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Solar Technology

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  1. In 2008 Solar Technology Daniel Ayoub The University of Texas at Austin Department of Chemical Engineering

  2. Introduction • Photovoltaic Cells • Derived from Greek Language: φώς “Phos” meaning light, and “voltaic” meaning electric Brittanica

  3. Introduction • First discovered in 1839 by French physicist A.E. Becquerel. • First “solar cell” build in 1883 by Charles Fritts with gold on selenium. Produced a current. • But why did this work?

  4. Light • Initially Maxwell’s wave theory of light predicted energy would be proportional to light intensity • Einstein described light as composed of discrete quanta – photons. • E=hν

  5. Light • A photon above a certain threshold frequency (energy) is able to eject a single electron. • = The Photovoltaic Effect

  6. Light • 1921 Albert Einstein Nobel Prize in Physics • Quantum Revolution

  7. Solar Cells – General Source: How stuff works

  8. Solar Cells – P-n Junction What is a p-n junction?

  9. Materials – P-type • Addition of trivalent impurities usually from group IIIA. • “Hole”-rich material • Boron, Aluminum, Gallium, etc.. • E.g.: Diffuse B2H6 gas into silicon Source: Hyperphysics

  10. Materials – N-type • Addition of pentavalent impurities usually from group 5A. • “Electron”-rich material • Phosphorus, Arsenic, Antimony, etc.. • E.g.: Diffuse PH3 gas into silicon Source: Hyperphysics

  11. Solar Cells – Band Gap • △E between Valance band and Conduction band • Available carriers only in conduction band Source: Wikipedia

  12. Materials – P-n Junction • Carrier Diffusion • Depletion Region at interface • E-Field Source: Wikipedia

  13. Solar Cells • Photons above band gap energy create free electron-hole pairs. • E-Field will send free electron from P to N side

  14. Solar Cells • Disrupts electrical neutrality • Collect electrons. Pass through external circuit to do work. • Recombine with respective holes back in P-type

  15. Solar Cells – General Source: How stuff works

  16. Solar Cells Today First Generation • Single Junction • Expensive • Theoretical max efficiency 33% (average 15%) • $1/Watt

  17. Solar Cells Today Second Generation (Now) • Alternative manufacturing techniques • Thin-Films • CVD • Electroplating • Defects reduce efficiency=>Use Multi-layer • CdTe, CIGS, etc • Typical layer efficiency of 7-10% • Replace 80cents of Si with 1 cent of thin-film material

  18. Solar Cells – HelioVolt (Austin, TX) • FASST Process = cheaper • 10-14% power conversion efficiency

  19. Solar Cells – Power Generation

  20. Solar Cells – Power Generation

  21. Solar Cells – Cool Stuff • Solyndra • Cylindrical Tubes • Thin-film CIGS coating • Paint roof white • Collect 20% more light • 2x energy density claim • Low installation cost(1/2) Source: Scientific American

  22. Solar Cells – The Future Third Generation Solar Cells • Current Research targeting 30-60% efficiencies! • July 2007, U Delaware set 42.8% efficiency record (1994 previous record of 24.7%) • Exploit other frequencies of light • Multi-junction cells • Cheaper manufacturing processes

  23. References • Hyperphyisics “The Doping of Semiconductors” http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/dope.html Retrieved Nov. 10th, 2008. •Wikipedia. “Solar Cell”. http://en.wikipedia.org/wiki/Solar_cells/. Retrieved Nov. 10, 2008 •Scott Aldous, How Stuff Works. “How Solar Cells Work”. http://science.howstuffworks.com/solar-cell4.htm. Retrieved Nov. 10, 2008. • David Biello, Scientific American. “Cylindrical Solar Cells Give a Whole New Meaning to Sunroof” http://www.sciam.com/article.cfm?id=cylindrical-solar-cells-give-new-meaning-to-sunroof • Carl Gutierrez, Forbes Magazine, Market Scan, “First Solar Goes Supernova” November, 2008 • Ed. P. Capper, “Properties of Narrow-Gap Cadmium-Based Compounds” INSPEC, IEE, London, UK, 1994. • Kim J et al. “Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Processing.” Science, 2008. • Antonio Luque and Steven Hegedus. “Handbook of Photovoltaic Science and Engineering.” John Wiley and Sons. 2003 • M.A. Green et al. “Crystalline Silicon Thin-Film Solar cell Modules.” Solar Energy, 2004. • Fthenakis, “Renewable & Sustainable Energy Reviews," Vol. 8, 2004 • V M “Life Cycle Impact Analysis of Cadmium in CdTe PV Production” pp 303 – 334, • “Plastics: Background Information for Teachers.” American Plastics Council, 2006. • Stefan Lovgren, National Geographic News, “Spray-On Solar-Power Cells Are True Breakthrough” January, 2005. • "New Ways to Catch Rays" NOVA Website, November, 2008. • Steven Latham "Saved by the Sun", NOVA on PBS. Courtesy of SCHOTT. April 2007. • Kevin Bullis, “Making Cheaper Solar Cells” MIT Technology Review, September 12, 2008. • Peter Fairley, “Fixing the Power Grid” MIT Technology Review, October 17, 2007. • Reuters on 2007 “Abu Dhabi to build $350m solar power plant” • Reuters on 2007 “Egypt invests $109mn in solar power”