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Eng/Phys. 160, 5/17/07

Eng/Phys. 160, 5/17/07. Photovoltaics – more basics  Insulators, metals, conductors  Photovoltaic effect  Need for an np junction (conventional)  Efficiency  Alternatives to silicon - organic PVs, Gratzel cells  New ideas - carrier multiplication + hot electrons

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Eng/Phys. 160, 5/17/07

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  1. Eng/Phys. 160, 5/17/07 • Photovoltaics – more basics  Insulators, metals, conductors  Photovoltaic effect  Need for an np junction (conventional)  Efficiency  Alternatives to silicon - organic PVs, Gratzel cells  New ideas - carrier multiplication + hot electrons • Photovoltaics – growth of usage • Wind Power – --> Basics – theoretical efficiency max, wind energy density, places of high density --> Growth of usage --> Cost --> Drawbacks (visual, noise pollution, longevity, raptor deaths) • Hydroelectric --> Basics --> Limits to large scale hydro --> Problems with large scale hydro (earthquakes, displacement, increased greenhouse effect, risks of catastrophic flooding, silting out of dams..)

  2. Gratzel dye and chlorophyll

  3. Gratzel Cell: mimic photosynthesis

  4. Beat the limit with nanostructures • Nanostructures have intrinsically multiple bands from ``quantum confinement’’ • Can increase the open circuit voltage by inhibiting carrier relaxation (emission of ``phonons’’) • Can increase the current by increasing number of particle hole pairs induced per photon (Klimov, Los Alamos)

  5. Typical efficiencies of current photovoltaics

  6. Photovoltaic growth • Upper left: world growth of sales • Lower left: Growth of installed capacity in Japan • Lower right: growth of installed capacity worldwide

  7. Photovoltaic Costs

  8. Wind energy

  9. Maximum wind efficiency--on blackboard. Neat result.

  10. Wind-where is it?

  11. Wind energy growth

  12. Wind energy costs

  13. Dams – Hoover, Grand Coulee, Three Gorges

  14. Where's left for dams?

  15. Image credits • Data from Japan: www.poweringtherim.org/casestudies/egill.html • PV Growth, MW: www.votesolar.org/whysolar.html • PV Growth, Sales: www.heliovolt.com/market.php • PV Costs, efficiency charts: www.eere.energy.gov/.../solar_power_from_pv.html • Wind energy growth: www.ecotopia.com • Wind energy development: blackhawkfund.com • Wind cost: http://www.eere.energy.gov/tribalenergy/guide/images/chart2_wind.gif • Where there's wind map: www.nrel.gov/wind/wind_map.html • Hoover Dam: http://www.nuc.berkeley.edu/courses/classes/E-124/hoover%20dam_1.jpg • Grand Coulee Dam:www.nwcouncil.org, www.grandcouleedam.com • Three Gorges Dam: http://www.tourroundchina.com/news/three_gorges_dam_to_open_to_visitors.htm • Hydro potential: nationalatlas.gov/articles/people/a_energy.html

  16. Image credits • Working Gratzel Cell: http://www.bath.ac.uk/physics/news/gratzel.jpg • Gratzel schematic (liquid electrolyte): http://www.bath.ac.uk/chemistry/electrochemistry/images/mechanism_small.jpg • Gratzel schematic (polymer electrolyte): http://www.rsc.org/ejga/CC/2005/b416461j-ga.gif • Polymer photovoltaic photo: http://www.polymercentre.org.uk/industry/pics/03photovoltaic.jpg • Alan Heeger: http://www.konarkatech.com/images/heeger.jpg • Konarka Power plastic: http://energypriorities.com/graphs/konarka-power-plastic.jpg • Chlorophyl: http://amanda.berkeley.edu/~bramall/work/astrobiology/images/chlorophyll.jpg • PV schematic: http://www.speedace.info/speedace_images/solar_cell_schematic.jpg • Met/ins/semic schematic: http://www.physics.udel.edu/~watson/scen103/semi1.gif

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