Lect17 -- Solar

Depends on fraction reflected for heating depends on

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Unformatted text preview: e effect is I/Io = cos(φ), and φ = latitude) How much can we use? •  depends on fraction reflected •  for heating, depends on heat loss from absorbing surface (by evaporation, conduction, radiation) •  for photovoltaic cells, need correct wavelengths The seasons Summer in northern hemisphere Winter in northern hemisphere •  Earth orbit is elliptical (varies from 0.98 to 1.02 A.U.) •  Axis tilted to ecliptic by 23.5° So location of solar input changes during year: In LA, changes from effective latitude of 9° to 58° --> 0.99*(435) to 0.85*(435) watts/m2 during year Elliptical effects change factors to about 0.96 to 0.88 Uneven energy input across globe drives wind, ocean Earth’s climate bands Uneven heating of Earth’s surface drives atmosphere, ocean circulation Potential solar radiation How can we harness solar energy? 1.  Capture and use for solar energy for heating •  Solar panel heaters for homes (usually small scale) •  Concentrating solar power (typically for larger plants) 2.  Use for Photovoltaic (PV) Solar Cells to generate elec...
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