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

Abstract

In this study, the preparation of the composite material consisting of expanded vermiculite (EV) and potassium carbonate (K2CO3) was conducted using a solution impregnation method. Sorption and desorption experiments were undertaken to investigate the dynamic and thermodynamic properties of the EV/K2CO3 composites with varying salt contents. The findings suggest that the EV/K2CO3 composites effectively address the issues of solution leakage resulting from the deliquescence and excessive hydration of pure K2CO3 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/K2CO3 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 EVPC40 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/m3, respectively. In comparison to pure K2CO3 salt, the utilization of EV/K2CO3 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/K2CO3 composites within thermochemical energy storage systems.