Which technology will win over utilities' hearts: solar thermal or photovoltaics?

It's an issue the American utilities will have to consider more often as a growing number of companies apply for permits to build solar-thermal power plants. A solar thermal power plant typically uses hundreds of mirrors to concentrate the sunlight for boiling some type of liquid for producing steam, which then drives an electricity generator. That scale gives it an advantage in lowering the overall costs of generating power, advocates say.

Solar-thermal energy proponents also like to point out that they don't need to use expensive semiconductor materials to produce electricity, unlike photovoltaic (solar-panel) developers.

"The scale we can implement through solar thermal is much faster [than photovoltaics]. The cost is much less. When you think about how much energy has to be generated, the near future will tilt toward solar thermal," said Charlie Ricker, senior vice president of marketing and business development for BrightSource Energy.

BrightSource, based in Oakland, Calif., has reason to be bullish. It recently signed a huge deal with the Southern California Edison, and it is due to deliver solar power to another large California utility – Pacific Gas and Electric (see BrightSource Inks 1.3GW SoCal Edison Deal and The Rush to Gigawatts in the Desert Explodes).

Whether BrightSource can fulfill its contracts remains to be seen, given the size of the projects. But its ability to win mega deals raises the question: Can photovoltaic companies' ambition to build large-scale power plants to sell power to utilities pay off?

Energy systems composed of solar panels, which convert sunlight into electricity, have been deployed more widely than solar-thermal power plants. Those panels can go on residential and commercial rooftops as well as be mounted on the ground. Photovoltaic technology supporters argue that building solar thermal power plants also requires using construction materials, such as copper, steel and aluminum, whose costs can go up quickly.

"We can build virtually anywhere at any scale and can be deployed rapidly," said Ed Smeloff, senior manager of utility project sales at SunPower Corp., a solar panel maker in San Jose, Calif. "It's a race. We are in a sweet spot right now – we have a technology that works."

SunPower has signed contracts to supply solar power to utilities, though not at the same scale as those under development by BrightSource (see PG&E to Buy 800MW From OptiSolar, SunPower).

The two men gave those brief marketing pitches during a discussion at the UC Berkeley Energy Symposium Monday about which solar technologies will offer cheaper and more reliable sources of electricity for utilities. Utilities across the country have been inking power-purchase agreements with solar power developers or building their own solar power projects in order to meet state mandates for selling renewable power.

Comparing the installation and operating costs between photovoltaic and solar-thermal is a bit of guesswork, however, since utilities and solar companies rarely disclose them. There are more data on the materials and installation costs of solar panel energy systems, given their wider deployment and availability as retail products for the consumer market.

Severin Borenstein, director of the University of California Energy Institute and a business school professor at UC Berkeley, has looked closely on the costs of solar energy. Speaking on the same panel, Borenstein said that a small, residential solar-panel system costs about 40 cents per kilowatt-hour over the system's lifetime while larger solar-panel system would cost 20 cents per kilowatt-hour.

A solar-thermal power plant could cost 18 cents per kilowatt-hour over the power plant's lifetime, a figure that would include the cost of land, Borenstein estimated, noting that there aren't good numbers to make a more definitive calculation. All these cost estimates didn't take into consideration the various state, federal and private subsidies for buying and installing solar energy systems.

In comparison, electricity from coal-fired power plants costs about 5 cents to 6 cents per kilowatt-hour.

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