Thermal analysis of micro-encapsulated phase change material (MEPCM)-based units integrated into a commercial water tank for cold thermal energy storage

This paper presents a numerical analysis of a hybrid latent heat thermal energy storage (LHTES) based on a water slurry of micro-encapsulated phase change material (MEPCM) inside cylindrical modules integrated into a commercial water tank. The aim is to enhance its storage efficiency to reduce the energy usage of a water-chiller system, which provides cooling for a 150 m2 single-family house. Firstly, a 2D axial-symmetric model of a cylindrical unit with MEPCM-water slurry is developed to investigate charging/discharging processes. Numerical solutions for temperature profiles are then experimentally validated using a thermal chamber. Further, a 1D code for the water-side heat transfer simulation is developed and coupled with the previous one to perform the simulation of the whole storage system. Effects of varying cylindrical modules size and water inlet temperature are investigated. According to the results, a reduction of 2 °C in water temperature involves a 16% increase in energy stored, i.e., from 1.9 to 2.2 kWh, but simultaneously does not entail a global benefit, since the energy released is lower than the baseline, i.e., 0.6 kWh. In periodic conditions, the best solution in the module size, i.e., 1 L, ensures a contribution for the chiller system of about 0.75 kWh/day.