Thermodynamic, economic, and environmental analyses and multi-objective optimization of a CCHP system based on solid oxide fuel cell and gas turbine hybrid power cycle

A combined cooling, heating, and power (CCHP) system integrated with a solid oxide fuel cell (SOFC) and gas turbine (GT) is characterized by high efficiency and low carbon emission. The integration and performance optimization of CCHP systems based on SOFCs are the hot spots in the field of research. This paper conducts thermodynamic, economic, and environmental analyses of a novel CCHP system composed of SOFC, GT, Rankine cycle (RC), organic Rankine cycle (ORC), steam ejector refrigerator (SER), and heat exchanger. A mathematical model of the entire system is established, and the system performance evaluations under the design and off-design conditions are analyzed and presented. The analysis results demonstrate that the system has been designed to deliver a total of 1,000.50 kW, 32.91 kW, and 195.06 kW of cooling, heating, and electrical products. The overall energy, electrical, and exergy efficiencies of the system were 78.55 %, 65.73 %, and 61.20 %, respectively. The analysis of system parameters such as current density, fuel utilization factor, compression ratios of compressors, steam to carbon, and air flow rate on system performance are conducted to explore the reasonable design ranges of parameters. At last, a multi-objective optimization using the non-dominated sequential genetic algorithm-Ⅱ (NSGA-Ⅱ) method is accomplished to achieve the optimal performance and parameters of the system in four assumptive scenarios with different types of target weights. The optimization results indicate that the optimal system exergy efficiency is 65.15 % with the system total cost and CO2 emission being 29.25 $/h and 0.2742 kg/kWh under the equal target weighting scenario, which are improved by 6.45 %, 3.43 %, and 8.84 % compared with those of under the designed condition.