Aircraft Carriage, Hydride Systems in Appliances (30.2)
Criticality: High
Progress: Not Addressed
Score: 40
DOT Relevance: §175
Description of Key Area
The carriage by aircraft of hydride-based hydrogen storage
systems is considered critical for commercial success by many potential
manufacturers of the hydrogen storage systems and fuel cell appliances and
devices powered by them. This area covers both rechargeable and
non-rechargeable type hydrogen storage systems, micro and portable systems, stand-alone
systems, and systems coupled to appliances. This section will discuss systems
transported while coupled to an appliance. Stand-alone systems, not coupled to
an appliance, are discussed in Item 30.1 of this report. The discussion of Item
30.1 is applicable to systems coupled to an appliance as well as for
stand-alone systems.
As has been previously discussed, hydride-based hydrogen storage
systems can be divided into two broad categories, rechargeable systems and
non-rechargeable systems. The rechargeable systems contain a reversible
hydride-forming material and are refilled by applying hydrogen; they will most
likely be identified by UN 3468 or NA 9279 with a 2.1 flammable gas hazard
classification. Non-rechargeable systems will likely contain a mixture of
hazardous materials that are not normally allowed within a single package since
they are capable of reacting together to produce a flammable gas. These systems
will require exceptions to a number of clauses in current regulations and may
require either new hazardous materials table entries or ORM-D exceptions. Each
of these two categories can be further divided into “micro” and “portable”
systems, with the difference being the intended use of the appliance they fuel.
Micro systems are primarily intended for use with low-power fuel cell
appliances for use in consumer electronics, such as cellular phones and laptop
computers. It is considered essential that these systems be able to be carried
and used by travelers in the passenger cabin of aircraft and upper size
limitations will likely be imposed. Portable systems are not intended to be
used in fixed, stationary locations but it is not expected that they need to be
carried or used in the passenger cabin of aircraft.
For micro systems, it is considered critical for commercial
success that they be able to be carried and used in the passenger cabin of
aircraft. For portable systems, it is not deemed critical that they be carried
and used in the passenger cabin of aircraft; however there are situations where
it may be important to be able to have them transported by passenger carrying
aircraft while coupled to an appliance. An example would be for systems used
with a fuel cell that powers a mobility device such as a wheelchair.
Standards being developed for hydride-based hydrogen storage
systems, such as ISO 16111, consider the systems up to a shut-off valve. The
standards are written to ensure that systems will not pose a hazard: by leaking
hydrogen at a rate that could create a flammable fuel-air mixture; from
overpressurization in fire conditions, etc. Either through the standards or
regulations, overpacking and requirements for restraining the systems during
transport may be imposed. When the systems are coupled into an appliance, the
testing found in the standards may not be sufficient. When coupled to an
appliance, the shut-off valve will likely be open and thus hydrogen will be
able to pass out of the storage container into the appliance. In this
situation, hydrogen leakage and overpressurization testing to ensure safety
must include the coupling and fuel cell appliance. The robustness of the
coupling between the storage system and appliance must also be tested against
potential abuse the combined unit may experience in transport and use.
In addition to modifications that might be required discussed in
Item 30.1 of this report, other modifications might be appropriate in §175.10(a) which is written
specifically for battery power mobility devices. It might be appropriate to
either modify them to include fuel cell powered devices or to include new
paragraph(s) under §175.10(a)
for fuel cell powered appliances.
Discussion of Criticality
This item has been assigned a criticality of high. It is expected
that many manufacturers will seek allowance of hydride-based hydrogen storage
systems aboard aircraft. DOT-E 13598 currently allows up to 90.7 kg (200 lb) of
UN 3468 material aboard cargo-only aircraft. Allowance will be sought to allow
micro systems to be carried in carry-on baggage within the passenger cabin of
aircraft. There is currently no allowance for systems to be carried into or
used within the passenger cabin of aircraft.
Consideration must be given to size and quantity limitations to
systems to be allowed within passenger baggage, carry-on and checked, and that
allowed as cargo on passenger and cargo-only aircraft. Packaging instructions
and container specification must include appropriate testing to ensure safety
of the systems allowed aboard aircraft. The testing for systems to be allowed
to be transported while coupled to an appliance must include the coupling and
appliance to ensure safety of the complete unit.
While it is considered critical that appropriate packaging
instructions be developed, 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
Hydrogen as a compressed gas, UN 1049, is allowed on cargo-only
aircraft with a 150 kg (331 lb) net limit. UN 3468, Hydrogen in a metal hydride storage system has been included in
ICAO’s dangerous goods list and forbidden from carriage on either cargo-only or
passenger aircraft. At the recent ICAO Dangerous Goods Panel meeting in Oct/Nov
of 2005, the panel accepted a proposal from the US
panel member to allow cargo-only carriage, with a 100 kg (220 lb) limit. This
new ruling is to become effective in January of 2007. Carriage aboard passenger
aircraft has not been allowed. US
DOT special permit E 13598 allows up to 90.7 kg (200 lb) of UN 3468/NA 9279
material be carried aboard cargo-only aircraft.
An informal and then a formal proposal were made to the UN SCETDG
by the representative from Japan,
to allow micro fuel cell systems and the fuel cartridges to be carried aboard
aircraft. The original informal proposal requested a new entry in the Dangerous
Goods List (DGL), with a hazard class 9. The formal proposal submitted for
consideration at the July 2005 meeting of the UN SCETDG was revised and instead
requested a new DGL entry with a flammable gas hazard, class 2.1. This proposal
was withdrawn without consideration. It is anticipated that a new proposal will
be submitted requesting modification of UN 3468 to include systems coupled with
fuel cell units as well as the stand-alone systems.
Progress on developing consensus standards that might be used as
a basis for 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.
- IEC
TC 105 has drafted and is currently reviewing a draft publicly available
standard for Micro Fuel Cell Systems (IEC PAS 62282-6-1). This document
includes sections on fuel storage containers and complete integrated fuel cell
appliances with fuel containers. This standard is expected to reference ISO
16111 for metal hydride-based hydrogen storage container design and testing.
IEC document 62282-5 for Portable fuel cell appliances may also be appropriate
for considerations for fuel cell appliances that do not qualify as micro, such
as might be used on mobility devices.
- UL
is developing a consensus standard (UL 2265) on micro fuel cell systems. An
effort is being made to keep UL 2265 consistent with IEC 62282-6 and its
development is therefore trailing that of IEC 62282-6.
Recommendations
It is recommended that the OHMS develop a minimum set of design
and test criteria for packaging of hydride-based hydrogen storage systems as
previously recommended in Items 18 and 25 of this report. Consideration should
be given to the impact of onboard aircraft carriage. 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. Size and quantity
limitations need to be considered for allowance aboard passenger aircraft,
particularly for inclusion in passenger baggage, checked as well as carry-on.
It is preferred that these criteria be performance-based. Ideally they would be
based on the ISO and IEC standards underdevelopment by international expert
committees (ISO 16111, IEC 62282-6-1 and IEC 62282-5). Systems coupled to
appliances must include the appliance standard, and may therefore have further
restrictions imposed.
New exceptions or
modifications of existing exceptions in §175.10(a) may need to be
developed for hydride-based hydrogen storage systems coupled to an appliance
allowed aboard aircraft.
To help ensure that the standards being developed for
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, IEC TC 105 working groups 7 and 8, and UL’s STP 2265.
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