Post Apocalyptic Refrigeration
There are many options to do refrigeration with simple technology
one option is a Hilsch vortex tube — you could use a water wheel to power a compressor to provide compressed air to the cooling system using a Hilsch vortex tube for cooling
Another option is a ice ball cooler — simply 2 containers under pressure with ammonia and water inside heat one container to boil off the ammonia – and cool the other with water … then when you take the heat away the water will freeze around the second container.
link to some info on the Ice ball cooler….. more info on the The Crosley ice ball cooler….link to plans to make one yourself….