MAGNESIUM SULFATE HEPTAHYDRATE AS PHASE CHANGE MATERIAL IN DOUBLE SLOPE SOLAR STILL

Abstract

Solar still is best choice of utilizing freely available solar thermal energy to purify/desalinate muddy water. The driving force for this work is the inadequate availability of clean fresh water sources and the plenty of contaminated water available for probable conversion into potable water. Among various designs available, double basin passive solar still looks attractive for thermal applications in water prone and remote areas. This work presents experimental characterization of double slope solar still using phase change materials. This work aims to improve the performance (productivity of fresh water) using Mg2SO4.7H2O as phase change material (PCM). Different tests were conducted for varying mass of the PCM. For experimentation, two identical double slope solar stills (basin area of 0.5×0.5 m2) were designed, fabricated and tested for freshwater productivity. One is solar still (without PCM) and second with phase change material. A water depth of 5 cm was constant throughout the experimentation under climate conditions of Jabalpur (23° 10' N, 79° 59'E), Madhya Pradesh India. The results obtained indicate that daily distillate for solar still with Magnesium sulfate heptahydrate is higher as compared to solar still without PCM. The convective heat transfer coefficient increases during the discharging period of PCM The daily freshwater productivity of 1400, 1420 & 1400 ml/m2/day for solar still (without Mg2SO4.7H2O), while 1800, 1900 & 1960 ml/m2day for the solar still (with PCM) were recorded with addition of 0.5, 0.75 and 1kg of Mg2SO4.7H2O respectively. The overall thermal efficiency of the solar still with PCM was observed to be 64%, and for a solar still without the PCM, it was 47% while the other conditions kept constant.