http://www.thermonamic.com/Pspec.html

http://www.varmaraf.is/engl/prod.htm

http://www.powerchips.gi/

http://www.dts-generator.com/

http://www.hi-z.com/

http://www.fieldlines.com/story/2004/9/25/14932/7951
http://www.fieldlines.com/story/2004/9/29/17922/4377

Yes, I started that discussion :-).

<The peltiers seem to be more costly per watt than solar or wind, so there hasn't been as much work here on them.>

That's true.. a single peltier element can cost about $30 retail, and you can get a few watts out of it.  But I've purchased them for as little as $3 on eBay, and so now the price per watt comes way down.  But that's just the price of the peltier.. the element itself won't generate electricity.  You need to connect it to other hardware.

You can read the other thread where I discussed my ideas.. which have changed a bit since then.  My goal is to create a portable power generator, something I can put into a backpack and take camping.

To summarize, my original thought was to use a one-gallon paint can with the peltiers sandwiched between the lid and a piece of aluminum.  Have the heat source inside the paint can and water on top flowing in from a tube from a creek and then out again to keep a cool water source.  This design proved very complicated and a bit bulky to carry.

So my current idea is to use cans that are shaped like upside-down pyramid with the "point" cut off.  The place where the "point" would be cut off would be the bottom and the perfect size for a square peltier element.  The reason for this particular shape is that using this design would require several of these devices to be connected in series to get the voltage that I'd need to charge a 12V battery, and this shape allows them to easily be stacked so that they don't take up a lot of space.  The element would sit at the bottom of this unit sealed in with a piece of aluminum over it.  Then, I would fill this with water and sit it on a campfire.  The campfire would provide the hot side, and the boiling water would provide the cold side since it cannot reach more than 212F, and the campfire will go well over that.

I have done a few experiments, and the most important factor that I have found is pressure.  You have to have great amounts of evenly distributed pressure applied to both sides of the element to have the heat flow through as quickly as possible.  The faster the heat flows, the more power that's generated.

My current dilemmas are how to apply the needed pressure to the peltier (I don't know whether or not this is a job for glue, the recommended pressure us 200PSI), and how do I run the pair of wires from the peltier so they are not damaged by potential exposure to the heat.. since they'll be coming right out of the bottom of the can where the heat source is.

My vision was more toward a solar aspect using a peltier in the place of a solar condenser - or is that as a solar collector?  I'm new to this line of though so bear with me.  I was thinking along the lines of lenses focusing light onto black steel sheeting with peltiers attached to the back of the steel panel.  The opposite side of the peltiers would be attached to a large aluminim heat sink that sat in the shadow of the device.  Some form of insulation would be needed to isolate the heat dissipating off the hot steel from warming the aluminum heat sink.  The though being, the steel would heat durring the day and maybe give enough temperature difference between it and the aluminum to create some power.  May be possible to use the airflow created by the hot steel heating the surrounding air to help cool the aluminum heat sink.  I would think though that the power would spike once the sun set and air temperature decreased enough to allow the aluminum to dissipate at a greater rate while the steel would retain it's heat for some time.

This is all purly speculation and I'm looking for input as to why this may or may not work.

As I recall from my Igloo one, when you pass a currant through 2 disimilar metals, one heats and one cools (copper,aluminum) and which way you pass the currant decides which side gets hot or cold, either Neg ground gets cold on the aluminum or copper side, to change sides for warming or cooling just change the polarity.

Now I wonder, if you connect a block of aluminum to a block of copper and attach wires, will currant be produced simply by heating the copper and cooling the aluminum? Simply reverse the process, instead of using electric to make heat use heat to make electric.

Since a peltier is so costly for such a small amount of power, and blocks of copper or aluminum cheap in comparision, maybe you could make your own peltier? Might be worth a try.

Also if you heat a thin copper sheet from the bottom till the top gets a black oxide, then rub off the black with steel wool or such till you have a red oxide under it you have a simple solar cell. Attach a wire to the copper back and the red oxide front and sit in the sun. Not alot of power, but it does work. You might want to use fine wire or aluminum window screen for the front as a grid to collect the power. Maybe make a few pounds of these to carry with you?
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nothing to lose