Tessera Solar, the sister company to Stirling Energy Systems, has won a bid to develop up to 500 megawatts of solar thermal power plants on land owned by Riverside County in California.

Tessera said it's teaming up with Optiflex Properties & Development on developing and financing the power plants, which would be located on closed landfills and undeveloped properties, said Janette Coates, a spokeswoman for Tessera.

Tessera announced the project earlier this week, about two weeks after it said it would build a 27-megawatt solar project in Texas and sell the power to CPS Energy, which is run by the city of San Antonio.

Building 500 megawatts would require about 3,500 acres, she said. Tessera and Optiflex are scouting for ideal locations in Riverside for erecting Stirling Energy Systems' SunCatcher equipment.

A SunCatcher is made up of a giant parabolic dish of mirrors (40 feet across) to concentrate the sun onto a receiver called a "power conversion unit (PCU)." Sunlight heats up the hydrogen gas in tubes in the PCU, and the gas goes through a heat exchanger to run a four-cylinder Stirling engine. The engine then drives a generator to produce electricity.

Stirling Energy Systems (SES) recently unveiled a newly designed SunCatcher that it said would be easy to mass produce and maintain than its first-generation design (see Stirling Redesigns SunCatcher, Plans 1.5MW Demo Project).

The history of Stirling engines goes back to 1816, when Robert Stirling in Scotland designed the first machine and built it two years later to pump water from a quarry.

Coates declined to disclose the likely costs of the overall project. The developers are still working out the details of a lease with Riverside County, Coates said.

Tessera and Optiflex would own and operate the solar farms and sell electricity to utilities and communities throughout the state. The companies haven't announced any power sales agreements.

The companies plan to start construction between 2010 and 2012, Coates said.

Houston-based Tessera was formed only this past April by SES to focus on power plant development.

SES, on the other hand, was founded in 1996 and turned heads in 2005 when it announced it would build up to 1.75 gigawatts of solar farms and sell the electricity to Southern California Edison and San Diego Gas & Electric. 

Since then, competition for utility-scale projects has become a lot more intense. SES has to contend with a host of European and other American companies that have have developed different ways to use the sun's heat for generate steam and drive turbines (see Solar Thermal: Which Technology Is Best?). Many of them, such as Abengoa Solar, BrightSource Energy, Solar Millennium and eSolar also have won contracts to sell power to utilities (see Solar Millennium Lands 726MW Contract With SoCal Edison). 

Scottsdale, Ariz.-based SES is still working on the two big projects, and expects to start construction for one of them next year.

Image via Stirling Energy Systems.

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