My Dad has a VW camper refrigerator collecting hobby.  99+ percent of the world's refrigerators and air conditioners use similar methods for cooling.  You compress a gas (refrigerant) and then let it cool off a little in a radiator before you release the pressure on it and it gets really cold.  The VW refrigerators use another method for cooling that uses heat somehow and was invented and patented by none other than Albert Einstein.  My Dad the physics professor who loves VWs couldn't help himself with that confluence of interests he had in VWs and physics, and since his fridge was on the fritz, he's been slowly buying up all the fridges in the North East when ever they show up on Ebay.  The fridge in his VW camper probably works better than any other in the US.

That will be a fun chore to get rid of those fridge guts when he passes.