Just a heads up for off grid people. A simple cheap way to have a nice fridge is looking for a used gas 2 or 3 way fridge from a camper, RV or trailer. They can be found in wrecking yards and on CL. I’ve messed around with gas fridges for years and used to sell the smaller ones to people going to BM. In my experience the Dometic ones are much higher quality than the Nor(Not)cold ones. These fridges almost never go bad. About the only failure is if the cooling unit gets rusted out or a hole burned in it. Easy to replace parts like the ignition unit or thermocouple may need to be changed, but that’s usually rare. Most people have issues due to neglect and user error. People don’t take the time to learn about them and how they function. They let them sit unused for long periods of time and try to use them when they are not level.
Basically they work by using a heat source to both move the refrigerant and to provide the energy for cooling. The heat source and be a gas flame or an electric heating element. The units can have both AC and DC heating elements if they are 3 way. Because they do not use a compressor, the refrigerant is dependent on convection to flow. If the unit is too far from level, the refrigerant will not move efficiently. If they sit too long unused, the refrigerant can separate and cause a clog inside the cooling unit tubes. If that happens, the flow will be blocked or restricted. Simply turning the unit on it’s other 3 sides for a few minutes each will usually fix any internal blockage. You can hear the refrigerant gurgle when it moves inside the cooling unit.
A flaw they do have is that they usually don’t have an internal fan. This makes them slow to cool down at the start and they don’t work as well if they have a lot of unused internal space. Humid air also reduces their efficiency. Installing a small fan inside to move air inside will make them work much better. Even a small battery powered fan will help.
Someone who likes to tinker can probably make one work with alternative fuel sources like biodiesel, scrap wood/gasification, and maybe crazy ideas like steam or even focused sunlight. All you need is a steady heat supply on the lower pipe of the cooling unit.