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Before President George W. Bush signed the federal energy bill into law on Aug. 8, he got a firsthand glimpse of a technology that could transform the deserts of the Southwest. Instead of a sandy wasteland, there would be gleaming farms with thousands of giant dish-shaped mirrors measuring 37 feet in diameter. Each dish would track the sun and focus its heat rays on an oil-barrel-size contraption suspended out in front, harnessing the heat to drive a 25-kilowatt generator.
Plant enough of these solar-dish farms, Bush learned on his tour of Sandia National Laboratories' National Solar Thermal Test Facility near Albuquerque, and they could mightily reduce the need for electric power plants that burn fossil fuels and emit carbon dioxide.MOJAVE MEGAWATTS
The day after the Presidential tour, Sandia's vision began to look a lot more real. The supplier of the solar-thermal dish generators, Stirling Energy Systems Inc. in Phoenix, won a major commitment from Southern California Edison Inc. () (SCE): For 20 years the utility will buy all the electricity that Stirling Energy can generate at a 500-megawatt solar energy farm that Stirling will build in the Mojave Desert near Victorville, Calif. This could be the biggest solar installation in the world -- equal to a typical coal-fired plant. And if local power lines can be upgraded to handle more juice, Stirling could enlarge the facility to 850 MW -- and SCE would take all of that, too.
Stirling's deal was made possible by several trends that are pushing alternative energy into the mainstream. As oil has become more expensive, so have natural gas and coal, the primary fuels for power plants. At the same time, concerns about global warming have prompted lawmakers -- local, state, and now the feds -- to unleash incentives for renewable energy. Wind power, solar energy, geothermal, and biomass fuels are all benefiting.
If the dishes do well, Stirling Energy's 4,500-acre desert farm will usher in new potential for Stirling engines, invented in 1816 by Church of Scotland minister Robert Stirling. His engine is ideal for green energy because it doesn't burn fuel internally. Instead, its pistons are driven by heating and expanding a reservoir of gas, which then cools for the next cycle. Using the sun's energy to heat the gas means zero fuel is burned.
Stirling Energy stands to rake in upwards of $90 million a year once the solar dishes are generating 500 MW in 2011. For SCE, already the largest purchaser of renewable energy in the U.S., the extra 500 MW will more than double the 354 MW of solar power it tapped in 2004 from nine other solar-thermal operations in the Mojave. It will also add almost 20% to SCE's 2,588 MW of renewable energy sources, including 1,021 MW of wind power. Last year more than 18% of the electricity that the utility delivered to its customers came from renewables.
Monster dish-shaped "heat antennas" are hardly familiar icons of green power. People tend to associate solar energy with flat, glassy panels that convert photons from sunlight into electric current. But such photovoltaic cells don't produce power as efficiently as Stirling dish generators. Cells typically convert just 10% to 15% of the sun's light -- and many cells perform at just half that level. In contrast, Stirling dishes achieve almost 30% in Sandia's six-dish system. "Later this year we'll do even better," declares D. Bruce Osborn, Stirling Energy's new CEO and a longtime solar proponent.DAYTIME ONLY
Why hasn't Stirling Energy's technology made more of a splash in the power business? "Our dilemma has always been how to get costs down," explains Osborn. The dish assemblies now run $250,000 each. But that's because most have been handcrafted in sporadic lots of one or two units. Building a group of 40 or so would trim the cost to $150,000 each, Osborn estimates. With real mass production, that could drop by 50%.
So when SCE said it wanted to buy more renewable energy, Osborn's outfit proposed the 500 MW project as the means of moving beyond its chicken-or-egg impasse. Producing that much electricity will require 20,000 dishes, built in a steadily increasing flow over several years. "We're ramping up now," says Osborn.
He expects to have 40 dishes in place for a 1 MW facility by the end of next year, followed by 50 MW in 2008. The electricity will be delivered only when the sun is shining, but that's when the utility's customers place peak demands on electricity. "Our system is a really good match, providing peak power at times of peak load," notes Osborn.
The price per kilowatt-hour (kWh) that SCE will pay is confidential and must be approved by the California Public Utilities Commission. But there's little doubt that the contract will get a thumbs-up, perhaps as soon as next month. One reason: SCE says the price it negotiated is so attractive -- "well below the 11.33 cents per kWh" it now pays for peak power -- that it won't seek any subsidies from the state.
Subsidies have been a common means of jump-starting solar projects in California and 46 other states. Early this year, Governor Arnold Schwarzenegger unveiled his Million Solar Roofs Initiative, calling for an additional 3,000 MW of solar power by around 2017. If the Million Solar Roofs Initiative passes next month, as expected, homeowners who install solar energy systems will earn a 7.5% state income-tax credit, in addition to other state incentives and the new 30% federal tax credit.
Consumers, of course, are unlikely to plant Stirling Energy's huge 37-foot dishes in their backyards, even if they are the most efficient solar generators around. But the technology dovetails nicely with California's mandate that utilities must derive 20% of their electricity from renewable sources by 2017 -- and Schwarzenegger would like to boost that goal to 33% by 2020. Osborn says that a dish farm of 11 miles square could produce as much electricity as the 2,050 MW from Hoover Dam. "We're already looking at a half-dozen one-square-mile sites in the California desert," he says, "and there's lots and lots more territory there."
Theoretically, Stirling dish farms with a total area of 100 miles square could replace all the fossil fuels now burned to generate electricity in the entire U.S. What happens in the California desert over the next few years could determine whether thermal solar power can help end the dominance of fossil fuels. By Otis Port in New York