“Peltier-Seebeck effects”
About 12 years ago I picked up an portable 12v Igloo cooler/warmer chest using that effect and it worked pretty good. During 90 degree weather in Chicago the ice cube tray formed ice cubes and kept the frozen food in a stable state. It also used a hell of a lot less juice than a normal refridge would. The only problem was that it created a lot of RFI when using the 120 ac/ 12v dc transformer when used in the apartment. Still have it in storage.
I had an Igloo that we sat between the seats of my Pontiac, and it did a good job.
My dad had one that was heated by propane. It was heavier duty than my electric one.