Solar power has advanced significantly since the days of inefficient photovoltaics. In California, solar power is being built into roof tiles, and talk is that nanotechnology will make any surface on which the sun shines a source of power—windows, for example. Experiments have been undertaken with a new form of solar energy—Concentrating Solar Power (CSP). In our lifetimes, as homes feed power into the electrical grid, electric meters will run backward, feeding power into the electrical grid from individual homes and businesses, using carbon-based fuels only as backup.
A 380-foot concrete tower surrounded by 600 huge mirrors near Seville, Spain, is part of a new CSP plant that produces solar power that is commercially viable on a large scale. In this case, the power station, constructed by Abengoa S.A., can supply about 6,000 homes. Spain and other European countries are subsidizing CSP and other solar technologies to move away from fossil fuels. According to the consulting firm Emerging Energy Research, 45 CSP projects were in planning around the world by 2007, including some in the United States. The Spanish government has set a goal of 500 megawatts of solar power by the year 2010. Spain is presently subsidizing CSP development, requiring utility companies to buy their power at above-market rates. Abengoa plans to eventually build enough CSP capacity to supply all of Seville,
15 megawatt solar photovoltaic array at Nellis Air Force Base, Nevada, completed December 2007 (U.S. Air Force, http://www.nellis. af.mil)
about 180,000 homes. In the United States, Arizona Power was conducting a test of CSP in 2007.
New CSP technology is much more powerful than photovoltaic cells. A rooftop photovoltaic complex might power a small office building, while the complex near Seville can generate 11 megawatts, enough electricity for a small town. The CSP mirrors track the sun and concentrate its power on single points, generating steam that runs turbines to generate power. Some of the heat is also stored in oil or molten salt to run the turbine after sunset or when clouds block the sun. Such new technologies may increase the potential of solar power and bring down its cost, which is now 12 to 15 cents per kilowatt-hour, compared to an average of 4 cents for coal-fired energy.
In California by 2007 many new homes were being built with solar cells embedded in their roof tiles. T.J. Rodgers, an entrepreneur, underwrote the solar cells' production. The PowerLight Corporation, based near San Francisco, bought the cells from Mr. Rodgers's company, the SunPower Corporation, and turned them into roof tiles. The tiles ended up on houses built by Grupe Homes, based in Stockton, because state utility regulators established a $5,500 state-financed rebate for builders who installed similar systems, which cost $20,000. Under a law that took effect in 2006, the U.S. federal government provides home buyers a $2,000 tax credit; state law guarantees lower electric bills as utilities buy back power homeowners do not need (Barringer, 2006). By the end of 2007, Nellis Air Force Base in Nevada was poised to open what its publicists called the largest solar power complex in the United States.
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