May 2005 NREL/BK-520-38024 

International Conference on 

Solar Concentrators for the Generation of 

Electricity or Hydrogen 

Book of Abstracts 

Conference Chairs: 

 R. McConnell, M. Symko-Davies, and H. Hayden 

Double Tree Paradise Valley 

Scottsdale, Arizona 

May 1 – 5, 2005 
NOTICE

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iii

Program Committee Members 

Chairs: 

R. McConnell, National Renewable Energy Laboratory, USA 

M. Symko-Davies, National Renewable Energy Laboratory, USA 

H. Hayden, Arizona Public Service, USA 

Conference Organizing Committee: 

D. Glickson, National Renewable Energy Laboratory, USA 

S. Huntley, National Renewable Energy Laboratory, USA 

S. Norman, Arizona Public Service, USA 

S. Padilla, National Renewable Energy Laboratory, USA 

F. Posey-Eddy, National Renewable Energy Laboratory, USA 

S. Renfrow, National Renewable Energy Laboratory, USA 

Program Committee: 

V. Andreev, Ioffe Institute, Russia 

K. Araki, Daido Steel, Japan 

R. Bentley, Whitfield Solar, United Kingdom 

A. Bett, Fraunhofer ISE, Germany 

R. Boehm, University of Nevada, Las Vegas, U.S.A. 

T. Bruton, NaREC, United Kingdom 

V. Garboushian, Amonix, USA 

D. Holland, Solar Systems P/L, Australia 

J. Karni, Weizmann Institute, Israel 

S. Kurtz, National Renewable Energy Laboratory, USA 

S. Licht, University of Massachusetts, Boston, USA 

I. Luque Heredia, Inspira, Spain 

A.Luzzi, Switzerland 

H. Dieter Mohring, Center for Solar Energy & Hydrogen Research, Germany 

G. Sala, Universidad Politecnica de Madrid, Spain 

A. Sarno, ENEA, Italy 

R. Sherif, Spectrolab, USA 

A.Steinfeld, ETH, Switzerland 

R. Swanson, SunPower, USA 

R. Winston, University of California, Merced, USA 
iv

Sponsors 

The International Conference on Solar Concentrators for the Generation of Electricity or 

Hydrogen deeply appreciates the support of the sponsors of this conference – 

Arizona Public Service (APS), Solar Systems PTY, Spectrolab, Amonix, 

Solargenix Energy, Solar Electric Power Association (SEPA), Arizona 

Department of Commerce Energy Office, and Navigant Consulting. 

The support of these sponsors has made this conference possible. 

Thank you!
v

Program Agenda 

(All persons listed below are listed as the presenting author.) 

Sunday, 1 May 2005 

1800 – 2000 Registration and Reception - Sponsored by Solar Systems, PTY 

Presentations downloaded from CD ROMS or memory stick 

Monday, 2 May 2005 

0800 Registration and Continental Breakfast – Breakfast Sponsored by Solargenix 

0830 – 0850 Welcome - (Arizona or NREL dignitaries) 

 

0850 – 0900 Robert McConnell, Plenary Session Opening Remarks, National Renewable Energy 

Laboratory, Golden, Colorado, USA 

0900 - 1500 Policy and Marketing for Solar Concentrator Technologies 

0900 – 1000 Southwest Regional Policy Presentations 

 Moderator: Ray Williamson, Utilities Engineer, Arizona Corporation Commission, 

Arizona, USA 

 

 • Richard Burdette, Energy Advisor, Office of the Governor, Nevada, USA 

 • Lynnette Evans, Policy Advisor, Regulatory Affairs, Office of the Governor, 

 Arizona, USA 

 • Gary Schmitz, Principal Economist, Colorado Public Utility Commission, 

 Office of the Governor, Colorado, USA 

 • Ned Farquhar, Energy/Environment Advisor, Office of the Governor, 

 New Mexico, USA 

 • TBD: Speaker representing California 

 

1000 – 1030 Coffee Break – Sponsored by Solargenix

(You may begin setting up your poster at 11:00 a.m. on Monday morning.)

 

1030 – 1130 Roundtable and Audience Discussion with Southwest Regional Policy Panel 

Moderator: Ray Williamson, Utilities Engineer, Arizona Corporation Commission, 

Arizona, USA 
vi

1130 – 1330 Conference Luncheon – Sponsored by Amonix

 

 Vahan Garboushian, “Marketing Concentrating Solar Systems – Challenges and 

Opportunities,” Amonix, Inc., Torrance, California, USA 

 

1330 – 1715 Market Entry for Solar Concentrator Systems 

1330 – 1400 David Holland, “Picking Up the Pace,” Solar Systems Pty. Ltd., Hawthorne, Australia

 

1400 – 1430 Raed A. Sherif, “Commercialization of Concentrator Multijunction Photovoltaics,” 

Spectrolab, Inc., Sylmar, California, USA 

 

1430 – 1500 Peter Johnston, “The Role of CSP in Filling APS’ Future Solar Energy Needs,” 

Arizona Public Service, Tempe, Arizona, USA 

 

1500 – 1515 Coffee Break – Sponsored by Solargenix

1500 – 1655 Related Marketing Issues for Solar Concentrators 

1515 – 1535 Vicente Díaz, “The Path for Industrial Scale Production of Very High Concentration 

PV Systems,” ISOFOTON, SA, Málaga, Spain 

 

1535 – 1555 Hans-Joerg Lerchenmüller, “Cost and Market Perspectives for FLATCON®

Systems,” Concentrix Solar, Freiburg, Germany 

 

1555 – 1615 Kenji Araki, “CPV Using 3J III-V Cells and Fresnel Lenses – Reliability, 

Applications and Perspectives,” Daido Steel Co., Nagoya, Japan 

 

1615 – 1635 David Faiman, “The Triple Sustainability of CPV Within the Framework of the Raviv 

Financing Model,” Ben-Gurion University, Sede Boqer, Israel 

 

1635 – 1655 Gilbert Cohen, “SolarGenix Concentrating Solar Thermal,” SolarGenix, LLC, 

Raleigh, NC, USA 

 

1800 – 2000 Poster Session and Reception - Sponsored by Spectrolab

(See Poster List Below) 

Tuesday, 3 May 2005 

0830 – 1200 Solar Cells for Concentrators 

0830 – 0850 Speaker: Robert McConnell, “DOE High Performance Concentrator PV Project,” 

National Renewable Energy Laboratory, USA 

0850 – 0910 Mark Wanlass, “GaInP/GaAs/GaInAs Monolithic Tandem Cells for HighPerformance Solar Concentrators,” National Renewable Energy Laboratory, Golden, 

Colorado, USA

 

0910 – 0930 Harry Atwater, “Ultrahigh Efficiency Cells for Microconcentrator PV”, Caltech, 

Pasadena, California, USA 

 

0930 - 0950 Carlo Flores, “GaAs Concentrator Solar Cells for the Italian Electrical System,” CESI 
vii

S.p.A., Milano, Italy 

 

0950 – 1010 Richard King, “Bandgap Engineering in High-Efficiency Multijunction Concentrator 

Cells,” Spectrolab, Inc., Sylmar, California, USA 

 

1010 – 1030 Coffee Break – Sponsored by Xcel Energy

 

1030 – 1050 Jeffrey Gordon, “Ultra-High Concentration Effects in Multi-Junction Solar Cells,” 

Ben-Gurion University of the Negev, Israel, and University of California, Merced, 

California, USA 

 

1050 – 1110 Daniel J. Friedman, “GaInNAs Junctions for Next-Generation Concentrators: 

Progress and Prospects,” National Renewable Energy Laboratory, Golden, Colorado, 

USA 

 

1110 – 1130 Timothy Bruton, “Low Cost Concentrator Cells From One Sun Production Cell 

Technology,” NaREC, AG, United Kingdom 

 

1130 – 1150 Lew Fraas, “Efficient Solar Photovoltaic Mirror Modules for Half the Cost of 

Today’s Planar Modules,” JX Crystals Inc., Issaquah, Washington, USA 

 

1150 – 1330 Lunch (no speaker) 

1330 – 1655 Prototypes and Optics for Low to High Concentration Technologies 

1330 – 1350 Valery Rumyantsev, “Practical Design of PV Modules and Trackers for Very High 

Solar Concentration,” Ioffe Physico-Technical Institute, St. Petersburg, Russia 

 

1350 – 1410 Lew Fraas, “New Cassegrainian PV Module Using Dichroic Secondary and 

Multijunction Solar Cells,” JX Crystals Inc., Issaquah, Washington, USA 

 

1410 – 1430 Dan Aiken, “Design, Manufacturing, and Testing of a Prototype Multijunction 

Concentrator Module,” Emcore Photovoltaics, Albuquerque, New Mexico, USA

 

1430 – 1450 Andreas Bett, “The FLATCON® Concentrator PV-Technology,” Fraunhofer Institute 

for Solar Energy Systems ISE, Freiburg, Germany 

 

1450 – 1510 CoffeeBreak – Sponsored by Excel Energy

 

1510 – 1530 Roland Winston, “Planar Concentrators at the Etendue Limit,” University of 

California, Merced, California, USA 

 

1530 – 1550 Ralf Leutz, “Hemispherical Solar Concentrator Corrected for Aberrations,” PhilippsUniversity, Marburg, Germany

 

1550 – 1610 Daniel Feuermann, “Realization of Compact, Passively Cooled, High-Flux 

Commercial Photovoltaic Prototypes,” Ben-Gurion University of the Negev, Be'er 

Sheva, Israel 

 

1610 – 1630 Ralf Leutz, “One-Axis PV Sun Concentrator Based on Linear Nonimaging Fresnel 

Lens,” Philipps-University, Marburg, Germany 

 

1630 – 1650 Atushi Akisawa, “Design of Non-Imaging Fresnel Lens for 500X Solar 
viii

Concentration,” Tokyo University of Agriculture and Technology, Toyko, Japan 

 

1730 – 2030 Conference Dinner – SPONSORED BY ARIZONA PUBLIC SERVICE, 

 Overall Event Sponsor. 

Speaker: Richard J. Schwartz, “The Evolution of High Intensity Photovoltaic Cells 

from Thermophotovoltaic Applications to High Concentration Solar Applications: 

Lessons Learned,” Purdue University, West Lafayette, Indiana, USA 

Wednesday, 4 May 2005 

0830 – 1200 Solar Concentrator Designs and Testing 

8:30 – 0850 Ignacio Antón,” Indoor Characterization of Concentrator Modules: Application on 

the Production Line,” Instituto de Energía Solar, Universidad Politécnica de Madrid, 

Spain 

 

0850 – 0910 Steve Kusek, “On-Sun Testing of Multijunction PV Cells,” Concentrating 

Technologies,” LLC, Owens Cross Roads, Alabama, USA 

 

0910 – 0930 Ignacio Luque-Heredia, “CPV Sun Tracking at InSpira,” InSpira, SL, Madrid, Spain 

0930 – 0950 William McMahon, “Outdoor Testing of GaInP2/GaAs Tandem Cells with Top Cell 

Thickness Varied,” National Renewable Energy Laboratory, Golden, Colorado, USA 

 

0950 – 1010 Yen-Chang Tzeng, “The Development of High Concentrating III-V Photovoltaic 

Modules at INER Taiwan,” INER, Taiwan

 

1010 – 1030 Coffee Break – Sponsored by Navigant Consulting

 

1030 – 1050 Giuliano Martinelli, “Dichroic Flat Faceted Concentrator for PV Use,” University of 

Ferrara & INFM, Ferrara (FE), Italy 

 

1050 – 1110 Yiping Wang, “Performance on Concentrating Photovoltaic/Thermal Systems Using 

Solar Cells Immersed in Dielectric Liquid,” Tianjin University, Tianjin, China 

1110 – 1130 Liang Ji, “Representative Samples for Concentrator Photovoltaic Module 

Qualification Testing,” Arizona State University East, Mesa, Arizona, USA 

 

1130 – 1150 Geoff S. Kinsey, “Optimization of High-Concentration Multijunction Solar Cells,” 

Spectrolab, Sylmar, California, USA 

 

1150 – 1330 Lunch (no speaker) 

1330 – 1650 Hydrogen, Space and Innovative Concentrators 

1330 – 1350 Mark J. O’Neill, “ENTECH’s Stretched Lens Array (SLA) for NASA’s Moon/Mars 

Exploration Missions, Including Near-Term Terrestrial Spin-Offs,” ENTECH, Inc., 

Keller, Texas, USA 

 

1350 – 1410 D. Buie, “Combining the Tools for Solar Thermal and Photovoltaic Power Generation 

– The Experimental and Computational Facilities at the University of Sydney,” 

University of Sydney, Sydney, Australia 
ix

1410 – 1430 Gregor Lengeling, “The agiceiverTM – A New Approach for Hydrogen Production by 

Concentrated Sun Light,” AGRISOLAR, Aachen, Germany 

 

1430 – 1450 Sergey Vasylyev, “Nonimaging Reflective Lens Concentrator,” SVV Technology 

Innovations, Inc., Sacramento, California, USA 

 

1450 - 1510 Coffee Break – Sponsored by Navigant Consulting

 

1510 – 1530 Yoshihiro Nakato, “Recent Progress of Electrochemical Solar Water Splitting with 

Photoelectrodes and Photocatalysts,” Osaka University, Osaka, Japan

 

1530 – 1550 Jamal R.Thompson, “Hydrogen Electrolysis Using Concentrated Solar Energy,” 

Howard University, Washington, D.C., USA 

 

1550 – 1610 Robert McConnell, “Summary of Conference Highlights,” National Renewable 

Energy Laboratory, Golden, Colorado, USA 

 

1610 – 1630 Herb Hayden, “Recommendations for Further Action,” Arizona Public Service, 

Phoenix, Arizona, USA 

 

1630 – 1650 Instructions for tomorrow’s field trip 

Thursday, 5 May 2005 

0830 – 1500 Site Visits 

 

0830 – 0845 Board Buses 

 

0830 – 1500 Site Visits: 

 Arizona Public Service (APS) 

 • APS Star, Tempe 

 • APS Facility, Prescott 

Posters 

1 H. Song, “One Step Method to Produce Hydrogen by Tandem Amorphous Silicon Solar Cells,” 

Nankai University, Tianjin, China 

 

2 C. S. Solanki, “Solar Irradiation Potential for PV Concentrator Systems in India,” IIT Bombay, 

Munbai, India 

 

3 C. S. Solanki, “PV Concentrator Systems – A Database Search,” IIT Bombay, Munbai, India 

 

4 Carlo Privato, “Plastics Structured Optics for Solar Concentrating in PV System,” ENEA Centro 

Ricerche, Portici (NA), Italy 

 

5 Angelo Sarno, “Design, Realization and Preliminary Performance Analysis of the PhoCUS-5 

Standard Unit,” ENEA Research Center, Portici, Napoli, Italy 

 

6 Huacong Yu, “Research on Graded Optical Band Gap (GBG) in na-Si:H Solar Cells Prepared by 

PECVD,” Shanghai Jiaotong University, Shanghai, China 
x

7 Kemal Koknar, “Increased Solar Collector Efficiency Through SunTrapTM Technology,” Radiant 

Power, LLC, Santa Clara, California, USA 

 

8 Manuel J. Blanco, “Design Principles of Tonatiuh, an Open Source Computer Program for the 

Design and Analysis of Solar Concentrating Systems,” The University of Texas at Brownsville, 

Brownsville, Texas, USA 
xi

TABLE OF CONTENTS 

Title/Author(s): Page 

Marketing Concentrating Solar Systems – Challenges and Opportunities . . . . . . . . . . . . . . . 

Vahan Garboushian, Amonix, Inc. 

1 

Picking Up the Pace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

David Holland, Solar Systems Pty., Ltd. 

2 

Commercialization of Concentrator Multijunction Photovoltaics . . . . . . . . . . . . . . . . . . 

Raed A. Sherif, Richard R. King, Chris M. Fetzer, Hector L. Cotal, Geoff S. Kinsey, Jeff Peacock, and 

Nasser H. Karam, Spectrolab, Inc. 

3 

The Role of CSP in Filing APS’ Future Solar Energy Needs . . . . . . . . . . . . . . . . . . . . . . 

Peter Johnston, Arizona Public Service 

4 

The Path for Industrial Scale Production of Very High Concentration PV Systems . . . . . . . . . . 

V. Díaz, ISOFOTON SA 

5 

Cost and Market Perspectives for FLATCON® - Systems . . . . . . . . . . . . . . . . . . . . . . . . 

H. Lerchenmüller, Concentrix Solar

A. W. Bett, and J. Jaus, Fraunhofer Institute for Solar Energy Systems ISE

6 

CPV Using 3J III-V Cells and Fresnel Lenses – Reliability, Applications and Perspectives . . . . . 

Kenji Araki, Daido Steel Co., Ltd. 

7 

The Triple Sustainability of CPV Within the Framework of the Raviv Financing Model . . . . . . . 

David Faiman, Ben-Gurion University 

Dov Raviv and Roy Rosenstreich, MST, Ltd. 

8 

SolarGenix Concentrating Solar Thermal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Gilbert Cohen, SolarGenix, LLC. 

9 

DOE High Efficiency Concentrator PV Project: III-V Multijunction Concentrators . . . . . . . . . 

Robert McConnell and Martha Symko-Davies, National Renewable Energy Laboratory

10 
xii

GaInP/GaAs/GaInAs Monolithic Tandem Cells for High-Performance Solar Concentrators . . . . 

M.W. Wanlass, S. P. Ahrenkiel, D. S. Albin, J. J. Carapella, A. Duda, J. F. Geisz, Sarah Kurtz, 

T. Moriarty, and M. J. Romero, National Renewable Energy Laboratory 

11 

Ultrahigh Efficiency Cells for Microconcentrator PV . . . . . . . . . . . . . . . . . . . . . . . . . . 

Harry Atwater, California Institute of Technology 

12 

GaAs Concentrator Solar Cells for the Italian Electrical System . . . . . . . . . . . . . . . . . . . . 

Carlo Flores, CESI S.p.A. 

13 

Bandgap Engineering in High-Efficiency Multijunction Concentrator Cells . . . . . . . . . . . . . 

R. R. King, R. A. Sherif, G. S. Kinsey, C. M. Fetzer, K. M. Edmondson, D. C. Law, H. L. Cotal, 

D. D. Krut, J. H. Ermer, and N. H. Karam, Spectrolab, Inc. 

14 

Ultra-High Concentration Effects in Multi-junction Solar Cells . . . . . . . . . . . . . . . . . . . . 

J. M. Gordon, Ben-Gurion University of the Negev and the University of California, Merced 

E. A. Katz, W. Tassew, and D. Feuermann, Ben-Gurion University of the Negev 

15 

GaInNAs Junctions for Next-Generation Concentrators: Progress and Prospects . . . . . . . . . . 

D. J. Friedman, A. J. Ptak, S. R. Kurtz, J. F. Geisz, and J. Kiehl, National Renewable Energy 

Laboratory 

16 

Low Cost Concentrator Cells From One Sun Production Cell Technology . . . . . . . . . . . . . . 

T M Bruton, NaREC 

17 

Efficient Solar Photovoltaic Mirror Modules for Half the Cost of Today’s Planar Modules . . . . . 

L. Fraas, J. Avery, and H. Huang, JX Crystals, Inc. 

18 

Practical Design of PV Modules and Trackers for Very High Solar Concentration . . . . . . . . . 

V. D. Rumyantsev, Ioffe Physico-Technical Institute, Russian Academy of Sciences 

19 

New Cassegrainian PV Module Using Dichroic Secondary and Multijunction Solar Cells. . . . . . 

L. Fraas, J. Avery, and H. Huang, JX Crystals, Inc. 

E. Shifman, SRS Engineering & Agencies, Ltd.

20 

Design, Manufacturing, and Testing of a Prototype Multijunction Concentrator Module . . . . . . 

D. J. Aiken, M. A. Stan, S. Endicter, G. Girard, P. R. Sharps, and E. Fuller, Emcore Photovoltaics 

21 

The FLATCON® Concentrator PV-Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

A.W. Bett, C. Baur, H. Lerchenmüller, G. Siefer, and F. Dimroth, Fraunhofer Institute for Solar 

Energy Systems ISE 

22 

Planar Concentrators at the Etendue Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Roland Winston, University of California, Merced 

Jeffrey M. Gordon, University of California, Merced, and Ben-Gurion University of the Negev 

23 

Hemispherical Solar Concentrator Corrected for Aberrations 

Ralf Leutz, Philipps-University

24 
xiii

Realization of Compact, Passively Cooled, High-Flux Commercial Photovoltaic Prototypes . . . . . 

Daniel Feuermann, Ben-Gurion University of the Negev 

Jeffrey M. Gordon, Ben-Gurion University of the Negev, H2Go Corp., and University of California, 

Merced 

Steve Horne and Gary Conley, H2

Go Corp. 

Roland Winston, University of California, Merced

 

25 

One-Axis PV Sun Concentrator Based on Linear Nonimaging Fresnel Lens . . . . . . . . . . . . . 

Ralf Leutz, Philipps-University 

Leonid B. Rubin, Alexander S. Osipov, Vasili Y. Tarasenko, and Valerie M. Nebusov, Day4 Energy, 

Inc. 

26 

Design of Non-Imaging Fresnel Lens for 500X Solar Concentration . . . . . . . . . . . . . . . . . 

Atushi Akisawa, Tokyo University of Agriculture and Technology 

27 

The Evolution of High Intensity Photovoltaic Cells from Thermophotovoltaic Applications 

to High Concentration Solar Applications: Lessons Learned . . . . . . . . . . . . . . . . . . . . . 

Richard J. Schwartz, Birck Nanotechnology Center, Purdue University 

28 

Indoor Characterization of Concentrator Modules: Application on the Production Line . . . . . . . 

I. Antón, C. Domínquez, and G. Sala, Instituto de Energía Solar 

29 

On-Sun Testing of Multijunction PV Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Steve Kusek, Concentrating Technologies, LLC 

30 

CPV Sun Tracking at InSpira . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

I. Luque-Heredia, Inspira, SL 

 

31 

Outdoor Testing of GaInP2/GaAs Tandem Cells with Top Cell Thickness Varied . . . . . . . . . . . 

W. E. McMahon, K. E. Emery, D. J. Friedman, L. Ottoson, M. S. Young, J.S. Ward, 

C. M. Kramer, A. Duda, and Sarah Kurtz, National Renewable Energy Laboratory 

32 

The Development of High Concentrating III-V Photovoltaic Modules at INER Taiwan . . . . . . . 

Yen-Chang Tzeng, Chih-Hung Wu, Hwa-Yuh Shin, Hwen-Fen Hong and 

Chieh Cheng, INER 

33 

Dichroic flat faceted Concentrator for PV Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Giuliano Martinelli, Marco Stefancich, Andrea Antonini, Alessandro Ronzoni, 

Maurizio Armani, and Paolo Zurru, University of Ferrara & INFM 

34 

Performance on Concentrating Photovoltaic/Thermal Systems Using Solar Cells Immersed in 

Dielectric Liquid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Yiping Wang, Wei Tian, Jianbo Ren, and Li Zhu, Tianjin University 

35 

Representative Samples for Concentrator Photovoltaic Module Qualification Testing . . . . . . . . 

Robert McConnell, National Renewable Energy Laboratory 

Liang Ji and Govindasamy Tamizhmani, Photovoltaic Testing Laboratory, Arizona State University 

East 

36 

Optimization of High-Concentration Multijunction Solar Cells . . . . . . . . . . . . . . . . . . . . 

Geoff S. Kinsey, Moran Haddad, Hojun Yoon, Ken Edmondson, Chris M. Fetzer, Richard R. King, 

and Raed A. Sherif, Spectrolab, Inc. 

37 
xiv

ENTECH’s Stretched Lens Array (SLA) for NASA’s Moon/Mars Exploration Missions, 

Including Near-Term Terrestrial Spin-Offs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Mark J. O’Neill, ENTECH, Inc. 

38 

Combining the Tools for Solar Thermal and Photovoltaic Power Generation – 

The Experimental and Computational Facilities at the University of Sydney . . . . . . . . . . . . . 

D. Buie, M. Borland, S. G. Bosi, C. J. Dey, N. J. Ekins-Daukes, A. G. Imenes, D. Mc

Kenzie, 

M. Proschek, A. Royne, and Y. Yin, University of Sydney 

39 

The agiceiverTM – a New Approach for Hydrogen Production by Concentrated Sunlight . . . . . . 

Gregor Lengeling, AGRISOLAR 

40 

Nonimaging Reflective Lens Concentrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Sergey Vasylyev, SVV Technology Innovations, Inc. 

41 

Recent Progress of Electrochemical Solar Water Splitting with Photoelectrodes and 

Photocatalysts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Yoshihiro Nakato, Osaka University 

 

42 

Hydrogen Electrolysis Using Concentrated Solar Energy . . . . . . . . . . . . . . . . . . . . . . . . 

Robert D. McConnell, National Renewable Energy Laboratory 

John B. Lasich, Solar Systems 

Jamal R. Thompson, and Mohsen Mosleh, Howard University 

43 

 Poster Papers 

Title/Author(s) 

One Step Method to Produce Hydrogen by Tandem Amorphous Silicon Solar Cells . . . . . . . . . 

H. Song, X. H. Geng, Y. Zhao, X. D. Zhang, and D. K. Zhang, Nankai University 

44 

Solar Irradiation Potential for PV Concentrator Systems in India . . . . . . . . . . . . . . . . . . . 

C. S. Solanki, VIT, Pune and P. Pimpalkar, ITT Bombay 

46 

PV Concentrator Systems – A Database Search . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C.S. Solanki, VIT, Pune and P. Pimpalkar, ITT Bombay 

47 

Plastics Structured Optics for Solar Concentrating in PV System . . . . . . . . . . . . . . . . . . . 

Carlo Privato, Carmine Cancro, Michele Pellegrino and A. Sarno, ENEA Centro Ricerche 

48 

Design, Realization and Preliminary Performance Analysis of the PhoCUS-5 Standard Unit . . . . 

A. Sarno and C. Privato, Enea Portici Research Center 

49 

Research on Graded Optical Band Gap (GBG) in na-Si:H Solar Cells Prepared by PECVD . . . . 

Huancong Yu and Rongqiang Cui, Shanghai Jiaotong University 

He Wang and Hong Yang, Xi’an Jiaotong University 

Zhibin Zhou, Jiangming Gu, Liang Zhao, Dunyi Tang, Shuquan Lin, and Fanying Meng, Shanghai 

Jiaotong University 

Yuliang He, Jiangsu Weifu Nanometers Science & Technology Ltd. 

50 
xv

Increased Solar Collector Efficiency Through SunTrapTM Technology . . . . . . . . . . . . . . . . 

Kemal Koknar and Eric Aylaian, Radiant Power, LLC 

51 

Design Principles of Tonatiuh, an Open Source Computer Program for the Design and 

Analysis of Solar Concentrating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Manuel J. Blanco, Juana M. Amieva, Azael Mancillas, University of Texas, Brownsville 

52 
1

Marketing Concentrating Solar Systems -

Challenges and Opportunities

Vahan Garboushian – Amonix, Inc.

3425 Fujita Street, Torrance, CA 90505

310-325-8091 - vahan@amonix.com

The implementation of today’s Concentrating Solar Systems offer customers increased 

performance at the lowest cost in photovoltaic energy generation. Tomorrow’s advanced 

systems offer still more. The challenge is to educate customers on the proper utilization of these 

systems and avoid the pitfalls of ‘overselling’ in a highly competitive market. Standard flat-plate 

technology is internationally well established and has opened the door for superior concentrating 

systems. Specialized marketing strategies are needed. Accurate knowledge at the customer level 

is required to advance Concentrating Solar market entry. This paper will present lessons learned 

from over 10 years of utility field trials and offer suggestions for the Concentrating Solar 

community in the area of national and international marketing. 
2

Picking Up The Pace 

Dave Holland 

Solar Systems Pty., Ltd., Hawthorne, Australia 

Email: dholland@solarsystems.com.au

Abstract: 

Solar energy is more plentiful, more predictable and is less site specific than wind. Despite 

solar’s advantages and our best intentions, wind farms are commonplace while “sun farms” are 

still a rarity. It seems inevitable that the scales will tip but the natural time scales are too long 

(for the author at least). How do we pick up the pace. 

This paper presents the author’s view of the solution, which includes a mixture of technology, 

commercial management, capital, collaboration and influence (not to mention a good dose of 

courage, excellence and perseverance). 

Dave Holland is the Managing Director of Solar Systems and a Director of Renewable Energy 

Generators Australia – an industry group that represents more than 90% of Australia’s renewable 

energy based generation assets. 
3

Commercialization of Concentrator Multijunction Photovoltaics 

Raed A. Sherif, Richard R. King, Chris M. Fetzer, Hector L. Cotal, Geoff S. Kinsey, Jeff 

Peacock, and Nasser H. Karam

Spectrolab, Inc., 12500 Gladstone Avenue, Sylmar, CA 91342-5373 

Email: rsherif@spectrolab.com

Abstract: 

This paper discusses the issues and opportunities of Concentrator multijunction photovoltaics. It 

gives an overview of the status of the technology, the status of the multijunction solar cells and 

receivers, and the roadmap to achieving higher cell efficiencies. The economic benefits of using 

this technology to produce gigawatts of electricity, and the steps required to achieve that are also 

presented. 
4

The Role of CSP in Filling APS’s Future Solar Energy Needs 

Peter Johnston 

Arizona Public Service 

Tempe, Arizona 

Email: Peter.Johnston@aps.com

Abstract not available. 
5

The Path for Industrial Scale Production of Very High Concentration PV Systems 

V. Díaz 

ISOFOTON SA, La Gitanilla 26, P.I. Santa Cruz. Málaga 29006, Spain 

Generally speaking, a common target for building photovoltaic at much lower prices is present inside 

PV industry as a definitive take off of PV solar energy. Concentration of light over the solar cell, as a way 

for reducing semiconductor area, (the highest driving cost in a PV module) is one of these strategies. 

The very high concentration problem in photovoltaic is an old target reviewed extensively since late 

seventies [1]. However, now it is being issued thanks to the increased interest evidenced [2] by the 

potential price reductions of reliable installed systems. Even more, firsts tentative in the industrialization 

is currently in progress [3] based on III-V solar cells, TIR-R lenses and accurate two axis tracking 

systems. 

ISOFOTON S.A., the Spanish PV manufacturer company, is interested in the exploitation of this 

technology. It is actively involved in the industrialization of High Concentration PV at really competitive 

price (below 2,5 €/Wpk for installed systems) when mass production issues (10MW/year) are considered. 

This paper will describe the details concerning the industrialization path from lab scale to mass 

production. The main focus now is to reduce the time for going to the market. 

Brief explanation of the high concentration PV concept 

The optics is one of the key issues of every concentration systems. The one chosen for this application 

is suitable for a very compact solution, (figure 1 and 2) and has been described in detail elsewhere [4]. It 

is composed of a system of two lenses (TIR-R), manufactured in acrylic by injection molding, where the 

top one (TIR) works by means of Total Internal Reflection. The second and bottom one works only by 

refraction and cover completely the solar cell. This system makes that the light impinging over the surface 

of the solar cell will be increased 1000 times. 

Aspheric surfaces

flat surface TIR facets

Solar Cell

~ 20 mm

~ 45 mm

Aspheric surfaces

flat surface TIR facets

Solar Cell

~ 20 mm

~ 45 mm

Figure 1. Cross section of the TIR-R 

system 

Figure 2. Solid drawing 

of the TIR-R system. 

Figure 3. Three finished PV 

concentration modules 

installed in a two axis tracking 

system 

The size of the PV module under development is 1 m times 0,3 m and for the final installations a two axis 

tracking system like that of figure 3 is needed. This is due to the requirements of collecting only direct 

sunlight. Further details of the manufacturing procedures will be addressed for the time of the conference. 

References

[1]. E.L. Burgess, M.W. Edenburn, “One kilowatt subsystem using Fresnel Lens Concentrators” Proc. of the 

12th IEEE PVSC, 1976 

[2]. “Ultra compact high flux GaAs cell photovoltaic concentrator” HERCULES. JOR-CT97-0123 EC Joule 

Thermie III .program.1999 

[3]. V. Diaz, J.L. Alvarez, J. Alonso, A. Luque, C. Mateos “Towards a technology for mass production of 

very high concentrator flat panel”. Proc. of the 19th European PVSEC Paris. 2004. In press. 

[4]. J.L Alvarez, M. Hernández, P. Benitez, J. C. Miñano, "TIR-R Concentrator: a new compact high-gain 

SMS design", Nonimaging Optics: Maximum Efficiency Light Transfer VI, Proc., pp.32-42, (2001). 
6

 Cost and Market Perspectives for FLATCON-Systems

H. Lerchenmüller a, A.W. Bett b, J. Jaus b 

a

 Concentrix Solar 

Solar Info Center, 79072 Freiburg, Germany 

lerchenmueller@concentrix-solar.de 

b

 Fraunhofer Institute for Solar Energy Systems ISE 

Heidenhofstraße 2, 79110 Freiburg, Germany 

bett@ise.fraunhofer.de 

ABSTRACT 

 FLATCON® systems are high concentrating photovoltaic units using point focussing 

Fresnel lenses and multi-junction solar cells. FLATCON® concentrator modules equipped with 

dual-junction solar cells reached efficiencies of 22,7% under realistic operation conditions. A 

thorough analysis of production cost was carried out for a 20 MW production line. This paper 

shows the results of this cost analysis and the calculations of levelized electricity costs in 

comparison to conventional flat plate PV modules: For large systems at sites with high direct 

solar radiation the FLATCON® technology is expected to have a clear competitive advantage. In 

February 2005 the company Concentrix Solar GmbH was founded as a spin-off company of 

Fraunhofer ISE to manufacture concentrator systems based on the FLATCON® technology. 
7

CPV using 3J III-V cells and Fresnel lenses –Reliability, Applications and Perspectives 

Kenji Araki 

Daido Steel Co., Ltd. 

2-30, Daido-cho, Minami-ku, Nagoya, Japan 

ABSTRACT 

Almost one year has passed since 550 X CPV system 

using III-V 3J cells and dome-shaped Fresnel lenses was 

launced in the test site and began power generation. The 

550 X system is the improved product from the 400 X CPV 

system presented at the previous SCC2003. Reliability and 

field test result is presented. Applications and future 

perspectives are discussed. 

1. What’s new about a 550 X system? 

 The 550X lens has two improvements from the previ-ous 

design. First, the facet size was significantly enlarged after 

improvement of injection molding technique by keep-ing 

uniformity in polymer fluid in the overall area. The loss 

from rounded prism peak and valley was significantly reduced. Second, durability against freezing cycle was improved. The previous 400 X injection-molded Fresnel lens 

had a problem in degradation by fine cracks caused by 

freezing. The new 550X lens was improved by residual 

stress and proved a stable outdoor operation for a long 

time. 

The next improvement was durability against concentrated UV flux and water condensation around the solar 

cell. Since III-V solar cells are more reactive against environment than silicon solar cells, they need complete sealing from environment. However, the transparent sealing 

polymer on the solar cell is exposed by concentrated 

sunlight and may be damaged by UV. Even though the 

sealing polymer keeps transparency, the mechanical 

strength would be usually degraded and have a chance of 

breakage of sealing. 

2. Reliability and fail-safe 

 It was shown that the receiver survives 20 years of 

accumulated concentrated sunshine (desert area) by UV 

accelerated test. Various fail-safe tests were conducted 

including off-axis beam test. Due to advanced non-imaging 

optics, the temperature rise by off-axis beam was 15K. 

3. One year field test 

 One year observation showed a seasonal fluctuation 

inherent to MJ cells and stable energy output. The total 

energy was 264 kWh/m2

 by 1980 hours of sunshine 

duration. The energy per rating was 940 kWh/kWp (28 % 

and 1kW rating). The annual efficiency (annual energy 

generation devided by annual insolation) was 20.5 %. This 

is almost two times more energy than typical flat-plate 

system despite the well-known preconceived idea that 

CPV is not suitable to wet area like Japan. 

4. Applications (1) –rooftop on apartment houses 

 One of the possible applications in Japan is a rooftop 

on the apartment houses. A new light weight tracker 

(Figure 1) and light weight module is being developed. 

The weight is 0.3 kg/w including modules. The weight 

does not include the base structrue. 

Figure 1. A new 3kW tracker developed by Daido Metal 

5. Applications (2) – See-through PV! 

 Another interesting application is what we call the tree 

planting PV (Figure 2). The CPV only utilizes direct 

beam in the sunlight which is often harmful for tree 

planting. The CPV system without the back cover is 

transparent to the diffused sunlight. The CPV module 

shades the strong direct beam and provides rich diffused 

sunlight to plants. With this transparent module, the area 

under the module is no longer the dead area. Different 

from “see-through” flat-plate module, the power 

generation is not compromised at all.. 

Figure 2. CPV for “Breeding Plants” that collects direct 

beam and provides diffused sunlight to the underneath 

plant. 

6. Where are we going? 

 The direction of future CPV will be discussed. 
8

The Triple Sustainability of CPV Within the Framework of the Raviv Financing Model 

David Faiman1

, Dov Raviv2, Roy Rosenstreich2

1

Ben-Gurion University, Jacob Blaustein Institute for Desert Research 2

MST, Ltd. 

Email: faiman@bgumail.bgu.ac.il 

Abstract: In a recent series of remarkable presentations [1,2,3], Dov Raviv has shown that CPV can be 

highly cost-effective, in a subsidy-free manner, if introduced on a sufficiently large scale. Raviv1s model 

involves financing via an open credit line that is repaid with interest entirely from revenues that accrue 

from a steadily increasing number of Very Large Solar Photovoltaic (VLS-PV) power plants. Within the 

framework of an International Energy Agency (IEA) Task 8 PV Specialists Group study, we have 

recently applied this model to various countries in the Middle East [4]. Although those countries have 

different population growth rates and electricity needs, a number of common features emerged from that 

study that will be the focus of the present paper. Specifically, we found that CPV can be sustainable in 

three completely independent ways. First is the familiar meaning of sustainability that solar energy in 

general promises compared to the steadily dwindling reserves of fossil fuel. Second, we find that within 

the context of the Raviv model, because the credit line and interest are paid back well within the expected 

lifetime of the VLS-PV plants, revenues from the latter are sufficient to continue funding the construction 

of new plants without the need for any further investment. The second sense in which CPV becomes 

sustainable is therefore that it is a technology that can eventually "breed" itself without external funding. 

Thirdly, we find that revenues from the steadily increasing number of VLS-PV plants become so large 

that they are even capable of fully financing the construction of TWO new plants per year: one to keep 

pace with rising electricity needs and the other to replace a 30-year old plant that has reached the end of 

its assumed useful life. The third sense in which CPV technology becomes sustainable is therefore its 

ability to renew itself at the end of effective system life, once again without external funding.
9

SolarGenix Concentration Solar Thermal 

Gilbert Cohen 

SolarGenix, LLC. 

Phone (919) 871-0423 

Abstract not available. 
10

DOE High Performance Concentrator PV Project: III-V Multijunction Concentrators 

Robert McConnell* and Martha Symko-Davies 

National Renewable Energy Laboratory 

1617 Cole Boulevard 

Golden, CO USA 80401-3393 

The U.S. Department of Energy (DOE) initiated the High-Performance Photovoltaic (HiPerf PV) 

Project to substantially increase the viability of photovoltaics (PV) for cost-competitive 

applications so that PV can contribute significantly to both our energy supply and environment. 

To accomplish such results, the National Center for Photovoltaics (NCPV) directs in-house and 

subcontracted research in high-performance polycrystalline thin-film and multijunction 

concentrator devices with the goal of enabling progress of high-efficiency technologies toward 

commercial-prototype products. We will describe the details of the subcontractor and in-house 

progress toward exploring and accelerating pathways of III-V multijunction concentrator solar 

cells and systems toward their long-term goals. By 2020, it is anticipated that this project will 

have demonstrated 33% system efficiency and a system price of $1.00/Wp for concentrator PV 

systems using III-V multijunction solar cells with efficiencies over 40%. 
11

GaInP/GaAs/GaInAs Monolithic Tandem Cells for High-Performance Solar 

Concentrators 

M. W. Wanlass, S. P. Ahrenkiel, D. S. Albin,

J. J. Carapella, A. Duda, J. F. Geisz, Sarah Kurtz, T. Moriarty, and M. J. Romero

National Renewable Energy Laboratory (NREL), 1617 Cole Blvd., Golden, CO 80401 

Email: mark_wanlass@nrel.gov; Phone: (303) 384-6532; Fax: (303) 384-6430 

Abstract: 

The performance of state-of-the-art, lattice-matched (LM), triple-junction (TJ), 

GaInP/GaInAs/Ge concentrator tandem solar cells could be improved substantially by replacing 

the Ge bottom subcell with a subcell having a bandgap of ~1 eV. For the last several years, 

research has been conducted by a number of organizations to develop ~1-eV, LM GaInAsN 

materials to provide such a subcell, but, so far, the approach has proven unsuccessful. 

In this paper, we present a new TJ tandem cell design that addresses the above-mentioned 

problem. Our approach involves inverted epitaxial growth to allow the monolithic integration of 

a lattice-mismatched (LMM) ~1-eV GaInAs/GaInP double-heterostructure (DH) bottom subcell 

with LM GaAs (middle) and GaInP (top) upper subcells. A transparent GaInP compositionally 

graded layer facilitates the integration of the LM and LMM components. Handle-mounted, ultrathin device fabrication is a natural consequence of the inverted-structure approach, which results 

in a number of advantages, including robustness, improved thermal management, incorporation 

of back-surface reflectors, and possible reclamation of the parent crystalline substrate. 

Our initial work has concerned GaInP/GaAs/GaInAs tandem cells grown on GaAs substrates. In 

this case, the 1-eV GaInAs experiences 2.2% compressive LMM with respect to the substrate. 

Specially designed GaInP graded layers are used to produce 1-eV subcells with performance 

parameters nearly equaling those of LM devices with the same bandgap. Preliminary ultra-thin 

tandem devices (0.237 cm^2) have already been demonstrated with NREL-confirmed, one-sun 

efficiencies of 31.3% (global spectrum) and 29.7% (AM0 spectrum). Concentrator devices have 

been fabricated and are currently being tested. Realistic performance modeling of 

GaInP/GaAs/GaInAs tandems shows that practical efficiencies exceeding 40% should be 

achieved for terrestrial concentration ratios of a few hundred suns. 
12

Ultra-High Efficiency Cells for Microconcentrator PV 

Harry Atwater 

California Institute of Technology 

Phone: (626) 395-2197 

Email: haa@caltech.edu

Abstract not available. 
13

GaAs Concentrator Solar Cells for the Italian Electrical System 

Carlo Flores 

CESI S.p.A. 

Via Rubattino 54, 20133 Milano, Italy 

e-mail: flores@cesi.it, phone +39 02 2125 4721, fax +39 02 2125 5530 

Abstract

This paper describes the research and development activities carried out in Italy in the field of 

high efficiency solar cells based on GaAs compounds. This activity is funded by the Research 

Fund for the Italian Electrical System established with Ministry of Industry Decree in year 2000. 

The research is focused on the development of concentrator solar cell components derived from 

the production of space solar cells of CESI. Three fields of investigation are presently 

considered: 

- GaAs and InGaP single junction cells for special concentrator systems. 

- InGaP/InGaAs/Ge triple junction cells. 

- InGaP/InGaAs dual junction cells on Si substrates. 

The cells under development are tested in laboratory as well as in natural light using both Fresnel 

lenses and large dishes. Aim of the activity, however, is not the development of modules and 

systems but the development of reliable solar cell components for the Italian market. 
14

Bandgap Engineering in High-Efficiency Multijunction Concentrator Cells 

R. R. King, R. A. Sherif, G. S. Kinsey, C. M. Fetzer, K. M. Edmondson, 

D. C. Law, H. L. Cotal, D. D. Krut, J. H. Ermer, and N. H. Karam 

Spectrolab, Inc., Sylmar, CA 

International Conference on Solar Concentrators for the Generation of Electricity or Hydrogen, 

May 1-6, 2005, Scottsdale, AZ 

Sunlight is an energy resource with a wide geographic distribution, making it easily accessible 

for solar electricity generation in many communities. However, it is also distributed over a wide 

range of wavelengths, complicating efficient photovoltaic energy conversion. Multijunction 

solar cells divide the solar spectrum into narrower wavelength bands, allowing more efficient 

conversion by the individual subcells, each with bandgap energy tuned to the photon energies in 

the corresponding band. The GaInP/GaInAs/Ge 3-junction cell is a multijunction (MJ) cell 

configuration combining III-V and group-IV subcells, that has achieved record efficiencies 

(37.3%, 175 suns) under the terrestrial AM1.5D low-AOD standard spectrum. Efficiencies over 

40% and even 50% are possible in principle if a different combination of subcell bandgaps can 

be used to partition the solar spectrum. Group-III sublattice ordering phenomena, and the use of 

unconventional semiconductor materials such as metamorphic GaInP and GaInAs, and ~1-eV 

GaInNAs with dilute nitrogen composition, are discussed to achieve the desired combination of 

bandgaps in new types of high-efficiency terrestrial MJ solar cells. Concentration ratios of 

~500X, delivered by a variety of reflective and refractive schemes now deployed in the field, 

reduce the cost of such cells dramatically by reducing the cell area required. Investigation of 

new semiconductor materials and device structures to reach new heights in cell efficiency holds 

the promise to break through to photovoltaic system costs competitive with conventional power 

sources. 
15

Ultra-High Concentration Effects in Multi-Junction Solar Cells 

J.M. Gordon1,2,3, E.A. Katz ,W. Tassew and D. Feuermann 

Department of Solar Energy and Environmental Physics, Jacob Blaustein Institute for Desert Research, 

Ben-Gurion University of the Negev, Sede Boqer 84990, Israel 

1 and The Pearlstone Center for Aeronautical Engineering Studies, Department of Mechanical Engineering, BenGurion University of the Negev, Beersheva, Israel 

2 and Schools of Engineering and Natural Sciences, University of California, Merced, CA 

3 Corresponding and presenting author, Postal address: University of California, POB 2039, Merced, CA 95344, Tel 

209-724-2939, Fax 209-724-2912, e-mail jeff@bgu.ac.il 

Abstract

 We report results of ultra-high flux photovoltaic characterization of monolithic triplejunction GaInP2/GaAs/Ge and tandem GaInP/GaAs solar cells using a new high-flux real-sun 

probe predicated on mini-dish fiber-optic concentrators. Our aims were to investigate the 

sensitivity of the cell efficiency to the flux level and distribution. 

 Radiation on the cell was moderated with an iris on the concentrator's window. Near-perfect 

flux uniformity was achieved with a square cross-section kaleidoscope. Irradiating the cell 

directly from the distal fiber tip and varying fib/er height above the cell, we could realize a wide 

range of flux distributions, including the extreme localized irradiation limit of contact with the 

cell such that radiation projected beyond the fiber tip was negligible. The localized irradiation 

method allows mapping inhomogeneities in cell construction, e.g., via the spatial sensitivity of 

current-voltage curves. 

Our uniform-irradiation and localized-irradiation measurements yield characteristic plots 

for the flux dependence of efficiency that are similar to those reported previously for the same 

fully-irradiated cells, but provide additional information on cell dynamics. The increase of the 

flux values at which efficiency peaks in localized-irradiation tests can be predicted from 

fundamental solar cell modeling, and bodes well for the high-efficiency performance of future 

generations of smaller-area concentrator cells. 

In one instance, ultra-high-flux localized-irradiation measurements (at 3200 suns and 

above) revealed a sharp degradation in cell performance that can uniquely be associated with the 

inadequacy of one of the cell's tunnel diodes. This in turn led to the first predictable and 

reversible observation of hysteresis in photovoltaic current-voltage curves. The ramifications of 

these findings for photovoltaic design and diagnostics are addressed, and a non-destructive 

determination of the peak and valley threshold current densities of tunnel diodes is presented. 
16

GaInNAs Junctions for Next-Generation Concentrators: Progress and Prospects 

D.J. Friedman*, A.J. Ptak, S. R. Kurtz, J.F. Geisz, and J. Kiehl 

National Renewable Energy Laboratory 

1617 Cole Blvd, Golden, CO 80401 

*daniel_friedman@nrel.gov; phone 303-384-6472; fax 303-384-6430 

We discuss progress we have made toward the development of GaInNAs junctions with 

performance good enough for application in the next generation of multijunction concentrator 

cells. The short diffusion lengths in GaInNAs have stymied the achievement of the near-100% 

quantum efficiencies required for current matching in the GaInP/GaAs/GaInNAs/Ge fourjunction (“4J”) structure. A significant development is the demonstration of very wide depletion 

widths in GaInNAs junctions using MBE growth, making possible p-i-n junctions with 3-μmwide i-layers. The resulting drift field yields near-100% internal QEs, a significant proof-ofconcept advance for GaInNAs junctions. The width and low doping of the i-layers raises the 

concern that the resulting series resistance could make such junctions incompatible with 

concentrator operation. Fortunately, testing of our p-i-n junctions at high currents shows these 

devices not to suffer significant voltage losses under concentrator operation. We explain this 

result by considering the high density of carriers injected into the i-layer at high operating 

currents, and show that in general, a GaInNAs p-i-n junction which has near-100% QE can be 

expected also to have a small voltage loss under concentration. 

For the MBE-grown p-i-n junctions, bandgaps as low as 1.15 eV have been demonstrated, but 

1.0 eV will need to be achieved for current matching in the 4J structure. Likewise, the ~80% QEs 

of the MOVPE-grown junctions need to be increased to near 100% for current-matching to the 

4J structure. An alternative approach to next-generation multijunction cells, under development 

at Spectrolab and Fraunhofer, uses a five-or six-junction (“6J”) structure with lower currentmatching requirements than the 4J structure. We project what the efficiencies of the 6J structure 

would be if the state-of-the-art MBE- and MOVPE-grown GaInNAs junctions can be 

incorporated into this structure. 
17

Low Cost Concentrator Cells from One Sun Production Cell Technology 

T M Bruton 

NaREC, Eddie Ferguson House, Ridley St., Blyth, NE24 3 AG, UK 

Tel: +44 1670 359555 Fax: +44 1670 359666; e-mail: tim.bruton@narec.co.uk

The present silicon shortage creates an opportunity for concentrating systems but to be adopted 

systems costs must be comparable. It is axiomatic that in concentrating systems lower cell cost 

can be achieved and this pays for the added complexity of the concentrating system relative to 

flat plat. These cell cost reduction have proved elusive in reality. Modifying one sun 

technologies offers a route to volume manufacture of concentrator cells with low overheads for 

short production runs. The LGBC cell technology is particularly suitable for concentrator 

technology as high current carrying capacity can be structured into the cell with minimal shading 

by the metallization. The laser cutting technology also means a range of sizes can easily be cut 

from the basic 125 x 126 mm p-square wafer. The technology has proved adaptable to a range of 

concentrating systems. Good results have been obtained for 112 X6 mm cells in untracked CPC 

2.4 x modules for BIPV. Half one sun cells have worked well in the ARCHIMEDES 2x 

passively tracked system. Cells 115x45 mm have demonstrated efficiencies between 18 and 20% 

for concentration between 20 and 30x in both linear Fresnel lens and Parabolic reflector systems. 

Recent good results have been achieved at 100X for point focus systems. Assuming a cell 

manufacturing cost of $2/Wp for a one sun cells then cell prices fall from $1/Wp at 2x through 

$0.27/Wp for 20x to below $0.1/Wp at 100X. Major production facilities are not required and 

even the modest 50KW/p.a pilot facility at NaREC could produce over 100 MWp of 

concentrating cell with modest investment. 
18

Efficient Solar Photovoltaic Mirror Modules for Half the Cost of Today’s Planar Modules 

L. Fraas, J. Avery, and H. Huang 

JX Crystals Inc, 1105 12th Ave NW, Suite A2, Issaquah, WA 98027 

lfraas@jxcrystals.com, (425) 392 5237; Fax: (425) 392 7303 

ABSTRACT

1. Opportunity and Solution

 The demand for solar photovoltaic (PV) cells and 

modules has far outstripped PV cell supply, e.g. 

Germany and Japan are buying everything they can find 

and module prices are rising. Solution: JX Crystals Inc 

has a 3-sun mirror module design that uses 1/3 the cells 

to triple module production at a lower cost.

2. The Linear Mirror Module Concept 

A problem for concentrated sunlight PV systems has 

been the requirement for investment in special cell and 

module manufacturing facilities. Herein, we describe a 

new concentrator module design that uses existing planar 

cells. We simply cut standard 125mm x 125mm 

SunPower A300 cells into thirds. In addition, our 

module design uses standard circuit laminant fabrication 

procedures and equipment. However, we add a thin 

aluminum sheet at the back of the laminant for heat 

spreading. While a standard planar module contains 

rows of 125mm x 125mm cells, our low concentration 

modules consist of rows of third-cells with each row 

now 41.7 mm wide. We then locate linear mirrors with 

triangular cross sections between the cell rows. The 

mirror facets deflect the sun’s rays down to the cell 

rows. The result is the 3-sun concentrator module shown 

in figure 1 below. Since mirrors are over ten times 

cheaper than expensive single crystal cell material, these 

3-sun modules can be made at half the cost of today’s 

solar PV modules. 

Figure 1: 3-sun mirror module

 

3. Results to date

 As shown in figure 2, we have fabricated and tested 2-

sun mirror modules previously. These modules have 

successfully passed hail stone, thermal cycling, and hipot tests at ASU. 

 Our more recent efforts have been focused on using 

SunPower A300 cells because they are both higher in 

efficiency and can be cut into thirds as shown in figure 3. 

Figure 2: Two of JX Crystals 2-sun mirror modules 

on an Array Technologies TR15 sun tracker in 

outdoor test. 

Figure 3: View from the back side of a 125 mm x 123 mm 

A300 SunPower cell before and after being cut into 3rd cells. 

We have now laminated some 3rd cells into test coupons 

and measured their outputs at 3 suns before and after 50 

thermal cycles between -40 C and +90 C. Photos of these 

test coupons are shown in figure 4 along with the measured 

power outputs. There was no degradation. We also 

measured the temperature rise at only 3.3 C. 

 Figure 4: Tested coupons.

4. Summary 

This design has the following major advantages: 

• $1.50 per W instead of $3 per W for today’s modules 

• Evolutionary design using existing cells and module 

production methods 

• 20% efficient cells immediately available 

• Triple production with no new factory 

• Pre-qualified by design ● Patent pending 

• Compatible with existing trackers 

ID 

Efficiency 

BEFORE 

50 Thermal 

Cycles 

Efficiency 

AFTER 

50 

Thermal 

Cycles 

T84 19.5% 20.0% 

T85 20.1% 19.5% 
19

Practical Design of PV Modules and Trackers for Very High Solar Concentration 

V. D. Rumyantsev 

Ioffe Physico-Technical Institute, Russian Academy of Scienses 

26 Polytechnicheskaya str., St. Petersburg 194021, Russia 

ABSTRACT 

 The following solar PV concepts connected with 

high concentration approach are under development: smallaperture area and short focal length primary Fresnel lenses; 

smooth-surface secondary mini-lenses; design for the 

concentrator modules with III-V tandem cells; close-loop 

strategy for sun-tracking; solar installations, realizing the 

above concepts Lens panel formation and cell mounting 

processes have been developed. The sun trackers for 1 kWp 

of installed capacity have been built and tested 

. 

1. Module Design 

 A concept of small-aperture area concentrator sub-modules 

in PV module design leads to rise in cell efficiency and 

saving the semiconductor and structural materials. It may be 

realized at retention (in the whole) of a distributed character 

of sunlight conversion and heat dissipation− similar to the 

case of systems without concentration In our design, 

refractive-type concentrators (Fresnel lenses) have a 

composite structure: microprisms are formed from 

transparent silicone rubber contacting with front glass sheet 

as a protective superstrate. Quantities of the lenses are 

arranged on a common superstrate in a view of lens panel. 

The smooth-surface secondary minilenses arranged as an 

intermediate composite (glass-silicone) or monolithic (glass) 

panel are inserted between panel of the primary Fresnel 

lenses (each lens of 40 x 40 mm2

) and panel of the solar 

cells. The cells as small as 1.2 mm in designated area 

diameter operating at very high concentration ratio (more 

than 1000x) can be used in the PV modules with secondary 

lenses. Developed formation process allows fabricating the 

modules of total area up to 0.5 x 0.5 m2

. Air interspace 

between front and rear glass plates have no hermetical 

sealing with respect to atmosphere, so that environmental 

protection of the cells is carried out due to hermetical sealing 

a thin air gap between rear glass plate and trough-like shaped 

metallic heat sinks. Heat dissipation takes place immediately 

to the surroundings, by-passing the rear glass plate (see Fig. 

1). 

Figure 1: Experimental module with primary and secondary 

lenses equipped with two ventilation tubes. 

2. Trackers Design 

 High accuracy of tracking to the sun is a specific feature 

of the high-concentration PV method. Each our tracker is 

equipped with main (accurate) sensor and additional one, 

both operating as a part of a close-loop system. Main sensor 

can align the tracker with the sun to within 0.05 degree of arc 

accuracy with acceptance angles of ±70° in both horizontal 

and vertical directions. Additional sensor makes wider the 

“East/West” turning angle (up to 270°, if necessary). Both 

sensors are mounted on the suspended frame together with 

PV modules. They are not sensitive to variations in 

illumination level, caused by presence and movement of 

clouds, as well as to parasitic light reflected from various 

objects during a day. For this, main sensor includes two subchannels in both horizontal and vertical channels equipped 

with tandem-type III-V cells with increased output voltage. 

Differential signals are generated in correspondence with 

misalignments of the installation to the sun in azimuth and 

elevation. Additional sun sensor consists of three tandem PV 

cells. 

 In construction of the trackers the cheapest structural 

materials are used, such as roll-formed perforated channels 

and angles, made of zinc-protected steel. All members are no 

longer than 2 meters. Tracker consists of two main moving 

parts (see Figure 2): a base platform moving around vertical 

axis, and a suspended one with PV modules moving around 

horizontal axis. The base platform is equipped with three 

wheels one of which is connected with azimuth drive. Only a 

flat territory is necessary for tracker operation. The 

suspended platform is a frame where concentrator modules 

are installed as three steps of a stair. Position of the 

suspended frame can vary in the range of ±45° symmetrically 

about a horizontal plane

Figure 2: Sun tracker with concentrator PV modules 

installed on the roof of the Ioffe Institute. A similar tracker 

has been delivered to NREL (USA) and deployed in the 

frame of the IPP Program under Subcontract AAT-3-32614-

01. 
20

New Cassegrainian PV Module using Dichroic Secondary and Multijunction Solar Cells 

L. Fraas1, J. Avery2, H. Huang2, and E; Shifman3

1&2JX Crystals Inc, 1105 12th Ave NW, Suite A2, Issaquah, WA 98027 1

lfraas@jxcrystals.com, (425) 392 5237; Fax: 392 7303 3

SRS Engineering & Agencies Ltd., Israel

ABSTRACT 

1. General Objective

Our objective is to demonstrate a 33% efficient solar 

concentrator PV module using 40% efficient 

multijunction (MJ) solar cells. This very high efficiency 

module can then produce cost competitive solar electric 

power. 

2. The Cassegrainian Module Concept 

Herein, we describe a new concentrator PV module that 

provides conveniently for two cell locations so that ideal 

3J (=2J+1J) and 4J (=2J+2J) cell efficiencies can 

potentially be obtained. A new module design using a 

Cassegrainian mirror configuration is shown in figure 1. 

This Cassegrainian configuration splits the sun’s 

spectrum using a dichroic hyperbolic secondary mirror 

providing two focal points, one for the near visible and 

the second for the infrared (IR). The 2J GaInP/GaAs 

cell can be located at the near visible light focus and a 

GaSb IR booster cell or a GaInAsP/GaInAs lattice 

matched 2J cell can be located at the long-wavelength 

infrared (IR) focal point. 

GaSb IR Cell

InGaP/GaAs

2J Cell

Cassegrain PV Module

33% Efficient PV Module

GaSb IR Cell

InGaP/GaAs 2J Cell

Figure 1: Cassegrainian PV Module Concept uses a 

dichroic hyperbolic secondary mirror to split the 

spectrum into short and long wavelength bands to create 

two focal points. 

The first advantage of the Cassegrainian module is 

that the dichroic secondary either transmits or reflects. 

There are no absorption or shading losses for the IR cell. 

A second advantage for this Cassegrainian design is that 

the GaInP/GaAs cell is now a straightforward design 

with gridlines on top and full metal on back. A third 

advantage is in thermal management in that the heat load 

is now divided into two separate locations. 

3. Cassegrain Module with GaInP/GaAs-GaSb Cells 

A preliminary design for a 32.4% efficient module that is 

based on today’s existing GaInP/GaAs and GaSb cells is 

shown in figure 2. Detailed drawings for the various 

components have now been completed and we are now 

ordering the parts required to implement this design. The 

primary mirror size in this module is 25 cm x 25 cm. 

Figure 2: Cassegrain module design with 

dimensions (mm). 

4. Projected Performance 

 Table 1 summarizes the projected performance for this 

near term module. The efficiencies of the component cells 

sum to 38% and given module optical losses, a module 

efficiency of 32.4% is predicted. The result is a prediction 

of 20 W for a 25 cm x 25 cm unit module.

Table 1: Projected Module Performance 

 GaInP/GaA

s 2J cell 

GaSb IR 

cell 

TOTAL 

Input Solar Flux STC 

25 x 25 cm2

 Primary 

62.5 W 62.5 W 

Cell Efficiency 30% 8% 38% 

Optical Efficiency 85% 86% 

Combined Efficiency 25.5% 6.9% 32.4% 

DC Power Out 15.9 W 4.3 W 20.2 W 

5. Conclusions 

In conclusion, the Cassegrainian PV module design 

provides two separate cell locations, and makes achieving 

near ideal efficiencies for 3J and 4J cells practical. (38% 

near term with 30% GaInP/GaAs + 8% GaSb). The ideal 

efficiency under concentration for hybrid 3J cells = 2J + 1J 

is 47% while the ideal efficiency for hybrid 4J cells = 2J + 

2J is 52%. 
21

Design, Manufacturing, and Testing of a Prototype Multijunction Concentrator Module 

D.J. Aiken, M.A. Stan, S. Endicter, G. Girard, P.R. Sharps, E. Fuller 

Emcore Photovoltaics 

Mailing address: 10420 Research Road S.E., Albuquerque, NM 87123

Email address: dan_aiken@emcore.com

Telephone: 505 332 5084 

Fax: 505 332 5038 

Abstract: 

As a commercial manufacturer of III-V multijunction solar cells, Emcore has made a business case for a 

vertically integrated approach to the commercialization of high concentration PV modules using III-V 

multijunction cells. Towards this goal we have leveraged both internal and external (NREL HiPer PV 

program) funding to make technical advances in three areas: the development of high-concentration 

multijunction cell technology, design and construction of a prototype module, and the establishment of 

on-site, on-sun testing capability. Complete module prototypes have been designed and constructed, 

including copper-based receivers for electrical interconnect and thermal management, PMMA Fresnel 

primary lenses of 520 cm2 aperture area, and reflective secondary optical elements for beam 

homogenization and improved tracking tolerance. These elements have been incorporated into both 

single cell and 4 cell module prototypes. On-sun testing has resulted in over 24% module-level 

efficiencies.
22

The FLATCON Concentrator PV-Technology 

A.W. Bett, C. Baur, H. Lerchenmüller, G. Siefer, F. Dimroth 

Fraunhofer Institute for Solar Energy Systems ISE 

Heidenhofstrasse 2, 79110 Freiburg, Germany 

Andreas.Bett@ise.fraunhofer.de, phone: +49 761 45885257, fax: +49 761 45889250 

ABSTRACT 

This paper reports about the actual technology status of 

the FLATCON-technology developed at Fraunhofer ISE. 

This includes the fabrication of multi-junction lattice 

mismatched concentrator solar cells. An efficiency of 35.2 

% @ 300-600 suns was recently achieved for this type of 

cell. FLATCON -modules are based on an all-glass 

design. Completely hermetically sealed modules and 

modules using a special filter were tested. Results of more 

than two years of outdoor experiences as well as testing in 

climate chambers will be presented. Recently, the optical 

efficiency of the Fresnel lens was slightly improved to 82 

%. Together with the new triple-junction cells we expect 

operating efficiencies up to 28 %. In February 2005 the 

company Concentrix Solar GmbH was founded aiming to 

manufacture concentrator systems based on the 

FLATCON technology. 

Extended description 

The FLATCON technology has been developed during 

recent years at Fraunhofer ISE in a co-operation with the 

Ioffe-Institute, St. Petersburg and is now ready for the 

market. 

Fraunhofer ISE has a more than 15 year experience in the 

development of III-V based concentrator solar cells. 

Starting with LPE-grown GaAs single-junction solar cells 

in the 80ies, we developed multi-junction concentrator 

solar cells using MOVPE technology in the year 2000. 

From the very beginning we were focusing on lattice 

mismatched Ga0.35In0.65P and Ga0.83In0.17As material 

grown on GaAs or Ge. The reason for choosing this path 

of research is simply that higher cell efficiencies are 

theoretically achievable compared to the commonly used 

lattice matched Ga0.51In0.49P and GaAs materials. In 2001 

we achieved an efficiency of 31.1. % @300 suns (AM1.5d 

“old”, area of 0.1326 cm2) for a Ga0.35In0.65P/ 

Ga0.83In0.17As dual-junction concentrator solar cell. This 

had proven the validity of the use of lattice mismatched 

material for high efficiency concentrator solar cells. Those 

dual-junction solar cells are still the working horse in our 

current FLATCON -modules under test. However, very 

recently we started to manufacture triple-junction solar 

cells growing the lattice mismatched 

Ga0.35In0.65P/Ga0.83In0.17As structure on activated Gesubstrates. An efficiency of 35.2 % @ 300-500 suns 

(AM1.5d, low AOD) was achieved on circular 2 mm 

cells. This cell type is optimised for the use in our 

FLATCON -modules, thus not aiming for record 

efficiencies. For example, the front grid was designed 

assuming a Gaussian illumination profile with a 5 times 

higher intensity in the centre (as compared to the averaged 

intensity). This leads to a higher metalisation in the centre 

of the cell lowering the efficiency under a homogeneous 

illumination in the laboratory. An interesting feature of 

this cell is that all the three sub cells (Ga0.35In0.65P, 

Ga0.83In0.17As and Ge) generate nearly the same amount of 

current, as determined by external quantum efficiency 

measurements. 

However, in contrast to flat plate PV in concentrator PV 

we have to consider the interaction between concentrating 

optics and the cell. Thus, we have to optimise the 

concentrator system. Fraunhofer ISE is one of the few 

institutes world wide which is developing all components: 

cells, modules, tracking system control and BOS. As 

mentioned, circular cells 2mm in diameter and designed 

for operation under 500x are used in our Fresnel Lens 

All-glass Tandem cell CONcentrator (FLACTON) 

modules. A special technology was developed for the 

concentrating optics: 48 Fresnel structures (4x4 cm2 each) 

are stamped into a 0.2 mm thin silicone film on glass. The 

frame of the modules are made from glass plates with a 

height of 75 mm. The cells are soldered on a copper plate 

and subsequently glued to a glass sheet using pick and 

place machines. The module is sealed with structural 

silicone. While at the beginning we used hermetically 

sealed modules we recently introduced a small filter to 

allow for pressure exchange. The modules were tested on 

our tracking system for more than 2 years and we carried 

out indoor tests in climate chambers. We have found that 

the FLACTON -modules work reliable and we measured 

an efficiency of 22.7 % under operating conditions using 

dual-junction solar cells. However, at the conference we 

will present the first results of FLACTON-modules 

using the recently developed triple-junction cell as well as 

an improved optical efficiency. Thus, we expect module 

efficiencies higher than 25 % up to 28 %. In combination 

with the relatively simple manufacturing technologies we 

expect costs below 2.5 €/Wp assuming a 20 MW 

fabrication capacity. In order to go this fabrication path 

the company Concentrix Solar GmbH was founded as a 

spin-off company of Fraunhofer ISE. 
23

Planar Concentrators at the Etendue Limit 

Roland Winston1

, Jeffrey M. Gordon1,2 

1

School of Natural Sciences and School of Engineering, University of California, Merced 95344, USA. Email: 

rwinston@ucmerced.edu 2

Pearlstone Center for Aeronautical Engineering Studies, Ben Gurion University of the Negev, Beersheva 84105, Israel 

Abstract 

Aplanatic imaging concentrators recently proposed by Gordon et al are integrally combined with nonimaging flux boosters to 

produce an ultra-compact planar concentrator that performs close to the etendue limit. Such designs are attractive for highefficiency multi-junction solar cells. Current commercial fabrication technologies can realize cell efficiencies of 40% at high

flux (hundreds to thousands of suns) in cells of order one square millimeter. The all-dielectric designs presented here should be 

capable of (a) generating about one watt from such a one square millimeter cell, (b) accommodating liberal optical tolerances, 

(c) realizing the fundamental compactness limit of a 1/4 aspect ratio (f-number), (d) completely passive cooling, (e) a 

concentrator mass that is equivalent to a 5 mm thick pane of glass, as well as (f) precision mass production via existing glass

and polymeric moulding techniques. 
24

Hemispherical Solar Concentrator Corrected for Aberrations 

Ralf Leutz, Harald Ries 

Physics Department, Philipps-University, Renthof 5, 35037 Marburg, Germany; ralf.leutz@physik.unimarburg.de

1. What Diocles Didn’t Know 

 When Diocles around 200 B.C. compared the ‘burningpower’ of a hemispherical and a paraboloidal mirror, he 

knew everything about their geometries. He didn’t know 

that it is possible to analytically find the shape of a 

secondary concentrator for the hemispherical primary, 

which would correct spherical aberrations. 

The secondary’s shape was not found until 1957 [1]. We use 

this shape, and optimize its position relative to the primary 

and the target. The result is a solar concentrator for medium 

to high concentration, with the inherent advantages of the 

spherical shape, i.e. the geometry is easier to make because 

of its constant local slope, and the primary may be 

constructed as stationary concentrator, with only the 

secondary tracking the sun. 

 

Figure 1: Spherical primary mirror with secondary 

concentrator. Version with medium concentration 

1000 X, receiver out of the rays’ paths, integrated into 

the primary mirror for cooling 

2. Correction of Coma Using a Secondary 

 Head’s solution is valid only for a point source. For small 

extended sources, such as the sun, the aberration caused by 

non-paraxial incidence is coma. Coma can be corrected by 

adhering to the Abbe-sine-condition. 

Our design follows this principle. We find two separate 

maxima to an objective function, incorporating the deviation 

from the Abbe-sine-condition, the concentration ratio, and 

three types of shading. 

Other configurations are possible, such as the version with 

medium concentration of 1000 X in Fig. 1, where the 

receiver is integrated into the primary for cooling and 

constructive reasons. This is an example of a system with a 

tracking primary. 

3. Performance Comparison with the Paraboloid 

 The ideal paraboloid remains superior in optical 

performance to the spherical primary with secondary for all 

but the highest concentration ratios. A typical irradiance 

distribution is given in Fig. 2. Both systems’ performances 

are close, and a practical decision must include the 

manufacturability of the respective geometries, and the 

operational advantage of the spherical concentrator. 

Figure 2: Irradiance distribution on the target of 

spherical primary with secondary concentrator, and 

ideal parabolidal concentrator of high concentration 

>10 000 X 

4. Conclusions 

 We have designed a new class of spherical primaries with 

corrective secondary mirrors for solar concentration. The 

systems are competitive with paraboloidal geometries of 

medium and high concentration ratios. 

References 

1. Head, A.K., A new form for a giant radio telescope.

Nature, 1957. 179: p. 692-693. 
25

Realization of Compact, Passively Cooled, High-Flux Commercial Photovoltaic Prototypes 

Daniel Feuermann1

, Jeffrey M. Gordon1,3,4 , Steve Horne2, Gary Conley2 and Roland Winston3

1 Department of Solar Energy & Environmental Physics, Blaustein Institute for Desert Research, 

Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel 

2 H2Go Corp., 12021 Magnolia Court, Saratoga, CA 95070 

3 Schools of Engineering and Natural Sciences, University of California, Merced, CA 95344 

4 Corresponding and presenting author, Postal address: University of California, POB 2039, Merced, 

CA 95344, Tel 209-724-2939, Fax 209-724-2912, e-mail jeff@bgu.ac.il 

Abstract

We report on the materialization of a recent conceptual advance in high-flux photovoltaic concentrators 

into first-generation commercial prototypes. The design strategy employs a tailored imaging dualmirror system, with a tapered glass rod that boosts concentration and accommodates greater 

concentrator optical errors. The final designs were severely constrained by the need for ultra-compact 

(minimal aspect ratio) modules, simple passive heat sinks, liberal optical tolerances, employing 

commercial off-the-shelf solar cells, and practical considerations of inexpensive fabrication 

technologies. Each concentrator has a geometric concentration of 625 and irradiates a single 100 mm2

square triple-junction high-efficiency solar cell at a net flux of 500 suns. 
26

One-Axis PV Sun Concentrator Based on Linear Nonimaging Fresnel Lens 

Ralf Leutz 

Physics Department, Philipps-University, Renthof 5, 35037 Marburg, Germany; ralf.leutz@physik.unimarburg.de

Leonid B. Rubin, Alexander S. Osipov, Vasili Y. Tarasenko, Valerie M. Nebusov 

Day4 Energy Inc., 102 4475 Wayburne Drive, Burnaby BC V5G 4X4, Canada; lrubin@day4energy.com

This paper is the result of a fruitful cooperation, and will be 

presented by both leading authors. 

1. The Concentrator Concept 

 The arched nonimaging Fresnel lens [1] has been 

prototyped and tested (Fig. 1) with the intention to create a 

marketable solar concentrator for one-axis tracking. 

The concentrator system is based on PV cell technology 

proprietary to Day4 Energy Inc. The cell is best suited for 

low concentration ratios between five and ten. 

 

Figure 3: Nonimaging arched Fresnel. The reflective 

paper is held approximately at the receiver level, while 

the hands demonstrate the size of the concentrator 

2. The Nonimaging Fresnel Lens 

 The Fresnel lens is based on nonimaging design 

principles, namely the edge-ray principle for extended 

sources. The lens has design acceptance half-angles of 

θ = 6°, and θ = 18° in the cross-sectional plane and the 

plane perpendicular to it, respectively. It features minimum 

deviation/dispersion prisms. The design is matched to the 

one-axis azimuthal tracking of the concentrator. 

3. The PV Cell 

 The 10-cm wide PV receiver employs conventional 

monocrystalline half-finished PV cells with Day4 

proprietary current collecting front and rear side electrodes 

which allow the PV cell to operate under up to 10 suns 

concentrated solar radiation without conversion efficiency 

decline. 

Day4 PV cells production technology is applicable for mass 

production, thus offering a distinctive cost advantage for sun 

concentrator application. 

4. Performance in Simulation and Experiment 

 The optical concentration ratio of the arched nonimaging 

Fresnel lens (i.e. its geometrical concentration ratio 

multiplied by its optical efficiency) is 6.1 for normal 

incidence, including Fresnel losses at the surfaces and 

reflection losses at the kaleidoscope secondary. The 

simulation of other combinations of incidence angles is 

shown in Fig. 2. Experiments with a first prototype revealed 

a design flaw, resulting in a dark. The problem was solved 

for the second lens generation. 

The sun concentrator with water cooled PV receiver was 

tested on 1-axis tracker of Array Technologies Inc. with 

tracking accuracy of ±1.5°. The PV concentrator 

demonstrated an efficiency of 18.2% at 32°C relative to 

solar radiation within half-angle θ = 6°. 

 

Figure 4: Optical performance of the linear nonimaging 

Fresnel lens with kaleidoscope secondary 

5. Conclusions 

 Optimzed linear Fresnel lenses perform well in solar 

collectors of low to medium concentration. This is 

confirmed in simulation and experiment with an arched 

nonimaging Fresnel lens for one-axis tracking. A 

kaleidoscope secondary increases the homogeneity of the 

irradiance and the concentration of the system. 

It is crucial to utilize PV cells designed for this low range of 

concentration, and match the optics with the cell. 

References 

1. Leutz, R., Suzuki, Akio, Nonimaging Fresnel Lenses: 

Design and Performance of Solar Concentrators. 

Optical Sciences. 2001, Berlin: Springer Verlag. 
27

Design of Non-Imaging Fresnel Lens for 500X Solar 

Atushi Akisawa 

Tokyo University of Agriculture and Technology 

Tokyo, Japan 

Email: akisawa@cc.tuat.ac.jp

Abstract not available. 
28

The Evolution of High Intensity Photovoltaic Cells from Thermophotovoltaic Applications 

to High Concentration Solar Applications: Lessons Learned 

Richard J. Schwartz 

Birck Nanotechnology Center, Purdue University, Electrical Engineering Building, Room 313E, 

465 Northwestern Avenue, West Lafayette, IN 47907-2035 

Email: Schwartz@purdue.edu; Phone: (765) 494-0619; Fax: 765 494 6441 

The foundations of the current designs for silicon solar cells used for high-flux concentrator 

systems can be traced to developments that occurred more than thirty-five years ago in the 

development of high intensity thermophotovoltaic cells that were operated under continuous 

illuminations of greater than 30 Wcm-2. The Interdigitated Back Contact Cell, developed for the 

high flux conditions of TPV systems, was directly applied to silicon high concentration terrestrial 

applications. These silicon cells were operated, in 1974, under continuous conditions at flux 

densities of greater than 30 Wcm-2 with efficiencies of 18%. The IBC cells were the direct 

precursor to the point contact cell, which still holds the record for efficiency for silicon cells 

under concentration. One and two dimension computer models developed to design these cells 

were the first solar cell numerical models to provide contact-to-contact models of both minority 

and majority carrier current flows. Many of the lessons learned in the design of these high flux 

cells have a direct influence on today’s cell designs. 
29

Indoor Characterization of Concentrator Modules: Application on the Production Line 

I. Antón1, C. Domínguez2, G. Sala2

1

Instituto de Energía Solar - SEC-UPM 

2

Instituto de Energía Solar - UPM 

ETSI Telecomunicación. Ciudad Universitaria s/n 

28040 Madrid 

Phone: +34 91 5441060 Fax: +34 91 5446341 

E-mail: nacho@ies-def.upm.es

ABSTRACT: 

New concepts of concentrator modules have been proposed in the last years based on high 

concentration refractive optics and cost effective III-V devices at such high concentration levels. 

The concentration ratio in these approaches is higher than 300X, and therefore, the maximum 

acceptance angle of the system is very narrow, in the range of one degree. A consequence is that 

a sun tracking system is required in normal operation. Nevertheless, outdoor characterization 

could be adequate for research work but it is not practical for its use on the production line so the 

well-know flash lamp technique has been explored in this work. The main difference with 

conventional panels is that not only the irradiance requirement must be fulfilled, but also the 

angular size of the light source is essential. This last condition becomes harder when combined 

with large area modules (larger than 500 cm2

). For example, a point light source should be 

placed at a quite fair distance (more than 20 m) to illuminate the whole aperture within the 

acceptance angle and the practical power of commercial lamps would not allow to reach the 

irradiance values of 0.1W/cm2 in the module. Several approaches have been studied and one 

based on a large area optical device to fulfill both illumination conditions has been chosen. The 

requirements of the light source, the design and manufacturing of the optical device are the most 

novel contributions of this work. 

[1] Bett AW, Baur C, Dimroth F, Lange G, Meusel M, Riesen S van, Siefer G, Andreev VM, 

Rumyantsev VD, Sadchikov NA. FLATCON-MODULES: Technology and Characterization, 

Proceedings of the 3rd WCPEC, 2003. 

[2] Andreev V, Ionova E, Rumyantsev V, Sadchikov N, Shvarts M. Concentrator PV Modules of 

“All-Glass” Design with Modified Structure. Proceedings of the 3rd WCPEC, 2003. 

[3] Díaz V, Alonso J, Hernández M, Álvarez JL, Labrador M, Blen J, Mohedano R, Benítez P, 

Miñano JC, Preuss W, Gessenharter A. Progress in the Manufacture of Ultra Flat Optics for 

Very High Concentration Flat Panels. Proceedings of the 29th IEEE PVSC, 2002; 1580-1583 

[4] Araki K, Kondo M, Uozumi H, Yamaguchi M. Development of a Robust and High 

Efficiency Concentrator Receiver. Proceedings of the 3rd WCPEC, 2003. 
30

On-Sun Testing of Multijunction PV Cells 

S. Kusek 

Concentrating Technologies, LLC 

7234 Hwy. 431 South 

Owens Cross Roads, AL 35763

ABSTRACT 

Concentrating Technologies, LLC (CT) is developing a solar power conversion system using reflective 

optics and high efficiency PV cells for utility-scale use. This high concentration PV (HCPV) system 

uses a small-footprint power conversion unit (PCU) that can be combined to form a myriad of power 

levels on two-axis tracking systems. 

CT has performed extensive test work with Arizona Public Service and Spectrolab (SL) over the past 

five years to try and identify potential issues with using SL’s multijunction cells in a utility 

environment. CT started working with dense arrays and the preferred design has changed into a single 

cell PCU at about 500x. On-sun testing has led to improvements in the basic designs for the receiver, 

heat exchanger, optics, and cell. The specific power has climbed from about 5 W/cm2 to almost 14 

W/cm2 with an 850W/m2 sun. The test program has given confidence that the latest Spectrolab triplejunction PV cells are ready for long-term utility-scale deployment. 
31

CPV Sun Tracking at InSpira 

I. Luque-Heredia 

Inspira, SL 

C/Chile, 10, 28290, Las Matas, Madrid, Spain, iluque@inspira.es

ABSTRACT 

This paper presents a general overview of the projects developed at Inspira in the field of sun 

tracking for photovoltaic concentration technologies. Being sun tracking, Inspira’s major point of 

contact with CPV efforts up to now, the development of the EPS-Tenerife sun tracking control 

unit for BP Solar’s EUCLIDESTM constitutes our first attempt in this domain which concludes 

with the production in 1998 of 14 sun tracking control units for the 480kWp EUCLIDES plant in 

Tenerife. Second significant landmark, is the development, still under progress, of a complete 

sun tracking solution for Isofoton’s micro-concentrator modules. Always working on hybrid 

approaches, based in an ephemeris computation core complemented by some sort of feedback, 

both adaptive and model based strategies have been developed. These developments, presently 

being supported by several EC initiatives, such as Fullspectrum or the Marie Curie Fellowship

programme, are also being customized and tested in new concentrator prototypes such as PVFibre or Proteas.
32

Outdoor Testing of GaInP2/GaAs Tandem Cells with Top Cell Thickness Varied 

W.E. McMahon, K.E. Emery, D.J. Friedman, L. Ottoson, M.S. Young, 

J.S. Ward, C.M. Kramer, A. Duda, and Sarah Kurtz 

National Renewable Energy Lab 

Bill McMahon 

NREL/MS3212 

1617 Cole Blvd 

Golden, CO 80401 

bill_mcmahon@nrel.gov; Phone: (303) 384-6578 FAX: (303) 384-6430 

 ABSTRACT: 

 To maximize the performance of GaInP2/GaAs tandem cells and GaInP2/GaAs/Ge triplejunction cells, the top GaInP2 cell must be "thinned" slightly to allow some above-band-gap 

photons to pass through to the GaAs cell. Because the terrestrial solar spectrum changes 

throughout the day, different top cell thicknesses (ttops) are optimal for different times of the day. 

This raises two questions: "What ttop is best for my application?" and "How critical is that 

choice?" 

 To help determine the best ttop for a given application, a set of GaInP2/GaAs tandem cells 

with different ttops were mounted on a collimated two-axis tracker for direct comparison outdoors 

over the course of several days. We find that cells designed for Low AOD, "Clear Sky", or AM 

1.5G standard spectra all work quite well. The AM 1.5D spectrum is a poor choice, unless 

maximizing morning and/or evening power production is a priority. Model results support these 

conclusions. 
33

The Development of High Concentrating III-V Photovoltaic Modules at INER Taiwan 

By 

Yen-Chang Tzeng, Chih-Hung Wu, Hwa-Yuh Shin, Hwen-Fen Hong and 

Chieh Cheng 

ABSTRACT 

Concentrating photovoltaic modules are fabricated successfully at INER Taiwan through 

the use of triple-junction solar cell. The module is composed of the Fresnel lens, a secondary 

collimator, a triple-junction solar cell (supplied by Spectrolab Incorporation) and heat sink. 

Photovoltaic characteristics of the module are measured. The output power of the module having 

a 1x1cm2 solar cell is 4.1W with a geometrical concentration ratio 144x when measured at 10:00 

AM outdoors; while an output power of 5.2W can be obtained as the geometrical concentration 

ratio is 245x when measured at 13:40 AM outdoors. Additionally, the characteristics of the 

triple-junction solar cells under various illuminations and temperatures are investigated 

experimentally. Based on the study, a new 100x geometrical concentration ratio solar module is 

also developed. A module efficiency of 19.98% is obtained with the aid of a second collimator. 

An array of 1x9 modules is also developed. A module efficiency of 19.9% for the 1x9 array is 

measured under DNI=778 W/cm2

. In this report, details of the related experimental results are 

also described. 

KEYWORDS: Concentrating photovoltaic module, Triple-junction solar cell, Photovoltaic 

characteristics 
34

Dichroic Flat Faceted Concentrator for PV Use 

Giuliano Martinellia*, Marco Stefancicha , Andrea Antoninia, Alessandro Ronzonia

, 

Maurizio Armania, Paolo Zurrua

a

University of Ferrara & INFM , Via Paradiso 12 Ferrara (FE) 44100, Italy; 

*

Contact Author: 

 Mail Address: University of Ferrara, Department of Physics, via Paradiso 12, 44100, Ferrara 

(Italy) 

 e-mail Address: martinelli@fe.infn.it 

 Tel. : +39 0532 974247/53 

 Fax : +39 0532 974210 

Keywords: Spectral splitting, concentrated solar, photovoltaic, flat mirror, composite dish 

ABSTRACT 

Reflective concentrator systems has been demonstrated offering an interesting approach to cost 

reduction for solar photovoltaic. Still, the efficiency of concentrator system is limited by the 

inherently low efficiency of silicon that does not exceed 24%, even at 250 suns. The use of 

tandem cells is still prohibitive from the point of view of costs and, due to the cell series 

connection, suffers from spectral fluctuations in the earth received solar radiation. 

We present a system which split the solar spectrum in different parts and send each part to the 

most suitable concentrator solar cells module. 

Such a division is obtained, in the presented prototype, at the primary concentrator that employs 

a specifically designed double dichroic mirror generating two illuminated areas providing a cost 

effective solution to the problem. 

The theory, design, numerical simulation and first results of the system installed in Ferrara will 

be presented at this meeting as well as some projection on costs. 
35

Performance of Concentrating Photovoltaic/Thermal Systems Using Solar Cells Immersed 

in Dielectric Liquid

Yiping Wang, Wei Tian, Jianbo Ren, Li Zhu 

School of Chemical Engineering and Technology 

Tianjin University 

Tianjin, 300072, China 

xinxing@tju.edu.cn

ABSTRACT 

Solar cells immersed in a dielectric liquid under certain conditions have an increasing operating 

efficiency. This kind of immersion operation of solar cells is suitable for photovoltaic concentrator and 

hybrid PV/Thermal applications. An experimental apparatus was set up to evaluate the system thermal 

and electric performances. The system consists of parabolic dish concentrator, PV/T module and liquid 

tank. The liquid can provide an effective cooling to the cells through combination of the spectrally 

selective liquid that can absorb unwanted solar radiation from reaching solar cells and the convection heat 

transfer between the liquid and the solar cells. The immersion operation can maintain the working 

temperature of ordinary solar cells under concentrating conditions while the concentration ratio limits to 

20. The system makes full use of the spectrum of solar radiation and improves the overall system 

efficiency. 
36

Representative Samples for 

Concentrator Photovoltiac Module Qualification Testing

Robert McConnell 

National Renewable Energy Laboratory (NREL 

1617 Cole Boulevard, Golden, CO 80401-3393, USA 

e-mail: robert_mcconnell@nrel.gov

Liang Ji and Govindasamy Tamizhmani 

Photovoltaic Testing Laboratory (PTL), Arizona State University East 

7349 E. Unity Ave., Mesa, AZ 85212, USA 

e-mail: l.ji@asu.edu, manit@asu.edu

ABSTRACT: This paper reports the developmental status of a new test standard IEC 62108, 

titled “Concentrator Phhotovoltaic (CPV) Receivers and Modules - Design Qualification and 

Type Approval.” The IEC CPV working group, TC82/ WG7, is currently exploring the 

possibility and validity of using small representative samples in place of large/actual product for 

the design qualification testing. By using appropriately designed and fabricated representative 

smaller samples, the qualification tests can be conducted to considerably reduce the testing costs 

and/or time to the manufacturers, while maintaining a reasonable engineering confidence level 

on the results. In the year 2000, the flat-plate PV module working group, TC82/WG2, developed 

a Retest/Similarity Test Guideline. This guideline has been accepted and adopted by the 

worldwide PV community including the independent testing laboratories. Based on this 

guideline, after the largest type/model from a given flat-plate module family passed a full 

sequence in the qualification test program, other smaller types/models in the same family can be 

fully qualified by running a fewer tests on fewer samples. This larger-representing-smaller 

approach, however, can not be directly applied to CPV, because many CPV systems are in the 

range of several kilowatts, and their sizes are much larger than available test equipment can 

handle, primarily environmental chambers. The intention of TC82/WG7 is to apply the 

“similarity” approach to the CPV qualification but in the reverse order, that is, smallerrepresenting-larger. This paper discusses the potential failure mechanisms under different testing 

sequences, and then gives some suggestions on how to design and fabricate appropriate smaller 

representative samples. This new approach will be discussed within TC82/WG7 for a possible 

incorporation in the IEC 62108 standard, and then submitted for an international voting. 
37

Optimization of High-Concentration Multijunction Solar Cells 

Geoff S. Kinsey, Moran Haddad, Hojun Yoon, Ken Edmondson, Chris M. Fetzer, Richard R. King, and 

Raed A. Sherif

Email: gkinsey@spectrolab.com; Phone: (818) 898-7570

Spectrolab, Inc. 

12500 Gladstone Avenue, Sylmar, CA 91342 USA

A methodology for the design of high-concentration solar cells is presented. The current 

densities present in concentrator multijunction solar cells routinely exceed 1000 mA/cm2. 

At these levels, careful design of the solar cell structure to minimize resistive power 

losses is essential. Increasing the doping in the upper multijunction layers decreases the 

resistivity of the semiconductor and therefore reduces the resistive power loss in the 

semiconductor. However, excessive doping leads to a decrease in blue response (due to 

free carrier absorption) in the top subcell that can offset any reduction in resistive power 

losses. Optimization of these two competing factors will lead to the highest overall cell 

efficiency. This methodology has been applied to several high-efficiency solar cell 

designs. Results from the latest concentrator multijunction solar cell design will be 

presented along with the modeling data. 
38

ENTECH's Stretched Lens Array (SLA) for NASA's Moon/Mars Exploration Missions, 

Including Near-Term Terrestrial Spin-Offs 

Mark J. O’Neill 

ENTECH, Inc. 

1077 Chisolm Trail 

Keller, TX 76248 USA 

Tel: 817-379-0100 

Fax: 817-379-0300 

E-Mail: mjoneill@entechsolar.com

Web Site: www.entechsolar.com

ABSTRACT: Since 1986, ENTECH has been developing photovoltaic concentrator arrays for 

space power. ENTECH’s arrays utilize ultra-light Fresnel lens optics to focus sunlight onto 

multi-junction solar cells. An ENTECH mini-dome lens array (using Boeing cells) on the 

NASA-USAF PASP-Plus flight experiment in 1994-95 demonstrated the best performance and 

durability of 12 advanced array types in a high-radiation orbit. An ENTECH line-focus lens 

array (SCARLET, integrated by ABLE using TECSTAR cells) on NASA’s Deep Space 1 probe 

in 1998-2001 demonstrated exceptional performance in powering both the spacecraft and its ion 

engine for 38 months, enabling rendezvous with both an asteroid (Braille) and a comet 

(Borrelly). Our latest technology, the Stretched Lens Array, offers substantial improvements 

over SCARLET. NASA’s Exploration Systems Mission Directorate recently selected SLA for a 

major Technology Maturation Program. SLA and its many attributes will be discussed in the 

paper, as will potential terrestrial spin-offs from this exciting space technology. 
39

Combining the Tools for Solar Thermal And Photovoltaic Power Generation— 

The Experimental and Computational Facilities at The University of Sydney 

D. Buie, M. Borland, S. G. Bosi, C. J. Dey, N. J. Ekins-Daukes, 

A. G. Imenes, D. Mc

Kenzie, M. Proschek, A. Royne and Y. Yin 

Solar Energy Group, Building A28, School of Physics, 

University of Sydney,NSW 2006, Australia. 

ABSTRACT 

Solar concentrator power generation represents a crossing 

point between the concerns of solar thermal and photovoltaic 

power generation. Problems ranging from the design of solar 

collectors, flux uniformity and heat transfer are common to 

both fields. In particular, the recent interest in hybrid 

concentrator PV/thermal power generation has broadened the 

outlook of both the solar thermal and photovoltaic 

communities. This paper presents the models and test 

facilities designed for thermal systems to concentrator 

photovoltaic or hybrid thermal/photovoltaic systems, with 

particular emphasis on the facilities and the modelling 

capabilities at the University of Sydney. 

1. Assessment and design of solar concentrators 

 The design of solar energy systems is not necessarily 

governed by creating the most efficient configuration to 

convert solar energy into electricity, but in designing a 

system that produces electricity at the lowest cost. Computer 

modelling forms an important aspect of efficient and cost 

effective concentrator design and an array of computational 

tools have been developed at the University of Sydney to 

specifically address these issues. 

 This paper will present the tools that provide a framework 

for identifying optimal optical designs and absorber profiles. 

The models accurately predict the high flux distributions in 3 

dimensions about the absorber plane (Figure 1 – crosssection), which is essential in the determining the 

performance and longevity of absorber modules. In this 

paper, we will illustrate the latest simulations of surfaces 

illuminated with an homogenous distribution, critical for 

concentrating PV applications. 

Figure 5: Simulation of the cross-section of the flux 

passing through the imaging plane of the experimental 

facility at the University of Sydney (The orientation of the 

simulation can be seen in Figure 2). 

 Thermal management of the absorbers forms the operating 

basis for efficient solar thermal collectors and an important 

issue for PV systems. The University of Sydney is applying 

its considerable experience in heat transfer simulation of 

thermal absorbers to the problem of cooling PV under 

concentrated sunlight. 

 In complement to the optical and thermal design, it is 

important to understand and accurately simulate the response 

of a PV device under solar concentration. A model has been 

developed that can simulate both single junction and multijunction concentrator devices from basic semiconductor 

considerations. The model can be scaled from the cell level 

to an entire module. The model is also linked to an outdoor 

concentrator PV test database, allowing realistic simulations 

to be readily performed with rapid comparison against 

experimental results. 

2. Experimental facilities 

 The Solar Energy Group is in the final stages of 

characterising a high flux Fresnel parabolic solar concentrator 

(Figure 2) that will be used as a platform for the experimental 

evaluation of devices and surfaces under realistic conditions. 

The concentrator consists of 18x0.6m diameter circular 

mirrors that can provide tuneable fluxes ranging from 200-

1000 suns uniformly over an area of 10cm2

. 

Figure 2: The high flux solar concentrator at the 

University of Sydney (6 mirror mode). The arrows 

indicate the x and y displacement as seen in Figure 1.

3. Summation 

A complete set of computational tools have been developed 

at the University of Sydney that allow virtually any 

concentrating system to be analysed, in terms its thermal 

and/or photovoltaic power generation. These computational 

tools are backed up by experimental facilities capable of 

fabricating and assessing a range of concentrator devices and 

materials. This paper presents the most recent results in 

experimental and computational modelling of high flux PV 

simulations. 

y
40

The agiceiverTM − a New Approach for Hydrogen Production by Concentrated Sun Light 

Gregor Lengeling 

AGISOLAR 

Dennewartstr. 25/27, D-52068 Aachen, Germany, g.lengeling@agisolar.de, FON/FAX: 

+49(241)963-1625/-1629 

ABSTRACT 

 The agiceiverTM is a special receiver for concentrated sun light. It combines a properly tailored 

semiconductor solar cell and an electrolysis cell on top of which the solar cell is mounted. Efficient 

cooling by the electrolyte allows for high concentration factors. An additional thermo-electric voltage 

contributes to its overall efficiency. The electrode is a metallic conductor rather than a semiconductor. 

First results indicate that the agiceiverTM might be useful for concentrations to 4000X or even above. 

This approach allows omitting all electronic circuits to match the electrical characteristics of the solar 

cell and the electrolysis cell. By directly producing hydrogen rather then providing electrical energy 

this device might contribute to fuel the growing number of hydrogen powered cars in an 

environmentally friendly way. This paper is presented at an early stage of our development. It is rather 

meant to fuel a discussion in the community than to present final results. 
41

Nonimaging Reflective Lens Concentrator 

Sergey Vasylyev 

SVV Technology Innovations, Inc. 

P.O. Box 375, W Sacramento, CA 95691, U.S.A 

vasilyev@svvti.com

Tel: (916) 714-4917; Fax: (530) 686-9935 

A new rear-focus concentrator design is discussed. The concentrator consists of an array of 

relatively narrow reflectors redirecting the incident sunlight downward and thus acting together 

like a non-imaging lens. It is shown that one-stage concentrations between 20 and 40 suns (in a 

linear configuration) and above 1,000 suns (for a point focus design) are achievable for a PV 

receiver positioned below the concentrator. We also demonstrate that the concentrated flux can 

be substantially homogenized without the use of secondary optics although simple secondaries 

can be employed to further increase concentration and improve flux uniformity. A point-focus 

reflective lens can also be used in high-temperature furnaces and water-splitting hydrogen 

production applications to deliver highly concentrated fluxes (>1,000 W/cm2) directly to the 

reactor. Results of prototyping and testing of several linear-focus PV concentrators based on this 

concept are also presented. 
42

Recent Progress of Electrochemical Solar Water Splitting with 

Photoelectrodes and Photocatalysts 

Yoshihiro Nakato 

Division of Chemistry, Graduate School of Engineering Science, Osaka University 

Mailing Address: Toyonaka, Osaka 560-8531, Japan 

Tel: +81-(0)6-6850-6235 

 Fax: +81-(0)6-6850-6236 

 Email Address: nakato@chem.es.osaka-u.ac.jp 

Abstract: 

Solar water splitting into hydrogen and oxygen with a semiconductor/electrolyte junction 

has merits in that (1) inexpensive thin-film semiconductor materials can easily be used, and 

(2) no current collection (and hence no expensive transparent conductive oxide film) is 

necessary, in contrast to thin-film solar cells. The main problem is that it is not easy to find 

efficient and stable semiconductor electrodes or photocatalysts operating in aqueous solutions. In 

the present talk, I will review recent progress of studies on electrochemical solar water splitting, 

though the present achievements are still far from the ideal goal. The talk will include the 

effective stabilization of n-Si by a combination of surface alkylation and metal nano-dot coating 

without any loss in the efficiency, solar water splitting with a composite Si/metal-oxide 

semiconductor electrode, and visible-light responsive metal oxide semiconductors effective for 

water photooxidation or photoreduction. 
43

Hydrogen Electrolysis Using Concentrated Solar Energy 

Robert D. McConnell 

NREL, 1617 Cole Boulevard, Golden, CO 80401-3393, USA 

e-mail: robert_mcconnell@nrel.gov

John B. Lasich 

Solar Systems, 6 Luton Lane, Hawthorn, Victoria 3122, Australia 

e-mail: jlasich@solarsystems.com.au

Jamal R. Thompson and Mohsen Mosleh 

Howard University, 2300 6th St. NW, Washington, DC 20059, USA 

e-mail: mmosleh@howard.edu & jthompson03@hotmail.com

The use of electrolysis to separate hydrogen from water is one of the most energy 

intensive hydrogen production processes. With the majority of the United States’ grid power 

being generated from natural gas and coal fired power plants, the use of grid power in the 

electrolytic production of hydrogen defeats the purpose of developing a hydrogen economy. 

Therefore, the development of efficient, pollution free methods of producing hydrogen are 

essential to the success of the hydrogen economy. Since the feedstock for electrolysis is water, 

there is no pollution in the generation or use of the fuel. Furthermore, it has become evident that 

concentrator photovoltaic (CPV) systems have a number of unique attributes that could shortcut 

the development process and increase the efficiency of hydrogen production to a point where 

economics will then drive the commercial development to mass scale. 

 Concentrating solar energy to produce electricity can occur at quite high solar conversion 

efficiencies. The highest efficiency for solar concentrator cells, as measured at NREL, is now 

above 37%. In production, similar cells have efficiencies above 30% and are currently in 

widespread use for powering satellites. Solar Systems has exhibited a 40% boost in hydrogen 

production by stripping away the solar infrared radiation incident on concentrator solar cells and 

using it as the heat source for a solid oxide electrolyzer cell operating above 1100 Celsius. With 

today’s solar cell technologies, it is therefore feasible to expect a 50% conversion efficiency of 

the solar energy to hydrogen through high temperature electrolysis. 

With gasoline prices constantly increasing, the cost associated with producing hydrogen 

is becoming more and more favorable. At $3.10/kg, the cost of producing hydrogen through 

wind electrolysis is already competitive with that of gasoline. It is expected that hydrogen 

production through thermal-CPV electrolysis will be equally attractive, if not more so. Details of 

a cost analysis for such a hydrogen generation system will be presented. 
44

One Step Method to Produce Hydrogen by Tandem Amorphous Silicon Solar Cells 

H.Song, X. H.Geng, Y Zhao, X. D. Zhang, D. K. Zhang 

(Institute of Photo-Electronics thin film devices and technique of Nankai University, Tianjin, 300071, China) 

(Key Laboratory of photo-electronics thin film devices and technique of Tianjin, Tianjin, 300071, China,) 

(Key Laboratory of Opto-electronic Information Science and Technology, (Nankai University, Tianjin 

University), Ministry of Education, Tianjin, 300071, China)

Abstract 

A new direct one step method to split water into hydrogen and oxygen by using tandem 

amorphous silicon solar cells with p-i-n-p-i-n-p-i-n on glass substrate .The nickel-iron oxide film 

layer as OER catalyst, which is deposited on the surface of SnO2 by DC magnetron reactively 

sputting, and CoMo as HER catalyst is deposited on n-layer of the cell using the same method, as 

shown in figure 1. 

The electrochemical load is represented by: 

V=ηHER+Veq+J•R(KOH)+ηOER 

Where Veq, the decomposition potential for water, is 1.23v; R is the combined resistance of 

the Helmholtz layer , electrolyte and membrane ; ηHER and ηOER are the overpotential at the 

anode and cathode surfaces of the hydrogen and oxygen evolution reaction.

Nickel-iron oxide film electrode, which is as anode of OER, was deposited at room 

temperature by DC magnetron reactively sputtering device at various oxygen content and 

pressure. it was charactered by using XRD, XPS and SEM method, and its electrochemical and 

electric property was measured also. Its property was changed with the processing condition. 

When the current density is 10-20mA/cm2

, its overpotential is about 0.32V, and this film 

electrode has good anticorrosion property in alkaline electrolyte also. 

The XPS spectra of iron-nickel oxide films indicated Ni in the films existed as +2 and +3 

value, and Fe existed as +3 value. 

The CoMo film electrode as the cathode, its overpotential is about 0.1V. And its surface 

morphology is smooth and compact. 

Fig.1 the schematic diagram of photoelectrochemical cell for production 

hydrogen 
45

Considering the electrochemical resistance, the overall voltage of decomposition water is 

about 1.9V-2.0V. When the light incidented on amorphous crystal silicon cell, the single cell 

could produce voltage of 0.7V, through tandem three cells, hydrogen and oxygen can be evolved 

from separated cathode and anode of this system. 
46

Solar Irradiation Potential for PV Concentrator Systems in India 

C. S. Solanki1, P. Pimpalkar2

1

Assistant Professor, Energy Systems Engineering, IIT Bombay, Powai, Mumbai-400076, India 

chetanss@iitb.ac.in, Ph:+91-22-2576 7895, Fax:+91-22-2576 4890 

2

Mechanical Engineering Department, VIT, Pune-411037, India

Assessment of normal beam irradiation is done for application of PV concentrator systems in 

India. In a year, India receives about 3000 to 3200 hours of bright sunshine in central and Northwest India and about 2600 to 2800 hours in most of the other parts of the country. Measured data 

for global and diffused irradiation from 15 meteorological stations are used to calculate annual 

beam irradiance on a plane perpendicular to the sun rays, Hb (kWh/m2

/Year) and annual beam 

irradiation on a one-axis tracked plane, Hb1x (kWh/m2

/Year). Hb and Hb1x is calculated for 60 

points across the country and thus the map of Hb and Hb1x has been plotted. The values of Hb is 

in the range of 1900 to 2300 in central and north-east region and between 1600 to 1900 in most 

of the other parts of the country except far-east and far-north. Relatively low value of normal 

beam irradiation is due to absorption and scattering in the sky during pre-monsoon and monsoon 

period. 
47

PV Concentrator Systems – A Database Search 

C. S. Solanki1, P. Pimpalkar2

1

Assistant Professor, Energy Systems Engineering, IIT Bombay, Powai, Mumbai-400076, India 

chetanss@iitb.ac.in, Ph:+91-22-2576 7895, Fax:+91-22-2576 4890 

2

Mechanical Engineering Department, VIT, Pune-411037, India

PV concentrator (PVC) systems provide lowest cost energy option among all PV technologies. 

Despite this, its contribution in the PV market is insignificant. A database search for PVC 

systems has been done to find out the amount of work done on various topics and to identify the 

areas that require more attention. Electronic database search of INSPEC has revealed the 

development of PVC systems in three phases, of growth, stability and decline. In total 1151 

papers have been published till now, most of them deal with the solar cells. Among 419 papers 

on solar cells, 119 is on Si and 140 in on GaAs and other III-V compounds. In the category of 

concentrator optics, 45 papers are based on Fresnel lens and 37 on static concentrators. 

Surprisingly very less number of papers are published on solar cell cooling. High cell 

temperature not only reduces the cell performance but also reduces the reliability of the system 

and probably requires more attention. 
48

Plastics Structured Optics for Solar Concentrating in PV System 

Carlo Privato* Carmine Cancro, Michele Pellegrino and A. Sarno 

ENEA Centro Ricerche 

Località Granatello I-80055 Portici (NA), Italy. 

e-mail: carlo.privato@portici.enea.it tel: +39-81-7723-273, Fax: +39-81-7723-493; 

* author for correspondence 

The main advantages of using plastic structured optics for concentrating solar beams on a 

receiver of a PV system, instead of the more traditional materials like the glass and the quartz, 

rely on very large mass production, improved structured optics design and manufacturability, 

less weight, high optical quality, low unit cost. 

ENEA in the aim of PhoCUS (Photovoltaic Concentrators to Utility Scale) Project has designed 

and patented a prismatic PMMA (polymethylmethacrylate) optic. Among all the moulding 

technologies, the injection process has been selected to produce this optic. Some critical 

parameters of manufacturing process have been investigated in order to improve the aspect ratios 

and the optical quality of the moulded prismatic lens. 

The resulting samples appear to have a reduced stress, satisfactorily planar surfaces and a little 

radius of curvature for rounded corners, corresponding to a good optical efficiency, major than 

80%. A further improvement will be the deposition of an antireflective hard coating on the 

incoming surface. 

The first production of prismatic lens has been employed to realize the PhoCUS C-module 

prototypes, today under outdoor testing. 
49

Design, Realization and Preliminary Performance Analysis of 

The PhoCUS-5 Standard Unit 

A.Sarnoh,C.Privato 

Enea Portici Research Center Loc.Granatello 80055 Portici (Napoli) - Italy 

hauthor for correspondence - phone +39 081 77 23 202 e-mail: sarno@ portici.enea.it 

The PhoCUS (Photovoltaic Concentrators to Utility Scale) project was launched by ENEA (Italian 

Agency for Energy, Environment and New Twechnologies) in the late 2001 to develop, in close 

cooperation with national industrial operators, a low-cost photovoltaic concentrators technology (Ctechnology). The road-map of the project was outlined to get in medium term a system cost of 4.1 

€/Wp with a production of 5 MW/year. 

One of the main objectives of the PhoCUS is the development, the design and the realization of the 

standard unit. The design criteria of the standard unit have been addressed to develop and optimise 

the most appropriate technologies in order to realize a system able both to work singularly in 

connection with the low voltage grid and to be parallel connected each to other for a centralized 

power generation. The peak power of the standard unit has been fixed at 5 kW in order to meet a 

distributed generation market demand and to limit the PV generator area in such a way as to install it 

on a single medium size tracking structure. 

The innovative components development, like the C-module and the tracking structure, as well as the 

design and the realization of the prototypes, have been performed by two qualified National 

industrial operators, namely ENI TECNOLOGIE ( formerly Eurosolare) and Galileo Avionica 

respectively. In both cases, the design guidelines were addressed to meet the target in terms of cost, 

reliability and performance. 

The novel solution developed for the C-module is a plastic housing, based on thermoplastic resin. 

The lens parquet is fixed on the housing top, while the cells, individually placed on aluminium 

dissipating elements, are fixed on its bottom. Cost, weight, handling, alignment and scalability 

considerations have led us to focus on a 24 commercial (SunPower HECO252) cells assembly (6 x 4) 

of dimensions about 1m x .68 m x .25 m and weight < 30 kg. 

The tracking structure developed is based on a pedestal, supporting on its top a network structure of 

about 35 m^2 where 51 PV modules will be installed. The driving is obtained by means of two 

stepper motors, while the motion transmission is assured by reduction gears properly designed to 

meet the desired stiffness requirements against torsional and bending moment stresses and to 

withstand both the static and dynamic loads. The mechanical carpentry design was performed so as 

to get the lightest structure, able to meet simultaneously both the desired stiffness values and the 

national standard requirements. 

The installation of the standard unit first prototype was started at Portici ENEA Research Center last 

November. At present, the setting up and acceptance phases are in progress. 

The paper will report the lesson learned by the design, realization and installation of the system. The 

results coming from specific experimental campaigns both on single component and on whole system 

will be presented and discussed 

Contact Author: Angelo Sarno 

phone +39 081 7723202 ; fax:+39 081 7723344; e-mail: sarno@ portici.enea.it 

address: ENEA Research Center Portici Località Granatello Portici (NA) 80055 Italy 
50

Research on Graded Optical Band Gap (GBG) In Na-Si:H Solar Cells Prepared 

By PECVD 

Huacong Yua

*, Rongqiang Cui a , He Wang b , Hong Yang b , Zhibin Zhou a, 

Jiangming Gu a

 , Liang Zhao a , Dunyi Tang a , Shuquan Lin a , Fanying Meng a, Yuliang Hec

 

(

a

 Institute of Solar Energy, Shanghai Jiaotong University, Shanghai 200240, China) 

(

b

 Institute of Solar Energy, Xi’an Jiaotong University , Xi’an 710049, China) 

(

c

 Jiangsu Weifu Nanometers Science & Technology Ltd., Wuxi 214028, China) 

Abstract 

The paper report the research on the intrinsic hydrogenated nanoamorphous silicon (na-Si:H) 

layer with the graded band gap (GBG) in p-i-n solar cells prepared by PECVD in varying the processing 

parameters. The optical band gap (Eg

opt) derived from Tauc plot. We have carried out a investigation of 

the relationships between the Eg

opt with the crystallization ratio (Xc) and the Egopt with the nanocrystalline 

grain size (D) in na-Si:H thin films grown by PECVD on glass substrates through XRD, Raman 

scattering, transmission. The Eg

opt increase with the decreases of the crystallization ratio (Xc) and the 

nanocrystalline grain size (D). But with the increase of the DC Bias Voltage. The hydrogen dilution ratio 

is found to increase basically both the crystallization ratio (Xc) and the nanocrystalline grain size (D). 

According the simulated and optimized the band gap figure of solar cells by AMPS-1D, we utilized all 

the relationship to tune the band gap of i na-Si:H layer of p-i-n solar cells prepared by PECVD in varying 

the processing parameters(the DC Bias Voltage and the hydrogen dilution ratio), got the graded band gap 

(GBG) in the i type na-Si:H in p-i-n solar cells, then enhanced this kind of solar cell’s conversion 

efficiency to 11.26% ( solar cell’s active area: 95mm2

, AM1.5,1000W/m2, 25°C). Two relationships in 

na-Si:H are discussed by the etching effect of atomic hydrogen in the framework of the growth 

mechanism and the quantum size effect (QSE) .Because the nanocrystalline silicon speciality, the 

nanoamorphous silicon solar cells is better temperature and irradiation stability, so it can be used in the 

concentration solar cells. This result will improve heat sinking, long-term behavior, cell degradation, and 

reliability, reduced the system cost accordingly. 

Keywords: Graded optical band gap (GBG), Hydrogenated nanoamorphous silicon thin films, 

Nanocrystalline grain, Solar cells, PECVD 

*Corresponding author. Tel.: 0086-21-5474-3243; fax: 0086-21-54745803 

E-mail address: yuhuacong@sjtu.edu.cn and yuhuacong@hotmail.com 
51

Increase Solar Collector Efficiency Through SunTrapTM Technology 

Kemal Koknar and Eric Aylaian 

Radiant Power, LLC 

Email: kkoknar@radiant-power.com

Abstract: 

Radiant Power, LLC (RP) has designed, developed and tested a new solar collection system, which has 

demonstrated the ability to greatly increase the overall efficiency of photovoltaic (PV) modules. 

This process relies on RP’s patented SunTrapTM technology, in which PV cells are arranged such that 

non-absored, incident photons are reflected onto and re-absorbed by additional PVs. The cumulative 

absorption increases the over-all External quantum Efficiency of the system, thereby increasing the 

efficiency. 

The concept is material and system agnostic, having application to virtually any PV cell material or type, 

from 1-sun t high concentration. Recent tests with III-V concentrator cells have demonstrated extremely 

high efficiencies. A description of the SunTrapTM design and results of various tests are presented. 

 
52

Design Principles of Tonatiuh, an Open Source Computer Program for the Design and Analysis of 

Solar Concentrating Systems 

Manuel J. Blanco, Juana M. Amieva, Azael Mancillas 

Department of Engineering 

The University of Texas at Brownsville 

80 Fort Brown 

Brownsville, Texas 78526 

ABSTRACT 

The Tonatiuh project consists of the design, development, 

implementation, verification, and validation of Tonatiuh, 

an open-source advanced object-oriented program, that 

using distributed computing, Monte Carlo ray tracing, and 

the best 3D user interface technologies available today, 

aims to provide a sophisticated and efficient environment 

for the design and analysis of solar concentrating systems. 

The software development effort leading to the 

development of Tonatiuh started just last summer at the 

Department of Engineering of The University of Texas at 

Brownsville under a three-year DOE-NREL Minority 

Research Associate (MURA) Program subcontract. 

Although the first release of Tonatiuh has not been 

concluded yet –it is scheduled for the end of May, 2005- 

Tonatiuh’s leading design principles have already been 

established and are being applied consistently in the 

development of the program. 

This paper describes those principles and discusses their 

implications for the functionality, maintainability, userfriendliness, and scientific relevance of the program. 

General Introduction 

While a myriad of factors will determine to what extent 

solar energy will fulfill its potential to contribute to an 

environmentally benign and sustainable energy future, it 

is clear that the more cost-effective solar technology 

becomes the more chances it will have to fulfill its 

promises. The Tonatiuh project is intended to increase the 

cost-effectiveness of solar energy technologies by 

advancing the state-of-the-art of the simulation tools 

available for the design and analysis of solar 

concentrating systems. 

The objective of the work that is underway at the 

Department of Engineering of The University of Texas at 

Brownsville is the design, development, implementation, 

verification and validation of Tonatiuh, an open-source 

advanced object-oriented program to assist in the design 

and analysis of solar concentrating systems. 

Support for the development of Tonatiuh is being 

provided under a three-year DOE-NREL Minority 

University Research Associate (MURA) Program 

subcontract entitled “Tonatiuh: An object-oriented, 

distributed computing, Monte-Carlo ray tracer for the 

design and simulation of solar concentrating systems”. 

When completed, it is intended that Tonatiuh, will 

(a) provide a unifying computational paradigm for the 

simulation and analysis of virtually any type of solar 

concentrating system that may be envisioned; (b) be 

extremely user-friendly, easy to adapt, expand and 

maintain; and (c) be able to take advantage and efficiently 

handle any computer power available to it. 

Design Principle, Technologies and Tools 

One basic design principle for the development of 

Tonatiuh is to use and leverage available technologies 

whenever possible. Currently, Tonatiuh is being 

developed under Linux, but in an Operating System (OS) 

independent manner. 

The standard Graphic User Interface (GUI) is 

implemented using Trolltech’s Qt, while the 3D GUI is 

implemented using Coin, a C++ 3D graphics library and 

Application Programming Interface (API), which is 

essentially an open-source version of the well-known 

“Open Inventor” 3D toolkit, the industry standard for 3D 

visualization. 

XML is used as the markup language and toolkit for 

Tonatiuh’s inner and outer-process information exchanges 

and objects serialization. 

Software Architecture 

The main architectural decisions adopted so far in the 

development of Tonatiuh are: (a) completely split the 

program into two main components: the kernel and the 

user interface; (b) use a tree-structure to provide semantic 

content through positioning and, therefore, to facilitate the 

externalization of object-state; and (c) establish a clear 

distinction between the roles of container and contained 

C++ classes. 

Both components, the kernel and the user interface, are 

being developed in an OS independent manner using the 

technologies referred to in the previous section. Thus, 

when completed they should be able to run separately 

under the following operating systems: Linux, UNIX, 

Mac OS X, and Windows. 

By decoupling the user interface from the kernel, and by 

using XML as the standard for information exchange and 

object persistence, we are aiming to be able to run the user 

interface and the kernel in separate process environments, 

which may run in different machines, under different OS. 

This will pave the way to incorporating parallel and 

network processing capabilities to Tonatiuh. 
F1147-E(12/2004) 

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4. TITLE AND SUBTITLE

 International Conference on Solar Concentrators for the Generation 

of Electricity or Hydrogen: Book of Abstracts 

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R. McConnell, M. Symko-Davies, and H. Hayden 

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National Renewable Energy Laboratory 

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14. ABSTRACT (Maximum 200 Words)

The International Conference on Solar Concentrators for the Generation of Electricity or Hydrogen provides an 

opportunity to learn about current significant research on solar concentrators for generating electricity or hydrogen. 

The conference will emphasize in-depth technical discussions of recent achievements in technologies that convert 

concentrated solar radiation to electricity or hydrogen, with primary emphasis on photovoltaic (PV) technologies. 

Very high-efficiency solar cells—above 37%—were recently developed, and are now widely used for powering 

satellites. This development demands that we take a fresh look at the potential of solar concentrators for generating 

low-cost electricity or hydrogen. Solar electric concentrators could dramatically overtake other PV technologies in the 

electric utility marketplace because of the low capital cost of concentrator manufacturing facilities and the larger 

module size of concentrators. Concentrating solar energy also has advantages for the solar generation of hydrogen. 

Around the world, researchers and engineers are developing solar concentrator technologies for entry into the 

electricity generation market and several have explored the use of concentrators for hydrogen production. The last 

conference on the subject of solar electric concentrators was held in November of 2003 and proved to be an 

important opportunity for researchers and developers to share new and crucial information that is helping to stimulate 

projects in their countries. 

15. SUBJECT TERMS

PV; solar concentrators; electricity; hydrogen; solar radiation; solar cells; high-efficiency; research and development; 

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