The "Water Fueled Car"

[Roland]

Furthermore, you wouldn't be emitting oxygen, you would be emitting WATER

Very true.

- the product of burning hydrogen.

Uh-oh. Not quite. The burning of Hydrogen ALONE does not produce water. It is the combination of one Oxygen atom plus two Hydrogen atoms and the application of fire that creates water. Hence the atomic breakdown of H2O. You can't just burn hydrogen (or anything, for that matter, that I know of) without oxygen as well, but your statement as it stands is a bit misleading.

Just had to nit that.:P

The problem with steam is the boiler itself. In order to make a useful steam engine, you need a high amount of pressure in order to turn a turbine (thus turning mechanical energy into electrical). It's this pressure that makes steam engines so inherently dangerous, and why they are not very popular in recent applications. They are much cleaner burning, provided you use a clean-burning fuel, but they are also much more dangerous. Gasoline engines use controlled mixtures of gasoline "mist" and oxygen, compressed down to extreme levels, and then ignited, creating a small explosion that drives a piston, which in turn moves a crankshaft, etc. But the reaction is much more controllable, and provided things aren't horrendously out-of-spec, much safer than a steam engine (or, rather, using a boiler).

I don't see steam as any savoir for our energy problems in this day and age. We got away from it for a reason - it would be a step backwards to start using it again for any large-scale applications (such as cars). A giant tank filled with 1,000 PSI (arbitrary numbers, mind you, for example's sake) of boiling hot steam is a very dangrous thing. Imagine what would happen in a car-crash - instant explosion of metal and steam. You'd be a moving bomb should anything go wrong. Just not a smart idea.