Investigation of the PCM layer thickness and heat extraction on the thermal efficiency of salt gradient solar ponds

Abstract

The salt gradient solar pond (SGSP) is a renewable energy system that absorbs solar irradiation and keeps it as heat. The application of the SGSP in the cold seasons is limited. To keep the temperature of the SGSP in cold seasons, the heat extraction rate should be reduced or the Phase Change Material (PCM) is employed. The present study investigates the impact of the PCM with a melting temperature of 56 °C on the efficiency and applicability of the SGSP. The one-dimensional model of the SGSP including the heat and mass transfer equations are modelled using the finite volume method. The results showed that the latent heat emitted from the PCM helps maintain the temperature of the LCZ layer at the melting temperature of the PCM and enhances the efficiency of SGSP during the cold seasons. The effective thickness of the PCM is investigated and showed that it depends on the heat extraction rate. Using the effective PCM thickness, the average solar pond efficiencies increase to 11.5 and 13.8 for heat extraction rates of 21 W/m2 and 25 W/m2, using a PCM thickness of 0.4 m and 0.8 m, respectively.