Concave mirrors and lenses have been used for ages
to concentrate the sun’s rays on a single point and therefore multiply
its strength. Mirrors with a parabolic cross-section are especially
suited to this purpose because they can also focus the outer rays
towards the middle. If a mirror is designed in the form of a trough,
the solar radiation, concentrated about forty times, can be focused on
an absorber tube with a heat-conducting fluid inside.
The best use for these tube collector
thermal solar power systems is for domestic water heating and heating
support. A well-known high-tech system is the parabolic trough power
plant in the Californian Mojave Desert. It has a total of 2.3 million
square meters of mirror surface area and produces 354 megawatts of
electricity. To improve their performance they can be rotated about
their roll axis. The heat-conducting fluid is heated up to 400 ºC and
by means of a turbine and generator then produces electric current.
Similar large plants are also planned at Crete, Egypt and India and
should be able to deliver electricity at a price of about $ 0.07 (0.08
€) per kilowatt-hour.
The Center for Solar Energy and Hydrogen Research
(Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSF)) in
Stuttgart, Germany operates an experimental plant in Almeria, Spain with
oil as the heat-conductor and heat-storage fluid.
source: http://www.solarserver.com
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