Thermo-economic analysis of a combined cooling, heating and power system based on self-evaporating liquid carbon dioxide energy storage

• A polygeneration system based on liquid CO 2 energy storage is proposed. • A self-evaporating method for carbon dioxide is involved. • The thermodynamic and economic performances are executed. • Low storage pressure near the critical value is suggested. • The proposed system is superior to the systems with similar nature. Renewable energy will play the hard core in the future energy consumption structure. However, presently, the penetration rate of renewable electricity in power grid is put to limit by the nature of intermittent and volatile. Compressed carbon dioxide energy storage is a promising way to smoothen the fluctuations. In order to realize the evaporation process without heat source in charging process and satisfy the diversified energy demands, a combined cooling, heating and power system based on liquid carbon dioxide energy storage system was proposed in this paper. An ejector refrigeration cycle was coupled to recycle the waste heat, and a self-evaporating method was presented on the basis of flash distillation. Parametric analysis was carried out to evaluate the influence of several key parameters on system’s thermal and economic performances. Results indicated that the roundtrip efficiency and energy density of the system were 64.97% and 17.46 kWh/m 3 under design conditions. Besides, increasing the turbine inlet parameters improved the system efficiencies and amplified the system storage capacity prominently, but it had negative effect on the cooling power. The optimum value of low pressure storage tank was around critical point in terms of system thermal efficiency and heating power, while entrainment ratio dominated the behavior of the cooling power. Moreover, economic performance of the proposed system was advantageous in the large-scale energy storage systems.