heat to electricity

[shankle]

Would like to hear some more about this from you engineers.
Was on intelsat 9ku last night listening to a program on Airiang from S. Korea.
They were talking about a wafer say 2" by 2" by 3/8" thick that produced electric. It was hot on one side and cold on the other when heated.
There were a whole bunch of chips say 3/8" by 5/8" by 1/8" thick covered on both sides by an insulator on this wafer. (I'm guessing  these measurements).
My understanding gets muddy here as I think one chip was positive and another chip was negative. They connected 2 wires to this wafer
and were able to light a bulb with it. And again my understanding is muddy, a positive chip the electrons went one way and the negative chip
the electrons went another way. This is what produced the electricity.
Applications for this are limitless. Materials that do this are rare. They talked some about substitutes for these rare elements and I think
they found some that were more abundant.

The whole idea of this is to cut world wide usage of oil, coal and gaseous gas.
An application of this would be in an automobile engine to take the wasted heat from the engine and generate electric and recharge the battery.

If you know of a site that explains this for non engineers I would appreciate it.

[dedndave]

i got to play with one of these wafers back in the mid-80's
a friend of mine had somehow acquired a small one - say 1.5" on each side - about 1/8" thick
if i recall, it was made of beryllium (ceramic-like) - which is a very hazardous material in powder form - so if it chips, be careful
not only is it capable of generating electricity, it works in the reverse, as well
applying electricity to the substrate (via some metalized film i presume) causes heat to be generated on one side, while the other side is cold
i would have liked to seen more of these wafers to play with
my thinking was - "what a great heat-sink" - put the cold side on the integrated circuit or transistor and put the juice to it
semiconductors can handle an amazing amount of power, so long as you are able to keep the junction temperature from climbing past a certain point
the material is expensive - i have only seen it used in one application - for cooling a micro-wave circuit

[shankle]

Thank you Dedndave for responding.
I got the idea from the program that this was something new.
The insulator was white and looked like styrofoam but who can tell from a TV.
If I should get to see it again I will try to write down some of the compounds they were made from.
Evidently what prompted all this is the Green effort being made world wide.

[FORTRANS]

Hi,

   Look for thermal-electric (sp?) cooling.  They have made heat
sinks and beer coolers with them.  Producing electricity is/was
very inefficent.  Maybe if they got a bulb to light with one
wafer, it might be a breakthrough.

Steve N.

[BogdanOntanu]

Peltier effect ;) - for cooling / heating

I have seen it used in small refrigerators / coolers.

Seebeck effect - for generating electricity.

I have seen it used in temperature sensors.

I guess that silicon solar panels are better for generating electricity from Sun light and an Stirling engine is more efficient for generating mechanical work and then electricity from an small temperature gradient.

[MichaelW]

The efficiency is very low whether the device is used as a generator or a heat pump.

http://en.wikipedia.org/wiki/Thermogenerator

A while back the devices starting seeing use for CPU coolers, but they had the problem that compared to the normal HSF coolers they produced a very large increase in the heat generated within the case.

[BogdanOntanu]

Again, for heat to energy conversion your best solution would be an Stirling engine and if you have a machine shop then you can do it yourself (the engine).