Closed Cycle Hydrogen Fuel Cell Question

[Ulzgoroth]

Originally Posted by davester65

By thermodynamics, do you mean the whole perpetual motion thing? The idea I had was that there would be some loss each time the water was reused, so that it would eventually run out, but that it would still use fuel more efficiently. Forgive me if I'm off, my knowledge of science isn't too detail oriented.

Related to that, and also to the 'conservation of energy' you may have heard of at some point.

What you're suggesting is flatly impossible. The energy extracted from a fuel cell comes from turning hydrogen and oxygen into water. Turning the water back takes the same amount of energy as making the water released. Except that both steps aren't perfectly efficient, so if you ran it forward and backward that way you'd wind up using up all the energy you got and not having enough to crack all the water to get back to where you started.