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Comment by ajago | Hacker News Reader

Can you elaborate on this please? How can superconductors be used for storage?

Basically, just push more and more electricity into a coil of superconductive wire. Because the wire has no resistance, the electricity just loops around forever.

https://en.wikipedia.org/wiki/Superconducting_magnetic_energ...

For now, this is restricted to special applications due to great size and cost. The great size and cost are caused mainly by the cooling systems.

The magnetic field of a superconducting electromagnet contains a lot of energy because the field can be very strong with a large cross section. It’s the conjugate of a capacitor after all, it’s just that the energy density of normal inductors is much lower than that of capacitors. Using a superconductor also avoids resistive losses for (dis)charging.

(Inductors are very frequently used for very short-term energy storage (~fractions of a millisecond). For example, all energy output by a flyback converter was briefly stored in the transformer’s magnetic field. Unlike a regular transformer/forward converter, where the magnetic field is just a side effect of coupled inductors, so none of the energy is stored in it.)

But obviously you can't exactly carry multi-Tesla electromagnets around. So no car batteries, much less phone batteries. Large energy storage facilities for grid power regulation, possibly.

Could you shield them with mumetal? Maybe make tiny arrays of thousands of them each with smaller atorage surrounded by mumetal to let them be close. That way if they break it is only those along the break that would discharge instantly.

The quantities of energy released would heat up the material around it to the point that it may well lose its superconducting properties as well. Likely failure of any winding in such a setup would set off the rest as well unless there is a lot more separation. Mu metal has a relatively low saturation limit.

And that's before we get into the purely mechanical stresses created by such an event, which likely will destroy the vicinity of the carrier of the current.

Fermi check: Mu metal boxes are only good enough to reduce the influence of this planet's magnetic field, not eliminate, and that's a really weak field (in terms of flux density, it's of course also really freakin gigantic).

Well, they are used in electromagnetic shielding but you'd need an awful lot of it to overcome the kind of field that even a single winding of a superconductor puts out, my intuitive guess is that for any realistically available level of shielding that the magnetic field would punch right through it as if it wasn't there at all.

Just look at what happens if you leave something made out of metal lying around near an MRI machine when it is switched on and that's not for want of attempts to shield it.

If you will close it into ferrite cup as it is done today with coils, then all the magnetic field should be limited only on coil on ferrite material itself.

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