Peltier cell in series both electrically and thermally

[askingask]

So here you can see the basics behind a thermocouple.

What people usually do, is that they connect these junctions electrically in series and thermally in parallel.

Now another thing people do is cascading several peltier modules.

Now my thought was, why not connect them electrically in series and thermally also in series directly like shown above?
That way you cascade them on a cell level instead of on a module level.

I know that there is a reason why when the modules are cascaded the modules get bigger and bigger towards the warm end to effectively cool each stage.

What do you think about that idea and do you have any reference I could look in to?

 

[Flyboy]

I’m not an expert on this stuff by any stretch of the imagination, but I think running them in series electrically is going to either fry one, or cause one to severely underperform. I suspect they have different resistances and current demands, but will require similar voltages.

 

[askingask]

I’m not an expert on this stuff by any stretch of the imagination, but I think running them in series electrically is going to either fry one, or cause one to severely underperform. I suspect they have different resistances and current demands, but will require similar voltages.

They are actually usually connected in series. The peltier modules shown above are connected in series. That itself isn‘t interesting, the interesting part is them being thermally in series as opposed to being thermally in parallel like the peltier modules shown above.

 

[Baluncore]

I know that there is a reason why when the modules are cascaded the modules get bigger and bigger towards the warm end to effectively cool each stage.

What do you think about that idea and do you have any reference I could look in to?

The limitation is on the thermal insulation that is required between each layer of Peltier junctions. You must build colder insulated spaces inside cooler insulated spaces, like those Russian dolls.
https://en.wikipedia.org/wiki/Matryoshka_doll

Even with perfect peripheral insulation, there is a maximum temperature difference possible per module. That is determined by the maximum current, since that must provide for the thermal conduction, backwards through the Peltier module itself.

Your first reference should be ...
https://en.wikipedia.org/wiki/Thermoelectric_cooling

 

[Rive]

Now my thought was, why not connect them electrically in series and thermally also in series directly like shown above?
That way you cascade them on a cell level instead of on a module level.

The modules themselves are already a combination of series and parallel connections on junction level: the 12V (or other convenient) operating voltage is the result of that.

You can add further elements in series, but you need to match current: you can add more parallel, but then you should match voltages (that's what happens on that pyramid-stack on the picture).

 

[askingask]

The modules themselves are already a combination of series and parallel connections on junction level: the 12V (or other convenient) operating voltage is the result of that.

You can add further elements in series, but you need to match current: you can add more parallel, but then you should match voltages (that's what happens on that pyramid-stack on the picture).

You mean electrically?