Experimental investigation on a double-slope solar still with partially cooled condenser in the region of Ouargla (Algeria).

Abstract The population of Algeria is expected to double in the next thirty years, by then it will clearly face serious water shortages. The demand in water for drinking, agriculture and industry largely exceeds the amount that fresh sources can meet, especially in the Saharan regions where rainfall is the lowest, with years of total drought. To overcome this serious water scarcity, solar desalination could be an effective solution. Solar distillation is one of the simplest techniques used in water desalination. This investigation presents an experimental study using a double slope solar still. This choice is justified firstly by the abundance and low price of solar energy, and by the simplicity of installation and easy maintenance of these devices. The main aim of the present work has been to enhance the yield of the still by improving the performance of its condenser. This was achieved by cooling its outer surface. Small-scale solar powered distillation pilot units have been constructed and operated. The tests were conducted in the town of Ouargla, south of Algeria. Two series of experiments were performed. In the first series, the condenser was cooled by flowing water on the north glass cover throughout the run. This enhanced the still productivity by 11.82%. The second series consisted of lowering the glass temperature (condenser), and this was realised by an intermittent shading (12 h.00-14 h.00) of the north glass cover. The shade was assured by placing a rectangular screen at 90 cm above the north side of the still. This procedure improved the yield by just 2.94%.