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[Logan]

Hello,
To transform heat directly into electricity, there are the calopiles.
In addition, I understand that they have fairly high yields since not based on a mechanical transformation of energy as in dish-stirling.

The problem is that their construction requires materials from nanotechnology, so it's still quite expensive.
I haven't done any research so I don't know if there are companies offering them for sale ...

[Logan]

After research, it turns out that the calopile does not have the drawbacks (cost and yield) of thermopiles based on the peltier effect.

http://automatique.free.fr/calopile.html

PRINCE

CONVENTIONAL THERMOELECTRIC GENERATORS

A thermoelectric generator transforms heat into electricity without requiring mechanical movements like those of a piston or a turbine, or chemical reactions like those which take place in an accumulator battery, a battery or 'a fuel cell.

The physical principle which is implemented in a thermoelectric generator is "the Seebeck-Peltier effect", namely:
when a solder which links two conductive branches, of a different and adequate nature, is heated, an electric current is released at the cold end of these two branches.

What could be simpler and more ecological to produce electricity?

However, this system has two major drawbacks:

a) the low conversion efficiency,
B) the very high cost of said suitable materials, which are specific semiconductors resulting from very elaborate manufacturing processes and which limits the outlets to very precise applications, including the aerospace industry or military use.

_____________________________________________________________________________________

THE CALOPILE

In the CALOPILE, things are different:

1) The two branches in question are ordinary conductors (copper or other), but at their ends is reported a tiny layer of semiconductors (specially developed for CALOPILE) and it is the latter which make the contact between said pair of branches.

2) Instead of heating the junction (ex welding), only one of the two branches is heated and the other is cooled.

Therefore, we no longer speak of welding, but of "P / N" junction as for a transistor, the Seebeck-Peltier effect is not intrinsically implemented and we therefore prefer to speak here of "bithermal" junctions, and this, as opposed to “monothermal” welds, used in conventional thermoelectric generators.
But these two novelties must be implemented jointly for this to work and semiconductors specially developed for bithermal junctions must be used to obtain an acceptable yield.

A CALOPILE made according to this process has a considerable advantage:
Thus, the thickness of the semiconductors, which in a case of measurement measures 5 mm in a conventional thermoelectric generator, is reduced here, to 2,5 microns ... hence a reduction in their cost, by a factor of 1 at 1000!

By cons, no news from the company supposed to produce the calopile.
I did not find anything on the Net ...

[Logan]

Yes, but the output is equivalent to that of a solar cell for a much lower cost. In addition, there are more applications and with a cogeneration system (domestic hot water) the yield is further increased.

The ideal would be to be able to use thermal solar as a hot source, since the capture systems are quite simple to manufacture.
The problem is that you must at least reach a differential of 70 ° C (hot / cold source) for its to work well.
Using a satellite dish and a Canadian well for the cold source, maybe ...

[Philflam]

B)