Solar Concentrator

one or more mirrors or lenses that collect (focus) solar rays to increase the intensity of solar radiation.

Devices for concentrating solar rays have long been known (for example, the incendiary devices of the ancient Greek mathematician and engineer Archimedes and the French scientists T. P. Buffon and A. L. Lavoisier). In his work On Optics, M. V. Lomonosov described the original optical system he devised from flat mirrors and converging lenses. In the USSR the first large solar concentrator, in the form of a paraboloid 10 m in diameter, was built in 1946 in Tashkent. Similar paraboloidal solar concentrators were constructed in France, the USA, and Japan. In France, for example, the largest solar furnace, with paraboloidal solar concentrators 54 m in diameter, began operation in 1968. The largest composite-type solar concentrator, with a mirror surface of 20,000 sq m, has been planned in the USSR for a solar thermal power plant.

The principal elements of a solar concentrator are a rigid supporting unit and a mirror or lens part. In the 1960’s a new trend began to develop in manufacturing semirigid and inflatable solar concentrators from polymeric transparent and metallized films. The form of the reflecting surface and the scheme of the solar concentrator vary widely: they may be paraboloidal (parabolic-cylindrical or cylindrical), conical, toroidal, a composite of individual flat mirrors, a mirror-lens scheme, or in the form of flat mirrors that track the sun and an immobile paraboloidal concentrator (the movable flat mirrors are usually called orienters or heliostats; they serve to direct solar rays onto the immobile solar concentrator). In terms of the character of their surfaces, solar concentrators are divided into beveled types, with a discontinuous mirror surface, and smooth types, with a continuous mirror surface. Composite solar concentrators are a system of movable or fixed flat or curved mirrors and lenses. The maximum intensity of energy achieved on high-precision paraboloidal solar concentrators is 35 x 10³ kilowatts per sq m (kW/m²)— slightly less than half the intensity of radial energy on the sun’s surface (74 x 10³ kW/m²).