It's hard to distinguish the humor
from the science in this one. But I'll add a few facts and opinions on the subject (as a chemist). First, the total weight (mass) of hydrogen and oxygen needed to make water is exactly the same as the weight of water that you receive. Second, there is no hydrogen roaming around in the air. In fact, hydrogen is so light that it has "escape velocity", i.e., if you release hydrogen it will eventually escape the earth's magnetic field and drift off into space.
I never understood the idea of a hydrogen economy! It is one of the worst things to handle. It isn't explosive by itself but it forms explosive mixtures in air at a really wide range of concentrations. It is damned near impossible to contain. It leaks
out of most materials and "reacts" with most metals to make them brittle and porous. Systems that use hydrogen are always replacing the tubes, valves, etc. I think I'd rather have an equal weight of military high explosive on my boat than hydrogen.
I think most commercial
hydrogen comes from oil
refining. But the fuel
companies use it as fast as they make it because it improves the quality of their fuels (when reacted with the feedstock). You can make hydrogen from seawater. But as pointed out: It takes a LOT
of energy. We don't "make" energy except in nuclear reactors, including the sun!. We just collect it, store it and move it around. It turns out that diesel fuel
is just about the highest energy density that you can get. If I'm not mistaken diesel
has about three or four times the energy per gram as TNT. It's just that TNT releases it faster! You can certainly collect energy from the sun with efficiencies around 20% for the conversion to electricity.
Most scientists learn something about Thermodynamics. There are lots of thermodynamic laws and principles (including Boyles Law) but there are three fundamental laws of Thermo. In layman's terms they are:
1. You can't get something for nothing. (Conservation of Energy)
2. You can only break even at absolute zero. (Entropy)
3. You can't reach absolute zero.
So, you are always going to lose energy. And that's OK for most things but don't look for perpetual motion!
Enough hydrogen-oxygen-dehydrated water stuff.
But, water is a big problem and there is a lot of research
in trying to come up with better ways to get it...mostly get the salt
out of it. So far RO seems to be the best but it does take energy. It's actually the second law above that comes to play here. And there is a lot of effort going into better membranes. But one of the biggest problems is fouling. The more efficient membranes tend to foul faster. Keep our fingers crossed, better ones are on the way. I think that carbon nanotubes are probably useful for making a strong, thin membrane because they have unbelievable strength properties. They are probably not (at this time anyway) useful as pores because most nanotubes are not open from end to end.
As for fuel cells, they don't generate enough water to keep a flea alive. Most of them don't generate enough to keep their membranes wet. And hydrogen fuel cells have all of the disadvantages of managing hydrogen gas. But there is a lot of work on hydrocarbon and alcohol fuel cells that would really help the cruiser run all of our "needed" systems. The holy grail here is a fuel cell
that will "burn" JP-8 (diesel). But it's the catalyst/membrane that's holding that up as well. Maybe one of these days.
Whew! Is that pedantic enough??