Performance investigation of solar-assisted supercritical compressed carbon dioxide energy storage systems

Energy storage technology plays a vital role in realizing large-scale grid connection of renewable energy. Compared with compressed air energy storage system, supercritical compressed carbon dioxide energy storage (SC-CCES) system has the advantages of small size and high energy storage density. In this paper, two solar-assisted supercritical compressed carbon dioxide energy storage (SASC-CCES) systems are proposed. One is coupled with simple regenerative compression cycle (SR-SASC-CCES), the other with recompression cycle (RC-SASC-CCES). Thermodynamic and economic analyses are carried out. The results show that the energy efficiency of the system is higher than that of other organic working fluids when the transcritical CO2 is used as the working fluid of the bottom cycle due to the residual heat available in the energy storage system of the recompression cycle. Compared with the baseline SASC-CCES system, the SR-SASC-CCES system and RC-SASC-CCES system are more conducive to improving the solar energy utilization rate, and their photoelectric conversion efficiencies are 23.56 % and 28.77 %, respectively, 2.63 % and 7.84 % higher than that of the baseline SASC-CCES system. Increasing the inlet temperature of turbine 1, energy storage pressure and energy release pressure can effectively increase the energy efficiency, solar-electricity conversion efficiency, exergy efficiency and energy storage per unit volume of these two systems. In addition, the RC-SASC-CCES system has better economic performance, whose dynamic investment recovery period is about 6.8 years. The 20-year net present value (NPV) is 23,456.16 k$, 7956.69 k$ higher than that of the SR-SASC-CCES system.