We use propane fridges in some of our smaller off-grid installs. The electric fridge is a big electricity user, and although propane is not renewable, it’s often a first step to getting off the grid until your PV system is built up to the point where you have the capacity to run a energy star electric fridge.
The ammonia and water is heated by a propane flame [which is why it is called a propane refrigerator] thus causing it to vaporize into a steam through the perk tube. The process that this steam is being perked, is similar to a coffee percolator. The inner tube [perk tube] in the boiler emits steam & water bubbles moving upward. Since the ammonia is lighter than water, the ammonia will turn into steam sooner then the water will. This ammonia steam is pushed up into a condenser by the hydrogen pressure while the water falls down into the outer tube and is pushed into the absorber tubes which then returns to the mixing tank [absorber tank]. As the ammonia steam is moving upward through the rectifier and on into the condenser tubes it again turns into a rich ammonia liquid. This rich ammonia liquid is pushed into the top of the evaporator tubing. After it is in the evaporator it meets the hydrogen gas moving up through the inner tube inside the evaporator. This hydrogen gas absorbs the rich ammonia. As the ammonia meets this hydrogen gas in the evaporator it creates a chemical reaction . This reaction evaporates the ammonia thus making it extremely cold at that point. This is what is called absorbing the heat, or better stated, removing the heat from the refrigerator box.