from: http://www.engadget.com/2011/09/09/superconducting-sapphire-wires-are-as-cool-as-they-sound/:

The copper wire is relatively cheap, malleable and can conduct electricity, but it is far from ideal. Feed the cities requires meters wide and cables, the metal loses a lot of energy as heat. Fortunately, a team of Tel Aviv University think it solved the problem. Take a sapphire fiber Oakridge National Laboratory in Tennessee, he developed a superconducting wire barely thicker than a human hair, which makes 40 times the electricity of his brothers copper. Cooled with liquid nitrogen, superconductors carry current without sapphire heat, which is the key to their effectiveness. The team working on practical applications of the technology – because it is so small and flexible (unlike previous superconductors), it could replace the copper in the home and its cold performance makes it perfect to transmit power to long distances from the stations to green power. The wire goes around the world as we speak and will arise at the conference in Baltimore in October ATSC. Anyone who makes jokes about son and Baltimore will be asked to leave politely.