Emergency Response Information: Metal Hydride (19.4)
Criticality: High
Progress: Addressed, Not Adequately
Score: 20
DOT Relevance: §172 Subpart G
Description of Key Area
This key area pertains to the availability of appropriate
information resources needed by first responders to potential emergencies
(e.g., accidents) involving hydrogen transported in metal hydride storage
systems used as part of a hydrogen vehicle fueling infrastructure.
“Metal hydrides,” as used here, refers to metals for which the
hydriding reactions are reversible at convenient temperatures and pressures so
that the recharging process is accomplished by simply applying hydrogen gas to
the system over a brief time period with heat removed to a heat transfer fluid.
DOE is sponsoring a large team headed by SNL to research and develop metal
hydrides for low-cost on-vehicle hydrogen storage systems with high gravimetric
and volumetric densities. Metal hydride hydrogen storage systems are also being
developed by various industrial firms, some systems are being field
demonstrated, and a few have been commercialized for specific applications.
Possible evolution of economical metal hydride storage systems
with suitable density and convenient rechargeability brings up the possibility
that such systems could be used to transport hydrogen from a central production
plant to a fueling station. For example, metal hydride powder might be
contained within a pressure vessel equipped with heat exchanger elements and
connections, and the overall system might be trailer-mounted so that it
resembles a tank truck trailer. At the hydrogen vehicle fueling station, hydrogen
could be discharged from this trailer to charge permanently installed hydrogen
storage equipment or the metal hydride tank truck trailer could be disconnected
and parked to provide temporary hydrogen supply for the station (analogous to a
tube trailer). If this type of hydrogen transportation system is used as part
of a commercial hydrogen vehicle fueling infrastructure, then emergency
response information resources specific to this technology will be needed.
Discussion of Criticality
This key area will be critical if hydrogen fueling
infrastructures that utilize metal hydride hydrogen storage and transportation
systems do in fact evolve. This is because, even though some partially
applicable emergency response information resources current exist (e.g., the
DOT ERG2004 lists hydrogen absorbed in metal hydride, as discussed below),
these resources may not be applicable to new metal hydride technologies and
storage/transportation systems, and they will probably not be applicable to
operations in an open-public-access environment such as a public fueling
station.
The important but unanswered question pertains to the likelihood
that such a hydrogen vehicle fueling infrastructure will in fact develop. In
this regard, it should be recognized vehicle fueling infrastructure will in
fact develop but metal hydride based systems may not play a significant role
relative to distributed production (i.e., at the fueling station) or delivery
via pipeline.
Discussion of Progress
Progress toward providing emergency response information
resources appropriate to metal hydride hydrogen storage packagings and
transportation systems used as part of a hydrogen fueling infrastructure is
rated as “Addressed, Not Adequately.” This is because, while some resources
currently exist, they may not be applicable to evolving metal hydride
technologies and packaging/transportation systems, and they may not be adequate
to cover operations at public-access fueling stations.
The DOT ERG2004 lists both Hydrogen (ID Number 1049, with
reference to Guide Number 115, “Gases—Flammable, Including Refrigerated
Liquids) and Hydrogen Absorbed in Metal Hydride (ID Number 9279, which also
refers to Guide Number 115). Other listings in the Guidebook address some of
the solid material categories potentially applicable to uncharged
(non-hydrided) metal powders that might be used in a hydrogen metal hydride
storage system. Examples include various pyrophoric metals, self-heating
solids, and water-reactive solids. However, there are serious uncertainties, which
are discussed elsewhere, regarding the potential applicability of guidelines
for non-hydrided materials to a metal hydride hydrogen storage package and
transportation system delivering hydrogen to a hydrogen vehicle dueling station
site.
In 2005, the NASFM and DOT’s RITA established the Hydrogen
Executive Leadership Panel (HELP). HELP’s mission is “…to bring together
emergency responders, government regulators, scientists, consumers and experts
from the automotive and energy industries to facilitate a safe and orderly
transition to hydrogen and other alternative fuel sources.” HELP will focus on
issues involved in training, educating, and mobilizing emergency responders to
work with government, industry, and community groups to facilitate and ensure
hydrogen transport, storage and distribution, and the safety of vehicles and
environs.
ASME's Boiler and Pressure Vessel project team on hydrogen tanks
is addressing metal hydride vessel design in a code case to Section VIII-1.
Recommendations
It is recommended that research to develop metal hydride hydrogen
storage technologies should be monitored. Analyses and perhaps testing should
be carried out to identify any scenarios where accidents involving metal
hydride hydrogen storage systems might involve exposure to non-hydrided
materials that are pyrophoric, toxic, or otherwise hazardous. It is anticipated
that these analyses and possible tests are being, or will be, carried out as
part of current on-vehicle metal hydride hydrogen storage R&D efforts or
current metal hydride commercialization activities, but this should be
verified.
If R&D succeeds in developing practical and economical metal
hydride hydrogen storage systems, and if it appears that this technology may be
used as part of a commercialized hydrogen vehicle fueling infrastructure (e.g.,
tank trucks containing hydrogen absorbed in metal hydrides used to transport
hydrogen from central production plants to fueling stations), then work to
develop appropriate emergency response information resources should be
initiated.
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