Nanotubes For Power Transmission Line Materials
As our demand for power
increases, the burden on our electricity infrastructure grows. This was dramatically demonstrated in the
2003 blackout in the Northeast. Upgrading our infrastructure is a recognized
priority. A major challenge is to develop new transmission line materials that
are of lighter weight and lower loss than copper. Individual carbon nanotube
fibers have an electrical conductivity similar to or better than copper at only
one-sixth the weight and with negligible eddy current loss. This high conductivity derives from the
highly efficient transmission of electrons down the individual tubes acting as
quantum wave guides in one direction, and the efficient resonant quantum
tunneling of the electrons from tube to tube as the current passes down the
fiber. Several researchers have
demonstrated that one single wall carbon nanotube can carry currents up to 20
microamperes. With an assumed 5%
efficiency of conduction from nanotube to nanotube along the length of the
fiber and a carbon nanotube packing density of 1014 per square centimeter, a
carbon nanotube fiber bundle could carry currents of
100 million amperes per
square centimeter – 100 times the current carrying capacity of the best low
temperature superconductors. With current technology, losses in power
transmission lines are about 7%.
Reducing these losses to 6%
would result in a national annual energy savings of 4 X 1010 kilowatt-hours
– an annual energy savings
roughly equivalent to 24 million barrels of oil.
Current production of
single-wall nanotubes typically results in fibers that are less than 100
micrometers
in length and have widely
varying electrical conduction properties. So, there are many technical
challenges to overcome: How can we consistently produce nanotubes with
controlled conduction properties? How
can CNTs be cost-effectively manufactured into ropes and fibers with desired
electronic properties? How can the
transmission at tube-to-tube junctions be increased to almost 100 percent?
Carbon nanotube fiber (above) and (below) photograph of recent capability to spin long carbon nanotube fibers [Courtesy of R. Smalley, Rice University].