Design and performance analysis of a combined cooling, heating and power system: Integration of an isobaric compressed CO2 energy storage and heat pump cycle

Decarbonization of global power generation is primarily driven by wind and solar power. However, the uncontrollable volatility and intermittency result in a low utilization rate of these large-scale renewable powers. Compressed carbon dioxide energy storage system (CCES) provides an effective path to make the renewable powers controllable and then improve the utilization rate. To further improve the system performance and broaden the application scenarios, a combined heating, cooling and power system based on the integration of isobaric CCES and CO2 heat pump cycle is proposed. In order to reduce the exergy loss of high-pressure storage, an isobaric storage container is designed on the hydraulic principle. The heat transfer feasibility in the Cooler 1 is discussed and the operation pressure boundaries are obtained under different parameters. Then, the parametric analyze of key parameters are carried out. Results show that the proposed isobaric method can improve the roundtrip efficiency from 49.36 % to 56.47 % compared to the conventional liquid storage, and the isobaric supercritical storage can reduce the CO2 condensation exergy destruction of 7.68 kJ/kg. With the increase of split ratio, the system coefficient of performance is improved from 0.56 to 2.17, but the system exergy efficiency diminishes from 56.47 % to 40.39 %. The optimal efficiency is corresponding to the turning point of thermal tank storage state, on this basis, the optimal operation map of the proposed CCES system is provided under different cases. Compared to the same type systems, the proposed system power efficiency could be 8 % higher. Moreover, the system coefficient of performance can reach approximately twice times.