Superconductors promise friendlier power delivery

Superconductor and copper wire - capable of carrying the same amount of power.

Small-scale power transmission projects around the world using highly efficient superconductors are showing promise and could have applications in this country.

A conference this week will hear how demonstration power projects in the United States, Europe and Japan could point the way forward on power transmission. While long-distance projects have yet to be built, one expert says costs now running at twice those of conventional overhead lines are coming down constantly.

Industrial Research is running the three-day gathering at Te Papa which will highlight greater applications for superconductors with zero resistance for electricity that can function in much warmer situations than the older technology.

High temperature superconducting (HTS) allows cables or associated equipment to be cooled to -196C using "off the shelf" cryogenic technology instead of -273C which is far more expensive and needs cumbersome specialist equipment.

Among the participants is the American Superconductor Corp, which has installed high temperature superconductor cables in Ohio in the New York area.

While the longest stretch is less than 1km and its most immediate future is in densely populated areas, the company says the same technology is capable of being applied over hundreds of kilometres.

Spokesman Jason Fredette said there were now plans to use superconductor cables to join up all three major United States power grids.

Two superconductor cables within a buried pipe less than 1m in diameter had the capacity to carry enough power for 1.5 million homes. Conventional overhead high-voltage direct current lines lost between 7 per cent and 10 per cent of their load over long distances whereas superconductor cables lost just 2.5 per cent, at points where power was stepped down to alternating current, he said.

Superconductor cables were "smart" in that they were capable of managing power surges. The 23-year-old company was now selling the system in Korea, he said.

Some opponents of Transpower's massive North Island pylon project have criticised the SOE for rejecting too early the potential benefits of underground superconductor cables. Transpower said the use of high temperature conductor was considered an option on the North Island Grid Upgrade project but it was found to be expensive to buy and install, had high transmission losses and was relatively untested.

Industrial Research chief executive Shaun Coffey said New Zealand's electricity sector might benefit more from applying high temperature superconducting to small-scale generation, rather than using it to transmit power over long distances.

Because it could replace heavy and bulky copper cabling in generators, he said, it could be used in compact, lightweight wind turbines on buildings, for example.

While upfront costs were higher, operating costs over what would be a longer lifespan of equipment were lower.

SUPER SCIENCE

* Superconductivity allows electrical current to be carried with no resistance and extremely low losses.

* Power cables made up of yttrium, barium, copper and oxide woven into a coaxial configuration are far less bulky than copper cable and capable of carrying much more power.

* Proponents say it creates no electromagnetic field emissions, no soil heating, and oil isn't used so there are fewer environmental impacts.