IPF 2011: Plugging into the grid

For now, room-temperature superconducting wires remain a pipe dream, but superconducting power cables based on cuprate materials are actually starting to work their way into power grids.

Alexis Malozemoff from the company American Superconductor (AMSC) started off his talk at the 2011 Industrial Physics Forum in Dallas, Texas, by describing his company’s development of superconducting wires—and its first major commercial order. LS Cable of South Korea bought about three million meters of AMSC’s wires to turn into more than ten kilometers of power cables. Some of the cables will be used to bring power directly into South Korea’s capital Seoul.

“This major commercial order we see as tremendously important,” Malozemoff said. "[This] order signals the transition from demonstration to commercialization.”

The wires that LS Cable bought are really more like ribbons, about four millimeters wide and about a fifth of a millimeter thick. Each one is made of about eight layers of different materials, but only the thin middle YBCO (yttrium barium copper oxide) layer actually carries the current of more than 3 megamp/cm².

To turn them into functioning power cables, the thin ribbons are wound helically in one direction around a copper core and then another layer is wound in the opposite direction to balance out the axial magnetic fields. The wound-up ribbons are then clad in layers of dielectric. When they’re operating, the ribbons are bathed in liquid nitrogen to keep them below their superconducting transition temperature.

“Superconductor cable is more expensive than a conventional cable per length,” Malozemoff said. But, he added, a superconducting power network would save money when viewed as an overall system. Because traditional cables are so bulky, installing them in dense inner cities or even remote rural areas is more expensive than would be the case for low-profile superconducting cables.

“It’s essential to look at these costs as a system,” Malozemoff said. “There’s literally no easier way to get power into a big city like New York City.”

Mike Lucibella