Thermodynamic and exergoeconomic performance assessment of a SOFC/GT cogeneration system integrating transcritical CO2 cycle and ejector refrigeration cycle

Abstract

Clean and efficient utilization of fossil fuels is becoming increasingly imperative for energy supply chains. In order to lower emissions and realize cascade energy utilization, this study proposes a novel solid oxide fuel cell/gas turbine (SOFC/GT) cogeneration system incorporating dual-stage transcritical CO₂ cycle (TRCC) and ejector refrigeration cycle (ERC) subsystems. By further utilizing the residual low-temperature waste heat, the ERC subsystem addresses the challenge of subcritical CO₂ condensation, which is difficult to manage with ambient air or water. Thermodynamic and exergoeconomic analyses are conducted to evaluate the overall performance based on the system steady-state model, where a one-dimensional SOFC model is adopted to monitor the safety status. Simulation results indicate that the system provides a net electrical output of 1228.54 kW and a heating capacity of 280.37 kW under the design condition. The net electrical efficiency, exergy efficiency, and overall energy utilization efficiency are 65.05%, 63.37%, and 79.90%, while the LCOE and payback period are 0.0599 $/kWh and 10.91 years, showing slight advantages compared to existing literature. According to simulation results, the SOFC, pre-reformer and afterburner have significant potential to enhance thermodynamic and economic performance. A sensitivity analysis of key parameters for the SOFC/GT subsystem is also performed to determine the feasible operating range from both performance and safety perspectives. In addition, the ideal working fluid for the TRCC subsystem is investigated, aiming to reduce operating pressure and improve thermal efficiency. Overall, the proposed system exhibits superior performance, providing a new configuration for efficient energy utilization and ideal economic profitability.