Comprehensive comparative study of two novel isobaric adiabatic compressed air energy storage systems coupled with pumped hydro storage

In the context of achieving carbon neutrality, the compressed air energy storage (CAES) technology has experienced considerable development in recent years. This is because it can mitigate the negative impacts associated with the large-scale integration of renewable energy into the electricity system. However, the traditional advanced adiabatic CAES (AA-CAES) system suffers from a significant exergy loss due to the air throttling process that is inherent in its operation. To address this issue and enhance system performance, two novel isobaric adiabatic compressed air energy storage systems coupled with pumped hydro storage are proposed: isobaric adiabatic compressed air energy storage with high backpressure pumped hydro storage (HPPHS-IA-CAES) system and isobaric adiabatic compressed air energy storage with pumped hydro storage aided compression (PHSAC-IA-CAES) system. In these two systems, the air throttle is eliminated and the stored air can be fully released at a constant high-pressure, which increases the round-trip efficiency and energy storage density of the system. Comparative studies are conducted from the perspectives of energy, exergy, exergoeconomic and techno-economic analyses to verify the feasibility of the proposed systems. Thermodynamic analysis results indicate that the round-trip efficiency and energy storage density of the HPPHS-IA-CAES system can reach 74.73 % and 5.31 kWh/m(3) under the design condition, respectively. This is superior to the performance of the PHSAC-IA-CAES system (68.64 % and 4.19 kWh/m(3)) and the AA-CAES system (65.73 % and 4.71 kWh/m(3)). Techno-economic results reveal that the dynamic payback period of the HPPHS-IA-CAES system is 2.42 years, which is 0.06 years and 1.47 years shorter than that of the AA-CAES system and the PHSAC-IA-CAES system, respectively. Multi-objective optimization results demonstrate that further improvements in system performance can be achieved through optimization.