August 7, 2009

Resistance is useless...

Superconductivity is the phenomenon whereby a material can conduct an electric current with no resistance. For some of you that might seem rather dull, but the implications of this are actually fairly significant. Because they can conduct an electric current with no resistance, there is no heat loss as a result. This, coupled with the fact they can transmit high current loads, makes them ideal as power transmission cables, replacing those that are currently quite inefficient over long distances.

Superconductors can also be used to create powerful magnets for better MRI instruments, magnetically levitated trains (like the Maglev train in Shanghai, China that can reach speeds of up to 430 km/h), and particle accelerators (like the LHC in Switzerland) that allow physicists to conduct ground breaking fundamental research about the world we live in.

As a result, superconductors have been "the next big thing" for a fair few many years now, but their application has been hamstrung by the fact they require bulky, complicated, and expensive cooling systems to get the superconducting effect - they only work below about -135 C and so need to be cooled by liquid nitrogen (-197 C). The obvious goal is to get them to work at ambient temperatures of around 0-30 C, but for this to happen, scientists still need to understand the fundamentals of these materials.

For a long time, scientists only thought there was one family of superconducting materials, which made it difficult for them to understand their fundamentals. Recently a Japanese group has discovered (by accident) a new family. Although operating at only -217 C, well below the current benchmark of -135 C, it is nonetheless exciting because now with two families to compare and contrast hopefully scientists can finally solve this problem and we might see some of these incredible applications become more widespread.

Endeavour Capital, who I work for, is an investor in HTS-110, a spin out company from fundamental research conducted at Industrial Research Limited (IRL) in Lower Hutt, New Zealand. Researchers at IRL were one of the first groups in the world to develop a process for the production of superconducting wire from 1st and 2nd generation superconducting materials. As a result, they formed a partnership with American Superconductors Inc., one of the biggest companies in the world active in this area. HTS-110 use this wire to produce superconducting magnets. This is yet another example of how kiwi ingenuity can be a world beater - in some areas that probably not too many kiwi's suspect either.

I think their story, coupled with the exciting new discovery by the Japanese group, illustrates the vital role of fundamental research in the progression of any ground breaking new technology towards commercialisation.


  1. Aaron - we looked at the superconductor market a few years ago. In the fault current limiters application, the most recent generation of materials that are able to operate at higher temperatures, such as YBCO (YBa2Cu3O7), require the use of a metallic shunt top layer to give a degree of thermal and electrical protection should a fault in the superconducting tape develop. This metallic layer is typically 50-100nm thick and must be resistant to oxidation at the high temperatures which can arise during both processing steps and in service during current overload situation. It must also serve as a barrier to prevent ingress of moisture into the YBCO superconductor. Sputtered silver, gold and silver-gold alloy layers have so far shown the best combination of properties for this applications including electrical and thermal conductivities, contact resistance, specific heat capacities, oxidation potential, lattice constant, and coefficient of linear expansion

  2. To the extent that NZ has been involved in the production of HTS wires this has come from IRL not HTS-110. DSIR/IRL held key patents on BSCCO (material used in 1st generation wire)and IRL has had an on going contract with American Superconductors (one of the producers of HTS wire) to help improve the quality of YBCO based wire (2nd generation).

    HTS-110's contribution has been in using the wire to make magnets.

    The real issue around dveloping wire for fault current limitiers (at least of the resistive type) is to incorporate bulk metal conductors (not at the nm scale) to act as a resistive and thermal sink when the superconductor ceases to conduct (superconductors work well for dealing with fault currents because they cease to conduct at sub cycle seeds if the current goes beyond a critical current).

  3. Thanks for your comments and for clearing that up Simon.



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