Superconductors have for decades spurred dreams of extraordinary technological breakthroughs, but many practical applications for them have remained out of reach. Now a new study reveals what may be the world’s highest-performing high-temperature superconducting wires yet, ones that carry 50 percent as much current as the previous record-holder. Scientists add this advance was achieved without increased costs or complexity to how superconducting wires are currently made.
Superconductors conduct electricity with zero resistance. Classic superconductors work only at super-cold temperatures below 30 degrees Kelvin. In contrast, high-temperature superconductors can operate at temperatures above 77 K, which means they can be cooled to superconductivity using comparatively inexpensive and less burdensome cryogenics built around liquid nitrogen coolant.
Regular electrical conductors all resist electron flow to some degree, resulting in wasted energy. The fact that superconductors conduct electricity without dissipating energy has long lead to dreams of significantly more efficient power grids. In addition, the way in which rivers of electric currents course through them means superconductors can serve as powerful electromagnets, for applications such as maglev trains, better MRI scanners for medicine, doubling the amount of power generated from wind turbines, and nuclear fusion power plants.
“Today, companies around the world are fabricating kilometer-long, high-temperature superconductor wires,” says Amit Goyal, founding director of the University at Buffalo’s RENEW Institute in New York.
However, many large-scale applications for superconductors may stay fantasies until researchers can find a way to fabricate high-temperature superconducting wires in a more cost-effective manner.
In the new research, scientists have created wires that have set new records for the amount of current they can carry at temperatures ranging from 5 K to 77 K. Moreover, fabrication of the new wires requires processes no more complex or costly than those currently used to make high-temperature superconducting wires.
“The performance we have reported in 0.2-micron-thick wires is similar to wires almost 10 times thicker,” Goyal says.
At 4.2 K, the new wires carried 190 million amps per square centimeter without any externally applied magnetic field. This is some 50 percent better than results reported in 2022 and a full 100 percent better than ones detailed in 2021, Goyal and his colleagues note. At 20 K and under an externally applied magnetic field of 20 tesla—the kind of conditions envisioned for fusion applications—the new wires may carry about 9.3 million amps per square centimeter, roughly 5 times greater than present-day commercial high-temperature superconductor wires, they add.
Another factor key to the success of commercial high-temperature superconductor wires is pinning force—the ability to keep magnetic vortices pinned in place within the superconductors that could otherwise interfere with electron flow. (So in that sense higher pinning force values are better here—more conducive to the range of applications expected for such high-capacity, high-temperature superconductors.) The new wires showed record-setting pinning forces of more than 6.4 trillion newtons at 4.3 K under a 7 tesla magnetic field. This is more than twice as much as results previously reported in 2022.
The new wires are based on rare-earth barium copper oxide (REBCO). The wires use nanometer-sized columns of insulating, non-superconducting barium zirconate at nanometer-scale spacings within the superconductor that can help pin down magnetic vortices, allowing for higher supercurrents.
The researchers made these gains after a few years spent optimizing deposition processes, Goyal says. “We feel that high-temperature superconductor wire performance can still be significantly improved,” he adds. “We have several paths to get to better performance and will continue to explore these routes.”
Based on these results, high-temperature superconductor wire manufacturers “will hopefully further optimize their deposition conditions to improve the performance of their wires,” Goyal says. “Some companies may be able to do this in a short time.”
The hope is that superconductor companies will be able to significantly improve performance without too many changes to present-day manufacturing processes. “If high-temperature superconductor wire manufacturers can even just double the performance of commercial high-temperature superconductor wires while keeping capital equipment costs the same, it could make a transformative impact to the large-scale applications of superconductors,” Goyal says.
The scientists detailed their findings on 7 August in the journal Nature Communications.
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