Modelling calcium looping at industrial scale for energy storage in concentrating solar power plants

Highlights: • Calcium looping thermochemical energy storage has been modelled at large scale. • The minimum operating load of carbonator is 23.9% due to technical limitations. • The available energy efficiency of the overall system is in the range 55–97%. • The require size to store CaO and CaCO₃ solids during 15 h is 5700–11,400 m³. Ca-Looping represents one of the most promising technologies for thermochemical energy storage. This process based on the carbonation-calcination cycle of CaO offers a high potential to be coupled with solar power plants for its long-term storage capacity and high temperatures. Previous studies analyzed different configurations of CaL integrated into power cycles aiming to improve efficiency. However, most of these assessments based on lumped models did not account for scale effect in the most critical reactor. In this work, a detailed 1D-model of a large-scale carbonator is included in the comprehensive model of the integrated facility. The results obtained served to assess the available heat, the minimum technical part load of this equipment, the required size of the storage tanks and the overall efficiency of the plant. The main issue in the operation of large-size carbonator is the heat removal, thus a multi-tube internally cooled reactor is proposed. The designed carbonator provides 80 MWth at nominal operation and 40 MWth at minimum part load operation. The sizing of storage tanks depends on the operation management, ranging between 5700–11,400 m³ for 15 h. Different efficiencies of the system were defined and presented through operating maps, as a function of the reactor loads.