Indirect integration of thermochemical energy storage with the recompression supercritical CO₂ Brayton cycle

Dispatchability is a major technological obstacle for concentrated solar power (CSP) plants. Calcium looping (CaL) is a potential solution for storing solar energy for long periods using raw materials (e.g., natural limestone or dolomite) which are high energy density, widespread availability, and low cost. This study aimed to propose a CSP-CaL plant indirectly integrated with the recompression supercritical CO₂ Brayton cycle to realize carbonation under atmospheric pressure. To understand this indirect integration, the thermodynamic models are developed in Aspen and Matlab. The results show that the considered system can achieve storage exergy efficiency in the range of 8.26–16.34%, and power exergy efficiency in the range of 13.6–23.85%. In addition, a sensitivity analysis reveals that the storage exergy efficiency is largely determined by reaction temperature and conversion. Its value decreases with calcination temperature, and increases with carbonation temperature and CaCO₃ conversion. Besides, it is found that the power exergy efficiency increase with an increase in power conditions (cycle low pressure, intermediate cycle pressure, and cycle high pressure) initially. However, above a certain pressure (80, 170, 210 bar, respectively), further increase leads to a decrease in power exergy efficiency. The results also indicate that high reaction temperature has a positive effect on power exergy efficiency. Compared to the molten-salt-based and direct integration, this CSP-CaL indirect integration offers competitive performance and promising potential for the commercialization of CSP-CaL systems in the near future.