IEEE Electrification Magazine - March 2018 - 53

Additionally, the
safety and
functionality of
hydrogen tanks are
tested and certified
by authorized
institutions.

fuel-cell systems is related to parts
that are inherent to the automotive
industry, but these have not yet been
mass produced by the free market.
These parts, e.g., sensors, controllers,
valves, filters, and blowers have
slightly different specifications compared to generic parts. However, with
the increased demand for FCevs,
many current vendors may participate in the supply chain, and the
prices should decrease.
of course, there are also many
components unique to fuel-cell systems that are new to the automotive industry, and they are
more related to the material and chemical industry, e.g.,
catalysts, membranes, and porous media. when the sales
volume of FCevs increases, as mentioned previously, the
related industries will not overlook the opportunity to
expand into this market. These components are also used
in hundreds of units per FCev, which may decrease the
threshold of mass production by a factor of a few hundred.
in addition, some people are more concerned about the
depletion of a material (platinum), which is used as a catalyst, than about the price. However, platinum is a noble
metal with well-studied recycling techniques. in other
words, platinum, which is one of the most expensive materials in a fuel cell, can be recycled from retired FCevs to
help prevent a steep price increase resulting from depletion, although the recycling process has its own costs.
little information is available about the cost of FCevs
because most carmakers regard the cost breakdown of
their vehicles as trade secrets. However, one may soon see
affordable FCevs in the market because of the previously
mentioned subsidies, cost reduction achieved by technology, or both. moreover, the popularity of FCevs will expedite
the price reduction.

hydrogen Safety
FCevs are not commonly observed on the streets, but they
are featured in many automotive shows and exhibitions
that focus on the environment. one of the most frequently asked questions about FCevs from attendees at these
shows is if they are dangerous, or, more specifically,
whether the hydrogen tanks in FCevs can explode. This
exaggerated fear may originate from the hydrogen bomb,
which is completely different from a hydrogen tank or a
hydrogen fuel cell and uses a fusion reaction that cannot
accidently occur with only hydrogen gas. although a
hydrogen tank is not a hydrogen bomb, the answer to the
question about whether or not a hydrogen tank can
explode is, unfortunately, yes, but the possibility is very
slim. The standard charging pressure of hydrogen tanks
for FCevs is 70 mPa, which is 700 times that of the atmospheric pressure and sufficiently high enough to explode
when the tanks are heated or impacted. To make matters

worse, hydrogen is readily flammable
when it is mixed with oxygen in the
air and ignited.
To safely store hydrogen in a
vehicle, the tank is designed to be
tougher than is required. its inside is
an airtight container made of plastic
or aluminum, and the outside is a
thick layer of carbon-fiber-reinforced
polymer, which gives it the strength
to endure more than double the required pressure of 70 mPa. because
of the selection of material and its
structure, a hydrogen tank deforms
instead of cracks when it is physically impacted. in addition, a special mechanical device called the thermally activated pressure-relief device (TPRD) is attached to the tank in
preparation for the event of exposure to a fire or high
temperature. The TPrd purposely opens an emergency
vent when the temperature of the tank increases beyond
a set value so that the hydrogen gas is discharged in a
controlled manner instead of in a disastrous explosion.
Therefore, an explosion of a hydrogen tank in an FCev
may only occur when a deliberate effort is made, e.g.,
to set a fire underneath the tank and cool the TPrd.
although the explosion, like any other event, probability
cannot be completely eliminated; it is considerably rare
and virtually impossible.
additionally, the safety and functionality of hydrogen
tanks are tested and certified by authorized institutions.
The test protocol is extensive and includes leakage, charge
and discharge cycles, drops, bursts, bonfires, bullets, and
so on. To the relief of the end user, these related regulations have been strengthened and require a single tank to
pass a series of tests rather than multiple tanks passing
individual tests. Finally, FCevs with hydrogen tanks
should pass various crash tests to ensure the safety before
customers can purchase them as common vehicles (Figure 6). Therefore, FCevs are at least as safe as any other
conventional vehicle.

Infrastructure
The last obstacle to overcome for the popularization of
FCevs is the insufficient infrastructure for hydrogen refueling. even with perfect FCevs that are environmentally
friendly, pleasing to drive, affordable, and safe, who would
buy them if their refueling takes hours of driving? meanwhile, who would build a refueling station if the number
of potential customers is very low? This is quite a dilemma. Furthermore, a pioneer who attempts to build a refueling station may be frustrated by public concerns about
hydrogen safety, which may make people reluctant to
allow one in their neighborhood.
objectively, the chances are slim that this quandary will
naturally be solved by the market economy. instead, strong
initiatives based on a reasonable belief of what must be

IEEE Electrific ation Magazine / ma r c h 201 8

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