一种新型等容-等压放电压缩CO₂储能系统的动态特性研究

Abstract Compressed CO 2 Energy Storage (CCES) is widely considered one of the most promising technologies for large-scale renewable energy grid integration. However, during its discharging process, the continuous pressure reduction in the high-pressure storage tank causes turbine deviation from the design operating point, reducing power output. To address this issue, a dynamic model of a 10 MW isochoric-isobaric discharging compressed CO 2 energy storage system (IID-CCES) is established. By utilizing the dramatic thermophysical property variations of CO 2 in the pseudo-critical region, propose an isobaric discharging model for the high-pressure liquid storage tank applicable under isochoric and isobaric conditions. This tank model precisely controls the heating process of the high-pressure liquid storage tank by recovering low-grade energy within the system, dynamically compensating for the pressure drop caused by the outflow of the working fluid, achieving isobaric discharging process. Results show that the proposed IID-CCES system achieves a round trip efficiency of 64.04 % and an energy storage density of 0.18 kW·h·m −3 under typical design conditions. Near the pseudo-critical point, a slight temperature increase can effectively maintain isobaric in high-pressure liquid storage tank, whereas away from the pseudo-critical point, continued heating has reduced effectiveness in maintaining isobaric, and the system output power drops substantially. Compared with the non-isobaric discharging process, a round trip efficiency of the isobaric discharging process is improved by approximately 8.32 %, which is primarily due to whether the outlet pressure of the high-pressure liquid storage tank is maintained constant. The isobaric discharging solution proposed in this study offers a technical pathway toward accelerating commercialization of large-scale CCES systems.