1. Solar Photovoltaic Technologies & Operation Chris Lombardo CHE 384 November 20, 2006

2. Basic Operation Solar cells are physically made of p-n junctions Solar cells are physically made of p-n junctions Photons of greater then E g liberate charge which travels out of solar cell Photons of greater then E g liberate charge which travels out of solar cell For Si: 1.1 eV or 1129 nm, 15% efficient For Si: 1.1 eV or 1129 nm, 15% efficient Excess energy goes to heating Excess energy goes to heating Band diagram of a p-n junction 1

3. Solar Spectrum Solar Spectrum outside and within Earth’s atmosphere 2

4. Bulk Heterojunction Device Tunable band structure and junction energies Tunable band structure and junction energies Made out of exotic compound semiconductors Made out of exotic compound semiconductors Very expensive Very expensive Up to 35% efficient Up to 35% efficient Bulk Heterojunction PV Structure 3 = 575 nm = 661 nm = 776 nm = 884 nm = 1053 nm = 1880 nm

5. Solar Spectrum Solar Spectrum outside and within Earth’s atmosphere 2

6. Thin Film Devices Lower efficiency but lower cost Lower efficiency but lower cost Amorphous Si, CdTe, CIGS, organic/polymer, and other materials Amorphous Si, CdTe, CIGS, organic/polymer, and other materials Cheap to manufacture because many can be put on flexible substrates or glass Cheap to manufacture because many can be put on flexible substrates or glass Use only 1% material used when compared to bulk devices Use only 1% material used when compared to bulk devices Technologically very young Technologically very young

7. Heliovolt FASST Process 4

8. Efficiency Now and Then Current PV Module Efficiency 4 Future PV Module Efficiency 4

9. Improving Efficiency Concentration – using lenses and mirrors to focus sunlight in a small area Concentration – using lenses and mirrors to focus sunlight in a small area Tracking – using an passive or active means to follow the sun through the sky Tracking – using an passive or active means to follow the sun through the sky Increase energy output from 22%-100% Increase energy output from 22%-100% Solar Tracking throughout the Day 5 Morning top-left, Evening bottom-right

10. PV System Wiring Diagram 6

11. Questions?

12. References 1. http://www.nano.physik.uni- muenchen.de/elektronik/E1/8Optoelektronik/Bilder/pn- junction.gif http://www.nano.physik.uni- muenchen.de/elektronik/E1/8Optoelektronik/Bilder/pn- junction.gif http://www.nano.physik.uni- muenchen.de/elektronik/E1/8Optoelektronik/Bilder/pn- junction.gif 2. http://en.wikipedia.org/wiki/Image:MODIS_ATM_solar_irra diance.jpg http://en.wikipedia.org/wiki/Image:MODIS_ATM_solar_irra diance.jpg http://en.wikipedia.org/wiki/Image:MODIS_ATM_solar_irra diance.jpg 3. Miles R., Progress in Crystal Growth and Characterization of Materials, (51), p. 1, 2005 4. http://www.heliovolt.com http://www.heliovolt.com 5. http://www.zomeworks.com/solar/trackrack/trackwork.html http://www.zomeworks.com/solar/trackrack/trackwork.html 6. http://www.solar-power-answers.co.uk/inverter_system.html http://www.solar-power-answers.co.uk/inverter_system.html