Effect of metallic reflectors and surface characteristics on the productivity rate of water desalination systems

Abstract The objective of this research is to determine the best metallic reflector for parabolic trough solar collectors of water desalination units. A group of materials have been selected and tested for their reflectivity. These materials were; aluminium foil of thicknesses 6 μm and 86 μm, and sheets of 1mm thickness made of aluminium, galvanized steel, copper and stainless steel. An experimental setup has been constructed to examine the performance of the parabolic trough as a function of the reflecting surface. The experimental setup consists of an artificial sun, parabolic trough solar collector with an evacuated tube located in the focal point of the trough and a desalination unit. The influence of the different reflectors, in terms of reflectivity, on the performance of the collector and the desalination unit were examined. It has been found that both the material type and surface roughness affect the reflectivity of the surface, and that the highest desalination rate is obtained by the aluminium foil of thickness 6 μm that has the lowest surface roughness Ra 0.04 μm and highest reflectivity 93%. The heat energy output from a parabolic trough using an evacuated tube at its focal line is linearly proportional to its reflectivity.