Superconductors in the round
Compact but powerful
Grid upgrades in urban areas requires cables that can fit into existing pipes. Although High Temperature Superconducting (HTS) cables are smaller than conventional ones, we patented a new way to produce a smaller round wire, making the cable core 2 to 3 times more compact than their predecessors.
An inside job
Since ceramic HTS tapes which transmit power are difficult to bend, they are usually stranded around a hollow tube or cable core that is lost for conduction. Our solution distributes round superconducting wires inside the core, which increases the superconducting section (and current density) while reducing diameter.
Shaping a tape like a tiny cylinder and laser-bonding it to a central core is tricky, since tensile stress can crack the ceramic surface layer. To resolve this, we borrowed micro-tube technology from Hanover (for making medical needles). Then we patented the “neutral axis” wire design and associated processes to accurately place the fragile HTS ceramic layer on the neutral axis of the tape where there is minimal tension during bending. NRC Lens developed a special, fast electrolytic deposition line, and Hanover improved shaping tools to gently bend tapes.
Round Wire (RW) cables will be easier to manufacture than previous versions with superconducting tapes. Classical multistage cabling machines could produce the cores (containing 40-60 strands) in a single run. These cables are compliant with environmental requirements for urban and protected areas. The small diameters make it easier to retrofit HTS cable in existing rights-of-way, while a smaller cryogenic envelope reduces thermal losses. This groundbreaking patent and improved process will accelerate superconductor deployment in dense urban grids.
“By reducing the footprint of superconductors, this patent will accelerate their use in grids.”