Highly-integrated and Cost-efficient Ammonia-fueled fuel cell system for efficient power generation: A comprehensive system optimization and Techno-Economic analysis

Abstract Ammonia (NH3) has been considered as a promising hydrogen storage media due to the features of low saturated vapor pressure at room temperature, high hydrogen content, low costs of transportation and storage, and carbon-free emission·NH3 can decompose into a gaseous mixture compromising of 75 vol% H2 and 25 vol% N2 in an NH3 decomposition reactor, which can integrate with a proton exchange membrane fuel cell (PEMFC) into one compact system, called as an indirect ammonia PEMFC (IA-PEMFC) system. IA-PEMFC systems are applicable for distributed power systems, vehicle and marine applications. In this study, we develop a physical–chemical model of an IA-PEMFC system, and perform a comprehensive techno-economic analysis to optimize IA-PEMFC system layout and improve its energetic, exergetic and economic performance. Results indicate that using our self-developed Ru/C NH3 decomposition catalyst can reduce operating temperature to less than 500 °C with remarkable stability, at least 300 °C lower than current commercially-available Ni-based catalyst, which can help the IA-PEMFC system to save heat supply by 29%, leading to an improvement of 2 points of percentage in energy efficiency. Recycling and burning tail gas from PEMFC anode are an effective pathway for better heat integration, and can significantly enhance system efficiency by about 11% to 56.1% when average cell voltage is 0.7 V. An auto-thermal reactor integrating NH3 decomposition and H2 catalytic combustion can further improve system efficiency by 0.5 points of percentage to 56.6%, and the exergy efficiency increases to 49% correspondingly. Economic estimation reveals fuel cost of our optimized IA-PEMFC system reaches 0.13 $/kWh for power generation and 0.024 $/km for vehicle application, respectively. In contrast, a carbon-free IA-PEMFC system is more economically efficient than ones using gasoline-fueled heat engines and H2-fueled PEMFC, and highly competitive in both energy efficiency and economic feasibility to indirect methanol PEMFC system (with end-user CO2 emission).