Black cobalt coatings for photothermal conversion of solar energy: Preparation and characterization

This paper presents an investigation on the optical and physical properties of spectrally selective solar absorbing coatings of black cobalt prepared by spray pyrolysis technique onto chemically brightened aluminium substrates. Advantages are low cost, reasonably good selectivity and can be scaled on collectors of any desired size. The coatings exhibit high absorptivity. $\text{α ? 0.93}$ in the “Solar” range and low emissivity, $\text{?(100°}\text{C}\text{) ? 0.22}$ in the “Thermal” range. The photothermal conversion efficiencies of black paint coated and black cobalt coated solar collectors are compared.