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Solar Photovoltaic Technologies & Operation. Chris Lombardo CHE 384 November 20, 2006. Basic Operation. Solar cells are physically made of p-n junctions Photons of greater then E g liberate charge which travels out of solar cell For Si: 1.1 eV or 1129 nm, 15% efficient
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Solar Photovoltaic Technologies & Operation Chris Lombardo CHE 384 November 20, 2006
Basic Operation • Solar cells are physically made of p-n junctions • Photons of greater then Eg liberate charge which travels out of solar cell • For Si: 1.1 eV or 1129 nm, 15% efficient • Excess energy goes to heating Band diagram of a p-n junction1
Solar Spectrum Solar Spectrum outside and within Earth’s atmosphere2
Bulk Heterojunction Device • Tunable band structure and junction energies • Made out of exotic compound semiconductors • Very expensive • Up to 35% efficient = 575 nm = 661 nm = 776 nm = 884 nm = 1053 nm = 1880 nm Bulk Heterojunction PV Structure3
Solar Spectrum Solar Spectrum outside and within Earth’s atmosphere2
Thin Film Devices • Lower efficiency but lower cost • Amorphous Si, CdTe, CIGS, organic/polymer, and other materials • Cheap to manufacture because many can be put on flexible substrates or glass • Use only 1% material used when compared to bulk devices • Technologically very young
Efficiency Now and Then Current PV Module Efficiency4 Future PV Module Efficiency4
Improving Efficiency • 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 • Increase energy output from 22%-100% Solar Tracking throughout the Day5 Morning top-left, Evening bottom-right
References • http://www.nano.physik.uni-muenchen.de/elektronik/E1/8Optoelektronik/Bilder/pn-junction.gif • http://en.wikipedia.org/wiki/Image:MODIS_ATM_solar_irradiance.jpg • Miles R., Progress in Crystal Growth and Characterization of Materials, (51), p. 1, 2005 • http://www.heliovolt.com • http://www.zomeworks.com/solar/trackrack/trackwork.html • http://www.solar-power-answers.co.uk/inverter_system.html