Solar thermal performance of a nickel-pigmented aluminium oxide selective absorber

The solar thermal performance of a nickel-pigmented aluminium oxide selective absorber was determined by using an experimental model (prototype model). The constructed models were tested outdoors during daylight under a clear sky. Different volumes of prototypes were used. The flat-plate collector used was of the glazed type. The thermodynamic characteristics of each flat-plate collector were determined. The maximum calculated collective flux of the selective absorbers was in the range 590–699 W/m2. The maximum conversion efficiency for our systems was in the range 0.73–0.78. However, the maximum Carnot efficiency was 0.04–0.16. The absorption of merit of the samples lay in the range 0.91–0.97. The selective absorbers used have absorptivity in the range 92.0–97.0% while they have emissivity in the range 11.0–22.5%. The effects of absorptivity, emissivity, and prototype volume on the collective flux, conversion efficiency, and absorption of merit are discussed.