Reduced-Order 1D Modeling of Ammonia-Fed Protonic Ceramic Fuel Cells for System-Level Analysis

Abstract

Protonic ceramic fuel cells are distinguished by fuel flexibility, lower carbon emissions, scalability, and 400–650 °C operating temperatures, addressing environmental concerns while maintaining economic viability. Ammonia has been identified as a viable PCFC fuel alternative to pure hydrogen, reducing costs associated with storage and transport due to higher energy densities at more moderate temperatures and pressures. However, pure hydrogen provides more efficient electrochemical performance, raising the question of whether reduced fuel and infrastructure costs can offset the efficiency difference. Despite the recognized potential of directly fed ammonia PCFCs, modeling efforts remain limited, with most studies relying on high-fidelity 2D/3D simulations with multi-step ammonia micro-kinetics. While accurate, these approaches are computationally intensive and impractical for system-level integration. Therefore, this work develops a one dimensional planar PCFC model with fully coupled electrochemistry, simplified in-situ ammonia decomposition kinetics, and mass and energy conservation in Python. Ammonia decomposition is represented using a thermodynamically consistent global kinetic formulation, reducing computational cost and stiffness while preserving reaction equilibrium coupling. The model is designed for integration into an Aspen HYSYS framework for system-level performance evaluation and technoeconomic analysis, with convergence stability improved through numerical regularization for efficient coupling with larger thermal-fluid simulation frameworks. ix Results are validated through ammonia decomposition kinetics and polarization curve comparisons against literature results as well as mass and energy balance consistency checks. Polarization curves comparisons indicate R2 > 0.988 and confirm predictions within 15% across all validated operating temperatures. Furthermore, the paper presents three parametric studies based on variable ammonia inlet flow rates, average cell current densities as well as inlet temperatures, quantifying trade offs in reactant utilization, thermal gradients, and peak power output. Average cell current density parametric study indicates that under defined operating conditions of the PCFC, 6500 A m-2 current density results in the highest cell power density output of 3500 W m-2. The cell experiences a sharp decrease in power output under current densities above 9000 A m-2, representing less sustainable operation. Ammonia inlet temperature parametric study indicates decomposition is strongly temperature dependent. Higher temperatures accelerate kinetics and shift the equilibrium towards products; NH₃ conversion to H₂ is more complete, sustaining electrochemical performance. NH3 utilization ranges from 9.6% at 680K to 100% at 816K.