Magnetic Trains, Cheap Power Brought to You by Superwires?

Yancey Hall
for National Geographic News

April 3, 2006

It's the future that was supposed to happen a decade ago: high-speed
levitating trains, ultrafast computers in every office, and plenty of
cheap, clean electricity, all courtesy of superconductors.

Hailed as the breakthrough replacement for copper wiring, superconductors can transport electrical current with near-perfect efficiency.

But superconducting materials have presented several technical hurdles that have kept futuristic products from reaching the public.

One of the biggest problems is that the materials are often used in conjunction with powerful magnets, and the magnetic fields can act like brakes against free-flowing electrons.

Now researchers at the U.S. Department of Energy's Oak Ridge National Laboratory (ORNL) have found a way to stop the intrusion of magnetic fields—placing a unique configuration of nanoscale dots inside the wires.

"Since most applications [for superconductors] involve high magnetic fields, we had to look for a way to sustain the superconductive flow of electric current," said ORNL's Amit Goyal, the project leader.

This latest advance means that superconducting wires can performe well enough for use in many large-scale applications.

Nanodots

Scientists have already found one possible way to overcome the other main hurdle of bringing superconductors to market: keeping the wires cool.

Conventional superconductors work at subzero temperatures—too low to be maintained economically.

Scientists are therefore pinning their hopes on high-temperature superconductors (HTS), and ceramics seem to be today's best candidates.

Ceramics are normally insulators, but they are able to superconduct at higher temperatures than most other substances—around -200°C (-328°F), or about the same temperature as liquid nitrogen.

Because liquid nitrogen is a relatively cheap coolant, HTS wires are the best bet for making hover trains and ultra-efficient power grids a reality.

But ceramic HTS wires suffer the same problem of magnetic interference as other superconductors.

Goyal and his team, who report their findings in the current issue of the journal Science, found their solution to this quandary using nanotechnology.

The scientists coated the interior lining of HTS wire with columns of nanodots—nanoscale "defects" created by a laser.

The pockmarked wires were found to be highly effective in sustaining a superconductive flow of electric current.

"The nanodots localize the magnetic flux in nonsuperconducting regions [of the wire]," Goyal said. The dots essentially act like tiny wells that trap magnetic fields.

But it's not just the dots themselves that prevent magnetic interference. It's also the way they are positioned on the lining of the wire.

Maglev Train

Greg Yurek, chairman and chief executive officer of private firm American Superconductor, is often one of the first people to create industrial potential for HTS developments at government labs like ORNL.

In 1995 his company worked with Los Alamos National Laboratory in New Mexico on a technique to coat wires with superconducting material.

Eleven years later that technology is making its way into commercial and industrial applications.

"It's finally coming to fruition," Yurek said. "I remember in 1988 a reporter called me up and said, Where are the magnetically levitated trains?"

His answer could have been, In Japan but about 20 years from now.

In the fall of 2005 an experimental magnetic-levitated train, developed by Central Japan Railway, ran down a track in Japan at more than 310 miles an hour (500 kilometers an hour).

American Superconductor's HTS wires were used in one of the superconductive electromagnets that provided the lift necessary make the entire train hover four inches (ten centimeters) above the concrete guideway.

But it's not just futuristic trains that would rely upon these superwires. Power grids can be revamped with the technology so larger amounts of electricity can be provided to energy-hungry cities.

"In December of 2006 we will be installing our first commercial superconductor product into a power grid," Yurek said.

Because HTS wires can carry more current at a smaller size than other wires, "a superconductive power cable can carry a lot more power through the duct work under the streets of cities and relieve grid congestion."

One of the keys to making the HTS wires viable in the marketplace is keeping manufacturing costs low.

"By the end of the decade, the price performance ratio will be roughly equivalent to copper [wires]," Yurek predicts.

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