Thermal Analysis of Flate Plate Collector of Active Solar Stills

Solar distillation is the process of getting potable water by harnessing solar energy with the help of solar still which imitates the natural hydrological cycle with the difference that cycle is closed. Potable water is one of the basic requirements for the survival of organisms on the planet earth, However, water has been contaminated badly due to rapid industrialization, fast growth in agriculture and population all over the world. There is going to be lack of potable water in years to come if this problem is not addressed properly as reported by many researchers. In this circumstance, exploitation of the solar energy for electricity generation and distillation could be better alternative to mitigate the imminent problem of shortage of energy and potable water to a greater extent. The basin type passive and active solar stills have been investigated in the current study on the basis of energy matrices, exergoeconomic parameter, enviroeconomic parameter, productivity and various efficiencies. Its main motive is to offer better solar distillation system to turn out potable water at competitive price. Apart from the conventional solar distillation systems, various other solar distillation systems coupled with (a) N- identical partially covered photovoltaic thermal (PVT) flat plate collectors (FPC), (b) partially covered PVT compound parabolic concentrator (CPC) collectors and (c) evacuated tubular collectors (ETC) have been studied in detail. The thermal model has been developed for the proposed system. The life cycle cost analysis of various basin type solar distillation systems has been carried out by incorporating the effect of energy payback period. Four different types of weather conditions viz. [a, b, c and d] type for each month of year have been considered for the exhaustive computation of yield, energy output and exergy gain at optimum number of collectors and mass flow rate followed by computation of exergoeconomic parameter, enviroeconomic parameter, productivity and various efficiencies. Generally, exergoeconomic parameter is computed as exergy loss per unit cost for systems like mechanical, thermal etc. as reported by several researchers. However it has been proposed to be computed as the exergy gain per unit cost because of the fact that nothing has to be paid against the input (solar energy) to solar system. Also same input cannot be provided to different solar distillation systems while making comparison. The comparison of various solar distillation systems has been carried out at 0.14 m water depth, optimum number of collectors and optimum mass flow rate for the composite climate condition of Ghaziabad U.P, India. The production cost of water in ₹/kg and production cost of electricity in ₹/kWh have also been computed. The performance analysis viz. hourly productivity and various efficiencies of solar distillation systems have been carried out at optimum number of collectors and mass flow rate by incorporating the effect of water depth for two different months (June (summer) and January (winter). It has been concluded that double slope ETC active solar distillation system gives the best performance on the basis of energy matrices and production cost of water. Further double slope PVT-FPC active solar distillation system has been found better than other systems under consideration on the basis of enviroeconomic parameter and annual productivity (exergy based); however, the value of exergoeconomic parameter and energy based annual productivity is highest for double slope ETC active solar distillation system. On the basis of average daily electrical efficiency and average daily overall thermal efficiency, double slope PVT-FPC active solar distillation system gives the best performance; however, double slope PVT-CPC active solar distillation system performs best on the basis of average daily exergy efficiency, overall exergy efficiency and productivity among all active solar distillation systems under consideration. Moreover, double slope ETC active solar distillation system has been found to perform best among all active solar distillation systems under consideration on the basis of average daily thermal efficiency. At last, proposed solar distillation systems has been carried out followed by conclusions and recommendations.