Numerical design and optimization of an ammonia-fueled solid oxide fuel cell (SOFC) combined heat and power system for urban heating stations

Addressing the current lack of research on efficient cogeneration optimization for ammonia-fueled solid oxide fuel cells (SOFCs) in urban energy systems, this study presents and systematically evaluates an ammonia-fueled SOFC system designed for urban heat exchange stations. An exothermic ammonia SOFC thermodynamic model was established using Aspen Plus, and four system configurations were designed. By varying key parameters such as anode off-gas recirculation (AOGR) rate, fuel utilization (Uf), and steam separation rate (Rss), the study investigated their influence on net electrical efficiency and thermoelectric ratio. It was found that AOGR effectively enhances fuel utilization efficiency, while the multi-pass heat exchanger (MH) structure intensifies waste heat recovery. The steam separation (SS) unit optimizes water vapor balance and reaction environment. Among the designs, Design D demonstrates the best overall performance, achieving a system's net electrical efficiency of 64.52% under conditions of Uf = 0.85, AOGR = 0.5, and Rss = 0.6. Multi-parameter optimization revealed that the system achieves efficient and stable operation within the ranges of Uf = 0.7–0.85, AOGR ratio = 0.4–0.8, and Rss = 0.4–0.7. Focusing on a integrated (AOGR-MH-SS) system configuration for urban heating stations—a scenario not extensively explored previously—this study conducts a systematic quantification and comparative analysis of its electrothermal performance enhancement mechanism. The results provide crucial theoretical foundations and design guidance for the engineering application of ammonia-based fuel cells in urban low-carbon energy supply and distributed energy systems.