OPTICAL CHARACTERISATION OF REFLECTOR MATERIAL FOR CONCENTRATING SOLAR POWER TECHNOLOGY

In order to evaluate the quality and suitability of reflector materials for concentrating solar power (CSP) applications a measuring procedure has been developed for the determination of optical key values. These were defined for their relevance in CSP as the solar weighted hemispherical reflectance SWH, the solar weighted direct reflectance SWD within an acceptance angle of interest (25 mrad) and the specular beam diversion spec. After measuring those parameters also on artificially degraded samples, an extensive analysis of the optical material properties and comparative lifetime estimation are provided with the intention to lead to a standardized test method. Evaluation of various reflector material samples demonstrates the superiority of glass mirrors over alternative materials (polymer film, aluminium) in all concerned respects with hemispherical and direct reflectances of almost 0.94 and minimal losses after degradation. The high relevance of spectral properties as well as high mechanical resistance is emphasized.