Experimental investigation on sustainable cycling of thermochemical energy storage Ca(OH)₂/CaO using a pressurized air flow

The Ca(OH)₂ to CaO and water vapor reaction can be reversed and used for thermochemical energy storage, making it a highly promising method for utilizing solar thermal energy and recycling industrial waste heat. In this study, an experimental platform using a pressurized air flow was established to investigate the cyclic performance of the thermochemical energy storage Ca(OH)₂/CaO. Then a series of dehydration/hydration experiments which can be used for practical engineering was carried out, and it was found that the dehydration at a temperature exceeding 650 °C can effectively restore the cyclic performance. Subsequently, more than successive 20 cycles at below 650 °C were conducted, and the results show a decrease of 5.9 % in the conversion of the energy storage reaction after 10 cycles, followed by a continuous decrease of 3.6 % in the next 10 cycles. The thermogravimetry (TG) and particle size tests demonstrate that CO₂ is the primary factor causing cyclic performance degradation, while an excess temperature of 650 °C can effectively reduce the CaCO₃ content in the reactants. This study establishes a basis for the effective implementation of thermochemical energy storage Ca(OH)₂/CaO in engineering applications.