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To: aculeus
In cars, thermoelectrics could replace the alternator and save hundreds of millions of gallons of gas a year, according to an estimate from a General Motors researcher. (See "Free Power for Cars.") Organic materials are appealing because they cost much less than thermoelectric inorganic materials: even if they are inefficient, they might still be economical. "These molecules are dirt cheap," Majumdar says. "If the efficiency is low, that's fine. You're throwing that heat away anyway."

This has been discussed for decades. An assembly of thermoelectric modules, if clamped to a flat cast into the exhaust manifold, can generate clean DC from the waste heat. But regardless of the semiconductor's Figure Of Merit, the overall perfomance depends on temperature difference between the heat source and sink. If people take the easy way out, and use the engine's coolant as a sink, it is already at 165-195°F.

If the manifold reached 500°, then there is only a 300° Delta T.

One factor that has limited the usual bismuth telluride materials is their poor mechanical properties. After so many expansion/contraction cycles, they fail, because the hundred+ dies are connected in series, and it only takes one to open the circuit and render the device inoperable.

An organic thermoelectric will have limitations on it maximum temperature, limiting the Delta T, and the poorer Figures-Of-Merit, added to this limitation, probably just relegates this to a NanoDream™.

2 posted on 02/22/2007 6:50:36 AM PST by Gorzaloon (Global Warming: A New Kind Of Scientology for the Rest Of Us.)
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To: Gorzaloon

Thanks.


3 posted on 02/22/2007 6:58:37 AM PST by ChiefJayStrongbow
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To: Gorzaloon

Thanks.


4 posted on 02/22/2007 6:58:41 AM PST by ChiefJayStrongbow
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To: Gorzaloon

Bump


7 posted on 02/22/2007 7:18:10 AM PST by A. Pole (Condoleezza Rice: "Kosovo is a precedent for nothing, which is a very important point to make")
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To: Gorzaloon

You might want to look at powerchips.gi. They make the claim of 70% heat to electricity via the Josephson Junction process(hot electrons tunnel thru the nano-scale barrier, leaving the cold electrons behind). It's already in product testing, getting ready for mass production in europe. It will first appear in german cars. They also claim 40% efficiency in the cooling mode.


16 posted on 02/23/2007 1:02:39 AM PST by timer (n/0=n=nx0)
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