I know this isn't just a simple problem, and it depends on a lot of things like the critical magnetic field at various temperatures, etc. And I'm still learning to calculate things like inductance and how that (eventually) relates to power. But suppose there were a material that was a superconductor all the way up to, say, 100 degrees Celsius, that material would in theory have a very high critical magnetic field. Things I'm specifically curious about is, let's say I wanted to store 5 MWh in a superconductor (yes, I know it's an absurdly high amount of power, especially when you read the next part, but keep in mind this is all theoretical guessing game stuff). How do I figure out the following: If I were to store that 5 MWh in a ring 10m in diameter, and X thickness (no clue here...), what sort of magnetic field would be generated external to that ring, and what would that field look like? Similarly, what if I wanted to do the same thing in a ring 1m in diameter (or 10cm), how would that change the magnetic field, in terms of its size, shape, strength, etc? And I guess finally, is there any way to cancel that magnetic field (to some degree)? Possibly by using 2 rings instead of one, which generate forces opposite to eachother?