Superconducting cables are one-tenth the size of copper wires. What’s more, they can handle surge protection within the cable itself without requiring new sets of bulky breakers. Superconducting materials, which are based on a flexible ceramic called yttrium barium copper oxide, can tolerate a certain power load. At every point up to that maximum, they carry current with zero loss. But the moment the maximum is exceeded, the superconductors become highly resistive and stop propagation of surges. “Depending on the number of wires you put in, you can carry more current without losses, and you can design the cable in terms of having the right amount of resistance” in the event of power surges, says Alexis Malozemoff, chief technology officer at American Superconductor.
Of course, if the superconducting cable becomes resistive, it can burn up, so some hardware is needed to prevent such damage. The company says that unspecified associated control systems will handle this problem effectively. “Necessity is the mother of invention,” says Yurek. “You can put [fault protection] in the cable, with some other proprietary technology,” which he says is more space efficient.
However sensible this might be, it won’t be simple. It will take more than a year just to put all the pieces together in laboratories. “You have to design it, then build it, then develop testing protocols, then [do] full prototype tests, then analyze the data, then develop a design specification for installation,” says Kurtz. The hope is that the concept will be proved by August 2008. Actual construction won’t happen before 2010.
High-temperature superconductors were born two decades ago. American Superconductor found a way to commercialize the material by making a flexible version of the ceramic and nudging the temperature requirements up to a more-manageable 90 degrees kelvin. That temperature can be reliably maintained using liquid nitrogen for cooling.
While superconducting cables–including some transmission lines in Columbus, OH, Albany, NY, and Long Island–are slowly making headway, the Manhattan project marks a new milestone, says Yurek. “Con Ed is deciding they are willing to put these superconductors in their grid. It’s a heck of a validation point, to say the least.”