Spectrally selective copper sulphide coatings

Abstract

In the present investigation, copper sulphide films were chemically deposited on aluminium substrates and their optical properties were studied for their application in photothermal conversion of solar energy. The films are stable, have good adhesive properties, are fairly uniform and found to possess spectral selectivity. The maximum solar absorptance α s (0.89) and minimum thermal emittance ϵ T (0.25) are found for a film deposited at 250°C and having thickness of 1.6 μm. The selective coating gave a stagnation temperature of 124°C which gives the improvement in collector efficiency of 17% over the black paint. The films are found to be stable up to 200°C. Different aging tests such as temperature stability, temperature cycling and ultraviolet irradiation have been done. The films essentially provide a low cost selective coating for photothermal conversion of solar energy. The cost of the coating per square meter area has been estimated to be around $2.5.