Modelling analysis of a solar-driven thermochemical energy storage unit combined with heat recovery

Solar-driven thermochemical energy storage (TCES) can address the mismatch between solar heat production and heating demand and contribute to decarbonisation in buildings. In many studies of typical salt hydrate TCES systems, massive heat carried by the discharged humid airflow during the charging phase is not well-utilised but directly dissipated to the ambient. Therefore, a solar photovoltaic/thermal-powered TCES system integrating a heat exchanger (PV/T-TCES-HEX system) is proposed in this study for recovering this part of heat. To study the effect of adding the PV/T collector and heat exchanger (HEX) on the performance of the TCES system, the thermal performance of the PV/T-TCES-HEX system is compared with other two TCES systems via COMSOL modelling. Results suggest that the PV/T-TCES-HEX system requires an additional external electricity input of 11.86 kWh on a typical summer day in Nottingham, which is only 40.53% of the TCES-only system. The overall thermal efficiency of the PV/T-TCES-HEX system is 56.00%, indicating an efficiency enhancement of 146.80%. A lower mass flow rate leads to higher thermal efficiency and storage energy. The system has the highest overall thermal efficiency when the reactor bed thickness is 0.04 m (57.55%) and when the reactor bed length is 0.5 m (58.73%).