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'Thermo-electric Power (was Heat Powered Fans )'
2005\02\18@094543 by Martin McCormick

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       I am deliberately asking what may sound like one of the
dumbest questions we've had on here in recent history, but this is
more along the lines of "What is the catch?"

       Thermocouples produce electric currents at any temperature
above absolute 0.  Voltages in series add,
so one should be able to place millions of thermocouples in series
and generate some power from the ambient temperature.

       Even the most rabid spammers haven't tried to sell something
like that so what really does happen if you hook a billion
thermocouples in series?  It obviously doesn't work since the
technology to make the world's largest series string of thermocouples
has existed for as long as we have been bonding metal together which
is a very long time.

       Can you imagine how terrible the voltage regulation would be
in such a setup?  I also suspect that as soon as one drew any current
from the stack, it would act like a heat pump and cool down just
enough to stop working.

       The amateur radio magazine "QST" once had an article
describing how to use a Peltier cooling element to generate enough
power to drive a very small transmitter.  It actually did work, but
one had to have a high temperature differential between the two sides
of the Peltier device such as almost boiling water on one side and ice
water on the other and the two sides began rapidly moving toward
temperature equilibrium as soon as the current started to flow.

Martin McCormick WB5AGZ  Stillwater, OK
OSU Information Technology Division Network Operations Group

2005\02\18@105421 by Harold Hallikainen

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Thermocouples generate power based on a temperature difference between the
cold junction and the hot junction. If both are at the same temperature,
no voltage. You might look at it as the two junctions generating voltages
of opposite polarity that are in series, so you could TRY to have just one
junction. But, it appears when you wire the circuit together, you always
have two junctions.

Harold



--
FCC Rules Updated Daily at http://www.hallikainen.com

2005\02\19@191516 by Martin Klingensmith

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Martin McCormick wrote:

{Quote hidden}

Hi there Martin
(I'm a Martin too)
Thermo-electricity has been used to produce electricity since before
mechanical generators, they were one of the first methods of producing
electricity for the electroplating industry. I can't seem to remember
the name of a website that I saw, but it had many examples of what I
think are called thermo-piles. They had many themocouples (up to
hundreds) and usually sat over a gas flame with the hot ends pointing in
and the cold ends pointing out in a star shape.

--
Martin K
http://wwia.org/sgroup/biofuel/

2005\02\21@092403 by Lawrence Lile

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I have always been fascinated by these devices.  I have a sample from one of
the companies mounted on a heat sink, with a pack of four AA batteries, and
a switch labeled "heat" and "Cold" which does exactly that.  It sucks down
batteries fast (they aren't too efficient) but it is really fascinating.  If
a bright. bored kid acts up in Sunday school i g ive it to him and ask him
to figure it out.  He is quiet for the rest of the hour.

How cold a temperature can one generate by stacking these devices?

--Lawrence



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