Fuel cells combine hydrogen (from a tank) and oxygen (from the air) to make water and electricity (to power, say, an electric car motor). They're heavy, and you need a bunch of them to move a car. You probably don't want to try to move an 18-wheeler with them.
There's another way to get at the potential energy of hydrogen, though: burn it (well, it's still oxidation, but it is a lot more explosive), as pointed out in the Wired News article, "Truckers Choose Hydrogen Power." By adding hydrogen to the air-fuel mixture of a standard diesel engine, you get a bigger bang for your buck. And by splitting the source hydrogen from water as you go, you don't need a big, pressurized tank of explosive gas in your vehicle. However, the article says the electricity used to split the water is taken from the engine's alternator--it almost sounds like a perpetual motion machine. Obviously not, as you're still using lots of diesel fuel (simply a bit less, with the hyrdogen's help), and I'm sure alternators on cars and trucks everywhere are producing an overabundance of electrical potential that's going unused, so that you're not taking undue energy to feed an inefficient process (alternator electricty splits water to create hydrogen that's burned in engine that spins alternator to create electricity). Just based on the laws of physics, though, you have to figure that using an engine's rotational energy to spin some coils of wire through a magnetic field is using some little bit of energy, and that's going to cost you more fuel, even if you use the electricity to create hydrogen to reduce your fuel cost.
If drawing off the alternator to split water is taxing, however, my suggestion: throw some solar panels on top of that big rig.
Or just screw it. Nobody said internal combustion was efficient.

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Posted by erik to HipSmart at 11/16/2005 10:07:33 AM