Abstract

The single greatest barrier to hydrogen (H₂) aviation is the immense challenge of storing and distributing liquid hydrogen (LH₂). This challenge is the primary obstacle to making flights that emit only water a practical reality. A significant part of this challenge stems from a fundamental property of H₂ itself: the interconversion of its isomers, ortho- and para-H₂, under liquid storage conditions. This exothermic isomerisation reaction is a major, direct contributor to the quick evaporation of LH₂, making fuel storage inherently inefficient. A solution is to promote the ortho-para conversion (OPC) with a catalyst in liquefaction. This enables the supply of stable LH₂ fuel that meets the standards required by H₂ aircraft designs.

This lecture will present findings from a recent study demonstrating that the industry-standard pursuit of >99% para-hydrogen purity is not only more expensive than we thought but also energetically sub-optimal for the aviation fuel cycle. The findings reveal that a strategically-tuned OPC process, accepting purities of 83-95%, reduces liquefaction energy demands by 8-13% while reducing evaporation losses during storage for the critical 1-7 day transport window. This optimisation, when coupled with green H₂ production, leads to a >92% reduction of CO₂ emissions from fuel production to flight on routes such as London-New York. Furthermore, this talk will outline the experimental continuation of this work, building on the kinetic understanding of the catalytic OPC . The new insights gained into this quantum phenomenon directly address the evaporation of H₂ in storage tanks, the economic viability of H₂ aviation, and the carbon footprint of the LH₂ supply.