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Those achievements have required huge investment in engineering research and development – and some of the resulting technologies have applications far beyond particle physics.
The Rebco (Rare-Earth Barium Copper Oxide) cable is one such technology. It was originally designed to transmit extremely high power to particle accelerators such as the Large Hadron Collider. Now, Cern and Airbus subsidiary UpNext are exploring its use in the electrical distribution systems of future hydrogen-powered aircraft as part of the Scale (SuperConductors for Aviation with Low Emissions) demonstrator.
‘High-temperature’ superconductivity
At extremely low temperatures, some materials have no electrical resistance and therefore no power loss. At Cern, superconducting cables maximise efficiency and minimise energy use as powerful magnets guide particles towards each other.
“Our magnets rely on cables which are able to transfer very high currents in a very small cross-section,” said Amalia Ballarino, deputy group leader of Cern’s magnet and superconductor group. “If you think about 12,000A, these are levels of current that you do not find in everyday applications using conventional materials… overhead lines typically do not transfer more than 2,000-3,000A.”
She added: “The only way to generate these fields in a compact configuration and also then to run the machine with reasonable cost is to have a superconductor.”
Produced by starting from a substrate and depositing extremely thin layers of ceramic material, Rebco is a ‘high-temperature’ superconductor at 77K, or -196ºC – not warm by any stretch of the imagination, but a much higher temperature than the 4.2K of low-temperature superconductors, made possible by liquid helium cooling.
Typically manufactured in 100m lengths with a width of 4mm and thickness of 0.1mm, Rebco tapes can transfer about 200A when cooled in liquid nitrogen. Several tapes are combined into a cable, connected in parallel, to transfer very high currents.
Power loss is “practically zero,” said Ballarino, although there are losses from transitions and when operating in AC.
These characteristics mean the cables could significantly reduce the weight of electrical distribution systems in electric or hybrid-electric powertrains, which could in turn enable fuel reductions or longer range for hydrogen aircraft.
Cern is working with UpNext to explore different configurations. Take-off and approach require instantaneous power, for example, while long-range cruising needs a different set-up. If the aircraft uses liquid hydrogen fuel, that itself could provide the onboard cryogenic system to cool the cables to superconducting temperatures.
Cost pressure
The advanced technology is likely to be expensive at first, but the team at Cern is confident that the advantages will more than justify the cost. As aviation faces up to the scale of the net-zero challenge, something that enables sustainable flight could get huge industry backing.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.