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Absorber coatings for collectors

The key component of a collector is the absorber and, in particular, the absorber coating. The quality of a coating is determined by two parameters: optical properties (absorptance/emittance) and resistance.

Optical properties (absorptance/emittance)

Abbildung Absorber

Absorptance and emittance measurement for wave-lengths in the range 0,3 µm – 18 µm. Determination of solar absorptance (absorptance α) through weighted integration with the AM1.5 spectrum (ISO 9845-1). Calculation of thermal emittance through weighted integration with the spectrum of a black body at a temperature of 100 °C (emittance ε).

Resistance (Task x)

Foto ALT

A coating’s optical properties determine the energy yield of the solar system. This yield should not drop noticeably over the years. In cooperation with other institutes, we have developed an accelerated method to evaluate the behaviour of such coatings as they age to ensure the stability of yield over time. This is carried out in a laboratory over a short period of time. During the tests, different measurements are made inside special climatic exposure test cabinets and high-temperature ovens intended to simulate a 25 year aging process.
Optical properties are also monitored during testing.