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Bloomberg News A solar power plant in Nevada
THE TECHNOLOGY: Energy from the sun can be used to make electricity directly with photovoltaic panels or indirectly using concentrated sunlight to heat a liquid, which produces steam to turn electrical turbines. Concentrating solar plants can be built to store heat and deliver power for several hours without sunlight.
CURRENT STATUS: Solar power (both photovoltaic and concentrating) produced an estimated about 3.2 billion kilowatt-hours of electricity in 2009. Total capacity—the amount of power that could be produced if the sun shone constantly—of solar photovoltaic systems has been doubling every two years, and the pace of increase is expected to rise further: An estimated 2,000 megawatts of solar capacity in 2009 was nearly 45% higher than in 2008. That includes about 980 megawatts of concentrating-solar projects; an additional 81 megawatts are under construction.
WHY IT'S GOING TO TAKE SO LONG: Even at that rate of growth, solar power is still minuscule: Solar generation in 2009 accounted for less than 0.1% of total electricity production in the U.S. Solar capacity remains less than 1% of the total. "The biggest obstacle is that we're starting at such a low level," says John Benner, a research manager at the National Renewable Energy Laboratory.
The cost of solar installations has fallen in recent years, but remains high, partly because demand continues to keep pace with supply. The cost for average residential installations was about $5.40 a watt of capacity in 2008 and $4.20 a watt for commercial, after a raft of federal, state and local incentives, according to a study by the Lawrence Berkeley National Laboratory. (Solar installations depend heavily on subsidies, which vary widely; without incentives, costs average $7.50 a watt.) Thanks to capital expenses, electricity from solar is expensive: Estimates of solar costs cover a broad range, from 25 to 46 cents a kilowatt-hour for residential and from 17 to 29 cents from a concentrating solar plant. That compares with about 7 cents a kilowatt-hour for coal and natural gas and 10 cents for wind, according to estimates by the Energy Power Research Institute.
Like wind farms, utility-scale solar photovoltaic and concentrated-solar projects also require additional transmission connections. Since most aim to build in the environmentally sensitive desert Southwest, where much of the land is publicly owned, they also face lengthy and complicated permitting reviews.
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Bloomberg News A Chevrolet Volt getting charged at last month's Consumer Electronics Show in Las Vegas
THE TECHNOLOGY: In theory, electric vehicles could replace most gasoline-powered cars and light trucks. They can run entirely on battery power, or in the case of plug-in hybrids, on batteries that can be charged by a separate gasoline engine when needed as a backup.
CURRENT STATUS: About 56,000 electric vehicles are in use, but the numbers are deceiving—most are limited to low-speed driving and have limited range. So far, Tesla Motors Inc.'s Roadster is the only open-road electric vehicle, but a handful of other all-electric cars, including Nissan Motor Co.'s Leaf, are expected to come to market in 2010. The first commercial plug-in hybrids, led by General Motors Co.'s Chevy Volt, also are slated to be available later this year.
WHY IT'S GOING TO TAKE SO LONG: The biggest obstacle is cost. The advanced lithium-ion battery pack that powers the Volt, which can travel 40 miles on a charge, can cost as much as $10,000, though prices are expected to fall as production ramps up. The U.S. Energy Information Administration predicts that in 2030, the added cost of a plug-in hybrid will be higher than fuel savings unless gasoline costs around $6 a gallon.
Another challenge is the need for public recharging stations. Though most drivers travel fewer than 40 miles a day, well within the range of first-generation electric vehicles, consumers will balk if they worry about running out of juice.
Public charging spots are less important for plug-in hybrids, which are more likely to be recharged at home. Still, owners may need to upgrade their existing outlets to recharge more quickly; a 120-volt outlet will take about four to six hours to charge a plug-in vehicle and about 12 to 24 hours for an all-electric vehicle. A 240-volt outlet, which can charge an electric vehicle in about three to six hours, generally requires adding a circuit to the home's electric system to handle the additional load.
— Mr. Totty is a news editor for The Journal Report in San Francisco. He can be reached at michael.totty@wsj.com .
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