I want to build a mini fridge, however, I want to build it a bigger than the ones showed in the tutorials I've watched.
For that I assume I need more than one peltier to cool it.
However, for that I need to know what is the maximum amount of space 1 peltier is valid for.
I want to make it 6 cubic feet.
How many peltiers would I need for that, and how much voltage do I need to power all of them?
EDIT:
I plan on using acrylic panels as its outside, laced with Auto Car Heat Sound Deadener Insulation and styrofoam
on the inside, including gaskets wherever needed to make sure no air escapes from the box.
In order to cool the heat sinks from the hot side I want to use several 12cm computer fans.
The average temperature in the room the coolbox will be in is about 30 degrees Celcius.
I need the cooling inside to average at 0-3 degrees celcius at most.
My plan is to use more than one cooler, in order for easier cooling as both will work at half the power, and thus will be less noisy.
Best Answer
Peltiers are very, very inefficient, compared to a compressor at least. With that volume box, you need to play hard-ball with physics, to get any useful performance at sensible power.
1) Insulate the box properly. Use PU panels (Celotex, Kingspan, that sort of thing), the thickest you can aesthetically use (my 20L coldbox uses PU 70mm thick). Rubber foam sound insulation will not provide anything like that performance.
Once you've figured out the surface area of the box, and the thickness of PU you're using, you can calculate how many watts you'll need to keep it below ambient, and so calculate how many Peltiers you'll need.
Here's an excellent online calculator, which given the power and the delta T you want to achieve, will give you figures for the lowest power, and the smallest (unfortunately not the same) way of achieving that.
2) Reduce the hot side temperature of the Peltiers by using an evaporation cooled water circuit (look up Bong cooler) to waterblocks to reduce the delta T the Peltier has to provide. Depending on the humidity, you will be able to get many degrees below the actual 'dry bulb' air temperature, approaching the 'wet bulb' temperature.
Better still, use a compressor solution, which is head and shoulders above Peltiers for efficiency and capacity.