Solar furnace

Solar melting furnace Center du Four Solaire Félix Trombe in Odeillo, France ( detailed view )

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

Designs

The concentrating component of a solar furnace works in principle like a burning glass . For technical reasons, however, a concave or parabolic mirror is used, which focuses the light incident from the sun in a focal point. The reflective surface of this concentrator can be from one square meter to a few hundred square meters. If larger areas are required, a heliostat field is usually used in which several plane mirrors map the light onto one point.

To ensure optimal illumination of the concentrator, it is necessary to continuously track the sun with the heliostat . This is done either by software that constantly calculates the current position of the sun, or a sensor is used that determines the position of the sun and thus ensures that the heliostat is tracked. In practice, three possible geometries are implemented for a solar furnace with a concentrator:

• direct tracking concentrator,
• stationary on-axis concentrator with tracking heliostat,
• Fixed off-axis concentrator with tracking heliostat.

In the case of larger concentrators, these are composed of individual flat mirrors or, in a Fresnel arrangement, of individual focusing mirrors. Concentrations of up to a few 10,000 suns are achieved.

The reflective components must meet certain qualitative criteria. So it is important that the reflectivity is as high as possible, or known exactly, as is the scattering of the reflecting surface. The wavelengths to be reflected are also an important criterion if, for example, you want to use the UV (A, B) components of sunlight.

Directed direct sunlight is a prerequisite for effective concentration. The climatic conditions at the location of a solar furnace therefore play an important role.

Solar ovens (test systems)

• High flux density solar furnace in Cologne of the DLR , output: 25 kW thermal, concentration: up to 5200 times sunlight
• Odeillo (France), power: 1000 kW thermal, numerous heliostats in the area, 1 paraboloid mirror.
• Plataforma Solar de Almería (Spain), heliostat field with a total area of 20,000 m ²
• Prototype from 1949 by Félix Trombe (1906–1985) in Mont-Louis , France, 50 kW, 1 flat heliostat, 1 paraboloid mirror.

See also

• Solar cooker
• Solar thermal power plant

Web links

Commons : Melting furnace Center du Four Solaire Félix Trombe  - Album with pictures, videos and audio files

• Plataforma Solar de Almería ( Memento of March 27, 2009 in the Internet Archive )
• Le Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), Odeillo, France
• Solar Technology Laboratory of the Paul Scherrer Institute, Villigen, Switzerland

Individual evidence

1. ↑ M. Shubnell and H. Ries: Velocity-controlled tracking of the sun . Solar Energy Mater., 21, 207-212.
2. ^ A. Neumann, G. Dibowski, U. Groer, A. Kalt, A. Lewandowski: The optical design of the solar furnace of the DLR Cologne , conference proceedings DGS Sonnenenergie, Verlag GmbH Munich, pp. 45–58, 9th Internationales Sonnenforum, Stuttgart 1994.
3. ^ A. Lewandowski: The Design of an ultra-high Flux solar tetst capability . In: Proc. Intersociety Eng. Conf. IECEC-89, Washington DC, 1989.