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Science corner

Sophie Duncan gets all steamed up

This is the largest solar power plant in the World. Built in the Mojave desert, one of the sunniest places in America, it delivers more than 350MW of power. Despite its futuristic appearance, this solar electric generating station is very conventional.

The electricity is generated using a steam turbine. Thousands of parabolic trough reflectors placed in rows focus the Sun's energy on to a pipe, at the focal line of the parabola, increasing the intensity of the light some 40 times. The pipe carries a thermal oil which heats up and is pumped into a heat exchanger, where water is converted into steam to drive the turbines.

On cloudy days, or at night, it can run off natural gas. However, 75 per cent of the output is provided directly from the Sun's energy. A limiting factor is desert sand covering the reflectors. Sophisticated cleaning arrangements help.

The plant, built in the mid 1980s, conprises several fields of troughs, with a total surface area of two million metres squared.

The first solar powered motor was created in the 1860s by a Frenchman called Auguste Mouchout.

Sophie Duncan is a physicist and programme manager with Science Yearwww.scienceyear.com

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