Performance of a proposed solid oxide fuel cell (SOFC)-compressed carbon dioxide (CO2) combined cycle system with thermal and electric energy storage

The combined power generation system with energy storage has higher power generation efficiency than the separate power generation. In this paper, a SOFC-compressed CO2 combined cycle system is proposed firstly, and the operating simulation is carried out by using Ebsilon software with the consideration of working fluid flow rate, compressor pressure ratio, storage tank volume, expander output work, compressor power consumption, and so on. The performance of the SOFC-compressed CO2 combined cycle system in terms of power generation rate, primary energy utilization, energy storage density and system cycle efficiency are discussed. As the pressure ratio increases, the ratio of system output work to dissipated work increases, and the power generation efficiency of the combined cycle is higher. As the pressure ratio increases from 1.2 to 2.0, the power generation efficiency of the combined cycle can be increased from 67. 12% to 74.63%. The primary energy utilization rate grew from 70.9% to 80.3%, and the CO2 power generation efficiency grew from 13.07% to 23.48%. With the increase of working medium flow rate, the more heat exchange between waste heat and working medium is, the higher waste heat utilization rate of SOFC will be obtained. The combined cycle power generation efficiency can reach 73.63%. With the capacity of the carbon dioxide storage tank increases, the power generation efficiency and energy utilization rate of the combined cycle system also increase significantly, from 66. 12% to 73.63%. The flue gas utilization rate increases from 11.8% to 34.5. The combined cycle system proposed in this paper realizes the mutual utilization and gradient utilization of waste heat and improves the power generation efficiency and energy utilization rate. The system scheme and related research results can provide theoretical support for engineering applications.