Superconductors are Key to Efficient Power Lines

Remember the Woodstock of physics? Probably not. Back in the spring of 1987, though, headlines were trumpeting it as the most exciting scientific meeting in history. Three thousand physicists crammed into a ballroom at the New York Hilton to talk about superconductivity—the transmission of electricity with literally zero resistance. The technology was suddenly within reach of being economical. So it appeared, anyway, and that could mean anything from superfast computers to tiny, powerful electric motors to power lines that could carry current with no loss of energy.

In the more than two decades since, superconductors haven't grabbed many headlines. That's partly because the new materials discovered in the late '80s proved to be a lot harder to work with than anyone expected, and partly because their energy-saving wizardry wasn't in high demand during most of the 1990s. But nowadays, using less energy is a key strategy in the fight against climate change—and a lot of the technical problems that have dogged superconductor technology have been solved. "Five years ago, I'd have been skeptical," says Robert Cava, a Princeton materials scientist who was in on the original Woodstock of Physics. "But after years and years and years of people beating their heads against the wall, they've finally got it."

"They" are scientists and engineers at a handful of companies in Europe, the U.S. and Japan who have figured out how to turn brittle, fragile superconductors into flexible wires. "We basically found a way to bend the unbendable," says Greg Yurek, who left the MIT faculty in the late 1980s to found American Superconductor in Massachusetts. Superconductors have found their way recently into ships, wind turbines and electric cars.

But the big push now is for power transmission. A major element of the "smart grid" is a new set of long-distance power lines to carry electricity from renewables like wind and solar. Conventional power lines are expensive, unsightly and wasteful—they can lose 14 percent of their energy from the resistance of the cables.

Superconducting cables have no such problem. A set of cables carrying five gigawatts of power—the output, of, say, five big nuclear-power plants—can fit into a pipe just one meter across, and you could even bury it underground. Part of the pipe will be taken up with a cooling system: these superconductors work only when kept at the temperature of liquid nitrogen, about minus 170 degrees Celsius. Nitrogen is relatively cheap to manufacture and keep cold compared with the liquid helium (minus 269 degrees) needed for old-fashioned superconductors. The cooling equipment draws some energy from the cable, but still far less than the losses in today's cable.

Even so, the power industry isn't likely to trash its old but serviceable transmission lines and install superconductors, even if they are more efficient. If the world is going to start using climate-friendly renewables, it'll require new transmission lines anyway. In the U.S., for example, the most abundant and reliable wind power comes from a belt stretching from Texas north to the Dakotas. The best spots for solar are in Arizona and New Mexico. The biggest consumers of electricity—the cities—are mostly along the coasts and near the Great Lakes.

So new power cables will have to link the source to the consumer. And if it's a choice between ugly, inefficient overhead lines and a pipe buried along existing interstate-highway rights of way, the choice seems kind of obvious—assuming that American Superconductor is correct in its claim that the costs are roughly the same. The Woodstock of Physics, in short, may finally be living up to its mostly forgotten hype.

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