Development and comprehensive thermo-economic analysis of a novel compressed CO2 energy storage system integrated with high-temperature thermal energy storage

This study introduces an innovative compressed CO2 energy storage (CCES) system poised to significantly enhance the management of fluctuating renewable energy sources. Unlike traditional system layouts, a high-temperature thermal energy storage (HTES), an ejector cycle and a flash process are adopted in the system and innovatively integrated into its charging and discharging process. These above methods aim to reduce geographic limitations and improve round-trip efficiency. Thermodynamic and economic models are established to conduct a comprehensive evaluation, engaging in detailed parameter analysis followed by multi-objective optimization. The analysis indicates that increasing turbine inlet pressure and temperature significantly improves system performance. While increasing flash pressure and the temperature of low-pressure storage benefit round-trip efficiency (RTE) and levelized cost of electricity (LCOE), it negatively impacts the energy storage density (ESD). Additionally, setting the ejector back pressure at approximately 7.5 MPa optimizes performance. Multi-objective analysis indicates that the optimal low-pressure storage temperature is approximately 295.07 K, with the associated flash pressure and ejector back pressure set at 3.94 MPa and 7.48 MPa, respectively. Under these conditions, the proposed system achieves the optimal RTE, ESD and LCOE of 50.43 %, 16.60 kWh/m³, and 0.0992 $/kWh, respectively. Compared to other similar systems, the proposed system exhibits preferable balance performance.