Microstructural changes of SrBr2/H2O for thermochemical energy storage during cycling

Thermochemical energy storage (TCES) has long been explored for potential applications ranging from capturing excess heat from industrial processes to improve efficiency to storing energy in concentrated solar power plants. One promising technology is based on TCES using salt hydrates, such as strontium bromide. However, the design and up-scaling of reactors is hampered by structural changes in the reactive bulk that lead to changes in heat and mass transport. In this study, we investigate the changing microstructure of strontium bromide monohydrate using micro-computed tomography on cycled powder samples. By varying the number of cycles between 0 and 100 cycles, we study the successive change in microstructure due to cycling. We observe a complete rearrangement of the microstructure at the level of individual particles as well as at the bulk level, effectively creating a single porous solid after 100 cycles. For microstructural analysis, the solid and pore spaces were separated by image segmentation, and the resulting binarized microstructures were analyzed by several morphological measures. Finally, effective transport parameters are calculated, which give an indication of the influence of the morphological changes on the heat and mass transport within the reaction bed and consequently the reactor performance.