The peltier module I have played with and used for a project measured about 40x40x3 mm and was rated at 75W, from memory.
These things are as simple as it gets.
Supply power to it and one side cools while the other heats up.
Now, if you do that in free air (or, as you plan, by placing the module under a container) you'll be *very* disappointed by the results :wink: .
Why? The cold from one side will immediately get equalised by the heat from the other.
You HAVE to physically seperate the air at both sides so you will have to mount the module so it becomes part of an enclosure - like a cooler box.
Usually the hot side is mounted on a large heat sink, fan cooling this will improve its performance.
The cold side fits against a metal plate inside the cooler to radiate the cold (can one 'radiate' cold? - you know what I mean :wink: )
AND in between the two you should have as much insulation material as possible. The thicker and the better its thermal coefficient the better.
This last requirement is the hard part since the module is so thin, makes for some tricky engineering to get a reasonable efficiency. Have a good look at how peltier coolers are constructed and go from there. There is room for improvement as these coolers are built to a price.
I controlled it with a temperature sensor, turning the power on and off. Due the thermal lag of a good cooler this cycling is not very rapid at all.
Now, for your application, I think Its not going to be satisfactory if you drink a lot of water. And, its rather power inefficient when compared to other refrigeration methods. Its neat though
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The best way to use peltier coolers is to place things into them cold (or hot) and use the cooler (warmer) to keep the contends at this temperature. If you try to use it as a fridge it'll be disappointing.
If I remember right the max hot/cold plate temp difference is around 40 degrees C. The modules can be cascaded for bigger differences but at the price of even more complexity.
Have fun
Klaus