This is big news to the
transmission business claims to the contrary notwithstanding. It is all about line loss. These do the job and they are light enough to
suspend in the air.
The industry has been waiting for
this option so that the training required covered a wide range of their
equipment rather than an occasional stand alone device. That has surely ended.
This means that everything in the
power business will now be retro fitted as swiftly as possible.
While they are at it, they may
even be able to harden a lot of the infrastructure against EMP events. The shielding has become necessary anyway
because of the huge power throughputs involved and superconductor tape does shield out external magnetic fields.
Eliminating the majority of line
loss, 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-field
magnets.
WEDNESDAY, FEBRUARY 23, 2011
BY PRACHI PATEL
Superconductor coil: The cross section of a new type of
high-temperature superconducting cable shows a multistrand copper core spirally
wound with superconducting tapes.
Researchers at the National Institute of Standards and Technology
(NIST) have found a way to make high-temperature superconducting power
cables that can carry as much current as existing superconducting cables while
being a tenth of the diameter. The thin, flexible cables could open up new
applications in electrical power transmission and could lead to powerful new
magnets.
The cables could provide a lightweight, compact replacement for copper
power cables, says NIST researcher Danko van der Laan, who led the work. Superconducting
magnets made with the cables would generate much higher magnetic fields than
are possible today. Such high fields would be useful for high-energy physics
and proton cancer treatment.
Superconductors conduct high electric currents without heating up or
losing power when they are cooled. The superconducting magnets found in medical
imaging devices and particle accelerators typically use niobium alloys that
turn superconducting below 10 °Kelvin (-263 °C). But certain compounds made of
rare earth elements, barium, copper, and oxygen also become superconducting
at higher
temperatures of over 70 °Kelvin (-203 °C), at which point they can be
cooled using liquid nitrogen or helium gas.
High-temperature superconducting cables have been touted as a promising
alternative to copper cables for electric power transmission in
urban settings and compact spaces. That's because just one superconducting
cable could replace over 10 copper cables, cutting weight by over 95 percent
and eliminating heating loss.
Cryogenic superconducting power cables are
typically made using superconducting "tapes" wound
around solid or hollow metal cores. The tapes are thin strips of metal coated
with a micrometer-thick layer of superconductor and films of ceramic
insulators. Superconducting cables have recently been used in small power grid
demonstrations. A bismuth-based cable was installed at a utility substation in Columbus , Ohio
In comparison, van der Laan has made a cable 7.5 millimeters wide that
can carry 2,800 amperes. Another is 6.5 millimeters in diameter and can carry
1,200 amperes. The cables can be bent around a cable with a diameter of less
than a quarter of a meter.
Van der Laan starts with a core made of multiple copper strands
sheathed in nylon insulation. Then he winds gadolinium barium cuprate
superconducting tapes in alternating directions around the core. His
experimental results were recently published online in the journal Superconductor
Science and Technology.
Conventional superconducting cables are lighter than those made of
copper, but are still so heavy that they have to be buried underground, van der
Laan says. "Researchers are looking at options for using them as overhead
lines instead of underground," he says, "but conventional cables have
been too heavy to use overhead. One benefit of our cables is they're much more
lightweight."
Until now, it was assumed that you could not make superconducting
cables so thin, says Venkat
Selvamanickam, a mechanical engineering professor and high-temperature
superconductivity expert at the University
of Houston
David Larbalestier, a scientist at the National High
Magnetic Field Laboratory in Tallahassee, Florida, says the new cables are a
perfect 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 into
power transmission, though. "Many people would love to use
high-temperature superconductors to revolutionize the electric utility
industry," he says. "But the industry is relatively conservative and
not used to cryogenics. On the other hand, the big multibillion dollar market
for superconductors is making magnets that consume very little power."
Today's superconducting magnets contain niobium-titanium wires wound
into coils that can provide at most 25 Tesla magnetic fields. Magnets made
using the new high-temperature superconducting cables could give higher fields
while potentially requiring less power for cooling. Such compact, high-field
magnets could be used for proton cancer treatment and high-energy physics, van
der Laan says.
Researchers at CERN (the European Organization for Nuclear Research)
in Switzerland
The low weight and flexibility are especially appealing to the military
as a replacement for the bulky copper cables that carry large amounts of power
from generators to weapons and devices on board aircraft and ships. "If
you look at replacing standard copper cables on a Navy ship, you have to be
able 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.
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