Parameter decoupling analysis and equipment-constrained multi-objective optimization of electrochemical–thermodynamic synergy for a SOFC–semi-closed CO2 Brayton cycle hybrid system

Abstract

To achieve efficient near–zero–carbon power generation, this study focuses on a hybrid system integrating a solid oxide fuel cell (SOFC) with a semi–closed CO 2 Brayton cycle. This configuration offers both high efficiency and inherent CO 2 capture, yet supercritical operation is constrained by the pressure tolerance limitation of planar SOFC sealing—a critical issue that remains underexplored in previous studies. To address this gap, we develop a thermodynamic model of an SOFC coupled with a subcritical semi–closed CO 2 cycle, quantifying six key parameters including steam–to–carbon ratio, anode recirculation ratio, and fuel utilization. The NSGA–II algorithm is employed for multi–objective optimization to simultaneously maximize exergy efficiency and net power output. The TOPSIS method selects both a compromise solution and an efficiency–preferred solution from the Pareto frontier. The compromise solution yields an exergy efficiency of 65.8 % and net power of 354.42 kW, while the efficiency–preferred solution gives 66.9 % and 288.73 kW. The Pareto frontier theoretically reaches a maximum efficiency of 68 % and a maximum power of 378.76 kW. Analysis of the Pareto set reveals a distinct strategy–switching mechanism. Below 370 kW, power enhancement is achieved primarily by increasing current density; however, the accompanying rises in steam–to–carbon ratio and operating temperature reduce stack voltage, leading to a gradual decline in exergy efficiency. At 370 kW, the current density hits its upper bound, and the optimization shifts to lowering the steam–to–carbon ratio and fuel utilization, which further boosts net power but at the expense of a significant efficiency drop.

The authors' abstract, as published at the source. Fuel, 2026 · DOI ↗