Solar thermal goes big

A massive solar thermal installation, slated to produce over 1 GW of energy, has been announced. From

The largest series of solar installations in history, more than 1,300 megawatts, is planned for the desert outside Los Angeles, according to a new deal between the utility Southern California Edison and solar power plant maker, BrightSource.

The momentous deal will deliver more electricity than even the largest nuclear plant, spread out among seven facilities, the first of which will start up in 2013. When fully operational, the companies say the facility will provide enough electricity to power 845,000 homes -- more than exist in San Francisco -- though estimates like that are notoriously squirrely. The technology isn't the familiar photovoltaics -- the direct conversion of sunlight into electricity -- but solar thermal power, which concentrates the sun's rays to create steam in a boiler and spin a turbine.

Solar thermal power generation seems to be very competitive on the 'city-scale', as it avoids the (currently) high cost of producing photovoltaic panels. The technology is described in the official press release:

The system uses thousands of small mirrors called heliostats to reflect sunlight onto a boiler atop a tower to produce high temperature steam. The steam is then piped to a conventional turbine which generates electricity. In order to conserve precious desert water, the LPT 550 system uses air-cooling to convert the steam back into water. The water is then returned to the boiler in an environmentally-friendly closed cycle. This fully integrated energy system is designed to offer the highest operating efficiencies and lowest capital costs in the industry.