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Ohio Researchers Advance Heat Reclamation Technologies
Downchuck writes "Researchers at Ohio State University claim to have synthesized a new material capable of delivering electricity directly from heat, at an efficiency far better than existing thermoelectric materials. Scott at ArsTechnica has an interesting take: 'Merge this with the new MIT solar dish and you're in business!'"
And since I can't make hyperlinks correctly on slashdot, I'll try again: thallium.
Nasty stuff, as its compounds are very easily absorbed through potassium uptake pathways in your body, but behave very, very differently from potassium. I seem to remember a chemist friend telling me that if you deal with thallium, you practically need an entirely separate lab for it.
"We are Microsoft. You shall be assimilated. Competition is futile."
You make electricity directly from heat. You can't make electricity directly from temperature (or stored heat) though.
heat != temperature
But you are right that you have to have a cold reservoir to get any work from the system. But heat in thermodynamics is not the same as temperature, and it generally denotes the amount of transfered thermal energy between two systems of differing temperature.
I'm assuming that the cold reservoir is the cooler temperature air surrounding the device.
This allows better RTGs, but they would only be marginally efficient for, say, reclaiming computer case waste heat. This is especially so as you can't put them on the CPU directly, where the differential is great, because they are insulating as well. You will need to put it at the radiating end, over a large surface.
The article at the Green Car Congress site titled New Approach to Developing Thermoelectric Materials Doubles Efficiency" has a lot more scientific details than that article linked from the summary, especially on the actual formula that determines "zT", which is the thermoelectric conversion efficiency coefficient:
And also detailed nanomaterials engineering analysis of the quantum structure of the quantum chemistry's thermoelectric effects.
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... contain a link to a possibly more useful article with some more comprehensible numbers:
http://www.technologyreview.com/Energy/21125/
e.g. The device could increase fuel efficiency of vehicles by approximately 10 percent.
But quadrupling them would. The old max zT these researchers were improving was about 0.87. They've now got it to about 1.5. And are targeting about 3.0 in their current research.
Freon refrigerators have a zT of about 3.0. Which makes these new materials look directly competitive with them for cooling when they reach that efficiency. Since zT 1 materials are about 10% efficient, zT 3 will be able to reclaim about 30% of waste heat. That would be about 20 points of the ~60% of gasoline energy wasted as heat in car engines. Since car engines are about 20% efficient now, that would mean doubling their fuel efficiency.
If these materials can be made, deployed, and recycled with close to (or less than) the energy inputs required now to make the car radiators/manifolds/exhaust systems they'd probably mostly replace, the benefits would be revolutionary.
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"A thermoelectric material designed to replace a conventional Freon-gas refrigerator must have a ZT of at least 3."
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