Thermal stability and moisture resistance of C/Al2O3/Al solar absorber surfaces

Mechanically manufactured C/Al2O3/Al solar absorber surfaces were exposed to thermal stability and moisture resistance tests following the IEA Solar Heating and Cooling Programme recommendations (draft ISO/DIS 12592). The main degradation mechanism is found to be hydration of aluminium oxide to pseudoboehmite and boehmite. We estimated the absorber service lifetime (with an optical performance more than 95% of its initial) based on two literature references, where time of wetness frequency distribution of a solar collector microclimate was measured. The estimated average service lifetime in normal use was 20 or 25 years, depending significantly on the time of wetness frequency distribution of the surface.