Isn't the big win of superconductors that you can build batteries with them? Like, you just pump them full of power that goes round and round forever with no or trivial losses. I always heard that this was why they were interesting.
It's an interesting idea worth exploring. The two places where I think feasibility may face challenge is in the energy density gated by critical current density and magnetic field and in raw discharge rate (giant inductors are not known for being able to change their current quickly).
Knowing peak capacity and aging is also tricky since you can't measure critical limits without hitting a quench (a very, very bad scenario). You'll need to maintain healthy margins so you don't have things blowing up on sunny days or after so many charge/discharge cycles.
https://en.wikipedia.org/wiki/Superconducting_magnetic_energ...
Compare with this table:
https://en.wikipedia.org/wiki/Energy_density#In_chemical_rea...