The battery one is crazy, where you just store the electrons in a loop.
You're basically storing your energy as magnetic potential. Pretty neat.
But how do you get them out? Don't electrons prefer the path of least resistance, so that is staying in the superconductor? Or they won't stand still?
Converting magnetic force into electrical current (electromagnetic induction) is the principal behind of all electrical power generation. SMES (superconducting magnetic electrical storage) is essentially an inductor made using superconductors. Electrical current gets converted into magnetic force and then back into electrical current when the circuit is discharged.
So they still generate permanent electromagnetic force when "charged"?