From five miles away, the Nevada Solar One power plant seems a mirage, a silver lake amid waves of 110 degree F. desert heat. Driving nearer, the rippling image morphs into a sea of mirrors angled to the sun.

As the first commercial �concentrating solar power� or CSP plant built in 17 years, Nevada Solar One marks the reemergence and updating of a decades-old technology that could play a large new role in US power production, many observers say.

�Concentrating solar is pretty hot right now,� says Mark Mehos, program manager for CSP at the National Renewable Energy Laboratory in Golden, Co. �Costs look pretty good compared to natural gas [power]. Public policy, climate concern, and new technology are driving it, too.�

Spread in military rows across 300 acres of sun-baked earth, Nevada Solar One's trough-shaped parabolic mirrors are the core of this CSP plant � also called a �solar thermal� plant. The mirrors focus sunlight onto receiver tubes, heating a fluid that, at 735 degrees F., flows through a heat exchanger to a steam generator that supplies 64 megawatts of electricity to 14,000 Las Vegas homes.

Today the United States has 420 megawatts of solar-thermal capacity across three installations � including Nevada Solar One. That's just a tiny fraction (less than 1 percent) of US grid capacity. But Nevada Solar One could signal the start of a CSP building boom.

Efforts to generate another 4,500 megawatts of solar thermal power are now in development across California, Nevada, Arizona, and New Mexico � all of which have the flat, near-cloudless skies most desirable for solar thermal, the Solar Electric Industries Association reports.

Photovoltaic panels that produce electricity directly from the sun's rays work well on rooftops, but are still too costly for utility-scale power generation. Solar thermal, however, is nearing the cost of a natural gas-fired turbine power plant � making it a winner with several power companies that have signed long-term contracts to purchase solar-thermal power.

Desert land lures developers In fact, there's a land rush at the federal Bureau of Land Management. As of July, the BLM reported more than 125 applications to build solar power on about 1 million acres of desert, up from just a handful of proposals a few years ago.

�We think there's a good market there,� says Travis Bradford, an expert at the Prometheus Institute, a Boston-based solar-energy market research firm. His firm sees 12,000 megawatts (12 gigawatts) of solar thermal installed by 2020 and maybe 20 times that in coming decades.

Dr. Mehos says perhaps 100,000 megawatts (100 gigawatts) could be built across the US Southwest over the next 30 years.

�You could supply the entire US with the sun power here in a little piece of the Southwest,� says Dan Kabel as he strolls beneath a row of trough-shaped mirrors. Mr. Kabel is chief executive of Acciona Solar Power, which owns the $266 million Nevada Solar One project. �As fossil fuel costs rise, this plant is unaffected. �If America doesn't do this, if we don't install many more of these clean solar-power systems, we'll just end up seeing a lot more fossil-fuel plants instead.�

Still, the cost of power remains critical. Commercial CSP systems emerged in the late 1990s, only to be squashed by falling natural gas prices.

Today, as natural gas prices rise along with concerns about carbon emissions and global warming, the stable, predictable costs of carbon-free solar thermal is increasingly comforting to utilities.

�What's different now from the '80s and '90s is that we have much higher natural gas prices than back then,� Mehos says. �I don't think people foresee a serious drop in natural gas prices now. Even if they fell 30 percent, CSP would look attractive.�

The importance of tax credits Concentrating solar technology produces electricity for about 17 cents per kilowatt hour (kWh), Mehos estimates. But subsidies remain critical to solar thermal development in both the US and Spain, two global hotbeds of CSP development. With the federal investment tax credit, or ITC, costs drop to about 15 cents per kWh � low enough to compete with natural gas.

A key feature of solar thermal is its potential to use heat-storage technology to generate power after the sun sets. Nevada Solar One is considering adding a molten-salt or similar system to allow it to supply power for several hours after sundown.

With such storage systems, solar thermal becomes even more attractive to utilities, experts say. Arizona Public Service is contracting with Abengoa to build a 280-megawatt solar thermal plant near Phoenix that will cost more than $1 billion and have molten-salt heat storage. �Arizona Public Service really does want to put this [solar thermal] plant in because in the future this really could replace natural gas,� says Reese Tisdale, an analyst at Emerging Energy Research, a market-research firm in Boston. �They're the first to say that once this plant is installed, the fuel is free.�

So far, US development of solar thermal is dominated by a handful of big overseas companies, including Abengoa and Acciona (Spain), as well as Solel Solar Systems (Israel), Solar Millenium (Germany), and Ausra (Australia), now headquartered in Palo Alto, Calif.