Little big wire: High‐temperature superconductivity makes a bid for the power grid

Abstract

I n 1986, scientists discovered a new family of materials that can conduct electricity with absolutely no resistance. Because these socalled superconductors work at much higher temperatures than any previously identified superconductors, the discovery was considered one of the Four wire strips most important of made of the highthat decade. The temperature findings triggered a superconductor wave of euphoria BSCCO (forethat flooded scienground) can carry tific meetings and as much current the popular press. as a copper cable At an American about 100 times Physical Society larger in crossmeeting in New York sectional area. City that convened just months after the discovery hit the news, thousands of researchers overflowed a huge hall. An allnight session was filled with presentations about the phenomenon of high-temperature superconductivity and speculations about its impact. That event became known as the Woodstock of physics. Because the materials potentially could carry huge currents resistance-free and because cooling them to their effective temperature is far less onerous a task than it is for their lower-temperature cousins, many scientists turned visionary and predicted a technological revolution. We physicists were the darlings of the media for a recalls Paul M. Grant of the Electric Power Research Institute (EPRI) in Palo Alto, Calif. At the time, he led the research group at IBM's Almaden Research Center in San Jose, Calif., that determined the atomic structure of one of the materials. someone shoves a mike in your face ... you can say some things that, in retrospect, are pretty silly, he says. To be sure, the revolution has yet to materialize, mainly because the new substances-complex and brittle ceramicsproved to be tougher to tame than the early pundits suspected. But the dream didn't die. Recently, researchers and designers have started demonstrating full-scale prototypes of electric power cables, motors, transformers, and other equipment made of high-temperature superconducting (HTS) wire. The new devices waste less energy than their conventional counterparts. The energy requirement is less even when taking into account the power to cool them to -196?C-or often lower temperatures when strong magnetic fields are present. Moreover, the new superconducting equipment is smaller, lighter, safer, and often more environmentally friendly than conventional devices. We're offering a way to make [motors and other electrical equipment] as perfect as they're ever going to get, says James Daley, manager of the Department of Energy's (DOE) superconductivity program, which is based in Washington, D.C. In Detroit next year, if all goes well on one of the projects sponsored by Daley's office, power will flow through HTS cables to commercial customers for the first time. The main component of the HTS devices now beginning to prove themselves is wire made with compounds of bismuth, strontium, calcium, copper, and oxygen. These matericals are generically known as BSCCO (pronounced bisco). However, the high cost of using BSCCO looms as a serious obstacle to its wide use. That cost may come down through highvolume production of the wire and improvements in its performance. Still, even BSCCO manufacturers are looking for less expensive alternatives to the material. In labs throughout the world, researchers are racing to develop wire from another high-temperature superconductor called yttrium barium copper oxide, or YBCO (pronounced ibco). YBCO wires may cost less than BSCCO ones. They're also expected to carry higher currents than BSCCO wires in the presence of the magnetic fields found in many types of equipment. If YBCO wire can be made in practical lengths-a challenge that arose as soon as YBCO was discovered in 1987-high-temperature suDerconductivU ity may finally offer both cost low enough and performance high enough to become a Workers assemble the first 1,000-horsepower hightemperature superconducting motor at a Rockwell Automation plant in Cleveland.