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EV vs. Fuel Cell
Fuel Cell: Invented in 1830, a device which converts chemical energy directly into electricity
by an electrochemical process, refined and made practical during the 1960's. Primary power source for manned US
Space missions, using Hydrogen and Oxygen. Features/problems:
- Requires a Carbon-free supply of pure Hydrogen gas,
- Reaction itself emits only water;
- Has needed a catalyst or hi-temperature reaction chamber;
- Oxygen supply may come from ambient air;
- Hydrogen can be supplied by closed, hi-pressure tanks;
- Hydrogen can be the output of a reformer, which breaks down methanol or other fuel into
Hydrogen and other byproducts;
- Time gap before electricity delivered: 10-15 seconds;
- Under intense development for the last 40 years.
Drawbacks: Carrying Hydrogen (for mobile applications), energy loss, prohibitive
cost (both mobile and stationary applications), low energy density.
There has been a lot of speculation lately that the FUEL CELL will be the ultimate mode of power for transportation
in the future. This may very well be true.
Fuel Cell technology has come a long way since the early days in the Apollo space program. Certainly the idea
of running a car on pure hydrogen is an exciting prospect, the only emissions would be pure water.
Water is composed of hydrogen and oxygen (H2O) and by adding electricity (electrolysis) pure hydrogen and oxygen
gas can be extracted. A fuel cell does the reverse: from the Hydrogen and from Oxygen in the air, the right device
(a fuel cell stack) will generate electricity which can then be used to power an electric motor.
The only waste product is water.
A fuel cell is a complicated device requiring a lot of plumbing and the fuel stack itself (the heart of the
system) is still extremely expensive... more expensive than the NiMH batteries used in a pure EV although both
the cost of the fuel cell stack and the NiMH batteries would come down dramatically in any volume production.
In practice, electrolysis of water is much too expensive and inefficient for Hydrogen generation. Usually, Hydrogen
is produced by chemical reaction from the breakdown of CarboHydrates. One of the most challenging questions regarding
fuel cells (assuming they were affordable) is how to separate all the Carbon out, and how to store it.
Compressing the hydrogen into a high pressure tank is one option although some people might not be comfortable
with highly compressed hydrogen tanks in the car (oddly enough, people ARE comfortable with flamable/toxic gasoline
though so who knows). Even under tremendous pressure, you can't really store a lot of hydrogen in a vehicle in
this fashion. Prototype compressed hydrogen fuel cell vehicles have a range of about 100 miles, not
exceeding the current state of pure electric (battery) vehicles. Other exotic methods of storing pure hydrogen
are being investigated including storing it in a sponge-like metalic device that would soak up hydrogen in a higher
density than you could normally compress it. Of course even if we could store enough pure hydrogen on the vehicle,
where would we get it? Your local hydrogen fuelling station? That's a huge infrastructure to install.
You could of course pull hydrogen from water by using electricity but if your goal is a vehicle that only goes
100 miles, it is much more efficient to put the electricity directly into a battery on the vehicle. It's far less
efficient to use electricity to pull hydrogen out of water, then compress the hydrogen into a tank on the car then
run the hydrogen through a fuel cell to get the electricity back than it would be simply to store it in a battery.
You might also use what is called a REFORMER to pull hydrogen out
of a liquid fuel like methanol, natural gas or gasoline. This brings us to the second big problem with fuel cells.
The most likely fuel cell vehicle in the near future (2004+) would probably use on board reformer to convert
a liquid fuel on the vehicle to hydrogen to run through the fuel cell. If you are able to use a large on-board
reformer to pull the hydrogen out of methanol for example, you are still left with additional carbon from the gas.
These extra pollutants would show up as additional emissions from the vehicle, most likely in the form of carbon
dioxide, a green-house gas. Of course the situation gets even worse when you consider a gasoline reformer as gasoline
is a much more complicated fuel than methanol and you'd have a lot of other odd products left over as a result
of the "cracking" process. Would we really want to keep using gasoline anyway? Even though the infrastructure
is already in place, the total fuel cycle emissions from gasoline is enormous including of course oil drilling,
transportation cost (including spills), refining and distribution, not to mention the political upheavals and threatened
and actual wars fought to protect the oil in the first place.
Even considering the marvels of modern technology, and the amazing devices we use every day, all in all the
prospects of a pure hydrogen fuel cell vehicle still seems a long ways off.
A pure hydrogen manufacturing, distribution and fueling infrastructure would take a long time to replace the existing
gasoline infrastructure, and involves unknown risks and expenses (and by-products). On the other hand, by contrast
a battery powered electric uses an infrastructure that is already available throughout the United States, simple
household electricity.
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