Image source: Nikkei Asia

Japan takes superconducting power transmission leap

Japan, Tokyo: A Japan Railway-affiliated research institute has laid a 1.5 km superconducting transmission line — the world’s longest practical-use cable.

The cables have been laid at a facility in Miyazaki Prefecture, where it is holding demonstration tests.

The production of the line was outsourced to Mitsui Mining & Smelting, and several railroad companies are showing interest in adopting the technology, the institute said.

Transmission loss is mainly caused when electricity turns into heat due to the electrical resistance of electric wires. When a transmission line is cooled to minus 269 °C with liquid helium and put into a superconducting state, however, the electrical resistance becomes zero, and power loss can be all but eliminated.

The technology’s cost had been a major hurdle to its spread. But thanks to the development of materials that can be superconducting at minus 196 °C, liquid nitrogen can be used as a coolant, which is 10 % cheaper than the standard liquid helium.

The Railway Technical Research Institute, based in Tokyo, has taken this less expensive coolant, innovated with it and discovered a way to coat transmission lines with it.

The test cable can carry the railway-required 1,500 V and several hundred amperes.

Although cooling adds costs to normal power transmission, “if we can make the distance of one power line more than 1 km, we can reduce the cost by utilizing existing power transmission facilities, and the advantage of eliminating power transmission losses outweighs the additional cooling cost,” the Railway Technical Research Institute says. Several railway companies are interested in adopting this technology.

Source: Nikkei Asia