Mohammad Dashtban - Department of Chemical Engineering, University of Sistan and Baluchestan, Zahedan, Iran
Hamid Moghaddam - Department of Chemical Engineering, University of Sistan and Baluchestan, Zahedan, Iran
Farshad Farshchi Tabrizi - Department of Chemical Engineering, University of Sistan and Baluchestan, Zahedan, Iran

Provision of fresh water is a major problem in remote areas and arid zones. Passive Solar still is one of the many apparatus that can be widely used for water purification in mentioned areas when the climatic conditions is fair and the demand is not too large. Passive solar stills are broadly divided into basin and inclined types. In this paper, two cascade solar stills were constructed with and without latent heat thermal energy storage system (LHTESS). Paraffin wax is selected as phase change material (PCM) that acts as a LHTESS. Using weir on each step of stills leads to forced flow of inlet water and increases in its residence time in the stills. Furthermore, a thin layer of water covers completely the evaporation surface and prevents to spots dry upon it. Thermal performances of stills were compared in typical sunny and partially cloudy days. The results showed that nearly the same values of total productivity are obtained for stills with and without LHTESS in sunny day. On the other hand, a significant difference was observed in total productivity when the stills operated in partially cloudy day. Hence, still without LHTESS is preferred for sunny areas because of its simplicity and low construction cost.

Desalination, Solar stills, Cascade solar still, Phase change material, Productivity