Maximization of thermal discharge power density of composite foam for thermochemical energy storage using calcium hydroxide and silicon-impregnated silicon carbide

• Numerical model for a composite of Ca(OH) 2 and Si–SiC foam was validated. • Composite with a foam porosity of 94% exhibited maximum power density. • Maximum power density at 5 min for the optimal composite was 0.97 kW L −1 . • This maximum power density was 1.6 times that of the pure Ca(OH) 2 powder. • Lower porosities inside the foam pores decrease the optimal foam porosity. The hydration of calcium oxide (CaO), a reaction that releases heat to produce calcium hydroxide (Ca(OH) 2 ), finds application for thermal discharge in thermochemical energy storage systems. Composites using CaO/Ca(OH) 2 and silicon-impregnated silicon carbide (Si–SiC) foams exhibit high performance in heat transfer. However, the optimal porosity of the Si–SiC foam and the theoretically achievable thermal discharge power density of the composite foam remain unclear. This study develops a novel numerical model of the composite in a fixed-bed reactor during CaO hydration to determine the optimal foam porosity that maximizes volumetric power density. We find that, by employing Si–SiC foam with a porosity of 94%, the thermal discharge power density at 5 min of the composite foam, with a 72% porosity inside the Ca(OH) 2 -loaded foam pores, can be maximized to 0.97 kW L −1 . This represents a 1.6-fold increase in power density over typical pure CaO/Ca(OH) 2 powder. Furthermore, we show that the optimal foam porosity decreases when higher amounts of CaO/Ca(OH) 2 are loaded into the foam pores. Our results provide a useful framework for determining the optimal porosity of thermally conductive open-cell foam in composites for thermochemical energy storage applications.