Spectral characterisation of high temperature solar absorber coatings

Four newly developed solar absorber coatings are to be evaluated with the help of thermal cycling and optical characterisation. An initial round robin campaign reveals the need of a standardisation of the calculation procedure of solar absorptance and thermal emittance derived from optical measurements at room temperature. The implementation of a common processing of spectral hemispherical reflectance values enables a reduction of standard deviations to 0.2%, both for solar absorptance and thermal emittance. The calculation procedure proposed within this paper corresponds to DIN EN 22975-3 and enables the verification of measurement reproducibility according to ASTM E 691 - 05.