Experimental investigation of a weir-type cascade solar still with built-in latent heat thermal energy storage system

Solar stills were used for water desalination in arid lands with lack of water in the fair climatic conditions. In this paper, two cascade solar stills were constructed with and without latent heat thermal energy storage system (LHTESS). Paraffin wax is selected as the phase change material (PCM) which acts as a LHTESS. Using weir on each step, causes an increase in residence time. Furthermore, a thin layer of water covers the evaporation surface and reduces channelization. Thermal performances of the stills were compared in typical sunny and partially cloudy days. Based on the obtained results, the total productivity is nearly the same for both stills in a typical sunny day. However, for a partially cloudy day, the still with LHTESS has a significantly higher productivity. So, the still without LHTESS is preferred for sunny areas because of its simplicity and low construction costs, while the still with LHTESS is proposed for partially cloudy areas due to the higher productivity. Also, the effect of flow rate on the still productivity is investigated during five sunny days. The results show that the maximum productivity is obtained in the lowest possible flow rate.