D39_2021-01 PRESLHY_ChapterLH2-v3

The interest in hydrogen as a clean fuel and energy carrier of the future has grown in many countries and initiated comprehensive research, development, and demonstration activities with the main objective of the transition from a fossil towards a CO2 emission lean energy structure as the ultimate goal.
Hydrogen represents an energy carrier with high energy content and a clean, environmentally benign source of energy to the end-user. The volume-related energy content of gaseous hydrogen, however, is comparatively small. For various applications of hydrogen where volume is an essential issue, it is necessary to liquefy the hydrogen for the sake of volume reduction. But there are also other situations where the liquid state represents a reasonable and economic solution for storage and distribution of large amounts of hydrogen depending on the end-user’s requirements. Furthermore liquid hydrogen has the advantage of extreme cleanliness making it appropriate in many industrial applications. Major drawback is the enormous energy input required to liquefy the hydrogen gas, which has a significant impact on the economy of handling LH2.
The hazards associated with the presence and operation of LH2 containing systems are subject of safety and risk assessments. Essential part of such accident sequence analyses is the simulation of the physical phenomena which occur in connection with the inadvertent release of LH2 into the environment by computation models. The behavior of cryogenic pool propagation and vaporization on either a liquid or a solid ground as well as potential pool burning is principally well understood. Furthermore state-of-the-art computer models have been developed and validated against respective experimental data. There are, however, still open questions which require further efforts to extent the still poor experimental data basis.
The experimental and theoretical investigation of the characteristics of liquid hydrogen, its favorable and unfavorable properties, as well as the lessons learnt from accidents have led to a set of codes, standards, regulations, and guidelines, which resulted in a high level of safety achieved today. This applies to both LH2 production and the methods of mobile or stationary LH2 storage and transportation/distribution, and its application in both science and industries.