Southern California Edison Co. said Wednesday it struck "the world's largest solar deal" by agreeing to buy 1,300 megawatts of power from solar plants to be built over the next seven years in Southern California's Mojave Desert.

The utility said it has entered seven 20-year contracts with Oakland-based BrightSource Energy to purchase enough power to serve nearly 845,000 homes.

Pending approval by the California Public Utilities Commission and other regulatory agencies, BrightSource said it plans to build seven solar power plants in stages, with the final plant slated to go on line in 2016.

The plants would utilize about 10,500 acres of the Mojave Desert, although in most cases specific locations have not been selected, BrightSource said.

Under the agreement, the first 100 megawatts that Southern California Edison would receive would come from a 400-megawatt solar power plant planned to be built at Ivanpah that would begin operating in 2013.

BrightSource said it intends to break ground later this year on that plant, which would be the first commercial application of its Luz Power Tower technology.

At Ivanpah, BrightSource plans to carpet about 3,600 acres of desert with thousands of small flat glass mirrors.

The mirrors will be arrayed to reflect sunlight to heat water-filled steel boilers mounted on top of 300-foot towers.

Steam that is created will turn turbines to generate electricity without the carbon dioxide emissions associated with fossil fuel-fired power plants and blamed for contributing to global warming.

Stuart Hemphill, Edison's vice president of renewable and alternative power, said the utility, which already is the nation's largest user of renewable energy, sees solar as "a large untapped resource, particularly in Southern California."

According to BrightSource's Web site, the sun shines reliably 330 to 350 days a year in the Mojave, making it a prime area for solar energy generation.

Southern California Edison delivers 667 million kilowatt hours of solar power, which represents 5 percent of its renewable portfolio, with more of its renewable power coming from geothermal and wind contracts.

John Woolard, chief executive of BrightSource, called its solar contracts with Edison "a landmark agreement" that "illustrates the increasing demand for solar thermal energy as a reliable source of utility-scale renewable power."

Prevents emmissions

Woolard said the 1,300 megawatts of new solar projects would prevent more than 2 million tons of carbon dioxide emissions that would be produced by natural gas-fired power plants.

That would be equivalent to removing 335,000 cars from the road, he said.

Mike Marelli, a manager in Edison's renewable energy group, said by state law Edison must keep confidential how much it has agreed to pay for the solar power.

He said it's difficult to compare the price of solar power with the cost of conventional power, which in California fluctuates sharply with the price of natural gas.

The price of solar power from BrightSource will remain fixed for the duration of the contracts, he said.

Still, solar energy doesn't come cheap.

According to the California Energy Commission, the cost of producing electricity by a common thermal solar technology in 2007 was almost three times the cost of producing electricity by conventional combined cycle gas-fired power plants.

BrightSource has said its method is more cost-effective.

As part of California's effort to reduce carbon emissions, Southern California Edison and other investor-owned utilities face a legislated mandate to supply 20 percent of their customers' needs with renewable energy by 2010, and there are proposals in the Legislature to raise the requirement to 33 percent or higher by 2020.

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Southern California Edison currently meets about 16 percent of its customer's power demands with renewable energy, Hemphill said.

The utility won't reach 20 percent by 2010, he said, but will still comply with state law that gives utilities more time if they have contracted to buy renewable power that won't be delivered until additional transmission is built.

Transmission has been a major hurdle for development of utility-scale renewable energy plants, which typically are far from urban centers.

"We will need significant new transmission for these projects and are in the process of determining the size and the best way to interconnect them," said Hemphill.

Tom Doyle, executive vice president in charge of project development at BrightSource, said the company is choosing solar plant sites so they can link into existing transmission corridors rather than require that transmission lines be laid on new routes.

Hemphill said Edison hopes to have the transmission improvements "scoped out later this year."

Environmentalists have raised concerns about how transmission projects and large solar farms will affect the desert and its wildlife.

"The Sierra Club is solidly behind development of renewable energy, but it is all about location, location, location," said Joan Taylor, the Sierra Club's California/Nevada desert and energy chairman.

Taylor said the club wants solar farms to be placed in areas already "disturbed" -- abandoned agricultural land and air bases -- rather than on pristine desert.

Carl Zichella, the Sierra Club's western renewable programs director, said the club does not oppose the Ivanpah solar project but is working with the regulatory agencies and BrightSource to make certain there will be adequate mitigation for desert that is damaged.

Reach Leslie Berkman at 951-368- 9423 or lberkman@PE.com