Technology Status of Hydrogen Road Vehicles

on time scales that range from instantaneous to a few years. All originate in settings that are somewhat
remote; without a suitable vector, they may never make much impact, especially on urban transport. Hydrogen
is such a vector, and in its pure form does not disturb the environmental merits of clearens. Whether it should
be used alone or in combination with a carrier (e.g., methanol is a liquid carrier similar to other oil products;
reduced iron is a carrier similar to ore) is still an open question. In fact, there may be several competitive
approaches to what may become a major shipping industry that will bring clearens from remote to
industrialized areas.
This report does not define the technological status of these approaches to bulk hydrogen production and
transport. For present purposes, large quantities are not necessary to fuel a limited number of prototype and
small-fleet demonstrations of hydrogen vehicles. Even when the niche markets imposed by regional
legislation become reality, clearen-derived hydrogen is not a must; any local supply of hydrogen such as
refinery off gases or even electrolyzers powered by local electricity will suffice. The point is, there is nothing
wrong with decoupling early hydrogen vehicles from clearen-derived hydrogen; any hydrogen will do.
Storage batteries are accepted as the motive power for zero-emission vehicles (ZEVs) and they, like
home/local electrolyzers, simply shift the fossil fuel pollution, albeit much reduced, from local to power plant
settings. In some vehicle applications such as fuel cells (FCs), the impurity levels in the hydrogen could be
important. However, water electrolysis (which seems to be the front runner in clearen-derived hydrogen) is
very pure (>99.999%).
There is increased emphasis in the 11th WHEC (see Appendix 4) on hydrogen derived from hydrocarbon
sources, especially by reforming of methane or methanol; this trend will be discussed throughout the report.
Moore and Raman (1996) and Ogden (1996) examine various options of putting hydrogen into the vehicles
in cities.
2.2 Urban Distribution
Hydrogen distribution is, especially in an urban setting, less straightforward than that of almost any other gas
or liquid fuel. Even if town gas (before the arrival of natural gas) contained considerably more hydrogen, it
still could not be compared to pure hydrogen from handling and safety points of view. In fact, hydrogen’s
interface with the public is one of its main hurdles. This interface is dominated by safety concerns, both real
and perceived.
The real safety questions have received considerable attention, and will always be integral to vehicle design
and operation. They are fundamental to any hydrogen application (especially urban transport); the important
results are summarized in Appendix 1.
The safety of hydrogen is so different from that of conventional fuels that simple comparisons can be
misleading. The precise application is critical. In general, if hydrogen is properly handled, its safety potential
exceeds conventional hydrocarbon fuels; improperly handled (especially if it leaks in confined spaces), it can
be more explosive. Designing and operating hydrogen vehicles to guarantee adequate safety are matters for
engineers and regulatory authorities. Hydrogen should not affect driving or life styles, unless vehicles are
parked in garages or other confined spaces that do not have proper and guaranteed ventilation.
The automotive industry has usually listened to the experts about safety issues, especially since the 1960s
when safety moved to the forefront of most designs. But that is not true of all industries: the Challenger
accident is a reminder of what happens when other pressures overwhelm safety. The measures available to
keep safety at the forefront are discussed in Appendix 1.
The perceived safety questions can be more intractable, particularly in a startup phase of hydrogen vehicles.
2