How do you keep things cool?

Peltier elements can be stacked or cascaded to get more than the 30 degree differential. But they require power (could use solar but you are looking at 200-500W just for cooling, then a fan with a decent heatsink will be required to remove the excess heat from the hot side or it will leak/flow back towards the cold side.

we used stacking to keep some lasers cool for precision measurement.

The really aren't that efficient when you compare them to a propane fridge. You'll put a good deal of your off grid power into the device than is probably worth.

I like the idea of a propane fridge out of a travel trailer. No moving parts. Well if you don't consider toting the propane tank to the fridge.

 

Well, this type of evaporation cooler draws water from a pan on top and wicks it down the burlap sides, evaporating as it flows! I don't think ammonia or glyco or alcohol is something you want hanging in your kitchen or porch!

 

I wouldnt say absorbtion refrigeration is mature technology, hell it's almost Victorian technology.