Techno-economic analysis and comprehensive optimization of an on-site hydrogen refuelling station system using ammonia: hybrid hydrogen purification with both high H2 purity and high recovery

Ammonia (NH3) has been considered to be a promising hydrogen storage medium owing to the carbon-free features, easy liquefaction storage, low transportation costs, and potential ammonia production from renewable energy sources. On-site hydrogen production using ammonia decomposition offers a sustainable and cost-efficient solution for hydrogen refuelling stations, and separating H-2 from a H-2-N-2 mixture is a necessary step to obtain high-purity H-2 (>99.97%). In the scale of a hydrogen refuelling station (similar to 300 Nm(3) h(-1)), using pressure-swing adsorption (PSA) is not feasible owing to its low recovery, while using polymeric membranes cannot meet the H-2 purity demand. To achieve both a high H-2 purity and high H-2 recovery, we developed a physical-chemical system model of a 300 Nm(3) h(-1)on-site NH3-fed hydrogen refuelling station to optimize a H-2 purification subsystem, and furthermore predicted the system efficiency and economic feasibility. We validated our system model using experimental data, and compared eight different scenarios of H-2 purification subsystems. The results reveal that a NH3-fed on-site hydrogen refuelling station using a "PSA-to-membrane" subsystem is a feasible method of producing high-purity H-2 with a H-2 recovery greater than 95%, which is 29% higher than a system only using PSA. Correspondingly, the system efficiency increased from 59.1% to 85.37%, and the total specific cost was reduced by 22% to 4.31 euro per kg. The feedstock cost accounts for 74% of the total specific cost. Using our optimized hybrid H-2 purification subsystem, the H-2 production cost of the NH3-fed on-site hydrogen refuelling station was at least 15% lower than other carbon-free routes (such as electrolysis, solar thermolysis, photo-electrolysis, etc.), and comparable to that of a methane steam reforming system with carbon capture and storage.