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Physicists May Be One Step Closer To Explaining High-Temp Superconductivity
sciencehabit writes For years some physicists have been hoping to crack the mystery of high-temperature superconductivity—the ability of some complex materials to carry electricity without resistance at temperatures high above absolute zero—by simulating crystals with patterns of laser light and individual atoms. Now, a team has taken—almost—the next-to-last step in such 'optical lattice' simulation by reproducing the pattern of magnetism seen in high-temperature superconductors from which the resistance-free flow of electricity emerges.
You will always have heat buildup to deal with in any system that does something useful.
Superconducting magnets are useful, even if they're not doing work.
138K = -211F
The key threshold is 77K. Above that, and you can cool with liquid nitrogen. A liter of liquid N2 costs less than a liter of milk. A liter of liquid helium costs about a hundred times as much.
Even though there are higher temperature superconductors, and even if room temperature superconductors are discovered, MRI machines will probably continue to use liquid helium. Superconductivity not only stops when a critical temperature is exceeded, but also when critical magnetic fields are exceeded, and the magnetic field limit increases with lower temperature. So a lot of LN2 superconductors are still used with liquid helium, because you then can have more current and hence more magnetic field for using less superconducting wiring. Higher fields for MRI machines mean more options like higher SNR, better resolution, or quicker measurements. I would expect ambient magnetic field MRI equipment (using Earth's magnetic field with sensitive detectors like SQUIDs) would be the direction low cost, non-cryogenic MRI machines to take in the future if room temperature superconductors were found.
The highest temperature superconductor (HgBa2Ca2Cu3Ox(HBCCO) acts at temperatures at or below -140C (-220F). That is still darn cold. Dry Ice sublimates at -78C. What I would consider practical would be around -5C (which means we have 140C to go). Some would want it to be 25C or higher, but you could run a 'national grid' at -5C where "power pumped in" = "power pumped out" without loss. And it would save I2R losses by boatload. Clearly when you look at the number of chemicals and the structure of what they are creating to get to superconductivity, shotgunning it may not be as good as a sound theory of how things work. Every advance gets us closer to a crapload of money and the ability to use electric cars using a power grid similar to what we have now.