Super-thin Superconducting Cables

This is big news to thetransmission business claims to the contrary notwithstanding.  It is all about line loss.  These do the job and they are light enough tosuspend in the air.

The industry has been waiting forthis option so that the training required covered a wide range of theirequipment rather than an occasional stand alone device. That has surely ended.

This means that everything in thepower business will now be retro fitted as swiftly as possible.

While they are at it, they mayeven be able to harden a lot of the infrastructure against EMP events.  The shielding has become necessary anywaybecause of the huge power throughputs involved and superconductor tape does shield out external magnetic fields.

Eliminating the majority of lineloss, not only saves energy it makes two way integration much more economic.

Super-thin Superconducting Cables

New compact cables show promise for power transmission and high-fieldmagnets.

Superconductor coil: The cross section of a new type ofhigh-temperature superconducting cable shows a multistrand copper core spirallywound with superconducting tapes. 

Researchers at the National Institute of Standards and Technology(NIST) have found a way to make high-temperature superconducting powercables that can carry as much current as existing superconducting cables whilebeing a tenth of the diameter. The thin, flexible cables could open up newapplications in electrical power transmission and could lead to powerful newmagnets.

The cables could provide a lightweight, compact replacement for copperpower cables, says NIST researcher Danko van der Laan, who led the work. Superconductingmagnets made with the cables would generate much higher magnetic fields thanare possible today. Such high fields would be useful for high-energy physicsand proton cancer treatment.

Superconductors conduct high electric currents without heating up orlosing power when they are cooled. The superconducting magnets found in medicalimaging devices and particle accelerators typically use niobium alloys thatturn superconducting below 10 °Kelvin (-263 °C). But certain compounds made ofrare earth elements, barium, copper, and oxygen also become superconductingat highertemperatures of over 70 °Kelvin (-203 °C), at which point they can becooled using liquid nitrogen or helium gas.

High-temperature superconducting cables have been touted as a promisingalternative to copper cables for electric power transmission inurban settings and compact spaces. That's because just one superconductingcable could replace over 10 copper cables, cutting weight by over 95 percentand eliminating heating loss.

Cryogenic superconducting power cables aretypically made using superconducting "tapes" woundaround solid or hollow metal cores. The tapes are thin strips of metal coatedwith a micrometer-thick layer of superconductor and films of ceramicinsulators. Superconducting cables have recently been used in small power griddemonstrations. A bismuth-based cable was installed at a utility substation in Columbus, Ohio,in 2006, for instance. It has a diameter of seven centimeters and can carry3,000 amperes.

In comparison, van der Laan has made a cable 7.5 millimeters wide thatcan carry 2,800 amperes. Another is 6.5 millimeters in diameter and can carry1,200 amperes. The cables can be bent around a cable with a diameter of lessthan a quarter of a meter.

Van der Laan starts with a core made of multiple copper strandssheathed in nylon insulation. Then he winds gadolinium barium cupratesuperconducting tapes in alternating directions around the core. Hisexperimental results were recently published online in the journal SuperconductorScience and Technology.

Conventional superconducting cables are lighter than those made ofcopper, but are still so heavy that they have to be buried underground, van derLaan says. "Researchers are looking at options for using them as overheadlines instead of underground," he says, "but conventional cables havebeen too heavy to use overhead. One benefit of our cables is they're much morelightweight."

Until now, it was assumed that you could not make superconductingcables so thin, says VenkatSelvamanickam, a mechanical engineering professor and high-temperaturesuperconductivity expert at the University of Houston. "Theconcern was whether the tapes could be bent at such small diameter cores andstill maintain high current carrying capacity without any damage."

David Larbalestier, a scientist at the National HighMagnetic Field Laboratory in Tallahassee, Florida, says the new cables are aperfect example of good engineering. "There's no new rocket science here.They have applied perfectly standard techniques to make a cable."Larbalestier does not think the new cables will easily find their way intopower transmission, though. "Many people would love to usehigh-temperature superconductors to revolutionize the electric utilityindustry," he says. "But the industry is relatively conservative andnot used to cryogenics. On the other hand, the big multibillion dollar marketfor superconductors is making magnets that consume very little power."

Today's superconducting magnets contain niobium-titanium wires woundinto coils that can provide at most 25 Tesla magnetic fields. Magnets madeusing the new high-temperature superconducting cables could give higher fieldswhile potentially requiring less power for cooling. Such compact, high-fieldmagnets could be used for proton cancer treatment and high-energy physics, vander Laan says.

Researchers at CERN (the European Organization for Nuclear Research)in Switzerlandare also interested in using the thin cables to feed the several thousands ofamperes of current to the magnets used at the LargeHadron Collider.

The low weight and flexibility are especially appealing to the militaryas a replacement for the bulky copper cables that carry large amounts of powerfrom generators to weapons and devices on board aircraft and ships. "Ifyou look at replacing standard copper cables on a Navy ship, you have to beable to pull the cable through existing conduits with many sharp bends,"van der Laan says. He is now making a demonstration cable for the U.S. military.

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