Technology Status of Hydrogen Road Vehicles

Appendix 1. Safety Questions of Hydrogen Storage and Use in Vehicles
This Appendix shows the available findings on the safety concerns and solutions when hydrogen is stored onboard
and used in road vehicles. Other situations with different safety implications, such as large-scale
stationary hydrogen storage, will not be explicitly handled.
Until operating data are accumulated with hydrogen vehicles, the best approach is to examine the following:
! The fundamental properties of hydrogen with safety relevance
! The experience to date from comparable industries (including space)
! Recent simulations of specific accidents with H 2 vehicles.
Undoubtedly laymen, and even many technically informed people, react to hydrogen as a particularly
dangerous substance. Yet insiders are becoming ever more convinced that hydrogen has a safety behavior
different, but no worse than, conventional transportation fuels. It is probably safer overall, provided some
basic rules are followed. The public reacts with some skepticism to such affirmations, and great care will be
needed in presenting the situation in a balanced and convincing way. This means paying considerable
attention, when the time comes, to societal concerns as well as to technical aspects.
Much technical work remains to be done to assure even the specialist that hydrogen vehicles can be safely used
by the public. This report concentrates on the technical aspects; however, societal concerns should be factored
rather soon into remaining developments. The reaction provoked by others such as the nuclear industry, which
underrated the need to address legitimate public concerns, should be avoided at all costs.
Hydrogen has routinely been used in large quantities for decades in the petroleum refining, chemical, and
petrochemical industries with no serious problems. Moore 1996, summarized in Appendix 4, gives relevant
experience in the USA. The space industry has a similar record, marred only by the Challenger accident
(discussed in section A1.4).
The manner in which safety objectives have been met by these industries is outlined below. This experience
is largely applicable to hydrogen vehicles, but has in this context one important weakness: the public was not
involved, and all procedures were safely in the hands of qualified personnel. The safety consciousness typical
of such industries can be brought to high levels by training and automatic control, but is difficult to transfer
to the public.
For the foreseeable future, highway driving will be subject to unpredictability, and accidents to confusion and
panic. A new fuel should possess better inherent safety than gasoline or diesel oil. Somewhat paradoxically,
hydrogen has such characteristics, at least to the specialist. A large part of the following discussion will
therefore involve comparisons with traditional fuels.
This appendix was written before an important, but unpublished, report (EQHHPP 1993) was made available
after the update was due to the 11th WHEC. Although we could not examine the implications of this report
throughout this document, we have been given permission to quote its summary here:
In brief, the study comprises:
! a compilation of physical and chemical properties of hydrogen
! a description of hazards
! a collection of international and national rules, discussed in varying depth
! a number of recommendations for further development of rules and their international harmonization
! proposals for the promotion of hydrogen, and the proper approach of the public in the early phase of
industrial projects
! standards and their relevance for selected items of the EQHHPP (in the appendixes)
A1.1 Fundamental Hydrogen Properties with Safety Relevance
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