Numerical simulation of a combined thermochemical-latent energy storage system based on paired metal hydrides and phase change material

Abstract

The main goal of this paper is to assess the operating performance of a thermal energy storage system that combines latent and thermochemical heat storage for their utilization in industrial waste heat recovery as well as in solar power plants. Thermal energy is stored and released through endothermic desorption and exothermic absorption processes, thereby cycling hydrogen between two paired metal hydrides (MHs). The thermal performance of the dynamically coupled Mg2Fe/LaNi5 pair, which has never been investigated before, is presented in this study. Sodium acetate trihydrate is used as a PCM for the LaNi5-tank thermal management. Moreover, during the heat charging stage, the Mg2Fe-tank was subjected to a typical solar heat flux. A mathematical model has been established and utilized to simulate how the storage system would operate in practical situations. The impacts of the operating conditions, which are the efficiency of the supplied heat system, the HTF temperature, the heat transfer coefficient, and the initial temperature of the MH beds, on the storage system's performance are studied and discussed in detail. The findings from this investigation revealed that the pairing of Mg2Fe with LaNi5 at suitable operating conditions enabled the storage system to achieve a specific energy storage capacity of 2 MJ/kg of Mg2Fe and an efficiency of 87.1 %. The results of this study reveal the excellent performance of a potential and viable metal hydride pair (Mg2Fe/LaNi5) for its usage in thermal energy storage systems.