Lithium orthosilicate/carbon dioxide/zeolite (Li4SiO4/CO2/zeolite) chemical heat pump (CHP) systems have been discussed for storage and transformation of surplus thermal energy (at ∼650°C) generated from renewable and nuclear energy systems. Tablet forms of Li4SiO4 (referred to as K‐tablets) have been developed with a new pelletizing method for practical application in packed bed CHP reactors. To understand the carbonation and decarbonation mechanisms of K‐tablets, a double‐shell model was suggested and used for explaining experimental results. Isothermal carbonation, decarbonation, and cyclic experiments were conducted under several reaction temperatures for characterization of the K‐tablet. The developed K‐tablet exhibited superior carbonation and decarbonation performance compared to pure Li4SiO4 powder at low temperatures, even when the powder was formed into a tablet shape. The K‐tablet also demonstrated enough durability and a stable reacted conversion value (Δx = 0.75) during cyclic experiments under all temperature. Higher kinetic performances of the K‐tablet than those of pure powder at 650°C and 600°C were also confirmed. The K‐tablet exhibited a high Woutput‐max of 9.82 kW/kg‐tablet at 650°C on the 10th cycle and that value was higher than that of the pure powder (3.25 kW/kg‐Li4SiO4) under the same reaction temperature. The developed K‐tablet has sufficient potential as a CHP material for heat transformation of thermal energy at 600°C to 650°C to >700°C.

The global increase in energy consumption has caused serious environmental problems, especially CO 2 emissions. In general, CO 2 is produced from the combustion and oxidation reactions at high temperature. The use of thermochemical energy storage is considered an appropriate approach to enhance the utilization of surplus or waste heat from high temperature industrial processes. So far, there are very few reports that have been published for high temperature thermochemical energy storage. In this study, high temperature thermochemical energy storage based on the lithium orthosilicate/carbon dioxide (Li 4 SiO 4 /CO 2 ) reaction was developed. A new candidate storage material was fabricated with four di erent concentrations of the potassium carbonate (K 2 CO 3 ) additive (0, 6, 11, 17, and 33 mol%), in the shape of pellets, from the point of energy density view. On the basis of the results of the carbonation and decarbonation experiments, the highest thermal output and storage densities were recorded for a pellet possessing a 11 mol% concentration of the K 2 CO 3 additive. Furthermore, this pellet, LK11, showed cyclic ability with repeat reactions over twenty cycles. Thus, LK11 pellet can be used as a thermochemical storage material because of its ability to store and release heat at high temperatures, ranging from 550 to 700°C.