Current status of thermodynamic electricity storage: Principle, structure, storage device and demonstration

As an efficient energy storage method, thermodynamic electricity storage includes compressed air energy storage (CAES), compressed CO2 energy storage (CCES) and pumped thermal energy storage (PTES). At present, these three thermodynamic electricity storage technologies have been widely investigated and play an increasingly important role in renewable energy utilization and power grid peak regulation. However, few literatures have reviewed and compared the three technologies. Therefore, in this paper, these three technologies are comprehensively reviewed. For each technology, the basic principle is firstly clarified, and then the system structures and storage devices are summarized. Thereafter, the corresponding demonstrations and costs of different routes are sorted out. Furthermore, a bibliometric analysis of CAES is carried out. On this basis, knowledge gaps and development directions are stated. Finally, a summary of these three technologies is made. It is pointed out that a common future development for these three technologies is to further decrease the cost. Furthermore, for CAES, D-CAES and AA-CAES are in the stage of commercialization. For other structures of CAES, most of them are still in the prototype stage, and overcoming the technical barriers is the focus of future work. For CCES, only VL-CCES has been validated in the demonstration project. For other routes of CCES, experiments are urgently required. Manufacturing and operation of key components have to be addressed. For PTES, it's more suitable in the user side. The efficient storage of heat and cooling at different temperatures is crucial for the application of PTES. Meanwhile, at the user side, how to employ the local energy to improve the performance of PTES has to be considered in the future work.