Thermal Analysis of a Single Slope Passive Solar Still

Abstract

Water is an essential element for a living organism on earth. 71% of the earth’s surface is covered with water and seawater hold approximate 97% of earth’s water that is highly salty. The ratio of freshwater to salty water on earth is 1 to 40. Freshwater on earth is available in the form of rivers, lakes, in glaciers and it can be used directly. However, population growth and industrialization have resulted in high demand for freshwater for domestic, agriculture and industrial use. Also, water distribution is uneven on the earth surface. So freshwater shortage is a major problem in underdeveloped and developing nations. so desalination of the seawater is the only option left.The use of solar energy for desalination are popular choices nowadays. In the present study thermal analysis of passive single slope solar still and a still with the use of PCM (paraffin wax) via mathematical modeling is done to predict the behavior of still. Their performances are compared on the basis of the mass of distillate produced by them. It was observed from theoretical investigations that still consisting a PCM is efficient than the conventional one by up to 83%. Also, the thickness of PCM has no significant effect on productivity. With an increase in water depth from 2cm-15cm, there was loss in productivity up to 30%. Loss in productivity is due to sensible heat of water, hence lower operational values are suggested of range 2-5cm for optimum efficiency. Wind speed on glass cover has no significant effect on the productivity of still with a maximum variation of 9% for a speed range of 1-5 m/sec. Also, the slope angle is an important design parameter. The present study shows that optimum slope angle changes with the season. Optimum slope cover angle can be different for summers and winters. Slope angle should be designed according to summers as water requirement is high in summers as compared to winter.