Experimental investigation on thermodynamic and kinetic of calcium hydroxide dehydration with hexagonal boron nitride doping for thermochemical energy storage

Abstract Thermochemical heat storage is a promising candidate due to its high energy densities and the possibility of long-term storage in the areas of waste heat recovery and renewable energy utilization. In this work, hexagonal boron nitride (HBN)-doped calcium hydroxide has been prepared by ultrasonic and mechanical agitation. Thermodynamics, kinetic and cycling stability of HBN-doped composites as well as the pure calcium hydroxide are investigated by thermogravimetric analysis, differential scanning calorimetry, thermal constant analyzer and scanning electron microscope. The obtained results show that the thermal conductivity of the materials has been improved with HBN doping, and the dehydration enthalpy of HBN-doped composites has also been slightly enhanced in comparison to that of the pure calcium hydroxide. In addition, the pre-exponential factor and activation energy associated to the suitable kinetic models are derived for dehydration of both pure and an optimal mass content of 15 wt% HBN-doped composite. Moreover, the results of cycling stability texts indicate that HBN-doped composite shows the improved multicycle activity in comparison to the pure compound. After ten dehydration/rehydration cycles, a 67% of the rehydration conversion remains for HBN-doped composite, exhibiting competitive heat storage capacity with energy density of more than 1000 kJ/kg.