Path: utzoo!attcan!uunet!know!zaphod.mps.ohio-state.edu!ub!kitty!larry
From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: Thermoelectric coolers - how do they work - in English plea
Summary: Peltier effect has been known for a long time...
Message-ID: <4041@kitty.UUCP>
Date: 21 Sep 90 03:01:09 GMT
References: <4486@optilink.UUCP> <34081@cup.portal.com>
Distribution: na
Organization: Recognition Research Corp., Clarence, NY
Lines: 37

In article <34081@cup.portal.com>, dbell@cup.portal.com (David J Bell) writes:
> Simply, the Peltier effect gives a correlation between thermoelectric
> generation and electrical *pumping* of heat. Consider it analogous to
> the way a DC motor can be used as a generator: with a Peltier device
> (usually a P-N semiconductor junction, but I believe any two dissimilar
> conductors), if you heat one junction (remember, there are always
> effectively *two* junctions, but one may be made with copper wires
> between the active materials), it will produce a current, just like
> any thermocouple. If you drive a current into the device, though,
> one junction will get hot, and the other will get cold. Reverse the
> polarity of the driving current, and the hot and cold ends switch, too.

	It is interesting to note that the Peltier effect was discovered
in 1834, and was a logical derivation of the Seebeck effect discovered
in 1821.  In 1855 William Thompson (Lord Kelvin) derived a scientific,
thermodynamic relationship explaining both effects.

	It was not until around 1910 that the German scientist Altenkirch
gave serious consideration to thermoelectric refrigeration.  However, the
low Seebeck coefficients of materials available at the time precluded the
development of any practicable devices. 

	Thermoelectric refrigeration remained a curiosity item until the
1950's, when advances in development of semiconductors created materials
having a much larger Seebeck coefficients than previously available.
The primary material used in practicable thermoelectric refrigeration
devices is bismuth telluride, often used in conjunction with bismuth
selenide or antimony telluride. 

	I have often wondered what would have happened if a greater
understanding (or "luck") in metallurgy and chemistry had existed during
the 1800's, allowing the discovery of suitable semiconductor materials
for thermoelectric refrigeration at that time.

Larry Lippman @ Recognition Research Corp.  "Have you hugged your cat today?"
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