Comparative performance analysis of hydrogen-, methane-, and ammonia-fueled solid oxide fuel cell systems considering anode off-gas recirculation

Fuel flexibility is a key advantage of solid oxide fuel cell (SOFC) systems, but comprehensive performance evaluations across systems using different fuels, considering system-level effects, remain limited. This study conducts a comparative analysis of SOFC systems operating on hydrogen, methane, and ammonia with and without anode off-gas recirculation using validated thermodynamic simulation software (H-Twin®). In addition to comparing SOFC stack performance differences, pressure drops in heat exchangers and reformers are quantified using empirical correlations with unified component geometries, enabling assessment of fuel-dependent parasitic power consumption. For non-recirculation systems, the ammonia-fueled system exhibits the highest electrical efficiency (57.4 %), followed by the methane-fueled system (55.0 %) and the hydrogen-fueled system (50.6 %). Anode off-gas recirculation improves the electrical efficiency of the hydrogen-fueled system to 51.5 % and the methane-fueled system to 57.9 % by reducing fuel supply requirements, but slightly decreases the electrical efficiency of the ammonia-fueled system to 56.9 % due to the excessive parasitic power consumption from high recirculation flow rates. A parametric study on recirculation ratio (0.55–0.75) confirms that these fuel-dependent trends are generally preserved, while also revealing that the ammonia-fueled system may achieve higher electrical efficiency that the methane-fueled system at lower recirculation ratio, suggesting potential for improvement through fuel-specific system design optimization. These results demonstrate that optimal fuel selection depends critically on system layout and that parasitic power consumption can significantly impact the benefits of anode off-gas recirculation. • SOFC systems fueled with three types of fuel are compared on an equal basis. • Hydrogen-fueled systems exhibit the lowest efficiency regardless of recirculation. • The methane-fueled system shows the largest efficiency gain with recirculation. • The ammonia-fueled non-recirculation system shows the highest efficiency. • Recirculation may reduce electrical efficiency in ammonia-fueled systems.