A new study suggests that large-scale, cost-effective application of high-temperature superconducting wire is increasingly possible. High-temperature superconducting (HTS) wires could define the future of our energy systems. Able to conduct electricity without resistance at higher temperatures than traditional superconductors, these advanced materials have the potential to transform the electrical grid and make commercial nuclear fusion a reality.

But these large-scale applications will not occur until HTS cables are produced at a price-performance ratio equal to the traditional copper cable sold at your local hardware store.

A new study led by the University at Buffalo brings us closer to that goal. In a study published in Nature Communications, researchers report that they have produced the world’s most efficient HTS wire segment while achieving a significant price-performance ratio.

Their rare-earth barium copper oxide (REBCO)-based wire achieved the highest critical current density and pinning force (the amount of electric current carried and the ability to pin magnetic vortices, respectively) reported to date for all magnetic fields and temperatures from 5 Kelvin to 77 Kelvin.

This temperature range is still extremely low (minus 451 degrees Fahrenheit to minus 321 degrees Fahrenheit) but higher than absolute zero, where conventional superconductors operate.

“These results will guide industry toward further optimizing deposition and manufacturing conditions to significantly increase the cost-effectiveness of commercial coated conductors,” said Amit Goyal, SUNY Professor Emeritus and SUNY Empire Professor of Innovation, the study’s corresponding author. He also holds a position in the Department of Chemical and Biological Engineering in the UB School of Engineering and Applied Sciences. “The price-performance ratio needs to be made more affordable to fully realize the many large-scale envisioned applications of superconductors.”

HTS wires have many applications

Applications of HTS wires include energy generation, such as doubling the power produced by offshore wind generators; stranded superconducting magnetic energy storage systems; energy transmission, such as lossless transmission of electricity in high-current direct and alternating current power lines; and energy efficiency through high-efficiency superconducting transformers, motors, and fault current limiters for the network.

Commercial nuclear fusion, which is just one niche application of HTS wires, has the potential to produce unlimited clean energy. In the last few years alone, approximately 20 private companies have been established worldwide to develop commercial nuclear fusion, and billions of dollars have been invested in the development of HTS wires for this application alone.

Other applications of HTS wires include next-generation MRI in medicine, next-generation nuclear magnetic resonance (NMR) in drug discovery, and high-field magnets for numerous applications in physics. There are also numerous defense applications, such as the development of all-electric ships and all-electric aircraft.

Most of the companies now producing kilometers of high-performance HTS cables around the world are using one or more of the platform technology innovations previously developed by Goyal and his team.

These include roll-assisted biaxially textured substrates (RABiTS) technology, ion beam-assisted deposition (IBAD) MgO technology, and nano-pillared defects at nanoscale distances using simultaneous phase separation and strain-driven self-assembly technology.

World record for critical current density and clamping force

In this study published in Nature Communications, Goyal’s group reports superconducting cables based on ultra-high-performance REBCO. The HTS cables at 4.2 Kelvin carried 190 million amperes per square centimeter without an external magnetic field, also known as the self-field, and 90 million amperes per square centimeter with a 7 Tesla magnetic field.

At a higher temperature of 20 Kelvin, the expected application temperature for commercial nuclear fusion, the wires can still carry more than 150 million amperes per square centimeter of their area, and more than 60 million amperes per square centimeter at 7 Tesla.

In terms of critical current, this corresponds to a 4 millimeter wide piece of wire at 4.2 Kelvin having a supercurrent of 1,500 amps in its field, or 700 amps at 7 Tesla. At 20 Kelvin, this is 1,200 amps in its field, or 500 amps at 7 Tesla.

Despite being only 0.2 microns thick, the HTS film developed by the team can pass a current comparable to commercial superconducting wires with an HTS film almost 10 times thicker.

In terms of pinning strength, the wires showed a strong ability to hold magnetic vortices pinned, or in place, with forces of about 6.4 teranewtons per cubic meter at 4.2 kelvin and about 4.2 teranewtons per cubic meter at 20 kelvin, both under the 7-Tesla magnetic field. field.

These are the highest critical current density and pinning force values ​​ever recorded for all magnetic fields and operating temperatures from 5 Kelvin to 77 Kelvin.

“These results demonstrate that significant performance improvements, and therefore associated cost reductions, are still potentially achievable in optimized commercial HTS cables,” says Goyal.

How was high-performance wire made?

The HTS segment of the wire was fabricated using nanopillar defects on (IBAD) MgO substrates and using simultaneous phase separation and strain-controlled self-assembly technology. The self-assembly technology allows the placement of insulating or non-superconducting nanopillars at nanoscale distances inside the superconductor. These nanodefects can pin superconducting vortices, creating higher supercurrents.

“The high critical current density is made possible by the combination of rare-earth doping, oxygen point defects, and pinning effects resulting from the insulating barium zirconate nanocolumns and their morphology,” says Goyal.

“The HTS film was created using an advanced pulsed laser deposition system with careful control of the deposition parameters,” adds Rohit Kumar, a postdoctoral researcher at UB’s Laboratory for Heteroepitaxial Growth of Functional Materials and Devices, which Goyal leads.

In pulsed laser deposition, a laser beam strikes the target material and removes the material, which is deposited as a film on a suitably positioned substrate.

“We also performed atomic-resolution microscopy using state-of-the-art microscopes at the Canadian Centre for Electron Microscopy at McMaster University to characterize nanocolumnar and atomic defects, and some measurements of superconducting properties at the University of Salerno in Italy,” Goyal says.