Thermophysical Performance of BN- and KNO₃-Doped Ca(OH)₂ and Mg(OH)₂ for Medium-Temperature Thermochemical Energy Storage Applications: A Comparative Study

Pure calcium hydroxide, Ca(OH)2, and magnesium hydroxide, Mg(OH)2, are limited in their applicability for the storage of medium-temperature heat due to their high dehydration temperatures. Modification of the hydroxides by doping with appropriate materials is a viable method for solving this problem. In this work, samples of Ca(OH)2 and Mg(OH)2 have been doped with various proportions of Boron Nitride (BN) and Potassium Nitrate (KNO3) to reduce their dehydration temperatures. The results showed that the doping processes were successfully achieved as desired, but there was a reduction in their surface areas and porosity, which could impact their thermodynamic behaviour. However, the thermal analysis on the samples revealed that the KNO3 had a more positive effect on the Mg(OH)2 material than Ca(OH)2. For instance, a reduction of 23 ℃ in the dehydration temperature and an increase of 6% in heat storage capacity were achieved with 5 wt% KNO3-doped Mg(OH)2, thus making it applicable for heat storage in the temperature range of 293–400 ℃. Thermodynamic and kinetic studies on this composite material are therefore encouraged to establish its full potential.