Investigation on Long Term Operation of Thermochemical Heat Storage with MgO-Based Composite Honeycombs

The efficient storing and utilizing of industrial waste heat can contribute to the reduction of CO2 and primary energy. Thermochemical heat storage uses a chemical and/or an adsorption-desorption reaction to store heat without heat loss. This study aims to assess the long-term operational feasibility of thermochemical material based composite honeycombs, so that a new thermochemical heat storage and peripheral system were prepared. The evaluation was done by three aspects: The compressive strength of the honeycomb, heat charging, and the discharging capabilities of the thermochemical heat storage. The compressive strength exceeded 1 MPa and is sufficient for safe use. The thermal performance was also assessed in a variety of ways during 100 cycles, 550 h in total. By introducing a new process, the amount of thermochemical-only charging was successfully measured for the first time. Furthermore, the heat charging capabilities were measured at 55.8% after the end of the experiment. Finally, the heat discharging capability was decreased until 60 cycles and there was no further degradation thereafter. This degradation was caused by charging at a too high temperature (550 °C). In comparative tests using a low temperature (450 °C), the performance degradation became slow, which means that it is important to find the optimal charging temperature.