Exergoeconomic analysis and multi-objective optimization of a CCHP system based on SOFC/GT and transcritical CO2 power/refrigeration cycles

Abstract

A CCHP (Combined Cooling, Heating and Power) system based on SOFC/GT (Solid Oxide Fuel Cell/Gas Turbine) and transcritical CO2 power/refrigeration cycles is proposed to efficiently provide cooling, heating and power for users under the principle of energy cascade utilization. The energy, exergy and exergoeconomic analysis is conducted to assess the effects of key parameters on the system’s thermal-economic performance. The simulation results demonstrate that the cooling, heating and net electricity outputs could reach 48.37 kW, 240.65 kW and 250.95 kW with a trigeneration cost per unit exergy of 37.12$/GJ, while the power generation and exergetic efficiencies could reach 62.65% and 62.27%. The annualized capital cost, O&M cost and fuel cost are 131 549$, 90 532$ and 162 375$, respectively. The NPV and payback period of the CCHP system are 502 824$ and 12.5 years. The effects of SOFC pressure, air flowrate, refrigerant flowrate and CO2 flowrate of the transcritical CO2 power cycle on the CCHP system characteristics are discussed. Furthermore, exergoeconomic and multi-objective optimization methods are used to find the final optimum operation condition with best results. A solution set in Pareto frontier with each fitness value superior to that of the design condition is obtained after optimization. Through the decision-making process, the total energy output and the exergy efficiency increase by 35.58 kW and 0.20%, respectively, while the unit exergy cost of trigeneration rises by 0.21$/GJ.