Subcontract Report

NREL/SR-520-47310

December 2009

Reflective Optics CPV Panels 

Enabling Large Scale, Reliable 

Generation of Solar Energy Cost 

Competitive with Fossil Fuels 

15 November 2007 – 30 June 2009

S. Horne, M. McDonald, N. Hartsoch, and 

K. Desy

SolFocus, Inc. 

Mountain View, California
National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401-3393

303-275-3000 • www.nrel.gov

NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency and Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

Contract No. DE-AC36-08-GO28308

Subcontract Report

NREL/SR-520-47310

December 2009

Reflective Optics CPV Panels 

Enabling Large Scale, Reliable 

Generation of Solar Energy Cost 

Competitive with Fossil Fuels 

15 November 2007 – 30 June 2009

S. Horne, M. McDonald, N. Hartsoch, and 

K. Desy

SolFocus, Inc. 

Mountain View, California

NREL Technical Monitor: Brian Keyes

Prepared under Subcontract No. NAT-7-77015-09
This publication was reproduced from the best available copy

submitted by the subcontractor and received no editorial review at NREL

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iii

Table of Contents

Introduction .................................................................................................................................................. 1

Phase I........................................................................................................................................................... 2

Task 1 - Improve Efficiency and Reliability of Module Design .................................................................. 2

Overview ............................................................................................................................................... 2

Subtask 1.1 - Develop Higher Efficiency Optics .................................................................................... 3

Subtask 1.2 - Enhancing Reflectivity and Increasing Durability of Mirror Coating Process & Subtask 

1.3 - Development of Anti-reflection Coatings..................................................................................... 3

Subtask 1.4 - Increase Durability of Optics........................................................................................... 4

Subtask 1.5 - Improved Sealing of Module Enclosure .......................................................................... 5

Subtask 1.6 - Group III-V PV Cell Performance Monitoring and Test Development............................. 5

Task 2 - Reliability Validation .................................................................................................................... 6

Overview ............................................................................................................................................... 6

Subtask 2.1 - FMEA Analysis of Thermal Path, Mirror and Panels (UTRC)............................................ 7

Task 3 - Development of Processes and Equipment for High Volume, Low-Cost Manufacturing............ 7

Overview ............................................................................................................................................... 7

Subtask 3.1 - Mirror Fabrication ........................................................................................................... 7

Subtask 3.2 - III-V PV Cell Manufacturing Capacity and Cost Reductions............................................. 8

Subtask 3.3 - Module Assembly ............................................................................................................ 8

Stage Gate Review .................................................................................................................................... 9

Phase II........................................................................................................................................................ 10

Task 4 – Reliability Validation ................................................................................................................. 10

Overview ............................................................................................................................................. 10

Subtask 4.1 - IEC Qualification ............................................................................................................ 11

Subtask 4.2 - Highly Accelerated Stress Test (HAST) & Subtask 4.3 - Correlation of HALT with Field 

Test Results using Analytical Model.................................................................................................... 11

Task 5 – Manufacturing Readiness ......................................................................................................... 12

Overview ............................................................................................................................................. 12

Subtask 5.1 - Supply Chain.................................................................................................................. 13

Subtask 5.2 - Factory/Assembly.......................................................................................................... 13

Summary ..................................................................................................................................................... 15
iv
1

Shown to left: SolFocus SF-1100 

optical system utilizing primary and 

secondary mirrors and optical rod 

are combined with high-efficiency 

multi-junction PV cells to form a 

power unit. Twenty power units are 

integrated into a panel, and then 28 

panels are integrated on a dual axis 

tracker for field deployment. 

Introduction

The objective of this 18 month subcontract was the improvement of reflective optics CPV panels to 

enable the large-scale, reliable production of solar electricity to meet SAI-established LCOE targets, and 

ultimately provide a path to solar power at parity with or better than the cost of energy generated 

utilizing fossil fuels. To this end, SolFocus has completed this subcontract with great success as 

evidenced by the end results of a CPV panel with conversion efficiencies greater than the targeted 22% 

and manufacturing capabilities with a run rate capacity far exceeding the milestone benchmark >3MW. 

Phase I of the subcontract focused on improving the panel efficiency, reliability, and overall module 

performance. Phase II of the subcontract focused on the development of processes and equipment for 

high volume, low-cost manufacturing through automated fabrication of optics and panels to improve 

the speed of manufacture and quality control. This summary report accompanies the final presentation 

for Subcontract NAT-7-77015-09 presented at the National Renewable Energy Laboratory in Golden 

Colorado on June 29, 2009.
2

Optical architecture redesign from hexagonal to quadrangle shaped 

optics

Phase I

The first objective of Phase I was the development of an efficient and reliable module design with better 

than 1% annual degradation. Work commenced in six different areas to accomplish this objective 

including: developing higher efficiency optics, enhancing reflectivity and durability of the mirror 

coatings, developing anti-reflection coatings, increasing the durability of the optics, improving the 

sealing of the module enclosure, and III-V PV Cell performance monitoring/test development. 

Task 1 - Improve Efficiency and Reliability of Module Design

Overview

The overall objective of this task was to 

minimize the wasted space in a concentrator 

panel and to maximize the efficiency of the 

optical path to the multi-junction PV cell. The 

first subtask was to develop higher efficiency 

optics. To accomplish this, SolFocus redesigned 

the shape of the primary mirror from a hexagon

to a square and enhanced the reflectivity of the 

optics through improved Silvering techniques. 

By working with vendors, the durability of these 

coatings was improved until satisfactory longevity 

was shown for both primary and secondary mirrors. 

Lastly, anti-reflection coatings on the transmissive elements further improved efficiency. Fabrication 

was to be completed at SolFocus Glassworks facility in Mesa, Arizona. The two silvering technologies 

evaluated were sputtered first surface silver and liquid applied protected second surface silver. Due to 

the market-ready availability of the first surface coating, this is the coating that was selected; however, 

the flexibility to switch to a potentially less costly second surface method is available once this 

technology has advanced. Further HAST research and testing in the area of optics durability indicated 

that the glass and the coatings are sufficiently robust to maintain the integrity of the optic.

Sealing was another module-level enhancement included in this subcontract, which would improve 

overall module performance and field life durability. Breathing and sealing measures that allow the 

module to maintain a clean and moisture controlled environment were tested in both lab and field tests 

in various extreme climates such as tropical, maritime, desert, and moderate/mixed weather environs. 

An improved sealing technology that could pump out excess moisture was implemented.
3

The final subtask of the first task was to model the multi-junction cell performance and project the 

variation in cell performance as a function of various environmental factors and to develop test 

methodologies to be able to predict field life and performance. SolFocus gathered test data and 

modeled Dark and Lit IV curves and HiPot testing at the cell level to determine leakage, fill factor and 

peak performance. To enable this, a cell flash tester was developed, which continues to be used for

testing cell and receiver performance.

Subtask 1.1 - Develop Higher Efficiency Optics

A variety of rough optical shapes and designs were evaluated through a series of simulation tests and 

lab tests. A square mirror was determined an optimal fit in the rectangle module and glass processing 

allowed for the efficient manufacture of a square aperture. The secondary mirror shape was also 

altered to a square design, which when combined with the square aperture of the secondary mirror, 

minimized shadowing. A report of the evaluation was submitted to NREL on March 15, 2008. 

Subtask 1.2 - Enhancing Reflectivity and Increasing Durability of Mirror Coating Process & 

Subtask 1.3 - Development of Anti-reflection Coatings

These two subtasks are being reported together as they were done simultaneously. The engineering 

team worked with various vendors and fabricators of mirror coatings to evaluate samples for enhanced, 

durable reflectivity of the primary mirror collector. SolFocus engineers analyzed various mirror coatings 

looking for a coating that would provide highly efficient, specular reflectance across the solar spectrum,

and maintain durability. A report outlining the analysis and conclusions of this selection process was 

submitted as part of deliverable 3.1.2 and a primary optic with the selected coating was delivered to 

NREL in April 2008. SolFocus decided that the best course of action was to use a sputtered, protected 

first surface Silver due to its high reflectivity, durability, and market readiness. The first surface primary 

mirror with enhanced reflectivity coatings yielded approximately 6% higher relative reflectivity and 

simulations using the anti-reflective coating indicated 80% potential optical efficiency with an 

acceptance angle of +/- 1 degree. Fabrication of these primary mirrors, incorporating the improved 

coating, is being done in-house at our Glassworks facility in Mesa, Arizona. 
4

Subtask 1.4 - Increase Durability of Optics

In addition to enhancing reflectivity, the reflector substrates were also analyzed for durability and 

reliability. Research and testing in the area of optics durability indicated that the glass and first surface

coatings are sufficiently robust to maintain the optics’ integrity. Various reflecting material substrates 

were tested and glass consistently yielded the best results. A specific issue of localized degradation and 

damage arose when systems were operated for prolonged periods of time off-axis. A Tiger Team 

dedicated to the issue found that the best remedy for this issue was a combination of preventative 

measures at the system level and improved thermal management on the mirror itself. 

0

5

10

15

20

25

30

90.0%91.3%92.5%93.7%95.0%96.2%97.5%98.7%

100.0%101.3%102.5%103.7%105.0%106.3%107.5%

Frequency

Reflectivity, % of average Second Surface results

SolFocus Primary Mirror reflectivity,

First Surface process vs original Second Surface process

First Surface

Second surface

100% chosen as 

average of 

Second Surface

test results.

Test results, first surface vs. second surface reflectivity

Left: Summary flowchart used by SolFocus to estimate component and module lifetime. Right: Graph showing secondary mirror lifetime extrapolation. Under 

normal operating conditions; graph indicates and average 33 year lifetime 
5

A second issue arose with the integrity of the adhesive of the secondary mirror to the front glass. Excess 

energy was absorbed due to the dark coloring of the adhesive; a switch to a white colored adhesive with 

increased reflectivity eliminated this issue.

Subtask 1.5 - Improved Sealing of Module Enclosure

The initial module sealing technology used in the first generation of this product was ineffective and 

allowed moisture to accumulate inside the module. Different breathing and moisture control measures 

were tested in the lab and field testing in different geographies measured the impact of varying external 

climactic factors inherent to targeted geographic location. A redesigned vent that pumps moisture out 

of the module was implemented into this generation of the module. 

Subtask 1.6 - Group III-V PV Cell Performance Monitoring and Test Development

The objective of this task was to determine multi-junction cell performance in order to project the 

variation in cell performance as a function of different environmental factors. SolFocus developed test 

methodology approaches and tested both modules and cells using flash testers. A full report detailing 

Left: Secondary mirror with 

dark adhesive. Right: 

Secondary mirror using 

adhesive with increased 

reflectivity.

Left: Image of new venting system design. Right: Test results of various venting schemes.
6

these methodologies and preliminary results with regards to modeling of a Dark and Lit IV curves, HiPot 

testing, and determination of leakage were outlined in deliverable 3.1.4 submitted in April 2008.

The III‐V PV cell performance, reliability, and flux were tested in house at SolFocus facilities and at NREL. 

III‐V cell performance, Dark IV leakage and HiPot were measured at the cellular level by a multi‐sun flash 

tester and the performance of the III‐V cell as part of the receiver and module were tested by a module 

flash tester. A Dark IV test method was developed to test the cell sub assembly by biasing the cell subassembly, to heat and with current ramp to 5 amps. Through this we developed the following factory 

qualification parameters: 

Fail at the factory:

Fail low >10 mA at 2.2V

Fail high >3.8V at 5A

Task 2 - Reliability Validation

Overview

The objective of this task was to determine the likely failure modes and test protocols for the thermal 

path, mirrors, and panel. Subtasks under this task included: analyzing mirror coatings and identifying

appropriate testing and validation protocols for the reliability of coatings; analyzing fully assembled 

panels and identifying appropriate testing and validation protocols that need to be completed to 

Cell and wafer testing apparatus and test output.
7

demonstrate target reliability for panels; and analyzing thermal paths to validate existing testing and 

modeling methods to verify that cell/heat transfer surface interface meets reliability metrics. Failure 

Mode Effects Analysis (FMEA) was performed at both the component and panel levels, critical failure

modes were identified, validation/test protocols were created, and modeling methods outlining the 

analyses for each of the above areas were submitted to NREL. Testing is ongoing and has been crucial in 

directing the industrialization effort. 

Subtask 2.1 - FMEA Analysis of Thermal Path, Mirror and Panels (UTRC)

Work in this area commenced earlier than outlined in the SOW, as SolFocus felt that testing protocols 

and reliability targets for these components was critical in the path towards IEC certification. SolFocus 

engineers utilized a Design Failure Mode Effects Analysis (dFMEA) to find design risks and prioritize 

mitigation. dFMEA metrics and rankings were applied to all optical coatings, all optical substrates, the 

backpan, the receiver, adhesive system, thermal paths, tracker mechanics, and the tracker control 

system.

Task 3 - Development of Processes and Equipment for High Volume, Low-Cost 

Manufacturing

Overview

The objective of this task was to automate the fabrication process for the primary optics (mirrors) in 

order to improve speed of manufacture and quality control, resulting in achievement of specifications 

for smoothness and improved cost targets. The SolFocus Glassworks facility in Mesa, Arizona is

evidence of the completion of this task. To achieve targets for this task, Mesa Glassworks expanded 

capability to include Lehr ovens, batch slump ovens, water jet cutting, a rotary oven, and semiautomated silvering procedures. Production capacity increased from a 2MW capacity in 2008 to a 

34MW capacity by April 2009. This manufacturing expansion is expected to produce 15MW of primary 

reflectors in 2009 and more than double that capacity in 2010. Primary mirror fabrication costs are

critical to reducing LCOE of SolFocus CPV systems.

Subtask 3.1 - Mirror Fabrication

Work toward this subtask also commenced ahead of schedule. Batch slump ovens were put into 

operation with optimized process parameters. A batch coating machine was developed by our 

manufacturing partner and implemented at Glassworks. By moving primary mirror fabrication in-house, 

SolFocus was able to achieve a higher level of quality and run consistency of the primary optics 

compared to the original vendor. The SolFocus Glassworks facility came online in mid-year 2008 with a 

theoretical production capacity of 2MW; 45,000 primary mirrors were produced in 2008. In March of 
8

2009, Glassworks expanded and increased its automated production capabilities; this expansion has a 

production capacity of 34MW and is estimated to produce 1.2 million mirrors this year.

Subtask 3.2 - III-V PV Cell Manufacturing Capacity and Cost Reductions

SolFocus engineering team actively engaged with III-V PV cell manufacturers in order to assure quality 

and supply of cells to meet CPV module design requirements for functionality. SolFocus decided the 

most cost-effective approach would be to source III-V cells from manufacturers and not bring this 

capability in-house. This is an ongoing process and the collaborative work in this area continues, but 

SolFocus has contracted to source all the cells necessary to meet its contracts in 2009 and 2010.

Subtask 3.3 - Module Assembly

This task incorporated all of the tasks and subtasks outlined in Phase I and was the last step before 

moving into the work outlined in Phase II. SolFocus completed significant work with manufacturing 

automation partner Meikle to design the necessary alignment tooling and manufacturing processes to

achieve consistent quality and accuracy of high volume manufacturing. This process began in late 2007 

and came to fruition in April 2009 with a pilot run of a fully automated panel assembly line in Rochester, 

NY.

Left: Rotary batch oven. Right: Rotary coating applicator.

The Kuka robotic arm is the 

key to the automated Meikle 

panel assembly line.
9

Stage Gate Review

A final Stage Gate report was delivered to NREL on July 16, 2008 detailing the measured performance of 

the module delivered to NREL on July 9, 2008. The improvements to the performance and efficiency of 

the CPV panel resulted in a CPV panel that met and exceeded the metrics listed below.

The target metrics at the Stage Gate at the end of Phase I:

Optical efficiency: 74%

Power unit efficiency: 25%

Module efficiency: 18% 

Acceptance angle: +/- 0.75 degree

Cell temperature 550C over ambient

Module degradation of 1% - 2% per K

Measured outputs at the Stage Gate:

Optical efficiency: EQE and high solar resource range 400 to 1350 nm, exceeds 74%

Power unit efficiency: 27.0%

Module efficiency: 25.3%

Acceptance angle: >1 degree

Cell temperature: 50.80C to 53.90C

Module degradation: 1.2% per K

End product efficiency comparison of SolFocus CPV with other best in class PV technologies
10

Phase II

The Second Phase had two objectives. The first objective of Phase II was focused on the complete indepth reliability validation on the CPV module, which included Highly Accelerated Life Test (HALT), a 

correlation of HALT results with field test results, and group III-V PV cell accelerated life testing. The 

second objective of Phase II was focused on ramping up overall manufacturing processes and equipment 

in order to transition from prototype manufacturing to high volume manufacturing. The expected 

results by the end of the grant project were to have a run rate of greater than 3MW with module 

manufacturing cost <$5/Watt. A third party validation of module manufacturing costs was performed 

by Navigant Consulting, and based on their analysis, SolFocus exceeded the goal of <$5/Watt 

manufacturing costs. The manufacturing accomplishments are described in detail below.

Task 4 – Reliability Validation

Overview

Passing IEC test specifications is critical in achieving market penetration and acceptance in the United 

States and other countries. SolFocus completed all of the tests related to IEC 62108 internally and is

only awaiting the final outdoor test results ( a six-month process due late July 2009) prior to obtaining 

certification from TUV to IEC 62108. In June 2009, SolFocus became the first CPV company to receive 

certification to IEC 62108, which they achieved on the first generation SF1000 product. All lessons 

learned from that effort were applied to the SF1100 system, and testing has gone very smoothly on the 

new product. SolFocus has also received listing on the SF1100 panel on the California Energy 

Commission (CEC) approved list qualified equipment for California Solar Initiative (CSI) rebates governed 

by the California Public Utilities Commission. This listing requires certification by TUV to safety 

standards. SolFocus is also the only CPV company to be listed on the CEC’s approved equipment list.

The implementation of an extensive Highly Accelerated Stress Testing (HAST) program that included 

temperature/humidity cycling, high flux (including UV) exposure and vibration stress testing was 

completed under this subcontract. HAST stress tests are critical in establishing module failure modes 

and degradation rates of both the overall module and at the component level. Component HAST tests 

included testing for mirror reliability and thermal path degradation. Module HAST testing included 

rigorous module environmental testing. The correlation of the HAST program with field data indicated

field failures, degradation rates, and ultimately, the lifetime of the module and its components. A linear 

extrapolation of power degradation from environmental stress test measured 8% degradation at 10 

years => 25 years life.
11

Reliability testing continues at SolFocus, and has become a part of the control loop in the manufacturing 

process. As is normal for reliability work, field and HAST learnings improve accuracy estimates of the 

lifetime of the equipment.

Subtask 4.1 - IEC Qualification

Passing IEC qualification is critical in achieving market penetration 

and acceptance in the United States and other countries. Prior to 

submitting the SF1100 product to PTL for IEC 62108 testing, 

SolFocus performed its own internal testing in the critical areas, 

and based on results of this internal testing, we were confident in 

the products’ ability to pass IEC certification. Due to complications 

recognized by the testing lab, the final certification for the SF1100 

was delayed, but is expected by the end of July 2009 once outdoor 

exposure tests are complete. Further complications are not 

anticipated, nor is non-passage, as internal qualification tests in all 

sequences indicate a successful passage. Furthermore, the 

previous generation of module (SF1000) was awarded IEC 

certification, making it the first CPV panel on the market to receive 

IEC certification.

Subtask 4.2 - Highly Accelerated Stress Test (HAST) & Subtask 4.3 - Correlation of HALT with 

Field Test Results using Analytical Model

The objective of this task was to implement an extensive HAST program; including temperature/

humidity cycling, high flux (including UV) exposure and vibration stress testing. These stress tests are 

critical in establishing module failure modes and degradation rates of the overall module as well as at 

the component level. Component HAST tests included testing for mirror reliability and thermal path 

degradation; module HAST testing included rigorous module environmental testing to assure a 25-year 

life of the module and components. A complete report outlining each of the component HAST tests was 

delivered to NREL in November 2008. 

The correlation of the HAST program with field data indicated field failures, degradation rates, and 

ultimately, lifetime of the module and components. We collected field data related to HAST tests in 

Arizona, which gave us an indication of degradation, output, reliability, and failure modes. It is 

important to note that the SolFocus field data was collected in a geography with very high annualized 

DNI (7-7.3); an environment which is typical of areas well-suited for CPV and that stress the robustness 

Copy of IEC 62108 certificate for the SF1000 

product, dated June 2009.
12

of the product. In summary, a linear extrapolation of power degradation from environmental stress 

tests measured 8% degradation at 10 years on a panel with a 25 year life, thus beating targeted 

objectives under this subcontract.

Task 5 – Manufacturing Readiness

Overview

The objective of this task was to have a seamless transition from pilot-run manufacturing to high-volume 

manufacturing. This task included subtasks for assuring that all parts of the supply chain were in place 

and able to meet manufacturing demand, as well as assure that all equipment, facilities, and processes

were placed to allow rapid ramp from pilot run to volume production. 

This past year, SolFocus has been heavily focused on manufacturing readiness. SolFocus underwent 

negotiations with our supply chain partners for module components, resulting in secured material 

supply business contracts. We are confident that our supply chain partners have alleviated bottlenecks 

and will have the resources available for panel manufacturing at volume and cost targets indicated for 

2009-2010. Furthermore, a quality control program for suppliers was developed and is in place for both 

the Glassworks facility and for component supplier partners at their facilities. 

Additional steps were taken to assure high volume manufacturing and quality control, which included 

actively engaging with III-V PV cell manufacturers in order to assure quality and supply of cells to meet 

CPV module design requirements for functionality and developing the necessary alignment tooling for 

an automated assembly line. 

Module lifetime power prediction as of June 2009.
13

As mentioned earlier in this report, the SolFocus Glassworks facility in Arizona expanded and is fully 

operational, with an expected production this year of 15MW of primary reflectors and more than 

doubling that quantity in 2010. The Glassworks facility has the capabilities to produce a small volume 

(5MW) of SF1100 panels via its semi-automated prototype line, but could be quickly expanded given US 

demand increases. 

Meikle Automation was contracted for the development of automation for the manufacturing process 

to enable SolFocus to expand capacity to 100MW by mid-2010. The pilot automation line for volume 

panel assembly was implemented at Meikle’s Rochester, New York facility. The pilot run of this line

tripled our SF1100 panel population in one week’s time. This automated assembly line is being 

replicated by our manufacturing partners, and is projected to have a 50MW production capacity by year 

end 2009 and a 100MW capacity in mid 2010.

Subtask 5.1 - Supply Chain

In the second half of 2008, SolFocus was heavily focused on manufacturing readiness. SolFocus’ 

manufacturing and supply chain plan of record was set by December 2008 and was moved into the 

execution phase by January 2009. Our supply chain partners underwent materials negotiations for 

module components and material supply business contracts were awarded by year-end 2008. A quality 

control program for suppliers has been developed and is in place for both the Glassworks facility and for 

component supplier partners at their facilities. As well, SolFocus Glassworks facility initiated an internal 

program schedule for ISO certification. 

A cost throughput analysis was reported to NREL in November 2008 and was based on negotiated 

materials contracts, which showed SolFocus beating its aggressive cost targets for the SF1100 panels. 

Navigant consulting provided a third party validation of the throughput analysis and reported that 

SolFocus BOM costs were under $5/Watt, the target for this subcontract. 

Subtask 5.2 - Factory/Assembly

As mentioned above, the SolFocus Glassworks facility in Arizona expanded in March 2009 and was fully 

operational by April. This manufacturing expansion is expected to produce 15MW of primary reflectors 

in 2009 and more than doubling capacity in 2010. The Glassworks facility will also have the capabilities 

to produce a small volume of SF-1100 panels via its prototype line. 

The pilot automation line for volume panel assembly was developed and tested in New York with 

SolFocus’ automation manufacturing partner, Miekle. This pilot line had >3MW capacity and more than 
14

tripled the SF1100 panel population in one week of operation during the test run in April, proving that 

SolFocus is on a path to high volume manufacturing. 

By the end of 2008, SolFocus and its manufacturing partners had produced approximately 1MW of 

SF1000 product to meet supply contracts and engineering R&D testing needs. By the end of 2009, 

SolFocus and its manufacturing partners are projected to build 15MW of SF1100 panels and have a 

50MW manufacturing capacity which can be quickly scaled up to 100MW or beyond to meet demand. 

An additional benefit of the automated assembly was the increase in assembly precision, which is 

leading to an increase in panel acceptance angle and consequently, lower installation costs. 

Meikle high volume automated assembly line. Top left: secondary mirrors on sheet glass. Top right: Primary mirror attachment to front glass. Bottom 

left: Adhesive application to primary mirrors. Bottom right: Kuka robots moving panels to next step of process.
15

Summary

SolFocus has executed according to plan and has met or exceeded the targets laid out in the original 

statement of work set 18 months ago. This subcontract was instrumental in the commercialization of 

the SolFocus concentrator photovoltaic module and helped put it on an aggressive cost reduction curve 

resulting in LCOE numbers that beat SAI goals, as well as having the fastest cost reduction curve 

compared to other PV technologies.

In summary, the key metrics of the program have been achieved:

Panel efficiency of 25+% (22% was program goal)

Module cost of <$5/Watt (target exceeded)

On path to meet SAI cost targets

>3MW manufacturing/production capacity
F1146-E(10/2008) 

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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.

1. REPORT DATE (DD-MM-YYYY)

December 2009

2. REPORT TYPE

Subcontractor Report

3. DATES COVERED (From - To)

11/15/07-06/30/09

4. TITLE AND SUBTITLE

Reflective Optics CPV Panels Enabling Large Scale, Reliable 

Generation of Solar Energy Cost Competitive with Fossil Fuels: 

15 November 2007 – 30 June 2009

5a. CONTRACT NUMBER

DE-AC36-08-GO28308

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

S. Horne, M. McDonald, N. Hartsoch, and K. Desy

5d. PROJECT NUMBER

NREL/SR-520-47310

5e. TASK NUMBER

PVB91199

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

SolFocus, Inc.

510 Logue Avenue

Mountain View, CA 94043

8. PERFORMING ORGANIZATION

REPORT NUMBER

NAT-7-77015-09

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401-3393

10. SPONSOR/MONITOR'S ACRONYM(S)

NREL

11. SPONSORING/MONITORING 

AGENCY REPORT NUMBER

NREL/SR-520-47310

12. DISTRIBUTION AVAILABILITY STATEMENT

National Technical Information Service

U.S. Department of Commerce

5285 Port Royal Road

Springfield, VA 22161

13. SUPPLEMENTARY NOTES

NREL Technical Monitor: Brian Keyes

14. ABSTRACT (Maximum 200 Words)

The goal of SolFocus' 18-month subcontract was to improve reflective optics concentrator photovoltaic (CPV) panels: 

(1) to enable the large-scale, reliable production of solar electricity to meet Solar America Initiative-established 

levelized cost fo energy targets, and (2) to ultimately provide a path to solar power at parity with or better than the 

cost of energy generated using fossil fuels. To this end, SolFocus completed this subcontract with great success, as 

evidenced by the end results of a CPV panel with conversion efficiencies greater than the targeted 22% and 

manufacturing capabilities with a run-rate capacity far exceeding the milestone benchmark of more than 3 

megawatts.

15. SUBJECT TERMS

PV; CPV; concentrator photovoltaics; reflective optics; large-scale; generation; solar cells; cost; conversion 

efficiencies; manufacturing; fossil fuel; LCOE 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION 

OF ABSTRACT

UL

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OF PAGES

19a. NAME OF RESPONSIBLE PERSON

a. REPORT

Unclassified

b. ABSTRACT

Unclassified

c. THIS PAGE

Unclassified 19b. TELEPHONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98)

Prescribed by ANSI Std. Z39.18