HIGH ABSORPTIVITY AL-PBS SELECTIVE SURFACES FOR SOLAR PHOTOTHERMAL CONVERSION

Low cost two layer AlPbS selective coatings for solar photothermal conversion have been produced by a chemical deposition process. The AlPbS coatings are stable at room temperature and have good adhesive properties. When cycled between room temperature and 120°C, the coatings suffer no change in their spectral absorptance. The coatings have high absorptivity in solar spectral region (0.93) and low emittance in the infrared region (0.21). The selective coatings gave a stagnation temperature of 120°C. The ultraviolet irradiation in air caused oxidation of the sulfide to sulfate. No such effect was seen on uv treatment in vacuum. The chemically sprayed two layer AlPbS provides a low cost selective coating for solar photothermal conversion. An apparatus for measuring normal emittance of solar selective coatings and low emittance metallic substrates over the temperature range 25 to 250°C to an accuracy of ±0.01 has been described. © 1979.