High Flow Liquid Hydrogen Fueling Couplings for Aerospace and Heavy Transport Applications
AIR8999
The SAE AE-5CH Taskgroup has determined that high flow liquid hydrogen fueling couplings need to be developed in order to fast fill aircraft at the airport.
Though the flow rates from a current liquid hydrogen bayonet connect may reach the lower bound flow rates of regional aircraft, there are some shortcomings to this connector for aerospace. For this reason a new specification for flow rates for regional to narrowbody (and potentially later widebody) are to be developed in this documenet.
Harmonization for lower flow rates (such as up to 20kg/minute) are planned to be harmonized with ground vehicle fueling such as with ISO 13984. Within this document,coupling descriptions including Flow rates from 84 to 200 kg/minute will be evaluated (and potentially higher), and requirements and testing and safety targets will be specified.
Rationale: Today, aviation accounts for around 2.5% of global CO₂ emissions, but 3.5% when non-CO₂ impacts on climate are considered. Although aviation represents a relatively small percentage of global emissions today, that could rise to 22% by 2050 , as more people fly and other sectors decarbonize quicker. Though Sustainable Aviation Fuels (SAF) offer an interim solution to reducing emissions, it does not completely solve emissions, and is much more energy intensive. Whereas pure hydrogen as a fuel holds great potential to decarbonize aviation as well as other hard to abate transportation sectors.
Presently there are established codes & standards for ground vehicles at SAE, ISO, NFPA, etc. that could also be applicable to some applications for hydrogen at the airport. While there are some existing fuel cell and hydrogen standards for Aerospace (such as the SAE/EUROCAE efforts) there is a need to create new fueling station standardization efforts, outlined herein. For one, the ambient conditions are significantly different related to expected temperatures on the tarmac and tanks that could be exposed to the direct sunlight, unlike ground vehicles. Large aircraft such as a regional, narrow body or a wide body require up to 100x to 1000x more hydrogen storage (e.g. 1000 kg to 10000+ kg) than light to heavy duty ground vehicle fueling (5kg* to 120kg+). With this larger amount for aircraft fueling, there will be an exponentially larger need for hydrogen supply and fueling on site.
Hydrogen fueling process limits described herein (including fuel temperature, the maximum flow rate, time required, etc.) are affected by factors such as ambient temperature, fuel delivery temperature, and initial pressure in the hydrogen storage system. At the airport similar to conventional hydrocarbon fuels, there will be both mobile fueling trailers and stationary hydrogen fueling stations which are planned to be within the SAE AIR 8466 scope. A further goal is to harmonize and establish common aircraft fueling safety definitions and wherever possible with other SAE, EUROCAE standards and NFPA codes, etc. standards alike. Gaseous Hydrogen Fueling and Liquid Hydrogen Fueling at cryogenic temperatures are two very different types of fuel stored in different types of vessels with safety mitigations. The goal is to start with an all-encompassing SAE AIR for hydrogen fueling and after publishing, establish a family of documents covering categories of fueling as determined by the SAE AE-5CH taskgroup.
