You're not getting it. First, no one claimed a perpetuum mobile, or that there's anywhere a conversion with 100% efficiency. You are probably the first one to mention that in this specific thread, BTW. Don't throw in universal truths or generalities just to make yourself look correct when no one were arguing about those.

In any case, the energy comes from the Sun, for completely free, and you can treat hydrogen as a carrier of energy, if you wish. The main advantage of hydrogen over other fuels is that it can be inherently greenhouse gas free. (all the way from generation) As far as I know, the only other, similarly clean and viable method is the battery based storage of electricity, but their weight to power ratio is nowhere near as good.