Giving Solar a Chance

Another slice of the new energy supply pie will likely derive from the old­est source of power. New, large-scale efforts to put solar power to work have recently taken shape in California. Two separate companies are constructing solar plants that will be ten times bigger than those now in use. Spurred by state mandates to derive 20 percent of its electricity from renewable sources by 2010, Pacific Gas and Electric will purchase the plants’ electricity.

Each plant uses photovoltaic technology, which turns sunlight directly into electricity instead of using it to heat water. OptiSolar, a company that has just begun to make thin-film solar panels—with a layer of semiconductor material thinner than a human hair on the back of a glass panel—will install 550 megawatts in San Luis Obispo County, in central California. And the SunPower Corporation, which uses crystalline cells, will build 250 mega­watts in the same county. The OptiSolar plant will cover about nine square miles, and the SunPower plant about 3.5, although the actual cell area will be smaller. Together, these plants will generate a total of 800 megawatts.

A megawatt is enough power to run a large Wal-Mart. At peak hours, to­gether the plants will produce as much power as a large coal or nuclear power plant. But they will run far fewer hours of the year, so output will be at least a third less than that of a coal plant of the same size. SunPower’s panels are mounted at a 20-degree angle, facing south, and pivot over the course of the day so they continuously face the sun. OptiSolar’s panels are installed at a fixed angle. They are larger and less efficient, but much less costly, so that the cost per watt of energy is similar, company executives said. (OptiSolar)

Solar energy, both photovoltaic and thermal, which uses the sun’s heat to make steam, is bounding ahead, driven mostly by state quotas and govern­ment incentives. California requires that 20 percent of the kilowatt-hours sold by investor-owned utilities come from renewable sources by 2010, a goal that some companies are struggling to meet. Pacific Gas and Electric expects that when these two solar plants are completed, their total will rise to 24 per­cent, but that will not be until 2013.

The planned California installations raise questions about the idea that solar power is best deployed on the roofs of houses and businesses. Although building units near their point of use can help avoid transmission expenses, the companies said that by building on a gargantuan scale, they expected to achieve economies of scale in the cost of design, installation, and connection to the grid, as well as marketing and overhead. A typical home installation is several thousandths of a megawatt, while these proposed units are in the hun­dreds of megawatts. Boosting the solar manufacturing base with such large projects is an important step toward lowering the cost of solar energy, for both large commercial projects and for smaller distributed rooftop systems, for future generations.

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