Thermodynamic Analysis of a Hybrid Electrical Energy Storage System Integrating High-Temperature Thermal Energy Storage and Compressed Air Energy Storage for Mitigating Renewable Energy Curtailment

Compressed air energy storage (CAES) system can smooth out the fluctuated power from renewable energy and allow it to meet electricity demands reliably. It further enables the mitigation of renewable energy curtailment. A hybrid energy storage system integrating high-temperature thermal energy storage (HTTES) and CAES is proposed. In the energy charging process, the high- and low-quality power from renewable energy are stored separately in the air storage reservoir (ASR) and HTTES system. In the energy discharging process, the compressed air is heated to high temperature in the HTTES system and finally expands in air turbines for electricity generation. Thermodynamic analysis reveals that a round trip efficiency of 64.36% with an energy storage density of 5.38 kWh m(-3) can be achieved. It is found that the proposed hybrid system has the beneficial effect of improving the system performance. The largest exergy destruction takes place in the HTTES system. The round trip efficiency is mostly sensitive to the output temperature of HTTES, the isentropic efficiency of compressors and turbines, and the maximum and minimum operating pressures of ASR.