PV: The Path from Niche to Mainstream Source of Clean Energy

1. PV: The Path from Niche to Mainstream Source of Clean Energy Dick Swanson

2. Outline • History of PV • Satellites to Mainstream (almost) • PV Market Dynamics • Growing fast • PV Applications • Grid-connected distributed generation • How Solar Cells Work • It’s simple

3. The 1970s oil crises sparked interest in PV as a terrestrial power source I can’t believe he said that. Don’t worry Mr. President, solar will be economical in 5 years! Sun Day, May 5, 1978, SERI

4. Solar Cell Solar Module Systems Polysilicon Wafer Ingot $300/kg 3 inches in diameter Sawn one at a time 0.5 watts each $100/watt $200/watt Situation in 1975 Wafered Silicon Process

5. 1975 View Wafered Silicon Hopelessly Too Expensive Breakthrough Needed Concentrators Thin Films Solar Farms Remote Habitation

6. What Actually Happened Wafered Silicon Emerges as the Dominant Technology Breakthrough Needed DOE Wafered Silicon Program Concentrators Thin Films Residential/ Commercial Grid connected Solar Farms Remote Habitation

7. PV Market Growth 95% Wafered Silicon

8. Historical PV Landscape

9. Historical PV Landscape

10. Market Share Trends

11. Recent Industry Milestones • 1999 1 GW accumulated module production • 2001 More square inches of silicon used than in entire microelectronics industry • 2004 1 GW production during year • 2006 More tons of silicon used than in microelectronics

12. History of SunPower • Founded in 1985-9 to commercialize technology developed at Stanford • Utility-scale solar dish application • High performance required • All-back-contact cell developed • NASA & Honda early customers • Great technology, high cost • Merged with Cypress Semiconductor in 2001 • Went public in 2005

13. SunPower Growth 2007 forecast non-GAAP net income as presented in Q4 conference call

14. Distributed Generation Strategies are Shaping the Future

15. PV Applications Residential Retrofit Power Plants New Production Homes Commercial & Public

16. 1500 Surprise Geothermal Solar 1000 Biomass Exajoules Wind Nuclear 500 Hydro Gas Oil &NGL Coal Trad. Bio. 0 1860 1880 1900 1920 1940 1960 1980 2000 2020 2040 2060 Source: Shell, The Evolution of the World’s Energy Systems, 1995 Shell Sustained Growth Scenario • Renewable Energy Drivers: • Climate Change • Fossil Fuel Depletion • Energy Security

17. Value Chain Cost Distribution Polysilicon Ingot Wafer Solar Cell Solar Panel System Polysilicon 2006 US Solar System Cost Allocation by Category 50% 30% 20%

18. 50%+ cost reduction from CA system cost is achievable

19. SAMPLE APPLICATIONS

20. Systems Business Segment Commercial Roofs New Production Homes Commercial Ground Power Plants

21. Santa Barbara, California – 12.6 kW

22. Walldürn, Germany – 8.0 kW

23. Osaka, Japan – 5 kW

24. Walnut Creek, CA

25. New York City – 27 kW

26. Los Altos Hills, California – 35 kW

27. Market Opportunity for PV Roof Tiles • Product enables homeowner to integrate PV into the roof of the building: • Lower profile than traditional modules means better aesthetics • Potential cost savings over traditional PV system • Traditionally targeted at new home construction PowerLight SunTileTM

28. New York City – 27 kW

29. Microsoft Silicon Valley Campus

30. Arnstein, Germany – 12 MW

32. Factory Assembled Unitary Product Reduces CostTracking improves Energy Delivery 15 MW Plant Nellis AFB

33. Television for 1st Time

34. The Terrawatt Future • Advanced Crystalline? • Thin film? • Concentrating PV? Energy from the Desert, Kosuke Kurokawa, ed., James & James, London, 2003.

35. How Solar Cells Work

36. The Hydropower Analogy to PV Conversion Energy as light H2O

37. Solar Cell Operation Light Electron Collection e Electron-Hole Production h Hole Collection

38. Solar Cell Operation Step 1: Create electron at higher energy Conduction Band Bandgap Valence Band Thermalization loss

39. Solar Cell Operation Step 2: Transfer electron to wire at high energy (voltage/electrochemical potential/Fermi level) Collection loss Thermalization loss

40. Step 3: Deliver Energy to the External Circuit

41. Recombination Loss • Any outcome of the freed electron and hole other than collection at the proper lead is a loss called “recombination loss.” • This loss can occur in several ways

42. Bulk Recombination Loss A) Radiative recombination

43. Bulk Recombination Loss B) Defect mediated recombination (SRH recombination) Defect related mid-gap energy level

44. Surface and Contact Recombination Loss

45. Cell Current

46. Cell Voltage

47. Generic Solar Cell Loss Mechanisms Reflection Loss I2R Loss 1.8% 0.4% 0.4% 0.3% Recombination Losses 1.54% 3.8% 2.0% Back Light Absorption 1.4% 2.6%

48. Lightly doped front diffusion • Reduces recombination • loss Texture + Oxide Texture + SiO2 + ARC Texture • N-type FZ Silicon – 240 um thick • reduces bulk recombination P+ N+ P+ N+ P+ N+ • BacksideGridlines • Eliminates shadowing • Thick, high-coverage • metal reduces resistance loss • Localized Contacts • Reduces contact • recombination loss N-type Silicon – 270 um thick SunPower’s Backside Contact Cell • Backside Mirror • Reduces back • light absorption • Causes light trapping • Passivating • SiO2 layer • Reduces top • and bottom recombination loss

49. Texture + Oxide N-type Silicon – 270 um thick SunPower Cell Loss Mechanisms 0.8% 0.5% Texture 1.0% 0.2% 0.2% 0.2% 0.3% 1.0% I2R Loss 0.1%