The generation of electricity from solar energy is efficient and comparatively abundant when nature collects the energy from enormous areas and man taps what nature has concentrated; this is the case for hydropower (the sun lifts the water and gravity collects it into a reservoir), or Ocean Thermal Energy Conversion.
When man tries to do the collecting himself, the harvest is poor and expensive; but there are nevertheless cases when the price is worth paying. One way of converting man-collected solar energy into electricity is to use a thermal plant, which simply focuses the sun's rays into a boiler to produce steam¾in essence, solar heat is used in place of nuclear or fossil-fired heat. It is actually the solar radiation that is being focused, and only upon absorption by the target medium is the light converted to heat.
But it is also possible to convert sunlight to electricity directly in photovoltaic collectors. The heat produced here represents no more than an undesirable energy loss: It is produced from light that failed to be converted to electricity. (The other type of loss is the light that filters through the collectors without being changed to heat or electricity.)
The second type works at low temperature and, at present, is less efficient as well as more expensive. But what both methods have in common is, above all, the enormous collecting area needed for a given capacity. While 1000 MW of fossil-fired or nuclear power can be produced by a plant taking up 25 acres, a solar plant necds some 50 square miles for 1,000 MW of electric power. (Some readers doubted this in the past, so here are the figures: "1000 MW capacity" means that 1,000 MW can be put on line whenever needed, even when the sun is not out. To tide the plant over cloudy days and over nights, its storage capacity must be able to be replenished at several--6 or 7-- times the rate at which it is drained by the load; thus, 1000 MW capacity requires at least 6,000 MW peak power. Assume solar energy coming in at the possible maximum of 1 kW/M2, 50% spacing, 10% efficiency, and a pocket calculator will do the rest. The power/area ratio is also confirmed by a solar thermal plant near Albuquerque, N.M., and a planned photovoltaic plant in California.)
The cost in energy to produce the necessary materials is about 1,000 times higher than for conventional power plants of equal capacity, and the dollar cost is, as yet, staggering: The price of photovoltaic cells is now about $10 per peak watt (but falling). Thus, to toast 4 slices of bread in a 1 kW toaster by "free" electricity, one would have to invest $10,000, and even that goes only for cloudless days when the sun's rays are perpendicular to the collector plane. Most utilities charge about 0.1 cents for toasting the four slices, and that includes all the financial, technical, and other headaches they have with the generating equipment. No wonder people will not switch to solar beyond sporting "Switch to Solar" bumperstickers on their gasoline-driven cars.
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Vol. 7, No. 7
Newsletter: Access to Energy Newsletter Archive Volume: Volume 7 Issue/No.: Vol. 7, No. 7 Date: March 01, 1980 03:17 PM (For actual publication date see newsletter.) Title: Berrigan's Law
Copyright © 2004 - Access to Energy Newsletter Archive
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