Fuel Cell Vehicles - the ZEVs of the future?
Another type of Zero-Emission Vehicle is the
fuel cell powered
vehicle. When the fuel cells are fueled with pure hydrogen, they are
considered to be zero
emission vehicles. Fuel cells have been used on spacecraft for many
years to power
electric equipment. These are fueled with liquid hydrogen from the
Fuel cell vehicles turn hydrogen fuel and oxygen into electricity.
then powers an electric motor, just like electricity from batteries
powers the motor of an
electric vehicle. Fuel cells combine oxygen from the air with
hydrogen from the vehicle's
fuel tank to produce electricity. When oxygen and hydrogen are
combined they give off
energy and water (H2O). In fuel cells this is done
without any burning
(combustion). A graphic showing how a typical fuel cell works is
When we think of vehicles that are fueled with hydrogen, we may
think of rocket-powered
spacecraft, like the space shuttle. The space shuttle is fueled with
liquid oxygen and
liquid hydrogen. To fly, the oxygen and hydrogen are mixed together
and ignited to make a
very hot fire. The expanding gases from that fire are what propel
the spacecraft. The
exhaust from spacecraft rocket motors (and hydrogen-fueled fuel
cells) is mostly water.
That is why hydrogen-fueled fuel cell vehicles are also ZEVs. Very little is
exhaust except water. Fuel cells do get hot though, so the water
comes out of the fuel
cells as water vapor, or steam.
There are a number of ways that hydrogen can be provided to the
fuel cell. One way is
simply to put hydrogen gas into the fuel cell, along with air.
Hydrogen gas can come from
gaseous or liquid hydrogen stored on the vehicle.
To carry gaseous hydrogen on a vehicle, it must be compressed.
(usually to a pressure of about 3000 pounds per square inch), it must
be stored in special
high-pressure containers. This is similar to the way compressed
natural gas is stored on
natural gas-fueled vehicles.
The other way to provide hydrogen gas to the fuel cell is to store
it on the vehicle in
liquid form. To make hydrogen liquid, it is chilled and compressed.
Liquid hydrogen is
very, very cold--more than 423.2 degrees Fairenheit below
zero! This super-cold
liquid hydrogen is the kind used in space rockets. The containers
are able to hold
pressure, but they are also insulated to keep the liquid hydrogen
from warming up.
Warming the liquid, or lowering the pressure, releases gas (like
boiling water), and the
gas can go to the fuel cell.
Another way to get hydrogen to the fuel cell is to use a
"reformer". A reformer is a
device that removes the hydrogen from hydrocarbon fuels, like
methanol or gasoline. When
a fuel other than hydrogen is used, the fuel cell is no longer
zero-emission, but it still
may be very low emitting.
There is also a type of fuel cell that can be fueled with methanol
directly. This is
called a direct-methanol fuel cell. This type of fuel cell does not
need a reformer to
separate the hydrogen from the methanol. The fuel cell removes the
hydrogen from the
liquid methanol inside the fuel cell.
Many people in the vehicle manufacturing business think that fuel
cell vehicles may be
the technology of the future. However, a lot of work will have to be
done to make fuel
cell vehicles perform well enough to replace the internal combustion
engine in the vehicles we use today. They also
will need to be made much less expensive.
At present, fuel cell vehicles have only been developed to what
might be called the
pre-prototype stage. That means there are very few fuel cell
vehicles in existence, and
all of them are actually used for testing. Most car manufacturers
have or are working on
demonstration models, some of which can reach a speed of 90 mph and
can travel up to about
280 miles before they need refueling. DaimlerChrysler has developed the NECAR
4 (pictured above) and Ford calls its demonstration model the
Some manufacturers claim they will have fuel cell cars
available for the public in the next ten years.
Find out more about fuel cell vehicles by going to the California
Fuel Cell Partnership web
site called Driving the Future.
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