These Are Not Your Father’s TEDs

Researchers at Wake Forest University's Center of Nanotechnology and Molecular Materials are working with some interesting stuff. They have developed a cloth-like material made from carbon nanotubes that has thermo-electric properties.

Thermoelectric devices (TEDs) have been around since the 19th century. A TED is created when two dissimilar metals are placed in contact and heated. A potential is developed across the junction and associated wires, and current flows from one metal to the other and through a connected load. This effect and the related cooling effect was discovered and analyzed by the French physicist Jean Charles Athanase Peltier and the German physicist Thomas Johann Seebeck. A TED will work the other way: If a current is forced through the junction, one side gets hotter and the other side gets colder. If you stack up plates of dissimilar materials, you can make a small “heat pump” and cool the CPU in your overheating laptop computer.

Materials used for simple TEDs — like the one in your gas water heater that keeps the valve open as long as the pilot flame remains lit — are made from inexpensive materials like iron and constantan. The Seebeck constant for an iron-constantan junction is about 55uV/deg-C. For the heat pump version, bismuth and telluride works pretty well, but it's a lot more expensive.

Apply electrical energy, and heat gets pumped from top to bottom. (Source: Wikipedia)

Apply electrical energy, and heat gets pumped from top to bottom.
(Source: Wikipedia)

Apply a temperature differential (hotter on the top), and you get a current flow. (Source: Wikipedia)

Apply a temperature differential (hotter on the top), and you get a current flow.
(Source: Wikipedia)

At Wake Forest, they've got a type of TED made of carbon nanotubes and plastic fibers that responds to a temperature differential. Since it's small and can be made inexpensively, the hope is that they can make a thermopile that will produce enough power to be practical. They plan to turn what they've developed in the lab into useful, manufacturable products that could recover waste heat in cars and trucks and produce electricity in usable quantities. Or use your body heat to recharge your cellphone battery. Also you could have clothing that keeps you warmer — or cooler — than the ambient temperature as the need dictates. And, of course, there's heating and cooling of buildings.

The research appears in the current issue of Nano Letters, titled “Multilayered Carbon Nanotube/Polymer Composite Based Thermoelectric Fabrics.” Wake Forest is in talks with investors to produce its Power Felt product commercially.

3 comments on “These Are Not Your Father’s TEDs

  1. SunitaT
    February 6, 2013

    Brad, Thanks for the post.

    Power Felt can be used as thermoelectric generators. Most thermoelectric generators are inefficient. But generators using waste heat produced by engines, solar energy, wind energy then low efficiency may be practical.

  2. eafpres
    February 6, 2013

    Hi Brad–there is a lot of interest in TEDs.  They are used more widely than most realize.  TEDs show in in things like DNA sequencers becuase it is easier to control temperature with them.  They are used in some opto-electronics becuase the lasers need to be temperature stabilized to stay on frequency, so the are held above ambient and actively controlled.  

    There are several areas of research regarding power generation.  Efficiency is the big issue for any application where size/weight is a concern.  So in cars, people are working hard on high-temperature TEDs that can generate powr off the waste heat from the catalytic converter.  Likewise for large-scale power generation.

    An interesting area of work is to increase the absorption of solar energy as heat directly onto TEGs (Thermo Electric Generators) to improve efficiency as compared to photovoltaics.

  3. Brad Albing
    February 12, 2013

    It's good to know there are a lot more applications for the devices than I had initially thought. So people are not just making chillers for their 6-packs of beer.

    Definitely a field to which I will pay more attention.

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