The PEM fuel cells in most FCVs
use hydrogen to produce electricity. The hydrogen, however,
can be supplied in several ways.
Pure hydrogen. FCVs can be fueled with pure hydrogen
gas stored in onboard fuel tanks. Since hydrogen gas is diffuse,
it must be stored in high- |
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pressure tanks in order to store enough to travel
reasonable distances on a full tank of fuel. Currently used
tanks, which allow hydrogen to be compressed to 5,000 pounds/square
inch (psi) of pressure, can only store enough hydrogen gas to
allow FCVs to go about 200 miles before refueling. However,
manufacturers are designing and testing tanks that will store
more hydrogen at a higher pressure. |
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In addition to onboard storage problems,
our current system for getting liquid gasoline to consumers
can't be used for gaseous hydrogen. Therefore, new facilities
and systems would have to be built, requiring significant time
and resources. |
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Hydrogen-rich
fuels. FCVs can also be fueled with hydrogen-rich fuels, such
as methanol, natural gas, petroleum distillates, or even gasoline.
These fuels must be passed through onboard "reformers"
that extract pure hydrogen from the fuel for use in the fuel cell.
Reforming does emit some carbon dioxide (CO2), but much less than
gasoline engines do.
The fuels mentioned above contain enough hydrogen to allow FCVs
to travel the same distance as a conventional vehicle on a single
tank of gas; about 300 to 400 miles. Also, unlike hydrogen gas,
liquid fuels like methanol and gasoline wouldn't require a completely
new system for delivering fuel to consumers.
Although there are advantages to powering FCVs with these fuels,
there are also several disadvantages.
- Onboard reformers add to the complexity, cost, and maintenance
demands of a vehicle's fuel cell system.
- If the reformer allows carbon oxides to reach the fuel cell
anode, it can gradually decrease the performance of the cell.
- Reformers produce small amounts of greenhouse gases and other
air pollutants.
It is not yet clear which method of fueling fuel cells will prevail.
Research and development continues for all of these fueling options.
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