Safety of Cryogenic Liquid Hydrogen Bunkering Operations - The Gaps Between Existing Knowhow and Industry Needs

Hydrogen plays an important role in the global transition towards Net-Zero emission. While pipelines are a viable option to transport large quantities of compressed hydrogen over long distances, it is not always practical in many applications. In such situations, a viable option is to transport and deliver large quantities of hydrogen as cryogenic liquid. The liquefaction process cools hydrogen to cryogenic temperatures below its boiling point of -259.2 0C. Such extreme low temperature implies specific hazards and risks, which are different from those associated with the relatively well-known compressed gaseous hydrogen. Managing these specific issues brings new challenges for the stakeholders.
Furthermore, the transfer of liquid hydrogen (LH2) and its technical handling is relatively well known for industrial gas or space applications. Experience with LH2 in public and populated areas, such as truck and aircraft refuelling stations or port bunkering stations for example, is limited or non-existent. Safety requirements in these applications, which involve or are in proximity of untrained public, are different from rocket/aerospace industry.
The manuscript reviews knowhow already gained by the international hydrogen safety community; and on such basis elucidate the gaps, which are yet to be filled to meet industry needs to design and operate inherently safe LH2 operations, including the implications for regulations, codes, and standards (RCS). Where relevant, the associated gaps in some underpinning sciences will be mentioned; and the need to contextualise the information and safety practices from NASA1/ESA2/JAXA3 to inform risk adoption will be summarised.