Transmitting nickel’s benefits

Superconductors wrapped in nickel alloy could some day cut electrical line losses in half, making transmission more efficient.

Scientists at the U.S. Department of Energy’s Los Alamos National Laboratory in New Mexico have invented an experimental superconducting tape capable of transmitting electricity over long distances with little loss of power. The tape’s success, which so far is only technical, rests largely on paper-thin strips of nickel alloy, which are used because of its high resistance to heat, though, ironically, the superconductor operates at the ultra-low temperature of liquid nitrogen.

The superconducting material (a compound of yttrium, barium, and copper oxide) is bonded to strips of nickel alloy. The strips, which are only a few microns thick, can withstand bonding temperatures of 700-850C without oxidizing. Brian Newnam, deputy leader of Los Alamos’s Superconductivity Centre, says the tape has been produced using two nickel alloys: N102242, which consists of 65% nickel, 25% molybdenum and 22% chromium, commonly used in gas turbine seal rings; and N06625, which is 60% nickel and 22% chromium and was developed to withstand the extreme heat of jet engines.

The alloys are strong, do not stretch a lot, can be polished to receive the coating, and are non-magnetic — all properties that are essential for producing the tape.

Newnam says the alloys should cost 5-10 times less to produce than the silver alloy used to build the first generation of bismuth-based superconducting tape. The earlier superconductor operated at the temperature of liquid helium (about minus 269C), whereas the nickel-based tape is most efficient at the relatively high temperature of liquid nitrogen (about minus 196C). Liquid nitrogen is relatively inexpensive, and less insulation will be needed to build superconducting transmission lines, offering further cost advantages.

In March 2001, the Los Alamos lab signed a US$2.5-million agreement with Intermagnetics of Latham, N.Y., to develop processes to manufacture many kilometres of tape. Newnam predicts that within 3-5 years, the tape will be used in transmission cables, transformers and electric motors. “It should be a huge market [for nickel] when the coated superconductor becomes commercially available,” he says. “They’re going to turn out thousands of kilometres a year to satisfy the need for transmission cables.”

Power lines employing superconducting technology would be welcome news to Californians weary of power blackouts. Conventional transmission cables lose about 7% of their load, but superconductors can reduce the loss by 50% or more, saving energy and, at the same time, helping protect the environment. Notes Newnam: “This means less energy is required from the producer — burners of coal, oil and natural gas — and that means fewer pollutants.”

Newnam has a wish-list for nickel producers interested in cashing in on the potential market for supeconducting tape. “We are depending on the nickel alloy producers to make reels of kilometre-length tape that is very thin,” he says, adding that the thinness enables the tape to be wound without sacrificing current flow.

He says the lab welcomes a chance to work with nickel alloy producers to devise alloys with fewer impurities, as these impurities can diffuse into the superconducting coating and ruin it.

“The corrosion resistance needs to be available for a short time,” Newnam explains.

— The preceding is an excerpt from Nickel, a publication of the Toronto-based Nickel Development Institute.