Energy, exergy and economic analysis of an air cavity appended passive solar still of different basin material at varying depth

Abstract

Developing countries are severely affected by water scarcity. To meet the growing demand for clean drinking water, minimal, small-scale methods that don't use much energy are needed. Saline water desalination utilising the solar still, which depends only on solar radiation, is a realistic option for rural coastal communities. The current research focuses on increasing the daily production of solar still distillate yield. This paper provides a modified design that incorporates an air cavity connected to a solar still absorber plate and an effort to calculate the solar stills technological and economic assessment. The current study extensively focuses on the usefulness of an air cavity in improving solar still performance under diverse climatic conditions. The experimentation was performed at varying depths of saline water in two different material solar stills. During the experimentation, the maximum saline water temperature observed was 89°C and the lowest temperature was found as 29 °C. Aluminium and polycarbonate stills had an average energy and exergy efficiency of 48.8 %, 3.44 %, and 42.4 %, 2.3 %, respectively. The daily yields for aluminium and polycarbonate stills were 2.8 to 3.8 l/m2/day and 1.8 to 3.4 l/m2/day, respectively. The cost per litre of the distillate from aluminium and polycarbonate stills was determined to be Rs. 0.723 and Rs. 1.361, respectively, with a payback time of 10 and 11 months. Overall, at 1.8 cm saline water depth, the aluminium still provides improved distillate yield than the polycarbonate still, and the addition of air cavity reprises in the improvement of the efficiency of the solar still. From the experimental findings of both the solar stills, we can conclude that they are long-term viable and cost-effective in producing more distillate than expected with a short payback time.