A Thin Film Can Wringenergy From The Sun

Jacques E. Ludman, president of Northeast Photosciences Inc. in Hollis, N.H., wasn't looking for cheap solar energy. His goal was to lighten the load of solar-power systems in space. The secret to efficient solar power is well-known: Focus the sun's rays and split them up into beams of individual colors, so that each beam hits a solar cell engineered for that particular wavelength. But the standard method--with prisms and lenses--is too heavy for pound-conscious spacecraft.

So Ludman found a lightweight solution: a thin holographic film that uses diffraction to split and focus sunlight. Unfortunately, the demise of Star Wars dried up much of Ludman's potential market. But when government and university scientists explored earthly applications, "we found, to our great surprise, that what we were doing was capable--on paper--of producing electricity at 5 cents to 6 cents a kilowatt-hour," Ludman says. That could make solar power cost-competitive with conventional power plants.

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