Stuart Wimbush: From materials to systems
Story by Ruth Beran Commercialising high temperature superconductors is what the 25 scientists and engineers at the Robinson Research Institute (RRI) do best. Formerly part of IRL, and called the Superconductivity and Energy Team, the RRI is now part of Victoria University of Wellington. The Robinson Research Institute was named after the late Dr Bill Robinson who developed the seismic base isolators found in buildings like Te Papa. Robinson was the director of the Physics and Engineering Laboratory (PEL) at the Department of Scientific and Industrial Research (DSIR) from 1985 to 1991 and supported early research into high temperature superconductors. This research paid off, leading to the discovery of what would become the first commercial high temperature superconductor (HTS) material, Bi2Sr2Ca2Cu3O10. Patenting this discovery and licensing that patent enabled the development of a long-lasting research relationship with the pioneering superconducting wire manufacturer American Superconductor, helping them to successfully commercialise the product. It also spurred the development in New Zealand of a new industry sector, embodied in the companies HTS-110 and GCS, building superconducting components, devices and systems. A superconductor is a material that allows electricity to flow without resistance or loss of energy. There is a catch though. Superconductors only work when they are very, very cold. For example, low-temperature superconductors used in the magnets of hospital MRIs (magnetic resonance imaging) or NMR (nuclear magnetic resonance) require liquid helium to keep them at temperatures below –250°C. High temperature superconductors (HTS) still need low temperatures, but not nearly as cold. So for example, they operate at temperatures of –196°C or so, which can be achieved using liquid nitrogen or even electrical refrigeration systems which don’t need a cryogen like liquid nitrogen at all. This means high temperature superconductors can be used more broadly in applications like electric power systems, transmission cables, as well as in magnets. “Superconductors really have to be viewed as the enabling technology for a sustainable energy future, which is what we’re all heading towards,” says MacDiarmid Institute Associate Investigator Stuart Wimbush, RRI senior scientist. “There’s just no way that we can avoid utilising this technology we have. It just needs a little development and things are definitely heading that way.” So at RRI, senior scientist Mike Staines has been using HTS technology to develop a power transformer that drastically reduces energy loss compared to conventional transformers. “A transformer takes an electrical voltage and changes the voltage,” says Wimbush. “You’ll know about that from your house, like your laptop power brick, that’s a transformer. But they are required at every scale and we apply them actually in the grid.” The transformer developed at RRI uses superconducting wire instead of copper wire, allowing it to carry a far higher current density, making it smaller and lighter. Instead of oil, the transformer uses liquid nitrogen for cooling and insulation, eliminating fire and environmental hazards. At present this liquid nitrogen needs to be topped up, but in the field, electrical coolers will be used in a sealed system so liquid nitrogen does not boil off. “That transformer, because it’s made of superconductor has been able to carry the highest current of any transformer that’s ever been reported,” says Wimbush. In recent tests, the transformer successfully handled a top current capacity of 1390 amps. Another project being worked on at RRI is a cryogen-free MRI machine. It also uses high temperature superconductors, so instead of needing a cryostat of liquid helium to cool the magnet, the small experimental version that has been developed uses an electrical refrigeration unit, or cryocooler. Like most electronic devices this means the MRI cannot operate if there is a power failure, but it also means the machine can be switched on and off, unlike a hospital MRI which is always on. It can also be easily moved. This means that eventually, if funding is found to develop a larger MRI, it could be put into a shipping container and made transportable for applications like military field hospitals. “That would be quite a unique product or system for an MRI machine, to be able to be transported around to different areas, particularly remote regions” says Wimbush. The RRI has a focus on materials science and commercialising that science, and for this reason Wimbush sees a close fit with the MacDiarmid Institute. The RRI also has a large contingent of Principal and Associate Investigators. Jeff Tallon (PI) is focused on the fundamental science of HTS, Bob Buckley (AI) is the Director of the RRI, Shen Chong (AI) is investigating new materials, and Chris Bumby (AI) works on a range of applied projects, including the development of a superconducting flux pump used to energise superconducting coils efficiently. Ruth Knibbe (AI) runs the scanning electron microscope facility, and Simon Granville (AI) works on magnetic materials. A new MacDiarmid Institute postdoctoral fellow, Guy Dubuis, will join the team shortly to work on investigating the superconducting state because even though superconductivity brings quantum mechanics to the everyday scale, exactly how high temperature superconductors work at the quantum level is poorly understood. While Wimbush would like to see more Principal Investigators at RRI, he thinks the large number of Associate Investigators is a reflection of the strong materials-based science being conducted at RRI. “I think we attract materials scientists and we have challenging topics to work on and as a result we have a lot of relevance to the MacDiarmid Institute and its goals and I think that’s reflected in the number of people that we have here,” says Wimbush.