A simple experiment that to prove the potential energy is unlimited.

[Zhang Yalin]

Drop a bottle of liquid gas (V=1M3 ) into a deep pool of 10 meters, burned the gas out, The buoyancy of the empty bottle will do work: W=G(water)H=10000N*10M=100000J.
The shortcoming: The operation is not working continually.
(It's the rudiment of perpetual motion machine)

[hansvonlieven]

What about the energy needed to compress the gas inside the bottle in the first place. Where do you account for this?

Hans von Lieven

[Zhang Yalin]

If the bottle has not been dropped into the water, the energy used to compress the gas inside the bottle can't  be unconsumed.

[Pirate88179]

No offense intended but that argument would be like saying that since you can't return the batteries you purchased to the store, you don't have to allow for the energy inside them in your equation.  Or, that since the batteries were already made anyway, their energy does not count.  I mean this in a constructive way and I am not trashing your idea.  Thinking is good.

Bill

[Zhang Yalin]

Thank you,  My proposal is to find a way to kill the gravity of the objects by doing no work. For example:
burn up a pile of wood into ashes.