Research on power generation and waste heat utilization performance of a novel gas-CO2 combined cycle

To enhance the utilization rate and quality of waste heat from gas turbine flue gas, this paper proposes a gas-CO2 combined cycle power generation system based on the principle of the Ericsson cycle. The system comprises a CO2 cycle power generation system and a gas turbine power generation system. The CO2 cycle utilizes the waste heat flue gas discharged from the gas turbine for power generation, employing an approximate isothermal process and an isobaric process, following the Ericsson cycle principle. Furthermore, the combined system can utilize off-peak electricity for energy storage through CO2 storage tanks. This paper constructs a simulation model of the gas-CO2 combined cycle power generation system using simulation software. Based on the validation of the simulation's effectiveness, the performance of the gas-CO2 combined cycle system, which is based on the approximate Ericsson cycle, and its parameter-dependent behavior are explored. The results indicate that increasing the CO2 mass flow rate within a certain range significantly enhances system power generation efficiency. However, the efficiency tends to stabilize at excessively high flow rates. Increasing the compressor pressure ratio does not significantly affect the overall system power generation efficiency, while an increase in ambient temperature leads to a decrease in gas turbine load, thus impacting system power generation efficiency. Conversely, increasing the gas turbine load ratio can significantly improve the combined cycle system's power generation efficiency and the contribution of the CO2 cycle. Compared to a single gas turbine, the combined system significantly improves overall power generation efficiency. At a full gas turbine load of 3387 kW, the maximum power generation efficiency of the gas-CO2 combined cycle is 30.21 %, with the CO2 cycle contributing 4.04 %. At this point, the flue gas waste heat utilization efficiency reaches 33.34 %. This system provides a viable solution for waste heat utilization and energy storage in small- and medium-sized energy supply systems.