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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 soydios on 10/8/2008 4:59:29 PM , Rating: 4
Number of collisions. That electron collides with a lot of the conductor's molecules as it drifts.

RE: Pinky calling for the Brain.
By menace on 10/9/2008 2:10:43 PM , Rating: 2
It has more to do with the force interactions with the other electron and nucleii. Photons to not carry any charge or weight and are able to move through a transparent medium with negligible energy transfer. Pushing EM waves through wires (via the electrons present in the medium) results in a small but significant portion of the energy being transfered into the wire. The heat conversion surely has to do with quantum mechanics but I'm not smart enough anymore to explain how.

By the way, the electrons themselves don't move across a wire at relativistic (near light) speeds but the energy they transfer across the wire does. And this is true regardless of if the current is AC or DC. A good analogy is to envision a long pipe full of ping pong balls. If you push one ping pong ball at one end, a ball immediately pushes off the other end even though no single ball moved more than the diameter of a ball.

RE: Pinky calling for the Brain.
By amanojaku on 10/9/2008 3:37:05 PM , Rating: 3
Exactly. One physicist pointed out that a human can run faster than an electron can move, unless that electron is infused with energy from an external force. Unless the electron jumps up a valence shell, eventually escaping the atom to become a free electron, the energy is converted into a different type, like heat, light, etc...

The energy that moves at light speed (in a vacuum) is the electromagnetic field. When traveling through a medium the speed moves at less than light speed, determined by the atomic composition. With the right atomic composition the electric field can move at speeds approaching light in a glass silica fibre. It will still generate a lot of heat, however, and is subject to electromagnetic interference, unlike light.

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