Peltier modules as Thermoelectric Generators.

A Peltier Effect Device [PED] which has a temperature differential 
applied across it produces a voltage at its terminals and may be used 
as a Thermoelectric Generator [TMG] .

There is quite a lot of material on the net re people using PEDs as 
TMDs.
Manufacturers who specialise in such things and presumably custom 
build their cells fro optimum TEG use get efficiencies in the 2% - 5% 
range.

Sometime after Christmas and before we go on holiday on about January 
5th I hope to turn 10 x 68 Watt PEDs into a PED of whatever 
performance may be achievable. Aim is to make something which can 
charge a 12V battery for laptop and lighting use. TEG to be heated by 
Propane.

I rate the odds of producing a reasonably useful device in the time 
available, given that much else must also be done, as rather low. 
Worth a try though.

Any input that anyone has on the subject would be most welcome. Please 
retain the  two ::s in the subject line if replying.

While these were not horrendously expensive I'd rather not turn them 
into scrap by overheating. To get the efficiencies they do "real" 
people run there PEDs at hot sides of several 100 degrees C (!!!). 
Thje maximum temperature rating of these 'off the shelf' no name brand 
cells is unknown.

I considered using boiling water as the hot side but this is liable to 
result in terribly low efficiencies.

One thing that's unclear (but will be les so after 'playing') is the 
heat flux that a given Peltier can actually be operated at. ie a 
nominally 68 Watt PED will have a maximum rated heat flux in TMG mode 
which is liable to be larger than occurs when used a a Peltier effect 
device.




        Russell McMahon

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