Development of potassium carbonate-based thermochemical materials for space heating

Thermochemical heat storage is an environmentally friendly technology that can enhance energy efficiency. This study focuses on thermal energy storage capacity using the hydration and dehydration reactions of potassium carbonate-impregnated vermiculite (K 2 CO 3 /V). Because K 2 CO 3 has relatively high energy density, good chemical stability, low cost, is easy to obtain, and is nontoxic, it can be used as a thermochemical material (TCM) for domestic space heating. The challenges still remaining for practical applications are agglomeration in multiple-cycle tests and slow kinetics during hydration and dehydration reactions. This study provides insights into addressing these challenges. These problems were resolved by modifying the substrate of a K 2 CO 3 –based TCM using hydroxyapatite (HAP) and including additives such as CsF and Cs 2 CO 3 . Significant improvements were observed with a substrate including a 1:1 weight ratio of vermiculite and HAP. The improvement of reaction kinetics was achieved with K 2 CO 3 composites using additives. The synthesized TCMs were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and dynamic vapor sorption (DVS). The long-term stability was tested using 20 cycles (maximum 200 cycles) of thermal charging and discharging. The results of surface analysis, the long-term stability, high energy density, and an appropriate dehydration temperature demonstrate that our developed composite material can be used as a promising TCM.