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What Are the Different Types of Thermoelectric Materials?

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  • Written By: M. Kayo
  • Edited By: Susan Barwick
  • Last Modified Date: 19 July 2014
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The thermoelectric process is the direct conversion of heat into electricity and back again in the heating or cooling of an object. Thermoelectric materials can be used to measure temperature changes, change the actual temperature of a object, and generate an electrical charge, which can be used to generate power. In 2011, thermoelectric materials too inefficient to be useful, but automotive engineers are attempting to use them to glean wasted heat energy from a vehicle and turn it into usable electricity. Researchers are attempting to increase the efficiency of thermoelectric materials to make them more economical so they can be used to create low cost and more efficient refrigerators, air conditioners, and other devices that require cooling.

Thermoelectric processes occur because of the Peltier effect, which is the cooling and heating of opposite junctions in electrical circuits containing dissimilar semiconductors. Thermoelectric materials may be used to create cooling devices or to provide refrigeration. One of the common thermoelectric materials used today is bismuth telluride, an expensive compound that can cost as much as $1,000 US dollars (USD)/lb ($2,000 USD/kg). When properly prepared, this thermoelectric material produces reliable temperature changes anywhere between 14 to 266 degrees F (-10 to 130 degrees C). Thermoelectric systems perform reliably and precisely without the noise of conventional heating, cooling, and refrigeration systems and without environmentally harmful chlorofluorocarbons (CFCs).

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For several years, the National Aeronautics and Space Administration (NASA) has harnessed the power of thermoelectric materials to power space probes in the deepest reaches of space, so far from the sun that solar panels are useless. The process involves imbedding nuclear material in a radioisotope thermal generator, in which the radiological decay produces heat energy that is then converted into electricity to power the probe. This is the same process that automotive engineers are trying to harness from the exhaust heat of car engines — heat which can be converted into electricity to power the car.

Research and development in thermoelectric materials is being conducted by the Energy Frontier Research Center at the Massachusetts Institute of Technology (MIT). There, researchers and scientists have made some rather significant discoveries, such as the coupling of thermal disorder and electronic structures at a finite temperature. The current challenges in this field are identifying or synthesizing new, as yet undiscovered, materials with more efficient thermoelectric capabilities. Advancements in this field may enable the development of materials that generate electricity from waste heat, providing a sustainable global energy solution.

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nony
Post 4

@David09 - Getting electricity out of waste heat is the best idea so far in my opinion. I know someone who graduated with a degree in biochemistry and she loves the possibilities of creating energy from biofuels.

She says you can take waste products to do this, and of course everyone has heard of ethanol and things like that. However, I think that the thermoelectric approaches are better.

That’s because heat is more abundant than waste stuff, and it’s usually cleaner in the end.

David09
Post 3

@everetra - It wouldn’t matter anyway. We would have gotten a lot of information from the probe before that time came, I would think, and so the whole thing would have been worthwhile.

Just look at other devices that have had shorter life spans. Take the Mars Rover. That didn’t last long, yet scientists hailed it a success because it landed successfully on Mars, and sent back tons of information about the Martian surface.

I think the nuclear powered thermoelectric generator on the space probe offers a lot of bang for the buck, comparatively speaking.

everetra
Post 2

@Charred - I would give it a few more years. I am more intrigued by the use of nuclear power for the space probes. If they are using radioactive decay to power the probes, there is clearly a limit to how far they can go, isn’t there?

I mean at some point the nuclear isotope is going to be totally decayed, and so it won't provide any more fuel. At that point the space probe is quite literally lost in space.

It may be hundreds of years however before something like that happens. I don’t know how much mileage they get out of those nuclear reactions.

Charred
Post 1

If you are going to use the thermoelectric effect to create electricity from car exhaust, you’ll need to build a special device to do that.

Somehow, I think that at current technology levels that device would have to be pretty big. As a result it may impose some drag on the car, slowing it down, and so you may wind up with a net loss in terms of usability.

That’s my opinion anyway. Until I see a working prototype I have yet to be convinced otherwise. It’s like the way it is with hydrogen fuel cells. In principle it works fine but the hydrogen tanks are so big as to be impractical for most cars.

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