Innovation at the Frontier

Solar Energy
A new type of power plant harnesses the sun-and taxpayers

On February 22^nd, 2008, at an event featuring film stars, astronauts and technology gurus, Acciona, a Spanish conglomerate, is due to inaugurate a new power plant a few miles from Las Vegas. In fact, the plant has been running since last June 2007. But the technology it uses, known as "concentrating solar power" (CSP) is hot right now, as the Hollywood luminaries might put it.

Acciona's new plant, called "Nevada solar One", can generate up to 64 megawatts (MW)-enough, it says, to power more than 14,000 homes. The solar Energy Industries Association (SEIA) says that more CSP plants, with a total capacity of 4,000 MW, are in pipeline and have signed contracts to sell their future output. An 11 MW plant opened in Spain last year. New Energy finance, a research firm, estimates that 2,000 MW of capacity is in the works in Europe.

As their name suggests, CSP plants generate electricity by concerning the sun's rays, usually to boil water. The resulting steam drives turbines similar to those found at power plants that run on coal or natural gas. There are several different designs. The Nevada plant uses long curved mirrors to focus light on a tube of fluid running just above them. The Spanish plant uses a forest of smaller mirrors to focus light on a tower in their midst. Other concepts involve long flat mirrors and devices resembling satellite dishes.

Solar power, of course, does not produce climate-changing greenhouse gases. But it also excites utilities because it generates the most power just when it is needed: on hot, sunny days when people turn on air conditioners. And CSP provides a way around the main drawbacks of solar power from photovoltaic cells. Unlike them, it does not involve expensive silicon wafers. And some designs provide power round the clock, not just when the sun is shining, by storing energy in the form of molten salt.

Even so, CSP is still not as cheap as coal or gas fired plants. America's CSP boom is driven by state laws requiring utilities to generate a certain share of their power from renewable sources, and by generous federal tax breaks, which offset as much as 45% of development costs, according to SEIA. In Spain, meanwhile, utilities must pay an extra €0.25 ($0.37) per kilowatt-hour on top of the market price for power from CSP.

America's tax breaks are due to run out at the end of the year, and without them, says Rhone Resch of SEIA, no more CSP plants will be built there. But in the long run, he argues, costs should come down. And if fossil-fuel prices continue to increase and American power plants have to start paying for their greenhouse gas emissions, CSP might just achieve "grid parity" with the wholesale power price. That really would be an excuse for party.