Solar thermal energy making a comeback

Solar thermal technology, dormant for about 16 years, is waking up fast.

Nevada Solar One, a 64-megawatt power plant outside of Las Vegas, has begun to supply electric power to the grid, Acciona Solar Power, which owns and built the plant, said on Wednesday.

The plant, which covers 400 acres, will generate 134 million kilowatt-hours of power a year. That's enough to power 15,000 households annually. (Sixty-four megawatts refers to the maximum power the plant can generate at any given time. Kilowatt-hours effectively refers to how much power gets delivered when measured over time.)

Acciona will sell electricity from the plant to Nevada Power Company and Sierra Pacific Power Company under long-term, fixed-rate contracts.

Nevada Solar One is the first thermal power plant built in the world in 16 years. Other companies, however, are constructing similar and larger plants in California's Mojave Desert, where an existing solar thermal plant has been cranking out electricity for over 20 years, and elsewhere. Acciona has a project under way in its home country of Spain.

Solar thermal plants, also called concentrated solar power plants, harvest heat from the sun with highly polished mirrors. The mirrors concentrate the heat on a tube filled with liquid or gas. Pressure builds inside the tube, and the pressure is then exploited to crank a turbine.

Heat is harvested by the mirrors. What can't be economically converted to electricity at the time it's obtained can be stored in molten salts at these plants. Thus, solar thermal plants are capable of generating electricity at night.

By contrast, solar panels essentially harvest electrons from sunlight.

Although solar thermal plants aren't cheap and take years to complete--Nevada Solar One's budget ran to $250 million--many believe that the technology is capable of delivering electricity for a price comparable to more traditional plants. The trick is to build massive plants providing close to a gigawatt, or 1,000 megawatts, of power, and building the plants close to urban areas.

Because of its smaller size, Nevada Solar One won't likely provide electricity at rates on par with regular grid power for several years, said executives from Schott, a German company that supplied components to the project.

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