The
Hydrogen Fuel Cell -- What It Is
And What It Is Not
There has been a lot of talk lately in
this country about using
alternative fuels – specifically hydrogen fuels that run on
fuel
cells. So what is a hydrogen fuel cell anyway?
Here's an
easy
explanation.
A fuel cell is an electrochemical energy
conversion
device that converts the chemicals hydrogen and oxygen in water
usually to produce electricity. Another electrochemical
device
that we are all familiar with is the battery. A battery has
all
of its chemicals stored inside, and it converts those chemicals into
electricity too. But a battery eventually "goes dead" and
you either throw it away or recharge it.
With a fuel cell, chemicals constantly flow into
the cell
so it never goes dead -- as long as there is a flow of chemicals into
the cell, the electricity flows out
of the cell. Most fuel cells in use today use hydrogen and oxygen as
the chemicals. The biggest advantage to a hydrogen fuel cell
is
that the only thing it emits when used as a fuel is water vapor.
You cannot ask the question “What is a hydrogen
fuel cell?”
without considering the types of fuel cells that have been
produced. The main type of hydrogen fuel cell is the polymer
exchange membrane fuel cell (PEMFC). This is the fuel cell
that
the Department of Energy is focusing on as the next big thing because
it is considered to be the most likely candidate for transportation
applications.
There is another type of hydrogen fuel cell that
shows
promise for operating motor vehicles. This one is the direct
methanol fuel cell (DMFC). Methanol fuel cells are comparable
to
a PEMFC in regards to operating temperature, but they are not as
efficient. Also, the DMFC requires a relatively large amount of
platinum to act as a catalyst, which makes these fuel cells expensive.
To answer the question: "What is a hydrogen fuel cell?"
We have to say that it is the next new wave of emerging technology in
the field of alternative fuels that will help our country get closer to
energy independence. It is what will give us a
clean
vehicle that runs great and has safe emissions.
Advantages
There’s no doubt that the
development
of hydrogen fuel cells as an alternative fuel is good for the
environment.
First, let’s consider the fact that
hydrogen fuel cells are good for the environment because they are the
cleanest burning fuels ever developed. Hydrogen is taken out
of water and then put into fuel cells as a gas that can power a
vehicle. The only emission that comes out of a fuel cell
powered vehicle is water vapor. It’s like having a
humidifier for the whole world!
Disadvantages
There are, however, some drawbacks that are
associated with hydrogen fuel cells and the environment. A
completely efficient system of producing, storing and transporting
hydrogen should, in principle, lead to no unwanted emissions of the gas.
But the researchers point out that such a system
would be expensive, and that in reality around 10-20% of the hydrogen
would escape into the atmosphere. They say that if hydrogen fuel cells
replaced all of today's oil and gas-based combustion technologies, such
losses would double or even triple the total hydrogen deposited into
the atmosphere at the Earth's surface.
Those who have studied hydrogen fuel cells say
that there are three
main disadvantages to using hydrogen as a fuel source.
1. The low
density. A hydrogen fuel tank will have to be three times
the size
of a standard gasoline tank. Also it must be insulated, and this will
add to its
bulk.
2. Safety
problems. Liquid hydrogen is cold enough to freeze air,
and
accidents have occurred from pressure build-up following plugged
valves. Some say these problems can never be overcome, but many side
with
those who think they can be overcome.
In a collision the hydrogen tank may rupture, just
like a gasoline tank can.
Limited historical accident data suggests that the danger is somewhat
less
with hydrogen than with gasoline, because the hydrogen dissipates
rapidly. HOWEVER
The release of hydrogen into a confined space like a garage
risks an explosion.
3. Evaporation. Since
the insulation can't be perfect, the hydrogen will gradually
evaporate -- typically 1.7 percent per day. This is too fast for a car
that
sits for months between uses. A tank of compressed hydrogen holding
just enough to get to a hydrogen station would solve this disadvantage.
If the engine is flexible enough to burn gasoline
as well as hydrogen,
a half gallon gasoline tank would suffice. Some automobile companies
like BMW, have experimented with vehicles powered by liquid hydrogen.
However, hydrogen cannot come into common use until the political
obstacles are overcome.
There’s really no doubt that using
hydrogen fuel cells as an
alternative fuel can be very advantageous both for the environment as
well as for America in general by reducing our dependence on foreign
oil. But there still are some significant disadvantages that
must
be overcome before we can realize the real benefits of using hydrogen
fuel cells as our main source of energy to power our vehicles.
The bottom line is that hydrogen fuel cells have a
positive effect on
the environment. When the only emission
that comes from hydrogen fuel cells is water vapor, you are talking
about a huge advantage over the toxic elements that are released into
the air with gasoline and diesel burning vehicles. There are
many more advantages than
disadvantages and hydrogen as an alternative fuel has the most promise
over any other alternative fuel.
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