Experimental comparison of solar thermal desalination systems based on energy, exergy and economic (3-E) analysis

With rapid increase in human population, the demand of fresh water has been increased significantly and the world will encounter enormous water crisis by 2040. The sea contains nearly 97% of available water on earth. To fulfill the demand of fresh water, desalination of sea water can be best solution. As desalination process can be performed by using low grade energy, the use of solar energy for desalination is very popular. The most popular solar thermal desalination system is conventional solar still but its productivity is very low. In the present study, a new desalination system based on evacuated tube collectors (ETC) is developed and its performance is compared with conventional solar still experimentally. The present system consists of 15 evacuated tubes, an insulated storage tank, a heat exchanger, a condenser, and a thermic fluid as working medium. The performance of both systems is compared on the basis of daily productivity, energy and exergy efficiency, and economic viability. It is observed that the ETC-based desalination system performed better as compared to the solar still. The average energy and exergy efficiency, productivity and produced fresh water cost of desalination systems based on ETC and conventional solar still are 43.74%, 9.52%, 4.2 L/m(2)/day, 0.022 $/L and 19.23%, 1.4%, 1.975 L/m(2)/day, 0.024 $/L respectively. Further, the pay-back time for ETC based desalination system is also less (104 days) as compared to solar still (113 days).