Energetic and exergetic analysis of a sloped solar still integrated with a separated heat storage system incorporating phase change material

Abstract

A single slope solar still coupled with a separated heat storage system consisting of a double glazing solar collector provided with latent heat storage material(PCM) is investigated in this paper. This system is moulded for working autonomously and continuously throughout the day. A transient model is developed for assessing the performances of this device under summer climatic conditions of the Algerian Sahara. In this model, the fraction of molten PCM was assessed at each time step, which allowed inspecting the evolution of PCM material during all the time of computations.The results indicate that the additional heat storage system supplied heat to the still for 20 h continuously during the daytime. Accordingly, it is found that the increase rates of daily and nocturnal yields were respectively 63% and 635% (an increase of more than six times) compared to the conventional system. Furthermore, it is exhibited that the useful energy is strongly influenced by the increase of PCM mass, so this parameter must be lowered as possible. Also, it is shown that in the summer season; there is an optimum tilt angle of 15° Meanwhile, it is demonstrated that a great part of the irreversibility generated in the system is caused by the solar radiation and the PCM irreversibility represents only 7% of the total irreversibility. It is also revealed that the daily irreversibility decreases slightly with increasing the water mass and collector slope angle, but possesses an optimum at a PCM thickness of 6 cm.