The effect of dehydration temperatures on the performance of the CaO/Ca(OH)2 thermochemical heat storage system

A more fundamental understanding of the dehydration and hydration processes of Ca(OH)2 materials is very important for the proper design and operation of thermochemical heat storage systems. There is no simple and effective method which can solve the issues of the rate of the heat storage process and the influence of CO2 on Ca(OH)2 materials. Kinetic studies have proven that a high temperature can increase the storage speed, but a high temperature will aggravate sintering of the material. The problem of carbonate formation due to contact with CO2 can also be solved by a high temperature. Therefore, how to solve the problem of the aggravation of sintering of the material after a single high temperature dehydration is important. In this study, it was found that the heat release ability can be recovered if the heat storage process of the material is applied at a lower temperature in the next cycle. Kinetic studies cannot explain the reasons of these processes. Therefore, the methods of N2 adsorption–desorption and SEM were used to reveal the effects of different dehydration temperatures on the microstructure of the materials. The results showed that the change of the micro-pore structure was the reason for the above processes. •The heat release performance can be recovered after one heat release/storage cycle.•A high/low temperature dehydration cycle can solve the issues of CaCO3 & sintering.•New nano-powder produced from the chemical reaction replaces the sintered particles.