It seems strange to think of burning gas to provide cooling, but in many cases it makes perfect sense.
An absorption chiller utilises gas to heat an ammonia solution within a sealed refrigeration circuit. Heating causes the solution to dilute, a process which absorbs further heat, thus providing the cooling effect. The principle has been used for many years in refrigerators, particularly in the USA, and gas absorption fridges remain popular today, especially with campers or in locations where there is no power. For a brief period, they became popular purchases for domestic kitchens but fell out of favour as electric fridges became cheaper and lighter and as gas fridges became understandably perceived as a potentially hazardous appliance for indoors.
Then there is the large industrial application, usually where there is an abundance of a “free” heat source, steam or hot water generated as a result of an industrial process which can then be used to drive a large absorption machine and provide cooling. Typically, these large absorption machines are 2,000 to 4,000 kW and use lithium bromide as a refrigerant instead of ammonia.
The third common type of application is for commercial comfort cooling where a small air source chiller uses ammonia to provide 18kW of cooling and the double effect can recover this heat for free hot water.