1. SOLAR CELLS ESW Sustainable Technology of the Month! Presented by: Brad Gething

2. DISCLAIMER I am not an expert in photovoltaics  This presentation is not a comprehensive review of the state of the art. Not all of the information presented originates from peer reviewed sources.

3. BACKGROUND 1839 - Photovoltaic effect was discovered by the French physicist Alexandre Edmond Becquerel. 1918 - Polish scientist Jan Czochralski discovered a method for monocrystalline silicon production. The first silicon monocrystalline solar cell was constructed in 1941. 1955 - Western Electric put for sale commercial licenses for solar cells production (mainly for space exploration). Hoffman Electronics- Semiconductor Division introduced a commercial photovoltaic product with 2 % efficiency for $25 per cell with 14 mW peak power. Cost - $1,785 per W. 1973 – U. Delaware produced a photovoltaic-thermal hybrid system Solar one, one of the first photovoltaic systems for domestic application. Cost - $30 per W 1984 - 1 MW photovoltaic power plant began to operate in Sacramento, California. ARCO Solar introduced the first amorphous modules. 1992 - A silicon solar cell with 20 % efficiency was patented. 2002 - Cumulative worldwide installed PV capacity expected to reach 2000 MW

4. AVERAGE SOLAR IRRADIANCE 1991-1993 W/m 2 World Energy Demand GW-hr2003 2030 (est.) 1.233 E 8 2.116 E 8 US Energy Demand GW-hr 2003 2030 (est.) 2.937 E 7 3.844 E 7 CONTEXT

5. CONTEXT Location, Desert Desert Size km 2 Irradiation W/m 2 Area Required km 2 Energy Output GW-hr Africa, Sahara 9,064,960260144,231 2.055 E 7 Australia, Great Sandy 388,500265141,509 China, Takla Makan 271,950210178,571 Middle-East, Arabian 2,589,910270138,889 South America, Atacama 139,860275136,364 U.S.A., Great Basin 492,100220170,455

7. HOW THEY WORK 1 Si-P Si-B 3 Si-P Si-B 2 Si-P Si-B

8. ECONOMICS A 3 kW PV residential retrofit system in the US costs ~$25,000 Amortized over a 20 year mortgage, the cost of PV electricity is ~25 cents per kWh in most U.S. locations The average cost of utility/grid electricity is 8.2 cents per kWh in the U.S. and between 0.10 and 0.15 €per kWh in Europe. Studies suggest an added hidden societal cost behind all fossil-fueled power plant ranging from 7 to 20 cents per kWh.

9. ECONOMICS Although the production of electrical grade Si has increased, acquisition of raw Si has not. DEMAND > SUPPLY

10. ECONOMICS

11. KEY POINT Costs can be reduced by: Alternative materials Alternative materials Reduced material cost Reduced material cost Reduced processing cost Reduced processing cost Increased efficiencies Increased efficiencies Alternative uses of Si Alternative uses of Si Amorphous Si (non-crystalline) Amorphous Si (non-crystalline) Si layered with glass Si layered with glass

12. ALTERNATIVES Materials Cadmium Telluride Cadmium Telluride Polymers Polymers Dye-sensitized solar cells Dye-sensitized solar cellsProcessing Thin films Thin films Ribbon Printing Ribbon Printing Nano-crystalline materials Nano-crystalline materials

13. EFFICIENCIES Amorphous silicon (Tandem) 6 - 7% Cadmium Telluride (CdTe) thin film 8 - 10% Multi (or Poly) crystalline silicon12 -15% Mono-crystalline silicon (SiN)13 -16% Saturn Mono-crystalline silicon15 -18%

14. WANT TO LEARN MORE? PSU Courses EDSGN 497A: Sustainable Design and Engineering EDSGN 497A: Sustainable Design and Engineering ENGR 097S: Solar Racers ENGR 097S: Solar Racers Center for Sustainability (www.engr.psu.edu/cfs) Solar Decathlon Solar Decathlonwww.solar.psu.edu Powerlion- portable PV station Powerlion- portable PV station New 1750 W PV array New 1750 W PV array Penn State Energy Institute – Sustainable Energy Research Faculty Dr. Andy Lau – ASE Dr. Andy Lau – ASE Dr. Christopher Wronski – EE Dr. Christopher Wronski – EE Dr. John Asbury - Chemistry Dr. John Asbury - Chemistry

15. REFERENCES http://www.pvresources.com/en/history.php http://en.wikipedia.org/wiki/Photovoltaics http://science.howstuffworks.com/solar-cell.htm “Everything You Wanted to Know About Solar PhotovoltaicsBut Were Afraid to Ask”, BP Solar Publication International Energy Outlook 2006, Energy Information Administration Annual Energy Outlook 2007, Energy Information Administration Flin, David. “Thin films for fat profits”, Modern Power Systems, 26(2), 2006.

16. LET’S CHAT! QUESTIONS?? COMMENTS?? “I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait till oil and coal run out before we tackle that.” --Thomas Edison “If to do were as easy as to know what is good to do, then paupers would be princes and a poor man’s hovel, a rich man’s estate.” – William Shakespeare