Design and performance of a simple single basin solar still

The lack of potable water poses a big problem in southern and south-western arid regions of Pakistan. The underground water, where exists, is usually brackish and cannot be used as it is for drinking purposes. Pakistan lies in high solar insolation band and the vast solar potential can be exploited to convert saline water to potable water. The most economical and easy way to accomplish this objective is using solar still. A simple single basin solar still was designed for 33.3° N latitude. The optimum inclination of glass cover was calculated to be 33.3o for both summer and winter. The average daily output of solar still based on data of 8 days in July 2004 was found to be 1.7 liters/day for basin area of 0.54 m2. Efficiency of the still was calculated as 30.65% with a maximum hourly output of 0.339 liters/hr at 1300 hrs. The drinking water coming from Simly dam filtration plant, Islamabad was desalinated in the solar still. The total dissolved solids (TDS), conductivity and pH of this surface water were measured as 370 ppm, 1.291 mS/cm and 6.72 before desalination and 30 ppm, 41 μS/cm and 6.5 after desalination respectively. The ground water of PIEAS colony, Islamabad was also desalinated and results obtained were 544 ppm, 1.668 mS/cm and 6.78 before desalination and 84 ppm, 31 μS/cm and 5.74 after desalination. A lab-prepared water sample was desalinated as well and results were, 17663 ppm, 85.3 mS/cm, 7.58 before desalination and 226 ppm, 88.5 μs/cm, 6.13 respectively, after desalination. The values for TDS and pH agree with the WHO guidelines for drinking water quality.