i know i'm probably totally wrong with this, but i need someone who knows what he's talking about to tell me exactly where, and why, here's a quick sketch of the idea i drew and scanned/edited a little...it sorta explains itself, electrolysis(or however its spelled) turns water into hydrogen and oxygen, which then goes up a tube with a one way gate(like the ones used on a beach ball to keep the air in while you inflate it, or a water gun to shoot the water up front and not back into the tank) and goes trough a turbine, propelling it,(thus already generating, somewhat energy, ) then up to a electricity produced spark, combusting, exploding, and turning back into water, it is already well known how to make electricity out of combustion and explosion(it's essentially how cars work, i think?) and since it turns back into water, it will fall down* by gravity, pass trough another turbine(turning it, and thus exploiting gravity) and then be recycled back into the initial container.
so far we have 4 sources of electricity: 2 turbines, one combustion, and one source of explosions, we connect all of this to a battery's input and then we connect the output to the electrolysis and the spark ,(making the device self sustaining) and to an outlet, so if we made this device big enough it could power a house off the grid, (i suppose we'd have to take into account standards, and a bunch of other stuff...) being completely independent of the sun or anything else(except for gravity)
*if the water was liquid, it would fall, if gas, it would be made to pass trough a chamber where it would condense, and eventually still fall...
please forgive my terrible english