Beware the evils of dihydrogen monoxide.

Not abusing MedMech here, but I am gunning for the concept of fuel cells. Fuel cells are an idea in search of an application. Aside from space craft, I can't think of a good use for them that couldn't be more economically addressed by diesel.

All that energy put into formation and sequestration of high pressure explosive gas for so little reward in motive force. True, the immediate product is harmless so it has immediate environmental appeal. It is also quiet. Nobody has to put-up with those damnedable rice-rockets and their resonators.

Somebody somewhere had to consume a lot of energy in some original form to produce 2 moles of hydrogen for each mole of oxygen. So we use a coal-fired plant to produce energy needed to produce hydrogen and oxygen through electrolysis. How much energy goes into electrolysis?

What's the carnot efficiency of a fuel cell? Pretty high compared to internal combustion, I'd guess. But the other half of the story is the creation, distribution and storage of the gases. Energy-wise, how does that compare to diesel fuel production, storage and distribution?