A new study shows that large-scale, cost-effective implementation 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 conventional superconductors, these advanced materials have the potential to transform the electrical grid and make commercial nuclear fusion a reality.
However, these large-scale applications won't happen until HTS wires can be manufactured at a price-performance ratio equal to that of conventional copper wire sold at your local hardware store.
New research led by the University at Buffalo brings us closer. to this end. In a study published in Nature Communications, the researchers report that they have produced the world's most efficient segment of HTS wire, while making the cost-performance ratio significantly better.
Based on Rare Earth Copper Barium Oxide (REBCO), their wires have achieved the highest critical current density and clamping force — the magnitude of the transmitted electric current and the ability to fix magnetic vortices, respectively — registered today for all magnetic fields and temperatures from 5 Kelvin to 77 Kelvin.
This temperature range is still extremely low — from minus 451 degrees to minus 321 degrees Fahrenheit — but higher than absolute zero , at which traditional superconductors work.
"These results will help the industry to further optimize their deposition and fabrication conditions to significantly improve the cost-effectiveness of commercial coated conductors,— says the study's corresponding author, Amit Goyal, PhD, SUNY Professor Emeritus and SUNY Empire Professor of Innovation. Department of Chemical and Biological Engineering in the UB School of Engineering and Applied Sciences. "To fully realize the many large-scale envisioned applications of superconductors, the price-performance ratio must be made more favorable".
HTS wires have many applications
Applications of HTS wires include energy production, such as doubling the power produced by offshore wind generators; mesh 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 in the form of highly efficient superconducting transformers, motors and fault current limiters for the grid.
Only one niche application of HTS wires, commercial nuclear fusion, has the potential to yield limitless clean energy. In the past few years alone, approximately 20 private companies have been founded 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 the next generation of MRI for medicine, next-generation nuclear magnetic resonance (NMR) for drug discovery, and high-field magnets for numerous applications in physics. There are also numerous defense applications, for example in the development of all-electric ships and all-electric aircraft.
Most of the companies around the world now making kilometer-long high-performance HTS wires use 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 nanocolumnar defects at nanoscale distances using simultaneous phase separation and strain-controlled self-assembly technology.
World record for critical current density and clamping force
In this work, published in Nature Communications, Goyal's group reports superconducting wires based on the ultrahigh-performance REBCO. At 4.2 Kelvin, the HTS wires carried 190 million amps per square centimeter without an external magnetic field, also known as self-field, and 90 million amps per square centimeter with a 7 tesla magnetic field.
At a higher temperature of 20 Kelvin – expected temperature of use for commercial nuclear fusion – the wires can still carry more than 150 million amps per square centimeter of self-field and more than 60 million amps per square centimeter at 7 tesla.
In terms of critical current, this corresponds to a 4 millimeter wide segment of wire at 4.2 kelvin, which has a supercurrent of 1500 amperes in its own field and 700 amperes at 7 tesla. At 20 Kelvin, this is 1200 amperes in its own field and 500 amperes at 7 tesla.
Notably, the HTS film developed by the team, despite being only 0.2 microns thick, can pass a current comparable to that of commercial superconducting wires with an HTS film almost 10 times thicker.
In terms of pinning force, the wires showed a strong ability to hold the 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 under the influence of a 7-tesla magnetic field. field.
These are the highest values of critical current density and pinning force reported to date for all magnetic fields and operating temperatures from 5 Kelvin to 77 Kelvin.
«These results demonstrate that significant performance improvements are still possible and, therefore, the associated cost reduction that can potentially be realized in optimized commercial HTS wires, — says Goyal.
How high efficiency wire was made
The HTS segment of the wire was fabricated on (IBAD) MgO substrates and using nanocolumnar defects using simultaneous phase separation and strain-controlled self-assembly technology. The self-assembly technology allows for embedding in insulating or non-superconducting nanocolumns at nanoscale distances inside the superconductor. These nanodefects can anchor superconducting vortices, creating higher supercurrents.
"The high critical current density became possible due to the combination of pinning effects from rare-earth doping, oxygen point defects, and barium zirconate insulating nanocolumns and their morphology", — says Goyal.
"The HTS film was created using an advanced pulsed laser deposition system by carefully controlling the deposition parameters", — adds Rohit Kumar, PhD student in UB's Heteroepitaxial Growth of Functional Materials and Devices Laboratory, which Goyal leads.
During pulsed laser deposition, a laser beam hits a target material and removes the material, which is deposited as a film on a properly placed substrate .
«We also performed atomic-resolution microscopy using state-of-the-art microscopes at the Canadian Center for Electron Microscopy at McMaster University to characterize nanocolumnar and atomic defects, and performed some measurements of superconductivity properties at the University of Salerno in Italy.» ;, — says Goyal.