Three-dimensional dynamic multi-physics modeling and long-term degradation performance analysis of solid oxide fuel cell considering carbon deposition

Carbon deposition is a critical issue in solid oxide fuel cell (SOFC) operations. In this study, a 3D dynamic model of SOFC considering carbon deposition is established and validated to investigate the effects of key operating conditions (i.e., output voltage, operating temperature, and fuel composition) on the long-term power degradation of the cell. Additionally, the total working lifecycle power generation (P_tot) of the cell is calculated for methane molar fractions in the feeding fuel (X_CH4) ranging from 0.1 to 0.4, output voltages (U) from 0.6 V to 0.8 V, and operating temperatures (T) from 1003 K to 1043 K. The results indicate that the long-term SOFC operating voltage should exceed the voltage for maximum steady-state power output to achieve higher P_tot. When the power degradation threshold (PDT) equals 0.75, P_tot reaches 2880 kW h/m² at U = 0.75V, approximately twice that at U = 0.55V. The power degradation process of the cell can be divided into two stages: a rapid degradation stage and a slow degradation stage. Decreasing the operating temperature or reducing X_CH4 to regulate PDT to the slow degradation stage can significantly enhance the cell's total working lifecycle power generation. A distinct boundary in X_CH4 is observed between high and low P_tot. When X_CH4 exceeds the boundary value (0.25), the cell's P_tot decreases by over 70 %.