Economist.com: producing electricity with cheap Solar balloons - 0 views
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SOLAR cells are expensive, so it makes sense to use them efficiently. One way to do so is to concentrate sunlight onto them. That means a smaller area of cell can be used to convert a given amount of light into electricity. This, though, imposes another cost-that of the mirrors needed to do the concentrating. Traditionally these are large pieces of polished metal, steered by electric motors to keep the sun's rays focused on the cell. But now Cool Earth Solar of Livermore, California, has come up with what it hopes will be a better, cheaper alternative: balloons. Anyone who has children will be familiar with aluminised party balloons. Such balloons are made from metal-coated plastic. Cool Earth's insight was that if you coat only one half of a balloon, leaving the other transparent, the inner surface of the coated half will act as a concave mirror. Put a solar cell at the focus of that mirror and you have an inexpensive solar-energy collector.
