Super Eco

Photo credit: sateda, SXC

Okay, Smartie, and you thought that solar energy was no good at night when the sun's not actually shining. Yeah, we didn't either. But savvy scientists are showing us wrong. Want to know how? Simple—it's salt.

Salts, or a combination of sodium and potassium nitrate (otherwise used as fertilizers, ick), can store a lot of heat, and about 93 percent of that energy is recapturable. They melt only at super high temperatures and don't turn to vapor until they get a lot hotter than the melting point. The stored heat energy contained in these molten salts can be transferred to water by use of a heat exchanger; the hot water turns to steam which can then be made to turn turbines, which then creates—ta da!—electricity. Voila, a solar-thermal power plant.

The concept has already tested well at Andale, the world's first solar-thermal power plant in sunny Spain, and in experimental use in the deserts of California. Plans are underway to build a second Andale and a solar-thermal plant is planned in the U.S. for the desert area south of Phoenix, but installation of the thermal holding tanks and acres of piping necessary to create such power plants isn't cheap. The cost is roughly $50 per kilowatt-hour for installation. After the initial installation, however, the cost to produce solar-thermal electricity is quite low, only 13¢ per kilowatt-hour—which is still about twice that of cheap coal-fired greenhouse gas emitting power plants.

Researchers are continuing to look into additional ways the sun's energy can be stored, so as to try to reduce the initial costs of building a solar-thermal power plant. There's a lot of energy up there in the sky, just waiting to be used.