Saturday, April 23, 2005

Carbon Nanotube Wires

Carbon nanotube wires could have performance characteristics similar to superconductors but at room temperatures, according to the MIT Technology Review:
[Dr. Rick] Smalley’s lab has embarked on a four-year project to create a prototype of a nanotube-based “quantum wire.” Cables made from quantum wires should conduct much better than copper. The wires’ lighter weight and greater strength would also allow existing towers to carry fatter cables with a capacity ten times that of the heavy and inefficient steel-reinforced aluminum cables used in today’s aging power grid.
Such nanotubes have virtually no resistance to electricity, but are stronger than steel. Nanotubes 100m in length have already been synthesized, but their construction must be identical for their conductivity to work. Smalley thinks he has a solution to this problem.

Smalley has a nice series of slide shows at his website; he also has a curriculum vitae, from which we learn he won the 1996 Chemistry Nobel Prize for the discovery of fullerenes, the predecessor to nanotubes. The presentation Our Energy Challenge (PowerPoint) given at the University of Illinois indicates he's very aware of the problems of using fossil fuels to power industrial civilization. Citing energy production as the number one problem facing mankind in the 21st century, he estimates that world energy consumption will rise to 30-60 terawatts by 2050. Noting that 165 TW of sunlight impinges on the earth's surface, he foresees

  • Energy transported electrically rather than as mass (coal, oil, etc.)
  • Radical increases in the amount of power routing capacity, interestingly on a grid that "does not need to be very reliable"
  • Local production and storage, supplemented by mass generation of all kinds,
  • "Mass Primary Power input to grid via HV DC transmission lines from existing plants plus remote (up to 2000 mile) sources on TW scale, including vast solar farms in deserts, wind, NIMBY nuclear, clean coal, stranded gas, wave, hydro, space-based solar... ”EVERYBODY PLAYS”" (i.e., all energy is welcome)
  • Hydrogen and methanol are the transport fuels
He sees these being enabled by tenfold improvements in solar power generation cost, and the photocatalytic conversion of CO2 to methanol (one of my favorite approaches).

Update, 4/24: In a comment on a Knowledge Problem post about using auctions as a mechanism for access to physically common resources such as transmission lines, I made the point that power generation isn't like telecom, which Lynne used as the basis for her idea. (Incorrectly, I said that copper is being used in long-distance power transmission; in fact, it's aluminum over reinforcing steel.) But carbon nanotube wires could change all that. Carbon nanotubes have already been measured in the lab to support current densities of 107 A/cm2, measuring resistivity at 3.4x10-5 ohm-cm. (By comparison, copper's resistivity is 1.5x10-3 ohm-cm -- about two orders of magnitude worse.) Replacing aluminum-steel transmission lines with carbon nanotube power lines would radically increase power density without requiring additional space. In sum, it could be the kind of breakthrough that might make her idea plausible.

Update 5/4: thanks to the anonymous commenter who pointed out my incorrect value for copper's resistivity; the correct value from Physics Factbook is about 16.7 nΩ-m, still appreciably better than the 340 nΩ-m. So perhaps what Smalley's after is a theoretical maximum of nanotube conductivity that has yet to be achieved. In any case, I regret the error and hope to have a followup post revisiting this matter published shortly.

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