Experimental investigation of a solar still equipped with an external heat storage system using phase change materials and heat pipes

In this study, a novel idea of storing the latent heat of condensing vapor in solar stills by means of phase change materials (PCMs) as a thermal storage is experimentally investigated. During the daytime, the generated water vapor by the solar energy, is conducted to an external condenser filled with PCM to be condensed. The wasted latent heat is absorbed by PCM and thereby stored. It is worth noting that there is no direct contact between the saline water and the PCM, therefore, the solar energy is not directly stored in the PCM. In the evening, the energy stored in the PCM is transferred as heat to the saline water by heat pipes and enables the desalination process to continue. Several tests were run to investigate the performance of the system. The results revealed that the presence of an external condenser filled with PCM and equipped with heat pipes in a solar still with evacuated tube collectors, makes the desalination process continue after the sunset without causing a decrease in the yield during the daytime. The yield increases by 86% as compared to the yield of the system without PCM and reaches to 6.555 kg/m2 day with the efficiency of 50%.