Performance Analysis of Vermiculite–Potassium Carbonate Composite Materials for Efficient Thermochemical Energy Storage

In this study, the preparation of the composite material consisting of expanded vermiculite (EV) and potassium carbonate (K 2 CO 3 ) was conducted using a solution impregnation method. Sorption and desorption experiments were undertaken to investigate the dynamic and thermodynamic properties of the EV/K 2 CO 3 composites with varying salt contents. The findings suggest that the EV/K 2 CO 3 composites effectively address the issues of solution leakage resulting from the deliquescence and excessive hydration of pure K 2 CO 3 salt, thereby substantially improving the water sorption capacity and overall stability of the composite materials. The salt content plays a vital role in the sorption and desorption processes of EV/K 2 CO 3 composites. As the salt content rises, the resistance to sorption mass transfer increases, resulting in a decline in the average sorption rate. Concurrently, as the salt content increases, there is a corresponding increase in the average desorption rate, water uptake, and heat storage density. Specifically, at a temperature of 30 °C and a relative humidity of 60%, the EVPC 40 composite with a salt content of 67.4% demonstrates water uptake, mass energy density, and volumetric energy density values of 0.68 g/g, 1633.6 kJ/kg, and 160 kWh/m 3 , respectively. In comparison to pure K 2 CO 3 salt, the utilization of EV/K 2 CO 3 composites under identical heat demand conditions results in a 57% reduction in the required reaction material. This study offers essential empirical evidence and theoretical backing for the utilization and development of EV/K 2 CO 3 composites within thermochemical energy storage systems.