Solar furnace

A solar furnace or solar furnace is an optical system to provide concentrated solar radiation. The concentrated energy of the sunlight can be used for the simple heating of a material, aging experiments of plastics or coatings, endothermic chemical reactions, or for loading experiments with mechanical or electrical components.

Designs

The concentrator component of a solar furnace works like a magnifying glass. For technical reasons, however, a hollow or parabolic mirror is used, which focuses the incident light from the sun at one focus. The reflective surface of this concentrator can range from 1 m to be large to some 100 sqm. If larger areas needed, use is usually a heliostat field, in which several flat mirrors reflect the light to a point.

In order to ensure optimum illumination of the concentrator, it is necessary to continuously follow the heliostats of the sun. This is accomplished either by software that constantly calculates the current position of the sun, or a sensor, it is used that determines the position of the sun and so ensures tracking of the heliostats. For a solar furnace with concentrator three possible geometries are realized in practice:

  • Directly tracked concentrator.
  • Fixed on-axis concentrator with tracked heliostat.
  • Fixed off-axis concentrator with tracked heliostat.

For larger concentrators are those of individual planar mirrors, and assembled in a Fresnel arrangement of individual focusing mirrors. You can reach concentrations up to several 10,000 suns.

The reflective components must meet certain qualitative criteria. So it is important that the reflectivity is as high as possible and accurately known as well as the scattering of the reflective surface. Also to be reflected wavelengths are an important criterion when, for example, the UV ( A, B) - would like to use parts of sunlight.

The effective concentration is directed to direct sunlight. Thus, the climatic conditions at the site of a solar furnace play an important role.

Solar furnaces ( experimental facilities)

  • High-flux density solar furnace in Cologne DLR, Power: 25 kW thermal, concentration: up to 5200 times sunlight
  • Odeillo (France), Power: 1000 kW thermal
  • Plataforma Solar de Almería ( Spain)
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