What is Absorption Refrigerator (Propane Refrigerator) and how it works?

When you say someone “runs hot and cold,” it isn't usually a compliment. But if it's a propane refrigerator, running hot and cold is a very good thing. Also known as an “absorption refrigerator,” the propane refrigerator proves that you can use fire to make ice – and you can do it al without electricity, or even moving parts.

 The device is based on some basic physics, first recognized by scientist Michael Faraday in 1828, when he liquefied ammonia gas and mixed it with silver chloride powder. As the ammonia evaporated, the mixture grew colder and colder – and the seeds of modern refrigeration took root. Thirty years later, French scientist Ferdinand Carre would combine water and sulphuric acid and get similar results, and by the 1920's, a century after Faraday's observation, the first commercially produced propane refrigerators were on the market.

The appliance operates on a system of heat, pressure, evaporation and condensation, with liquids and gases moving from chamber to chamber. Propane provides the heat source, which boils distilled water an ammonia mixture until the two ingredients separate. In the distilling process, the ammonia, which is lighter, is pushed upward into the condenser, while the water is pushed back down into the mixture's original tank. 

In the condenser, as it moves onward, the ammonia becomes a rich liquid and flows into the evaporator tube system, where it meets the compressed hydrogen gas that is rising to meet it. When the hydrogen and ammonia meet, a chemical reaction occurs. The ammonia evaporates, and in the process, absorbs the heat in in the refrigerator.

The propane refrigerator is a closed system, with sealed compartments and no moving parts. This means, for all practical purposes, that the process must be based on a cycle, endlessly repeating itself. The cold ammonia mist that was the result of its reaction with the hydrogen flows downward, mixing with the water in the tank to begin the process all over again.

The space needed for the tubes and cambers can limit the space of an absorption refrigerator, compared to an electric, but the lack of moving arts such as motorized compressors, make the propane appliance virtually maintenance free. Keeping dust, lint and other debris away from the burner vents is essential to smooth operation, and if the model has a flue, it needs to be cleaned on a regular basis. Because the flow of water, ammonia and hydrogen is essential to the operation of the device, the propane refrigerator should be kept as level as possible.

The units can take up to 24 hours to cool, so it's a good idea to start the refrigerator up a day before it is stocked, and keep in mind that of the seals aren't sealing, the refrigerator will not be operating at maximum efficiency.

Most problems that pop up on the troubleshooting lists don't involve the unit so much as they do the heat source. The propane tank needs to be kept at about 80 percent capacity to allow room for expansion, than lines and connectors need to be checked regularly for leaks. The air in the lines should be bled out before lighting, and the area around the burner kept free of dust and lint.

Absorption refrigerators don't necessarily require propane. Butane, kerosene, batteries, even refuse can be burned to provide the initial heat source. Industrial plants often use their incinerators as the heat source for their cooling system. Because electricity is not required, the propane refrigerator can continue to operate when the power goes out, making it a valuable asset in times of natural disaster, or a convenient one in situations or locations where electricity is not available, too expensive, or simply not wanted.

The propane refrigerators come in many sizes, from massive units that cool manufacturing facilities, to smaller ones tucked away in the rolling kitchens of recreational vehicles. Prices tend to be higher than electric refrigerators when it comes to start up. For instance, a basic 64-inch tall propane refrigerator with 7.9 cubic feet capacity costs approximately small electric “dorm” refrigerator can run from $1,500-2,500, where an electric one of comparable size costs about $400. Depending on where you live, the cost of running a propane fridge ranges from 50- 80 cents a day. Because the absorption refrigerator can use other heat sources, including natural gas, that operation cost can vary, and even compete with the $4-5 a month operating cost of an electric unit, especially if you live in an area where gas prices are low and electricity is high.  

But the lack of moving parts decreases the amount – and cost – of maintenance, and as technology improves, the propane water heaters are becoming more efficient, another factor that will increase their desirability and affordability. Besides offering the social maverick a way to live “off the grid” and still keep his food supply cold, the propane refrigerator offers a healthy cooling source for food when natural disasters strike and the grid itself goes down.