ACCELERATED AGING TESTS OF ABSORBER COATINGS FOR UNGLAZED METALLIC SOLAR COLLECTORS

摘要

During the expected minimum life-span of 20 years, the absorber coating of unglazed thermal solar collectors is directly exposed to different stresses like heat, rain and ice. With increasing application possibilities for this type of collectors (e.g. for borehole regeneration), there is a need for the quality certification of absorber coatings. However, there is no standard procedure available to assess the durability of spectrally selective coatings for unglazed collectors. Existing aging tests (ISO 22975-3) are designed for absorber coatings used in glazed solar collectors, where the degradation loads (e.g. for humidity and condensation) are very different. Preliminary steps for developing an accelerated lifetime testing procedure are presented. First results showing the optical performance after aging of two spectrally selective absorber coatings on stainless steel are reported.