Your refrigerator is one of the largest consumers of energy in your home. In an average home, refrigeration burns 125 watts per hour1. You can, of course, take steps to reduce the amount of electricity your refrigerator uses—by shag carpeting it, for example. But why not replace your fridge with something entirely renewable? I mean, as Derrick Jensen points out in this video, no civilization that consumes resources is sustainable.
Stephen and Rebekah Hren, in their book The Carbon-Free Home: 36 Remodeling Projects to Help Kick the Fossil-Fuel Habit, provide this brief exploration into the use of an alternative refrigeration technology: Absorption Refrigerators.
An alternative method of refrigeration from the standard compressor fridge is what is known as a gas-absorption refrigerator. Typical fridges take heat out of the air in the fridge using a liquid with a very low boiling point, such as freon. By putting freon under pressure with the compressor, the fridge converts the gas into a liquid at a very cold temperature. As the liquid evaporates into a gas, it pulls heat out of the air in the fridge and freezer. This gas is then compressed again and the cycle starts over.
Absorption refrigerators also cool by evaporation, except they use ammonia trapped in a hydrogen environment. After the ammonia evaporates, drawing heat out of the air, it combines with the hydrogen to form water. Heat is then used to boil the ammonia off the water and return it to the hydrogen environment. Propane refrigerators, commonly found in recreational vehicles, boats, and some off-grid homes, operate on the same principles. The main difference in the ammonia versions is that the cycle is powered by a source of heat, such as solar power or waste heat, instead of an electric generator or battery.
Solar-powered gas-absorption refrigerators have been around for a quarter-century or so, most homemade by skilled tinkerers. A few have been mass-produced. Fridges of this type are often referred to as intermittent solar ammonia-water absorption cycle, or ISAAC, refrigerators. The idea is intriguing because the fridge has no moving parts and, theoretically, nothing to wear out, giving it a potential life span well beyond that of an electric compressor refrigerator. The main hurdle is the ammonia, which is poisonous if handled improperly and is therefore difficult to obtain and work with and is probably not suitable for residential use. It is possible to use other refrigerants. Energy Concepts is a company based in Maryland that makes solar-powered absorption refrigerators, although only for larger industrial customers.
If you have an innovative method for reducing the energy used for refrigeration in your home, we want to hear about it!