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BrightSource Energy lands $115 million for solar 'power tower'

Showdown in the desert: BrightSource's power tower solar power plant design looks to displace traditional mirrored trough designs.

BrightSource Energy has raised $115 million, a hefty vote of confidence for its solar power tower technology that converts heat to electricity.

Investors included, the philanthropic arm of Google, as well as VantagePoint Venture Partners, BP Alternative Energy, Statoil Hydro Venture, and Cargill subsidiary Black River. Existing investors DBL Investors, Draper Fisher Jurvetson, and Chevron Technology Ventures also participated in the Series C round.

A drawing of a power tower where a field of heliostats concentrate light on a tower that houses a steam turbine. BrightSource Energy

BrightSource designs and operates solar power plants aimed at utilities that need to invest in renewable energy. Pacific Gas & Electric said in March it will purchase up to 900 megawatts from BrightSource solar power plants. It plans to start construction in 2009.

Solar thermal systems are considered cost-competitive with natural gas power plants, particularly for "peak" power which typically happens in the afternoon. They work best in desert environments; existing plants are in the Southwest U.S.

Using mirrors or lenses, sunlight is concentrated onto a liquid which makes steam that turns an electricity turbine.

The most traditional solar thermal technology is a power plant designed around a series of mirrored troughs. BrightSource, by contrast, uses a field of heliostats, or mirrors, to reflect light onto the top of a tower where a steam turbine is.

BrightSource senior vice president for marketing and business development Charles Ricker, who spoke on a panel at a clean technology investor conference in New York on Tuesday, argued that troughs will be phased out in the coming years in favor of other systems.

Power towers are more efficient and require less capital to make than trough solar thermal systems, he said.

The primary driver behind solar thermal technology, which works best in desert areas, is California where some utilities need to make renewable energy part of their power generation mix.

The state's renewable portfolio standard is set at 20 percent by 2010 and 33 percent by 2012, Ricker explained.

To date, BrightSource has raised $160 million.