Optimum conditions for a solar still and its use for a greenhouse using the nutrient film technique

Abstract

A study was made on optimizing conditions in solar distillation units for increasing the yield of purified saline or brackish waters for agricultural user in a greenhouse. Two identical solar still units located at the Solar Energy Laboratory of the American University in Cairo were used to study the effect of water depth, water color, reflectors, a floating surface and addition of charcoal pieces. Using one unit as a reference unit and the other as a test unit, optimum water depth was found to be 3 cm; production increased by 39% using a red dye and 70% with a black dye. Use of reflectors was found to enhance productivity by 68%. The optimum density and thickness of floating surfaces (black sponge sheets) was 20 kg/m 3 and 3 mm thick with a productivity factor of 140%. After testing the effect of each parameter individually, the optimum parameters were combined and tested together. The productivity factor was found to be 211% using black dye, a reflector and adding large charcoal pieces. The solar still unit was mounted on a greenhouse and the integrated system tested using the Nutrient Film Technique. The distilled water output was adequate for the greenhouse agriculture and drinking water.