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A new discovery made in thermoelectrical crystal compounds helps explain heat conduction at the molecular scale.

Though thermoelectric materials are quite common, they are not yet widely used as one might expect. The reason is largely that until very recently, these materials have been either very inefficient or very expensive. However, several groups of researchers have been working to solve the mysteries of these exotic compounds and bring them to the world en masse.

DailyTech has previously reported on a few endeavors with thermoelectrics. Mildred S. Dresselhaus's ongoing work at the Massachusetts Institute of Technology looks to create more efficient materials by manufacturing tiny particles or wires into them to disrupt the flow of heat. This would make materials that are already great electrical conductors much more thermally inert, allowing for greater heat-to-electricity or electricity-to-heat/cold conversion potential.

Another group at the University of California at Berkley, led by Professor Peidong Yang is looking into new materials. Silicon itself is not a great thermoelectric material – until venturing into nanoscale. Silicon nanowires have been shown to be one hundred times more efficient at the energy conversion than bulk silicon.

Publishing its findings in the most recent issue of Nature Materials, a group of scientists from the University of Århus, Risø-DTU and the University of Copenhagen has unlocked another secret of certain thermoelectric compounds which may help develop more efficient materials. Their work involves clathrate compounds, which are compounds composed of a “cage” of one type of molecule that surrounds a second type.

Initially it was believed that the movement of the trapped molecule was solely responsible for the way the compound conducted heat. After using neutron scattering to study the movement of the atoms inside the molecules, they realized it was the movements of the atoms in the cage that brought about the advantageous property.

Kim Lefmann, an associate professor of the Nano-Science Center, Niels Bohr Instituate at the University of Copenhagen explains, “Our data shows that, it is rather the atoms' shared pattern of movement that determines the properties of these thermoelectric materials. A discovery that will be significant for the design of new materials that utilize energy even better.”

Understanding the mechanism behind this thermal insulation will help scientists design better thermoelectric materials. These types of materials are finally being put to use in some of the places you might expect, such as vehicle auxiliary power generation from waste heat. The same waste heat could theoretically be used to power interior cooling systems via heat to energy to heat (and cooling) transference.

Thermoelectric materials have a tremendous amount of potential for use in everything from vehicles to homes and businesses to electronics. Better understanding of how these materials work will spawn more efficient materials and perhaps one day these things will be powered, cooled and heated by super thermoelectric devices.



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RE: Pinky calling for the Brain.
By amanojaku on 10/8/2008 9:55:22 PM , Rating: 2
FYI, a common misconception about the "speed of electricity" is that electrons flow through a conductor at less than the speed of light. This is true, but doesn't explain how electricity is transferred over a wire. It is the electromagnetic field that propagates at or less than the speed of light and transfers a signal.

The electromagnetic field is a force (vector): it has a magnitude and a direction. The proximity of moving charged particles (quarks, the negatively charged leptons, and the W force boson) create vector fields that affect each other. This interference (made worse by increased density of charged particles) is what reduces the speed of propagation of an electromagnetic field. It is theoretically possible, but practically improbable, for electromagnetic fields to align naturally in the same direction.

This is a gross over simplification of the nature of physics. Anyone describing the slower speed as a result of electrical resistance or the collision of electrons is wrong.

http://en.wikipedia.org/wiki/Velocity_of_propagati...
http://en.wikipedia.org/wiki/Propagation_delay
http://en.wikipedia.org/wiki/Electromagnetic_wave#...
http://en.wikipedia.org/wiki/Speed_of_electricity


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