Making Solar Power Competitive with Coal [View all]

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http://www.technologyreview.com/energy/39771/?mod=chfeatured

[font face=Times, Times New Roman, Serif][font size=5]Making Solar Power Competitive with Coal[/font]
[font size=4]A study identifies early-stage technologies that could be combined to cut the cost of solar panels in half.[/font]

Wednesday, February 22, 2012 | By Kevin Bullis

[font size=3]By the end of the decade, manufacturers in the United States could make solar panels that are less than half as expensive as the ones they make now. That would be cheap enough for solar power to compete with electricity from fossil fuels, according to a new study in Energy & Environmental Science. The cost reductions will come via technology that's already being demonstrated in research labs at startups, universities, and major solar manufacturers, and could involve silicon, the material most solar panels are made from today.

The report, from researchers at MIT led by Tonio Buonassisi, a professor of mechanical engineering and manufacturing, identifies early-stage technologies that, if employed together, could reduce the cost of making solar panels to 52 cents per watt. Currently, the cost is over a dollar per watt. At 52 cents per watt, assuming similar cost reductions for installation and equipment such as inverters, solar power would cost six cents per kilowatt-hour in sunny areas of the U.S.—less than the average cost of electricity in the U.S. today. Solar power in sunny areas now costs roughly 15 cents per kilowatt-hour, according to the U.S. Department of Energy, although the cost can be sharply higher in small installations or in cloudy areas where solar installations generate less electricity.

The best way to reduce the cost per watt is to make solar cells more efficient—as a result, more power can be produced with a given amount of material and factory equipment. Increasing efficiency also decreases installation costs, since fewer solar panels are needed. But efficiency improvements aren't enough to reach 52 cents a watt. Manufacturers will also need to make solar cells from thinner silicon wafers, make wafers in a way that wastes less silicon, and speed up manufacturing. If a high-efficiency solar cell design slows down manufacturing or requires thick wafers, it likely won't lead to the necessary cost reductions.

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Some high-efficiency solar cell designs lend themselves to thin wafers. One involves sandwiching a wafer of crystalline silicon between two layers of amorphous silicon, as is done with a type of solar cell now produced by Sanyo. This symmetrical structure reduces stress on the wafer. Such cells can be processed at lower temperatures than conventional solar cells. Other cell designs could also work with thin wafers. One puts all of the electrical contacts on the back of a wafer—a process that could be well-suited to processing the cells on a sheet of glass. The U.S. company Sunpower uses a version of this cell design.

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http://dx.doi.org/10.1039/C2EE03489A