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Emergency Response Information: Cryogas (19.5)

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 as a “cryogas” as part of a hydrogen vehicle fueling infrastructure.

“Cryogas” refers to a method of hydrogen storage being researched and developed at LLNL, which is also sometimes referred to as “cryogenic compressed hydrogen.” This hydrogen storage strategy seeks to store hydrogen gas (but not usually liquid or liquid-gas mixtures) at cryogenic temperatures (e.g., 80°K) and moderately high pressures (e.g., 25 MPa). The claimed advantages of this storage strategy include: higher storage density than conventional compressed storage, less hold-time and boil-off issues than liquid storage, no energy consumption for ortho-to-para conversion, and flexibility to fill the tank to pressure-temperature conditions tailored to the specific mission.

DOE has sponsored LLNL to study potential applications of cryogas storage for hydrogen vehicle fuel tanks and also for the tube trailer delivery from centralized hydrogen production plants to fueling stations. If this type of tube trailer is in fact manufactured and used as part of a commercialized hydrogen fueling infrastructure (or if any other cryogas-type hydrogen packaging is used as part of such an 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 cryogas storage do in fact evolve. This is because the emergency response requirements may be different from currently available resources, and no known work is currently underway to develop cryogas packaging emergency response information resources. 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 cryogas based systems may not play a significant role relative to distributed production (i.e., at the fueling station) or delivery via pipeline. Also, cryogas is in the R&D stage at this time. Small cryogas tanks have been fabricated and tested in the laboratory and in the field, but no large-capacity packaging or tube trailers have been built.

Discussion of Progress

Progress toward providing emergency response information resources appropriate to cryogas packagings and transportation used as part of a hydrogen fueling infrastructure is rated as “Addressed, Not Adequately.” This is because no specific resources exist at this time. The DOT ERG2004 Guide Number 115 (Gases—Flammable, Including Refrigerated Liquids) covers hydrogen that is either compressed or liquefied, but responding to a hypothetical cryogas tube trailer accident might involve some issues that are not covered in this guide.

LLNL and subcontractors have carried out some relevant tests of small cryogas “insulated pressure vessels” including burst tests and drop tests. They have also published claims that cryogas vessels would be safer than conventional high-pressure vessels because they contain less mechanical stored energy, the fatigue strength of reinforcement materials is higher at low temperatures, and other reasons.

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 the development of cryogas storage technology for hydrogen should be monitored. If it appears likely that this technology may be used as part of a commercialized hydrogen vehicle fueling infrastructure (e.g., cryogas tube trailers), then work to develop appropriate emergency response information resources should be initiated.