Thermal analysis of a weir-type cascade solar still integrated with PCM storage

A weir-type cascade solar still, integrated with latent heat thermal energy storage system, was designed with the view of enhancing productivity. Use of a heat storage system with 18 kg mass (2 cm thickness) of paraffin wax beneath the absorber plate keeps the operating temperature of the still high enough to produce distillated water during the lack of sunshine, particularly at night. Also, theoretical models were developed for the still with and without PCM, and the calculated results were compared with the experimental data. In addition, the internal convective heat transfer coefficient calculated from the experimental data of the still without PCM was applied for the calculations since the common relation proposed by Dunkle could not follow the still performance. Moreover, important parameters affecting the performance of the still, such as water level on the absorber plate and distance between water and glass surfaces, were theoretically investigated. The performance of the still with and without PCM was also studied on a typical day in Zahedan, Iran. In this regard, the daily productivity was theoretically found to be 6.7 and 5.1 kg/m(2)day, for the still with and without PCM, respectively. The results showed that the productivity of the still with PCM was theoretically 31% higher than that of without PCM. (C) 2011 Elsevier B.V. All rights reserved.