Burning water into helium and loose oxygen sounds very tricky. For starters where does the helium come from. You could fuse together two hydrogen atoms to get helium, but that isn't really burning, that's nuclear fusion.
As for the first part I'll hold my hands up and say I have no idea what that means. As I understand it you could call water 'hydrogen ash' as it is fully oxidised (burnt) hydrogen. So how do you burn something that is already burnt? And how do you store energy by doing so
