So you've not explained how this can be used as storage. Just because the conduction is free does not mean that the field interactions don't induce a load...
Consider: why does a permanent magnet stay magnetized even in a changing magnetic field? Why do two permanent magnets stay magnetized when you bring them together and apart again?
When you move through the magnetic field of a permanent magnet, no energy is drawn out from the permanent magnet. All of the work occurred externally. It's the same with an energized superconducting electromagnet. Its field will not be "stripped away" by interacting with magnetic objects. The flux might be reduced if you brought an opposing magnetic flux near it -- but it would be increased again when you moved it back away. Net zero work.
Consider: why does a permanent magnet stay magnetized even in a changing magnetic field? Why do two permanent magnets stay magnetized when you bring them together and apart again?
When you move through the magnetic field of a permanent magnet, no energy is drawn out from the permanent magnet. All of the work occurred externally. It's the same with an energized superconducting electromagnet. Its field will not be "stripped away" by interacting with magnetic objects. The flux might be reduced if you brought an opposing magnetic flux near it -- but it would be increased again when you moved it back away. Net zero work.