Absorption refrigerators use heat to drive the reaction that causes cooling. Recreational vehicle manufacturers often use these refrigerators in camping vehicles, in which propane fuels them. They provide cooling without using electricity.
Absorption refrigerators were popular in the United States prior to rural electrification. These models provided the cooling to prevent food spoilage as an alternative to an icebox. However, with the introduction of the vapor compression refrigerator and electricity to rural areas, residents replaced most absorption refrigerators.
Absorption refrigerators use ammonia as a refrigerant. Ammonia has a low boiling point and takes away heat as it changes from a liquid to a gas. Absorption refrigerators have no moving parts and use heat to change the ammonia back to a liquid. While propane is a common heat source, other potential sources include buildings that produce waste heat and solar refrigeration.
As of 2015, solar absorption refrigerators are offering help in areas where there is no electricity. In Mexico, they produce ice for storing the catch of anglers, keeping the fish fresh for shipping.
While solar absorption techniques also work for air conditioning, it requires an 86-square-foot solar reflector to produce as much air conditioning as a 6,000 British thermal unit per hour window air conditioner.