated Production Line 

Processes for Solar Brightfield Modules” 

•	 Design engineering was completed and 

fabrication is under way on a 2-m x 4-m solar 

simulator for module performance testing. 

This single long-pulse system has recently 

achieved commercial success, as Spire has 

sold several long-pulse simulators to PV 

module manufacturers and a test laboratory. 

•	 Initiated development of high-throughput lowstress processes for automated cell string 

assembly from cells as thin as 150 to 200 μm. 

•	 Developed a strategy for implementing a 

computer integrated manufacturing system for 

module line supervisory control and data 

acquisition. 

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3.3 Yield, Durability and Reliability 

The “Large-Scale Module and Component Yield, 

Durability, and Reliability” letter of interest issued 

in FY 2003 focused on addressing the needs of 

two categories. Category A, PV System and 

Component Technology, largely addresses nonmodule aspects of PV systems component 

manufacturing processes. Category B, PV Module 

Manufacturing Technology, primarily addresses 

aspects of module manufacturing processes. 

During FY 2005, 11 of the 17 responses to the 

YDR solicitation that were ranked in the 

competitive range were selected for funding. 

These projects represented a wide spectrum of 

the value chain in the PV industry, ranging from 

BOS work to PV module manufacturing. 

Significant achievements under this subtask by the 

individual subcontractors are described below. 

PowerLight Corporation 

“Accelerating PV Cost Effectiveness Through 

Systems Design, Engineering, and Quality 

Assurance” 

•	 Implemented improvements to data-logger 

capabilities to allow increased communication 

with data collector and inverter systems. 

•	 Developed and implemented improvements in 

the RFT10 sloped roof product to reduce cost. 

These included elimination of foam insulation, 

where little value is achieved, and the 

incorporation of more universal parts in the 

construction process. 

•	 Improved reliability and reduced permitting 

delays through analysis and high wind effects 

and the modeling of system stability during 

seismic events. 

GE Energy, LLC 

“Solar Cell Design for Manufacturability” 

•	 Produced molded wafers with thickness as low 

as 400 μm. 

•	 Specified, purchased, and installed a new pilot 

line for cell processing. 

•	 Produced first metal wrap-through prototypes. 

•	 Improved SiNx process to achieve a 30% 

increase in diffusion length. 

•	 Produced an 11.8%-efficient solar cell. 

Evergreen Solar, Inc. 

“Low-Cost Manufacturing of High-Efficiency, HighReliability String Ribbon Si PV Modules” 

•	 Began pilot operation of the in-situ ribbon 

cutting process. 

•	 Developed and implemented improved 

contacting processes, resulting in cell 

efficiencies as high as 15% on 190-μm ribbons. 

•	 Demonstrated a successful process for 

forming a frameless module all in one 

lamination step. 

SolarWorld Industries America 

“Manufacturing Improvements in CZ Silicon 

Module Production” 

•	 Accomplished a gain in silicon utilization 

through reductions in wire saw (140 to 120 

μm) and wafer thickness (280 to 240 μm). 

•	 Improved cell processing resulting in 16.6% 

cell efficiencies. 

•	 Implemented decay-free glass that cut the 

light-induced degradation in half at the module 

level. 

SunPower Corporation 

“Automated Manufacturing of High Efficiency 

Modules” 

•	 Improved understanding of wafer breakage 

and automated wafer handling techniques. 

•	 Continued development of Pb-free soldering. 

•	 Developed new interconnects for cell-cell 

stringing that reduced forces on solder joints 

by >50%. 

•	 Investigated and implemented antireflection 

glass, resulting in an efficiency gain of 2%. 

BP Solar 

“Development of Large High-Voltage PV Modules 

with Improved Reliability and Lower Cost” 

•	 Employed thermal modeling to guide 

improvements in casting run time (14%), 

energy consumption (18%), sizing cycle time 

(15%), carrier lifetime, and number of defects 

(50%). 

•	 Began evaluation of the impact of brick 

surface roughness on yield. 

•	 Developed improvements in module 

production through the implementation of antireflection glass (2.4% more power), evaluation 

of polymer frames to eliminate shorting, and 

improved module termination to improve 

reliability. 

Dow Corning Corporation 

“High Performance Packaging Solutions for LowCost, Reliable PV Modules” 

•	 Continued development through analysis and 

down-selection of new cell adhesive layers. 

• Developed improved encapsulation 

formulation with the potential for faster 

processing speed and the potential to 

eliminate traditional laminator processing. 

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First Solar 

“Solar Cell Design for Manufacturability” 

•	 Demonstrated the ability to fabricate CdTe 

modules using a modified transparent 

conducting oxide and buffer layer with a 

demonstrated potential for >0.5% efficiency 

point improvement. 

•	 Improved vapor transport deposition 

distributors for CdS, resulting in a 35% 

reduction in CdS thickness variation. 

•	 Improved the sputtered interfacial layers and 

wet spray activation process, resulting in 

>0.3% efficiency improvement over the 

baseline process. 

Xantrex Technology 

“Advanced, High Reliability, System Integrated 

500-kW Photovoltaic Inverter Development” 

•	 Generated a detailed Functional Specification 

document to guide the development and 

evaluation of an improved inverter. 

•	 Improved the high-power electronics and 

packaging design, resulting in cost reduction 

and reliability enhancements greater than the 

25% targets. 

•	 Improved the low-power electronics and control 

design, resulting in a cost savings of 52%. 

•	 Improved the design of system-integrated 

features, resulting in a 75% reduction in cost. 

Shingleton Design 

“Advanced, High Reliability, System Integrated 

500-kW Photovoltaic Inverter Development” 

•	 Developed a roadmap toward reducing costs 

of the drive system. 

•	 Reduced costs by >50% for the bearing 

housing and insert sections of the single axis 

tracker. 

•	 Developed guidance manuals to assist with 

design, installation, operation and 

maintenance of tracking systems. 

•	 Improved system design software, resulting in 

time savings and quality improvements. 

Schott Solar, Inc. 

“High Performance Multicrystalline Silicon 

Modules and Products” 

•	 Reduced impurities in in silicon feedstock by 

installing new processing equipment. 

•	 Utilized a protective coating for vulnerable 

furnace components that allows higher oxygen 

content within the device and results in higher 

efficiencies. 

•	 Modified and successfully tested a new hotzone design for growth furnaces to reduce 

stress. 

•	 Improved device efficiency through the use of 

B-doped wafers. 

•	 Developed materials, patterning designs, and 

an approach for the integrated module 

manufacture of backplane interconnects. 

•	 Developed module designs for several 

building-integrated photovoltaic (BIPV) 

applications. 

4. Planned FY 2006 Activities 

PVMR&D Project procurements are framed to 

specifically address milestones under the Solar 

Program. Under the continuing IDIP procurement, 

PVMR&D will continue to focus on integrating 

state-of-the-art process controls with current 

production technology in support of the FY 2007 

EERE cost goal and conduct end-of-year 

measurements to meet the FY 2007 EERE Joule 

Milestone for U.S.-made, commercial crystalline 

silicon PV modules of 14.5% conversion 

efficiency. The focus of the subcontracts under 

the YDR procurement will be on enhancing field 

reliability and durability, as well as manufacturing 

yield, which also supports the FY 2007 EERE 

milestones mentioned above. 

The major task milestones and expected 

accomplishments of this project during FY 2007 

include: 

•	 Verify a conversion efficiency of 14.5%, using 

standard laboratory measurements, of U.S.­

made, commercial crystalline silicon PV 

modules. (4th Q JOULE milestone) (09/07) 

•	 Complete initial incremental funding of 

subcontracted research under “Large-Scale 

Module and Component Yield, Durability, and 

Reliability” prior to identification of Technology 

Pathway Partnerships. (11/06) 

•	 Analyze the FY 2006 U.S. PV industry 

cost/capacity/recapture data to identify the 

capacity-weighted, industry average. (05/07) 

•	 Complete research under "In-Line Diagnostics 

and Intelligent Processing." (06/07) 

•	 Complete required redirections and 

incremental funding of subcontracted research 

under “Large-Scale Module and Component 

Yield, Durability, and Reliability” (09/07) 

The research addressed by the PVMR&D Project 

is chosen by the U.S. PV industrial participants in 

the form of proposals received in response to 

Photovoltaic R&D

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76
 

 

 

 

 

 

 

 

competitive solicitations. As such, these are 

systems-driven issues and are of the highest 

importance to PV manufacturers. Actual projects 

are chosen primarily by evaluators external to the 

government using criteria constructed to select, in 

a technology-neutral manner, those activities most 

likely to contribute to the PVMR&D Project goals 

and objectives. 

Subcontracts under this project have continued to 

contribute to both the reduction of PV system 

costs and the improvement of PV manufacturing 

processes and products. In addition, 

representatives of the PV industry have generally 

identified this project as one of the most, if not the 

most, important and successful projects in the 

DOE Program. As such, the PVMR&D Project will 

continue to support manufacturing R&D consistent 

with the Systems-Driven Approach that has been 

established under this partnership of industry, 

laboratories, and government by implementing 

multi-year subcontracts that address industryidentified problems selected through competitive 

and fair processes. 

5. Major FY 2006 Publications 

Margolis, R., Mitchell, R., and Zweibel, K., 

“Lessons Learned from the Photovoltaic 

Manufacturing Technology/PV Manufacturing R&D 

and Thin-Film PV Partnership Projects,” NREL/TP520-3 9780, September 2006. 

Nowlan, M.J., Murach, J.M., Sutherland, S.F., 

Miller, D.C., Moore, S.B., and Hogan, S.J., 

“Development of Automated Production Line 

Processes for Solar Brightfield Modules,” Final 

Annual Technical Progress Report, 1 July 2004–15, 

October 2005, NREL/SR-520-40406, August 2006. 

Rand, J.A., and Culik, J.S., “High Volume 

Manufacturing of Silicon-Film Solar Cells and 

Modules,” Final Subcontract Report, 26 February 

2003–30 September 2003, NREL/SR-520-38677, 

October 2005. 

Wohlgemuth, J., Narayanan, M., “Large-Scale PV 

Module Manufacturing Using Ultra-Thin 

Polycrystalline Silicon Solar Cells,” Final 

Subcontract Report, 1 April 2002–28, February 

2006, NREL/SR-520-40191, July 2006 

Wohlgemuth, J., Narayanan, M., “Large-Scale PV 

Module Manufacturing Using Ultra-Thin 

Polycrystalline Silicon Solar Cells,” Final 

Subcontract Report, 1 April 2002–28 February 

2006, NREL/SR-520-40191, 2006. 

Friedman, D.J.; Mitchell, R.L.; Keyes, B.M.; 

Bower, W.I.; King, R.; Mazer, J., “PV 

Manufacturing R&D Project Status and 

Accomplishments under In-Line Diagnostics and 

Intelligent Processing and Yield, Durability and 

Reliability,” Proceedings of the 4th World 

Conference on Photovoltaic Energy Conversion 

(Hawaii, 2006), NREL/CP-520-39904, May 2006. 

Botkin, J., “Accelerating PV Cost Effectiveness 

Through Systems Design, Engineering, and 

Quality Assurance,” Phase I Annual Technical 

Report, 4 November 2004–3 November 2005, 

NREL/SR-520-40335, July 2006. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006. 

Principal Investigator 

Organization/ Location/e-mail of Research Activity Description/Title 

($K) 

FY 

2006 

($K) 

Cost 

Share 

BP Solar International, Inc. 

John Wohlgemuth john.wohlgemuth@bp.com 

Frederick, MD Large-Scale PV Module 

Manufacturing Using Ultra Thin 

Polycrystalline Silicon Solar Cells 0*

20 

0* 

27 

Energy Conversion Devices, Inc. 

Tim Ellison time@ovonic.com 

Troy, MI 

hous 

Implementation of a Comprehensive 

On-Line Closed-Loop Diagnostic 

System for Roll-to-Roll Amorp 

Silicon Solar Cell Production 

500* 

0 

500* 

0 

Spire Corporation 

Michael Nowlan mnowlan@spirecorp.com 

Bedford, MA esses for Solar 

Brightfield Modules 

Development of Automated 

Production Line Proc 30* 

395 

29* 

384 

77

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Organization/ 

Principal Investigator Location/e-mail of Research Activity 

Description/Title FY 

2006 

($K) 

Cost 

Share 

($K) 

Schott Solar, Inc. 

Miles Russell 

Billerica, MA 

miles.russell@us.schott.com 

Plug and Play Components for 

Building-Integrated PV Systems 

0 

0* 

0 

0* 

Specialized Technology 

Resources, Inc. 

Ryan Tucker 

Enfield, CT 

susan.agro@strus.com 

Development of New Low-Cost, HighPerformance PV Module 

Encapsulant/Packaging Material 

5 

0* 

5 

0* 

Dow Corning Corporation 

Barry Ketola 

Midland, MI 

barry.ketola@dowcorning.com 

High Performance Packaging 

Solutions for Low Cost, Reliable PV 

Modules 

215 

550* 

215 

550* 

Evergreen Solar, Inc. 

Jack Hanoka 

Marlboro, MA 

hanoka@evergreensolar.com 

Low-Cost Manufacturing of HighEfficiency, High-Reliability String 

Ribbon Si PV Modules 

390 

668* 

390 

668* 

GE Energy, LLC 

James Rand 

Newark, DE 

im.rand@ps.ge.com Solar Cell Design for Manufacturability 270 

375* 

274 

377* 

PowerLight Corporation 

Jonothan Botkin 

Berkeley, CA 

jbotkin@powerlight.com 

Accelerating PV Cost Effectiveness 

Through Systems Design, 

Engineering, and Quality Assurance 

232 

120* 

779 

346* 

SolarWorld Industries America 

Theresa Jester 

Camarillo, CA 

Theresa.jester@shellsolar.com 

Manufacturing Improvements in CZ 

Silicon Module Production 

445 

500* 

442 

499* 

SunPower Corporation 

Doug Rose 

Sunnyvale, CA 

Doug.Rose@sunpowercorp.com 

Automated Manufacturing of High 

Efficiency Modules 

385 

300* 

407 

325* 

Xantrex Technology, Inc. 

Raymond Hudson 

San Luis Obispo, CA 

Ray.Hudson@xantrex.com 

Advanced, High Reliability, System 

Integrated 500-kW Photovoltaic 

Inverter Development 

79 

250* 

79 

250* 

First Solar, LLC 

Greg Helyer 

Perrysburg, OH 

ghelyer@FIRSTSOLAR.COM 

Implementation of Reliable 

Manufacturing of Higher Efficiency 

Module 

320 

100* 

324 

101* 

Shingleton Design, LLC 

Jefferson Shingleton 

Auburn, NY 

jefferson@shingleton.com 

One-Axis Trackers – Improved 

Reliability, Durability, Performance, 

and Cost Reduction 

50 

170* 

109 

371* 

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 

288 

150* 

270 

140* 

SCHOTT Solar, Inc. 

Mark Rosenblum 

Billerica, MA 

mark.rosenblum@us.schott.com 

High Performance Multicrystalline 

Silicon Modules and Products 

100 

310* 

97 

300* 

* Funded with prior years (FY 2004 & FY2005) funds. 

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78
 

Technology Development 

The U.S. Department of Energy, in cooperation with the U.S. photovoltaics industry, seeks to 

advance PV performance and systems engineering, bolster the U.S. market for PV, and develop 

technology suitable for integration into residential and commercial building. This work also 

includes building-integrated photovoltaics (BIPV), a rapidly growing solar application in which PV 

modules serve the dual purpose of replacing conventional building materials and generating 

electricity. By offering more than one functionality, BIPV systems will help cross the profit 

threshold essential to significant growth in distributed, grid-connected electricity markets. 

DOE recognizes that outreach and analysis activities are necessary for a national R&D program 

to remain viable in a rapidly changing energy sector. Through the Million Solar Roofs (MSR) 

Initiative, which concluded in FY 2006, the Solar Program helped to develop local and regional 

markets for all solar technologies by working with communities to identify and encourage new 

applications. The success of MSR helped lay the foundation for the Solar America Initiative (SAI), 

which President George Bush announced in February 2006. 

The Solar Decathlon—an intercollegiate competition to design, build, and operate attractive, 

energy-efficient, and totally solar-powered houses—is a high visibility event held on the National 

Mall in Washington, D.C. Between the two Decathlons (held in 2002 and 2005), as many as a 

quarter of a million people have come to visit the homes and learn about the architectural appeal 

and myriad benefits of solar energy in the built environment. 

A sample of FY 2006 accomplishments in Technology Development follows. 

PV System Evaluation and Optimization 

•	 Recorded and analyzed long-term (months) system performance data for eight array/inverter 

combinations providing system, array, and inverter performance characteristics based on 

daily energy production. 

PV Systems Engineering 

•	 Provided systems performance analyses and results and feedback to industry, including 

multiple long-term, small systems monitoring at NREL; new systems from SunPower and 

Shell Solar installed at NREL at industry request; damp heat and thermal cycling for 

SunPower; and soiling tests for GE Energy. 

Domestic PV Applications 

•	 Loaned solar electric charging stations to help residents of Kiln, MS, recover from the 

devastation of Hurricane Katrina. The systems provided much-needed power to this town of 

about 2,000 people, located 13 miles north of Bay St. Louis, MS, and the Gulf of Mexico. 

PV Systems Analysis 

•	 Expanded the number of default markets/systems included in the Solar Advisor Model, and 

used the model to support the SAI Technology Pathway Partnership (TPP) activities. 

Building-Integrated Photovoltatics 

•	 Concluded the implementation of the 2005 Solar Decathlon university competition, releasing 

the final regulations, solidifying sponsors, supporting teams, and scoring, monitoring, and 

carrying out all aspects of the event. 

Million Solar Roofs Initiative 

•	 Closed out program, published final report, and held wrap-up meeting in fall 2006 at the Solar 

Electric Power Association Conference. 

Regional Experiment Stations 

•	 Participated in Federal Opportunity Announcement Technical Committee to determine 

accuracy of all data submitted in SAI TPP proposals. 

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____________________________________________________________________________________ 

 

 

 

 

PV System Evaluation and Optimization 

Performing Organization: Sandia National Laboratories (SNL) 

Key Technical Contacts:	 David King (SNL Primary Contact), 505-844-8220, dlking@sandia.gov 

Sig Gonzales, (DETL, Inverter Contact), 505-845-8942, 

sgonza@sandia.gov 

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

FY 2006 Budget:	 $620K 

Objectives 

The key FY 2006 objectives for this R&D project were to: 

•	 Implement and operate a versatile fully instrumented PV System Optimization Laboratory
 

(PVSOL) for system and inverter performance, modeling, and reliability research.
 

•	 Develop, validate, and apply new testing and analysis protocols, based on energy production, 

which are 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 systems 

and inverters, in collaboration with manufacturers, system integrators, the Florida Solar Energy 

Center (FSEC), the Southwest Technology Development Institute (SWTDI), and Behnke, Erdman 

& Whitaker Engineering (BEW). 

•	 Investigate advanced PV system concepts, manufacturing methods, and deployment strategies 

that improve performance, reliability, and cost, and accelerate deployment. 

Accomplishments 

•	 Recorded and analyzed long-term (months) system performance data for eight array/inverter 

combinations providing system, array, and inverter performance characteristics based on daily 

energy production. Initial results documented in the 4th World Conference on Photovoltaic Energy 

Conversion (WCPEC) publication. 

•	 Initiated a comprehensive testing and analysis effort to develop a generally applicable PV inverter 

performance model. The beta version developed is widely applicable, easy to implement, and 

provides the accuracy required for energy modeling, technology comparisons, and system 

monitoring. 

•	 Conducted detailed module performance characterization of 15 SunPower 220-W modules with 

three types of glass superstrate—standard, sputtered antireflection (AR) coating, and solutiondeposited AR coating—and then installed three 1-kW systems using the modules to evaluate 

their relative energy production. Verified improved angle-of-incidence characteristics and 4% 

greater energy production with AR-coated glass. Documented in 4th WCPEC publication. 

•	 Arizona State University PV Testing Lab (ASU/PTL) successfully implemented SNL’s 

module/array outdoor testing and data analysis protocols for generating performance coefficients 

for the “module database” used by Maui Solar, the DOE Solar Advisor Model (SAM), and others. 

4th WCPEC publication. 

•	 Completed grid-tied performance evaluation per IEEE 1547 for PV Powered 30-kW prototype 

inverter and GE 3600 inverter deliverable from High Reliability Inverter Initiative. 

•	 Provided product development assistance for PV Powered to improve their maximum power point 

tracking (MPPT) algorithm and address difficulties meeting C62.45 surge suppression compliance 

for their commercial PVP-2800XV inverter. 

•	 Provided lab test support for Professor Michael Ropp of South Dakota State University (SDSU) 

for early validation of a detailed electrical model of internal inverter functions (e.g., MPPT, antiislanding, switching frequency, and non-linear loads). Three 4th WCPEC publications. 

Photovoltaic R&D

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____________________________________________________________________________________ 

 

 

 

 

 

•	 Provided initial concepts for a System Testing Protocol needed to evaluate DOE Solar America 

Initiative (SAI) system-level deliverables, and supported the development of a residential-scale 

system and inverter testing protocol requested by the Rural Utility Service (RUS) and to be 

conducted by FSEC. 

•	 Developed and applied new nondestructive ultrasonic imaging procedure intended for rapid 

evaluation of solder bond quality during production line cell tabbing (interconnection) process. 

Used capability to assist Advent Solar and Sharp (PowerLight) in module diagnostics and 

production process improvement. 

Future Directions 

•	 Continue the development and implementation of system and inverter test and evaluation 

protocols in support of industry participants in the SAI, providing both field-testing of large 

systems as well as laboratory optimization of small (<5kW) systems or components.
 

•	 Complete development and documentation of general inverter performance model for PV system 

performance modeling, including an initial database with inverter parameters derived from 

manufacturer specification sheets, system field tests, and test results recorded by laboratories 

supporting the California Energy Commission (CEC). 

•	 Perform concerted research effort to characterize, document, and model PV system, array, and 

inverter performance (energy production) and reliability through detailed analysis of fully 

integrated and instrumented PV systems. Research conducted in coordination with 

module/inverter manufacturers, system integrators, FSEC, SWTDI, BEW, and CEC. 

•	 Develop improved field-data acquisition techniques and analysis protocols for monitoring PV 

system performance and providing real-time performance assessment, as well as diagnostics. 

1. Introduction 

The System Evaluation and Optimization activities 

at Sandia National Laboratories closely match the 

needs of manufacturers and system integrators. 

The research effort provides laboratory and fieldtest information needed to establish the 

performance and reliability status of current PV 

systems, and to identify improvements in system 

design and component integration for nextgeneration systems. These activities are key to 

meeting the DOE Solar Energy Technologies 

Program Multi-Year Program Plan targets, the 

goals of the U.S. PV Industry Roadmap, and the 

objectives of the new DOE Solar America Initiative 

(SAI). As such, the System Evaluation and 

Optimization Project is the focal point within the 

DOE Solar Program at which the technical issues 

of PV component manufacturers, system 

integrators, and users converge. 

2. Technical Approach 

Major research activities for FY 2006 included 

detailed module, array, inverter, and system 

research aimed at understanding and improving 

the performance, reliability, and cost of fully 

integrated PV systems. Capabilities and expertise 

associated with SNL’s PV Systems Optimization 

Lab (PVSOL) and the companion Distributed 

Energy Technology Lab (DETL) were used to 

conduct this research. 

The PVSOL accurately evaluates the performance 

of both component (modules, arrays, inverters) 

and complete systems based on energy 

production. Continuous recordings of energy flow 

in and out of all system components provide 

detailed performance information, as well as longterm aging characteristics, for both inverters and 

arrays under all weather conditions. Accurate 

performance modeling for the array, inverter, and 

system provide real-time system performance 

metrics and diagnostic capabilities. 

The project had three subtasks, funded as 

indicated in the following table. 

Task Title FY 2006 

Budget ($K) 

PV System Performance Testing 

and Modeling 260 

Inverter Performance Testing and 

Industry R&D Support 260 

Advanced PV System Concepts 100 

The System Performance Testing and Modeling 

Task focused on module and array performance 

characterization and modeling, development of a 

new generally applicable inverter performance 

model, and development of system testing and 

81

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monitoring protocols based on energy production. 

Experience gained in this task supports the 

Modeling Leadership Team associated with the SAI. 

The Inverter Performance Testing and R&D 

Support Task conducted a variety of 

comprehensive inverter testing to aid inverter 

development, evaluate new concepts, benchmark 

performance and utility compatibility of commercial 

inverters, initiate long-term field aging at SNL, 

FSEC, and SWTDI, and provide performance 

parameters needed for new inverter performance 

model. This activity addresses the “Inverter 

Testing and Industry Support” section of the Solar 

Program Multi-Year Plan and is a key element of 

the SAI beginning next fiscal year. 

The Advanced PV System Concepts Task 

addresses improvements in PV system 

manufacturing methods, new inverter design 

concepts, and new equipment and procedures for 

real-time performance monitoring of PV systems 

and components. Limited funding was available 

this fiscal year, but several concepts were 

identified for next fiscal year, all complementary to 

objectives of the SAI. 

3. Results and Accomplishments 

The primary results and accomplishments for this 

project were summarized previously. FY 2006 

milestones for the three subtasks included: 

•	 Transfer of SNL module/array outdoor testing 

procedures to ASU/PTL with intercomparison 

measurements completed March 2006; 

documented in 4th WCPEC publication (May 

2006). 

•	 Performance characterization and modeling of 

eight PV arrays completed in September 2006 

in support of energy modeling analyses and 

long-term inverter testing. 

•	 Using fully instrumented PVSOL systems, 

demonstrated new procedures and high 

accuracy for energy-based performance 

models and monitoring of systems. 

Documented results in 4th WCPEC publication 

(May 2006). Results led to draft protocol for 

system performance testing associated with 

SAI deliverables. 

•	 Completed baseline performance evaluation of 

five commercial inverters in January 2006, 

now in long-term system aging at FSEC, 

SWTDI, and SNL. Plus, evaluation of three 

additional inverters by industry request 

completed September 2006. 

•	 Completed development of beta version of a 

general inverter performance model in 

September 2006, with final version for use in 

DOE SAM model and in commercial system 

design software planned for February 2007. 

•	 Investigation and analysis of system 

manufacturing, reliability, installation cost, PV 

technology, and system design sensitivities 

conducted in support of DOE SAM model 

development and analyses preceding funding 

opportunity announcement for SAI. 

•	 A continued effort resulted in the development 

of an innovative high-reliability micro-inverter 

design for the advanced “AC Building Block” 

PV system concept. Documented in 4th 

WCPEC publication. See the Inverter and 

BOS Development project for additional 

information on development of new highreliability inverter concepts. 

One highlight from the project was the 

development of a widely applicable inverter 

performance model for use in system-performance 

analyses and field-performance monitoring and 

diagnostics. The model was found to be applicable 

and accurate for a wide variety of both residential 

and commercial-scale inverters, provided the 

inverter had stable and repeatable performance 

characteristics. Three levels of accuracy are 

possible with the model, depending on the type of 

test data available: specification sheet data, fieldtest data during system operation, or detailed 

laboratory measurements as performed by SNL 

and CEC testing laboratories. Figure 1 illustrates 

measured performance results by a CEC 

laboratory for a typical inverter at six power levels 

and three input DC-voltage levels, along with 

modeled performance. Factors included in the 

model are peak (rated) AC power, peak DC power 

with DC voltage dependence, DC power (self 

consumption) required to initiate the inversion 

process with voltage dependence, nonlinear ACpower versus DC-power relationships with voltage 

dependence, and night time "tare" power required 

for sensing array voltage. 

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SMA SWR2500U Inverter, CEC Data, 5 Samples 

0 

500 

1000 

1500 

2000 

2500 

3000 

AC Power (W) 

Vdc = 252 

Vdc = 302 

Vdc = 483 

Model at 252V 

Model at 302V 

Model at 483V 

40 

0 500 1000 1500 2000 2500 3000 

DC Power (W) 

100 

90 

80 

70 

60 

50 

Fig. 1. SNL inverter performance model (lines) 

using CEC-measured data (symbols) at six power 

levels and three voltage levels. AC power and 

efficiency as a function of DC power are shown. 

Inverter Efficiency (%) 

4. Planned FY 2007 Activities 

Activities planned for FY 2007 will be largely 

defined by the test and evaluation requirements 

stemming from industry partnerships associated 

with the DOE Solar America Initiative. 

5. Major FY 2006 Publications 

B. Li, D. King, W. Boyson, G. Tamizmani, 

“Implementation of Sandia Outdoor Photovoltaic 

Test Method and Performance Model at Arizona 

State University,” 4th WCPEC, Hawaii, May 2006. 

D. Rose, O. Koehler, N. Kaminar, B. Mulligan, D. 

King, ”Mass Production of PV Modules with 18% 

Total-Area Efficiency and High Energy Delivery 

Per Peak Watt,“ 4th WCPEC, Hawaii, May 2006. 

D. King, G. Galbraith, S. Gonzales, A. Murray, J. 

Ginn, “Array Performance Characterization and 

Modeling for Real-Time Performance Analysis of 

Photovoltaic Systems,” 4th WCPEC, May 2006. 

W. Bower, R. West, A. Dickerson, “Innovative PV 

Micro-Inverter Topology Eliminates Electrolytic 

4th Capacitors for Longer Lifetime,” WCPEC, 

Hawaii, May 2006. 

C. Whitaker, J. Newmiller, W. Bower, “Inverter 

Performance Certification: Results from the 

Sandia Test Protocol,” 4th WCPEC, Hawaii, May 

2006. 

M. Ropp et al., “Discussion of a Power Line 

Carrier Communication-Based Anti-Islanding 

Scheme Using a Commercial Automatic Meter 

Reading System,” 4th WCPEC, Hawaii, May 2006. 

M. Ropp et al., “Simulation and Experimental 

Study of the Impedance Detection Anti-Islanding 

Method in the Single-Inverter Case,” 4th WCPEC, 

Hawaii, May 2006. 

M. Ropp et al., “Discussion of the Physical 

Mechanisms Behind the Observed Behavior of 

Motors in Islanded Loads,” 4th WCPEC, May 2006. 

J. Wiles and W. Bower, “Changes in the National 

Electric Code for PV Installations,” 4th WCPEC, 

Hawaii, May 2006. 

6. University and Industry Partners 

In FY 2006, a $10K contract was placed with 

ASU/PTL involving the technology transfer, 

implementation, and validation for the SNL 

outdoor module testing and data analysis protocol 

required to determine parameters for the "module 

database" initiated by SNL. 

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____________________________________________________________________________________ 

 

PV Systems Engineering and Performance 

Performing Organizations: National Renewable Energy Laboratory (NREL)

 Sandia National Laboratories (SNL)

 DOE Golden Field Office (DO/GO) 

Key Technical Contacts:	 Carol Riordan (NREL, Primary Contact), 303-384-6780, 

carol_riordan@nrel.gov 

Carl Osterwald (NREL PV Systems Performance & Standards), 303-384-

6764, carl_osterwald@nrel.gov 

Daryl Myers (NREL Solar Radiometry & Radiometry), 303-384-6768, 

daryl_myers@nrel.gov 

Ward Bower (SNL, Codes, Standards & Certification), 505-844-5206, 

wibower@sandia.gov 

Glenn Doyle (DOE/GO, Codes, Standards & Certification), 303-275-

4706, glenn.doyle@go.doe.gov 

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

FY 2006 Budgets:	 $1,475K (NREL), $100K (SNL) 

Objectives 

The key FY 2006 objectives for the Systems Engineering and Performance Project were to: 

•	 Determine, characterize, and document the near- and long-term performance and reliability of 

candidate, emerging PV technologies in the context of a small, grid-connected, system; provide 

benchmark-type data and analyses, in a continuing fashion, to the Systems-Driven-Approach 

activities. 

•	 Assist the PV industry and community with the development and implementation of codes, 

standards, and certification practices to assure safe installations that perform as expected. 

•	 Provide the DOE Solar Technologies Program with world-class and traceable solar radiometric 

capabilities, measurements, and standards. 

Accomplishments 

•	 Provided systems performance analyses and results and feedback to industry (e.g., multiple longterm, small systems monitoring at NREL; new systems from SunPower and Shell Solar installed 

at NREL at industry request; damp heat and thermal cycling for SunPower; soiling tests for GE 

Energy). 

•	 NREL and SNL continued collaborations with industry to evaluate performance-based 

assessments of module/system performance using a combination of models, which fed into the 

benchmarking and systems modeling to support the Solar America Initiative (SAI); implemented 

improvements to PVWATTS systems analysis software and posted on the Web. 

•	 Chaired American Society for Testing and Materials (ASTM) standards activities and provided 

standards support for PowerMark and Sunset Technologies (International Electrotechnical 

Commission [IEC] Secretariat). 

•	 Led Industry Forum and introduced 42 proposed changes for the 2008 edition of the National 

Electrical Code. 

•	 Led IEC standards developments related to inverter and systems test methods. 

•	 Chaired North American Board of Certified Energy Practitioners (NABCEP) test committee with 

two sets of test updates to correspond to testing schedules. 

•	 Supported SAI Market Transformation formulations. 

•	 Transferred World Radiometric Reference to NREL Reference Absolute Cavity Radiometers 

through the International Pyrheliometer Comparison X. 

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____________________________________________________________________________________ 

 

 

 

Future Directions 

•	 The draft (pre-appropriations) of the FY 2007 Annual Operating Plan specifies continuing R&D on 

PV systems engineering and performance R&D, solar radiation and metrology R&D, and codes, 

standards, and certification, with the objective of improving PV performance, providing broadband 

and spectral irradiance measurement capability with traceability to world radiometric standards, 

and removing barriers and facilitating system deployment through codes, standards and 

certifications to meet the mid- and long-term SAI cost goals for competitive PV systems. 

•	 Assuming the launch of the SAI, these PV systems engineering and performance, solar 

radiometry and metrology R&D, and codes/standards/certification agreements will play a major 

part in the test and evaluation of deliverables from the SAI Technology Pathway Partnerships, 

including application and development of test and evaluation protocols for module performance 

and energy modeling. 

1. Introduction 

The major thrust of this project is the near-term 

and long-term performance monitoring, 

characterization, and modeling of current- and 

emerging-technology, small (<5 kWp), gridconnected, prototype systems installed and 

operating at NREL’s Outdoor Test Facility (OTF). 

Critical to this effort is a supporting task that 

provides world-class and traceable measurements 

and instrumentation for solar radiometry. The 

resultant precision and accuracy of the PV system 

(and module) performance measurements is 

determined by the quality, precision, and accuracy 

of the measurements of the incident (on the PV 

arrays) solar irradiance (i.e., “power in”). This 

project also includes very important activities 

aimed at supporting the development of industryconsensus/adopted codes, standards, and 

certification that cover PV systems, components, 

and installation practices. The project provides 

leadership and support in creating and 

implementing codes and standards for quality, 

safe, and cost-effective systems. This work 

insures that codes, standards and certifications 

are in place to pave the way for wide varieties of 

PV installations and to insure interconnect issues 

with utilities are resolved. 

This project is integral to the Solar Energy 

Technologies Program multi-year technical plans 

because it provides credible/independent data, 

analyses, and assessments of the performance 

and reliability metrics that are required in 

benchmarking the candidate technologies and 

supporting the Systems Driven Approach (SDA) to 

R&D management. 

2. Technical Approach 

The technical approach for this project included 

providing: 

•	 Quarterly engineering test reports on at least 

seven small PV systems at the NREL OTF 

that provide the module manufacturers and 

the DOE Solar Program with independent 

analyses of energy performance ratings and 

long-term degradation rates at the system 

level. 

•	 An improved, on-line, PVWATTS software 

program/model that provides decision makers, 

the public, and the industry with credible 

estimates of PV system electric generation 

and costs for specific geographic locations 

nationally and internationally. 

•	 Robust technical support of important national 

standards, codes, and testing and certification 

activities, which are needed to assure safe 

installations that perform as expected. 

•	 Continued world-class solar radiometric, and 

therefore PV system performance, 

measurements and instrumentation. 

•	 PV system performance and reliability data 

and analyses required by the DOE Solar 

Program’s SDA activities (e.g., benchmarking) 

and analyses. 

Agreements under this project were: 

Agreement Title FY 2006 

Budget ($K) 

PV System Performance and 

Standards (NREL) 780 

Solar Radiometry and Metrology 

(NREL) 695 

Codes, Standards, and Certification 

(SNL and DOE/GO) 100 

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Subcontracts included support for PV module and 

systems certification to PowerMark Corp., and 

support for the IEC-TC Secretariat position to 

Sunset Technologies. A contract to BEW 

Engineering supported IEC Working Group 6 

Convener for leading standards-writing activities 

related to inverters and systems. A detailed table 

of subcontractors and funding is included below in 

section 6. 

3. Results and Accomplishments 

3.1. PV System Performance and Standards 

(Osterwald/NREL) 

•	 Delivered quarterly, small-PV system 

performance reports and analyses to module 

manufacturers (9/30/06); 7/06 report was 

skipped due to staff loss, resumed 10/06 

(ongoing). 

•	 Implemented improvements to PVWATTS 

systems analysis software (4/06) (see 

http://rredc.nrel.gov/solar/codes_algs/PVWATTS). 

•	 Continued collaboration with SNL and industry 

to evaluate performance-based assessments 

of module/system performance using a 

combination of models (9/30); fed into 

“benchmarking”/systems modeling to support 

SAI (reported to DOE). 

•	 Installed new technology—Shell Solar Eclipse 

80 CIGS—small PV system at the OTF (and 

initiated long-term testing) and three new 

SunPower 1-kW grid-tied systems for longterm performance monitoring. 

•	 Provided industry support: e.g., damp-heat 

and thermal cycling for SunPower, soiling 

tests for GE Energy, long-term module/small 

system testing being initiated for SunPower; 

participation in standards activities (e.g., 

Chair, ASTM 44.09), external standards 

support through PowerMark and Sunset 

Technologies contracts (ongoing). 

This R&D received very high ratings in the DOE 

Solar Program Peer Review for relevance and 

value (3.8 out of 4.0), with comments such as “The 

relevance of the work is seen as ‘critical to the 

achievement of DOE goals’ and the development 

of sustainable PV markets" and "technical 

approach is ‘well defined and focused.' ” 

3.2 Solar Radiometry and Metrology (Myers/NREL) 

•	 Transferred World Radiometric Reference to 

NREL Reference Absolute Cavity Radiometers 

through results of the International Pyrheliometer Comparison-X (9/30); this provides 

traceability of NREL solar measurements to 

the world reference standard. 

•	 Submitted three solar radiometer calibration 

standards to ASTM; revised and passed final 

ballot approval (7/06). 

•	 Submitted paper for publication on 

environmental influences on solar radiometer 

calibration, “Environmental Thermal Effects on 

the Eppley Normal Incidence Pyrheliometer,” 

to Solar Energy; publication expected as both 

journal article and NREL report (9/06). 

This agreement is critical to reporting the 

accuracy, traceability, and measurement 

uncertainty for NREL measurements (cell, module, 

performance, etc.). Activities in FY 2006 included 

implementing and upgrading the radiometer 

calibration and characterization software; 

calibrating more than 180 broadband and spectral 

radiometers; characterizing 5 research and 

industry solar simulators for PV performance 

testing; updating spectral solar radiation models; 

responding to more than 190 technical requests 

from industry, academia, government 

organizations, and the public; and revising and 

improving pulse spectral solar simulator and 

software. This R&D received very high ratings in 

the DOE Solar Program Peer Review for 

relevance and value. Reviewers commented that 

the activities were “clear, relevant, and necessary; 

an essential element of PV development, 

providing a clear measurement standard 

supporting the goals and objectives of the DOE 

Solar Technologies Program extremely well.” 

3.3 Codes, Standards, and Certification (Bower, 

SNL and Doyle, DOE/GO) 

• Led SNL Industry Forum and introduced 42 

proposed changes for the 2008 edition of the 

National Electrical Code. 

•	 Led IEC standards developments related to 

inverter and systems test methods 

•	 Chaired NABCEP test committee with two 

sets of test updates to correspond to testing 

schedules 

•	 Supported UL Standards Technical Panel in 

revising UL1741 to add testing methods for 

transformerless inverters and to correlate the 

standard with IEEE1547 for anti-islanding 

and interconnect requirements. 

4. Planned FY 2007 Activities 

FY 2007 planned activities are given in the draft 

(pre-appropriations) FY 2007 Annual Operating 

Plan, which is organized differently from previous 

years. 

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Systems Engineering and Performance and Solar 

Radiometry and Metrology will be performed under 

the Technology Evaluation Activity, PV System 

Testing and Evaluation Project, and the 

Component Testing and Evaluation Project 

Agreement on “Solar Radiometry and Metrology,” 

with aspects related to the Systems Analysis 

Project Agreement on “Systems Performance 

Modeling and Database Development.” The R&D 

under these agreements emphasizes PV system 

performance characterization and analysis; 

development of codes and standards/protocols for 

PV module and system performance, and R&D on 

solar radiometry and metrology to maintain 

traceability to world radiometric standards and 

allow measurement uncertainty analysis for cell 

and module performance measurements. These 

agreements also include related tasks on inverter, 

balance of systems, and systems testing and 

evaluation, as well as proposed SAI Market 

Expansion/Transformation Agreements on codes 

and standards. Work under the agreements will 

also support the Test & Evaluation plan for the 

Technology Pathway Partnerships as the SAI 

moves forward. 

5. Major FY 2006 Publications 

C.R. Osterwald, J. Adelstein, J.A. del Cueto, W. 

Sekulic, D. Trudell, P. McNutt, R. Hansen, S. 

Rummel, A. Anderberg and T. Moriarty, “Resistive 

Loading of Photovoltaic Modules and Arrays for 

Long-Term Exposure Testing,” Prog. Photovolt: 

Res. Appl. 2006; 14:567–575. 

S. Wilcox, J.R. Hickey, and D.R. Myers, 

“Environmental Thermal Effects on the Eppley 

Normal Incidence Pyrheliometer,” submited to 

Solar Energy, Sep 2006. 

I. Reda, J.Hickey, C. Long, D. Myers, T. Stoffel, S. 

Wilcox, J.J. Michalsky, E.G. Dutton, and D. 

Nelson, “Using a Blackbody to Calculate Net 

Longwave Responsivity of Shortwave Solar 

Pyranometers to Correct for Their Thermal Offset 

Error during Outdoor Calibration Using the 

Component Sum Method.” Journal of 

Atmospheric and Oceanic Technology, vol. 22, 

October 2005; pp. 1531–1540. NREL Report No. 

JA-560-36646. 

S. Wilcox, M. Anderberg, W. Beckman, 

A. DeGaetano, R. George, C. Gueymard, 

W. Marion, D. Myers, R. Perez, N. Lott, D. Renne, 

P. Stackhouse, F. Vignola, “Towards Production of 

an Updated National Solar Radiation Database.” 

Campbell-Howe, R., ed. Proceedings of the Solar 

2006 Conference, 9-13 July 2006, Denver, 

Colorado (CD-ROM). Boulder, CO: American 

Solar Energy Society (ASES) 6 pp.; NREL Report 

No. CP-560-39597. 

C. Whitaker, J. Newmiller, W. Bower, “Inverter 

Performance Certification: Results from the 

Sandia Test Protocol,” 4th WCPEC, May 2006. 

W. Bower and C. Whitaker, “Test Protocol for 

Certification of Inverter Performance,” 

Proceedings of the DOE 2005 Solar Program 

Review, Denver, CO, Nov 2005. 

J. Wiles and W. Bower, “Changes in the National 

Electric Code for PV Installations,” 4th WCPEC, 

Hawaii, May 2006. 

Organization/Principal 

Investigator Location/e-mail Description/Title of Research Activity FY 2006 

($K)(a) 

PowerMark Corp. 

Steve Chalmers 

Phoenix, AZ 

Chalmers@powermark.org 

U.S. PV module and systems 

certification program support 43.2 

Sunset Technologies 

Howard Barikmo 

Scottsdale, AZ 

hbarkimo@aol.com IEC-TC Secretariat support 33.5 

Behnke, Erdman & 

Whitaker Engineering 

Chuck Whitaker 

San Ramon, CA 

Chuck.Whitaker@bewengi 

neering.com 

Standards, codes, and certification and 

begin related performance modeling 68 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

(a) Without fees 
 

 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

Domestic PV Applications 

Performing Organizations:	 National Renewable Energy Laboratory (NREL) 

Key Technical Contacts:	 John Thornton (NREL) retired 7/06 

Cécile Warner (NREL) 8-9/06, 303-384-6516, cecile_warner@nrel.gov 

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

FY 2006 Budgets:	 $816K (NREL), $30K (SNL) 

Objectives 

•	 Address the markets and applications issues raised in the PV industry Roadmap (NREL). 

•	 Provide a focal point for DOE activities through dissemination of information, raising public 

awareness, and technical facilitation (NREL). 

•	 Support U.S. Department of Agriculture (USDA) Farm Bill Solar Program (NREL and SNL). 

•	 Support development of DOE Systems-Driven Approach (NREL and SNL). 

•	 Continue program-related outreach to Native Americans with interest in solar energy (SNL). 

•	 Extend rural utility support to additional PV systems applications and extend list of accepted 

systems (SNL). 

Accomplishments 

•	 Conducted three consumer workshops at the Denver Western Stock Show with public attendance 

of approximately 380 (NREL). 

•	 Supported the U.S. DOE/USDA joint conference in St. Louis, MO, with the development of an 

exhibit on PV applications in the agriculture sector (NREL) to be staffed by NREL personnel at 

the conference. 

•	 Continued partnership with DOE Rocky Mountain Oilfields Testing Center to test use of PV for oil 

transport in oilfields (NREL). 

•	 Loaned solar electric charging stations to help residents of Kiln, MS, recover from the devastation 

of Hurricane Katrina. The systems provided much-needed power to this town of about 2,000 

people, located 13 miles north of Bay St. Louis, MS, and the Gulf of Mexico (NREL). 

Future Directions 

•	 Continue support of joint DOE/USDA Conference in St. Louis, October 2006 (NREL). 

•	 Conduct expanded consumer workshops, jointly with Xcel Energy, at the Denver Western Stock 

Show (NREL). 

•	 Transition from Domestic Applications project to a broader scope of market transformation, 

supporting DOE in development of plans, review and selection of proposals, and technical 

support in the City Strategic Partnerships and Solar America Showcases projects (NREL). 

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1. Introduction 

The Domestic PV Applications Project, which 

concluded in FY 2006, supported the analytical, 

applications, and market development activities of 

the DOE Photovoltaic Subprogram and the 

development and use of a Systems-Driven 

Approach (SDA). The objective of the project was 

to provide a focal point for DOE activities through 

project development, dissemination of information, 

increasing public awareness, subcontract 

management, and technical assistance. Our work 

was carried out in-house at NREL as well as 

externally with and/or through a wide range of 

federal, state, and local groups. This project 

concluded in 2006. A new project, PV Market 

Transformation, is replacing this project in the 

2007 fiscal year and beyond. 

2. Technical Approach 

During FY 2006, this task addressed some of the 

critical challenges posed by the U.S. PV Industry 

Roadmap—namely, raising the awareness of PV 

in numerous market sectors where significant 

penetration has not yet been attained, developing 

information that effectively conveys the potential of 

PV (and other solar technologies) to both technical 

and non-technical audiences, and providing 

support to organizations to develop standardized 

system specifications and acceptance criteria. We 

also supported several DOE-requested activities, 

including planning for the phase-out of this project 

while ramping up planning to support the Solar 

America Initiative in the area of market 

transformation. 

Task Title FY 2006 

Budget ($K) 

Training, Education, and Technical 

Assistance (NREL) 816 

Domestic Technical Support (SNL) 30 

3. Results and Accomplishments 

3.1 National Renewable Energy Laboratory 

During FY 2006, our highest priority was planning 

for the transition of this project to support the 

DOE’s Solar America Initiative. The new project, 

known as PV Market Transformation, replaces this 

domestic applications activity. 

National Western Stock Show. In January, we 

again conducted workshops (with attendance 

approaching 400) and hosted an exhibit at the 

National Western Stock Show in Denver, CO. 

According to Stock Show staff, more than 600,000 

visitors attended the 16-day event. 

Rocky Mountain Oilfields Testing Center. We 

investigated ways to use PV to enhance the 

production, distribution, and use of traditional fossil 

fuels, such as oil and natural gas. We 

collaborated with the DOE Rocky Mountain 

Oilfields Testing Center (RMOTC) and installed an 

experimental PV-powered, oil-pumping unit in 

operation at the federally owned Teapot Dome oil 

field of Wyoming. The goal of this project is to 

demonstrate a solar-powered, oil-shipping pump 

at this DOE Fossil Energy facility in Casper, WY. 

During the spring and summer of 2006, NREL staff 

facilitated shipping oil reliably through modified 

system design using an alternative pump type. 

Equipment choice and data acquisition issues 

were resolved, and the system is now operating 

without interruption. The overall system design 

and implementation was difficult because it is the 

first of its kind and there was no prior work. 

Fruitful collaborations with experts in a variety of 

fields helped to solve the pumping and dataacquisition challenges. Documentation and 

dissemination of the system design and 

performance will be reported in FY 2007. We 

anticipate this project could be replicated manifold 

by the DOE Fossil program, given the large 

number of similar systems in its network. 

DOE and NREL Special Requests. We supported 

special requests for PV power as requested. For 

example, we provided PV power for the Science 

and Technology Facility dedication at NREL (July 

2006). 

USDA/DOE Conference. DOE and the U.S. 

Department of Agriculture (USDA) hosted a joint 

conference October 10–12, 2006, in St. Louis, 

MO, that focused on elements of President 

George W. Bush's Advanced Energy Initiative, 

specifically biomass, wind, and solar research and 

commercialization. The conference, Advancing 

Renewable Energy: An American Rural 

Renaissance brought together key stakeholders in 

renewable energy to identify major issues 

including partnership opportunities facing decision 

makers both within government and in the private 

sector and advance understanding of the 

opportunities and issues involved in the integration 

of distributed energy production into legacy 

systems. Our team planned, organized, and 

staffed the Solar Energy section of the DOE 

exhibit (see Fig. 1). 

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Fig. 1. Energy Secretary Samuel W. Bodman 

spoke to NREL's Byron Stafford about the 

laboratory's work on solar energy during a tour of 

the Advancing Renewable Energy exhibit hall on 

October 11, 2006. 

Solar Energy and Colorado Golf Course Owners. 

We prepared and presented elements of a 

workshop on “Renewable Energy for Golf Clubs” 

to members of the Colorado Golf Course Owners 

Association (CGCOA). Topics included solar 

energy and energy efficiency. Energy (and the 

closely related topic, water) usage and costs are 

increasingly important to golf clubs for business 

reasons, but also for the stewardship of the natural 

resources that they manage. There are about 

15,000 golf courses (18-hole equivalent) in the 

United States and each course ranges in size from 

150 to 200 acres of total land. The opportunities 

for PV applications in this sector are vast. Prior to 

the workshop, NREL staff toured a course with the 

CGCOA in Denver, CO. We discussed their 

energy concerns, usage, and costs as they relate 

to the golf industry. Not unexpectedly, energy and 

water are critical to maintaining a successful golf 

course and clubhouse. We gave an overview of 

the importance and value of energy efficiency 

measures that the golf course owners could 

implement immediately, especially in their club 

houses, and gave presentations on PV systems 

and a summary of opportunities for golf course 

owners based on NREL’s walkthrough. The 

workshop was well received by the golf course 

owners with requests for another workshop and 

possibly a workshop at their National Golf Course 

Owners Association’s annual conference. 

4. Planned FY 2007 Activities 

This project concluded, based on guidance from 

DOE, at the end of FY 2006. Some existing 

activities, notably technical assistance, will be 

folded into the new PV Market Transformation 

activities that are part of the Solar America 

Initiative, including City Strategic Partnerships and 

Solar America Showcases. We will continue to 

provide technical support to Federal, state, and 

local organizations, such as the Rocky Mountain 

Oilfields Testing Center in Casper, WY. DOE 

Headquarters activities will be supported on 

request. 

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____________________________________________________________________________________ 

 

 

 

 

 

 

 

 

 

____________________________________________________________________________________ 

PV Systems Analysis 

Performing Organizations: National Renewable Energy Laboratory (NREL)

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Robert Margolis (NREL, Primary Contact), 202-646-5053, 

robert_margolis@nrel.gov 

David Mooney (NREL), 303-384-6782, david_mooney@nrel.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 2006 Budgets: $616K (NREL), $150K (SNL) 

Objectives 

•	 Develop the PV components of the Solar Advisor Model including performance, cost, and 

financing modules, allowing detailed system, component, and subcomponent sensitivity studies. 

•	 Develop a user-friendly and intuitive graphical interface for the Solar Advisor Model. 

•	 Use the Solar Advisor Model to support program planning and evaluation. 

•	 Work with private-sector partners (utilities and industry) and Federal agencies to study the key 

component failures, costs and times to repair, and other operation and maintenance issues. 

•	 Document performance (such as kWh production) for various module technologies. 

•	 Determine the overall levelized cost of energy for fielded PV systems in key reference 

applications, and apply projections of technology improvements to determine future-year costs 

and overall targets. 

•	 Develop long-term market penetration projections for 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 Systems-Driven Approach model-development effort. 

•	 Evaluate policies, as well as other factors, that impact the value of solar energy technologies in a 

variety of markets. 

Accomplishments 

•	 Expanded the number of default markets/systems included in the Solar Advisor Model. 

•	 Used the Solar Advisor Model to support the Solar America Initiative (SAI) Technology Pathway 

Partnership (TPP) Federal Opportunity Announcement process. 

•	 Expanded partnered activities on residential PV systems to further refine determinations of 

installation and overall life-cycle cost, system reliability, and system availability. 

•	 Developed functional version of the SolarDS model. 

•	 Completed functional version of Web-based distributed PV cost-benefits clearinghouse. 

•	 Provided technical and analytical support to the Western Governors’ Association Solar Energy 

Task Force. 

Future Directions 

Continue to: 

•	 Develop the PV components of the Solar Advisor Model. 

•	 Exercise the Solar Advisor Model in support of the SAI. 

•	 Focus benchmark activities to directly support the SAI TPPs. 

•	 Work on technology-policy tradeoff studies and value analysis. 

•	 Support the annual Government Performance and Results Act (GRPA) analysis. 

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1. Introduction 

The PV Systems Analysis Task consists of 

systems performance and cost modeling, 

market/value/policy analysis, and benchmarking 

projects. The primary function of the Solar Advisor 

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 related 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 

(LCOE), and system capital and operations and 

maintenance (O&M) costs. The benchmarking 

effort is structured to document the current status 

of these and other key figures of merit. The Solar 

Advisor Model is intended for use by DOE and 

laboratory management and research staff and is 

a critical element in the implementation of the 

Systems-Driven Approach (SDA) to Solar Program 

planning. The model may be used by members of 

the solar industry to inform internal R&D direction 

and to estimate systems cost and performance. 

The analysis portion of the task is structured to 

consider market-penetration models and to 

capture the value of PV systems in various 

markets. During FY 2006, the work under this 

task was focused specifically on supporting the 

implementation of the Solar America Initiative 

(SAI). 

2. Technical Approach 

For the Solar Advisor Model, 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 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 the 

particular user. 

Developing the PV components of the Solar 

Advisor Model, defining its inputs (based on data 

gathered through benchmarking), and carrying out 

detailed analysis with the model has been a 

central focus of the modeling and benchmarking 

areas during FY 2006. 

The analysis team focuses on two main tasks. 

The first is developing long-term marketpenetration 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 

Solar Program’s economic and environmental 

benefits. Here, our emphasis has been on models 

and modeling: using existing models—such as the 

Energy Information Administration’s NEMS, 

MARKAL, and others—to carry out analysis, 

examining the structure of various models and 

providing feedback on how to improve the 

representation of solar technologies to modelers, 

and developing new models such as SolarDS that 

will help meet the needs of the broader SDA 

modeling effort. 

The analysis portion of this task also evaluates 

policies, as well as other factors, that impact the 

value of PV technologies in a variety of markets. 

This task involves using existing models, 

spreadsheets, and other tools. Here, our 

emphasis is on using analytical tools to quantify 

how changing policies, rate structures, system 

designs, and other factors will impact the value of 

solar technologies to consumers, utilities, 

governments, and other players. 

During FY 2006, a key emphasis of the analysis 

team was to identify best practices for implementing 

performance-based incentive structures, in 

particular, in the context of the shifts taking place 

under the California Solar Initiative. While this work 

was aimed at specifically supporting California, it 

developed the framework for broadly informing statelevel policymaking with respect to incentive design. 

In carrying out these projects, we use resources at 

NREL and SNL (described in the table below), as 

well as subcontracts (described in Section 6). 

Task Title FY 2006 

Budget ($K) 

PV Advisor Modeling 180 

PV Market, Value, and Policy 

Analysis 436 

System Reliability and Cost 

Analysis 150 

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3. Results and Accomplishments 

The primary objective of the modeling and 

benchmarking activities during FY 2006 was to 

continue development of the PV portions of the 

Solar Advisor Model, to carry out analyses to 

determine the overall LCOE for fielded PV 

systems in key reference applications, and to 

apply projections of technology improvements to 

determine future-year costs and overall targets. 

The results of this process provided direct support 

to completion of the Multi-Year Program Plan early 

in the year, and implementation of the Solar 

America Initiative later. 

Further refinement to PV system benchmark data 

focused mainly on residential installations and 

costs related to O&M of these systems. This was 

done in partnership with Tucson Electric Power, 

through monitoring and tracking of its installed 

systems. Table 1 lists some key characteristics of 

the residential reference system. The “baseline” 

system configuration uses crystalline silicon 

modules with an efficiency of 13.5% that are 

located in Tucson, AZ. These costs are typical of 

the systems supported by cost sharing under the 

Arizona renewable portfolio standard. The new 

information related to O&M provides a starting 

point for further investigation and for applying the 

Systems-Driven Approach to define and execute 

technology improvements in line with the goal of 

reducing overall levelized energy costs for 

residential systems. 

Table 1. Characteristics of Residential PV
 

System as Reference Application
 

Residential 

Sys Power (kW) 1.2-5.9 

Module Cost ($/Wdc) 3.14 

Inverter ($/Wdc0 1.04 

Installation ($/Wdc) 1.67 

Overhead/Profit ($/Wdc) 1.47 

Installed Price ($/Wdc) 7.32 

O&Ma (%) 1.7b 

a

O&M is listed as percent of initial capital cost per 

annum. 

b

 O&M equates to about $.09/kWh 

As part of the efforts to further develop and refine 

benchmarking data for residential PV systems, a 

set of telephone interviews was conducted with PV 

suppliers and installers to gain insight into two 

areas. The first was to further refine the cost 

categories into which installation procedures and 

balance-of-system (BOS) components can be 

divided. The second was to then populate these 

categories. These insights can further feed the 

Systems-Driven Approach as a basis for the 

development of more detailed cost models and to 

study the relative impacts of technology and 

design changes on overall LCOE for installed 

systems. 

This study of residential grid-tied systems resulted 

in the identification of two areas for technical 

improvement through partnership with PV module 

and BOS manufacturers: 

•	 The accuracy and credibility of Standard Test 

Conditions (STC) ratings for PV modules can 

and should be improved through the 

development of standardized procedures, 

including statistical sampling and 

measurements in the UL process. Through 

implementation of such a process, module 

specification sheets would be a more reliable 

source of information for system design. 

•	 The reliability and accuracy of measurements 

by power electronics equipment (i.e., 

inverters) must be improved. System 

installation costs can be reduced using these 

measurements when combined with intelligent 

reporting capability and wireless technology. 

In partnership with a major Arizona electric utility, 

an initial cost study was conducted of a one-axis 

tracking system, comparing tradeoffs between 

crystalline and thin-film module technologies. 

Cost categories included component and 

installation cost and the tradeoffs related to 

differences in efficiency and BOS components. 

For the case based on the most likely cost 

structure in this study, thin-film system cost is 

approximately 13% higher than for the crystalline 

silicon baseline system cost of $5.15/Wdc. 

4. Planned FY 2007 Activities 

•	 Continue to develop a suite of analysis, 

modeling, and benchmarking tools that are 

needed for the Solar Energy Technologies 

Program’s planning, technology evaluation, 

and decision-making (e.g., stage gate). 

•	 Partner with the U.S. PV and CSP industries 

to improve and advance systems design tools 

development, component and systems 

performance database development, systems 

performance prediction tools, and market 

penetration models. 

•	 Exercise the Solar Advisor Model in support of 

the Solar America Initiative. 

•	 Focus benchmark activities to directly support 

the SAI Technology Pathway Partnerships. 

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•	 Take full advantage of relationships and 

access to information offered by the 

monitoring of selected SAI Technical Pathway 

Partnerships. 

•	 Fully implement Web-based distributed PV 

cost-benefits clearinghouse. 

•	 Complete beta version of SolarDS model for 

external use and feedback. 

•	 Continue to support the GRPA process. 

5. Major FY 2006 Publications 

Denholm, Paul, and Robert M. Margolis, “Very 

Large-Scale Deployment of Grid-Connected Solar 

Photovoltaics in the United States: Challenges and 

Opportunities,” paper presented at Solar 2006, 

Denver, CO, July 9–13, 2006 

Denholm, Paul, Ken Zweibel, and Robert M. 

Margolis, “Tackling Climate Change in the U.S.: 

The Potential Contribution from Solar 

Photovoltaics,” paper presented at Solar 2006, 

Denver, CO, July 9–13, 2006. 

Margolis, Robert M., Richard Mitchell, and Ken 

Zweibel, “Lessons Learned from the Photovoltaic 

Manufacturing Technology/PV Manufacturing R&D 

and Thin-Film PV Partnership Projects. Golden, 

CO: National Renewable Energy Laboratory, 

NREL Technical Report (NREL/TP-520-39780). 

September, 2006. 

Margolis, M. Robert and Jarett Zuboy,. 

“Nontechnical Barriers to Solar Energy Use: 

Review of Recent Literature.” Golden, CO: 

National Renewable Energy Laboratory. NREL 

Technical Report (NREL/TP-520-40116), 

September, 2006. 

Moore, Larry, Harold Post, Tom Hansen, Terry 

Mysak, “Residential Photovoltaic System 

Experience at Tucson Electric Power,” internal 

draft. 

Perez, Richard, Robert Margolis, Marek Kmiecik, 

and Marc Perez, “Update: Effective Load Carrying 

Capability of Photovoltaics in the United States,” 

paper presented at Solar 2006, Denver, CO, July 

9–13, 2006. 

U.S. Department of Energy, Solar Energy 

Technologies Program Multi-Year Program Plan 

2007–2011, DOE Office of Energy Efficiency and 

Renewable Energy, Washington, DC. January, 

2006. 

Wiser, Ryan, Mark Bolinger, Peter Clappers, and 

Robert Margolis, “Letting the Sun Shine on Solar 

Costs: An Empirical Investigation of Photovoltaic 

Cost Trends in California.” Golden, CO: National 

Renewable Energy Laboratory, NREL Technical 

Report (NREL/TP-620-39300), January, 2006. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2006 

($K) 

Clean Power Research 

Thomas Hoff 

Napa, CA 

tomhoff@clean-power.com 

Designing Incentives for CustomerOwned PV Systems 100 

Lawrence Berkeley 

National Laboratories 

Ryan Wiser 

Berkeley, CA 

RHWiser@lbl.gov 

Providing Technical Assistance to 

the CPUC During the Design and 

Implementation of the California 

Solar Initiative 

100 

SENTECH, Inc. 

Jonathan Hurwitch 

Bethesda, MD 

jwitch@sentech.org 

Case Study of a PV-Covered 

Parking Installation 5 

MRG & Associates 

Marshall Goldberg 

Nevada City, CA 

mrgassociates@earthlink.net 

Development of Jobs and Economic 

Development Impact Models 12 

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____________________________________________________________________________________ 

 

Building-Integrated Photovoltaics 

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 2006 Budget:	 $2,260 K (NREL) 

Objectives 

•	 Conduct the next Solar Decathlon university competition of 100% solar-powered homes, which 

demonstrate building-integrated photovoltaic (BIPV) and solar technologies in marketable 

residential applications. 

•	 Support deployment of BIPV technologies through subcontracted R&D projects in BIPV and 

through development of a greater understanding of BIPV system performance. 

•	 Accelerate adoption of BIPV in new residential and commercial construction through technical 

assistance and successful collaborative partnerships. 

Accomplishments 

•	 Concluded the implementation of the 2005 Solar Decathlon university competition, releasing the 

final regulations, solidifying sponsors, supporting teams, scoring, monitoring, and carrying out all 

aspects of the event. (October 2005) 

•	 Held “Building Industry Day” for builders at the Solar Decathlon. (October 2005) 

•	 Developed and released a solicitation for the 2007 Solar Decathlon event. (October 2005) 

•	 Selected teams for the 2007 Solar Decathlon and launched the activities leading toward 

execution of the 2007 event. Awarded 2-year, $100,000 contracts to these 20 teams. (September 

2006) 

•	 Published the technical report, Solar Decathlon 2005: The Event in Review. (May 2006) 

Future Directions 

•	 Conduct the 2007 Solar Decathlon in the first quarter, FY 2008, and release a solicitation for the 

2009 event. 

•	 Monitor and guide the development of BIPV through the subcontracted university programs. 

•	 Assess performance of selected, occupied former Solar Decathlon entries to assess longer-term 

implications of PV in buildings. 

•	 Continue and expand productive interactions with the building industry. 

1. Introduction 

The Building-Integrated PV (BIPV) Project fosters 

the widespread acceptance of PV-integrated 

buildings by overcoming technical and commercial 

barriers and by facilitating the integration of 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 21st 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 homes 

and businesses that demonstrate buildingintegrated PV and solar technologies in 

marketable applications and partnerships that 

build on successes. There are two interrelated 

activities within this overall effort, which are the 

Solar Decathlon and R&D on PV in buildings. 

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2.1 Conduct the 2005 Solar Decathlon 

The Solar Decathlon is an intercollegiate 

competition to design, build, and operate the most 

attractive and energy-efficient solar-powered 

home. Eighteen teams of students from the United 

States, Canada, and Spain competed in the 2005 

event. Teams were selected through a competitive 

procurement in 2003 and worked on their projects 

over the intervening 2 years under our supervision 

and guidance. They transported their houses to 

the National Mall in Washington, D.C., where they 

built a “solar village” and opened their homes to 

the visiting public from October 7 to October 16, 

2005. They competed against one another in ten 

contests that tested the teams’ abilities to produce 

electricity and hot water from solar panels to 

perform all the functions of home—from turning on 

the lights to cooking, washing clothes and dishes, 

powering home electronics, and maintaining a 

comfortable temperature. These homes were also 

required to provide the power for an electric car. In 

addition to the energy-related contests, each team 

was judged on its home's architecture and 

livability. And expert homebuilders evaluated each 

home’s “build-ability” (ease of construction and 

replication of design). The teams provided 

documentation about their homes’ designs and 

communicated about their homes 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 its subcontractors. Some 

contests were scored by measuring performance, 

and others were scored by judges representing 

expertise in appropriate fields. For more 

information, visit the Solar Decathlon Web site 

(www.solardecathlon.org). The primary sponsors 

of the 2005 Solar Decathlon were 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, and private-sector 

sponsors BP, the DIY Network, and Sprint-Nextel. 

2.2 Develop and Release Solicitation for 2007 

Solar Decathlon Event 

While preparing for the 2005 event, the concept 

for expanded BIPV R&D at the universities 

participating in the 2007 event evolved, 

culminating in the development of a solicitation for 

the 2007 event (prepared by NREL), which was 

announced by the Secretary of Energy in early 

October at the start of the 2005 event. New to this 

solicitation, each winning university proposal was 

set to receive $100K in research funding (over two 

years) to support the innovative development of 

BIPV technology in its entry 

2.3 Plan Post-Decathlon Monitoring Program 

A PV building benchmarking effort to assess longterm performance of occupied Solar Decathlon 

homes after the competition was developed during 

FY 2006. A comprehensive monitoring and 

instrumentation plan, together with a building 

simulation and modeling effort, was conceived, 

with the goal of understanding and improving the 

design and performance of BIPV homes. 

Task Title FY 2006 

Budget ($K) 

Solar Decathlon (NREL) 2,160* 

PV in Buildings R&D 100 

* Includes activities that are reported in the Communications and Outreach section of the annual report. 

3. Results and Accomplishments 

3.1 Major Accomplishment: Solar Decathlon 2005 

During FY 2006, we successfully carried out the 

2005 Solar Decathlon, held September 29– 

October 19, 2005 on the National Mall in 

Washington, D.C. Activities included scoring for 

the 10 contests; expert judging for contest such as 

dwelling, architecture (see Fig. 1), engineering, 

Web sites, and house tours; 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 safe conduct of the 

entire event. We managed crowds of more than 

100,000 visitors to the Solar Decathlon and a 

massive media interest to view the future of solar 

energy and the next generation of solar 

practitioners and solar homes. 

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Fig. 1. At the 2005 Solar Decathlon, the 

Architecture Jurors debated the merits of each 

entry, including the pictured New York Institute of 

Technology home. 

3.2 Major Accomplishment: Solicit and Select 

Teams for the 2007 Solar Decathlon and Launch 

the Activities Leading toward Execution of the 

2007 Event 

We selected 20 teams (from proposal responses 

to a solicitation) to participate in the 2007 Solar 

Decathlon (see Section 6 for a list). In the 2005 

event, teams were encouraged to use buildingintegrated PV systems, but were not explicitly 

scored on the degree to which they implemented 

BIPV, except as evaluated by the aesthetic 

assessment of the Architecture Jury. Because 

BIPV development is a major goal of the DOE 

Solar Program, in the upcoming 2007 Solar 

Decathlon, the teams will be more explicitly scored 

on their ability to innovate in BIPV applications and 

the execution of cost-effective BIPV techniques for 

their entries. 

Milestones Supported by DOE Funding 

Milestone or 

Deliverable Due Date Status 

Carry out Solar 

Decathlon 2005 event 

on the National Mall in 

Washington, D.C., 

beginning September 

29, 2005. 

11/1/05 Complete 

Announce participants 

in the 2007 event. 1/31/06 Complete 

4. Planned FY 2007 Activities 

•	 Convene a workshop for the 2007 Solar 

Decathlon Teams in the first quarter, FY 2007. 

•	 Continue the activities leading toward 

execution of the 2007 Solar Decathlon event. 

•	 Monitor and guide the development of BIPV 

through the subcontracted university programs 

and through evaluation of long-term 

performance of selected entries. 

•	 Develop a solicitation for teams and for 

subcontracted production of the 2009 Solar 

Decathlon. 

5. Major FY 2006 Publications 

Cécile L. Warner and Michael R. Wassmer, “Solar 

Decathlon 2005—PV System Strategies and 

Results.” Proc. WCPEC, May 2006, Waikoloa, HI, 

(2006). 

Susan Moon, Ruby Nahan, Cécile Warner, and 

Michael Wassmer, Solar Decathlon 2005: The 

Event in Review, 62 pp., DOE/GO-102006-2328 

(2006). 

U.S. DOE, Solar Decathlon Web Site, 

www.solardecathlon.org. 

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6. University and Industry Partners 

The following organizations partnered in the project’s activities during FY 2006. Twenty teams were 

selected in FY 2006 to compete in the 2007 Solar Decathlon. DOE will award the selected teams 

$100,000 over two years to support the Solar Decathlon's research goal of reducing the cost of solarpowered homes and advancing solar technology. In most cases, this amount is less than half of the funds 

needed to mount a Solar Decathlon entry. Team members dedicate considerable time, energy, and 

ingenuity to enlisting community and industry support for the remaining funding. 

Organization/ 

Principal Investigator 

or Contact 

Location/e-mail Description/Title of Research Activity FY 2006 

($K) 

Colorado Code 

Consulting, LLC 

Thomas Meyers 

Berthoud, CO 

codeconsultant@gmail.com 

Complete three plan reviews of 20 sets of 

drawings and specifications and perform 

20 on-site building inspections of the 

competition houses after they are installed 

on the National Mall in fall 2007, for the 

Solar Decathlon competition 

70 

Carnegie Mellon 

University 

Stephen R. Lee 

Pittsburgh, PA 

stevelee@cmu.edu 2007 Solar Decathlon team 50 

Cornell University 

Zellman Warhaft 

Ithaca, NY 

zw16@cornell.edu 2007 Solar Decathlon team 50 

Georgia Institute of 

Technology 

Chris Jarrett 

Atlanta, GA 

chris.jarrett@coa.gatech.edu 2007 Solar Decathlon team 50 

Kansas State University 

R. Todd Gabbard 

Manhattan, KS 

rtodd@ksu.edu 2007 Solar Decathlon team 50 

Lawrence Technological 

University 

Philip Plowright 

Southfield, MI 

pplowright@ltu.edu 2007 Solar Decathlon team 50 

Massachusetts Institute 

of Technology 

Kurt Keville 

Cambridge, MA 

kkeville@mit.edu 2007 Solar Decathlon team 50 

New York Institute of 

Technology 

Thomas Rochon 

New York, NY 

thomas@thomasrochon.com 2007 Solar Decathlon team 50 

Pennsylvania State 

University 

David R. Riley 

University Park, PA 

driley@engr.psu.edu 2007 Solar Decathlon team 50 

Santa Clara University 

Jorge E. Gonzalez 

Santa Clara, CA 

jgonzalezcruz@scu.edu 2007 Solar Decathlon team 50 

Team Montréal (École 

de Technologie 

Supérieure, Université 

de Montréal, McGill 

University) 

Hughes Rivard 

Montréal, Quebec, Canada 

hughes.rivard@etsmtl.ca 2007 Solar Decathlon team 50 

Technische Universität 

Darmstadt 

Manfred Hegger 

Darmstadt, Germany 

fg@ee.tu-darmstadt.de 2007 Solar Decathlon team 50 

Texas A&M University 

Pliny Fisk 

College Station, TX 

pfisk@cmpbs.org 2007 Solar Decathlon team 50 

Universidad Politécnica 

de Madrid 

José Manuel Paéz 

Borrallo 

Madrid, Spain 

upm_faculty_contact@solar 

decathlon.upm.es 

2007 Solar Decathlon team 50 

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Organization/ 

Principal Investigator 

or Contact 

Location/e-mail Description/Title of Research Activity FY 2006 

($K) 

Universidad de Puerto 

Rico 

Rafael A. OlivenciaMartínez 

Mayagüez, Puerto Rico 

solar@uprm.edu 2007 Solar Decathlon team 50 

University of Colorado 

Michael Brandemuehl 

Boulder, CO 

michael.brandemuehl@ 

colorado.edu 

2007 Solar Decathlon team 50 

University of Cincinnati 

Dale L. Murray 

Cincinnati, OH 

dale.murray@uc.edu 2007 Solar Decathlon team 50 

University of Illinois 

Ty Newell 

Urbana, IL 

tynewell@uiuc.edu 2007 Solar Decathlon team 50 

University of Maryland 

Amy Gardner 

College Park, MD 

turbine@umd.edu 2007 Solar Decathlon team 50 

University of Missouri -

Rolla 

Stuart W. Baur 

Rolla, MO 

baur@umr.edu 2007 Solar Decathlon team 50 

University of Texas at 

Austin 

Samantha Randall 

Austin, TX 

samrandall@mail.utexas.edu 2007 Solar Decathlon team 50 

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____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

 

 

 

Million Solar Roofs Initiative 

Performing Organizations: DOE Headquarters and Regional Offices (ROs) 

National Renewable Energy Laboratory (NREL)

 Sandia National Laboratories (SNL)

 Interstate Renewable Energy Council (IREC)

 National Energy Technology Laboratory (NETL)
 

Key Technical Contacts:	 Carol Tombari (NREL, Primary Contact), carol_tombari@nrel.gov 

John Thornton (NREL, Technical Contact); Charles Hanley (SNL); 

Denise Riggi (DOE/NETL) 

DOE HQ Technology Manager:	 Glenn Strahs, 202-586-2305, glenn.strahs@ee.doe.gov 

FY 2006 Budgets:	 $250K (NREL), $100K (SNL), $200K (DOE/ROs), $300K (DOE/IREC) 

Objectives 

•	 Facilitate the reduction of institutional barriers to marketplace adoption of Million Solar Roofs 

(MSR) technologies (PV, solar domestic water, pool heating, and solar thermal heating). 

•	 Help to develop local and regional markets for solar technologies by working with communities to 

identify and encourage new applications. 

Accomplishments 

•	 Closed out program. Regional DOE Offices closed. 

•	 Published final report, held wrap-up meeting in fall 2006 at Solar Electric Power Association 

Conference. 

•	 Provided limited engineering support, economic analysis, and directed market studies for MSR 

Partnerships. Segue Consulting, NREL’s subcontractor, responded to many technical assistance 

e-mail requests from the partnerships and prepared analyses ranging from 2–20 pages. 

Future Directions 

•	 None. Project concluded in FY 2006, per DOE new priority direction. 

1. Introduction 

The objective of the Million Solar Roofs Initiative 

was to facilitate the installation of solar energy 

systems (PV, solar domestic water, pool heating, 

and solar thermal heating) on all types of buildings 

throughout the United States. The initiative 

supported the development of local and regional 

markets for solar technologies by working with 

states and local communities to address and 

remove institutional barriers. 

In addition to helping create markets, MSR has 

provided the Solar Program with critical feedback 

on performance and consumer preferences. 

2. Technical Approach 

To achieve its objective, MSR worked through a 

nationwide network of officially designated 

partnerships and their local partners. Businesses, 

utilities, government agencies, and/or advocacy 

groups interested in official partnership status 

were required to commit to facilitating the 

installation of a specified number of “solar roofs” 

by 2010. These partnerships used a variety of 

means to build markets in their local communities, 

including: identifying and addressing local barriers; 

using solar technologies to meet important public 

policy goals; leveraging state and local incentives 

for solar; and educating the next generation of 

consumers and their parents. 

3. Results and Accomplishments 

Investing in solar equipment directly would have 

required a large amount of funding to make an 

impact, so MSR invested in people instead. 

Between 1997 and 2005, 94 coalitions across the 

country signed on with DOE as official MSR 

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partnerships. These partnerships comprised 971 

private sector firms, electric utilities, 

builder/developers, nonprofit organizations, and 

governmental entities—all voluntarily committed to 

facilitating the installation of a specified number of 

“solar roofs.” This fundamental metric, embedded 

in the program name, gave the program an 

outcome-oriented focus. 

Key areas where MSR made significant 

contributions were in addressing barriers to 

technology acceptance and market expansion 

efforts, and developing best practices examples 

for market transformation. 

The national network of local partnerships imbued 

the program with a grassroots nature and 

exemplified successful public-private collaboration. 

DOE invested 68% of its program funding in 

competitively awarded grants to these 

partnerships, which focused on reducing barriers 

to technology acceptance and on expanding the 

market for solar technologies. 

The remaining funds supported the participation of 

the Interstate Renewable Energy Council (IREC), 

technical experts, and national laboratories in the 

core program team, providing expert 

underpinnings for the program, as well as a built-in 

feedback mechanism from the marketplace to the 

R&D community and solar industry. 

When the program concluded, the Federal 

government’s investment of $16 million had 

leveraged roughly $7.1 million in cash; it also 

leveraged in-kind resources and incentive 

programs throughout the country. This synergy 

has contributed to the following outcomes: 

•	 Installation of the equivalent of more than 

377,000 solar water heating, photovoltaic 

(PV), and solar pool heating systems 

•	 Installation of 200 MW of grid-connected PV 

capacity and 200 MWth of solar water heating 

capacity 

•	 Dramatic growth in PV technology 

acceptance, from 8% of solar installations in 

1997 to 41% in 2005 

•	 Economic and environmental benefits that 

resulted from grid-connected PV installed 

between 1997 and 2005, including: 

o	 Health benefit savings of $90 million 

o Decreased CO2 emissions of 3.3 million 

tons 

o	 Cumulative GNP increase of $1.6−$2.6 

billion, depending on installed cost (range 

of $8–$10/watt) 

o	 Increase in job-years of 23,000 to 31,000. 

•	 MSR conducted more than 26 peer exchange 

workshops, attended by more than 650 

people. More than 79% of MSR’s partners 

attended at least one workshop. Between 

2003 and 2005, some 910 people participated 

in 10 interactive telephone seminars. 

In addition, MSR efforts contributed to the body of 

knowledge about best practices for facilitating 

market transformation and technology diffusion. 

Task Title 

FY 2006 

Budget 

($K) 

MSR Project Management 

(DOE/RO) 200 

Technical Assistance through 

NREL 250 

Performance Coordination with 

SNL 100 

Communication and Outreach 

Support through IREC 300 

4. Planned FY 2007 Activities 

•	 None. Project concluded. 

5. Major FY 2006 Publications 

G. Strahs, C. Tombari, “Laying the Foundation for 

a Solar America: the Million Solar Roofs Initiative, 

Final Report” 43 pp.; NREL Report BK-710-

40483 (October 2006). 

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6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity FY 2006 ($K) 

Segue Consulting 

Christy Herig 

Redington Shores, FL 

cherig@tampabay.rr.com 

Economic, regulatory, financial, and 

value analysis (individualized response 

to technical assistance requests; 

generic analysis and document 

production) 

106 

Interstate Renewable 

Energy Council 

Jane Weissman 

Latham, NY 

jane@irecusa.org 

Communication and outreach activities 

aimed at the 91 MSR Partnerships and 

their participating members 

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Regional Experiment Stations 

Performing Organizations: Sandia National Laboratories (SNL) 

DOE Golden Field Office (DOE/GO) 

Key Technical Contacts:	 Michael Quintana (SNL), 505-844-0574, maquint@sandia.gov 

Glenn Doyle (DOE/GO), 303-275-4706, glenn.doyle@go.doe.gov 

DOE HQ Technology Manager:	 Dan Ton, 202-587-4618, dan.ton@ee.doe.gov 

FY 2006 Budget:	 $1,750K (DOE/GO) 

Objectives 

•	 Team with the national laboratories to meet Solar Program Annual Operating Plan objectives and 

milestones. 

•	 Position photovoltaics (PV) systems and technologies to become a cost-effective, major source of 

energy for the United States. 

•	 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/or support 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 of the Solar 

America Initiative (SAI). 

Accomplishments 

•	 Transitioned former Regional Experiment Station (RES) annual earmark-funded contract to a 

three-year, program-funded, and cost-shared contract through DOE/GO. 

•	 Continued long-term operation and monitoring of five inverters (Fronius, PV Powered, SMA, 

Solectria, and Xantrex) at each RES. 

•	 Southeast Regional Experiment Station (SERES) and Southwest Regional Experiment Station 

(SWRES): Developed the first implementation plan for the Photovoltaic Systems Assistance 

Center (PVSAC). Identified nine outstanding board members and held the first PVSAC Board of 

Advisors meeting for additional planning and guidance. 

•	 SERES and SWRES: Participated in Federal Opportunity Announcement (FOA) Technical 

Committee to determine accuracy of all data submitted in SAI Technology Pathway Partnership 

(TPP) proposals. 

•	 SWRES: Assisted the town of Woodside, CA, in developing and implementing a standardized 

process for permitting of PV plans. 

•	 SERES and SWRES: Continued work with eight countries through the International Energy 

Agency Photovoltaic Power Systems Programme (IEA PVPS) Task 2 to expand the 

comprehensive PV database containing performance and economic data for selected countries, 

including the United States, Germany, and Japan. 

•	 SWRES: Developed industry survey form for use by Test and Evaluation Team in assessing 

industry needs, existing data, and level of support required. 

•	 SWRES: Participated in final review for the California Energy Commission $35M PIER
 

Commonwealth Energy Renewables Resources Program.
 

•	 SERES: Completed more than 200 PV System Design Reviews for the U.S. Department of 

Agriculture (USDA), as part of its Renewable Energy Program, and for the State of Florida. 

•	 SERES: Completed four weeklong training programs for PV Installers. About 80 people were 

trained this year. 

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•	 Provided design reviews and acceptance testing for PV systems operated by the U.S. Virgin 

Islands Energy Office to encourage the Water and Power Authority to permit interconnection of 

PV systems to the grid. 

•	 SERES: Continued detailed monitoring of grid-connected PV systems to the utility in Florida and 

other states. 

•	 SERES: Continue testing the performance of commercially available PV modules to compare our 

results with those from industry. 

•	 SERES: Worked with several modular homebuilders in the design of PV systems. One such 

system will be on display at the International Builders Show in Orlando, FL. 

Future Directions 

•	 Support DOE/GO administration of the RES cooperative agreements by implementing technical 

activities to meet R&D emphases, assuring that milestones align with program priorities and that 

deliverables are met on time. 

•	 Present the PV System Assistance Center function that was a hallmark of the SNL/RES 

programs of the 1990s and transition this into a nationwide resource. 

•	 Develop advanced PV designs for integrated manufacturing and deployment. 

•	 Conduct a continuous review of activities to improve alignment with the Systems-Driven 

Approach. 

•	 Continue to evolve priorities to remove barriers to PV system deployments in targeted markets, 

targeted regions, and nationwide. 

•	 Continue monitoring the performance of new PV systems entering the market, with a focus on 

evolving PV products and high-value/profile applications such as disaster shelters. 

1. Introduction 

The Southeast and Southwest Regional 

Experiment Stations (SERES and SWRES, 

respectively) are partners in the DOE Solar 

Program. Each RES has a university affiliation 

(University of Central Florida for SERES and New 

Mexico State University for SWRES) and 

university-level capabilities, which have been 

developed over the years to provide systems-level 

R&D for DOE, the U.S. PV industry, other 

government agencies, and PV consumers. The 

RES work is aligned with activities conducted in 

the Technology Development and Advanced 

Materials and Devices portion of the DOE PV 

Subprogram. 

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 

Systems-Driven Approach in pursuit of targets 

specified by the DOE Solar Program Multi-Year 

Program Plan. 

The Regional Experiment Stations have 

contributed to the DOE National Photovoltaic 

Program for two decades. This work is integrated 

into DOE’s Annual Photovoltaic Program plan and 

is highly collaborative. Throughout the years, RES 

support has been an integral part of program 

projects, such as: 

1.	 Module Reliability R&D 

2.	 Inverter and Balance-of-System Development 

3.	 PV Systems Engineering 

4.	 Domestic PV Applications 

5.	 System Evaluation and Optimization 

6. PV System Analysis 

7.	 Education and codes and standards 

development. 

Collaborations with SNL, NREL, the National 

Center for Photovoltaics (NCPV) R&D partners, 

and industry counterparts are focused on reducing 

systems costs, improving systems reliability, 

improving system performance, and removing 

barriers to deployment, thereby promoting market 

growth. 

2. Technical Approach 

Work conducted by the Regional Experiment 

Stations 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 

high volume of requests from the PV industry, as 

well as the alignment to an evolving U.S. PV 

Photovoltaic R&D

Technology Development

104
 

 

 

 

 

 

 

 

 

 

 

 

 

Photovoltaic 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 PVSAC is a virtual laboratory comprising 

engineers and staff from both of the RES. The 

objective of the PVSAC is to become a national 

one-stop resource for public policy support, design 

reviews, specialized training and training 

materials, and technical field-support activities. In 

this way, the PVSAC will be a major gateway for 

technical education, training, and outreach to the 

U.S. PV community. 

The PVSAC will impanel a board of advisors, with 

whom they will develop a comprehensive strategic 

plan 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. 

2.2 Infrastructure Development 

This activity 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, which has 

been addressed consistently by the RES staff. 

Activities began by providing training to interested 

parties and have evolved to the creation and 

establishment of a National Installer Certification 

Program, an independent activity that the RES's 

were instrumental in creating. Similarly, training of 

inspectors and installers is now evolving to a 

system of “training the trainers,” providing an 

opportunity to reach a greater audience while 

minimizing 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 recognized 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 in order to assure quality and 

safety. The RES’s proactive approach provides 

the opportunity to guide development of codes and 

standards that assure performance, quality, and 

safety without creating a cost burden for the 

industry. Certification of hardware creates and 

applies a uniform set of standards in a 

recognizable format that instills consumer 

confidence. Certification is also the basis for 

assuring optimal awards from government 

incentive programs. 

2.3 Long-Term Component Testing 

The RES's provide unique environments for 

environmentally stressing PV components. 

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 begun to study 

the long-term performance of inverters in field-like 

outdoor configurations. Additional activities 

include placing the inverters in a distributedgeneration scenario to address issues associated 

with controls and generator interactions. Both of 

these activities are complementary to SNL’s 

baseline tests, which establish initial component 

performance parameters 

3. Results and Accomplishments 

•	 Trained more than 300 code officials in oneday workshops in New York, California, 

Colorado, Minnesota, and Texas. 

•	 Performed complete assessment of utilityscale PV power plants in Tucson, AZ, and San 

Mateo, CA, for performance, reliability, and 

cost benchmarks. 

•	 John Wiles (SWRES) served as Secretary of 

the PV Industry Forum; drafted recommended 

changes to the 2008 National Electrical Code. 

•	 SWRES and SERES: Participated in FOA 

Technical Committee review of all data 

submitted in TPP SAI proposals. 

•	 SWRES: Provided design reviews to dozens 

of major PV system developers (e.g., 

PowerLight, RWE Schott Solar) and 

purchasers (e.g., utilities, Federal agencies) 

for code compliance and proper design. 

•	 SERES: Provided design reviews for more 

than 200 PV systems for both the USDA and 

the State of Florida. This includes systems 

using equipment from companies such as 

Solarworld, Solar Integrated Technologies, 

Beacon Power, SMA America, Sharp, Xantrex, 

and Sunwize. 

•	 SERES: Provided module performance testing 

for eight modules from companies such as 

GE, Sharp, Sanyo, and Sunwize. 

•	 SWRES and SERES: Provided testing and 

analysis of c-Si and thin-film modules in 

105

Photovoltaic R&D

Technology Development
 

 

 

 

 

 

 

 

 

support of the Module Long-Term Exposure 

Program. 

•	 SWRES: Begin process of obtaining American 

Association of Laboratory Accreditation 

(A2LA) for PV system testing laboratories in 

accordance with ISO 17025. 

•	 SERES: Continued our accreditation from the 

American Association of Laboratory 

Accreditation and Powermark to certify both 

completely integrated PV systems and PV 

module performance. 

4. Planned FY 2007 Activities 

RES projects will focus on the following tasks: 

•	 Design and implementation of the PV Systems 

Assistance Center Web pages 

•	 PV systems analysis and engineering 

•	 Codes and standards development 

•	 R&D of advanced system concepts. 

Expected results for FY 2007 include the following: 

• Continuing update of 2006 benchmarking, 

including evaluation of first-year Technical 

Improvement Opportunities for the Solar 

Program. 

•	 Continued work to resolve codes and 

standards differences between the European 

Union and the United States. 

•	 Gather inverter long-term performance data 

and participate with SNL in the creation of a 

well-defined and documented inverter model. 

•	 Refinement of the PV Systems Assistance 

Center and introduction to the U.S. PV 

community. PVSAC will work to provide 

outreach, training, support, and Web 

development to get the maximum system 

information into the hands of the designers, 

installers, and policy makers who require it. 

•	 Continued work in PV module performance 

testing and design review work. 

•	 Maintain ISO 17025 accreditation in PV 

module performance testing and PV system 

design review. 

5.	 Major FY 2006 Publications 

A. Rosenthal, SMUD Performance Index Program 

and Results–Final Report, Submitted, March 2006. 

J. Wiles, "Recent Changes in the National 

Electrical Code," Presented at the DOE Annual 

Program Review, Q4 2005. 

A. Rosenthal, Salt River Project Performance 

Index Program User’s Manual, Submitted, May 

2006. 

J. Wiles, “Making the Utility Connection,” Home 

Power Magazine, March 2006. 

J. Wiles, “Working with Inspectors,” Home Power 

Magazine, February 2006. 

J. Wiles, “Back to the Grid,” International 

Association of Electrical Inspector News, January 

2006. 

J. Wiles, "Plan Check," International Association of 

Electrical Inspector News, March 2006. 

K. Lynn, W. Wilson, “Early Results from the LongTerm Testing of Inverters,” Proceedings of ASME 

International Solar Energy Conference, July 8–13, 

2006, Denver, CO. 

K. Lynn, J. Szaro, W. Wilson, M. Healey, “A 

Review of the PV System Performance and LifeCycle Cost for the SunSmart Schools Program,” 

Proceedings of ASME International Solar Energy 

Conference, July 8–13, 2006, Denver, CO. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2006 

($K) 

Florida Solar Energy Center 

Kevin Lynn 

Cocoa, FL 

klynn@fsec.ucf.edu PV System Research 875 

Southwest Technology 

Development Institute 

Andrew Rosenthal 

Las Cruces, NM 

arosenth@nmsu.edu PV System Research 875 

Photovoltaic R&D

Technology Development

106
 

Solar Thermal R&D Subprogram Overview 

Frank (Tex) Wilkins, Team Leader, Solar Thermal R&D 

The Solar Thermal Subprogram comprises two activities: Concentrating Solar Power (CSP) and 

Solar Heating and Lighting (SH&L). CSP technologies use mirrors to concentrate the sun’s 

energy up to 10,000 times sunlight to power conventional turbines, heat engines, or other 

converters to generate electricity. Energy from CSP systems is high-value renewable power, 

because energy storage and hybrid designs allow it to be provided when most needed. This is 

particularly important to utilities that need to increase the amount of power available to them 

during periods of peak demand. The SH&L research activity develops solar technologies that 

provide hot water for residential and commercial buildings as well as hybrid solar lighting for 

commercial buildings. Reducing the cost of these two technologies is important to the goal of a 

reasonably priced zero energy building. R&D sponsored by the Solar Thermal Subprogram is 

done in collaboration with industry and university partners. 

Goals and Objectives 

Concentrating Solar Power 

CSP systems currently offer solar electricity at about 12¢–14¢/kWh with systems ranging in size 

from kilowatt-scale to multi-megawatt power plants. A study by the Western Governors’ 

Association Solar Task Force projected that large CSP systems will be able to produce power at 

about 5.5¢/kWh with continued R&D and the deployment of 4,000 MW. Our 2012 goal is to 

reduce the cost of energy from CSP technology to 9¢–11¢/kWh. The 2020 goal is 5¢–7¢/kWh 

with up to 12 hours of thermal storage. This will be done through R&D carried out by the national 

laboratories and industry combined with the establishment of CSP plants deployed by utilities and 

their industry partners. The primary objectives for FY 2006 were to (1) assist industry in lowering 

the cost and improving the performance of trough and dish technologies and (2) encourage 

southwestern utilities to consider CSP as a way of fulfilling their renewable portfolio standard 

requirements by using the region’s most abundant renewable resource: solar energy. 

Solar Heating and Lighting 

SH&L research emphasizes the development of low-cost, polymer-based solar water heaters, 

which have the potential to cut the cost of today’s solar water heating (8¢/kWh) to 4.5¢/kWh. The 

objectives for FY 2006 were to (1) complete the evaluation of prototype units placed at locations 

throughout the nonfreezing regions of the country and (2) begin work on the design of solar water 

heaters applicable to freezing climates. Budget issues, however, precluded the completion of the 

first objective and led to the postponement of the second. The primary objectives of hybrid solar 

lighting development were to (1) improve the design of the system and (2) install prototypes at 

selected commercial locations and evaluate their performance. 

Results and Accomplishments 

Concentrating Solar Power 

The most significant CSP events during FY 2006 were the initial operation of Arizona Public 

Service’s 1-MW trough plant and the beginning of construction of a 64-MW trough plant in 

Nevada. The Nevada project, called Nevada Solar One, is expected to become operational in 

2007. These are the first commercial CSP plants built in the United States since 1991. Both are 

Solargenix projects and both used a solar collector developed collaboratively with the DOE Solar 

Program. The Solar Program also assisted industry in making existing projects more efficient. 

Methods were developed to evaluate the alignment of mirrors on collectors and assess the 

performance of thermal receivers in a solar trough field. NREL, working with FPL Energy, 

identified that a loss in efficiency of trough receivers was caused by hydrogen emanating from the 

heat transfer fluid and migrating through the receiver pipe into the glass jacket. Hydrogen in the 

107 Solar Thermal R&D
glass jacket was found to increase the thermal losses by a factor of four. Work is now under way 

to solve the problem. 

During FY 2005, Stirling Energy Systems (SES) built, entirely with its own funding, a six-dish 

150-kW power plant at the National Solar Thermal Test Facility at Sandia National Laboratories 

(SNL). SES also moved a sizable portion of its technical staff to Albuquerque to make the best 

use of the facilities and engineers at SNL. This dish system has become a valuable tool for 

improving the collector and the Stirling engine. A major redesign of the structure led to a 

reduction in weight of 4,000 pounds while increasing its ability to withstand wind loads. A 

redesign of the valves that control the gas management system has led to improved operation of 

the engine. This dish/engine effort is particularly important because SES has power purchase 

agreements with Southern California Edison and San Diego Gas & Electric, which could lead to 

projects totaling 800 to 1,750 MW. 

The Energy Policy Act of 2005 directed DOE to assess the potential impact of CSP. In response, 

the DOE Solar Program issued a report entitled Assessment of Potential Impact of Concentrating 

Solar Power for Electricity Generation. The report summarized the various evaluations of CSP 

over the last several years (e.g., assessments by Sargent & Lundy and the National Academy) 

and concluded that the cost of CSP can be reduced to 5¢–7¢/kWh through the combination of 

R&D and deployment. Whereas R&D was largely a DOE responsibility, deployment was being 

driven primarily by the renewable portfolio standards established by the southwestern states. The 

64-MW project in Nevada was the first example of that happening. A team made up of 

representatives from industry, SNL, NREL, and the Solar Program met with the governors’ offices 

of several southwestern states during the year to alert them to the benefits of CSP. We found the 

states were particularly interested in the creation of jobs that would accompany the establishment 

of CSP manufacturing and projects. After discussions with the California Governor’s Office 

indicated an interest in knowing about CSP, the Solar Program had Black & Veatch write the 

report, Economic, Energy, and Environmental Benefits of Concentrating Solar Power in 

California. The team also met with several utilities during the year to discuss solar resources in 

their area and CSP cost scenarios. Utility representatives verified that they had become very 

interested in CSP because of the capability of CSP technologies to store energy. This is leading 

us to increase our focus on thermal storage in FY 2007. 

Solar Heating and Lighting 

Funding for SHL in FY 2006 was significantly lower than in FY 2005 and presaged DOE’s 

recommendation to Congress that SHL be terminated in FY 2007. This limited the activities in the 

subprogram. On the other hand, the establishment of a tax credit for solar water heaters created 

optimism among the industry that sales would increase. The legislation that established the tax 

credit also required qualifying solar water heating systems to be certified. This has placed 

increased importance on the Solar Rating and Certification Corporation (SRCC). SRCC thus 

continued to receive funding from the Solar Program to help them process the increased number 

of systems for which industry was requesting certification. Both industrial partners continued 

working on the development of a low-cost solar water heater, albeit with less support from DOE. 

Both partners made design improvements to their water heaters and tested prototypes in 

preparation for introduction to the market, possibly in FY 2007. 

Several design improvements were made to the hybrid solar lighting (HSL) system. By the end of 

the year, 13 prototype systems had been installed throughout the country. Most of these, 

unfortunately, developed problems that have identified the need for a redesign of the system. A 

contract that was initiated in FY 2005 to estimate the market potential of HSL was expected to be 

completed in FY 2006. However, the lack of funding required this to be postponed. 

Solar Thermal R&D 108
New Directions 

In 2000 and again in 2002, the National Academy stated that CSP systems were too large and 

too expensive to ever be built. In 2006, however, projects in Spain resulting from a Royal Decree, 

along with the projects being established in the United States that were fostered by renewable 

portfolio standards, have proven that large CSP projects can be built. The investment tax credit 

established by EPAct 2005 reduced the cost of renewable power, making it easier for utilities to 

select CSP projects. These State and Federal policies have created an optimistic outlook for 

CSP, and the industry is growing. The Solar Program will respond by continuing to offer industry 

technical support and to begin development of the next generation of systems. An additional 

focus in FY 2007 will be planning for a more robust thermal storage activity. The Solar Program 

will also become more involved with issues surrounding transmission and the location of CSP 

plants (e.g., solar resource monitoring). 

By the end of FY 2006, it was apparent that SHL would receive funding in FY 2007. However, the 

message was clear that it had to change if it was to gain support. A major focus of FY 2007 will 

be to develop a new vision for SHL. Part of this may include non-technical activities that help 

industry expand the market for the technology. In the technical areas, analysis from NREL and 

our industrial partners shows the polymer water heaters will meet the 4.5¢/kWh goal. The next 

step is to assist our two industrial partners in the last technical changes prior to their 

commercialization of the products. The problems associated with the hybrid solar lighting systems 

installed during FY 2006 will result in a better design in FY 2007, and the field demonstration 

systems will be made operable. 

109 Solar Thermal R&D
Solar Thermal R&D 110
 

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 in FY 2006 include: 

Dish/Engine System R&D 

•	 Operated and maintained six-dish model power plant at Sandia National Laboratories, 

cataloging more than 80 development areas. 

•	 Completed design for manufacturing and assembly of dish structure, reducing weight by 

4,000 pounds. 

Parabolic Trough R&D 

•	 Started initial commercial operation of the first new parabolic trough plant to be developed in 

nearly 15 years. Arizona Public Service owns the plant, which was developed by Solargenix 

Energy. The plant uses parabolic trough collector technology developed by Solargenix under 

a cost-shared R&D contract with DOE/NREL. 

•	 Solargenix began construction of a 64-MW parabolic trough plant in Nevada. The plant uses 

a new second-generation parabolic trough collector design developed under the company's 

USA Trough Initiative R&D contract. 

Advanced Optical Reflector R&D 

•	 Continued to perform durability testing of optical materials and published results of durability 

testing of several mirror types. 

•	 Provided significant industry support about reflectors to the concentrating CSP and CPV 

industries. 

CSP Systems Analysis 

•	 Continued analysis in support of the WGA Solar Task Force, with an emphasis on analysis in 

support of a proposed southwest utility consortium. 

•	 Developed initial version of CSP Jobs and Economic Development Impact model. 

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____________________________________________________________________________________ 

 

 

 

____________________________________________________________________________________ 

 

 

 

 

Dish/Engine System R&D 

Performing Organization: Sandia National Laboratories (SNL) 

Key Technical Contact: Charles Andraka, 505-844-8573, ceandra@sandia.gov 

DOE HQ Technology Manager: Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2006 Budget:	 $1,550K 

Objectives 

•	 Improve the reliability and reduce the cost of dish/engine components and systems. 

•	 Support industry in the commercialization of the technology. 

•	 Perform R&D on dish/engine system components and systems. 

•	 Test, evaluate, and improve the performance of dish/engine components and systems. 

Accomplishments 

•	 Operated and maintained six-dish model power plant, cataloging more than 80 development 

areas. 

•	 Tested extensively to qualify valve vendors for gas management system. 

•	 Completed design for manufacturing and assembly (DFMA) of dish structure, reducing weight by 

4,000 pounds. 

•	 Developed systems model of field operation with shading and verified with data. 

•	 Supported hiring and training (mentoring) of Stirling Energy Systems (SES) staff. 

Future Directions 

Primary activities in FY 2007 will support SES's efforts toward commercialization by: 

•	 Continuing to evaluate the reliability of the six-dish mini power plant. 

•	 Identifying and resolving operational and reliability issues. 

•	 Supporting SES as it starts to deploy a 1-MW power plant. 

•	 Testing components to support manufacturable designs; assisting with other design elements. 

1. Introduction 

The DOE dish-Stirling program works closely with 

SES to improve system performance and reliability 

and to support deployment by industry in the near 

term, both of which are explicit goals of the DOE 

Solar Program Multi-Year Program Plan, section 

4.2.5.3. This year, our primary goal was to test, 

baseline the performance (reliability, availability, 

and efficiency) of six SES 25-kW dish-Stirling 

systems operating as a plant, and begin to solve 

reliability issues. 

The system is derived from the successful 

McDonnell Douglas Corporation (MDC) system, 

but was redesigned to improve cost. SES’s 

objective is to put this system into production 

within a few years, with a target market of 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 an aggressive deployment of 

25-kW dish-Stirling systems for bulk power 

generation. SES hardware is based on the triedand-true MDC design, with refinements for 

reducing manufacturing costs. SES is working 

closely with an SNL engineering team to maximize 

the possibility of success. 

This year, SNL and SES continued operation of 

the six-dish Model Power Plant (MPP) at SNL. The 

purposes of this plant are Reliability Improvement, 

Component Development, and Stakeholder 

Demonstrations. These purposes often conflict, 

and Sandia/DOE must defer to SES priorities 

because SES owns the hardware. 

The success of the MPP has, in part, led to SES 

signing agreements with Southern California 

Solar Thermal R&D

Concentrating Solar Power

112
 

 

 

 

Edison for up to 850 MW of power and San Diego 

Gas and Electric for up to 900 MW of power. 

Operation and improvement of the MPP is critical 

in the design process for these deployments. SES 

has made significant progress in developing site 

plans for these plants. The successes in 

partnering with these utilities and with companies 

developing the site plans were enabled by the 

operational plant at SNL. 

2. Technical Approach 

SES plans to achieve cost reduction by rapidly 

moving to high production rates in support of bulk 

power production. This approach, when compared 

to 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 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 rapidly 

training new solar engineers. 

Last year, we installed and began operating the 

six-dish system at SNL. Significant portions of the 

installation were performed by SES industry 

partners using SNL-developed procedures, which 

allowed evaluation of the field installation 

processes. This fiscal year, SNL worked with SES 

to continue cataloging reliability issues and 

developing an understanding of root causes, 

implementing solutions in a limited set of issues. In 

addition, we performed data development and 

collection in support of due diligence efforts. All of 

the dish system hardware is funded through SES 

investor financing, while SNL, through the DOE 

Concentrating Solar Power Subprogram, provides 

in-kind engineering support, technology transfer, 

training, and facilities. 

3. Results and Accomplishments 

The power conversion units (PCUs) included 

engines under various stages of development, 

from fully Kockums-built PCUs to SES-built PCUs. 

The Kockums engines are fully refurbished by 

SNL and SES. All of the systems were converted 

this year to the newer SNL-designed packages, 

featuring commercial-off-the-shelf (COTS) 

radiators, a robust cavity, and better access to the 

engine for maintenance. This package design has 

improved the maintainability and therefore the 

availability of the systems. All of the systems were 

operational for each of the stakeholder visits 

during the year, despite being taken offline at 

times for experimental upgrades to resolve or 

diagnose long-term issues. The systems have 

continued to operate a high level of efficiency, with 

peak net efficiencies in the range of 27%–29%. 

SNL engineers substantially supported SES in a 

major redesign of the dish structure, necessary to 

address assembly issues noted at SNL during the 

MPP installation. The new structure features a 

one-piece main beam, with high-rate assembly 

processes engineered into the design to support 

the needed deployment rates. SNL guided 

development of a suite of tools that combined 

Computational Fluid Dynamics wind load analysis, 

Finite Element structural analysis, and CIRCE2 

Optical analysis. This suite of tools allowed 

detailed evaluation of structural changes, and 

through an iterative process resulted in a weight 

reduction of about 4,000 pounds while providing a 

stiffer support structure. This weight reduction, as 

well as the manufacturability, is critical in reducing 

costs to meet SES deployment goals. The 

modeling suite was validated with structural 

measurements as well as optical measurement on 

the MPP dish systems. 

Continued operation of the systems has 

demonstrated that the valve redesign performed 

last year on the compressor valve has resulted in 

elimination of a critical failure mode. SNL has 

continued to lead the investigation of the entire 

gas management system (GMS), with the intent of 

understanding the design specifications for each 

valve and then qualifying vendor-supplied modern 

valves at each location. This work has been 

successful, identifying (and rejecting) several 

vendors with quality control issues and downselecting to a vendor with good quality and 

excellent costs. We are continuing to test the 

vendor’s valves and other GMS components, and 

next year will consolidate the selected 

components into an integrated GMS with 

dramatically reduced potential leak points. 

SNL has been heavily involved in mentoring and 

expertise development as SES began hiring 

aggressively this year, particularly in the controls 

area. Gary Thomas, the lead controls engineer, 

passed away at the beginning of the year. We 

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have developed a list of controls-related issues 

and a plan to address those issue in the short term 

(MPP and 1-MW builds) and in production. SES 

also hired an additional reliability engineer, an 

excellent VP of engineering, and a systems 

engineer. These key areas are critical to moving 

the development process forward. 

The systems have accumulated 8,025 dish-hours 

of operation so far (December 31, 2006). With the 

added engineering horsepower at SES, and a 

renewed emphasis on the reliability improvement 

aspect, we expect to dramatically increase 

operational hours in the next fiscal year. This 

added horsepower will better leverage SNL’s 

expertise into product improvement. The systems 

have performed well, with indicated efficiencies 

similar to the record of 29.4% net. Several SNLproposed changes to the engine package have 

further reduced weight, as well as slightly 

increasing system performance by improving 

aperture intercept of reflected light. 

SNL has worked closely with SES to develop 

improved data, information, and control handling 

and systems. We are embarking on a program to 

update the Supervisory Control and Data 

Acquisition system to provide graphical interfaces, 

historical online data, and efficient field 

communications. This system is database-driven 

and will provide views suitable for operators 

(simple), managers (summary), and engineers 

(highly detailed). In addition, SNL has continued to 

develop procedures and tools for capturing human 

interactions (electronic logbook) and documenting 

safe operational procedures. The larger number of 

systems requires diligent efforts to capture and 

catalog issue areas that will lead to product 

improvement. SNL has helped deploy a COTS 

Failure Reporting, Analysis, and Corrective Action 

System to formalize the process for reliability 

improvement and root cause analysis. 

SNL has developed a field performance model 

that incorporates dish shading into the loss 

calculations. This model has led to further 

understanding of operational limitations due to 

shading observed in the MPP, and has led to very 

minor adjustments in the field spacing proposed 

for the next-generation systems. The model also 

includes revenue stream calculations, so that 

optimizations can be influenced by enhanced 

summer revenues. 

SNL has updated its gas-fired test capabilities to 

support long-term cyclic and continuous testing of 

the SES engines. This capability will be critical for 

controls development, allowing full power 

operation with extensive instrumentation to 

characterize controls operations. This capability is 

also important for accelerating tests of seals and 

other wear components, so that enhanced 

versions can be developed and deployed. 

4. Planned FY 2007 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 shortterm fixes to the MPP, and outlined development 

paths for the production version. 

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 2007, we will: 

•	 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 

DFMA process. 

•	 Support SES as it starts to deploy a 1-MW 

power plant. 

•	 Actively participate in the DFMA. 

•	 Develop assembly plant and field-deployable 

alignment tools to support rapid deployment 

•	 Develop rapid deployment component designs 

including foundation, dish structures, etc., and 

test prototypes at SNL. 

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____________________________________________________________________________________ 

 

 

 

 

Parabolic Trough R&D 

Performing Organizations: National Renewable Energy Laboratory (NREL)

 Sandia National Laboratory (SNL) 

Key Technical Contacts:	 Henry Price (NREL, Primary Contact), 303-384-7437, 

henry_price@nrel.gov 

Doug Brosseau (SNL), 505-844-5218, dabross@sandia.gov 

DOE HQ Technology Manager:	 Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2006 Budgets:	 $2,310K (NREL), $500K (SNL) 

Objectives 

•	 Support development of near-term parabolic trough technology for central station power
 

generation. 

•	 Support development of advanced technologies for next-generation parabolic trough solar fields, 

thermal energy storage, and power plant technologies to meet long-term goals of the DOE Solar 

Program Multi-Year Technical Plan (MYTP). 

•	 Support the expansion of U.S. industry to supply parabolic trough technology. 

•	 Support continued SunLab1 collaboration on parabolic trough technology development and 

testing. 

Accomplishments 

•	 During FY 2006, initial commercial operation began at the first new parabolic trough plant in 

nearly 15 years. The plant is owned by Arizona Public Service (APS) and was developed by 

Solargenix Energy of Raleigh, NC. It is a 1-MWe solar power plant using an organic Rankine 

power cycle provided by Ormat Technologies of Sparks, NV. The plant uses parabolic trough 

collector technology developed by Solargenix under a cost-shared R&D contract with DOE/NREL. 

•	 Solargenix began construction of a 64-MW parabolic trough plant in Eldorado Valley, near 

Boulder City, NV. 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. The plant is expected to begin operation in the 

spring of 2007. 

•	 Industrial Solar Technology (IST) completed phase I of its FY 2004 USA Trough Initiative contract 

for the development of an advanced low-cost parabolic trough concentrator. The decision was 

made to proceed to phase II. The contract for phase II was placed at the end of FY 2006. 

•	 SNL has developed and tested a prototype theoretical overlay photographic alignment system for 

evaluating the alignment of mirrors and receivers on parabolic trough collectors installed in a 

solar field. 

•	 Latent Structures developed a non-intrusive device to measure gas composition and pressure in 

a parabolic trough receiver. The system was field-tested and detected hydrogen in a number of 

receivers installed in the solar field. 

•	 NREL developed a new laboratory test stand for measuring the thermal losses from parabolic 

trough receivers. The test stand was used to test eight receivers provided by FPL Energy. Four of 

the eight had shown high glass temperatures in the solar field. Receiver testing found that the 

receivers that were hot in the solar field had hydrogen present, which caused thermal losses to 

increase by a factor of four. 

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. 

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________________________________________________________________________________ 

 

 

•	 NREL continued 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 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 the 9,600 receivers in two days 

at SEGS VI to help FPL Energy categorize receiver performance in advance of a major receiver 

upgrade program. 

•	 SNL began initial evaluation of alternative molten salt formulations for use as the heat transfer 

fluid in trough solar fields and thermal storage systems. SNL also developed models and plans to 

support laboratory testing of freeze protection and recovery approaches in solar fields based on 

impedance heating concepts. 

•	 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. 

Future Directions 

•	 Continue development of advanced receiver and concentrator technologies to meet long-term 

DOE Solar Program MYTP goals. 

•	 Support development of advanced thermal energy storage technologies. 

•	 Continue building laboratory capability to support trough testing and analysis. 

1. Introduction 

Parabolic trough technology is starting to be 

reintroduced into the marketplace. During 

FY 2006, the first parabolic trough power plant to 

be built in 15 years began commercial operation. 

The 1-MWe Arizona Public Service (APS) 

Saguaro parabolic trough solar power plant first 

produced electricity in December 2005 (Fig. 1). 

Solargenix Energy began construction of a 64­

MWe parabolic trough solar power plant in 

February 2006 that is expected to be completed 

and start operation in the spring of 2007. Both 

plants use Solargenix parabolic trough collector 

designs developed under cost-shared DOE R&D Fig. 1. New APS solar power plant using contracts. 

Solargenix parabolic trough concentrator and 

Schott receiver In addition, several Spanish parabolic trough 

projects reached financial closure during FY 2006. 

These projects will use thermal energy storage The focus of the DOE parabolic trough R&D

program has been to: technology that was developed by the U.S.
 

Concentrating Solar power Program. • 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. 

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•	 Encourage expanded U.S. supply in 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 

The parabolic trough R&D effort is broken into four 

areas in the DOE Solar Program MYTP: (1) USA 

Trough Initiative, (2) solar field technology , (3) 

thermal energy storage technology, and (4) 

systems integration. 

2.1 USA Trough Initiative 

The USA Trough Initiative includes a number of 

competitive solicitations designed to encourage 

U.S. industry to develop new technology and 

services that advancethe state of the art of 

parabolic trough technology. During FY 2006, 

activities focused on: 

•	 Completion of phase I activities and decisions 

to progress to phase II for two contracts 

awarded in FY 2005 to Sola rgenix Energy and 

IST for the FY 2004 near-term component 

manufacturing solicitation. 

•	 Awarding a new contract to PPG for the 

FY 2005 near-term component manufacturing 

solicitation . 

•	 Technical support by S unLab to Solargenix 

and IST. 

2.2 Solar Field Technology 

The solar field technology agreement focuses on 

SunLab development of new parabolic trough 

solar technology and tools for evaluation of trough 

technology. During FY 2006, SunLab activities 

focused on: 

•	 Development of an IR camera system for rapid 

field assessment of receiver performance. 

•	 Developing a new field alignment system for 

assessing alignment of mirrors and receivers 

on parabolic trough concentrators. 

•	 Development of a new receiver test stand to 

accurately test the thermal losses in a 

laboratory-controlled environment. 

•	 Continued development of advanced selective 

coating technologies for receivers, with the 

focus on developing coatings with improved 

thermo/optic properties and that are thermally 

stable in air up to 500°C. 

•	 Development of a system to nondestructively 

test the vacuum on receiver tubes. 

•	 Development of an approach for in-situ 

injection of an inert gas in receiver tubes. 

2.3 Thermal Energy Storage (TES) Technology 

The SunLab TES program is responsible for the 

development of the indirect 2-tank molten-salt TES 

system that will be used in several parabolic 

trough solar plants under development in southern 

Spain. Unfortunately, this TES technology is still 

more expensive than the U.S. power market will 

tolerate (about $35–$4 0/kWht). The objective of 

the TES R&D effort is to develop next-generation 

TES technolog y, which will cost substantially less 

($15–$20/kWht). To achieve this goal, the DOE 

R&D effort focuses on: 

•	 Developing single-tank (thermocline) TES 

systems. 

•	 Applying TES systems that use inorganic 

molten salt directly in the solar field. 

•	 Developing advanced new heat-transfer fluids 

that will lower the cost of th e TES system. 

•	 Developing a heat-transfer, fluid-testing 

program at the SEG S plants and developing 

the laboratory tests to evaluate the hydrogen 

concentration in the fluid. 

2.4 Systems Integration 

This activity focuses on the development of 

systems-integration tools for evaluation of trough 

technologies and assessment of program 

activities. Specific FY 2006 activities inc luded: 

•	 The VSHOT was used to measure the optical 

accuracy of the Solargenix SGX-1 

concentrator, the IST concentrator, and the 

Luz LS-2 and LS-3 concentrators. 

•	 Nexant completed an a nalysis of the optimumsize parabolic trough power plant, the cost 

advantage of building trough plants in a power 

park, and the performance and cost impact o f 

moving to dry cooling. 

• NREL began updating the TroughNet Web s ite. 

• Quarterly milestone reports weregenerated in 

support of the CSPFY 2006 Joul e milestone. 

Budget allocations by task are providedbelow. 

Task Title FY * 

Budget ($K) 

 2006 /CO 

USA Trough Initiative 300/0 

Solar Field Technology 1,690/150 

Thermal Storage Technology 440/100 

Trough Systems Integration 380/0 

*Carryover from FY 2005 

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3. Results and Accomplishments 

3.1 USA Trough Initiative 

During FY2006, Solargenix Energy developed a 

new second-generation parabolic trough 

concentrator design that is currently being used in 

its new 64-MWe parabolic trough plant under 

construction in Eldorado Valley, near Boulder City, 

NV. The new Solargenix collector (the SGX-1) is a 

clear advancement over the company's firstgeneration collector (DS-1) used at the 1-MWe 

APS parabolic trough plant completed in 2005. 

The new collector design has the following 

improvements: 

•	 The collector uses a new low-cost organic hub 

design developed by Gossamer. 

•	 The spaceframe has 50% fewer parts than the 

DS-1, and about 80% fewer fasteners. 

•	 The spaceframe is 30% lighter. 

•	 Field assembly requires one-third of the time. 

•	 The design uses low-cost extruded parts. 

•	 No field alignment of mirrors is required during 

assembly. 

•	 Simple drilling jigs are used to obtain high 

tolerances. 

These features, combined with the new drive, ball 

joint assemblies, and the control system 

developed from earlier contracts, as well as the 

new improved Schott receiver, mean that the 

Solargenix collector is now potentially the most 

advanced and cost-effective parabolic trough 

collector design for high-temperature commercial 

solar power plant applications. Figures 2 and 3 

highlight the new structure and Gossamer organic 

hub design. 

Fig. 2. New Solargenix SGX-1 concentrator with 

Gossamer organic hubs 

Fig. 3. Gossamer organic hubs 

Work has been completed on the Solargenix 

FY 2005 USA Trough Initiative request for letters 

of interest (LOI) phase I contract. Solargenix has 

identified the detailed statement of work for 

phase II of the contract. During FY 2006, the 

Solargenix Nevada collector test loop was 

damaged by high winds and Solargenix needed to 

remove the collectors. A significant amount of the 

remaining funds on earlier contracts were for 

adding a thermal loop to the collector test loop. 

NREL and Solargenix have decided to redirect the 

money for the thermal loop to pay for the phase II 

efforts. The phase II work will focus on developing 

a larger space frame that holds up to four 

receivers and possibly a wider aperture. This work 

will also look at reducing the cost of the drive. 

IST completed phase I of its USA Trough contract. 

This effort developed a new design for a parabolic 

trough collector that rotates around the receiver, 

potentially eliminating the need for conventional 

flex hoses or ball joint assemblies. The new 

design would use a low-cost structure similar to 

the IST process-heat parabolic trough (PT-1) 

collector. Part of the effort included developing 

detailed structural design models (Fig. 4). The 

models were validated by building several new 

PT-1 collector models and testing them to failure. 

Based on these results, the PT-1 design was 

modified to improve its structural integrity. The 

structural models were then used to develop a 

new fixed focal point trough (FFPT) collector that 

would double the length and aperture of each 

module. Preliminary designs were developed for 

the drive and bearing to allow the concentrator to 

rotate around the receiver. An alternative design 

was also developed in which the receiver rotated 

with the collector and required some form of swivel 

or ball joint at the end of the collector. The SunLab 

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contract review team decided to move forward location in the mirror, one can determine any 

with phase II of the IST development. IST misalignment of mirrors or receivers. 

negotiated the phase II work effort and will begin 

Alignment work, in the early part of FY 2007, on developing Fixture two new full-scale prototypes, one of the FFPTs, 

Camera and a scaled-up version of the IST PT-1 design. Receiver 

Fig. 4. Finite-element analysis of new IST focal 

point power trough collector showing predicted 

stresses in the reflector. 

One contract was selected for award from the 

FY 2005 LOI. Contract selection went to PPG, a 

large U.S. glass supplier, for development of a 

new parabolic trough mirror. During contract 

negotiations, PPG decided not to move forward 

with the proposed statement of work based on a 

reprioritization of its internal R&D funds. 

FY 2006 Milestones: 

•	 Go/no go decision on Solargenix USA Trough 

Phase II LOI work. Statement of work and 

contract extension in place. (6/06) 

•	 Go/no go decision on IST USA Trough LOI 

Phase II work. Statement of work and contract 

extension in place. (9/06) 

3.2 Solar Field Technology 

During FY 2006, SNL conducted field tests of a 

new prototype system for conducting field 

alignment checks on parabolic trough collectors. 

The system, called the theoretical overlay 

photographic (TOP) alignment system, can be 

used to check for misalignment of mirrors and 

receivers. The system concept, shown in Fig. 5, 

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 distance such that the receiver only 

fills a portion of the image seen in the mirrors. The 

TOP system compares where the receiver image 

actually appears compared to where it should 

appear if the collector were perfectly aligned. 

Based on the relative position of the receiver 

No

Mirror

rmals 

Image 

Parabolic 

Mirrors 

Receiver 

Boresight

Camera 

Fig. 5. Theoretical overlay photographic (TOP) 

alignment conceptual schematic. Accurately 

positioned cameras on an alignment fixture 

measure the position of the receiver image in the 

mirror. The boresight camera is used to align the 

fixture receiver and mirror module. The mirror is 

aligned to superimpose the receiver image onto 

the theoretically calculated image position. 

A major advantage of this alignment-system 

approach is the ability to rapidly take images of 

trough modules between existing rows of 

commercial trough collectors. The TOP system, 

shown in Fig. 6, will allow rapid measurement and 

characterization of large commercial solar fields. 

Fig. 6. Prototype TOP alignment system under 

test at the APS Saguaro parabolic trough plant. 

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Work continues on development of a new 

selective coating that appears to meet the longterm selective property goals for parabolic trough 

receivers (α ≥ 0.96 and ε ≤ 0.07 @ 400°C). During 

FY 2005, a first prototype of the coating was 

deposited using a single-component deposition 

process. During FY 2006, NREL adapted its 

vacuum deposition system to allow deposition of 

two materials at the same time. This allows 

deposition of two constituent compounds. During 

FY 2006, new prototype coatings were deposited. 

The new coating improved the absorptance, but 

the lack of good layer thickness control resulted in 

a higher emittance than desired. Work has 

continued on improving the deposition thickness 

control. 

During FY 2005, NREL developed a technique for 

evaluating receiver thermal performance in 

operating solar fields using an IR camera. FPL 

Energy, the operator of seven of the SEGS plants, 

found the system to be useful in understanding 

solar field performance and indicated that it would 

be a useful tool for periodic monitoring of receiver 

performance. During FY 2006, an effort was 

undertaken to improve the speed of field 

measurements and data analysis to allow a more 

rapid field survey of receiver condition. Upgrades 

to the IR system allowed all 9,600 receivers in the 

SEGS VI solar field to be imaged during a 2-day 

period. Although, the new system was able to 

image the field rapidly, the data analysis still took 

too much time. Additional upgrades are planned 

for FY 2007 to enable much quicker data 

assessment. 

Latent Structures and NREL developed a new 

non-destructive device to measure vacuum on 

receivers while installed in the solar field. The 

system works because confined gases under low 

pressure emit characteristic spectra when a highvoltage discharge is allowed to pass through the 

gases. The characteristic emission wavelengths 

provide the identity of the gas (qualitative 

analysis); and the intensity of the emissions are 

proportional to the amount of gas (quantitative 

analysis). Field-testing with the device 

demonstrated that the hot glass failure being 

observed on many of the receivers at the SEGS 

plants was due to the presence of hydrogen in the 

receivers. Figure 7 shows the device and a 

plasma arc of hydrogen during calibration of the 

device. 

Fig. 7. Device for in-situ field measurement 

of receiver vacuum (Latent Structures) 

During FY 2006, NREL developed a new receiver 

thermal loss test platform to help accurately 

evaluate thermal losses from parabolic trough 

receivers. The test bed is based on approaches 

used by both Schott and The German Aerospace 

Center (DLR). The test bed uses electric 

resistance heaters to heat a receiver up to a 

simulated steady state temperature. The power 

required to keep the receiver at a steady state 

temperature is equal to the thermal losses from the 

receiver. Figure 8 shows the new thermal test bed. 

Fig. 8. New parabolic trough receiver thermal loss 

test bed 

During FY 2006, the plan was to test several new 

and used receivers on the test bed. However in 

early FY 2006, FPL Energy requested that NREL 

test eight Solel UVAC receivers that they had 

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removed from the solar field. Four of the receivers 

had exhibited the hot glass failure during operation 

in the solar field and four were in good condition. 

All eight receivers were tested. The four hot 

receivers also exhibited the hot glass 

temperatures under test and had thermal losses 

four to five times that of the cool receivers. 

Figure 9 shows the glass temperature and thermal 

losses from one good (cold) and one bad (hot) 

receiver. The vacuum gas measurement system 

showed that the rapid temperature increase on the 

hot tube corresponded to the release of hydrogen 

from the getters in the receiver vacuum annulus. 

Fig. 9. Parabolic trough receiver thermal loss test 

bed results 

One approach for reducing thermal losses from 

hydrogen and other gases in the receiver vacuum 

annulus is to inject a small amount of a thermally 

inert gas to disrupt the hydrogen heat transfer. 

SNL has proposed an approach for field repairs of 

receivers experiencing hydrogen build-up. A gasfilled volume with the correct amount of inert gas is 

placed on a heat collection element. A laser is 

used to form the volume to the receiver glass. 

The laser is then focused to drill a hole through the 

receiver and the side of the gas-filled volume 

attached to the receiver, allowing the inert gas to 

enter the receiver. The laser is then defocused to 

close the drilled hole. The next step is to prototype 

the concept. 

FY 2006 Milestones: 

•	 Field test of new IR camera system for 

receiver field performance assessment. (8/06) 

•	 Complete second prototype of advanced 

selective coating for higher temperatures, 

improved selective properties, and improved 

manufacturability. (10/06) 

•	 Report on test results from new receiver test 

bed. Include comparison of new and old 

receivers. (delayed to 07/07) 

•	 Field test of device for non-destructive in-situ 

evaluation of receiver vacuum gas 

composition. (11/05) 

•	 Field test validation of new alignment jig using 

modified distant observer approach to 

evaluate the alignment of mirrors and 

receivers on a parabolic trough collector 

module. (10/06) 

•	 Assessment of distant observer technique for 

evaluation of collector field alignment. 

(cancelled) 

3.3 Thermal Energy Storage Technology 

A SunLab and industry team has developed 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, as the most 

promising opportunity for cost reduction and 

improving the overall economics of parabolic 

trough plants in the future. A trip to visit the Italian 

National Agency for New Technologies, Energy 

and the Environment (ENEA) parabolic trough 

molten-salt test facility is planned for early in 

FY 2007. The storage team will also meet with 

DLR to get an update on its concrete and phasechange-material thermal storage activities. The 

update of the thermal energy storage plan was 

postponed until after the visits to ENEA and DLR. 

Due to delays in the start-up of the APS 1-MWe 

trough plant and changes in the rules for the 

Arizona renewable energy standard, only limited 

discussions with APS took place during FY 2006 

on initiating the thermocline storage test. 

The advanced heat transfer fluid development 

efforts are looking for new organic fluids that have 

sub-atmospheric vapor pressures at operating 

temperatures, low freeze point, and higher 

(greater than 400°C) upper temperature operating 

limits. Although a number of potentially attractive 

organic fluids have been identified, it is the thermal 

stability at temperatures around 400°C that limits 

use of most fluids. During FY 2006, the 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 replacement cost of 

the fluid, but also because decomposition of the 

fluid results in hydrogen being present in the fluid, 

which is an issue for maintaining the vacuum in 

the receiver. A number of possible degradation 

mechanisms have been identified. Based on this 

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knowledge, several new polyphenyl compounds 

are being evaluated for use. Unfortunately, the 

polyphenyl compounds tend to have a high freeze 

point, so work is progressing on evaluating 

eutectic mixtures to determine if the freeze point 

can be reduced to an acceptable level. 

Another option for advanced heat transfer fluids is 

the identification and development of alternative 

inorganic molten salt formulations. Current 

formulations, while offering many advantages over 

the therminol oil currently used in the SEGS 

plants, have distinct disadvantages. Primary 

among these are high freezing temperatures, 

higher cost, and potential unidentified material 

interaction issues. Testing completed at SNL 

during FY 2002 through FY 2004 identified both 

the potential benefits associated with improved 

molten salt formulations as well as some of the 

key issues related to their use in parabolic trough 

solar fields. Planning in FY 2005 and efforts in 

FY 2006 were 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 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 FYs 2007 and 2008. 

FY 2006 Milestones: 

•	 Advanced heat transfer fluid R&D progress 

review and development plan. (9/06) 

•	 Updated molten-salt TES plan. (12/06) 

3.4 Systems Integration 

SunLab is working to develop a better 

understanding of the cost and performance of the 

original Luz parabolic trough concentrators in an 

effort to establish a clear baseline cost and 

performance for comparison to new collector 

designs. In FY 2006, FPL Energy allowed NREL to 

VSHOT test the LS-2 and LS-3 collectors at two of 

its sites. The LS-2 and LS-3 concentrators 

demonstrated slope errors of 2.8 to 3.0 mrads. 

Figure 10 shows the VSHOT testing at SEGS IX. 

Fig. 10. Optical testing of LS-3 concentrator at 

SEGS IX with VSHOT 

Nexant, Inc., completed an analysis of the 

optimum size parabolic trough power plant, the 

cost advantage of building trough plants in a 

power park, and the performance and cost impact 

of moving to dry cooling. The optimum size for a 

parabolic trough plant appears to be on the order 

of 200 to 250 MWe with current technology, 

depending on whether thermal energy storage is 

included. The study found that building four 

250 MWe plants together could reduce the cost of 

energy by about 10% to 12%. Switching to dry 

cooling increased the cost of energy by about 7% 

to 10%, depending on climate and other factors. 

All three task reports can be downloaded from 

NREL’s publication database. 

During FY 2006, NREL began an update of the 

TroughNet Web site. A major effort is being 

pursued to get all subcontractor technical reports 

updated and placed on the Web. The technical 

content is being updated to reflect the current 

status of parabolic trough technology. TroughNet 

will be moved from the EERE to the NREL 

Web site. TroughNet is currently scheduled to be 

updated by the second quarter of FY 2007. 

Quarterly milestone reports were generated in 

support of the Concentrating Solar Power (CSP) 

FY 2006 Joule Milestone. The Joule metric had 

both cost of energy and annual solar to electric 

efficiency metrics. The parabolic trough 

technologies being installed in the 64-MWe 

Nevada Solar One power plant, Solargenix SGX-1 

parabolic trough collector, and Schott PTR70 

parabolic trough receiver are used to evaluate 

progress toward the milestones listed above. The 

table below shows the current cost and 

performance milestone goals as well as the 

current status of commercial parabolic trough 

technology. 

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The table shows that the current commercial 

parabolic trough technology exceeds both the 

Joule cost metric and DOE annual solar-to-electric 

performance milestones. This is in large part due 

to the aggressive efforts by industry to implement 

improved technology in their commercial products. 

The Solar Energy Technologies Program R&D 

efforts in recent years have played an important 

role in achieving these results. The cost of 

electricity is also very sensitive to the debt interest 

rate. With recent interest rate increases, we felt 

that the levelized cost of energy (LCOE) 

calculation should also reflect a more current debt 

interest rate. The following table shows that the 

technology meets the milestone metric goals even 

with today’s higher interest rates. 

FY 2006 CSP Joule Metric 

Milestones Goal Commercial 

Technology 

Debt Cost % 6% 6% 8% 

Real LCOE 

(2004$) 

12-14 

¢/kWh 

10.8 

¢/kWh 

12.1 

¢/kWh 

Annual Solar-toElectric Efficiency 11.9% 14.0% 

FY 2006 Milestones: 

•	 Initial revision of updated TroughNet Web site 

implemented on nrel.gov server. (delayed until 

FY 2007) 

•	 Draft report of trough baseline data and 

modeling assumptions. (9/06) 

4. Planned FY 2007 Activities 

Key activities planned for FY 2007 include: 

•	 Phase II of USA Trough Initiative near-term 

component manufacturing contracts with IST 

and Solargenix will build prototypes of new 

concentrators. 

•	 VSHOT testing of new concentrators 

developed under USA Trough Initiative. (9/07) 

•	 Modify VSHOT to perform three-dimensional 

mapping of mirrors. (03/07) 

•	 Field demonstration of new TOP concentrator 

optical alignment tool. (09/07) 

•	 Complete receiver testing of new and used 

receivers with new receiver thermal loss test 

rig. (07/07) 

•	 Continue implementation and optimization of 

co-deposition prototype samples of new hightemperature selective coating. (09/07) 

•	 Initiate program to test thermocline storage 

system at APS 1-MWe plant. 

•	 Evaluation and development of inorganic salt 

compositions for use as direct thermal energy 

storage fluid. 

•	 Initiate testing of receivers with molten salt to 

evaluate their freeze/thaw behavior. 

•	 Evaluate polyphenyl compounds for use as 

lower pressure and higher temperature heat 

transfer fluids. 

5. Major FY 2006 Publications 

Canada, S.; Brosseau, D.A.; Price, H. (2006). 

"Design and Construction of the APS 1-MWe 

Parabolic Trough Power Plant." Paper No. 

ISEC2006-99139. Morehouse, J.H. and Krarti, M., 

eds. Solar Engineering 2006: Proceedings of the 

ASME 2006 International Solar Energy 

Conference (ISEC2006), 9–13 July 2006, Denver, 

Colorado. 

Hurt, R.; Yim, W.; Boehm, R.; Hale, M.J.; Gee, R. 

(2006). "Advanced Parabolic Trough Field 

Testing—Real Time Data Collection, Archiving, 

and Analysis for the Solargenix Advanced 

Parabolic Trough." Paper No. ISEC2006-99078. 

Morehouse, J.H. and Krarti, M., eds. Solar 

Engineering 2006: Proceedings of the ASME 2006 

International Solar Energy Conference 

(ISEC2006), 9–13 July 2006, Denver, Colorado. 

Marcotte, P.; May, K.; Forristall, R. (2006). 

"Development of the Focal Point Power Trough 

(FPPT): An Advanced Parabolic Trough 

Concentrator for Electricity Generation." CampbellHowe, R., ed. Proceedings of the Solar 2006 

Conference, 9–13 July 2006, Denver, Colorado 

(CD-ROM). 

Kelly, B. (2006). Nexant Parabolic Trough Solar 

Power Plant Systems Analysis; Task 1: Preferred 

Plant Size, 20 January 2005–31 December 2005. 

59 pp.; NREL Report No. SR-550-40162. 

Kelly, B.; Kearney, D. (2006). Parabolic Trough 

Solar System Piping Model: Final Report, 13 May 

2002–31 December 2004. 23 pp.; NREL Report 

No. SR-550-40165. 

Kelly, B. (2006). Nexant Parabolic Trough Solar 

Power Plant Systems Analysis; Task 3: Multiple 

Plants at a Common Location, 20 January 2005– 

31 December 2005. 32 pp.; NREL Report No. SR550-40164. 

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Kelly, B. (2006). Nexant Parabolic Trough Solar 

Power Plant Systems Analysis; Task 2: 

Comparison of Wet and Dry Rankine Cycle Heat 

Rejection, 20 January 2005–31 December 2005. 

27 pp.; NREL Report No. SR-550-40163. 

Kolb, G.J.; Hassani, V. (2006). "Performance 

Analysis of Thermocline Energy Storage Proposed 

for the 1 MW Saguaro Solar Trough Plant." Paper 

no. ISEC2006-99005. Morehouse, J.H. and Krarti, 

M., eds. Solar Engineering 2006: Proceedings of 

the ASME 2006 International Solar Energy 

Conference (ISEC2006), 9–13 July 2006, Denver, 

Colorado. 

Parabolic Trough Solar Thermal Electric Power 

Plants. (2006). 2 pp.; NREL Report No. FS-550­

40211; DOE/GO-102006-2339. 

Prabhu, E. (2006). Solar Trough Organic Rankine 

Electricity System (STORES) Stage 1: Power 

Plant Optimization and Economics, November 

2000–May 2005. 67 pp.; NREL Report No. SR550-39433. 

Price, H.; Forristall, R.; Wendelin, T.; 

Lewandowski, A.; Moss, T.; Gummo, C. (2006). 

"Field Survey of Parabolic Trough Receiver 

Thermal Performance." Paper No. ISEC2006­

99167. Morehouse, J.H. and Krarti, M., eds. Solar 

Engineering 2006: Proceedings of the ASME 2006 

International Solar Energy Conference 

(ISEC2006), 9–13 July 2006, Denver, Colorado. 

Wendelin, T.; May, K.; Gee, R. (2006). "Video 

Scanning Hartmann Optical Testing of State-ofthe-Art Parabolic Trough Concentrators." Paper 

No. ISEC2006-99172. Morehouse, J.H. and Krarti, 

M., eds. Solar Engineering 2006: Proceedings of 

the ASME 2006 International Solar Energy 

Conference (ISEC2006), 9–13 July 2006, Denver, 

Colorado. 

Diver, R., Moss, T (2006). "Practical Field 

Alignment of Parabolic Trough Solar 

Concentrators," Paper No. ISEC2006-99146. 

Morehouse, J.H. and Krarti, M., eds. Solar 

Engineering 2006: Proceedings of the ASME 2006 

International Solar Energy Conference 

(ISEC2006), 9–13 July 2006, Denver, Colorado. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 

2006 

($K) 

Cost 

Share 

Solargenix Energy 

Nicholas Potrovitza 

Raleigh, NC 

randycgee@comcast.net 

USA Trough: Near-Term Component/ 

Subsystem Development – Advanced 

Parabolic Trough Concentrator 

Components and Subsystems, Phase II 

(299)* 20% 

Industrial Solar 

Technology 

Ken May 

Golden, CO 

industrialsolar@qwest.net 

USA Trough: Near-Term Component/ 

Subsystem Development – Advanced 

Parabolic Trough Concentrator, Phase II 

220 55K 

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 0 

Latent Structures, LLC 

Dr. Robert Meglen 

Boulder, CO 

bmeglen@comcast.net 

Development of field instrument nonintrusive measurement of hydrogen in 

trough receiver annulus 

30 0 

Arizona Public Service 

Scott Canada 

Phoenix, AZ 

scott.canada@aps.com 

Planned for use in thermocline storage 

test to begin in FY 2007. 350 20% 

* Funded with redirected funds from prior year (FY 2004–2005) contracts from CSP ($243K) and Nevada Renewable 

Earmark ($56K). 

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____________________________________________________________________________________ 

 

 

Advanced Optical Reflector R&D 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Cheryl Kennedy, 303-384-6272, cheryl_kennedy@nrel.gov 

DOE HQ Technology Manager: Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2006 Budget: $130K 

Objectives 

•	 The cost of the solar collector technologies needs to be reduced by half to achieve the long-term 

goals of developing parabolic-trough power plants, power towers, and dish-Stirling systems 

capable of competing on a cost competitive basis with conventional fossil power technologies as 

dispatchable intermediate power generation in the wholesale power market (levelized energy cost 

[LEC] $0.04 to $0.06/kWh). For mirrors, this is accomplished through technology advances by 

moving from heavy glass mirror reflectors 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 

•	 Continued to perform durability testing of optical materials and published results of durability 

testing of several mirror types. 

•	 Provided significant industry support about reflectors to the concentrating solar power (CSP) and 

concentrating photovoltaic (CPV) industries. 

Future Directions 

•	 Continue durability testing of optical materials to determine lifetime of solar reflector materials. 

•	 Analyze and publish results of testing of thin-glass mirrors applied to CSP technologies. 

•	 Analyze and publish status of reflector materials. 

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 MultiYear 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 are identified based 

on their potential for low cost and high optical 

performance and durability. All candidate materials 

are optically characterized prior to exposure 

testing and as a function of exposure time to 

assess optical durability. These mirrors are 

subjected to accelerated or outdoor weathering at 

a variety of geographically diverse exposure sites. 

3. Results and Accomplishments 

•	 Provided status of test results of candidate 

solar mirror samples and identified promising 

candidates. (11/06) 

•	 Provided significant industry support about 

reflectors to CSP and concentrating 

photovoltaics (CPV) industry. 

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3.1 Glass Mirrors 

Glass mirrors have excellent durability in terms of 

reflective layer corrosion, are readily available, 

have the confidence of the solar manufacturing 

industry, and are commercially deployed. 

However, they are heavy, fragile, and require 

expensive slumped glass for curved shapes. 

Trough mirrors (used in commercial solar plants) 

manufactured by Flabeg have been very durable; 

they use silvered thick, slumped low-iron glass 

that is protected with a proprietary multilayer paint 

system designed for outdoor exposure (see Fig. 1). 

Flabeg reported to NREL they converted their 

mirror line to 4- or 5-mm glass and a new low-lead 

paint system in FY 2003, in which the lead was 

reduced to the point that durability remained 

equivalent. The base paint of the three-layer paint 

system contains 2.5% lead, the intermediate paint 

contains 1% lead, and the white top coat is acrylic 

based with high UV stability. Side-by-side 

exposure testing of the original and new 

construction began in the second quarter FY 2004. 

After 2 years of accelerated Weather-Ometer 

(WOM) and outdoor exposure in Colorado, the 

new mirrors with the reduced lead paint system 

are performing similarly to the original mirrors. 

[The Atlas Ci65a WOM uses a xenon-arc light 

source with filters designed to closely match the 

terrestrial air-mass 1.5 solar spectrum and 

operates continuously at 60°C and 60% relative 

humidity (RH), with light levels about equal to 

outdoor exposure. A single day of testing 

(24 hours) is roughly equivalent to three times the 

outdoor exposure in terms of light intensity. 

 Equivalent NREL Exposure Time (years) 

0 3 6 9 12 15 18 21 24 

90 

95 

100 

% Hemispherical Reflectance 

APS - OLD 

FLA - OLD 

NREL - OLD 

WOM - OLD

0 10 20 30 40 50 60 70 8 

85 

0 

Total UV Dose (100 x MJ/m2) 

Fig. 1. Loss of solar-weighted reflectance of 

original Flabeg thick-glass mirrors as function of 

accelerated WOM and outdoor exposure at 

Phoenix, AZ (APS), Miami, FL (FLA), and Golden, 

CO (NREL), in total UV dosage. 

Two significant changes in mirror manufacturing 

have recently occurred in the classical wetchemistry process because of environmental 

concerns. The first is the method of forming a 

copper-free reflective mirror, and the second is the 

use of lead-free paints. The copper-free process 

requires stringent 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 are limited because the glass, 

chemical silvering, and mirror paint industries have 

consolidated. 

Testing of samples of Pilkington (4-mm copperfree) mirrors and “Spanish” (Cristaleria Espanola 

S.A; i.e., Saint Gobain) glass mirrors (3 mm, 

copper-free, and lead-free paint), bonded to steel 

with four different candidate adhesives, was 

initiated in FY 2001 for possible use at Solar Tres. 

Neither Pilkington nor Spanish mirrors exposed 

outdoors for 72 months show degradation up to 

this point (see Fig. 2). Pilkington mirrors exhibit 

better optical durability than the Spanish mirrors in 

accelerated WOM exposure testing. Spanish 

mirrors degraded 19.0%, whereas Pilkington 

mirrors degraded 2.8% after 53 months of 

accelerated WOM exposure. 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 

80 

85 

90 

95 

100 

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 

Total UV Dose (100 X MJ/m2) 

% Hemispherical Reflectance 

SPA/GE TSE 392-C ADH PIL/GE TSE392-C ADH 

SPA/GE D1-SEA210B ADH PILS/GE D1-SEA210B ADH 

SPA/KRAFFT SILKRAF ADH PIL/KRAFFT SILKRAF ADH 

SPA/DOW Q3-6093 ADH PIL/DOW Q3-6093 ADH 

Fig. 2. Loss of solar-weighted reflectance of thick 

Pilkington and Spanish reflectors with copper-free 

back layer, Pb-free paint, and four adhesives as a 

function of WOM exposure. 

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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 was prepared to 

identify the most promising combinations of paints 

and adhesives for use with solar reflectors. After 

more than three years of exposure in the WOM 

and in damp heat, data indicate that the mirror 

performance strongly depends on the back 

protection. (The BlueM damp-heat chamber 

operates continuously at 80°C and 80% RH, and 

the samples are not exposed to the light. The 

BlueM does not have the same known 

acceleration factor as the WOM, but from 

experiments the acceleration factor may be as 

high as roughly 10X WOM.) For the copper-free 

constructions, the addition of epoxy and 

polyurethane back protection appears to be a poor 

choice because when these constructions failed, 

they typically failed catastrophically by silver/paint 

delamination. Between the mirrors incorporating 

the new copper-free process, the Glaverbel mirror 

(Belgium) tended to outperform the Naugatuck 

mirror (U.S.) in the mirror matrix experiment. 

However, this could be because, at the time the 

mirrors were acquired, Glaverbel had more 

experience than Naugatuck in manufacturing 

mirrors with the copper-free technique. 

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 in FY 2006 and provided 

copper-free mirror samples for testing with a twocoat, lead-free paint system plus moisture and 

adhesive-resistant back protection, instead of the 

one-coat paint system previously used in its 

manufacturing line. Preliminary exposure testing 

results appear encouraging and testing is ongoing 

(see Fig. 3). 

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. 

Equivalent NREL Exposure Time (years) 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 100 

80 

85 

90 

95

% Hemipherical Reflectance 

APS 

FLA 

NREL 

WOM 

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 

Total UV Dose (100 x MJ/m2) 

Fig. 3. Loss of solar-weighted reflectance of 

Naugatuck thin-glass mirrors with Cu back layer 

and Pb-free paint as a function of APS, FLA, 

NREL, and WOM exposure. 

3.2 Aluminized Mirrors 

Aluminized reflectors use a polished aluminum 

substrate, an enhanced aluminum reflective layer, 

and a protective oxidized topcoat. The major 

concern has been poor durability of such materials 

in urban and industrialized (polluted) locations. An 

improved anodized aluminum mirror incorporated 

a protective polymeric overcoat onto aluminized 

aluminum. However, the specularity degraded with 

outdoor exposure at Arizona, Florida, and 

Colorado (NREL) and with accelerated exposure 

in the WOM. Alanod stopped selling this material 

in FY 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 FY 2005 are undergoing 

testing. Alanod reintroduced the product for sale 

as Miro-Sun in early FY 2006, and 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%. Preliminary exposure testing 

results appear encouraging and testing is ongoing 

(see Fig. 4). Alanod is now working to develop a 

silvered solar reflector likely to be called MiroSilver. 

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 Equivalent NREL Exposure Time (years) 

0 1 2 

40 

50 

60 

70 

80 

90 

100 

0.0 1.1 2.2 3.3 4.4 5.6 6.7 

Total UV Dose (100 x MJ/m2) 

% Reflectance 

NREL - 25 mr 

NREL - 7 mr 

NREL - SWV 

APS - 25 mr 

APS - 7 mr 

APS - SWV 

WOM - 25 mr 

WOM - 7 mr 

WOM - SWV 

Sandia -25mr

Fig. 4. Loss of solar-weighted reflectance, 25­

and 7-mradian specular reflectance at 660 nm of 

Alanod Miro-Sun aluminized reflectors as a 

function of APS, NREL, and Sandia outdoor 

exposure and accelerated WOM exposure.

3.3 Silvered Polymer Reflectors 

A polymeric solar reflector was developed through 

collaborative research with ReflecTech. In 

FY 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 solarweighted 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 after the equivalent of 

10 years of accelerated outdoor exposure in 

ACUVEX (natural sunlight in Phoenix, AZ, 

concentrated seven to eight times with a Fresnelreflector while samples are cooled with a fan to 

near-ambient conditions and sprayed with 

deionized water 8 minutes per natural sun hour). 

However, WOM results showed significant 

reflectance loss earlier than anticipated. Prototype 

materials to test modifications to the baseline 

construction were produced. These tests were 

successful in identifying changes to the baseline 

construction that dramatically improved the WOM 

durability of the reflective film. Some of these 

improvements were then incorporated into a new 

pilot plant production run delivered late FY 2004; 

initial hemispherical and specular reflectivity were 

low due to a vacuum problem during the 

manufacturing process. ReflecTech produced and 

delivered samples from its most recent pilot-plant 

production run (ReflecTech [06-48,06-60]) with 

improved hemispherical and specular reflectivity in 

the second quarter of FY 2006; the durability 

testing is ongoing (see Fig. 5). The ReflecTech 

material is being field-tested at SEGS and 

SolarGenix Power Roof system and has been 

installed in 685 mirror modules on a JX Crystals 

100-kW

manufac

 CPV project in China. Other

turers have expressed an interest. 

 solar 

0 1 

Equivalent NREL Exposure Time (years) 

2 3 4 5 6 7 8 

70 

75 

80 

85 

90 

95 

100 

% Hemispherical Reflectance

UV-Screen/SS95-NREL 

ReflecTech A-NREL 

ReflecTech B-NREL 

UV-Screen/SS95-WOM 

ReflecTech A-WOM 

ReflecTech B-WOM 

0 3.3 6.6 9.9 13.2 16.5 19.8 23.1 26.4 

Total UV Dose (100 x MJ/m2) 

Fig. 5. Loss of solar-weighted reflectance of 

ReflecTech prototype, initial pilot run, and mostpromising variation to baseline construction as a 

function of outdoor exposure in Colorado and 

accelerated WOM exposure. 

Progress has been made on advanced solar 

reflector research, but development work has 

been severely limited based on a lack of funding. 

Durability testing of reflectors supplied by industry 

is ongoing. Glass, ReflecTech, and Alanod 

mirrors are commercially 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. Recently, the construction of all of 

the 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 2007 Activities 

Continue optical characterization of advanced 

reflector materials, accelerated and outdoor 

testing of commercial and experimental reflector 

materials, and industry support. 

•	 Memo report on testing of thin-glass mirrors 

applied to CSP technologies (03/31/07) 

•	 Summary report of status of reflector 

materials. (08/31/07) 

5. Major FY 2006 Publications 

Kennedy, C.E.; Terwilliger, K.; and Warrick, A., 

2006, “Summary of Status of Most Promising 

Candidate Advanced Solar Mirrors,” CSP FY 2006 

Milestone Report. 

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____________________________________________________________________________________ 

 

____________________________________________________________________________________ 

 

CSP Systems Analysis 

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 2006 Budgets:	 $520K (NREL), $255K (SNL) 

Objectives 

•	 Provide support for the Concentrating Solar Power (CSP) Subprogram analysis efforts related to 

implementation of 1000 MW of concentrating solar power in the Southwestern United States 

through the Western Governors’ Association (WGA). 

•	 Support CSP-specific analysis related to implementation of the Systems-Driven Approach within 

the DOE Solar Program. 

•	 Support DOE and Energy Information Administration analysis requests on as-needed basis. 

Accomplishments 

•	 Continued analysis in support of the WGA Solar Task Force, with an emphasis on analysis in 

support of a proposed southwest utility consortium. 

•	 Developed geographical information system (GIS)-based tools designed to support requests for 

siting analyzes from public and private institutions. 

•	 Developed initial version of CSP Jobs and Economic Development Impact model. 

•	 Completed development of Concentrating Solar Deployment System market penetration model. 

Future Directions 

The primary activity for the systems analysis task in FY 2007 will be to continue support implementation 

of concentrating solar power in the Southwest. Specific directions will include: 

•	 Providing continued analytical support to WGA Solar Task Force. 

•	 Continuing interactions in the West with Arizona, New Mexico, Nevada, Texas, and Colorado in 

support of developing further CSP opportunities in those states. 

•	 Continuing development of tools (GIS, market analysis, economic impact analysis) for use in 

supporting the activities described above. 

1. Introduction 

The 1000 MW CSP project was initiated in 

FY 2002 based on a Congressional request to 

DOE to investigate the “feasibility of 1000 MW of 

concentrating solar power in the Southwest by 

2006.” The original charge has grown and now 

involves a number of activities including: outreach 

to the Southwestern states; support of state-level 

activities in New Mexico, California, and Colorado, 

and analysis in support of the Western Governors’ 

Association (WGA) 30 GW Clean Energy Initiative. 

The focus of the 1000 MW CSP Initiative is to 

accelerate the commercialization of concentrating 

solar power generation technologies. Analysis 

shows that cost reductions needed for the 

technologies to be competitive in central power 

generation markets will result from a combination 

of R&D advances, system scale-up, and 

learning/deployment. The 1000 MW CSP Initiative 

addresses cost reductions resulting from 

deployment. 

This project links directly to the DOE Energy 

Efficiency and Renewable Energy (EERE) and 

Solar Program 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 

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support the Solar Program’s long-term goal of 

achieving wholesale, central power generation 

from solar energy at costs of $0.05–$0.08/kWhr. 

2. Technical Approach 

The report on the potential of 1000 MW of CSP 

power in the West was completed and submitted 

to Congress in August of 2002. During the 

preparation of this report, DOE formed the 

1000 MW Team with the purpose of educating 

energy offices and professionals on the potential 

of CSP power in the Southwestern states. This 

“road show” sought to provide information on the 

characteristics of CSP technologies, the potential 

in each of the states, and the benefits that would 

accrue from its implementation. In April of 2004 at 

the North American Energy Summit in 

Albuquerque, New Mexico, the Western 

Governors’ Association resolved to evaluate 

diversification of Western energy resources. The 

mechanism for doing this is the 30 GW Clean 

Energy Initiative for the West, which includes a 

declaration to “establish a stakeholder working 

group to develop options for consideration by the 

governors in furtherance of the 1,000 MW 

Initiative.” The April 2004 resolution rolled up the 

1000 MW Initiative under the umbrella of the 

30 GW WGA Study. In FY 2005, we provided 

significant support to the WGA analysis efforts, 

through a combination of in-house and 

subcontracted technical, policy, and market 

analyses. This effort continued in FY 2006 by 

working with the WGA Solar Task Force to 

produce a final draft of the task force report (June 

2006 deliverable), to continue analysis in support 

of task force efforts, and to represent this analysis 

to Southwest stakeholders, with a particular 

emphasis on Arizona where a consortium of 

Southwest utilities, with Arizona Public Service 

(APS) leading the effort, are considering 

collaborating on the development of a large-scale 

(up to 250 MW) CSP project. 

Budget allocations by task are provided below. 

Task Title FY 2006 

Budget ($K) 

1000 MW Initiative Support - NREL $520K 

1000 MW Initiative Support - SNL $255K 

3. Results and Accomplishments 

The technical work plan for FY 2006 focused on: 

(1) Continued support to the WGA Solar Task 

Force 

(2) Analytical support for Southwest stakeholders 

(3) Development of analytical tools to support 

these efforts. 

3.1 Continued Support to WGA Solar Task Force 

•	 Supported completion of a final draft of the 

WGA Solar Task Force report. (see: 

http://www.westgov.org/wga/initiatives/cdeac/ 

Solar-full.pdf) 

•	 Met with state stakeholders, primarily Arizona, 

to provide overview of key WGA Task Force 

findings. 

3.2 Analytical Support to Southwest Stakeholders 

•	 Provided technical support to APS 

development of a Request for Information to 

industry for interest in developing a regional 

Concentrating Solar Power Project. 

•	 Provided analytical support to APS and 

participating consortium utilities on the impact 

of project size, incentives, and financing 

options on the cost of CSP 

3.3 Development of Analytical Tools to Support 

These Efforts 

•	 Completed development of initial phase of 

Concentrating Solar Deployment System 

(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 (see Fig. 1). 

•	 Continued development of in-house GISbased siting tools designed to support public 

(state and local stakeholders) and private 

industry requests for siting analysis (see Fig. 2). 

•	 Developed initial draft of Jobs and Economic 

Development Impact (JEDI) Model. 

Fig. 1. CSP capacity deployment by region in 

2030 based on output from the Concentrating 

Solar Deployment System Model. 

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130
 

 

 

 

 

Fig. 2. GIS siting analysis based on utility request 

for support 

4. Planned FY 2007 Activities 

The activities of this task have resulted in an 

increased awareness of the technologies by 

energy decision makers in the Southwestern 

United States. In FY 2007, we will continue to 

provide analysis in support of stakeholders 

interested in deploying significant levels of CSP in 

the Southwest. 

Specific activities identified in the FY 2007 Annual 

Operating Plan include: 

•	 Support for analysis of transmission issues 

impacting implementation of CSP in the 

Southwestern United States. 

•	 Continued development and subsequent use 

of the CSDS model for investigating the 

impact of policy and cost-reduction scenarios 

on penetration of CSP in the Southwestern 

United States. 

•	 Continued discussions and analysis in support 

of implementing CSP within “Solar 

Development Zones.” 

•	 Continued development of a mapping tools for 

identifying candidate locations for CSP plants. 

•	 Continued development of a JEDI model to 

support analysis of the economic impact of 

CSP for specific locations in the Southwestern 

United States. 

•	 Siting of weather ground stations for key direct 

normal incident resource sites in the 

Southwestern United States. 

5. Major FY 2006 Publications 

Final Report of the Western Governors’ Solar Task 

Force, January 2006. 

Black and Veatch, “Economic, Energy, and 

Environmental Benefits of Concentrating Solar 

Power in California,” Final Report, April 2006, 

NREL Report No. SR-550-39291. 

N. Blair, M. Mehos, W. Short, and D. Heimiller, 

“Concentrating Solar Deployment System (CSDS) 

–A New Model for Estimating U.S. Concentrating 

Solar Power (CSP) Market Potential,” July 2006, 

NREL Report No. CP-620-40525. 

M. Mehos and D. Kearney, “Tackling Climate 

Change in the U.S.: Potential Carbon Emissions 

Reductions from Concentrating Solar Power by 

2030,” presentation at ASES Solar 2007, draft 

report. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2006 

($K) 

Morse Associates, Inc. 

Fred Morse 

Washington, D.C. 

fredmorse@morseassociatesinc.com 

Consulting for government and 

utilities on CSP applications and 

marketing policy 

150 

MRG and Associates 

Marshall Goldbert 

Nevada City, CA 

mrgassociates@earthlink.net Development of CSP JEDI model 8.4 

131

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Solar Thermal R&D

Concentrating Solar Power

132
 

 

 

 

 

Solar Heating and Lighting
 

The Solar Heating and Lighting (SH&L) effort 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. 

The Hybrid Solar Lighting Project is developing an entirely new application of solar power in 

buildings through the use of fiber optic systems that bring sunlight into interior rooms of 

commercial buildings. This technology can improve the quality of indoor lighting with its 

associated benefits in worker productivity, student performance, and shoppers’ buying behavior. 

Following are highlights of SH&L achievements in FY 2006. 

Low-Cost Polymers 

•	 The Davis Energy Group/SunEarth team resolved leak issues for its integral collector storage 

system and developed pilot projects. 

•	 The FAFCO team developed and tested system prototypes and field-tested secondgeneration units. 

Materials Durability 

•	 The ultraviolet stability of a number of new candidate polymeric glazing constructions was 

tested. 

•	 Mechanical creep was measured as a function of temperature and applied stress for two 

candidate absorber materials. 

Industry Manufacturing Assistance 

•	 Deployed a “freeze-protected” roof-integrated collector on a Building America home. 

•	 Published a SAND report that documented the multi-year development of the roof-integrated 

thermosiphon. 

Hy brid Solar Lighting 

•	 Developed real-time, remote monitoring system to record energy use, tracker performance, 

and video data from 13 hybrid solar lighting (HSL) beta sites across the United States. 

•	 Produced a high-quality, long-lasting, 48”-diameter acrylic mirror for use with HSL and 

concentrating photovoltaics applications. 

133

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____________________________________________________________________________________ 

 

 

____________________________________________________________________________________ 

Low-Cost Polymers 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contacts: Jay Burch (NREL), 303-384-7508, jay_burch@nrel.gov 

DOE HQ Technology Manager: Glenn Strahs, 202-586-2305, glenn.strahs@ee.doe.gov 

FY 2006 Budget: $357K (NREL) 

Objectives 

•	 Collaborate with industry teams to reduce the levelized cost of saved energy (LCOE) for solar 

water heaters (SWHs) suitable for mild climates by at least 50%, from ~10¢/kWhth to less than 

~5¢/kWhth in new homes. 

•	 Develop low-cost system concepts that can lower the LCOE for SWH suitable for cold climates by 

at least 50%, from ~12¢/kWhth to less than ~6¢/kWhth in new homes. 

Accomplishments 

•	 Davis Energy Group/SunEarth team: glazed/unglazed polymer integral collector storage (ICS) 

that can achieve 6¢/kWhth: 

o	 Resolved leak issues for the Davis Energy Group/SunEarth SunCache ICS. 

o	 Developed pilot projects. 

•	 FAFCO team: unglazed drainback that can achieve 5¢/kWhth: 

o	 Developed and tested system prototypes. 

o	 Carried out field-testing of second-generation units. 

•	 Demonstrated lowered scale rates in candidate polymers. 

• Cold-climate systems: 

o	 New models and test methods for thermosiphons 

o	 Cold climate thermosiphon system concept development. 

Future Directions 

•	 Continue minor support to industry teams for wider field-testing and product refinement. 

•	 Issue request for proposal (RFP) for conceptual development of low-cost SWH for cold climates 

(if funding available). 

•	 Define most promising solar thermal pathways to attain cost-neutral zero energy homes. 

1. Introduction 

Domestic hot water is a major residential end use 

in the United States, totaling about 2.7 quads/yr 

and averaging about 13% of total residential 

usage nationwide. The LCOE for SWHs is 

currently ~10¢–25¢/kWhth, which ranges based on 

varying solar resource and system cost. System 

cost depends sensitively on the market scenario: 

for retrofits, the cost is 50% to 100% higher than 

for new construction (specific costs quoted herein 

refer to new construction, with LCOE 1.5 to 2 

times that for new construction). LCOE is to be 

compared with an effective gas water heating cost 

of ~3¢/kWhth and electricity cost at ~6¢–25¢/kWhth 

Significant reduction in LCOE is needed for SWH 

to capture significant market share through good 

economics. As detailed further in the DOE Solar 

Technologies Program Multi-Year Technical Plan 

(MYTP) and other studies, high first cost is the key 

barrier to U.S. SWH markets. The Solar Heating 

and Lighting (SH&L) Subprogram set a goal in 

1998 of reducing LCOE for SWH by at least 50%. 

This work started in 1999 and was focused on 

passive systems for mild climates to limit work 

scope, given sustained low funding levels. In 

response to an RFP, five teams were initially 

funded for concept development. After downselection in 2001, two teams were “stage-gated” 

through engineering development to field trials and 

manufacturing development in FYs 2005–2006. 

The two teams are: Davis Energy Group/SunEarth 

(DEG/SE) and FAFCO, Inc. The systems that 

have resulted from this partnership are shown in 

current form in Figs. 1–4. Each team intends to 

market several variations of its system, including 

glazed and unglazed versions. 

Solar Thermal R&D

Solar Heating and Lighting

134
Fig. 1. Schematic of DEG/SE glazed ICS. An 

immersed heat exchanger carries pressurized 

potable water. 

Fig. 2. DEG/SE glazed ICS on field test in 

Sacramento, CA. 

Fig. 3. DEG/SE unglazed unit. The unit is easily 

carried by one person. 

Fig. 4. Schematic of an unglazed drainback 

Support at NREL for the industry teams involved 

public domain work common to the teams, 

including: materials durability testing, modeling 

and testing, pipe freeze protection, overheat 

protection, immersed heat exchangers (modeling, 

testing, polymer tubing durability, and scaling). 

2. Technical Approach 

The technical strategy to achieve low costs 

includes: (1) use low-cost polymer materials and 

manufacturing technology; (2) simplify system 

designs and installation, exploiting the light weight 

and formability of polymers. The management 

approach is to contract with solar industry teams in 

public-private partnerships that leverage private 

industry innovation and manufacturing abilities 

with national laboratory and university expertise in 

modeling, testing, and materials. 

The project’s meager resources and limited solar 

industry resources are severe handicaps to 

developing successful low-cost polymer systems. 

The average budget for low-cost SWH at NREL 

has been about one-tenth of what DuPont 

allocated for its polymer collector work. With the 

hope of attracting polymer processors with added 

resources for product development, an effort was 

made to publicize the potential of polymer solar 

systems to the broad polymer industry through 

publications at national conferences and in trade 

journals. 

135

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Solar Heating and Lighting
 

 

 

 

 

 

 

 

 

 

With the polymer strategy comes new opportunities 

but new problems. A key problem is polymeric 

materials durability, given harsh environmental 

stresses and the occasional high system 

temperatures during stagnation events under no-load 

conditions. Accelerated testing is needed to identify 

workable materials in a timely fashion, and this has 

been done at NREL and at the University of 

Minnesota. NREL concentrated on identifying and 

testing candidates for glazings and absorbers. 

Materials work is described more fully in the SH&L 

project description Materials Durability. The 

University of Minnesota has focused on heat 

exchangers, including modeling/testing, and lifetime 

and scaling issues in polymer tubing suitable for 

polymer heat exchangers. 

The 2006 MYTP called for initiating development 

of low-cost, cold-climate SWHs in FY 2007. 

Freeze-protected thermosiphons as in Fig. 5, with 

their inherent cost and reliability advantages, could 

reach LCOE of 4¢/kWhth. However, risk of freeze 

damage and catastrophic burst of supply/return 

piping has been a showstopper. To encourage 

industry to consider such designs, NREL has been 

working for several years to establish freeze 

protection methods for the supply/return piping, 

including both primary and fail-safe backup 

protection. Another barrier to low-cost, 

unpressurized cold-climate thermosiphons is that 

modeling is generally unavailable for most 

configurations, making design and optimization 

difficult and dictating the need for costly system 

tests to develop “effective” rating models at Solar 

Rating and Certification Corporation (SRCC). 

Aux 

Tank 

Mains Inlet 

Supply piping 

Return piping 

Collector 

To drain 

Freeze Protection 

Valve located HERE! 

House load 

Storage 

Fig. 5. An indirect thermosiphon system is shown, 

with a freeze-protection valve for primary freeze 

protection. 

Modeling/design of heat exchangers has been 

subcontracted to the University of Minnesota, 

which has supported the teams in their heat 

exchanger designs and tested prototypes. 

Compared to copper heat exchangers, polymer 

heat exchangers have the potential to lower costs 

and weight. Use of lower-strength commodity 

plastics for heat exchangers drives the design to 

small diameters (reducing hoop stress). However, 

oxidation and subsequent polymer degradation 

becomes a more serious issue with thin walls. 

Antioxidant life must be at least 10 years. Scale 

buildup is also a concern, and these issues are 

also being addressed through testing and 

modeling. 

3. Results and Accomplishments 

Both industry teams plan to bring their low-cost 

SWH designs to market in 2007. The DEG/SE 

team refined its design and developed pilot 

installations and detailed marketing and 

manufacturing approaches. DEG/SE redesigned 

its unglazed collector mounting to eliminate leaks 

developing with that mounting. DEG/SE has been 

developing pilot projects with the Sacramento 

Utility District, migrant housing authorities in 

California, and Building America. 

In FYs 2005–2006, the FAFCO team found 100% 

leakage failures in its previous direct system with a 

glazed polymer collector. In FY 2006, FAFCO 

changed its system type from a glazed, 

pressurized system (which NREL strongly 

recommended not pursuing in FY 2004) to an 

unpressurized drainback system with an unglazed 

polymer flat-plate collector. FAFCO developed fullscale prototypes, held successful field trials, and 

made plans to formally introduce the system in 

February 2007 at the National Association of 

Home Builders show. To attract potential 

development from polymer processors, four 

papers on polymer solar thermal systems (two 

from NREL) were presented at the annual 

technical conference of the Society of Plastics 

Engineers (ANTEC2006). 

To allay cold-climate thermosiphon freeze 

concerns and potentially extend indirect 

thermosiphons to the entire United States, PEX 

supply/return potable water piping can serve as a 

fail-safe backup to any primary pipe freeze 

protection. To see if unsubstantiated claims of 

freeze tolerance are true, four brands of PEX 

piping were subjected to freeze-thaw cycling. Two 

of the four brands proved to be resilient against 

freeze-thaw beyond 450 cycles, as long as 

configurations promoting non-uniform freezing 

were avoided. Pipe freeze tolerance was 

confirmed by complementary stress-strain data at 

0o

C, as in Fig. 6. 
 

 

 

0

0.2

0.4

0.6

0 1 2 3 4 5 6 7

Time (weeks)

0

0.2

0.4

0.6

0 1 2 3 4 5 6 7

Time (weeks)

 PP Tubes

□ Cu Tubes

 PP Tubes

□ Cu Tubes

 

 

Another barrier to cold-climate thermosiphons has 

been the lack of models for innovative systems, 

inhibiting design optimization and forcing more 

costly ratings. New thermosiphon models for 

TRNSYS (TRaNsient SYstem Simulation 

Program) based on a general routine for inference 

Ca (10-3 mol/m2)

(PO4) (10-3 mol/m2)

0 

0.2 

0.4 

0.6 

Ca (10-3 mol/m2 ) 

0 

0.2 

0.4 

0.6 

(PO4 ) (10-3 mol/m2 

 PP Tubes )

□ Cu Tubes 

 PP Tubes 

□ Cu Tubes 

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 of convection loop mass flow rate have been Time (weeks) Time (weeks) developed, although oscillations at reasonable 

time-steps need to be resolved before industry Fig. 7. Calcium carbonate and calcium phosphate

and SRCC use. Standard TRNSYS types for scale rates on copper (open symbols) and polymer

collectors and tanks with immersed heat tubes (filled symbols).

exchangers are used, enabling efficient 

4. Planned FY 2007 Activities 

4.1 Industry Teams 

development of system models. To determine 

accuracy of models based on component testing 

only, component and system tests were performed 

for three innovative thermosiphon systems, and DEG/SE will continue to monitor field installations

normal operation data over 6 weeks were taken and seek other low-volume opportunities for pilot

for validation. The results demonstrate that when projects. Design refinement will continue, including

only components are tested, the resulting 

TRNSYS system models predicted measured 

normal-operation performance within 5%, even 

when the flow rate was not accurately predicted. 

This insensitivity of performance to flow rates 

(well-known in active systems) was corroborated 

by simulations, in which the flow was varied up to 

a factor of 10 from the base case, with variation 

less than 4%. 

Fig 6. Stress versus strain for five samples of a 

silane-based PEX. A quasi-linear region without 

significant permanent deformation exists for the 

hoop strain from uniform freeze. 

Progress has been made on the issues with 

potential polymer heat exchangers. The University 

of Minnesota has developed and validated a 

model for antioxidant depletion. It predicts 

antioxidant concentrations over time based 

primarily on molecular diffusion data. Scaling in 

the small-diameter heat exchanger tubing can 

choke off flow in scale-prone waters. Data on 

scale rates at high, but realistic, supersaturation 

have shown that polymer tubing initially scales 

less rapidly than copper tubes, as in Fig. 7. 

a simpler heat exchanger design and a more 

impact-resistant acrylic glazing. FAFCO will 

continue to monitor field-test results and refine its 

drainback models, with a glazed version under 

development. 

4.2 Polymer Industry Outreach 

A session on polymers in solar thermal is being 

organized for ANTEC2007. NREL will present a 

paper on materials testing, along with University of 

Minnesota papers. NREL has been asked to 

produce an article in 2007 on the potential market 

for polymers in solar thermal in the industry journal 

Modern Plastics, widely read by polymer industry 

executives. 

4.3 Solar Thermal for Zero Energy Home 

The SH&L Subprogram mission has shifted from 

supporting the development of low-cost solar 

water heaters to supporting the development of 

“cost-neutral” solar thermal pathways to zero 

energy homes, in collaboration with the DOE 

Building America Program. (Cost neutral means 

the system cost savings just offsets the extra 

mortgage cost). Homes on the path from code 

minimum to zero energy improve shell and HVAC 

first, and then look to install solar water heaters at 

about the 50% savings level. Although it makes 

great sense to develop lower-cost systems 

suitable for cold climates, a previously planned 

RFP for development of cold-climate systems will 

not be issued unless DOE specifically provides 

funds for this initiative from FY 2007 funds. For 

aggressively approaching zero energy, solar 

thermal systems that provide water heating, space 

heating, and space cooling (triple play) deserve 

close consideration, to determine if the extra 

collector/storage can be cost neutral. Annual 
 

 

 

 

 

 

storage schemes, that can produce high solar 

fractions for triple-play systems will be 

investigated. A concept for a unity-solar-fraction 

solar thermal system based on liquid desiccants 

will also be analyzed for its potential feasibility. 

5. FY 2006 Special Recognitions, Awards, and 

Patents 

The NREL article on polymer-based solar thermal 

systems was highlighted in the January edition of 

the SPE Highlights. The DEG/SunEarth SunCache 

system is being submitted for an R&D 100 Award 

in FY 2007. 

6. Major FY 2006 Publications 

Burch, J., Shoukas, G., Brandemuhl, M., and 

Krarti, M., “Modeling and Test-and-Rate Methods 

for Innovative Thermosiphon Solar Water 

Heaters,” Proc. ASES 2006. 

Burch, J., Heater, M., Brandemuhl, M., and Krarti, 

M., “Northward Market Extension for Passive Solar 

Water Heaters by Using Pipe Freeze Protection 

with Freeze-Tolerant Piping,” Proc. ASES 2006. 

Burch, J., Heater, M., Brandemuhl, M., and Krarti, 

M., “Pipe Freeze Prevention for Passive Solar 

Water Heaters Using a Room-Air Natural 

Convection Loop,” Proc. ASES 2006. 

Burch, J., “Polymer-based Solar Thermal 

Systems: Past, Present, and Potential Products,” 

Annual Technical Conference of the Society of 

Plastic Engineers, ANTEC2006. 

Burch, J., “High Temperature Issues for Polymerbased Solar Thermal Systems,” Annual Technical 

Conference of the Society of Plastic Engineers, 

ANTEC2006. 

7. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2006 

($K) 

Cost 

Share 

($K) 

Davis Energy Group/SunEarth 

Dick Bourne 

Davis, CA 

dbourne@davisenergy.com 

Field monitoring of 10 systems, 

codes, leak elimination 751 45 

FAFCO, Inc 

Mike Rubio 

Chico, CA 

mrubio@fafco.com 

Refine new designs, test 

prototypes 0 3002 

University of Minnesota 

Jane Davidson 

Minneapolis, MN 

jhd@me.umn.edu 

Stratification, pipe materials 

testing, and scaling rates 501 4003 

Thermal Energy System 

Specialists, Inc. 

Jeff Thornton 

Madison, WI 

thornton@tess-inc.com 

Develop TRNSYS and TRNSED 

models in support of industry 

teams 

504 0 

SRCC 

Jim Huggins 

Cocoa, FL 

huggins@fsec.ucf.edu 

Rating and certification of solar 

thermal collectors and systems 3185 0 

Notes: 

1. Funded with prior year funds. 

2. All work has been funded internally at FAFCO. 

3. High degree of co-funding through university and state grants devoted to solar thermal. 

4. Open contract through FY 2007, funds allocated in 2005. 

5. Funded through the Golden Field Office from SH&L funds. 
 

 

 

 

____________________________________________________________________________________ 

 

 

 

 

____________________________________________________________________________________ 

 

 

Materials Durability 

Performing Organization: National Renewable Energy Laboratory (NREL) 

Key Technical Contact: Gary Jorgensen, 303-384-6113, gary_jorgensen@nrel.gov 

DOE HQ Program Manager: Glenn Strahs, 202-586-2305, glenn.strahs@ee.doe.gov 

FY 2006 Budget: $150K 

Objectives 

•	 Identify alternative polymeric glazing and absorber materials/constructions that will allow design 

trade-offs that can help reduce the costs associated with solar domestic hot water systems. 

•	 Perform materials testing to demonstrate whether such candidate polymers will meet the 

durability requirements for real systems.
 

Accomplishments 

•	 The ultraviolet (UV) stability of a number of new candidate polymeric glazing constructions was 

tested. 

•	 The impact strength of several candidate glazing materials has been measured as a function of 

UV exposure time. 

•	 Mechanical creep was measured as a function of temperature and applied stress for two 

candidate absorber materials.
 

Future Directions 

•	 Provide support for industry partners, including investigation of thin-film glazings. 

•	 Provide support for standards development, including hail testing of evacuated tube collectors. 

•	 Continue long-term testing and evaluation of candidate polymeric glazing and absorber materials. 

1. Introduction 

Improved polymeric glazing and absorber 

materials are required to increase the reliability of 

cost-effective solar collectors. As discussed in the 

DOE Solar Program Multi-Year Technical Plan, a 

major impediment to development of low-cost 

solar water heating systems is the uncertainty in 

durability of polymeric components. 

Both passive solar water heating and active coldclimate solar water heating technologies require 

polymeric glazings and absorbers to survive in 

harsh operating environments. The objectives of 

this research are to: (1) identify alternative 

polymeric materials/constructions that will allow 

design trade-offs that can help reduce the costs 

associated with solar water heating (SWH) 

systems and (2) perform materials testing to 

demonstrate whether such candidate polymers will 

meet the durability requirements for real systems. 

This task complements and supports the Low-Cost 

Systems Development/Low-Cost Polymers 

activities. Materials are evaluated and 

recommended to private-sector partners for use 

with their prototype systems. We also test 

materials that are of interest to the project’s 

subcontractors. 

2. Technical Approach 

The primary property of interest for candidate 

polymeric materials is the ability to avoid optical 

and mechanical degradation (yellowing and 

embrittlement) during exposure to elevated 

temperatures and UV light. A number of candidate 

glazing constructions have been subjected to 

photothermal weathering using three 

complementary forms of exposure. These include 

outdoors, in laboratory-controlled accelerated 

weathering chambers, and at NREL’s unique UVconcentrator facility. Optical transmittance and 

mechanical impact strength are measured as a 

function of exposure time and conditions. 

To assess the mechanical stability of candidate 

polymeric absorber materials, creep is measured 

as a function of temperature and applied stress. 

139

Solar Thermal R&D

Solar Heating and Lighting
 

 

 

 

 

3. Results and Accomplishments 

The major results and accomplishments of the 

project during FY 2006 include the following: 

•	 The optical and mechanical durability of a 

number of candidate glazing materials was 

quantified. (09/06) 

•	 A creep-compliance master curve was 

generated for two candidate polymeric 

absorbers of interest to a private sector 

company planning to manufacture collector 

systems using these materials. (09/06) 

3.1 Glazing Materials 

Based on accelerated screening tests, we have 

found that fluoropolymers and acrylic are UV 

weatherable, and all other polymeric glazing 

materials tested lose transmittance and yellow. 

However, fluoropolymers are relatively expensive 

and realistically would be limited to use as thin-film 

glazings. Acrylic tends to be too brittle and exhibits 

thermal sag, which is a concern for a glazing 

candidate for solar collector applications. We have 

also found that polycarbonate (PC) laminated to 

an acrylic UV-screening film (Korad®

, a product of 

Polymer Extruded Products) can also be UV 

weatherable. The most promising construction 

uses a UV-screening film that is adhesively 

laminated to a PC sheet. Without the additional 

UV-screening layer, PC products exhibit 3%–5% 

loss in solar-weighted hemispherical transmittance 

after about 2–3 years’ equivalent exposure. In 

addition, severe visual yellowing (an aesthetic 

concern) occurs in the same timeframe. With the 

addition of a UV-screening film, significant loss in 

hemispherical transmittance does not begin until 

between 10–15 years’ equivalent outdoor 

exposure at elevated operating temperatures. 

Interactions were held with material suppliers to 

identify several new types of polymeric glazing 

materials. A company that is a major supplier of 

PC sheet is interacting with Polymer Extruded 

Products to provide thermally bonded UVscreening film/PC samples. The UV screening 

layer is thicker than previously used (0.08–0.15 

mm thick, rather than 0.05 mm thick), and 

enhanced screening films (that provide twice as 

much UV absorption as previously tested) are 

incorporated into their laminate samples. Two 

major polymer manufacturers have supplied 

samples in which UV-absorbing organic clear 

coats are applied to PC sheet. Such constructions 

are used in automotive headlamp applications. If a 

UV screening film cannot be thermally bonded to 

PC sheet as it is extruded, and/or cannot avoid 

severe adverse thinning during thermoforming, 

then clear coats could be applied to thermoformed 

PC to avoid such damaging effects to the 

screening agent. 

Prospective solar manufacturers are also 

considering non-PC glazing materials, including 

impact-modified acrylic (IMA) and fiberglassreinforced polyester. Solar-weighted 

transmittances for some of these more recent 

samples are shown in Fig. 1. Most of these 

materials are maintaining optical performance 

after a cumulative UV dose equivalent to about 5 

years outdoor exposure in Miami, FL. 

75 

76 

77 

78 

79 

80 

81 

82 

83 

84 

85 

Solar-Weighted Hemispherical Transmittance

Impact Modified Acrylic 

Company B; Material 1 

Company A; Material 2 

Fiber Reinforced Polyester 

5-yr 

Miami, 

FL 

0 5 10 15 20 25 30 35 

UVB Dose (MJ/m2) 

Fig. 1. Solar transmittance as a function of UVB 

dose for candidate glazing polymeric materials 

exposed at NREL’s UV concentrator at 70°C. 

Impact strength of several candidate glazing 

materials has also been measured as a function of 

exposure time in our XR-260 weatherometer. 

Figure 2 shows a loss in transmittance for 

unscreened PC as the samples yellow. Impact 

strength also degrades. However, the impact 

strength of PC was substantially greater than for 

IMA. The initial impact strength for 2.3-mm-thick 

PC was 32.1 ± 0.25 J, whereas the unweathered 

value for 2.2-mm-thick IMA was 0.17 ± 0.03 J. 

Furthermore, IMA lost ~25% impact strength in 

less than 1 year equivalent outdoor exposure. The 

behavior upon impact of these two glazing 

materials was also quite different. The PC 

generally failed by cracking around the perimeter 

of permanently deformed dimples, whereas the 

IMA typically cracked or shattered at the impact 

site without any plastic yield. 

Solar Thermal R&D

Solar Heating and Lighting

140
 

 

 

 

 

 

 

 

 

 

30 

35 

0.000 

0.010 

0.020 

0.030 

0.040 

0.050 

0.060 

0.070 

ε(t) 

Material B 

Material A 

20 Years 

ε(t) = D(t) * σr = A * (t/aTaσ)

n * σr 

aT = exp[-C1(T-Tr)/(C2+T-Tr)] 

aσ = exp{-C3[(σ-σr)/σr]

2

 - C4(σ-σr)/σr} 

Tr = 82°C σr = 2.31 MPa 

83 •	 Continue long-term testing and evaluation of 

1 Year 82 in Miami, FL 

candidate polymeric absorber materials. 

(09/07) 

Impact Strength (J) 25 81 

20 80 

15 79 

PC Impact Strength (J) 10 78 

Transmittance (%) 

5 Impact-Modified Acrylic 77

Impact Strength (J) 

0 76 

0 500 1000 1500 2000 2500 3000 3500 4000 

Time of Exposure (h) 

Solar-Weighted Hemispherical Transmittance (%) 

Fig. 2. Effect of UV exposure on impact strength 

and transmittance of 2.3-mm-thick polycarbonate 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07 1.E+09 1.E+11 1.E+13 

glazing. 

3.2 Absorber Materials 

Industry partners have identified two absorber 

materials that we have tested, namely, 

polypropylene (PP), including PP random 

copolymer (PPR), and metallocene-based multidensity polyethylene (MBMDPE). Creep is an 

important concern for absorber materials. Severe 

deformations can result in elevated stress 

concentrations that can result in cracking. If 

absorber bulges reach the glazing, then thermal 

performance is catastrophically compromised. 

Creep has been measured for both MBMDPE and 

PPR. Results for MBMDPE were previously 

reported. For PPR, samples of two materials (A and 

B) were tested at 82°C/2.3 MPa (the reference 

conditions), 100°C/2.3 MPa, 100°C/3.4 MPa, 

75°C/3.4 MPa, and 110°C/2.8 MPa. The data sets 

were then used to derive transformation equations 

to allow extrapolation to extended times at the 

reference conditions, as shown in Fig. 3. The 

resulting strain values after 20 years service are 

about 2.7% for material A and 3.8% for material B 

at the design reference conditions. Significant 

surface oxidation was also visible for material B 

during the creep measurements. 

4. Planned FY 2007 Activities 

The most significant activities planned for FY 2007 

include: 

•	 Continue testing UV stability of new candidate 

polymeric glazing constructions including thin 

films. (09/07) 

•	 Provide support for development of standards 

for hail testing of evacuated tube collectors. 

(09/07) 

Time (s) 

Fig. 3. Strain for PPR obtained from creep 

compliance master curve for reference conditions 

of 82°C and 2.3 MPa. 

5. FY 2006 Special Recognitions, Awards, and 

Patents 

The World Intellectual Property Organization 

granted an Australian patent (#2001238405): Gary 

J. Jorgensen and Allan A. Lewandowski, UltraAccelerated Natural Sunlight Exposure Testing 

Facilities, August 28, 2006. 

6. Major FY 2006 Publications 

G. Jorgensen, K. Terwilliger, C. Bingham, C. 

Lundquist, and M. Milbourne, “Durability of 

Polymeric Glazing and Absorber Materials,” DOE 

Solar Energy Technologies Program Review 

Meeting, Denver, CO, November 2005. 

M. Köhl, G. Jorgensen, S. Brunold, B. Carlsson, M. 

Heck, and K. Möller, “Durability of polymeric glazing 

materials for solar applications,” Solar Energy, 79, 

No. 6, December 2005, pp. 618–623. 

G.J. Jorgensen, K.M. Terwilliger, and C.E. 

Bingham, “Durability of Polymeric Glazing and 

Absorber Materials,” Presented at the Solar 2006 

35th ASES Conference, Denver, CO, July 8–13, 

2006. 

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____________________________________________________________________________________ 

 

 

 

 

Industry Manufacturing Assistance 

Performing Organization: Sandia National Laboratories (SNL) 

Key Technical Contact: Greg Kolb, 505-844-1887, gjkolb@sandia.gov 

DOE HQ Technology Manager: Glen Strahs, 202-586-2305, glenn.strahs@ee.doe.gov 

FY 2006 Budget: $90K (FY 2006) + $6.5K (FY 2005 Carryover) = $97K 

Objectives 

•	 Help solar thermal manufacturers improve their products. 

•	 Help solar technology users design their systems to achieve maximum cost effectiveness. 

Accomplishments 

•	 Deployed a “freeze-protected” roof-integrated collector on a Building America home. 

•	 Helped the manufacturer of a “non-freeze protected” roof-integrated thermosiphon (RITH) solve 

technical problems and obtain Solar Rating and Certification Corporation (SRCC) certification. 

•	 Published a SAND report that documented the multi-year development of the RITH. 

•	 Helped the University of New Mexico establish a solar energy R&D program. 

•	 Provided technical assistance to the SRCC and several other solar users and manufacturers. 

Future Directions 

•	 Continue to work with Building America and Artistic Homes to test a freeze-protected roofintegrated system. 

•	 With NREL, define role of solar hot water systems within zero energy homes. 

1. Introduction 

Sandia National Laboratories (SNL) provides 

technical assistance to the solar thermal industry. 

Through its Industry Assistance Program, SNL 

follows a Systems-Driven Approach to help 

manufacturers improve their products. In addition, 

the program helps potential technology users 

design their systems to achieve maximum cost 

effectiveness. This assistance is often highly 

leveraged with funding from the U.S. Department 

of Defense (DoD) and the utility industry. 

2. Technical Approach 

Solar thermal technology users and manufacturers 

make a formal request to SNL for technical 

assistance. Guidelines for making this request are 

described on the program Web site 

(www.sandia.gov/Renewable_Energy/solarthermal 

/Center/index2.htm). Assistance is given on a “first 

come, first served basis” to government agencies 

and to the private sector. Proposed project 

activities must not compete with those offered in 

private industry. 

3. Results and Accomplishments 

Budget allocation during FY 2006 was very limited. 

This allowed us to complete projects begun in 

FY 2005 and to provide limited technical 

assistance to manufacturers and users. No new 

R&D projects were started. The main areas of 

activity are described below. 

3.1 Deployed a Freeze-Protected Roof-Integrated 

Collector Project 

Roof integration is popular with both builders and 

architects. Roof integration solves many 

objections for adopting solar hot water systems 

that have been raised in the past by builders. The 

advantages of roof integration include much 

improved aesthetics, a reduction in the number of 

roof penetrations, and the ability to replace/repair 

a roof without removing the solar collectors. In 

FY 2006, SNL worked with the Building Science 

Corporation to deploy a roof-integrated design that 

is capable of operating in a freezing climate. The 

drainback method was selected as the preferred 

method of achieving freeze protection. 

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A demonstration system was installed on a 

Building America high-efficiency home (by Artistic 

Homes) in Los Lunas, New Mexico. The system 

was flashed into the roof instead of on top of the 

roof, which has been the tradition for the past 30 

years. SNL engineers designed an energy 

monitoring system and provided it to Artistic 

Homes. Data collection began in June 2006. 

A system price goal of $2,000 has been set, given 

a production scenario of several hundred per year. 

If this price can be achieved, the system will be 

cost effective for sunny locations in which natural 

gas is >$1/therm; the system can be included in 

the home mortgage and be paid off by the 

resultant energy savings. 

If the demonstration is successful and predicted 

costs are reasonable, Artistic Homes could offer 

solar hot water as an appliance option to 

homebuyers. 

3.2 Helped RITH Manufacturer Achieve SRCC 

Certification 

The RITH is a “non-freeze-protected” solar hot 

water system for the new-home market. The 

collector is the same as installed in the Building 

America project described above, but the design 

of the remainder of the system is totally different. 

Unlike the drainback system, the RITH has no 

pumps and water is circulated through the 

collector by natural circulation caused by placing 

the solar tank inside the attic above the elevation 

of the collector, i.e., the thermosiphon effect. 

In FY 2005, RITH failed its SRCC certification test 

because of leaks caused by faulty welds. In 

FY 2006, SNL worked with the RITH manufacturer 

(Energy Laboratory Incorporated) to solve the 

technical problems that precluded certification. 

Welding issues were resolved and the unit was 

resubmitted to SRCC in early 2006. The unit 

passed the retest and was certified in August 

2006. 

The final report that describes the multi-year RITH 

development effort was published. 

3.3 Helped the University of New Mexico Establish 

a Solar Energy Program 

During FY 2006, the University of New Mexico 

Mechanical Engineering Department (UNM/ME) 

was awarded a grant from the State of New 

Mexico to design, build, and operate a solar airconditioning testbed. SNL was a principal advisor 

to the UNM/ME team in developing the grant 

proposal and was instrumental in the design of the 

plan that was proposed and was funded. 

The grant covers the cost of new collectors, a 10-

ton absorption chiller, all of the associated balance 

of system components, and the labor to design 

and install the testbed. The testbed will be used 

for graduate and undergraduate studies and will 

produce chilled water for the UNM/ME building, 

where the system will be installed. 

The UNM/ME faculty will be offering, for the first 

time in nearly 20 years, solar engineering courses 

in upcoming semesters, eventually developing 

solar engineering degree programs at both 

graduate and undergraduate levels. 

3.4 Provided Technical Assistance to the Solar 

Rating and Certification Corporation 

SRCC is the solar hot water industry’s certifying 

organization for systems and collectors. SRCC 

has only a few paid positions and overhead costs. 

Historically, DOE has supported SRCC with about 

one-quarter million dollars per year. However, 

most of the organizational activities involve 

volunteer labor, most of it professional, supplied 

by the industry and supporting organizations. 

SRCC depends on the involvement of high-quality 

assistance from the national laboratories to 

continue to conduct its business in a professional 

manner. 

In FY 2006, SNL supported SRCC by chairing the 

Standards Committee and serving as technical 

liaison between the labs and SRCC. The 

Standards Committee meets monthly via 

conference call, with appropriate subcommittees 

meeting more frequently as needed. The chair is 

an ex-officio member of each subcommittee and 

often attends these meetings. Typically, the 

committee considers detailed technical information 

concerning testing and certifying collectors and 

systems and often involves technical analysis and 

supporting information. 

In addition, SNL provides critical guidance in the 

development of a strategic marketing plan for 

SRCC as a whole. 

3.5 Other Industry Assistance Activities 

We provided solar thermal assistance to several 

organizations that contacted us through our Web 

site. The major organizations and the help 

provided are included in the table below. 

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4. Planned FY 2006 Activities 5. Major FY 2006 Publications 

•	 Continue to work with Building America and Menicucci, D. F, T. A. Moss and G. E. Palomino, 

Artistic Homes to test a freeze-protected roof- The Development of a Roof Integrated Solar Hot 

integrated system. Water System, SAND2006-5529, Sandia National 

•	 With NREL, define role of solar hot water Laboratories, Albuquerque, NM, September 2006. 

systems within zero energy homes. . 

6. University and Industry Partners 

The following are the major organizations that received assistance during FY 2006. 

Organization/ 

Principal Investigator Location/e-mail or Phone Description/Title of Research Activity 

Building Science 

Corporation 

Mark Sevier 

Westford, MA 

mark@buildingscience.com 

Install freeze-protected roof-integrated solar hot 

water project for Building America. 

University of New Mexico 

Andrea Mammoli 

Albuquerque, NM 

mammoli@me.unm.edu Help develop solar R&D program. 

Energy Laboratory Inc. 

Mike Newman 

Jacksonville, FL 

mike.newman@solarenergy.com Resolve welding issues. 

SRCC 

Jim Huggins 

Cocoa, FL 

huggins@fsec.ucf.edu Aid the standards committee. 

City of Tucson 

Vinnie Hunt 

Tucson, AZ 

vajra@vecat-inc.com Develop a solar HVAC monitoring strategy. 

U.S. Air Force 

Patrick Pfaltzgraff 

Washington, DC 

ppfaltzgra@law.gwu.edu 

Perform research study to estimate potential of 

solar on military bases. 

Concurrent Designs 

Jim Smith 

Austin, TX 

512-869-0904 Provide info on 2-axis solar drives. 

Shell Oil 

Aina Abayomi 

Houston, TX 

Aina.Abayomi@shell.com 

Help with study for trough application in 

Bakersfield, CA. 

Quest Energy Group 

Jeremy Rivera 

Durango, CO 

970-247-3120 Provide info for solar swimming pool heat project. 

David Erickson 

Sonoma County 

Sonoma County, CA 

jdaviderickson@comcast.net 

Discuss feasibily/economics of possible district 

heating system. 

SENTECH 

Douglas Hinrichs 

Bethesda, MD 

DHINRICHS@sentech.org Review solar HVAC report. 

Puget Sound Energy 

Stephen Emmert 

Seattle, WA 

Stephen.emmert@pse.com Advise on solar tower applications. 
 

 

 

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Hybrid Solar Lighting 

Performing Organization: Oak Ridge National Laboratory (ORNL) 

Key Technical Contact: Melissa Lapsa, 865-576-8620, lapsamv@ornl.gov 

DOE HQ Technology Manager: Glenn Strahs, 202-586-2305, glenn.strahs@ee.doe.gov 

FY 2006 Budget: $220K 

Objectives 

•	 Deploy two beta-test units in Texas and California. 

•	 Deploy two beta-test units at ORNL for R&D and continued test and evaluation. 

•	 Develop real-time monitoring hardware for Sunlight Inside Initiative beta sites. 

•	 Report on benefits associated with 2005 Sunlight Inside Initiative describing energy savings and 

user feedback. 

Accomplishments 

•	 Developed real-time, remote monitoring system to record energy use, tracker performance, and 

video data from 13 hybrid solar lighting (HSL) beta sites across the United States. 

•	 Began evaluation of beta-testing data to be fully reported in FY 2007. Early data show nearly 70% 

peak energy savings at beta sites. 

•	 Produced a high-quality, long-lasting, 48”-diameter acrylic mirror for use with HSL and 

concentrating photovoltaics (CPV) applications. 

•	 Fully deployed one HSL beta-unit (HSL3100) at the Sacramento Utility District (SMUD)
 

headquarters in Sacramento, CA. 

•	 Partially installed one HSL beta unit at WalMart’s experimental store in McKinney, TX (completion 

expected by end of February 2007). 

•	 ORNL researchers were recognized in 2006 with an R&D 100 Award for the HSL system. These 

awards are presented annually by R&D Magazine in recognition of the year's most significant 

technological innovations. 

Future Directions 

•	 R&D on larger 64”-diameter primary mirror 

•	 Reporting on benefits associated with “Sunlight Inside Initiative” beta sites. 

•	 Integration of PV and CPV technology with existing platform. 

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 this 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 the sunlight itself 

(e.g., it fluctuates in intensity and can be highly 

directional, producing glare and unwanted 

heating). A significant market exists for a natural 

lighting product that can offer the benefits of 

natural lighting 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, there exists 20 billion square feet of 

commercial space that meets the requirements for 

implementation of an HSL system. Each year, this 

amount of applicable space grows by 600 million 

square feet of new construction. 

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Commercialization of HSL technology will initially 

focus 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, greater market 

penetration into this niche market and the larger 

commercial building market (including office 

buildings) is anticipated. Full-spectrum solar 

energy systems, such as HSL, provide a new and 

realistic opportunity for wide-ranging energy, 

environmental, and economic benefits. Their 

development is directly in line with the mission of 

the DOE Solar 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. 

Advantages of HSL include: 

•	 Small and minimal roof penetrations, reducing 

the potential for leaks. 

•	 Infrared and ultraviolet energy in sunlight is 

separated from the visible light, rather than 

being transmitted into buildings. Heating, 

ventilation, and air-conditioning (HVAC) loads 

are thus reduced by 5% to 10% compared to 

electric lighting systems. 

•	 Ready adaptability to commercial buildings 

with multiple stories, relatively low ceiling 

heights, and interior walls. A single system 

can distribute enough sunlight to co-illuminate 

several rooms in a typical office building. 

•	 No need for large portions of precious plenum 

space—the area between the roof and 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. 

•	 Easily incorporated into existing building 

designs (for retrofit markets), and the optical 

fibers can 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 

Research in HSL technology for FY 2006 was 

aimed at field-testing the developed technology 

while also conducting R&D to increase system 

performance and flexibility. Beta-testing at various 

sites across the United States—such as in hot, 

cold, wet, or dry climates—was expected to reveal 

flaws and limitations in the solar collector design 

that would be evaluated and remedied. Two 

ORNL-supervised beta sites at WalMart (in 

McKinney, TX) and SMUD Headquarters (in 

Sacramento, CA) were planned to educate the 

public about the technology and to evaluate 

installation challenges associated with the 

technology. A real-time, remote monitoring 

system was to be developed to monitor energy 

data from these two site, two prototyping units at 

ORNL, and 10 additional sites throughout the 

United States to provide a good survey of the 

current design year-round performance. 

In addition to beta-testing, a third-party market 

potential analysis was planned to gauge the 

commercial market size and characteristics for the 

technology. The benefits of the HSL activity were 

prioritized as (1) light quality, (2) reduction of 

waste heat compared to other lighting systems, 

and (3) fossil energy conserved by using solar 

energy for lighting applications. Unfortunately, due 

to budget limitations, this analysis was begun by 

Antares, Inc., but was discontinued pending 

additional funding. 

3. Results and Accomplishments 

In June 2006, the first HSL beta-site installation 

was completed at San Diego State University. 

Through the rest of 2006, an additional eight sites 

were installed by ORNL’s commercialization 

partner, Sunlight Direct. Additional units were 

jointly installed by ORNL and Sunlight Direct at 

SMUD Headquarters in Sacramento, CA, and an 

experimental Walmart store in McKinney, TX 

(expected to be completed in early 2007). 

In addition to the beta sites, two prototype HSL 

units were installed at ORNL. One has been used 

for HSL testing and demonstration while another is 

being configured for CPV applications. 

All beta-testing and prototyping units were 

equipped with a custom-designed monitoring 

system that allows the energy savings associated 

with the units to be remotely monitored. A cellular 

connection allows a high-bandwidth connection to 

each site and provides energy data, tracker control 

and diagnostics, and video feedback to be 

transferred back to ORNL. 

Early assessments of the beta-testing data show 

that the tracker platforms are performing very 

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reliably with only two known instances of tracker 

interruption (which were corrected remotely by 

Sunlight Direct within 24 hours). In addition, 

energy-savings data appears as expected, 

although additional data evaluation and reporting 

will be required before issuing a final assessment 

of the technologies energy-savings potential. 

Figure 1 shows actual energy data from San 

Diego State University’s beta site, demonstrating 

the potential of the technology to deliver significant 

energy savings during the peak daylight hours. 

Technical design flaws in the current HSL solar 

collector were identified early in the beta-testing 

effort and were corrected on later models that 

went into beta-testing. These flaws included: 

(1) Zenith bearing seal deficiencies 

(2) Tracker axle coupling slippage under high 

wind loading 

(3) Fiber heating due to contaminants. 

These issues were all corrected in the field and 

addressed in the production of later beta 

installations. Initial response to the technology has 

been positive and the technology has been featured 

in a number of popular publications in 2006. 

In addition to the beta-testing effort, ORNL has 

been working to further increase the functionality 

and performance of the HSL technology and 

components. Significant efforts went into 

continuing the development of a high-quality 48”-

diameter, thermoformed acrylic mirror for the HSL 

technology. In 2006, the quality of the mirror 

continued to improve and is close to rivaling glass 

alternatives. ORNL continues to push the state of 

the art in accurate acrylic thermoforming for solar 

imaging applications. 

Fig. 1. Actual data from 2006 Sunlight Inside BetaTesting Initiative 

Accomplishments: 

•	 Developed real-time, remote monitoring 

system to record energy use, tracker 

performance, and video data from 13 HSL 

beta sites across the United States. 

•	 Began evaluation of beta-testing data to be 

fully reported in FY 2007. Early data show 

nearly 70% peak energy savings at beta sites. 

•	 Produced a high-quality, long-lasting, 

48”-diameter acrylic mirror for use with HSL 

and CPV applications. 

•	 Fully deployed one HSL beta-unit (HSL3100) 

at SMUD headquarters in Sacramento, CA. 

•	 Partially installed one HSL beta unit at 

WalMart’s experimental store in McKinney, TX 

(completion expected by end of February 

2007). 

Fig. 2. One of 13 installed HSL beta units 

4. Planned FY 2007 Activities 

The greatest technical challenges/barriers 

remaining for the HSL project are: 

(1) Reliability of the 2-axis tracking mechanism 

(2) Sustained performance of the collection optics 

and optical fibers 

(3) System cost 

(4) System integration for other solar applications. 

Great progress has been made in improving the 

reliability of the HSL tracking mechanism and 

control electronics in recent years. However, 

smarter controls that use feedback sensors and 

self-learning algorithms and improved mechanical 

designs combined with extensive testing of the 

HSL tracker are needed to further improve the 

system’s reliability and lifetime. Tracker 

improvements that provide improved survivability 

and stability at high wind speeds, an improved 

tracking resolution of 0.05° in both axes, a selfcalibrating controller, and a tracker with an 

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integrated Web server to allow remote monitoring 

and servicing are key improvements that have 

been identified. 

Significant advances have already been made in 

the quality and cost of the plastic optical 

components used with the HSL technology. 

Despite these technical advances, the optical 

performance of the acrylic mirror is still not as high 

as desired. Variations in the shape of the mirror 

result in a large focal spot that has limited the 

collection efficiency of the HSL system and 

contributed to heating in the optical fibers. In 

FY 2007, we will improve the optical quality of the 

48” mirror by implementing a real-time 2D 

temperature control system to more uniformly heat 

the thermoformed plastic. Doing so is expected to 

consistently produce a plastic mirror that rivals the 

performance of early glass mirrors and has a focal 

spot of less than 1.0 cm. In addition, we will scale 

up this fabrication process and the associated 

molds to accommodate a larger 64”-diameter 

mirror that can collect twice as much light as the 

current design. The larger mirror design will 

increase the illumination area of a system from 

1,000 to 2,000 sq. ft., thereby reducing the cost 

per square foot by nearly 40%. With the 

development of a new, larger, primary mirror that 

will allow the current HSL system to increase its 

illumination area from 1,000 to 2,000 sq. ft. will 

also come the need to extend the optical fiber 

length (to allow full coverage of the 2,000-sq. ft. 

area). The goal of the FY 2007 effort will be to 

develop a 1.5”-diameter optical fiber bundle with 

65% transmission after 65 ft. costing less than 

$1,000. Research will continue toward improving 

the performance of the plastic optical fibers by 

studying the microscopic optical loss mechanisms 

present in commercially available PMMA optical 

fibers. R&D efforts will be conducted with an 

emphasis on investigating available postprocessing techniques that could improve fiber 

performance. 

To address the above technical issues and to 

conduct our market assessment, a budget of $2M 

is requested for FY 2007. 

FY 2007 Milestones: 

•	 Complete design and implementation of 

improved tracker controller and fiber receiver 

module. 

•	 Work with commercialization partner to reduce 

COGS (cost of goods sold) by 50% per square 

foot over FY 2006 levels. 

•	 Report on benefits associated with 2006 

Sunlight Inside Initiative describing energy 

savings and user feedback. 

3rd • Complete Party Market Assessment of 

Hybrid Solar Lighting. 

•	 Technical report/paper on long-term 

improvements and applications of the base 

HSL platform. 

5. Major FY 2006 Publications 

Melissa Lapsa, “Hybrid Solar Lighting,” oral 

presentation, U.S. Green Buildings Council Middle 

Tennessee Chapter Meeting, Nashville, TN, July 

27, 2007. 

Christina Ward, “Innovative Hybrid Solar Lighting 

Reduces Waste Heat and Improves Lighting 

Quality,” oral presentation and paper, Solar 2006 

Conference, July 11, 2007. 

Steve Allison, “Hybrid Solar Lighting Provides 

Energy Savings and Reduces Waste Heat,” oral 

presentation and paper, World Energy 

Engineering Congress, September 13, 2006, 

Washington, D.C. (part of a Federal Energy 

Management Session titled “Leading by Example: 

Examining New Energy Efficient Technologies for 

Federal Buildings"). 

Press Coverage: 

•	 "Hybrid Solar Lighting Technology... Soon to 

shine on the commercial scene!" Electrical 

Line Magazine, September/October 2006, 

Volume 12, Number 5. 

•	 "Vote Solar Initiative: How to Break Down 

Barriers to Solar, New Solar Hybrid Lighting 

Hits Select Retail Stores For Testing," 

Renewable Energy Access, Aug. 31, 2006. 

•	 "ORNL Spin-Off Beta Tests Hybrid Solar 

Lighting, EE Times, Portland, OR, Aug. 21, 

2006. 

•	 "Hybrid Solar Lighting Gaining Momentum 

around Nation," Renewable Energy Assess, 

Aug. 15, 2006. 

•	 "ORNL Hybrid Lighting Technology Gaining 

Momentum around Nation," The Oak Ridger, 

Oak Ridge, TN, August 7, 2006. 

6. FY 2006 Special Recognitions, Awards, and 

Patents 

ORNL researchers received an R&D Magazine 

R&D 100 Award for the HSL system. The system 

uses a roof-mounted solar collector and small fiber 

optics to transfer sunlight to hybrid fixtures with 

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electric lamps. A control system enables sunlight could be particularly valuable in areas where there 

to power the light and illuminate about 1,000 is an abundance of sunshine. The Hybrid Lighting 

square feet during sunny daylight hours while Team is composed of David Beshears, Melissa 

clouds and darkness allow the system to revert to Lapsa, Art Clemons, Dennis Earl, John Jordan, 

providing regular electrical light. Randall Lind, Curt Maxey, Jeff Muhs, Christina 

Ward, and Wes Wysor. The late Larry Dickens 

HSL reduces energy usage not only for lighting, was ORNL's commercialization manager on the 

but also for cooling due to the system’s ability to project. John Morris of Sunlight Direct is also a 

block ultraviolet and infrared heat. The technology member of the team. 

7. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2006 

($K) 

University of Tennessee 

Rao V. Arimilli 

Knoxville, TN 

arimilli@utk.edu 

Wind loading modeling conducted 

by a graduate student and 

professor on acrylic mirror design 

27 

Antares 

Christian Demeter 

Landover, MD 

cdemet@antaresgroupinc.com Market assessment 10 

Bennett Mirrors 

Alastair Bennett 

Tauranga, New Zealand 

alastair@bennettmirror.com Produced prototype acrylic mirrors 5 

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Systems Integration and Coordination 

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. The team also provides leadership and support for various Solar Program activities, 

such as development of the DOE Solar Program Multi-Year Program Plan (MYPP) and the 

Systems-Driven Approach to program management. 

Some significant accomplishments in FY 2006 are listed below. 

Systems-Driven Approach 

•	 Provided analytical support to the Solar America Initiative, including writing a number of 

internal white papers, preparing presentation materials, drafting documents related to the 

Technology Pathway Partnership Federal Opportunity Announcement. 

•	 Analyzed the potential for very large-scale solar PV deployment in the United States. 

Communications and Outreach 

•	 Completed five annual core documents for the Solar Energy Technologies Program. 

•	 Managed key components of, and staffed the, 2005 Solar Decathlon; participated in critical 

lessons learned, selection, and planning activities for the 2007 Solar Decathlon. 

International Activities 

• Published the Solar International Activities: Strategic Plan and adopted relevant elements of 

plan as SAI Market Transformation 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." 

Process Integration, Capital Equipment, and Facilities 

•	 At the Science and Technology Facility (NREL): performed project management and 

engineering development leading to the delivery, acceptance, and operation of an inter-tool 

transport pod to move samples between tools in a controlled ambient (high vacuum). 

Achieved successful transfer of samples between the stand-alone tool for transparent 

conducting oxides and the transport pod. 

•	 At the National Solar Thermal Test Facility (SNL): completed preliminary testing of a 

theoretical overlay photographic trough alignment approach on the trough rotating platform. 

151 Systems Integration and Coordination
Systems Integration and Coordination 152
 

 

 

 

 

 

____________________________________________________________________________________ 

 

 

 

 

 

 

Systems-Driven Approach 

Performing Organizations: National Renewable Energy Laboratory (NREL)

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Joe Tillerson (SNL on detail to DOE, Primary Contact), 202-586-1495, 

joe.tillerson@ee.doe.gov 

Chris Cameron (SNL), Paul Gilman (NREL), Charles Hanley (SNL), 

Robert Margolis (NREL), Mark Mehos (NREL), David Mooney (NREL) 

DOE HQ Technology Manager:	 Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2006 Budgets:	 $990K (NREL), $610K (SNL) 

Objectives 

•	 To develop and apply a market-driven, validated, user-friendly, analytical framework for
 

determining research priorities within the DOE Solar Program, including the following: 

o	 Analysis – To improve the analytical basis for understanding the system and policy drivers of 

solar technologies in various markets. 

o	 Benchmarking – To benchmark current system, component, and subcomponent 

performance and cost to provide validated input to the Systems-Driven Approach (SDA) 

model and to validate SDA model output. 

o	 Modeling – To develop a user-friendly solar energy systems model that will allow program 

managers and others users to investigate the impact of variations in physical, cost, and 

financial parameters to inform R&D and design decisions. 

Accomplishments 

•	 Analysis 

o	 Provided analytical support to the Solar America Initiative (SAI), including writing a number of 

internal white papers, preparing presentation materials, drafting documents related to the 

Technology Pathway Partnership (TPP) Federal Opportunity Announcement (FOA). 

o	 Provided training and assistance to SAI TPP applicants with respect to using the Solar 

Advisor Model (SAM). 

o	 Analyzed potential for very large-scale solar PV deployment in the United States. 

•	 Benchmarking 

o	 Established a cost basis for PV systems in the three market sectors of the Solar America 

Initiative, which was used as a starting point for TPP developments. 

o	 Defined reference systems and their parameters as input to SDA models and the DOE Solar 

Program Multi-Year Program Plan. 

o	 Provided data and analytical input to the SETP Posture Plan and a planned update of the 

Multi-Year Program Plan. 

•	 Modeling 

o	 Developed and released version (June 30, 2006) of Solar Advisor Model for use by SAI 

bidders and reviewers. 

o	 Developed documentation for SAM and held SAM workshop (July 25, 2006) for potential SAI 

bidders. 

o	 Supported external review/validation of SAM by Strategen. 

o	 Completed utility-scale, independent power producer (IPP) finance modeling option (upgrade 

to previously developed model). 

o	 Added user defined variable capability to allow flexibility in modeling nonstandard variables 

(variables modeled through linkages with Excel spreadsheets). 

o	 Enhanced parametric analysis capability to include parameterization of non-numeric variables 

(e.g., climate, tracking type, financing type, depreciation schedule) and to include 

parameterization of user-defined variables. 

153 Systems Integration and Coordination
 

 

 

____________________________________________________________________________________ 

 

 

 

 

 

 

o	 Continued improvements to model functionality for photovoltaic (PV) and concentrating solar 

power CSP cost and performance algorithms and interface in response to internal and 

external users. 

Future Directions 

In FY07 and beyond, these SDA activities will be more integrated as the Solar Program implements SAI 

and develops closer cooperation with the industry-led TPPs. Thus, as SDA becomes more intrinsic 

throughout the Solar Program, activities will focus more on development of needed tools for SAI and 

industry partners, and less on the establishment of a process for program implementation. 

•	 Analysis 

o	 Continue work on analysis of long-term benefits of solar energy. 

o	 Continue to carry out policy analysis in support of the Solar Program, in particular, to help 

provide context for SAI R&D planning. 

•	 Benchmarking 

o	 Work with TPPs and other partners to establish a basis for tracking progress of their technical 

developments on the basis of levelized cost of energy (LCOE). 

o	 Develop a means to input future revisions to benchmarks that will facilitate TPP reporting, 

such as a Web-based database. 

•	 Modeling 

o	 Add capability for modeling Federal, state, and local incentives (performance-based 

incentives, capacity-based incentives, investment-based incentives, and investment and 

production tax credits) for residential, commercial, and utility-scale PV and CSP systems. 

o	 Add additional utility finance options (e.g., investor-owned utility, municipal utility). 

o	 Add capability of analyzing time-dependent valuation of PV and CSP output. 

o	 Complete refinement and integration of solar only, solar w/ storage, and solar w/ hybrid 

parabolic trough performance and cost models. 

o	 Begin development of dish/Stirling performance model w/ linkage to program-developed cost 

model. 

1. Introduction 

The DOE Solar Program began the formulation of 

a Systems-Driven Approach (SDA) to R&D 

portfolio management and prioritization with a 

workshop held in December 2002. The DOE Solar 

Program Multi-Year Program Plan (MYPP) states 

that “we have implemented the use of our 

Systems-Driven Approach to guide us through 

difficult programmatic options and to make sound 

decisions considering limited resources.” The SDA 

provides a framework for program planning that 

supports this objective. Under the tasks described 

below, data and tools are being developed and 

applied to support the use of SDA in decisionmaking by program management. The SDA team 

works closely with other projects, especially the 

PV Systems Analysis Project. During FY 2006, 

the work under this task was focused specifically 

on supporting the implementation of the Solar 

America Initiative (SAI). 

2. Technical Approach 

The SDA is the basis for the multi-step planning 

process used in the Solar Program for portfolio 

decision-making. The SDA allows us to assure 

that all technical targets for R&D on the 

components and systems funded through the 

Solar Program are derived from a common market 

perspective and national goals, and the resultant 

technologies are tested and validated in the 

context of established criteria for each market. 

The key steps in the decision-making process are: 

• Identifying technology improvement 

opportunities and analyzing impact on LCOE 

•	 Assessing research activity contributions to 

technology improvement 

•	 Developing a multi-year research portfolio 

• Assessing progress. 

Analysis, benchmarking, and modeling activities 

are the three primary components of the SDA 

efforts. In FY 2006, activities focused primarily on 

new PV modeling capabilities and associated 

applications directly in support of the SAI. 

Task Title FY 2006 

Budget ($K) 

Analysis 430 

Benchmarking 610 

Modeling 560 

Systems Integration and Coordination 154
 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.1 Analysis 

Analysis is used to establish a sound basis for 

understanding the system and policy drivers of 

solar technologies in various markets. Results 

from analysis activities are linked to the broader 

SDA process and provide a market context for the 

benchmarking and modeling efforts. 

We are developing long-term, market-penetration 

projections for solar technologies by examining 

both 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 program’s economic and 

environmental benefits. Existing models, such as 

MARKAL and the Energy Information 

Administration (EIA) National Energy Modeling 

System (NEMS), are used to carry out analysis, 

and feedback is provided on how to improve the 

representation of solar technologies in these 

models. New models, such as the Solar 

Deployment Systems (SolarDS) model, are also 

being developed. This model analyzes the market 

penetration of PV on buildings in the United States 

under different policies and rate structures. 

We are also reviewing the feasibility of achieving 

the program’s technical and economic targets. 

This task examines proposed research goals 

given technical, funding, and other constraints. 

Here, our emphasis is on reviewing the existing 

literature on cost and performance projections, 

drawing on experts from both within and outside 

the solar community to review detailed technology 

cost models, and grounding the program’s targets 

in real-world experience. In addition, value 

analyses are completed in which we evaluate 

policies, as well as other factors, that impact the 

value of solar energy technologies in various 

markets. 

In carrying out these tasks, we utilize resources at 

NREL and SNL, as well as subcontracts (as 

described below in Section 6). 

2.2 Benchmarking 

With the development and initiation of the Solar 

America Initiative during this year, much of the 

benchmarking effort of the SDA was transitioned 

into supporting this initiative through the provision 

of underpinning data and analyses. Specific 

efforts contributed to the achievement of the 

planned milestones for this task area, including: 

•	 Providing leadership and technical support to 

the several industry Technical Exchange 

Meetings that took place during the year, in 

Chicago, Washington, D.C., and San 

Francisco, and the compilation of results 

reports that directly fed the development of the 

FOAs for SAI. 

•	 Contribution of materials for the Solar Program 

Posture Plan, to prepare for its release and 

publication in early FY 2007. 

•	 Provide support and verification of the 

baseline cases in the Solar Advisor Model, 

which was released for use in TPP 

applications. 

•	 Contribute to the development of the MultiYear Program Plan, and then to revisions, 

based on sound data collection and analysis. 

•	 Define and communicate the stage-gate 

process for technical development in the 

context of Solar America Initiative. 

•	 Contribute to the development of the TPP 

FOA and additional announcements as part of 

the SAI Market Transformation activities. 

2.3 Modeling 

The primary function of the Solar Advisor Model 

(SAM) 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. The model is intended for use 

by DOE and laboratory management and research 

staff in implementation of the SDA to program 

planning. The model is also intended to support 

members of the solar industry to inform internal 

R&D direction and to estimate systems cost and 

performance, in particular, as required in the TPP 

FOA process. 

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, 

which 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 

the particular user. 

Subcontracted work, listed in Table 6, includes 

Paul Gilman (model documentation and training), 

Steven Janzou (model code development), and 

the University of Wisconsin (TRNSYS support and 

model code development). 

155 Systems Integration and Coordination
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3. Results and Accomplishments 

3.1 Analysis 

During FY 2006, a major emphasis of the analysis 

effort was to provide a wide range of technical and 

analytical support to help implement the SAI. Two 

examples include providing support to the SAI 

Technical Exchange Meeting (TEM), held in 

Chicago during April 2006, and helping to develop 

the TPP Funding Opportunity Announcement. 

With respect to the TEM, tasks included writing 

white papers, preparing presentation materials, 

organizing planning and strategy reviews, 

providing breakout facilitation, and documenting 

results from the meeting. With respect to 

developing the TPP FOA, tasks included drafting 

major technical sections of the FOA and 

supplemental material, developing evaluation 

processes and criteria, establishing technical 

requirements, identifying technical support 

activities, integrating industry feedback from the 

TEM, and incorporating review comments. 

In addition, improving our understanding of the 

long-term market potential for solar technologies 

has been an important part of our analysis task. 

For example, SolarDS is being developed to 

examine sensitivity of PV market share to PV 

capital cost and performance, rate structures, 

competition with other distributed-generation 

technologies, tax and environmental policies, 

storage and load controls, and financing options 

and consumer choice. 

3.2 Benchmarking 

As stated above, the results of the integrated SDA 

activities provided the analytical basis for the Solar 

America Initiative and several of its related 

documents. This included further documentation 

of past efforts. For example, an appendix was 

prepared for the Multi-Year Program Plan that 

discussed in detail the system-level analyses 

portrayed in the document. This appendix was not 

published, because soon after the release of the 

MYPP, the program management decided that the 

document needed extensive revision. 

In addition, investigations were conducted to 

further understand the cost elements for balanceof-system components and installation steps for 

residential PV systems. These studies involved 

extensive Web-based investigations and 

interviews with several PV system suppliers 

across the United States. This information has 

been compiled in an Excel workbook, and further 

review will be done to determine how best to 

incorporate it into the Solar Advisor Model. 

3.3 Modeling 

In the SAI’s Technology Pathway Partnership’s 

Funding Opportunity Announcement that was 

released in June, applicants were required to 

project the impact of their proposed improvements 

on the PV system’s LCOE. While they could use 

any model of their choosing to calculate LCOE, 

they were encouraged to use the Solar Advisor 

Model and were informed that SAM would be used 

in the review process to verify their LCOE claims. 

In conjunction with the release of the FOA, SAM 

was also made available for download in late June 

from the SAI Web site. Leading up to the due date 

for applications, which was in October, about 300 

people had downloaded SAM. To support this 

activity, a one-day training workshop was held at 

NREL in July with about 35 attendees. 

Ultimately, 55 applications were accepted for 

review under the FOA. All 55 applicants had 

downloaded and utilized SAM in calculating their 

LCOE baselines and the impacts of their proposed 

improvements on LCOE. 

The first step in the technical review of the 

application involved the formation of a FOA 

Technical Committee (FTC). FTC members, who 

were versed in the use of SAM, looked at each of 

the 55 applications and input the relevant values 

from the applications into SAM in order to validate 

the applicant’s LCOE projections. Reports of 

these validation runs were generated and made 

available to the FOA Merit Review Committee for 

its consideration in the overall review of the 

applications. SAM will continue to be utilized in the 

technical monitoring of the selected TPPs in order 

to track progress toward LCOE targets. 

In conjunction with, and following release of SAM 

for use within the SAI framework, the SAM 

development team continued to refine and 

improve the SAM functionality. SAM was updated 

to support enhanced parametric analysis by 

adding the capability to parameterize non-numeric 

input variables (e.g., climate, tracking type, finance 

type). In addition, the development of userdefined variables will provide users with greater 

analytical flexibility by allowing them to investigate 

the impact of parameters not predefined in the 

models graphical user interface. 

Systems Integration and Coordination 156
 

 

 

 

 

 

 

4. Planned FY 2007 Activities 

4.1 Analysis 

During FY 2007, the analysis team will continue to 

support the implementation of the Solar America 

Initiative. In particular, this work will emphasize 

improving our understanding of the long-term 

market potential for solar technologies and 

continuing to review the program’s technical and 

economic targets, as follows: 

•	 Developing better approaches for evaluating 

the benefits and costs of achieving the SAI 

targets (for example, related to employment, 

energy, and environmental benefits). 

•	 Continue to carry out technology and policy 

analysis in support of the Solar Program, in 

particular, to help provide context for SAI R&D 

planning. 

•	 Continue to assess progress toward meeting 

the program's long-term goals. 

4.2 Benchmarking 

As the SAI implementation ramps up with industryled TPPs, benchmarking will support several 

activities, including: 

•	 Establishing and verifying baselines regarding 

PV system cost and performance with the 

TPPs, to facilitate technical program tracking 

and stage-gate reviews. 

•	 Continuing to lead the establishment of 

system-level program metrics to help 

determine technological program impacts on a 

broad, industry-wide level. 

•	 Developing a standard, Web-based means of 

inputting and summarizing such baselines, to 

allow TPPs and DOE management greater 

and easier access to technical information. 

•	 Participating in modeling team activities and 

contributing to the development of new 

analytical tools, for the benefit of both Solar 

Program management and the various players 

in the U.S. PV industry. 

In FY 2007 and beyond, these activities will be 

coordinated throughout the task areas in the 

Annual Operating Plan and will not be limited to 

only the SDA task area. 

4.3 Modeling 

The capability of the SDA model will be expanded 

and applied, as follows: 

•	 Addition of capability to analyze the impact of 

incentives (performance- and capacity-based) 

and tax credits (investment and production) on 

the cost of energy delivered from PV and CSP 

systems. 

•	 Addition of time-dependent valuation of 

generation from PV and CSP systems. 

•	 Inclusion of addition utility-scale project 

finance models (investor owned and 

municipal). 

•	 Refinement of parabolic trough system cost 

and performance models and initial 

development of a dish/Stirling system 

performance model. 

5. Major FY 2006 Publications 

Blair, Nate, Christensen, Craig, Mehos, Mark, 

Janzou, Steve, (2006), "Cost and Performance 

Solar Analysis Model for All Solar Technologies," 

(ISEC2005-76207), Solar Engineering 2005: 

Proceedings of the 2005 International Solar 

Energy Conference (ISEC2005), 6–12 August 

2005, Orlando, Florida. New York: American 

Society of Mechanical Engineers, pp. 225-228; 

(NREL TP CP-620-38049). 

Denholm, Paul, and Robert M. Margolis, “Very 

Large-Scale Deployment of Grid-Connected Solar 

Photovoltaics in the United States: Challenges and 

Opportunities,” paper presented at Solar 2006, 

Denver, CO, July 9–13, 2006. 

Denholm, Paul, Ken Zweibel, and Robert M. 

Margolis, “Tackling Climate Change in the U.S.: 

The Potential Contribution from Solar 

Photovoltaics,” paper presented at Solar 2006, 

Denver, CO, July 9–13, 2006. 

Margolis, Robert M., Richard Mitchell, and Ken 

Zweibel. “Lessons Learned from the Photovoltaic 

Manufacturing Technology/PV Manufacturing R&D 

and Thin-Film PV Partnership Projects. Golden, 

CO: National Renewable Energy Laboratory, 

NREL Technical Report (NREL/TP-520-39780), 

September 2006. 

Margolis, M. Robert, and Jarett Zuboy, 

“Nontechnical Barriers to Solar Energy Use: 

Review of Recent Literature.” Golden, CO: 

National Renewable Energy Laboratory, NREL 

Technical Report (NREL/TP-520-40116), 

September 2006. 

Perez, Richard, Robert Margolis, Marek Kmiecik, 

and Marc Perez, “Update: Effective Load Carrying 

Capability of Photovoltaics in the United States,” 

paper presented at Solar 2006, Denver, CO, 

July 9–13, 2006. 

157 Systems Integration and Coordination
 

 

 

U.S. Department of Energy, Solar Energy Wiser, Ryan, Mark Bolinger, Peter Clappers, and 

Technologies Program Multi-Year Program Plan Robert Margolis, “Letting the Sun Shine on Solar 

2007–2011, DOE Office of Energy Efficiency and Costs: An Empirical Investigation of Photovoltaic 

Renewable Energy, Washington, D.C., January Cost Trends in California,” Golden, CO: National 

2006. Renewable Energy Laboratory, NREL Technical 

Report (NREL/TP-620-39300), January 2006. 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2006 

($K) 

Energy Strategy 

Associates, LLC. 

Gerry Braun 

Damestown, MD 

gbraun12@comcast.net 

Experience scaling up 

manufacturing of emerging 

photovoltaic technologies, Part 2 

14 

Paul Gilman Washington, DC 

paulgilman@earthlink.net 

Documentation and training for 

solar analysis tools 37 

Janzou Consulting 

Steve Janzou 

Evergreen, CO 

steve@janzouconsulting.com 

Provide coding support for 

advisor model development 125 

University of Wisconsin 

Madison 

Sandy Klein 

Madison, WI 

klein@engr.wisc.edu 

CSP parabolic trough plant 

model, and support for 

TRNSYS/SAM integration. 

64 

Systems Integration and Coordination 158
 

 

 

 

 

 

 

 

 

 

____________________________________________________________________________________ 

 

 

Communications and Outreach 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Sandia National Laboratories (SNL)

 DOE Golden Field Office (DOE/GO) 

National Energy Technology Laboratory (NETL)
 

Key Technical Contacts: Don Gwinner (NREL), 303-384-6570, don_gwinner@nrel.gov

 Susannah Pedigo (NREL), 303-384-6624, susannah_pedigo@nrel.gov 

Terry Wilson (SNL), 505-844-6830, tcwilso@sandia.gov 

Glenn Doyle (DOE/GO), 303-275-4706, glenn.doyle@go.doe.gov 

DOE HQ Technology Managers: Robert Hassett, 202-586-8163, robert.hassett@ee.doe.gov 

 Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

FY 2006 Budgets: $570K (NREL), $132K (SNL), $300K (DOE/GO and NETL) 

Special Budget Note:	 Communications and outreach activities related to the Solar Decathlon 

(2005 and 2007 events) are discussed in this section of the report, but 

the funding for those activities is captured in the Building-Integrated 

Photovoltaics section. 

Objectives 

•	 Focus on innovative ways to reach critical audiences and improve business performance—get 

the right information to the right people at the right time in the right form. 

•	 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. 

•	 Use communications products and activities to inform and persuade audiences, move them to 

action, and help overcome barriers for particular technologies and applications. 

Accomplishments 

•	 Completed five annual core documents for the Solar Energy Technologies Program (SETP). 

•	 Played a key role in the Solar Program Review Meeting. 

•	 Participated in IEA Photovoltaic Power Systems Programme, Task 1. 

•	 Supported efforts for the publication of about 400 technical publications. 

•	 Maintained, expanded, and/or developed 12 Web sites. 

•	 Employed visual display and design expertise, creating products such as 3-D animations, kiosks, 

posters, and displays for a variety of products. 

•	 Created and/or staffed several exhibits. 

•	 Managed key components of, and staffed the, 2005 Solar Decathlon (took place in FY 2006). 

•	 Participated in critical lessons learned, selection, and planning activities for the 2007 Solar 

Decathlon. 

•	 Provided critical and timely support to SETP for the Solar America Initiative (SAI). 

•	 Supported the 2005 National Solar Tour. 

Future Directions 

•	 Plan and conduct activities for Core Program Support including development and distribution of 

annual SETP programmatic documents; maintaining, improving, and/or developing 10–15 Web 

sites; editing/processing for publication about 400 technical manuscripts; producing a 

concentrating solar power (CSP) overview publication; and supporting the CSP 1000 MW 

initiative. 

•	 Participate in merit reviews, support management at DOE, GO, and NREL of the task, and 

develop a plan for communications activities associated with the Solar America Showcases/City 

159 Systems Integration and Coordination
 

____________________________________________________________________________________ 

 

 

 

 

Strategic Partnerships Documentation, State Technical Outreach, and Utility Technical Outreach 

tasks. 

•	 Conduct all planning and implementation activities for the communications and outreach tasks for 

Solar Decathlon 2007, which will actually occur in FY 2008. 

1. Introduction 

Advances made through the DOE Solar Program 

must be communicated effectively to appropriate 

audiences if further technical and market growth 

will occur. In FY 2006, the Solar Communications 

Team implemented strategies and tactics on 

behalf of the Solar Program to generate 

awareness of solar energy technologies, the 

research activities, and the potential for solar 

energy technology advances. 

These strategies and tactics were set forth in our 

strategic communications plan developed in 

FY 2004 and refined in FY 2005. At that time, our 

communications efforts were realigned to 

integrate communications across the various solar 

technologies and minimize redundancy; better 

target audiences and messages; respond better to 

changes in markets, technology perceptions, 

audiences, and funding; develop communication 

projects within the context of other relevant plans; 

leverage limited resources; and cultivate a multiyear mentality. 

The planning approach includes eight key 

audiences and their perceptions of solar 

technologies; audience-specific messages and 

communication objectives and strategies; and 

communications tactics (projects) to reinforce the 

objectives. 

The Solar Communications Team’s primary 

objective is to get the right information to the right 

people at the right time in the right form. The 

team develops, or assists in developing, a wide 

range of products, including technical reports, 

conference papers, journal articles, proceedings, 

brochures, fact sheets, presentations, posters, 

databases, exhibits, displays, Web sites, and 

CDs, as well as programmatic pieces such as the 

Solar Program Overview, Annual Report, and 

Multi-Year Program Plan. 

2. Technical Approach 

Our planning efforts evolved from the following 

simple objectives: 

•	 Represent the Solar Program appropriately. 

•	 Save money by reducing duplication of effort 

among separate subprograms. 

•	 Brand all communications and outreach 

products and activities in a consistent and 

appropriate manner. 

Our team views core activities within four primary 

areas: 

Planning. Activities associated with strategic 

planning, budgeting, and aligning with the 

Systems-Driven Approach while working on the 

transition to alignment with the Solar America 

Initiative. 

Developing and producing. Activities associated 

with creating and producing a variety of 

communications products, including print, Web, 

and exhibits, to convey research results and the 

program’s messages. 

Transferring knowledge. Activities associated with 

transferring research and program information 

(both internally and externally) to critical 

audiences, from the national laboratories and 

program management. 

Measuring. Activities associated with measuring 

and assessing the relationships to critical 

audiences and the effectiveness of messages to 

them. 

The Communications and Outreach Project 

consists of the following tasks. 

Agreement Title FY 2006 

Budget ($K) 

NREL NCPV/PV Communications 570 

SNL NCPV/PV Communications 132 

DOE/GO and NETL Financial 

Assistance Outreach/ 

Communications 

300 

3. Results and Accomplishments 

We summarize our key results and 

accomplishments for FY 2006 under the four core 

activities mentioned under Technical Approach 

above. 

3.1 Planning 

•	 We served on the proposal review committee 

to choose the teams for Solar Decathlon 

Systems Integration and Coordination 160
 

 

 

 

 

 

 

 

 

 

2007. DOE announced the 20 teams chosen. 

We served on the Rules and Regulations 

Committee to revise the competition (about 

half of the 10 contests were changed 

significantly) and the Rules and Regulations 

for the competition. 

•	 The Solar Program Strategic Communications 

Team met as a full group—including 

personnel from DOE, NREL, and SNL—to 

discuss our role in the Solar America Initiative 

and how communications is vital to rolling out 

SAI’s aggressive technology acceptance and 

R&D efforts. (5/06) 

•	 We prepared the Solar Communications 

FY 2007 Draft R&D Project Proposal for the 

Technology Acceptance section of the Solar 

Energy Technologies Program. The write-up 

covers communications projects by NREL and 

SNL within both PV and CSP. (6/06) 

•	 The Solar Communications team participated 

in the SAI’s Technology Acceptance meeting 

in San Francisco, June 2006. The 

Communications representative documented 

the industry and research communities’ 

feedback regarding the development of the 

initiative, and the team will use the information 

in formulating business and communications 

strategies. (6/06) 

•	 We prepared the FY 2007 AOP. (9/06) 

3.2 Developing and Producing 

•	 We completed the DOE Solar Energy 

Technologies Program Annual Report, 

FY 2004, which included a CD of proceedings 

from the Solar Program 2004 Review 

Meeting. (10/05) 

•	 We implemented an online collection system 

for Solar Program Review Meeting papers, 

which streamlined the "by hand" collection 

system used in the past, and should save the 

Solar Program time and money. (10/05) 

•	 We provided dynamic content for the Solar 

Decathlon Web site, including daily photos 

and journals. (10/05) 

• For the 2005 Solar Energy Technologies 

Program Review Meeting (November 2005), 

we completed the meeting Program and 

Abstracts book and distributed 325 copies at 

the meeting. (11/05) 

•	 We completed a repurposing of the solarheating content on the EERE Solar Program 

Web site. Changes were necessary to provide 

more information about the subprogram's 

current research and partnerships and to 

make access to basic information about solarheating technologies more intuitive. (12/05) 

•	 We completed the final draft of the Solar 

Program Multi-Year Program Plan 2007–2011 

by the end of January. (1/06) 

•	 We completed and submitted the U.S. annual 

contribution to the IEA PVPS: Task 1 Annual 

Report: PV Technology Status in the USA. 

The U.S. submission is a summary of R&D, 

policy, U.S. industry, and DOE program 

accomplishments for FY 2005. (1/06) 

•	 We completed the migration of the EERE 

Solar Program Web site to DOE EERE’s new 

content management system 

www.eere.energy.gov/solar/. (2/06) 

•	 We created an exhibit for the groundbreaking 

of a new 65-MW solar parabolic trough plant 

in Nevada. The exhibit highlights the research 

accomplishments of an NREL/industry 

partnership with Solargenix. (2/06) 

•	 We completed the 3-D modeling and 

animation of the transfer pod/cluster tool 

concept, which is at the heart of the work to 

be conducted within the Process 

Development and Integration Laboratory of 

the Science and Technology Facility. (2/06) 

•	 We completed the DOE Solar Energy 

Technologies Program Annual Report, 

FY 2005, which includes a CD of proceedings 

from the Solar Program 2005 Review 

Meeting. The Annual Report chronicles all 

activities of the DOE Solar Program, giving 

account for how funding dollars are invested. 

(3/06) 

•	 We wrote and published DOE Solar Energy 

Technologies Program: Overview and 

Highlights (a June/July milestone). The 20-

page brochure provides engaging, accessible 

information about Solar Program activities and 

capabilities to a non-specialist audience, 

including Congress, industry partners, 

government agencies, and visitors to DOE 

facilities. (5/06) 

4th •	 We created a kiosk for the World 

Conference on Solar Energy Conversion, held 

in Hawaii in May. The focus was on luminaries 

in the PV field during the last several 

decades; the display included two flat-panel 

monitors that allowed participants to view and 

listen to unique interviews with many of the 

highlighted individuals discussing their 

careers and thoughts on the direction of solar 

research. (5/06) 

•	 We wrote, designed, and produced 

capabilities material for the NCPV's 

161 Systems Integration and Coordination
 

 

 

 

 

 

 

 

 

Measurements & Characterization (M&C) 

Division. The content is also being used in 

the redesign of the M&C Web site. (6/06) 

•	 We created new graphics for 19 display cases 

about PV technologies for the NREL Solar 

Energy Research Facility (SERF). The 

displays provide information on crystalline 

silicon, thin-film, and concentrating PV; 

manufacturing support; and balance of 

systems/systems integration. The cases are a 

major focus of tours to the SERF by various 

stakeholder groups and VIPs, such as 

legislators, agency heads, and industry 

executives. (6/06) 

3.3. Transferring Knowledge 

•	 Solar Decathlon 2005 hosted about 120,000 

visitors on the National Mall. We managed 

several key aspects of the event. Our village 

design and installation activity resulted in 

infrastructure for special events such as the 

Opening Ceremony, at which Secretary 

Bodman spoke; consumer workshops about 

energy efficiency and renewable energy, 

(about 1,400 attendees); and two exhibits: 

Energy Today provided information about 

EERE’s purpose and mission, and Anatomy of 

a House provided visitors with a primer on the 

basics of energy efficiency and solar energy 

for homes. Village design also included 

signage for the event. We managed the 

volunteer program—by far, the bulk of “event 

staff” interacting with the public is made up of 

volunteers from DOE and the Decathlon’s 

sponsors. We filled approximately 650 

volunteer “shifts.” We also managed the 

Communications Contest, which requires the 

student teams to develop Web sites and 

conduct tours of their houses on the mall. The 

“communications team” consisted of six from 

NREL, two from Oak Ridge National 

Laboratory, and one from SNL. We staffed the 

event and competition, conducting and 

managing the aforementioned activities while 

producing dynamic content for the Web site 

(scoring data, daily photos, and journals), 

which received 73,000 unique visits per day 

during the event. We also supported the 

media relations team, providing information 

and materials as needed. And we worked 

extensively with the student teams to ensure 

their interactions with visitors went as 

smoothly as possible. (10/05) 

•	 The Solar Communications Team represented 

the DOE Solar Program and NREL at Solar 

Power 2005 in Washington, DC. Attendees for 

this event included utility and energy service 

providers, the solar industry, and consumers. 

Our efforts focused on connecting external 

stakeholders with appropriate people at NREL 

and the EERE Solar Program. (10/05) 

•	 Under a grant from the DOE Golden Field 

Office, we supported the American Solar 

Energy Society (ASES) 2005 Tour of Solar 

Homes. The tour is the premier public 

demonstration event of deployed solar energy 

technology for the built environment, most 

frequently featuring energy efficiency, passive 

solar design, solar domestic hot water, 

photovoltaics, and daylighting. The tour 

reaches consumers interested in energy 

efficiency and renewable energy technologies, 

and, via media coverage, the general public 

who sees stories about the tour and the 

buildings in print and on the Internet, radio, 

and TV. 

•	 We produced material explaining the Science 

& Technology Facility, which was 

subsequently used by David Garman in 

presenting to the President’s Council of 

Advisors on Science and Technology 

(PCAST). (11/05) 

•	 We developed and produced several key 

posters to help NREL PV managers, as well 

as NREL Director Dan Arvizu, clearly explain 

the scope and value of the solar research 

being conducted at NREL. The posters were 

used in December, when NREL had separate 

visits from Clay Sell (DOE Deputy Director) 

and Ray Orbach (Director, Office of Science). 

(12/05) 

•	 On behalf of the Solar Program, we 

participated in the International Builders’ 

Show (IBS) in Orlando, FL (January 10–15). 

Exhibit participation at the show provides the 

Solar Program the opportunity to meet with 

builders, answer questions about all solar 

technologies, and distribute builder-oriented 

publications. With 100,000 attendees, IBS is 

the largest gathering of the buildings audience 

in the world. Participation in this event 

satisfies a strategic communications objective 

of disseminating information to the buildings 

audience. (1/06) 

•	 The NREL Solar Communications Team 

assisted DOE/EERE in publicizing the Solar 

America Initiative and the Notice of Program 

Interest (NOPI) for the initiative. 

Announcements regarding both events were 

developed and posted in strategic locations 

on the EERE Web site. (2/06) 

Systems Integration and Coordination 162
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

•	 The Solar Communications Team participated 

in the regular Task 1 meeting in Vancouver, 

BC, on behalf of the DOE Solar Program. The 

Photovoltaic Power Systems (PVPS) 

Programme is a collaborative R&D 

Agreement, established within the 

International Energy Agency, and conducts 

projects on the application of PV. IEA PVPS 

operates worldwide via a network of national 

teams in member countries, and promotes 

and facilitates the exchange and 

dissemination of information on the technical, 

economic, environmental, and social aspects 

of PV power systems. (3/06) 

3.4 Measuring 

•	 We prepared responses to questions asked 

by the Solar Program Review Meeting Review 

panel. We then participated in a question-andanswer period with three reviewers. Feedback 

helped to assess aspects of our work. (11/05) 

•	 We conducted a Web site survey and lessons 

learned on all communications and media 

outreach activities for Solar Decathlon 2005, 

which informed our development of the 2007 

identity, brochure, and Web site, as well as 

shaped our planning efforts for the next event. 

(12/05) 

•	 During the 2005 Decathlon, we managed 

photographers to ensure adequate 

documentation of the event. We also 

performed research and conducted interviews 

with teams. This preliminary work became 

part of Solar Decathlon 2005: the Event in 

Review, a technical report we produced about 

the event. The report overviews the 

competition, including final results, team 

strategies, and detailed descriptions of each 

of the 18 competition homes. A major goal of 

the Solar Decathlon is that each successive 

competition should advance the state of the 

art of solar-powered, energy-efficient 

homebuilding. This report was written with an 

eye toward guiding and educating the 2007 

Decathlon competitors. (6/06) 

4. Planned FY 2007 Activities 

Core Program Support: Develop and distribute 

Annual Report, Solar Program Overview, MYPP, 

and AOP. Maintain and improve some 12 Web 

sites and redesign the NREL PV, Measurements 

& Characterizations, and TroughNet Web sites. 

Edit/process the publication of ~400 technical 

papers. Produce a CSP overview publication. 

Support the CSP 1000 MW initiative through 

audience analysis and developing targeted 

information campaigns. 

Solar America Showcases/City Strategic 

Partnerships Documentation task: Participate in 

merit reviews, support task management (at DOE, 

GO, and NREL), and develop a communications 

plan. 

State Technical Outreach task: Participate in 

merit reviews, support task management (at DOE, 

GO, and NREL), and develop a communications 

plan. 

Utility Technical Outreach task: Participate in 

merit reviews, support task management (at DOE, 

GO, and NREL), and develop a communications 

plan. 

Solar Decathlon 2007: Preparations for the 

FY 2008 event must be completed by the end of 

FY 2007 and include developing an RFP for event 

management, and planning for special events, 

consumer workshops, volunteer program, and 

Communications Contest. Support the media 

outreach team, update Web content, prepare the 

Competition Program, write talking points for 

speakers, and serve on the Rules and 

Regulations Committee. 

National Solar Tour 2007: Conduct the 2007 

National Solar Tour with ASES under a grant from 

the DOE Golden Field Office. In coming years, 

add energy efficiency construction practices, 

information on appliances, and design support to 

an online energy calculator created to provide 

simple calculations for solar electric, solar 

thermal, and solar pool/spa heating. This tool will 

eventually provide a comprehensive vendor listing 

and localized insolation, utility rates, and incentive 

data to use in calculations, allowing consumers to 

determine for their property and locale the 

possibilities of renewable energy technologies and 

energy efficiency construction practices and 

potential vendors or contractors who could 

compete for their project. 

Interstate Renewable Energy Council (IREC): 

Maintain the Web-based Database for State 

Incentives for Renewable Energy (DSIRE), an 

ongoing project of the North Carolina Solar Center 

and IREC funded by DOE. 

Support projects such as Connecting to the 

Grid, Schools Going Solar database, Community 

Outreach, Training & Certification, Small Wind 

Energy News, Workshop-in-a-Box, Annual 

163 Systems Integration and Coordination
 

 

 

 

 

 

 

 

Renewable Energy Recognition Awards videos, 

public service announcements, guide, and 

newsletters. 

As the SAI Market Transformation activities, 

develop and conduct workshops, as appropriate, 

similar to the former Million Solar Roofs (MSR) 

Initiative Peer-to-Peer exchanges, which provided 

forums for MSR partners to learn from each other, 

receive training, and become informed on 

important issues. 

Focus on some current and often difficult issues 

impacting expanded renewable energy use; for 

example, rules that support renewable energy and 

distributed resources in a restructured market, 

connecting small-scale renewables to the utility 

grid, developing quality credentials that indicate a 

level of knowledge and skills competency for 

renewable energy professionals, and getting the 

right information to the right people. 

5. FY 2006 Special Recognitions, Awards, and 

Patents 

2006 International Association of Business 

Communicators (IABC)/Southern Region Silver 

Quill; Award of Merit; Print Communications: 

Special Publication, handbook, Brochures, OneTime Publications; for the DOE, Solar Energy 

Technologies Program: Overview and Highlights 

2005 Society of Technical Communicators (STC), 

FY 2006 Technical Communication Competition; 

Award of Excellence; Informational Materials 

Design; for the National Renewable Energy 

Laboratory 2005 Research Review (not solely a 

solar document, but it contained articles and 

information on solar technologies and was 

designed and written, in part, by members of the 

Solar Communications Team. 

6. Major FY 2006 Publications 

D. Gwinner et al., Solar Energy Technologies 

Program Multi-Year Plan 2007-2011. Final version 

not released, but draft posted at 

http://www1.eere.energy.gov/solar/about.html. 

S. Moon et al., DOE Solar Energy Technologies 

Program: FY 2004 Annual Report. (2005). 196 

pp.; NREL Report No. MK-520-36804; DOE/GO102005-2173. 

S. Moon et al., DOE Solar Energy Technologies 

Program FY 2005 Annual Report. (2006). 218 pp.; 

NREL Report No. BK-520-38743; DOE/GO102006-2246. 

S. Moon et al., (2006). Solar Decathlon 2005: The 

Event in Review. 62 pp.; NREL Report No. BK520-38264; DOE/GO-102006-2328. 

S. Pedigo et al., Solar America Initiative Web 

portal on Solar Energy Technologies Program 

Web site: http://www1.eere. energy.gov/solar/ 

solar_america. 

J. Zuboy et al., DOE Solar Energy Technologies 

Program: Overview and Highlights. (2006). 20 pp.; 

NREL Report No. BR-520-39081; DOE/GO102006-2314. 

J. Zuboy et al., DOE Solar Energy Technologies 

Program: FY 2005 Annual Report and 

Proceedings, Program Review Meeting (CDROM). (2006). ; NREL Report No. CD-520-38557; 

DOE/GO-102006-2245. 

7. University and Industry Partners 

The following organizations partnered in some of the project’s activities during FY 2006. 

Organization/ 

Principal Investigator Location/e-mail Description/Title of 

Research Activity 

FY 2005 

($K) 

Cost Share 

($K) 

Interstate Renewable 

Energy Council (IREC) 

Jane Weissman 

Latham, NY 

jane@irecusa.org 

Million Solar Roofs 

Outreach 300 0 

American Solar Energy 

Society 

Brad Collins 

Boulder, CO 

bcollins@ases.org 

2005–2009 National 

Solar Energy Tour 125* 247** 

*Funded with prior year (FY 2005) funds. **Spread over 5 years. No 2006 funds were obligated to this grant. 

Systems Integration and Coordination 164
 

 

 

 

 

 

____________________________________________________________________________________ 

 

 

 

 

 

 

____________________________________________________________________________________ 

 

International Activities 

Performing Organizations: National Renewable Energy Laboratory (NREL) 

Sandia National Laboratories (SNL) 

Key Technical Contacts: Cecile Warner (NREL), 303-384-6516, cecile_warner@nrel.gov 

 Vipin Gupta (SNL), 915-491-1158, vpgupta@sandia.gov 

DOE HQ Technology Manager: Tom Kimbis, 202-586-7055, tom.kimbis@ee.doe.gov 

FY 2006 Budgets: $150K (NREL), $130K (SNL) 

Objectives 

•	 Understand the drivers associated with international growth in PV sales. 

•	 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 

• Published the Solar International Activities: Strategic Plan developed by our team and adopted 

relevant elements of plan into the newly formed Solar America Initiative (SAI) Market 

Transformation 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." 

•	 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. 

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 Sandia). 

1. Introduction interested U.S. constituents, and determining how 

to improve U.S. PV product performance at a 

The primary mission of the Solar Program lower cost. Through our IEA involvement, as well 

International Activities task was to continually as our strategic planning exercise, our team 

learn from the international adoption of solar members also tried to provide timely data on 

technologies and improve U.S. solar technologies emerging markets, nurture relationships with key 

sold domestically and abroad. Because Germany, manufacturers and integrators abroad, and 

Japan, and Europe continue to drive the growth of distribute this information, where appropriate, to 

the solar market, our task included: keeping U.S. industry. 

current on why this is happening, understanding 

policy impacts, sharing this information with 

165 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 to the Systems-Driven Approach (SDA) 

process 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 2006 

Budget ($K) 

PV International (NREL) 150 

PV International (SNL) 130 

3. Results and Accomplishments 

One month after our international strategic plan 

was completed, President Bush announced in his 

2006 State of the Union address his advanced 

energy initiatives, including solar technologies. 

This became DOE’s new Solar America Initiative 

(SAI). Within a couple of months, our multiinstitutional team worked hand-in-hand with new 

staff at the DOE Solar Program to define and 

detail the planned SAI Technology Acceptance 

activities—activities to reduce market barriers and 

transform the market (focused on the U.S. market) 

for wider use of solar energy technologies. 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. 

4. Ongoing and Planned FY 2007 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: 

•	 Review and selection of winning Federal 

Opportunity Announcement proposals for 

Solar America Showcases, City Strategic 

Partnerships, Code and Standards, and State 

and Utility. 

•	 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." 

5. Major FY 2006 Publications 

Robert Foster, Paul Gilman, Vipin Gupta, Don 

Gwinner, Robert Hassett, Christy Herig, Al Hicks, 

Marguerite Kelly, Jean Ku, Debra Lew, Jeff 

Nelson, Wendy Parker, Susannah Pedigo, David 

Renne, John Thornton, and Harin Ullal, Solar 

International Activities: Strategic Plan, Solar 

Energy Technologies Program, U.S. Department 

of Energy, January 2006, pp. 1–26. 

Systems Integration and Coordination 166
 

6. University and Industry Partners 

The following organizations partnered in the project’s research activities during FY 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research 

Activity 

FY 2006 

($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 

167 Systems Integration and Coordination
 

 

 

 

_____________________________________________________________________________________ 

Process Integration, Capital Equipment, and Facilities 

Performing Organizations: National Renewable Energy Laboratory (NREL)

 Sandia National Laboratories (SNL) 

Key Technical Contacts:	 Larry Kazmerski (NREL-NCPV, Primary Contact), 303-384-6600, 

larry_kazmerski@nrel.gov 

Brent Nelson (NREL-S&TF), 303-384-6407, brent_nelson@nrel.gov

 Tom Mancini (SNL, Primary Contact), 505-844-8643, trmanci@sandia.gov 

DOE HQ Team Leaders:	 Thomas Rueckert, 202-586-0942, thomas.rueckert@ee.doe.gov 

Robert Hassett, 202-586-8163, robert.hassett@ee.doe.gov 

FY 2006 Budgets:	 $1,872K (NREL, S&TF Essential Capital Equipment) $580K (NREL, 

Process Integration), $425K (SNL) 

Objectives 

Related to the Process Integration Project at the Science and Technology Facility (S&TF) at NREL: 

•	 Develop infrastructure that will allow researchers to gain new knowledge that is difficult—if not 

impossible—to obtain with existing equipment. 

•	 Implement the process-integration design standards for hardware and software in the 

development and integration of research tools. These tools include deposition, characterization, 

and processing technologies in support of the core research technologies and their collaborations 

with university and industrial partners. 

Related to the National Solar Thermal Test Facility (NSTTF) at SNL: 

•	 Operate and maintain facilities at the NSTTF. 

•	 Support the DOE Concentrating Solar Power (CSP) Subprogram test and work-for-others
 

activities at the NSTTF. 

Accomplishments 

S&TF: 

•	 Project management support for the construction of a cluster tool to support silicon research. 

•	 Project management and engineering development leading to the delivery, acceptance, and 

operation of a stand-alone tool for transparent conducting oxides. 

•	 Project management and engineering development leading to the delivery, acceptance, and 

operation of an inter-tool transport pod to move samples between tools in a controlled ambient 

(high vacuum). Successful transfer of samples between the stand-alone tool for transparent 

conducting oxides and the transport pod. 

•	 Project management support leading to the competitive bid of a molecular beam epitaxy (MBE)-

type deposition chamber for copper indium (gallium) diselenide (CIGS) materials. 

•	 Project management support leading to the competitive bid and contract awarding of an Auger 

electron spectrometer that is compatible with other tools as a mobile diagnostic tool. 

•	 Project management and engineering development in the design of an automated chemical bath 

deposition system for cadmium sulfide growth. 

•	 Project management support leading to the delivery and acceptance of a spectroscopic
 

ellipsometer. 

•	 Project management support leading to the delivery and acceptance of thickness monitoring 

equipment consisting of a profilometer and an interferometer. 

•	 Project management support leading to the procurement of a UV-visible spectrophotometer. 

•	 Earned Value Management System project management of the S&TF Essential Capital 

Equipment. 

Systems Integration and Coordination 168
_____________________________________________________________________________________ 

 

 

 

 

NSTTF: 

•	 Support of the operation of the Dish Stirling Model Power Plant. 

•	 Completed preliminary testing of a theoretical overlay photographic (TOP) trough alignment 

approach on the trough rotating platform. 

•	 Started modification of the Engine Test Facility to accommodate 24-hour, gas-fired operation of 

Stirling engines. 

•	 Held a NASA contractors meeting on aerocapture and provided a site demonstration of high-flux 

test support for the program. 

•	 Performed minimal level of maintenance and required environmental health and safety (EH&S) 

activities at the NSTTF. 

Future Directions 

S&TF: 

•	 Finalize the unfinished procurements in the previous section. 

•	 Design and construct a general use current-voltage (JV)/quantum efficiency (QE) system. 

•	 Design and construct an X-ray photoelectron spectrometer (XPS) and ultraviolet photoelectron 

spectrometer (UPS). 

•	 Design and construct a cluster tool capable of Fourier transform infrared (FTIR) and visible optical 

analysis, ellipsometry, lifetime measurement, and thermal processing. 

NSTTF: 

•	 Due to the age of equipment and minimal maintenance over the last five years, we need to start 

planning a major maintenance upgrade to NSTTF equipment. 

•	 Maintain NSTTF activities in support of ES&H requirements and site training. 

1. Introduction 

The purpose of the Process Integration Project of 

the National Center for Photovoltaics (NCPV) is to 

develop an infrastructure at the Science and 

Technology Facility (S&TF) at NREL 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 our existing tool set, which lacks sufficient 

in-situ or real-time measurement capabilities, or 

lacks access to analytical tools where the sample 

remains in a controlled environment between 

deposition and processing or measurement. This 

new infrastructure will provide flexible and robust 

integration of deposition, processing (e.g., etching, 

annealing), and characterization tools via a 

standardized transfer interface such that samples 

move between tools in a controlled ambient. 

Ultimately, this synergistic effort between NREL 

staff, universities, and the PV industry—around an 

integrated tool base—will add to the PV 

knowledge base and help move many PV 

technologies forward. 

We will achieve this purpose by building a 

collection of integrated deposition, 

characterization, and processing tools. These 

integration standards must be flexible to allow for 

changing research needs, yet be robust and 

reliable. Deposition tools must be able to deposit 

uniformly and reproducibly over areas that are 

large enough to be meaningful to industry and be 

able to handle a wide variety of sample substrates. 

The benefits of having integrated tools include 

allowing researchers to: 

•	 Answer previously inaccessible research 

questions. 

•	 Control and characterize critical surfaces and 

assess the impact of these interfaces on 

subsequent layers. 

•	 Assess process-related source chemistry, 

surface chemistry and kinetics, and bulk 

reconstruction. 

•	 Grow layers and alter interfaces using 

controlled transfer ambients (without exposure 

to air). 

•	 Develop new techniques, methodologies, 

device structures, materials, and tools. 

Activities at the National Solar Thermal Test 

Facility (NSTTF) at SNL focus on supporting the 

six-dish mini power plant of Stirling Energy 

Systems (SES) and the operation and 

maintenance (O&M) of the facility in the context of 

complying with all maintenance and ES&H 

requirements. No new facilities or equipment are 

being developed. 

169 Systems Integration and Coordination
 

 

 

 

 

 

 

 

 

 

 

 

 

 

2. Technical Approach 

2.1 S&TF 

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). When neither of these integration methods 

is possible, techniques will be integrated by 

transferring samples from one location to another 

either via intra-tool or inter-tool sample transport. 

Intra-tool transport is the movement of samples 

between techniques within the same set of 

interconnected chambers, that is, a cluster tool. 

The actual transfer mechanism could be robotic or 

a linear track transport mechanism. Initial cluster 

tools will use robotic transfers. Inter-tool transport 

is the movement of samples between techniques 

where those techniques do not share direct 

connection. These techniques could be in a 

stand-alone tool or a part of a cluster tool. The 

sample is moved from one tool into the pod, which 

is sealed and disconnected from that tool before 

being wheeled to another tool, where the process 

is reversed. The transfer ambient within the pod 

can be either an atmosphere of ultrahigh-purity 

inert gas or high vacuum. This 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 (FOUP) 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. The transport pods being 

implemented under this project have two 

significant advantages over the SMIFs and FOUPs 

in the microelectronics industry. First, they protect 

samples and interfaces from contamination at the 

molecular level (not just from particulates). 

Second, these pods allowed us to save money on 

the building construction (no clean rooms). 

The main design goals of the NCPV Process 

Integration Project are to: 

•	 Develop a standard sample transport between 

tools. 

•	 Ensure the sample transport mechanism is 

robust. 

• Control the ambient of that sample transfer. 

•	 Be able to deposit uniformly and reproducibly 

over areas large enough to be meaningful to 

industry. 

• Handle a wide variety of sample substrates. 

• Standardize control and data logging software. 

• Integrate as many techniques as practical. 

Because of our need to handle a variety of 

substrate sizes, shapes, and materials in a sample 

platen, there are no "off-the-shelf" solutions to 

integrating our tools. Therefore, we had to 

develop our own set of design standards for future 

tool development, especially for the pod. The 

progress on each of the various tools in this 

project is discussed in the next section. Each 

custom tool involves the following development 

steps: 

•	 Conceptual design specifications 

• Obtain budgetary quotes 

•	 Scope adjustment (to fit budget) 

• Final specifications 

•	 Award contract and vendor fabrication 

•	 Site preparation (for tool hookup at NREL) 

•	 Acceptance and full operation at NREL. 

2.2 NSTTF 

The technical approach to operating and 

maintaining the NSTTF is to support the six-dish 

mini power plant and to assure that all ES&H 

requirements are met. 

3. Results and Accomplishments 

3.1. S&TF 

There is a three-year budget for essential capital 

equipment associated with the construction and 

operation of the S&TF. This essential capital 

equipment includes the following projects, which 

are divided by status according to the 

development steps listed above. 

Projects with equipment that is delivered, 

accepted, and fully operational at NREL: 

•	 TCO sputtering stand-alone tool (AJA 

International) 

•	 Transport pod (Transfer Engineering) 

• Profilometer (Veeco/Dektak) 

• Interferometer (Veeco/Wyko) 

• Ellipsometer (Woolam). 

Projects with contracts awarded and equipment 

being fabricated: 

•	 UV/visible spectrophotometer (Varian) 

•	 Silicon CVD cluster tool (MVSystems) 

• Auger electron spectrometer mobile tool (DCA). 

Systems Integration and Coordination 170
 

 

 

 

 

 

 

 

 

 

Projects with final specifications and that are in the 

procurement process: 

•	 MBE-type chamber to deposit CIGS 

•	 CBD CdS-controlled ambient stand-alone tool. 

Projects undergoing budgetary rescoping: 

•	 CIGS cluster-tool robotic hub 

•	 JV/QE multi-user work station. 

Projects developing final specifications: 

•	 X-ray and ultraviolet photoelectron 

spectrometer stand-alone tool 

•	 Electro-optical/processing cluster tool. 

Software Integration. Software is critical to having 

fully integrated tools, not only for automation, but 

for easy access to the data from which information 

can be gleaned and knowledge built. The 

approach we are pursuing is illustrated in Fig. 1. 

This is an effort to go beyond the tools built to the 

process-integration hardware standards to 

integrating data management of other equipment 

and collaborations. Currently, we are working with 

the Scientific Computing Center (SCC) at NREL to 

test Web-based data storage and recovery 

systems. We are also working with the 

Manufacturing Research Center at the Georgia 

Institute of Technology (MARC/GT) to test their 

data-brokering scheme (CAMX). Ultimately, 

having integrated data will allow us to work with 

the SCC using sophisticated data-mining and 

visualization tools. Also, we will have the ability to 

pull a recipe out of a database and load it to a tool 

for implementation, and then have the tool data-log 

back to the database (aka, recipe in/ results out). 

Fig. 1. Schema for software integration 

3.2 Operation and Maintenance of the NSTTF 

Accomplishments include that we: 

•	 Continued operating the SES six-dish mini 

power plant. 

•	 Supported NASA testing of high-flux materials. 

•	 Operated the rotating trough platform in 

support of TOP alignment testing. 

•	 Started modification of the Engine Test Facility 

to accommodate long-term Stirling engine 

testing. 

•	 Complied with all ES&H and training 

requirements. 

4. Planned FY 2007 Activities 

4.1 S&TF 

Projects with equipment to be delivered to NREL 

in FY 2007: 

•	 UV/visible spectrophotometer (Varian) 

•	 Silicon CVD cluster tool (MVSystems) 

• Auger electron spectrometer mobile tool (DCA) 

•	 MBE-type chamber to deposit CIGS 

•	 CBD CdS-controlled ambient stand-alone tool 

•	 CIGS cluster-tool robotic hub 

•	 JV/QE multi-user work station. 

Projects to place under contract in FY 2007: 

•	 X-ray and ultraviolet photoelectron 

spectrometer stand-alone tool 

•	 Electro-optical/processing cluster tool 

•	 Develop and construct a substrate cleaning, 

platen assembly, pod loading station. It will 

include the ability to measure particulates on a 

substrate surface will be incorporated on this 

station or the pod diagnostic chamber. 

•	 Develop pod and chamber diagnostic 

capabilities. This includes a pod diagnostic 

chamber (e.g., vacuum, interface controls) and 

making functional and available a mobile 

residual gas analyzer cart. 

•	 Improve the pod design and procure multiple 

pods in “bulk" order. This includes getting 

new, more robust, tooling for pod alignment to 

the dock. 

Software Integration. Software integration is an 

exceedingly time-consuming process requiring 

dedicated personnel. The microelectronics 

industry has determined that if software integration 

is developed along with the hardware 

development, it is about 40% of the development 

cost. When software integration is developed after 

the hardware is developed, it can account for more 

than 400% of the hardware development costs. 

For this part of the effort to be successful we need 

171 Systems Integration and Coordination
 

 

 

 

to hire two software engineers: one to help with 

tool integration into the overall architecture (within 

the green, or top dashed, line in Fig. 1) and the 

other to implement the over all architecture and 

continuously improve the user interface. These 

software hires and efforts will be a major effort in 

FY 2007. 

4.2 NSTTF 

At SNL, O&M of the NSTTF will continue in an 

EH&S-compliant manner. We will also start 

planning for a major maintenance upgrade to 

reestablish the operational capability of the 

NSTTF. 

5. University and Industry Partners 

This project ensures consistency of hardware and 

software between equipment within the core 

research groups of the NCPV and also helps them 

build state-of-the-art infrastructure. This 

equipment is owned and operated by those 

groups. Therefore, these core research groups 

design the projects utilizing this equipment, 

including specific collaborations with the university 

and industrial partners. This project facilitates 

those partnerships. 

Systems Integration and Coordination 172
 

 

 

 

 

EERE Crosscutting Activities 

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. 

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. 

The DOE Solar Program funded nine Congressionally Directed Projects through financial 

assistance awards in FY 2006. The scope of the projects varies significantly from research into 

carbon-nanotube transparent conductive coatings for thin-film photovoltaic cells, to development 

of electron microscopes for science students in college, to research in quantum dot light-emitting 

diodes. 

Some accomplishments in this arena for FY 2006 are listed below. 

Small Business Innovation Research 

•	 Developed “Smart Skin,” a sturdy coating for solar-thermal mirror concentrators. 

•	 Achieved single-step wafer fabrication from metallurgical-grade silicon. 

•	 Developed a hydrogen electrolyzer powered by PV concentrators. 

Congressionally Directed Projects 

•	 Developed and evaluated a new PV device structure in which carbon nanotubes replaced the 

indium tin oxide and CuxTe back contact layer of the top cell in a CdTe tandem thin-film cell. 

NREL reported a maximum efficiency of 12.9%. 

•	 Produced carbon nanotube-based, highly conductive polymer coatings (to be used as 

screens for PV panels) with an optical transparency greater than 80%. 

•	 Turned a "brownfield" site into a "brightfield" site by installing a 425-kW PV system. 

•	 Completed development of six prototype tabletop scanning electron microscopes to be used 

in postsecondary schools. 

173 EERE Crosscutting Activities
EERE Crosscutting Activities 174
 

 

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Small Business Innovation Research 

Performing Organization:	 DOE HQ Solar Energy Technologies Program 

Administrative: DOE HQ Germantown 

Support (Proposal Evaluation):	 National Renewable Energy Laboratory
 

Sandia National Laboratories
 

Key Technical Contact and 

DOE HQ Technology Manager:	 Alec Bulawka, 202-586-5633, alec.bulawka@ee.doe.gov 

FY 2006 Budget:	 $1,800K 

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 

Awards that advanced/matured in FY 2005/2006: 

•	 “Smart Skin,” development of sturdier coating for solar-thermal mirror concentrators 

•	 Single-step wafer fabrication from metallurgical-grade silicon 

•	 Effective removal of impurities in silicon under vacuum 

•	 Development of highly versatile and portable, stackable, more compact inverter 

•	 Development of a hydrogen electrolyzer powered by PV concentrators 

•	 Refinement of a process to convert waste thermal energy into electricity by luminescence upconversion. 

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 

The Solar Program has also benefited to a large 

Each year, ten federal departments and agencies extent from the Office of Basic Energy Sciences 

(including DOE) are required by the Small Business contribution in nanotechnology topics for PV in 2006. 

Innovation Research (SBIR) Program to reserve a The 2007 Solar Program is nested mainly in the 

portion of their R&D funds for award to small, U.S.- Renewable Energy Sources SBIR category (Topic 2). 

owned businesses. Over the life of the SBIR SBIR activities fit very nicely into the DOE Solar 

Program, the Solar Program has contributed $16 Program Multi-Year Technical Plan, because they 

million and received $34 million in research funding. continue to augment and support the core program, in 

175 EERE Crosscutting Activities
 

 

 

 

 

 

 

 

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 FYs 2006 and 

2007 were required to clearly demonstrate the 

applicants’ ability to proceed to hardware 

development, fabrication, testing and manufacture of 

technologies. 

2.1 FY 2006 Phase 2 Awards
 

There were no new Phase 2 awards initiated in 2006. 

2.2 FY 2006 Phase 1 Awards (September 2006)
 

Nanosolar, Inc.: Printed Solar Cell Using 

Nanostructured Ink
 

TDA Research: Improved Fullerenes for Organic
 

Photovoltaics
 

MicroCell Technologies: Ultrahigh Moisture Barrier
 

Coatings for Photovoltaic Systems
 

Midwest Optoelectronics: Novel Interconnection 

Process for Lightweight Flexible PV Modules
 

Wakonda Technologies, Inc.: Alternative Thin Film
 

Semiconductor Materials
 

NanoSonic, Inc.: High Performance, Low Cost
 

Nanostructured Mirror Surfaces
 

See the SBIR Web site (http://sbir.er.doe.gov/sbir) for 

details on FYs 1998–2006 awards. 

3. Results and Accomplishments 

Several SBIR awards advanced their goals and 

produced very encouraging results of their R&D to 

date. Significant progress was made in the 

development of low-cost, high-performance 

nanostructured mirror surfaces and indestructible 

“smart skin” for solar dish-concentrating systems by 

Nanosonic. GT Equipment Technologies has 

developed a single-step wafer-fabrication process in 

which metallurgical-grade silicon is purified and solar 

silicon wafers are then drawn directly, bypassing 

several intermediate steps. This approach is much 

more cost effective than other options, with a 25:1 

reduction in raw material cost. Crystal Systems, Inc., 

in an alternative approach, has developed a crucible 

and a process that, under vacuum, will be used for 

effective removal of impurities in metallurgical-grade 

silicon in the production of solar-grade Si. UQM 

Technologies was successful in the design and 

production of a very high power density, reliable, 

stackable (5 kW and up) inverter for anticipated use 

by multiple alternative energy source customers. It 

will operate more efficiently, deliver more power 

capability, and be more cost effective than what is 

presently available on the market. A 25-kW High 

Concentration Photovoltaic System prototype, in 

conjunction with a hydrogen electrolyzer incorporating 

a DC-DC converter and a low-pressure storage tank 

to produce clean hydrogen, is emerging for testing 

from Amonix, Inc. Hence, this is an alternative 

renewable energy source to produce clean hydrogen. 

MetroLaser is furthering its development of the 

process of luminescence upconversion to convert the 

infrared (excess waste heat) directly into electricity. 

Application will maximize absorption across the solar 

spectrum in a cell, while minimizing fundamental heat 

losses. 

4. Planned FY 2007 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 

EERE Crosscutting Activities 176
 

 

 

 

 

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 windloading 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 2005 and 2006 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 2006 (no cost share). 

Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2005 

($K) 

GT Equipment 

Kedar Gupta 

Merrimack, NH 

gupta@gtequipment.com 

An Innovative Technique of 

Preparing Solar-Grade Silicon 

Wafers from Metallurgical-Grade 

Silicon by In-Situ Purification 

600 

Crystal Systems 

Fred Schmid 

Salem, MA 

fschmid@crystalsystems.com 

Development of Solar-Grade 

Silicon 600 

UQM Technologies 

Jon Lutz 

Frederick, CO 

jlutz@uqm.com 

Power Converters for Diverse 

Applications 600 

Amonix, Inc. 

Vahan Gharboushian 

Torrance, CA 

drvahan@earthlink.net 

A High Efficiency PV-to-Hydrogen 

Energy System 600 

GT Equipment 

Kedar Gupta 

Merrimack, NH 

gupta@gtequipment.com 

Novel Low-Cost Process for 

Production of Crystalline Wafers 

for the Photovoltaic Industry 

100 

MetroLaser, Inc. 

Bauke Heeg 

Irvine, CA 

bheeg@metrolaserinc.com 

Thermal (Solar) Photovoltaics 

Using Luminescence of 

Upconverters 

100 

Distributed Power, Inc. 

Richard West 

San Luis Obispo, CA 

Rick.west@distributedpower.us 

Improved Performance, SystemIntegrated Power Converter with 

Advanced Circuit Topology for 

Renewable Energy Applications 

100 

NanoSolar, Inc. 

Chris Eberspacher 

Palo Alto, CA 

Chris@nanosolar.com 

Printed Solar Cell Using 

Nanostructured Ink 500 

TDA Research 

 Michael D. Diener 

Wheat Ridge, CO 

Mikee@tda.com 

Improved Fullerenes for Organic 

PV 100 

Microcell Technologies 

Richard M. Formato 

Littleton, MA 

Rformato@microcell-tech.com 

Ultrahigh Moisture Barrier 

Coatings for Photovoltaic 

Systems 

100 

177 EERE Crosscutting Activities
Organization/ 

Principal Investigator Location/e-mail Description/Title of Research Activity 

FY 2005 

($K) 

Midwest Optoelectronics 

Aarohi S. Vijh 

Toledo, OH 

Vijh@mwoe.com 

Novel Interconnection Process for 

Lightweight Flexible PV Modules 100 

Wakonda Technologies, 

Inc. 

Leslie G. Fitzemeier 

Fairport, NY 

lfitzemeier@earthlink.net 

Alternative Thin Film 

Semiconductor Materials 100 

NanoSonic, Inc. 

Michelle Berg 

Blacksburg, VA 

mberg@nanosonic.com 

High-Performance, Low-Cost 

Nanostructured Mirror Surfaces 100 

EERE Crosscutting Activities 178
 

 

 

 

 

 

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____________________________________________________________________________________ 

Conductive Coatings for Solar Cells Using Carbon Nanotubes 

Performing Organizations: Eikos, Inc., Franklin, Massachusetts

 National Renewable Energy Laboratory (NREL) 

Key Technical Contacts:	 Paul Glatkowski, Eikos, 508-528-0300, pglatkowski@eikos.com 

Tim Coutts, NREL, 303-384-6561, tim_coutts@nrel.gov 

Glenn Doyle, DOE-GO, 303-275-4706, glenn.doyle@go.doe.gov 

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

FY 2006 Budgets:	 $1,410K (DOE), $371K (Eikos cost share), $75K (NREL) 

Objectives 

•	 Develop requirements list for each solar cell type, wherein the transparent conductive coating 

(TCC) specifications are listed and the advantages and disadvantages of applying the carbon 

nanotube (CNT) technology are assessed and compared to existing TCCs. 

•	 Improve optoelectronic performance to achieve greater than 90% transmission at 

100 ohms/square through improved purification, dispersion, and morphology and helicity control. 

•	 Determine the best application method(s) in terms of compatibility with the solar industry. 

•	 Define photovoltaic design and determine commercial obstacles for implementation in 

commercial markets. 

Accomplishments 

•	 Successful use of CNTs in solar applications focused on further improvement of electrical
 

conductivity and optical transmittance of CNT coatings. 

•	 Continued research to develop better understanding of underlying mechanisms responsible for 

CNT sensitivity to surface resistance instability, known as Rs-drift. 

•	 Explored ways, such as barrier materials, to minimize or eliminate changes in electrical 

resistance (R) and optical transparency (T), or R/T, during use. 

•	 Explored avenues of performance enhancement by focusing on: CNT purification and metallic 

tube separation techniques, chemical doping, CNT patterning and alignment, advances in 

commercial and research materials, and field-effect schemes. 

•	 Continued to develop improved efficiency coating materials and transfer methods suitable for 

batch and continuous roll-to-roll fabrication requirements. 

•	 Developed and evaluated a new PV device structure in which CNTs replaced the indium tin oxide 

(ITO) and CuxTe back contact layer of the top cell in a CdTe tandem thin-film cell. NREL reported 

a maximum efficiency of 12.9%. 

Future Directions 

•	 Future directions target the following areas of research and development: Further CNT ink 

purification through “High G” centrifuging; examining metallic CNT harvesting methods; studies 

on conductive coating scale-up activities; studies on connectivity between CNT and external 

circuitry; further characterization on CNTs as PV material; publication of scientific results on CNTenabled solar cells; and exploration of commercial interests and use of CNTs in PV systems. 

•	 The results of research into CNT in PV cells has the potential to benefit researchers make 

progress toward the goal of making tandem CdTe top cells 25% efficient, which brings the 

technology closer to the performance of ITO cells. 

1. Introduction based on carbon nanotubes (CNTs) can perform 

at an electrical resistivity and optical transparency 

The project consists of conducting research to in the range required for use in solar cells. Today’s 

prove that transparent conductive coatings (TCCs) solar cells are fabricated using metal-oxide-based 

179 EERE Crosscutting Activities
 

 

 

 

 

 

 

 

 

 

 

 

 

TCCs with optoelectronic performance significantly 

exceeding that currently possible with CNT-based 

TCCs. The motivation for replacing metal-oxidebased TCCs is their inherent brittleness, 

expensive deposition cost, and relatively high 

deposition temperatures, which leads to reduced 

optoelectronic performance on plastic. 

Alternatively, CNT-based TCCs overcome all 

these shortcomings while offering the ability to be 

applied in existing, very low cost, plastic filmprocessing equipment, such as continuous roll-toroll coating. 

At today’s level of development, CNT-based TCCs 

are nearing commercial use in touch screens, 

some types of information displays (e.g., computer 

LCD monitors), and some military applications. 

However, the requirements for use in solar 

devices is nearly ten times higher than for those 

applications. Significant exploratory research is 

required on the fundamental CNT composition, 

dispersion, and deposition (film-forming). 

Theoretical calculations indicate that the current 

CNT TCC is capable of meeting the optoelectronic 

performance needed for solar cells. However, the 

path to reaching optoelectronic performance near 

theoretical limits will require successful application 

of carbon nanotechnology, which uses highly 

specialized tools and processes discovered in the 

past 2 years. 

Specifically, Eikos will explore several potential 

experimental pathways expected to advance this 

TCC material system to the next generation of 

performance. Eikos will use specialized analytical 

services and proprietary nanotube purification 

processes to isolate and characterize specific 

types of nanotubes. Eikos will further purify, 

disperse, formulate, coat on films, and test the 

resulting TCC. Eikos will build working solar 

devices using the coatings, measure performance, 

and most importantly provide consultation on the 

direction, specification, and utility of the resulting 

TCC materials. Eikos has set a goal of a 3x 

improvement in optoelectronic performance and of 

developing an understanding of the remaining 

potential for further improvement. Sample films 

will be fabricated and used in laboratory-scale 

solar devices to serve as the proof of concept. 

2. Technical Approach 

(1) Develop requirements list for each solar cell 

type wherein the TCC specifications are listed 

and the advantages and disadvantages of 

applying the technology are assessed and 

compared to existing TCCs. 

(2) Improve optoelectronic performance to 

achieve greater than 90% transmission at 

100 ohms/square through improved purification, 

dispersion, and morphology and helicity 

control. 

(3) Determine the best application method(s) in 

terms of compatibility with the solar industry. 

(4) Define photovoltaic design and determine 

commercial obstacles for implementation in 

commercial markets. 

2.1 FY 2006 Tasks 

Task 1: CNT Performance Enhancement. Key 

areas researched under this task include: 

development of high-purity CNT materials; 

formulation of high-concentration CNT inks; 

identification of target morphology methods; 

identification of metallic CNT harvesting methods; 

identification and formulation of chemical doping; 

and investigation of the properties of commercial 

CNT materials. 

Task 2: CNT Environmental Performance. Key 

areas of research under this task include: 

research into environmental barriers and 

accelerated weather testing. 

Task 3: 3rd-Generation PV Cells. Key areas of 

research under this task include: CNT 

characterization and investigation and fabrication 

of CdTe tandem and organic PV cells. Eikos and 

NREL developed a new PV device structure, 

which is a CdTe polycrystalline high-efficiency top 

cell for thin-film tandem cells. At a sheet 

resistance of 100 ohms/square, CNT conductive 

coating back contacts produced efficiencies of 

12.2%; at 50 ohms/square, the efficiency was 

12.4%. Also, Eikos and NREL fabricated organic 

PV (OPV) cells with CNTs and a binder and an 

inverted OPV cell. Eikos and NREL also 

performed electrodeposition of ethylene 

dioxythiophene (EDOT) onto bare CNT films. No 

additional CIGS cells will be fabricated by NREL 

using CNT until Eikos can successfully 

demonstrate n-type doping of the CNT layer. 

Task 4: CNT Conductive Coatings in PV 

Manufacturing. Key areas of research under this 

task include: investigating conductive coating 

uniformity; examining patterning methods; 

identifying interconnection methods; and 

identifying process scale-up options. 

EERE Crosscutting Activities 180
 

 

 

3. Results and Accomplishments 

Progress continues on research aimed at CNT 

performance enhancement, CNT environmental 

performance, 3rd-generation PV cells, and CNT 

processes/methods in PV manufacturing. 

4. Planned FY 2007 Activities 

Plans for continued funding of Congressionally 

Directed Projects are the prerogative of Congress. 

Although this single-year funded project may 

extend beyond a single-year performance period, 

continued funding by the Solar Program is not 

planned. 

5. Major FY 2006 Publications 

T.M. Barnes, “Hole conducting CNT Transparent 

Contacts for Photovoltaics,” MRS Fall 2006 

Conference, Boston, November 27–December 1, 

2006. 

J. van de Lagemaat, “Organic, Excitonic Solar 

Cells with CNT Replacing ITO as Transparent 

Electrodes,” MRS Fall 2006 Conference, Boston, 

November 27–December 1, 2006. 

C. Weeks, Single Walled Carbon Nanotube 

Coatings as Transparent Conductors,” MRS Fall 

2006 Conference, Boston, November 27– 

December 1, 2006. 

181 EERE Crosscutting Activities
 

 

 

 

 

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Dynamic Shading System with Integrated Concentrator Solar Module 

Performing Organization: Rensselaer Polytechnic Institute (RPI), Troy, New York 

Key Technical Contacts: Anna Dyson, RPI, (646) 872-8589, dysona@rpi.edu 

Glenn Doyle, DOE-GO, 303-275-4706, glenn.doyle@go.doe.gov 

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

FY 2006 Budgets: $742K (DOE), $256K (RPI cost share) 

Objectives 

•	 Design, construct, and install a curtain wall unit incorporating a full-scale array of an integrated 

concentrating photovoltaic system. 

Accomplishments 

•	 Determined that a planar lens shape for the two-axis tracking concentrator PV cell would meet 

the requirements of allowing close packing at all normal incidence. 

•	 Made progress in optimizing cell tracking while reducing thermal loading to the high-efficiency 

multijunction cells. 

1. Introduction 

This Congressionally Directed Project is for the 

design, build, and extensive test of a full-scale 

installation of a building-integrated PV system. 

This system will produce electricity, capture 

thermal energy, provide improved indoor lighting 

through shading, and lower building energy loads. 

2. Technical Approach 

Evaluate quarter-panel scale mock-up of Dynamic 

Solar Window Shading (DSWS) as a test bed for 

system operations (4th generation); develop 5thgeneration DSWS for large-scale use; refine 

optical modules, actuating tracking and heat 

transfer systems; design systems integration; 

fabricate 5th-generation system; test and evaluate 

integrated solar module at NREL; test 5thgeneration system and evaluate performance. 

3. Results and Accomplishments 

Through research and testing, a planar lens shape 

for the two-axis tracking concentrator PV cell was 

determined to meet the requirements of allowing 

close packing at all normal incidence. This lens 

allows maximum conversion of solar irradiance to 

electrical power while permitting substantial 

daylighting. Progress continues in optimizing cell 

tracking while reducing thermal loading to the 

high-efficiency multijunction cells. Research 

continues on capturing the solar power not 

converted to electricity via a coolant flow through 

the receiver on which the cell is mounted. This 

coolant is used for hot water heating and 

potentially for refrigeration cycles. 

4. Future Planned Activities 

Plans for continued funding of Congressionally 

Directed Projects are the prerogative of Congress. 

Although this single-year funded project may 

extend beyond a single-year performance period, 

continued funding by the Solar Program is not 

planned. 

EERE Crosscutting Activities 182
 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

 

Missouri Alternative and Renewable Energy Technology Center 

Performing Organization:	 Crowder College, Neosho, Missouri 

Key Technical Contacts:	 Art Boyt, Crowder, 417-455-5534, aboyt@crowder.edu 

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 2006 Budgets:	 $990K (DOE), $990K (Crowder cost share) 

Objectives 

•	 Design and construct pilot module and Stage 1 of the Missouri Alternative and Renewable Energy 

Center laboratory at Crowder College. 

Accomplishments 

•	 Completed site development plans, structural and building envelope specifications, daylighting 

design, and roof geometry design studies. 

1. Introduction roof geometry design studies have been 

completed. As a result of this design development 

This Congressionally Directed Project is for the activity, Crowder College has decided to comply 

development of a 27,500-square-foot facility that with U.S. Green Building Council guidelines and to 

functions as a living laboratory to support solar apply for LEED (Leadership in Energy and 

and other renewable energy development. This Environmental Design) platinum certification for 

facility will enable professional degrees, new the MARET Center facility. This should impact 

product commercialization, renewables-related positively the next stage of the National 

business incubation, and consumer education. Environmental Policy Act application. 

Construction was delayed pending further design 

2. Technical Approach	 refinement and validation, including daylighting 

simulations. Additional tests were conducted to 

Design Missouri Alternative and Renewable evaluate the structure to develop roof-wall and 

Energy Technology (MARET) Center at Crowder wall-foundation attachment details. 

College by integrating 40% solar design elements 

including: flat-plate silicon PV modules, balance of 4. Future Planned Activities 

systems, solar hot water, combined heating and 

cooling, and advanced building-integrated Plans for continued funding of Congressionally 

concepts (AC building block system, PV/thermal Directed Projects are the prerogative of Congress. 

hybrid system). Although this single-year funded project may 

extend beyond a single-year performance period, 

3. Results and Accomplishments continued funding by the Solar Program is not 

planned. 

Site development plans, structural and building 

envelope specifications, daylighting design, and 

183 EERE Crosscutting Activities
 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

 

Carbon Nanostructure-Based Screens for PV Panels 

Performing Organization:	 University of Arkansas at Little Rock 

Key Technical Contacts:	 Alexandru Biris, U. of Arkansas, 501-569-8210, asbiris@ualr.edu 

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 2006 Budgets:	 $495K (DOE), $124K (U. of Arkansas cost share) 

Objectives 

•	 Develop highly conductive coatings using carbon nanotubes and optically transparent electrodes 

to create an electrodynamic shield to remove particulates from solar panels and optical 

equipment. 

Accomplishments 

•	 Produced carbon nanotube-based, highly conductive polymer coatings with an optical 

transparency greater than 80%. 

1. Introduction nanotubes of reduced electrical resistivity that 

were mixed with polymeric films to produce highly 

This Congressionally Directed Project focuses on conductive polymer coatings with an optical 

studying electrically conductive carbon nanotubes transparency >80%. The polymeric materials 

and their use for building an electrodynamic shield were formed into electrodes, connected to an 

for particulate removal from solar panels and electrical supply, and generate moving electrical 

optical equipment. waves that keep the surface free of particulate 

deposition. 

2. Technical Approach 

4. Future Planned Activities 

Grow high-purity carbon nanotubes, mix with 

polymer materials, and develop coatings with Plans for continued funding of Congressionally 

improved conductivity in a preferential direction for Directed Projects are the prerogative of Congress. 

the electrodynamic screen. Although this single-year funded project may 

extend beyond a single-year performance period, 

3. Results and Accomplishments continued funding by the Solar Program is not 

planned. 

This project successfully completed development 

of high-purity single- and multi-walled carbon 

EERE Crosscutting Activities 184
 

 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

 

 

 

 

Tools for Nanotechnology Education Development Program 

Performing Organization:	 Oregon Nanosciences and Microtechnologies Institute (ONAMI), 

Eugene, Oregon 

Key Technical Contacts:	 Skip Rung, 541-713-1331, skip.rung@oregonstate.edu 

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 2006 Budgets:	 $1,485K (DOE), $513K (ONAMI cost share). 

Objectives 

• Develop tabletop scanning electron microscope for use by postsecondary school students. 

Accomplishments 

•	 Completed design, fabrication, reliability testing, and development of six prototype tabletop 

scanning electron microscopes. 

1. Introduction 3. Results and Accomplishments 

This Congressionally Directed Project is for This project successfully completed design, 

development and delivery of a tabletop scanning fabrication, reliability testing, and development of 

electron microscope. This microscope will be easy six prototype tabletop scanning electron 

to use by non-experts and students, will require no microscopes for use in postsecondary education 

special facilities, and will be affordable to institutions. 

postsecondary educational institutions. . 

4. Future Planned Activities 

2. Technical Approach 

Plans for continued funding of Congressionally 

Develop six prototype scanning electron Directed Projects are the prerogative of Congress. 

microscopes (SEMs), conduct reliability analyses Although this single-year funded project may 

and implement improvements, develop and test extend beyond a single-year performance period, 

SEM classroom simulator, train professors/ continued funding by the Solar Program is not 

technicians on prototypes, and deploy in planned. 

classrooms. 

185 EERE Crosscutting Activities
 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

 

 

 

PV Charging System for Remote Area Operations 

Performing Organization:	 Coherent Systems International, Lexington Park, Maryland 

Key Technical Contacts:	 Alexander Grethe, 407-929-9674, GretheA@coherentsys.com 

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 2006 Budgets:	 $900K (DOE); $224K (Coherent cost share) 

Objectives 

•	 Develop lightweight, remote PV-powered battery charging system generating 5–20 kWh/day for 

first responder and military applications. 

Accomplishments 

• Completed requirements definition for PV charging systems for a variety of remote applications. 

1. Introduction includes charging systems for battery-powered 

military vehicles, off-road electric vehicles, electric 

This is a Congressionally Directed Project for the motorbikes, small water purification systems, 

design and development of a PV charging system portable high-capacity battery packs, and 

for remote-area applications. The charging system emergency radios. Next steps include 

can be used by first responders such as forest fire identification of required technologies; conceptual 

fighters, military, and other emergency personnel. design; system integration, test and validation; and 

For this charging system, PV cells will be conceptual design of a next-generation system. 

developed to operate at greatly reduced irradiance 

levels. 4. Future Planned Activities 

2. Technical Approach	 Plans for continued funding of Congressionally 

Directed Projects are the prerogative of Congress. 

Define requirements for charging systems, Although this single-year funded project may 

benchmark against existing designs, develop extend beyond a single-year performance period, 

conceptual design of a next-generation system, continued funding by the Solar Program is not 

and design a prototype charging system. planned. 

3. Results and Accomplishments 

This project has completed its requirements 

definition for remote PV charging systems. This 

EERE Crosscutting Activities 186
 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

Brightfield Solar Energy 

Performing Organization:	 City of Brockton, Massachusetts 

Key Technical Contacts:	 Michael Thoreson, 508-580-7135, mthoreson@ci.brockton.ma.us 

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 2006 Budgets:	 $693K (DOE), $693K (City of Brockton cost share) 

Objectives 

• Install a 425-kW PV "brightfield" system at a remediated "brownfield" site in Brockton, MA. 

Accomplishments 

• Installed, tested, and transferred operations of a 425-kW PV system at a brownfield site. 

1. Introduction photovoltaic system on a remediated brownfield 

cleanup site in the City of Brockton, MA. 

This is a Congressionally Directed Project to fund 

the purchase and installation of approximately 4. Future Planned Activities 

three-quarters of the solar modules needed for a 

solar array on a “brightfield” site in Brockton, MA. Plans for continued funding of Congressionally 

Directed Projects are the prerogative of Congress. 

2. Technical Approach	 Although this single-year funded project may 

extend beyond a single-year performance period, 

Design, install, test, and transfer to full operation a continued funding by the Solar Program is not 

425-kW PV system on a remediated brownfield planned. 

site in Brockton, MA. 

3. Results and Accomplishments 

This project has completed installation, testing, 

and transfer to operations of a 425-kW 

187 EERE Crosscutting Activities
 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

National Orange Show Photovoltaics Demonstration 

Performing Organization:	 National Orange Show Events Center, San Bernardino, California 

Key Technical Contacts:	 Daniel Jimenez, 909-422-3780, djimenez@nosevents.com 

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 2006 Budgets:	 $445K (DOE), $1,500K (National Orange Show cost share) 

Objectives 

• Install a 400-kW PV system at the National Orange Show Events Center, San Bernardino, CA. 

Accomplishments 

• Completed the design, selected the contractor, and ordered materials for the PV installation. 

1. Introduction installation of a 400-kW PV system on buildings at 

the National Orange Show in San Bernardino, CA. 

This is a Congressionally Directed Project for the Installation and transfer to operation is scheduled 

National Orange Show to support the creation of a to be complete by February 2008. 

400-kW photovoltaic system at its National Orange 

Show Events Center. This PV system is expected 4. Future Planned Activities 

to provide approximately 75% of the center's 

electricity needs. Plans for continued funding of Congressionally 

Directed Projects are the prerogative of Congress. 

2. Technical Approach	 Although this single-year funded project may 

extend beyond a single-year performance period, 

Design, install, test, and transfer to full operation a continued funding by the Solar Program is not 

400-kW PV system on existing National Orange planned. 

Show buildings in San Bernardino, CA. 

3. Results and Accomplishments 

The design has been completed, the contractor 

selected, and the materials ordered for the 

EERE Crosscutting Activities 188
 

 

 

 

____________________________________________________________________________________ 

____________________________________________________________________________________ 

 

 

Photonics Research and Development 

Performing Organization: University of Nevada Las Vegas (UNLV) Research Foundation 

Key Technical Contacts: Wilbur Pittenger, 702-895-2833, bud.pittenger@unlv.edu 

Glenn Doyle, DOE-GO, 303-275-4706, glenn.doyle@go.doe.gov 

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

FY 2006 Budgets: $2,225K (DOE), $556K (UNLV cost share) 

Objectives 

•	 Develop quantum dot light-emitting diodes (QDLEDs). 

•	 Demonstrate commercial feasibility of hybrid solar lighting. 

Accomplishments 

•	 Developed a new method for fabricating QDs that allows for integration with the LED, improved 

material quality, and improved QD surface properties. 

1. Introduction 

This is a Congressionally Directed Project to 

continue the UNLV Research Foundation efforts to 

perform comprehensive R&D focused on 

improving light-emitting diode (LED) technologies 

and hybrid solar lighting. 

2. Technical Approach 

Conduct research on green-wavelength QDLEDs 

using InGaN; research LEDs that use solar light 

source; pilot test hybrid solar lighting including 

task lighting for students. 

3. Results and Accomplishments 

Progress continues on researching QDLEDs that 

can be tunable over a wide spectrum and achieve 

red, green, and blue colors using the same 

materials. A new method for fabricating the QDs 

allows for integration with the LED, improved 

material quality, and improved QD surface 

properties. Research into green QDLEDs using 

InGaN QDs aimed at increasing the quantum 

efficiency by 2X continues to progress. Research 

continues on polymer fiber optics materials that 

would facilitate carrying sunlight through hybrid 

solar lighting a distance of 65 feet with minimal 

losses in the visible wavelength. 

4. Future Planned Activities 

Plans for continued funding of Congressionally 

Directed Projects are the prerogative of Congress. 

Although this single-year funded project may 

extend beyond a single-year performance period, 

continued funding by the Solar Program is not 

planned. 

. 

189 EERE Crosscutting Activities
EERE Crosscutting Activities 190
 

 

 

 

Performing Organizations By Name 

NAME PAGE 

American Solar Energy Society................ 164
 

Amonix, Inc......................................... 49, 177
 

Antares ..................................................... 149
 

Arizona Public Service.............................. 124
 

Arizona State University/UL........................ 50
 

Behnke, Erdman & Whitaker Engineering.. 87
 

Bennett Mirrors ......................................... 149
 

BP Solar International, Inc.................... 77, 78
 

Brookhaven National Laboratory (BNL) ..... 24
 

Building Science Corporation ................... 144
 

California Institute of Technology

 (Caltech)........................................... 33, 49
 

Carnegie Mellon University......................... 98
 

Central State University.............................. 50
 

City of Brockton ........................................ 187
 

City of Tucson........................................... 144
 

Clean Power Research............................... 94
 

Coherent Systems International ............... 186
 

Colorado Code Consulting, LLC................. 98
 

Colorado State University........................... 60
 

Concurrent Designs.................................. 144
 

Cornell University........................................ 98
 

Crowder College....................................... 183
 

Crystal Systems........................................ 177
 

Davis Energy Group/SunEarth ................. 138
 

Distributed Power, Inc. ............................. 177
 

DOE Golden Field Office 

(DOE/GO)..............28, 52, 84, 95, 103, 159
 

DOE HQ and Regional Offices................. 100
 

DOE HQ Solar Energy Technologies

 Program................................................. 175
 

Dow Corning Corporation ........................... 78
 

Eikos, Inc. ................................................. 179
 

Energy Conversion Devices ....................... 77
 

Energy Laboratory Inc. ............................. 144
 

Energy Photovoltaics.................................. 60
 

Energy Strategy Associates ..................... 158
 

Erickson, David......................................... 144
 

Evergreen Solar, Inc................................... 78
 

FAFCO, Inc............................................... 138
 

First Solar, LLC..................................... 60, 78
 

Fisk University ............................................ 50
 

Florida Solar Energy Center ........ 60, 61, 106
 

GE Energy, LLC.......................................... 78
 

General Electric .......................................... 69
 

Georgia Institute of Technology
 

(Georgia Tech) ........................... 33, 49, 98
 

Gilman, Paul ............................................. 158
 

Global Solar Energy ................................... 61
 

GT Equipment........................................... 177
 

Howard University....................................... 50
 

Industrial Solar Technology...................... 124
 

NAME PAGE 

Institute for Sustainable Power .................167 

International Solar Electric Technologies....61 

Interstate Renewable Energy Council 

 (IREC) ....................................100, 102, 164
 

Janzou Consulting.....................................158
 

JX Crystals ..................................................49
 

Kansas State University..............................98
 

Latent Structures, LLC ..............................124
 

Lawrence Berkeley National
 

Laboratory (LBNL) ...................................94 

Lawrence Technological University ............98 

Massachusetts Institute of 

Technology .............................................98
 

MetroLaser, Inc. ........................................177
 

Microcell Technologies..............................177
 

Midwest Optoelectronics...........................178
 

Morse Associates, Inc ...............................131
 

MRG & Associates ..............................94, 131
 

NanoSolar ...........................................61, 177
 

NanoSonic, Inc..........................................178
 

National Energy Technology
 

Laboratory (NETL) .........................100, 159 

National Orange Show Events Center ......188 

National Renewable Energy Laboratory 

(NREL) ...............................4, 20, 28, 34, 44
 

52, 62, 70, 84, 88, 91, 95, 100, 115, 125, 

129, 134, 139, 153, 159, 165, 168, 179 

New York Institute of Technology ...............98 

Nexant.......................................................124 

North Carolina A&T State University...........50 

North Carolina Central University ...............50 

North Carolina State University (NCSU) .....33 

Northwestern University..............................50 

Oak Ridge National Laboratory (ORNL) ...145 

Ohio State University ..................................50 

Oregon Nanosciences and 

Microtechnologies Institute (ONAMI).....185 

Oregon State University..............................49 

Pacific Northwest National Laboratory

 (PNNL) .....................................................61
 

Pennsylvania State University.....................98
 

PowerLight Corporation ..............................78
 

PowerMark Corporation ..............................87
 

Princeton University ....................................50
 

Puget Sound Energy.................................144
 

Quest Energy Group .................................144
 

Rensselaer Polytechnic Institute (RPI) .....182
 

Sandia National Laboratories
 

(SNL)............... 62, 66, 80, 84, 91, 100, 103
 

112, 115, 129, 142, 153, 159, 165, 168 

Santa Clara University ................................98 

Schott Solar, Inc..........................................78 
 

 

 

NAME PAGE 

Segue Energy Consulting, LLC ........ 102, 167
 

SENTECH, Inc.................................... 94, 144
 

Shell Oil .................................................... 144
 

Shell Solar Industries.................................. 61
 

Shingleton Design LLC............................... 78
 

Solargenix Energy .................................... 124
 

SolarWorld Industries America................... 78
 

Southern University and A&M College ....... 50
 

Southwest Technology Development 

 Institute (SWTDI)................................... 106
 

Specialized Technology Resources, Inc. ... 78
 

Spectrolab, Inc............................................ 49
 

Spire Corporation........................................ 77
 

SRCC................................................ 138, 144
 

State University of New York (SUNY),

 Albany...................................................... 23
 

SunPower Corporation ............................... 78
 

Sunset Technologies .................................. 87
 

Syracuse University.................................... 61
 

TDA Research .......................................... 177
 

Team Montreal............................................ 98
 

Technische Universität Darmstadt.............. 98
 

Texas A&M University .......................... 61, 98
 

Texas Tech................................................. 33
 

Thermal Energy System Specialists, Inc.. 138
 

United Solar Ovonic.................................... 61
 

United States Air Force ............................ 144
 

Universidad de Puerto Rico........................ 99
 

Universidad Politécnica de Madrid ............. 98
 

University of Arkansas, Little Rock........... 184
 

University of California, Berkeley................ 33
 

University of Cincinnati ............................... 99
 

University of Colorado, Boulder............ 50, 99
 

University of Delaware.......................... 49, 50
 

University of Delaware, Institute of Energy
 

Conversion .............................................. 61
 

University of Illinois..................................... 99
 

University of Maryland ................................ 99
 

University of Minnesota ............................ 138
 

University of Missouri – Rolla ..................... 99
 

University of Nevada, Las Vegas
 

(UNLV)..................................................... 61
 

University of Nevada, Las Vegas
 

(UNLV) Research Foundation............... 189
 

University of New Mexico ......................... 144
 

University of Oregon............................. 49, 61
 

University of Oregon Solar Monitoring 

Laboratory ............................................... 23
 

University of South Florida ......................... 61
 

University of Tennessee ........................... 149
 

University of Texas, Austin ......................... 99
 

University of Texas, Brownsville................. 50
 

University of Texas, El Paso....................... 50
 

University of Toledo.............................. 49, 61
 

University of Utah ....................................... 61
 

NAME PAGE 

University of Wisconsin, Madison .............158
 

UQM Technologies ...................................177
 

Wakonda Technologies, Inc......................178
 

Xantrex Technologies, Inc.....................69, 78
 
 

Performing Organizations By State/Country
 

NAME PAGE 

ARIZONA 

Arizona Public Service.............................. 124 

Arizona State University/UL........................ 50 

City of Tucson........................................... 144 

Global Solar Energy ................................... 61 

PowerMark Corporation.............................. 87 

Sunset Technologies .................................. 87 

ARKANSAS 

University of Arkansas, Little Rock........... 184 

CALIFORNIA 

Amonix, Inc......................................... 49, 177 

Behnke, Erdman & Whitaker Engineering.. 87 

California Institute of Technology
 

(Caltech)............................................ 33, 49
 

Clean Power Research............................... 94 

Davis Energy Group/SunEarth ................. 138 

Distributed Power, Inc. ............................ 177 

Erickson, David......................................... 144 

FAFCO, Inc............................................... 138 

International Solar Electric Technologies ... 61 

Lawrence Berkeley National
 

Laboratory (LBNL)................................... 94 

MetroLaser, Inc......................................... 177 

MRG & Associates.............................. 94, 131 

NanoSolar........................................... 61, 177 

National Orange Show Events Center...... 188 

Nexant ...................................................... 124 

PowerLight Corporation.............................. 78 

Santa Clara University................................ 98 

Shell Solar Industries.................................. 61 

SolarWorld Industries America................... 78 

Spectrolab, Inc............................................ 49 

SunPower Corporation ............................... 78 

University of California, Berkeley................ 33 

Xantrex Technologies, Inc. ................... 69, 78
 

CANADA 

Team Montreal............................................ 98 

COLORADO 

American Solar Energy Society................ 164 

Colorado Code Consulting, LLC................. 98 

Colorado State University........................... 60 

DOE Golden Field Office 

(DOE/GO)..............28, 52, 84, 95, 103, 159 

Industrial Solar Technology...................... 124 

Institute for Sustainable Power................. 167 

Janzou Consulting .................................... 158 

Latent Structures, LLC.............................. 124 

NAME PAGE 

National Renewable Energy Laboratory 

(NREL) ...............................4, 20, 28, 34, 44 

52, 62, 70, 84, 88, 91, 95, 100, 115, 125, 

129, 134, 139, 153, 159, 165, 168, 179 

Quest Energy Group .................................144 

TDA Research...........................................177 

University of Colorado, Boulder ............50, 99
 

UQM Technologies ...................................177 

CONNECTICUT 

Specialized Technology Resources, Inc.....78 

DELAWARE 

GE Energy, LLC ..........................................78 

University of Delaware ..........................49, 50
 

University of Delaware, Institute of Energy
 

Conversion...............................................61 

DISTRICT OF COLUMBIA 

DOE HQ and Regional Offices .................100 

DOE HQ Solar Energy Technologies
 

Program .................................................175 

Gilman, Paul..............................................158 

Howard University .......................................50 

Morse Associates, Inc ...............................131 

United States Air Force.............................144 

FLORIDA 

Energy Laboratory Inc...............................144 

Florida Solar Energy Center
 

(FSEC) .......................................60, 61, 106 

Segue Energy Consulting .................102, 167 

SRCC ................................................138, 144 

University of South Florida..........................61 

GEORGIA 

Georgia Institute of Technology
 

(Georgia Tech).............................33, 49, 98
 

GERMANY 

Technische Universität Darmstadt ..............98 

ILLINOIS 

Northwestern University..............................50 

University of Illinois .....................................99 

KANSAS 

Kansas State University..............................98 

LOUISIANA 

Southern University and A&M College........50 
 

 

 

NAME PAGE 

MARYLAND 

Antares ..................................................... 149 

BP Solar International, LLC .................. 77, 78
 

Coherent Systems International ............... 186 

Energy Strategy Associates ..................... 158 

SENTECH, Inc. .................................. 94, 144 

University of Maryland ................................ 99 

MASSACHUSETTS 

Building Science Corporation ................... 144 

City of Brockton ........................................ 187 

Crystal Systems........................................ 177 

Eikos, Inc. ................................................. 179 

Evergreen Solar, Inc................................... 78 

Massachusetts Institute of Technology
 

(MIT)........................................................ 98 

Microcell Technologies ............................. 177 

Schott Solar, Inc. ........................................ 78 

Spire Corporation........................................ 77 

MICHIGAN 

Dow Corning Corporation ........................... 78 

Energy Conversion Devices ....................... 77 

Lawrence Technological University............ 98 

United Solar Ovonic.................................... 61 

MINNESOTA 

University of Minnesota ............................ 138 

MISSOURI 

Crowder College....................................... 183 

University of Missouri - Rolla...................... 99 

NEVADA 

University of Nevada, Las Vegas 

(UNLV)..................................................... 61 

University of Nevada, Las Vegas (UNLV)
 

Research Foundation ............................ 189 

NEW HAMPSHIRE 

GT Equipment........................................... 177 

NEW JERSEY 

Energy Photovoltaics, Inc. .......................... 60 

Princeton University.................................... 50 

NEW MEXICO 

Sandia National Laboratories 

(SNL) ...............62, 66, 80, 84, 91, 100, 103
 

112, 115, 129, 142, 153, 159, 165, 168 

Southwest Technology Development 

 Institute (SWTDI)................................... 106 

University of New Mexico ......................... 144 

NAME PAGE 

NEW YORK 

Brookhaven National Laboratory (BNL) ......24 

Cornell University ........................................98 

General Electric...........................................69 

Interstate Renewable Energy Council 

 (IREC) ....................................100, 102, 164 

New York Institute of Technology ...............98 

Rensselaer Polytechnic Institute (RPI) .....182 

Shingleton Design LLC ...............................78 

State University of New York (SUNY),

 Albany ......................................................23 

Syracuse University ....................................61 

Wakonda Technologies, Inc. ....................178 

NEW ZEALAND 

Bennett Mirrors..........................................149 

NORTH CAROLINA 

North Carolina A&T State University...........50 

North Carolina Central University ...............50 

North Carolina State University (NCSU) .....33 

Solargenix Energy.....................................124 

OHIO 

Central State University ..............................50 

First Solar, LLC .....................................60, 78
 

Midwest Optoelectronics ...........................178 

Ohio State University ..................................50 

University of Cincinnati................................99 

University of Toledo ..............................49, 61
 

OREGON 

Oregon Nanosciences and Microtechnologies 

Institute (ONAMI) ...................................185 

Oregon State University..............................49 

University of Oregon .............................49, 61
 

University of Oregon Solar Monitoring 

Laboratory................................................23 

PENNSYLVANIA 

Carnegie Mellon University .........................98 

National Energy Technology Laboratory
 

(NETL) ...........................................100, 159 

Pennsylvania State University.....................98 

PUERTO RICO 

Universidad de Puerto Rico ........................99 

SPAIN 

Universidad Politécnica de Madrid..............98 

TENNESSEE 

Fisk University.............................................50 

Oak Ridge National Laboratory (ORNL) ...145 

University of Tennessee............................149 
 

NAME PAGE 

TEXAS 

Concurrent Designs.................................. 144 

Shell Oil .................................................... 144 

Texas A&M University .......................... 61, 98
 

Texas Tech................................................. 33 

University of Texas, Austin ......................... 99 

University of Texas, Brownsville................. 50 

University of Texas, El Paso....................... 50 

UTAH 

University of Utah ....................................... 61 

VIRGINIA 

NanoSonic, Inc. ....................................... 178 

WASHINGTON 

JX Crystals.................................................. 49 

Pacific Northwest National Laboratory
 

(PNNL)..................................................... 61 

Puget Sound Energy ................................ 144 

WISCONSIN 

Thermal Energy System Specialists, Inc. 138 

University of Wisconsin, Madison............. 158 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A2LA 

AC 

AES 

AFM 

AIC 

ALO 

AOP 

APD 

APS 

AR 

ASES 

ASHRAE 

a-Si 

ASOS 

ASRC 

ASRM 

ASSET 

ASTM 

ASU 

BES 

BEW 

BIPV 

BLM 

BNL 

BOS 

BSC 

BSF 

Btu 

BU 

CAD 

C-AFM 

Caltech 

CBD 

CdTe 

CEC 

CET 

CIGS 

CIGSS 

CIS 

CL 

CNT 

COP 

COSE 

COTS 

CPS 

CPUC 

CPV 

CRADA 

Csave 

CSDS 

c-Si 

CSR 

Acronyms and Abbreviations 

American Association for Laboratory Accreditation 

alternating current 

Auger electron spectroscopy 

atomic force microscopy 

aluminum-induced crystallization 

Albuquerque Operations Office (U.S. Department of Energy) 

Annual Operating Plan 

antiphase domain 

Arizona Public Service 

antireflection 

American Solar Energy Society 

American Society of Heating, Refrigeration, and Air-conditioning Engineers 

amorphous silicon 

Automated Surface Observing System 

Atmospheric Sciences Research Center (at State University of New York) 

advanced solar reflective mirror 

Analysis of State Energy Tradeoffs Databank 

American Society for Testing and Materials 

Arizona State University 

Basic Energy Sciences (within U.S. DOE Office of Science) 

Behnke, Erdman & Whitaker Engineering 

building-integrated photovoltaics 

Bureau of Land Management 

Brookhaven National Laboratory 

balance of systems 

Basic Sciences Center (within the National Renewable Energy Laboratory) 

back-surface field 

British thermal unit 

Boston University 

computer-assisted design 

conductive atomic force microscopy 

California Institute of Technology 

chemical bath deposition 

cadmium telluride 

California Energy Commission 

Center for Ecological Technology 

copper indium gallium diselenide 

copper indium gallium sulfur selenide 

copper indium diselenide 

cathodoluminescence 

carbon nanotube 

coefficient of performance 

cost of saved energy 

commercial off the shelf 

Corporate Planning System 

California Public Utilities Commission 

concentrating photovoltaics 

Cooperative Research and Development Agreement 

cost of saved energy 

Concentrating Solar Deployment System 

crystalline silicon 

Climatological Solar Radiation 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CSS close-spaced sublimation 

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 Federal 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 

GPS Global Positioning System 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

GSE 

GW 

HALT 

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 

LED 

LEED 

LIPA 

Global Solar Energy 

gigawatt 

highly accelerated lifetime testing 

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 

light-emitting diode 

Leadership in Energy and Environmental Design 

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 

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 

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 

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 

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) 

SAIC Science Applications International Corporation 

SAM Solar Advisor Model 

SBC systems benefit charge 

SBIR Small Business Innovation Research 

SDA Systems-Driven Approach 

SDHW solar domestic hot water 

SDSU South Dakota State University 

SEGS Solar Energy Generating 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 

TW terrawatt 

UHV ultrahigh vacuum 

UL Underwriters Laboratories 

ULRF University of Louisville Research Foundation 

UN United Nations 

UNLV University of Nevada Las Vegas 

UNM/ME University of New Mexico Mechanical Engineering Department 

U of L University of Louisville 

UPS ultraviolet photoelectron spectroscopy 
 

 

 

 

 

 

USAID U.S. Agency for International Development 

USDA U.S. Department of Agriculture 

USGBC U.S. Green Building Council 

UV ultraviolet 

VASE variable-angle spectroscopic ellipsometry 

VB valence band 

VBM valence band maximum 

Voc open-circuit voltage 

VSHOT Video Scanning Hartmann Optical Test 

VTD vapor transport deposition 

WCPEC World Conference on Photovoltaic Energy Conversion 

WGA Western Governors' Association 

WIP-I Weatherization and Intergovernmental Program-International 

WMO World Meteorological Organization 

WOM weatherometer 

WREC World Renewable Energy Congress 

WRR World Radiometric Reference 

WVTR water vapor transport rate 

XPS X-ray photoelectron spectroscopy 

XRD X-ray diffraction 

YDR yield, durability, and reliability 

ZEH zero energy homes 

 

 

 

 

 

 

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