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

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

3. Sun Day, May 5, 1978, SERI I can’t believe he said that.
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. Situation in 1975 Wafered Silicon Process $300/kg 3 inches in diameter
Polysilicon
Wafer
Solar Cell
Solar Module
Systems
Ingot
$300/kg
3 inches in diameter
Sawn one at a time
0.5 watts each
$100/watt
$200/watt

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

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

7. PV Market Growth
95% Wafered Silicon

8. Historical PV Landscape
Era
Main Players
Characteristics
Small Start-ups
Solar Technology
International → ARCO
Solar Power Corp. → Exxon
Solarex → BP
Tyco → Mobile
Rapid Growth
Development of
technology
paradigm
Oil Companies
ARCO
Exxon BP
Mobile
Shell
Moderate growth
Search for market
Massive losses
Few start-ups

9. Historical PV Landscape
Era
Main Players
Characteristics
Japanese Companies
Sharp
Sanyo
Kyocera
Emergence of
residential roof
market
Improved
manufacturing
2000 -
Entrepreneurial Co’s
Q-Cells (Germany)
Scanwafer (Norway)
Solar World (Germany)
Evergreen (US)
SunPower (US)
Suntech (China)
MiaSole (US)
Explosive growth
Profitability
Technology
evolution

10. Market Share Trends

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

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

17. Value Chain Cost Distribution
Polysilicon
Polysilicon
Ingot
Wafer
Solar Cell
Solar Panel
System
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 Cost Tracking 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. Step 1: Create electron at higher energy
Solar Cell Operation
Step 1: Create electron at higher energy
Conduction Band
Bandgap
Valence Band
Thermalization loss

39. Step 2: Transfer electron to wire at high energy
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
1.8%
I2R Loss
0.4%
0.4%
0.3%
Recombination
Losses
1.54%
3.8%
2.0%
1.4%
Back Light
Absorption
2.6%
Limit Cell Efficiency
29.0%
Total Losses
-14.3%
Generic Cell Efficiency
14.7%

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

49. SunPower Cell Loss Mechanisms
Texture + Oxide
0.5%
0.8%
Texture
N-type Silicon – 270 um thick
1.0%
0.2%
0.2%
0.2%
0.3%
1.0%
I2R Loss
0.1%
Limit Cell Efficiency
29.0%
Total Losses
-4.4%
Enabled Cell Efficiency
24.6%