After generating huge excitement more than a decade ago, high-temperature superconductivity nearly disappeared from public view. Now, a breakthrough has spawned large-scale production of cost-effective superconducting wire capable of transmitting 130 times the electricity delivered by a normal copper wire.
This breakthrough has major cost-saving implications. It could lower electric bills for consumers, reduce the need for new power plants, cut greenhouse gas emissions, and increase the efficiency of large electric motors by as much as 50 percent.
"We hope the product will help boost industrial applications of superconducting wire and other products," says Yutaka Saeki, a spokesman for Sumitomo Electric Industries, which has successfully produced 3,000-foot sections of high-temperature ceramic superconducting wire. The wire, produced in Osaka, Japan, is narrower than the width of a pencil.
To develop the market, Sumitomo - Japan's biggest electric cablemaker - will offer the cable at competitive prices - about two to five times the price of conventional copper, Mr. Saeki says.
But Sumitomo will soon have competition. American Superconductor Corp. of Westborough, Mass., is working with the Oak Ridge National Laboratory [NIST] on a more advanced version of the wire, which could be used as transmission lines for electric utilities.
Mohawk Power Corp. in Syracuse, N.Y., will be the world's first utility to use Sumitomo's superconducting wire. Mohawk plans to use it in motors and transformers for ships and trains. Crafts using the new wire will weigh less than those that rely on low-temperature superconductors, reducing energy consumption.
Those gains come from the inherent efficiency of superconductors. In conventional conductors, such as copper wire, atoms impede the free flow of electrons, converting electrical energy into waste heat. Today, about 6 to 7 percent of the electricity generated in the United States is lost before ever getting to consumers, according to the US Energy Information Agency.
Superconductors, by contrast, have no such electrical resistance, so they carry current with no electrical energy loss. They come in two types. Low-temperature superconductors work at only very frigid temperatures: below -452 degrees F. They're expensive to operate because they need to be chilled with liquid helium.
High-temperature superconductors, however, work at relatively warmer temperatures (between -452 and -320 degrees) and require less expensive liquid nitrogen to run. The next step is to expand the uses of the technology.
For example, superconducting wire can stretch almost twice as much as previously thought - without any cracking of its coating and almost no loss in the coating's ability to carry electricity, according to Najib Cheggour and his research team at the National Institute of Standards and Technology. As a result, superconductor power cables employing this wire could be used as transmission lines. The liquid deposition coating process is designed to be suitable for high-volume, low-cost wire manufacturing.
American Superconductor expects to commercialize this technology in the next three to four years. It has already been successfully used in a new prototype electromagnet that floats Japan's newest magnetically levitated train about four inches above the track.
Once the technology gets commercialized, it could be used in many applications, including:
• City centers, where there is enormous demand but little space for additional copper cables under streets.
• Strategic points on the electric power grid, where compact underground superconductor cables would expand capacity and direct power flows.
• Machinery as well as motors and transformers for trains and ships.
• Extremely fast computers, which would avoid the heat-management problems in today's electronic circuits.
Even with high-temperature superconducting materials available, challenges remain. High-temperature superconducting materials are brittle. This causes difficulties in the manufacture and the use of superconducting wire cables. These cables need sufficient strength and resiliency to withstand the stretching and bending that occur during power-cable fabrication and installation.
The search continues for improved high-temperature superconducting materials. Discovering cost-effective materials that are superconducting at room temperature would be revolutionary. So despite the commercialization of high-temperature superconducting wire, much research remains to be done.