Emergency Response Information: Complex Hydrides (19.7)

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 the refueling material transportation infrastructure that might be used for hydrogen vehicles with complex hydride fuel storage systems.

“Complex hydrides,” as used here, refers to hydrides that are not readily reversible so that they are not regenerated while packaged in the vehicle fuel tank by being exposed to hydrogen gas. Instead, they are usually processed as a solution or slurry, which is often called a carrier. The hydrogen-releasing reaction usually involves mixing the carrier with water with the aid of a catalyst. The vehicle is refueled by removing the spent carrier and replacing it with freshly regenerated (hydrided) carrier. The spent carrier is then regenerated at a central processing plant, and the cycle repeats. Sodium borohydride is the most frequently cited example of this type.

DOE is sponsoring a large team jointly headed by LANL and PNNL to research and develop chemical hydrogen storage technologies of this type for low-cost on-vehicle systems with high gravimetric and volumetric energy density. Sodium borohydride systems have been field tested to a limited extent, e.g., in the Chrysler Natrium fuel cell vehicle.

Here we are concerned with the material packaging and transportation system that would be needed to support the refueling infrastructure for hydrogen vehicles with hydrogen storage systems that require defueling of a spent material, refueling with a regenerated material, and material regeneration at a central plant.

Discussion of Criticality

This key area will be critical if commercial hydrogen vehicles employ fuel storage systems containing hydrides such as sodium borohydride, which must be recharged at a central processing plant. This is because, even though some partially applicable emergency response information resources currently exist (e.g., the DOT ERG2004, as discussed below), these resources may not be ideally applicable to the specific chemicals and transportation systems that support the refueling infrastructure, 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 hydrogen vehicles of this type will be commercialized, and the associated spent/regenerated slurry exchange type of refueling infrastructure will develop. In this regard, it should be recognized vehicle fueling infrastructure will in fact develop but complex 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 the refueling transportation infrastructure that might be used to support hydrogen vehicles with chemical hydride slurry fuel storage systems is rated as “Addressed, Not Adequately.” This is because, while some resources currently exist, they may not be applicable to the specific hazardous materials that might be used in commercialized chemical hydride slurry fuel storage systems, and they may not be adequate to cover operations at public-access fueling stations.

For example, the DOT ERG2004 lists Sodium Borohydride (ID Number 1426, with reference to Guide Number 138). Guide Number 138 is for “Substances—Water Reactive (Emitting Flammable Gases).” Other listings in the Guidebook address other candidate chemical hydrides such as Magnesium Hydride (ID Number 2010, which also references Guide Number 138). It remains to be determined if all materials that might be used in a commercialized chemical hydride slurry refueling infrastructure are in fact covered in the Guidebook, and if these emergency response information resources are adequate for operations (i.e., tank truck loading of spent carriers, unloading of freshly regenerated carrier) at public-access fueling stations.

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.

Recommendations

It is recommended that research to develop chemical hydride hydrogen storage technologies (that are regenerated at a central plant and not in the vehicle fuel tank) should be monitored. Emphasis should be placed on characterizing the infrastructure required to “refuel” these systems—specifically, the processes envisioned for transporting spent carrier from fueling stations to central plants and for transporting regenerated (hydrided) carrier from central plants to fueling stations. Potential hazards associated with this transportation, including loading/unloading operations at public-access fueling stations, should be identified and the applicability of existing emergency response information resources should be assessed.

If R&D succeeds in developing this type of hydrogen storage and refueling infrastructure technology, and it appears that this technology may be used to support hydrogen vehicle commercialization, then work to develop appropriate emergency response information resources should be accelerated.