A numerical study of direct ammonia-fuelled solid oxide fuel cells based on a transient internal cracking model

Direct ammonia-fuelled solid oxide fuel cells (DA-SOFCs) present a promising route for efficient, carbon-free energy conversion. While existing SOFC models can capture detailed cell-level behaviour, they typically lack integration of ammonia decomposition and thermal processes, limiting their suitability for system-level powertrain simulations. This study introduces a one-dimensional transient model that couples' ammonia cracking kinetics with electrochemical processes, enabling both detailed transient analysis and integration into powertrain simulations. The model investigates the effects of startup conditions, operating pressure, temperature, inlet flow rate, and fuel concentration on steady-state and dynamic performance. Results show that low current and external heating are recommended abstract for the start-up to prevent sudden voltage drop and overcome the thermal threshold for ammonia decomposition. Once steady state is reached, the cell achieves heat balance and can operate without external heating. To ensure performance, maintaining ammonia concentration above 80% and fuel utilisation over 70% is a key to avoid fuel depletion or voltage interruption during load changes. Operating pressures up to 10 atm improve power density. However, further increases offer limited benefit and require higher operating temperatures to ensure complete ammonia decomposition. This numerical model offers cell-level mechanistic insights and provides a computationally efficient basis for future DA-SOFC stack- and system-level dynamic simulations.