Improving the double slope solar still performance by using flat-plate solar collector and cooling glass cover

Thermal analysis, for double slope solar still, was carried out based on internal and external heat transfer and energy balance equations to predict its performance. Depending on the thermal analysis, passive and active solar stills were installed (solar still and solar still integrated with flat-plate solar collector) to use solar desalination technology for producing fresh water. Water temperature as well as both internal and external temperatures of glass cover, added to ambient temperature was measured with hour intervals, under all experimental conditions, for both solar stills. Performance of both solar stills was studied as a function of change in basin brine depth and glass cover thickness under conditions of applying glass cover cooling (flash tactic) or without cover cooling. Performance of solar stills was evaluated in terms of recorded temperatures, instantaneous and internal thermal efficiencies and system productivity. The experimental results revealed that active solar still maximizes both fresh water productivity (10.06 l/m2·day) as well as internal thermal efficiency (80.6%) compared with passive solar still (7.8 l/m2·day productivity and 57.1% internal efficiency) under conditions of 1 cm basin brine depth and 3 mm glass cover thickness and by applying flash tactic cover cooling with 5 min on and 5 min off.