PERFORMANCE EVALUATION OF TWO DEFFERENT ACTIVE SOLAR STILLS

Abstract

The main goal of this work is evaluating the performance of two solar desalination systems under active mode using an integrated solar flat plate collector (FPC). The first one included a glass covered pyramid solar still (PSS) combined with FPC, whilst the second is consists of a greenhouse solar still (GSS) with the same area of brine basin and provided with transparent acrylic cover and connected to another similar FPC. The two systems were fully powered by solar energy using photo voltaic (PV) system. The pre-experiment was performed to evaluate the thermal performance of FPC to determine the optimum hot water flow rate to be used in the main experiment. The main experiment aims to investigate the performance of the two active solar stills under different brine depths and salinity levels. The effect of using basin auxiliary materials including black wick clothes (BWC) and black rubber mat (BRM) on the performance of solar stills was studied with taking into consideration the performance indicators. The obtained results revealed that, the water flow rate of 0.30 l/min achieved the highest values of maximum and average thermal efficiency for the solar FPC. Furthermore, there was no remarkable difference in the hourly productivity and accumulated yield for active PSS and GSS under the best operating condition of brine depth 1cm, salinity level 10000 ppm using BWC and water flow rate 0.30 l/min. Nevertheless, the instantaneous efficiency of active PSS was higher than active GSS, particularly at noon. The cost of distilled water unit is approximately equal for both stills. In conclusion, the two designs of stills proved a good performance with advantages of lightweight, durability and formability for the transparent acrylic cover of GSS over the fragile glass cover of PSS.