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.