The Biggest Jolt to Power Since Franklin Flew His Kite
By BARNABY J. FEDER
April 27, 2004
nytimes.com
CHENECTADY, N.Y. — In a onetime printing plant on the edge of this tattered manufacturing city, a small company named Superpower churns out sample after sample of what looks like shiny metal tape.
The tape has five layers. The middle one, a ceramic film one-tenth as thick as a human hair, exhibits one of nature's most tantalizing tricks. At very low temperatures, the ceramic abruptly loses all resistance to electrical current.
That free-flowing current generates a strong magnetic field, a feature that Superpower technicians demonstrate by showing visitors how a thumbnail-size magnet floats half an inch or so above a ribbon of chilled tape.
Superconductivity, as the phenomenon is known, has fascinated and baffled scientists since its discovery in 1911. Even now, they have yet to develop a comprehensive theory to explain its appearance in materials as diverse as metal and ceramics.
Such scientific conundrums are of only passing interest at Superpower, a four-year-old subsidiary of Intermagnetics General, and at other companies like it. After years of false starts and setbacks, these companies say they are closing in on the goal of producing relatively inexpensive superconducting wire for power generators, transformers and transmission lines.
Success requires making yard after yard of wire, and eventually mile after mile. The focus at the companies, at national laboratories and at many universities is on questions that call for a genius more like Edison than Einstein.
"We are finding out what works and going with that," said Dr. Jodi L. Reeves, a senior materials scientist at Superpower.
Success could spring superconductivity from the modest niches that it has occupied in fields like medical diagnostics and give it wide commercial applications. In addition to cutting costs and raising reliability in generating and distributing electricity, superconductive wire could replace copper wire in motors to save space and cut energy costs in factories and on ships. Railroads might finally embrace maglev technology, which allows high-speed trains to ride magnetic fields above superconductive rails.
The alloys used in medical imaging superconduct only at supercold temperatures, about 450 degrees below zero Fahrenheit. To reach that point, they have to be cooled by liquid helium, which is expensive to make and manage.
By contrast, ceramic superconductors work at temperatures above minus 321 Fahrenheit, allowing them to be cooled by liquid nitrogen, an inexpensive industrial refrigerant. For that reason, they are called high-temperature superconductors, though they are still far from the dream of a room-temperature superconductor.
The first reports of ceramic superconductors, in 1986, touched off a global research race to understand them and find others. The excitement peaked at the annual meeting of the American Physical Society in March 1987, when thousands of researchers crowded into a hastily organized midnight presentation.
That session, later called the Woodstock of physics, ran for hours as research groups from around the world reported their successes, sometimes with data updated to include results just hours old.
For some who were there, it was a life-altering experience. Dr. Gregory J. Yurek, a professor of materials science and engineering at the Massachusetts Institute of Technology, founded a company called American Superconductor in his kitchen in Wellesley, Mass., and resigned his tenured position the next year to work full time on his fledgling business. Experts from Intermagnetics General, a manufacturer of superconducting metals that was spun out of General Electric in 1971, immediately began work on the materials.
"Superconductivity was guaranteed to be a field where everything you did would be new," said Dr. Venkat Selvamanickam, who joined the first wave of research as a graduate student at the University of Houston, home to one of the leading high-temperature superconductivity research groups. He was hired by Intermagnetics in 1996 to lead the development work that it handed off to Superpower.
Although the United States and other countries have poured hundreds of millions of dollars into the area, success has not been quick. Unlike metal superconductors, the ceramic ones are naturally brittle and powdery. There was no simple process to transform them into wire.
Moreover, superconductivity in ceramic tape is easily disrupted by magnetic flux, in which changes in the magnetic field drift through the superconducting layers of the tape like swirling weather systems through the atmosphere. Figuring how to immobilize the magnetic vortices, an atomic-scale process called pinning, has emerged as a crucial area for research.
Early ceramic compounds were based on bismuth. The complexity of manufacturing and the need to rely on silver substrates to provide a workable mix of strength and stability to the bismuth compounds kept costs so much higher than standard copper wires that companies lost confidence that they could compete in mass markets.
Although bismuth-based wires have been useful for research and in a few products that help stabilize power grids, the spotlight has shifted to another compound, a mixture of yttrium, barium, copper and oxide generally called YBCO (pronounced IB-co).
YBCO tape cannot yet match bismuth's performance. But it uses nickel instead of silver as a wire strengthener and "thin film" technology borrowed from the semiconductor and photovoltaic industries to deposit the layers of the tape, which then can be made into wire.
The technology will cut the cost of production up to 80 percent from the first-generation technology, said Dr. Yurek, whose company is the leading producer of the bismuth-based wire.
The last steps will not be easy. While the semiconductor industry works on improving technology to produce ever thinner films, superconductivity companies chase the opposite goal, making thicker films to carry more current.
The best available process for depositing YBCO involves blasting a chunk of it in a vacuum chamber with high-energy laser pulses and running the tape through the resulting plume. But pulsed lasers use too much time and money to produce large quantities of wire. So companies are looking for other methods.
"There's probably a dozen ways to deposit the superconductor," said Dr. Dean Peterson, head of the research program at the Los Alamos National Laboratory, which has been researching the alternatives and how to improve them.
As an added complication, technologies under development are competing to create the substrate under the superconducting ceramic. Although that material is less sexy, research indicates that the uniformity and alignment of the substrate are as crucial to obtaining useful wire as a foundation is to a house.
As they race toward commercialization, the same question that attracted materials scientists to the field lurks in the background. Are better superconductors out there, waiting to be discovered? |
