Thermo-economic analysis and evaluation of a novel super/trans-critical CO2 Carnot battery based on partial condensation and recompression

The CO2-based Carnot battery, known for its high efficiency, significant energy density, and low construction costs, is a promising solution for large-scale physical energy storage. However, conventional CO2-based Carnot batteries face challenges, such as condensation issues and limitations in cycle structure. Integrating medium-temperature waste heat (>150 °C) can improve their round-trip efficiency, but a comprehensive thermo-economic analysis of CO2-based Carnot batteries remains underexplored. To address these challenges, this study proposes a novel trans-critical CO2 partial-condensation and recompression Carnot battery, utilizing a binary CO2-based zeotropic working fluid to mitigate condensation issues in the trans-critical CO2 cycle. Performance comparisons were made against the traditional supercritical CO2 recompression Carnot battery under various operating conditions. Additionally, a thermo-economic analysis was conducted for the CO2-based Carnot battery. The results show that the trans-critical CO2 partial-condensation and recompression Carnot battery achieves an 11.82 % improvement in round-trip efficiency compared to the traditional supercritical CO2 recompression Carnot battery. In scenarios with high waste heat stream's mass flow rate, significant disparities between peak and off-peak electricity prices, and longer off-peak durations, the trans-critical CO2 partial-condensation and recompression Carnot battery also demonstrates a shorter payback period.