Abstract

Solar still is one of the oldest and simplest techniques for desalination of saline water from the renewable energy i.e. solar energy. The main associated problem with the solar still is the low productivity of fresh water in comparison with the energy input from sun. Different design and operational parameters as well as heat losses are the causes of low performance ratio of this system. This report presents the synopsis of the effect of all design and operational parameters that greatly influence the productivity of still. In doing so, a mathematical model of conventional solar still on engineering equation solver has been developed which predicts the trends of all variables affecting the productivity. The model is solved for the Dhahran KSA on all inputs that are requiring for model.The study of all these effects leads to modification in design of solar still to enhance its productivity. A simple reflector is proposed on top cover of conventional solar still. The effect of all same parameters is then analyzed with this modification. A useful comparison of both cases reveals that the maximum productivity of solar still increased from 0.44 to 0.65 due to reflector. For a given day, the productivity of modified solar still increase by 90 g/h and reaches to maximum value of 230 g/h. Similarly, the presence of reflector enables to conserve energy i.e. the energy loss has been found to reduce by 16%.Other parameters that exhibit the same nature of trend for both cases are glass thickness, its temperature and slope. The model predicts that for a given inputs condition the optimum thickness of glass covering wide range of productivity here is 6 mm. Among three brine pool heights including 1 cm, 2 cm and 3 cm, maximum productivity is obtained at brine pool height of 1 cm. Seasonal effect for both conventional and modified design are widely discussed. It is found that water temperature is higher than glass temperature irrespective of the season of the year. Productivity is found to be higher in summer season than in winter season.

Keywords: Solar still; Reflector; Isotropic diffuse Model; Radiation