Albedo of solar cells

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Solar photovoltaic cells produce electricity without producing carbon dioxide (aside from the embedded energy in their manufacture).

Photovoltaic panels also produce localized heat when the sun strikes them, as does any object. If the solar panel is darker (lower albedo) than the object (roof or ground) that it covers, then more heat is absorbed and released than otherwise would be.

Does this matter? No! Even for a near-black solar panel over a white surface, the amount of heat produced in this way is tiny compared with the long-term impact of preventing carbon dioxide release in energy production. Each molecule of CO2, during its time in the atmosphere, traps approximately 100,000 times more heat than was released in the reaction that formed it. Any heating due to the color of the solar panels is smaller than a rounding error.[verification needed]

Contents

[edit] Calculation

[edit] Heat released by the panel

Assume a pure black solar panel.[1]

Assume 14% efficiency. Then for each kWh of electric energy generated, total energy that falls on the panel must be 7 kWh (100%/14% * 1 kWh = 7 kWh). Of this 7 kWh, 1kWh becomes electricity, and the remaining 6kWh are radiated as heat.

[edit] Heat avoided by the panel

Assuming the solar power is replacing US grid power, each kWh generated avoids the release of approximately 1.52 lb (690 g) of CO2 [2]. During its time in the atmosphere, this amount of CO2 would have absorbed approximately 210,000 kWh of heat.[verification needed]

[edit] Net effect

The benefit in avoided heating of the atmosphere by using solar photovoltaic power (assuming US grid power or similar as the alternative) is approximately 209,994 kWh of heat (210,000-6) for every 1 kWh of electricity produced.[verification needed]

[edit] Sources

[edit] Footnotes

  1. Actually many solar panels are blue and somewhat reflective, possibly having a higher albedo than the roof or ground that it covers. However, this doesn't actually matter in the context of the vastly larger amount of trapped heat avoided by not releasing CO2.
  2. 6.8956 x 10-4 metric tons CO2 / kWh, from EPA eGRID2010 Version 1.1, U.S. annual non-baseload, 2007 data, does not include line losses.

[edit] See also



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