Wednesday, September 20, 2006

Revolutionary Superconducting Power Transmission Cable

A second generation superconducting power transmission cable, using liquid nitrogen as the coolant, has been energised at a station outside Columbus, Ohio. The Triax HTS cable utilises 3 concentric super-conducting layers to allow 3-phase current transmission in a single cable!

-A new technology that holds promise to transform the global transmission and distribution of electric power was formally energized today near Columbus, Ohio. The $9 million project uses a second-generation High Temperature Superconducting (HTS) cable system to efficiently deliver electric power to approximately 8,600 homes and businesses in suburban Columbus.

The Columbus project is the first demonstration of the new Triax HTS cable design, which dramatically reduces the cost of superconducting systems and brings the technology one step closer to commercial viability. The system was developed by Southwire Company and its partners, American Electric Power (NYSE: AEP), Praxair (NYSE: PX), American Superconductor (NASDAQ: AMSC) and the U.S. Department of Energy's Oak Ridge National Laboratory (ORNL).

Approximately 200 meters (660 feet) of Triax HTS cable from Southwire are part of the system distributing electric power to residential, commercial and industrial customers through AEP's Bixby substation in Groveport, Ohio. The installation phase of the two-year demonstration project came in on time and on budget.

Superconducting cables, operating at extremely low temperatures, eliminate virtually all resistance to the flow of electric current. HTS cables can deliver up to five times more electricity than traditional conventional copper or aluminum cables and have the potential to address the challenge of providing sufficient electricity to densely populated areas. In an increasing number of cities, there is little room to expand underground cable networks and the cost to lay additional cable, including building new tunnels or ducts, is prohibitive. With their higher capacity, superconducting cables have the potential to increase the supply of electricity to an area using the existing underground cable footprint. Additionally, because HTS cables can carry more current at a lower voltage over longer distances, large power transformers could be located farther from urban centers and densely populated areas freeing up valuable real estate for development or green space.

Check out the flash animation at this website, that shows how an urban landscape can be transformed by the space efficiencies of superconducting cable such as the Triax HTS system. Urban real estate can be highly expensive, and anything that can free up land for more profitable use would be welcomed.

High-temperature superconductive cables are simple enough in principle. Encase a ceramic material in a silver tape, submerge it in liquid nitrogen, and run current through it. Temperature is the key. A conductor that carries 200A at -321 °F can carry 240A at -334 °F. Turn the refrigeration up and you get more capacity. You’ll lose about 0.5 percent of the power you transmit, where traditional power cables lose from three to eight percent. The trick is being able to manufacture your design. In the center of Southwire’s superconducting cable is a flexible pipe carrying liquid nitrogen. Superconducting tapes wrap around the pipe, followed by a dielectric layer, then a second layer of superconducting tapes that act as a neutral conductor. A double-walled outer cryostat surrounds the cable core and provides a return path for the nitrogen.

Hat tip to Energy Blog.


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