Chemical Heat Storage with LiOH/LiOH·H<sub>2</sub>O Reaction for Low-Temperature Heat below 373 K

Abstract

There is a great demand on promotion of heat utilization below 373 K to establish highly-efficient energy system, because such heat is enormously unused and discharged from every process. Towards this demand, we have focused on chemical heat storage due to its high heat storage density. In this study, the promising inorganic hydrates were investigated for low-temperature heat storage with the differential scanning calorimetry. Consequently, it is found that lithium hydroxide monohydrate dehydrates at 337 K with endothermic heat of 1,440 kJ/kg-LiOH・H2O. Due to its high storage density and the simplicity of dehydration reaction, LiOH/LiOH・H2O reaction was chose as the most promising reaction for chemical heat storage below 373 K. From the chemical equilibrium calculation, this reaction system is found to be more suitable for chemical heat storage than chemical heat pump. Fundamental study of dehydration behavior of LiOH・H2O was also performed with a thermogravimetric analyzer, and the apparent activation energy of dehydration of LiOH・H2O was determined to be 51.7 kJ/mol in the conversion ranges of 0.4-0.7.