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

Abstract

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 H₂ from a H₂–N₂ mixture is a necessary step to obtain high-purity H₂ (>99.97%). In the scale of a hydrogen refuelling station (∼300 Nm³ h⁻¹), using pressure-swing adsorption (PSA) is not feasible owing to its low recovery, while using polymeric membranes cannot meet the H₂ purity demand. To achieve both a high H₂ purity and high H₂ recovery, we developed a physical-chemical system model of a 300 Nm³ h⁻¹on-site NH₃-fed hydrogen refuelling station to optimize a H₂ 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 H₂ 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 H₂ with a H₂ 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 € per kg. The feedstock cost accounts for 74% of the total specific cost. Using our optimized hybrid H₂ purification subsystem, the H₂ 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.