Aiming to develop the ultimate power cables using new high-temperature superconductors

The Kamihara Laboratory is working to discover new high-temperature superconductors, and use them to make superconducting cables. The ordinary metals currently used for cables, such as copper and aluminum, undergo Joule heating when a current flows. This wastes electric power, and reduces the power that can be used.

Q.”If you generate 10 units of power, you can’t carry 10 units via power cables to the user. But if you use superconductors, Joule heating doesn’t occur. Those materials have absolutely no resistivity. In that case, if 10 units are generated, the user gets 10 units. The user’s device might be a PC, or many other things. Anyway, superconducting power cables enable us to use the total power of electricity generation. It is an extremely good power cable.”

Today’s high-Tc superconductors, such as layered copper oxides and iron-based oxypnictides, are ceramic, and fragile. Therefore, it’s an important issue to develop a technology to make a power cable using the oxides.

Q.”Most high-Tc materials are fragile. They’re ceramics. We have to cover those ceramics with malleable “sheath metal”, to make it fairly easy to process bending, rolling, and stretch. If superconductors are covered with the sheath metal, they finally become usable as cables. But when these superconductors are covered with metal, a problem arises. The superconductors react with metals, producing undesirable impurity phase. In our research, we aim to reduce amount of the impurity phase. I think it is a good way of cable-making research on iron-based superconductors.”

Also, at present, the highest Tc is 138 Kelvin of copper-based superconductors. Even at this temperature, the material is called a “high-temperature” superconductor. But this is too low for materials to be used in power cables at room temperature, which is 300 Kelvin.
In 2008, Dr. Kamihara and his bosses have discovered that a group of materials which include iron square lattices are suitable for use as superconductors.

Q.”There are many elements and compounds which demonstrate superconductivity. For example, there are silicon which is a typical semi-conductor, diamond which is made from carbon, and some species of cements which are construction materials. If you change its chemical composition slightly, or press it in high pressure, they become superconductors at low temperatures.”
　
If you obtain room-temperature superconductors using a variety of elements, it’ll be possible to generate and use electricity without wastage.

Q.”I think that if room-temperature superconductors are achieved, they’ll change everything related to power transmission. But the hurdles, which will replace all normal conducting power cables into undiscovered superconducting one, are still too high. So we do research for application of the superconductors which have been obtained. If our research produces results, we could use them, for example, to generate high magnetic fields for Maglev transport, or for MRI. We hope our research contribute to utilize superconductors in efficient power transportation and producing high magnetic field.”