The performance and durability of eight types of modern aluminum based solar selective absorber coatings was studied. The combined effect of high humidity (95 % RH), condensation and temperature (40 °C and 60 °C) was assessed. Optical, microstructural and elemental composition modifications after ageing were studied using FTIR spectrometry (Bruker IFS66), transmission electron microscopy (TEM, FEI Talos F200X) coupled with energy dispersive X-ray spectrometry. The study has shown that for the tested absorber surfaces, the predominant degradation process is not the formation of aluminum hydroxide, but the reduction of the antireflective layer thickness.

SPF Institute for Solar Technology