Fuel Cells and the Hydrogen Economy
''Water. Water decomposed (by electricity) into
its primitive elements ... yes, my friends, I believe that water
will one day be employed as the fuel, that hydrogen and oxygen
will constitute it ... that water will be the coal of the future.''
-Cyrus
Harding, from Mysterious Island by
Jules Verne
Quote taken from http://www.evworld.com/databases/shownews.cfm?pageid=news051102-08
A promising and environmentally friendly prospective
power source for future cars is fuel cells. Fuel cells are the
most likely long term solution to the search for a feasible ZEV. They
operate by reacting hydrogen and oxygen through a semipermeable
membrane, producing water and energy in the form of electricity
as products. In one type of fuel cell, hydrogen enters on one
side of the membrane and sends protons through the membrane and
electrons through an attached wire. The moving electrons create
a current that powers the car, and then on the other side of the
membrane the electrons, protons, and oxygen from the outside air
combine to form water (see diagram below). Fuel cells operate
far more efficiently than combustion engines.
Picture courtesy of http://www.ucsusa.org/clean_vehicles/advanced_vehicles/page.cfm?pageID=210
The most desirable fuel for a fuel cell car is pure
hydrogen, because it results in water vapor as the only emission. Thus
when using pure hydrogen a fuel cell car is a true ZEV. Hydrogen
can also be obtained from other fuels via a process called reforming,
but this causes some emission of carbon dioxide and other gases. Still,
a fuel cell car that uses reforming creates far lower emissions
than a conventional car. Examples of fuels for reforming are methane,
methanol, ethanol, and gasoline.
The environmental appeal of pure hydrogen as a fuel
has created the vision of a "hydrogen economy" in the future. As
the main energy source in this future system, hydrogen would be
mass produced and shipped by pipelines or tanks. At present there
is no method of obtaining large quantities of hydrogen that is
both environmentally clean and economically feasible. The use
of solar power to generate hydrogen by electrolysis of water is
an attractive solution, but currently suffers high costs. Thus,
just as hybrid vehicles signify an intermediate step towards a
ZEV, use of reforming to create hydrogen might be adopted as an
intermediate step until a workable method develops for obtaining
hydrogen from a clean and renewable source.
Fuel cells are still in a testing stage and continue to present
technical as well as economic challenges to development. Yet buses
operating on them are in use in Chicago and Vancouver, and many
auto manufacturers have announced intentions to begin sale of fuel
cell passenger cars between 2003 and 2005. Such a goal is ambitious
though, and large scale availability of fuel cell cars will probably
not come about for at least another decade.
Sources:
Bocarsly, Andrew. "Fuel Cells." Chemistry
333 class. Frick Laboratory, Princeton University. 7 Oct. 2002.
http://www.ccities.doe.gov/vbg/consumers/future.shtml
http://www.ucsusa.org/clean_vehicles/advanced_vehicles/page.cfm?pageID=208
http://www.ucsusa.org/clean_vehicles/advanced_vehicles/page.cfm?pageID=210
http://www.evworld.com/databases/shownews.cfm?pageid=news051102-08
http://www.fueleconomy.gov/feg/fuelcell.shtml
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