Modelling of calcium-based energy carrier for thermochemical energy storage: From the multi-physics processes to the exothermal performance enhancement

The thermochemical energy storage system based on the CaCO₃/CaO reaction cycle demonstrates promising development potential. However, the rapid decay on the performance of Ca-based energy storage materials inhibits the application prospects of Calcium Looping (CaL) pathway. Hence, after determining the gas diffusion coefficient in the pore structure of the energy carrier based on the lattice Boltzmann method, this work established a multiphysics model of CaO energy carrier particle to enhance the exothermic performance of CaL. By coupling heat-mass transfer and gas–solid reaction process, it is shown that increasing the CO₂ concentration can enhance the heat release capacity of energy carrier, but the particle temperature can not exceed 900°C at atmospheric pressure due to the Le Chatelier’s principle. Further, the carbonation reactor should be operated in such a situation that the average temperature of the energy carrier is 50–100°C lower than the equilibrium reaction temperature, thereby facilitating enhanced energy release performance. As for modified energy carrier particles, the porosity of the outer layer greatly affects the final conversion and should be maintained at a large value. Additionally, to reduce the temperature gradient and internal temperature difference during the exothermic process, the diameter of the energy carrier should be controlled to below 0.8 mm. This work provides a series of theoretical suggestions for particle doping and condition optimization, highlighting the application opportunities of CaL.