You guys are kicking yourselves in the a$$, figure I'll jump in. The way I see it. The alternator is making the power anyway. Of course it's a net loss (if it broke even I believe you would have solved the energy crisis,) but who cares? The alternator is capable of making more electricity than than the system needs, it fact it does that often. So, if you can use that excess electricity to some good then your recouping some of that inefficiency. Even if what you do with that energy is inefficient, any return is a net gain.
Second, it takes heat to create water, but that doesn't mean that the Hydrogen is burnt. When you start with water then the energy used to create the water doesn't matter (to your wallet anyway.)
Third, I don't know who told you that 100W isn't enough to break the chemical compound, but I've referred to a MM chief that does this for a living and he says it takes way less than that, although he did say the more the merrier to a point. I trust him, if it wasn't for the wonderfull Oxygen he creates I wouldn't be able to breathe in my steel tube under water.
Waiting to be roasted..
Ron