The Hydrogen Fuel Cell is a
Promising Source of Energy for Today and Tomorrow
Ms. Lessard
18 December 2002
In the world there are many problems
that have been presented and ignored for many years. One of the biggest issues
in the United States, and the world, is dependency on fossil fuels. Every year
the United States spends billions of dollars on importing fossil fuel to power
anything from houses, to cars, to electrical power generation. These fossil
fuels are big culprits in the formation of greenhouse gasses that cause global
warming. There is a better way to get energy, which would have minimal impact
on the environment around the world. This alternative to fossil fuels is the
hydrogen fuel cell. Though converting to hydrogen fuel cells could be
costly, it is the cleanest and brightest solution to the world’s dependency on
the combustion of fossil fuels.
A fuel cell is a device that runs on
fuel and creates an electrical current. Most fuel cells run on hydrogen as a
fuel. Hydrogen is the most abundant element in our known universe, though pure
hydrogen is in short supply. The hydrogen needed to run hydrogen fuel cells
must be extracted from another source because hydrogen is very buoyant, and if
it was found in it’s gaseous, pure, form it would float up into the sky within
seconds unless it is contained. There are many chemical processes that can be
used to produce pure hydrogen gas to run fuel cells.
One such chemical process is called
electrolysis. For electrolysis, only a few materials are needed to start with,
and those materials are water and electricity. Electrolysis is when water is
taken and electricity is passed through the liquid solution. The electricity,
in turn, breaks apart the water molecules into their elemental forms of pure
hydrogen and oxygen gas. These two gasses are then captured in containers so
that the hydrogen and oxygen can be stored for later use in a fuel cell. This
method of producing hydrogen and oxygen gas is one of very few processes that
have zero-emissions, which means that there is no harm done to the environment.
The energy needed in electrolyzing water can come from many sources. One of the
most promising sources of this energy is from solar powered photovoltaic cells.
Though, electrolysis obviously is not the only way to get pure hydrogen gas.
Fuel reforming is another
mentionable source for producing pure hydrogen gas. When using a fuel reformer
as a source of hydrogen there is a larger list of fuels that can be used to get
the hydrogen gas needed in a fuel cell. The fuels that can be used in a fuel
reformer are as follows: methanol, ethanol, natural gas, gasoline, and diesel
fuel. These fuels that can be used to produce hydrogen gas are called hydrocarbons.
Hydrocarbons are substances that are primarily made up of hydrogen and carbon
atoms, and are rich in energy. Fuel reforming is a fairly simple process; take
a hydrocarbon fuel, combine it with heat and steam at very high temperatures,
and separate out the hydrogen gas (Breakthrough 30). From this process there
are emissions of carbon monoxide, carbon dioxide, and nitrous oxides that are
greenhouse gasses. As of now there is very little hydrogen produced around the
world, though, ninety-percent of the hydrogen gas produced around the world is
produced thermo chemically by this method when making a gas called synthesis
gas, also known as syngas (Ogden 653).
Another mentionable process of
producing hydrogen gas is using algae and bacteria. Certain microscopic algae
and bacteria produce hydrogen gas during normal metabolic functions. A
cyanobacterium is one of the organisms that produce hydrogen gas. These
bacteria can live in the air or in water. They absorb light and heat from the
sun and break apart water in processes similar to electrolysis. They then use
that hydrogen for their own energy creating water once again, which can be
broken apart using energy from the sun (Breakthrough 31).
No matter the way one gets the
hydrogen to run a fuel cell the hydrogen is a very unique fuel. Hydrogen is a
low-density gas that is less dense than air, meaning it needs to be contained
in a pressurized cylinder, when stored in the gaseous state. Hydrogen is unique
also in the fact that it liquefies at –253oC, meaning it is possible
to store hydrogen in a liquid form. Hydrogen can also be stored in solid form
in a metal hydride, which can be converted easily back into hydrogen by the
addition of heat. Hydrogen, unlike many fuels, has a very low activation energy
meaning that for the hydrogen to combine with oxygen to create water and
energy, it takes a very small amount of energy. Hydrogen also has the highest
heating value of any fuel, meaning that it can hit temperatures that no other
fuel comes close to. Hydrogen gas is also non-toxic, meaning it will not hurt
people, animals, or the environment. Though each of these sources of hydrogen
have their pros and cons, the choice of the primary sources of hydrogen could
be decided on how the region of a certain area’s local resources can most
easily produce cost efficient hydrogen gas. By using this unique substance and
other renewable resources, emissions from the combustion of fuel could be cut
by eighty-percent. Hydrogen fuel cells electrochemical efficiency is around
sixty-percent of the energy that had been stored in the hydrogen fuel (Ogden
655).
No matter where the hydrogen fuel
comes from, the same chemical processes occur in the fuel cell. The hydrogen
fuel is fed into the fuel cell in an opening near the anode, the positive end
of an electrical circuit. The hydrogen will give up its one electron and become
a positive ion at the anode with the help of a catalyst. A catalyst is a
substance that promotes a chemical reaction to happen though it does not change
itself. The hydrogen ion will flow through the inside of the cell through the
electrolyte, a substance that allows ions to travel through it. While the
hydrogen ions are traveling through the inside of the fuel cell, the electrons
travel through an external circuit causing an electrical current that can do
work. Oxygen is fed into the cathode, the negative end of an electrical
circuit. The hydrogen ions go through the electrolyte and meet up with it’s
electron, and then combines with the oxygen to form water vapor. The water
vapor is then flushed out to keep from flooding the cell. This is the general
reaction that takes place in hydrogen fuel cells. Though, hydrogen fuel cells
are basically the same, the difference is the electrolyte used.
Phosphoric Acid fuel cells use a solution of phosphoric acid inside the
cell as the electrolyte and platinum metal as a catalyst. This cell has an
operating temperature of 150 – 200oC which is important because the
phosphoric acid fuel cell is forty-percent efficient at these temperatures,
though at lower temperatures the phosphoric acid is a fairly poor conductor of
ions.
Proton Exchange fuel cells use a solid organic polymer, called
poly-perflourosulfonic acid, which is a good ionic conductor and is less
corrosive than most acid based electrolytes. The Proton Exchange fuel cell uses
a mixture of metal alloys, primarily made up of platinum, for the catalyst. The
operating temperature for this fuel cell is around 80oC, which is a
relatively low operating temperature for a fuel cell or combustion engine. This
fuel cell can output from 50 to 250 KW of power, though this fuel cell is very
sensitive to fuel impurities.
Direct Methanol fuel cells are exactly what the name implies. They do not
require the fuel to be reformed. It just needs to be fed the methanol. The
anode catalyst can draw the hydrogen in the methanol right from the methanol.
This fuel cell get around forty-percent efficiency at operating temperatures of
50 – 100oC.The electrolyte used in this fuel cell is a polymer
membrane. These fuel cells are very interesting. Because of their very low
operating temperatures, they are expected to be used to power cell phones and
laptops in the future (Breakthrough 6).
Regenerative fuel cells are a relatively new type of fuel cell. These cells
take the concept of the Proton Exchange Membrane fuel cell and made it a closed
loop using solar photovoltaic cells to get electricity to electrolyze water
into hydrogen and oxygen gas. The hydrogen and oxygen is fed into the cell and
out come water that is again electrolyzed by the solar cells.
Alkaline fuel cells are fuel cells that use a solution of alkaline
potassium hydroxide soaked in a matrix as the electrolyte. This cell has power
generating efficiencies of around seventy-percent efficiency at operating
temperatures of 150 – 200oC. The output of this cell is about 300
Watts – 5 KW. One of the biggest advantages of this fuel cell is that the
cathode reaction is much faster, meaning higher performance.
Molten Carbonate fuel cells are fuel cells that use a solution of
lithium, sodium, and/or potassium carbonates as the electrolyte. This fuel cell
has high-fuel-to electricity efficiencies that are around sixty-percent of the
energy contained in the hydrogen fuel at operating temperatures of 650oC.
This fuel cell outputs 10KW to 2 MW, though because of it’s extremely high
operating temperatures the components of the fuel cell tend to corrode and
break down after a certain period of time.
Solid Oxide fuel cells use a hard ceramic material of solid zirconium
oxide and a small amount of yttrium as the electrolyte to conduct the ions.
This fuel cell has an efficiency of around sixty-percent at normal operating
temperatures of 1000oC. This fuel cell has an output around 100KW
and is very useful in industrial and large-scale power generation (Breakthrough
4).
Though these fuel cells with different electrolytes have been around for
quite some time, their first practical applications took place merely around
forty years ago. NASA’s space programs were the first to use fuel cells in a
practical sense. It was on the Apollo and Gemini space missions that fuel cells
were used to power the space shuttles to the moon and back. Not only did these
fuel cells provide the energy they needed to rocket into space, but it gave
them heat and water for the astronauts inside the shuttles (Ogden 655). Since
these space shuttles, some scientists have begun to work with fuel cells as the
end of fossil fuels becomes more evident and closer. Scientists have been able
to improve fuel cells to the point where to travel the distance one can with a
normal gasoline internal combustion engine, one can travel twice as far on the
same amount of hydrogen.
Recently there has been much advancement as we slowly realize a hydrogen
economy is the brightest future. In California, Nevada, and Germany, hydrogen
fueling stations have begun to open pushing forward the change from fossil fuel
to a hydrogen economy. As of 1999 car companies such as Daimler Chrysler, GM,
Toyota, and Honda have been developing fuel cell cars that they are predicting
to have on the commercial market in time for the middle of this decade around
2005 (Ogden 657). The Ford Motor Company released the following statement in
May of 1997:
“A modern hydrogen-powered vehicle would be much safer than the cars of
today… The hydrogen would be stored in one or more fiber wrapped composite
tank, that could survive a 50mph head-on collision, engulfment by diesel fuel
fire, and pressure greater than 2.25 times normal pressures without rupture”
(Breakthrough 34).
Ever since the early 1990’s the
world has been scrambling to enact “zero-emission-vehicle” regulations that
have been enacted in California, Massachusetts, and New York. The world has
been finding ways to store hydrogen and to make people convert to alternative
fuels. This has caused a large growth in the market for fuel cells. Currently
fuel cells account for $218 million and are expected to rise to $2.4 billion by
the year 2004 (1). Though these projections look as though the hydrogen economy
will happen in the next few years, it will likely take around twenty years
before the world has everything squared away and cost efficient ways of
producing hydrogen have been enacted. Throughout this conversion to hydrogen,
billions of dollars will be spent, but when the big picture is looked at, it is
clear that it will save Americans billions of dollars once the hydrogen economy
has been enacted.
It is obvious that the conversion to
hydrogen fuel cells can and will be costly. This is a similar fact for
converting anything to an alternative option; it will always cost money to
convert. People around the world will save the money spent to convert to
hydrogen in turn once the most cost efficient methods of producing hydrogen have
been put in place. Fuel cells will also lower noise pollution and there will be
much less emissions of greenhouse gasses into the atmosphere, making for a
better environment for the future children of the world. Though this technology
has been around for about one hundred and fifty years it is now getting some of
the attention it should have long before internal combustions engines had ever
been introduced to the commercial market. This is one issue that will not be
ignored for much longer if people around the world have any conscience.
Works Consulted
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Kaufmann Inc., 1975.
“Fuel Cell”, Microsoft Encarta Encyclopedia 2000.
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Golob, Richard, and Eric Brus. The Almanac of
Renewable Energy. New York, NY: Henry Holt and Company Inc., 1993.
Hoffman, Peter. “Hydrogen Fuel Cell Letter – November
2002.” http://www.hfcletter.com/november02/features.html.
(November 9, 2002).
Ogden, Joan M. “Hydrogen”. Macmillan Encyclopedia of
Energy. 2000.
Stephenson, Stan. “Hydrogen: The Next Step?” Motor
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(November 9, 2002).