Thermodynamic Analysis of a Transcritical Carbon Dioxide Energy Storage System

Under the background of the rapid development of energy storage technology, a transcritical carbon dioxide energy storage (TC-CES) system based on liquid and supercritical storage is proposed. The system has the advantages of high energy storage density, no geographical restrictions, and promoting carbon dioxide emission reduction. To explore the mechanism of the working parameters of TC-CES system on the thermodynamic performance, a mathematical model of the system was established. Using Aspen plus and MATLAB software to simulate the process, the thermodynamic characteristics of the system are analyzed, and the influence of energy storage pressure and energy release pressure on the energy efficiency of the system is deeply studied. The results show that the cycle efficiency of the system is 53.8%, the energy storage density is 21.1kW•h/m
³
, and the heat utilization efficiency is 77.9%; The energy storage pressure has different effects on compressors and turbines of different stages; When the energy storage pressure increases from 12MPa to 26MPa, the energy storage density increases but the cycle efficiency decreases gradually, but there is an inflection point at 24MPa; By reducing the energy storage pressure to 12MPa, the maximum cycle efficiency is 55.6%; The increase of energy release pressure is beneficial to improve the cycle efficiency, but attention should be paid to the selection of energy storage density.