Development of fluidization technology in CaO-based cycles for thermochemical heat storage

Due to the imbalances between energy supply and demand ascribed from the inconsistency and intermittence of solar energy, thermochemical heat storage (THS) especially based on CaO/Ca(OH)₂ and CaO/CaCO₃ cycles is receiving an increasing research interest due to high heat storage density, low energy loss, low material price, and good coupling with concentrated solar power (CSP) plants. Fluidization technology shows promise for THS applications due to its high gas–solid reaction rate and heat and mass transfer efficiency, as well as its ability for continuous operation. This study reviewed the development process of CaO-based systems for THS in fluidized bed reactors. Specifically, it comprehensively analyzed and discussed: reactor configuration design for CaO-based THS; operation conditions affecting the reactor and energy storage performance; multicyclic decline of CaO activity and the solutions to improve material stability; challenges related to the use of fine CaO particles with strong cohesiveness; assisting methods for fine powder fluidization, especially involving advanced nanoparticle technology in improving the reaction and cycling performance of CaO. Further studies are needed to comprehend the complexity of the process and explore more possibilities of nanoparticle technology in THS fluidization reactors.