Potable water by solar thermal distillation in solar salt works and performance enhancement by integrating with evacuated tubes

Abstract

Solar salt farms are located in remote coastal regions where the ground water is saline. During the salt harvesting season, the salt workers face difficulties owing to shortage of potable water at-site. Nevertheless such locations are blessed with plenty of sunshine and in-situ desalination for potable water in solar distillation system or still, benefits the workers to a great extent. Since such solar stills are directly applied in field, the design and operation approach ought to be such, that water output is high and maintenance easy. In this work, we report analysis of stepped type basin still and enhancement of output by integrating with evacuated tube collectors (ETC). The average augmentation of productivity was 24% by the integration during the period of March to May 2018. The study of warm feed water charging time from ETC was an important aspect and it was found that highest production could be obtained by night-charging, due to low top glass temperature which led to increased condensation and more productivity. 8.1 L per day from 2 m2 basin area was the maximum productivity from ETC integrated unit. The novelty of the work involves incorporation of particular operational features like (a) single basin stepped tilted absorber with triangular exposure area, avoiding shadow effect; (b) distance between glass and water surface minimum for facile evaporation; (c) easy cleaning of the deposited salts by overflowing water from tilted surface; and (d) endurance of glass tubes of ETC in corrosive salty environment.