Influence of pressure ratio on gas-compressed CO2 thermoelectric storage combined cycle system

In the operation of power plants, gas turbines alone cannot fully utilize heat, and in order to improve energy efficiency, solutions can be found in the high-temperature flue gas generated by gas turbines. Waste heat utilization of gas turbine is an efficient energy conversion method, which advocates the use of supercritical carbon dioxide (SCO2) to replace the traditional steam Rankine cycle. The supercritical carbon dioxide cycle has attracted much attention in the field of waste heat recovery because of its many advantages. Based on this research basis, this paper adopts the approximate Elson cycle as the carbon dioxide (CO2) cycle process in the combined cycle, aiming to improve the efficiency of circular power generation. In view of the significant effect of CO2 pressure ratio on the combined cycle, this paper will discuss its influence on the changes of the combined cycle system.In this study, EBSILON software was used to simulate the gas-CO2 combined cycle power generation system under different pressure ratios (1.2 to 2.0). The purpose of the simulation was to assess the impact of different pressure ratios on cycle performance indicators, including CO2 cycle efficiency alone, combined cycle efficiency, system cycle efficiency, energy storage density, flue gas efficiency, and primary energy efficiency. These findings are intended to provide theoretical basis for engineering practice.The results show that with the increase of pressure ratio, all evaluation indexes show an increasing trend. Specifically, when the pressure ratio rises to 2.0, the power generation efficiency of the CO2 cycle alone can reach 39.53%, while that of the gas-CO2 combined cycle can reach 43.93%. In addition, the system's cycle electrical efficiency increased to 40.37%, energy storage density increased to 68.55 kW/m³, flue gas utilization rate increased to 44.1%, and primary energy utilization efficiency also increased to 44.43%.