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Comment by ben_w | Hacker News Reader

10,000 km? I wonder how many amps that can carry.

(I have occasional daydreams of a global power grid; four of these reactors would have enough superconductor to go around the equator).

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ReBCO still isn't practical for grid transmission AFAIK. It needs to be cooled to something like 20 K to achieve high current. That's ~4x warmer than traditional superconductors (~4.5 K) but it's still not "high temperature" by anyone else's standards.

But you wouldn't be able to use it in that application because you can't keep it cool enough.

Tens of kiloAmps.

Wouldn't a superconductor theoretically be able to carry infinite amps? since it has zero resistance? (I=V/R etc)

There is a critical magnetic field at which superconductors stop being superconductive [1]. Generally, a superconductor carrying a lot of current suddenly becoming conductive is a bad thing. This is directly related to the maximum current density in a particular superconducting wire, so you need larger cross sections to increase the current carrying capability.

[1] https://en.wikipedia.org/wiki/Critical_field

More current produces a stronger magnetic field around the conductor, and superconductors usually have a maximum magnetic field beyond which they stop superconducting.

Not really, at a certain amount of current (how much exactly depends of the shape and material of the superconductor in question) it "quenches", where it abruptly goes back to being a material with non-zero resistance. Since there is usually a ton of current already flowing through the material, this usually leads to damage as the former superconductor heats up rapidly.

Nah, but easy misconception. Rearrange it as V=IR and that formula tells you there’s no voltage drop across the superconducting bit regardless of current.

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