Packaging Instructions for Portable Metal Hydride Hydrogen Storage Systems (18.3)
Criticality: High
Progress: Not Addressed
Score: 40
DOT Relevance: §173 Subpart D
Description of Key Area
UN SCETDG has approved entry UN 3468, Hydrogen in a metal hydride storage system, to the Dangerous Goods
List in the UN Model Regulation for the Transport of Dangerous Goods. This
entry has been adopted by the US DOT and is included in the Hazardous Materials
table in 49 CFR 172.101. Packaging instructions for UN 3468 require approval by
the Associate Administrator prior to first shipment (49 CFR 173.214). The
Hazardous Materials table also includes entry NA 9279, Hydrogen absorbed in metal hydride, which includes no packaging
instructions and requires a special permit for transport. Without any guidance
on packaging, the OHMS must individually review and issue an approval or
special permit for each system design and manufacturer/offeror for all metal
hydride-based hydrogen storage systems.
This discussion applies to both entries, UN 3468 and NA 9279.
Systems which are appropriately identified by these entries can be divided into
two broad groups that really only differ in where and how they might be used
and transported. This section will discuss “Portable” systems and Item 18.2
discussed “Micro” systems. Micro systems are ones that are expected to be
transported both as stand-alone storage containers and as storage containers
connected to and in use with fuel cell systems. It is anticipated that Micro
systems will be approved for transport and use with all modes of transport including
the passenger cabin of aircraft. Portable systems are not expected to be
transported or used within the passenger cabin of aircraft. In most instances
portable systems will be stand-alone; however there may be specific
applications where the portable systems will be attached to a fuel cell
appliance during transportation.
Today electronic appliances are ubiquitous and there is ever
greater demand to un-tether them from the grid, i.e., to use them without
always having a cord running to a grid-connected electrical outlet. Today this
is accomplished by the use of batteries. However a gap has been developing
between application power and energy demand and the ability of current battery
technology to meet demand. Hydrogen fuel cell technology is expected to be able
to provide better power and energy capabilities in these applications. Fuel
cells are similar to batteries in that they convert chemical potential energy
into electrical power and energy. However unlike batteries, the fuel and
oxidant are supplied from external sources and the by-products exhausted. With
hydrogen fuel cells, the fuel is hydrogen and the by-product is water. Another
advantage of hydrogen fuel cells is that they do not need electricity to be
“recharged” as batteries do. This advantage can provide tremendous benefits
under certain circumstances such as what was experienced by emergency
responders on the Gulf Coast
after hurricane Katrina in 2005 when there was no operational electrical grid
to recharge batteries for radios and other equipment.
Portable metal hydride-based hydrogen storage systems will find
use in many applications, not all of which will be with fuel cells. Since these
systems can provide a very compact, low-pressure storage option for hydrogen
gas, they may be used in laboratories which need hydrogen for equipment, such
as gas chromatographs. They may be used as exchangeable fuel tanks on mobility
devices such as wheel-chairs, scooters, golf carts, etc., which may be
propelled by either fuel cells or internal combustion engines. Portable systems
are expected to be used with portable generators for backup power and for
auxiliary power units (APUs), which is an example of an application where they
might be connected to an appliance and operating while being transported.
Currently there are a lot of development activities being carried
out by various companies and organizations around the world on these
technologies. Entry level products have started entering the marketplace. The
number of products and designs available are expected to increase dramatically
over the next few years. Without packaging instructions being included in the
hazardous materials regulations and without at least a template or set of
guidelines for use by the OHMS for evaluating these systems, the effort
required to review and approve or issue special permits for each may be
burdensome.
Discussion of Criticality
This item has been assigned a criticality of high. Without
packaging instructions being developed for metal hydride-based hydrogen storage
systems, there is no set of consistent minimum requirements to manufacturers
and offerors follow. The absence of packaging instructions requires that OHMS
personnel review and approve each system from each offeror and manufacturer.
This could present a burdensome work load on the OHMS if this technology is
found to be able to meet current expectations leading to many requests for
approval.
While it is considered critical that packaging instructions be
developed for systems identified by UN 3468 and NA 9279, it is also recommended
that the packaging instructions be designed so as to not prohibit new and
innovative designs. This technology is relatively new and is evolving. New
advanced materials and designs are expected. The packaging instructions should
therefore be performance-based and avoid being too prescriptive, while ensuring
a minimum level of safety.
Discussion of Progress
The hazardous materials table currently includes two listings: NA
9279, Hydrogen absorbed in metal hydride
and UN 3468, Hydrogen in a metal hydride
storage system. Currently these identifications can only be used with
approval from the OHMS after review and approval of the packaging. No packaging
instructions have been adopted in either the US
regulations or the UN Model Regulations. The OHMS has issued several special
permits for metal hydride hydrogen storage systems that are identified by
either one or both of these identifiers.
Progress on developing consensus standards that might be used as
packaging instructions include:
- The
ISO technical committee for hydrogen technologies (TC 197) has a working group
drafting a standard for transportable reversible metal hydride hydrogen storage
systems (ISO 16111). This document is currently in the approval stage as a
committee draft (“CD”) for advancement to the draft international standard
stage (“DIS”). In parallel to the CD approval, the document is being considered
for publication as a technical specification; with possible publication of the
TS much earlier than possible for the International Standard. Once the
international standard is approved, the technical specification will be
withdrawn. This document only considers stand-alone containers.
- CGA
has also considered developing a standard for portable metal hydride hydrogen
storage systems. This effort is early in development and the expected
publication date is unknown.
Proposals have been submitted to ICAO for approval of metal
hydride-based hydrogen storage systems to be transported aboard aircraft. ICAO
approved transport aboard cargo aircraft. It is expected that future requests
to ICAO for transport in the cargo space of passenger aircraft will be made
once a published document on system design and testing is available for
reference. The OHMS granted special permit DOT-E 13598, issued to Jadoo Power
Systems, that allows up to 90.7 kg (200 lb) to be transported aboard cargo
aircraft.
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 the OHMS develop a minimum set of design
and test criteria for packaging of systems that meet the UN 3468 and NA 9279
hazard descriptions and that meet the portable system definition used in this
report. These criteria should be provided to potential manufacturers and
offerors for use in their design and testing of the storage systems and would
help ensure consistency in application of rigor in determining the minimum
level of safety. It is preferred that these criteria be performance-based.
Ideally they would be based on ISO 16111, underdevelopment by an international
committee of experts.
To help ensure that the standards being developed for metal
hydride-based hydrogen storage systems meet the need of OHMS, it is recommended
that the OHMS assign personnel or contractors to actively participate on the
applicable development committees. These would include ISO TC 197 working group
10 and the CGA Hydrogen Fuel Technology committee.
From experience obtained from systems approved under these
guidelines, they could, at an appropriate future time, be refined and used as a
basis for a New Rule Making Proposal for conversion into regulations and
incorporated into 49 CFR 173.
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