Investigation and improvement of complex characteristics of packed bed thermal energy storage (PBTES) in adiabatic compressed air energy storage (A-CAES) systems

With the application of large-scale renewable energy, power grids have put forward explicit demands for energy storage. Among the various forms of energy storage systems, the adiabatic compressed air energy storage (A-CAES) system has received more attention due to its environmental friendliness and adaptability. As a key link in the regenerative A-CAES, thermal energy storage (TES) has an important impact on the efficiency of the system. Among various forms of TES, PBTES has better economy and adaptability. However, there is insufficient research on the impact of PBTES structure on A-CAES systems. Therefore, a dimensionless governing equation for the PBTES is proposed to study the depth effect of the PBTES structure. Through comparing with the pilot-scale and industrial-scale PBTES experimental data, the maximum error of the model is 2.3%, which proves that the model has good accuracy in the simulation of different scales of PBTES. The result of research shows that: the improved thickness of the structural layer is between 0.1 m and 0.15 m. The increase in the number of cycles of the A-CAES system results in a gradual increase in system efficiency. For the A-CAES system, the round-trip efficiency is improved by 4.1%, reaching 64%, with the improvement of the wall, volume ratio, and height-to-diameter ratio of PBTES.