An earlier form of air cooling, the windcatcher, was used in ancient Egypt and Persia thousands of years ago in the form of wind shafts on the roof. They caught the wind, passed it over subterranean water in a qanat and discharged the cooled air into the building. Nowadays Iranians have changed the windcatcher into an evaporative cooler (Coolere Âbi) and use it widely.
Schematic diagram of an ancient Iranian windcatcher and qanat, used for evaporative cooling of buildings
A traditional air cooler in Mirzapur, Uttar Pradesh, India
The evaporative cooler was the subject of numerous US patents in the 20th century; many of these, starting in 1906, suggested or assumed the use of excelsior (wood wool) pads as the elements to bring a large volume of water in contact with moving air to allow evaporation to occur. A typical design, as shown in a 1945 patent, includes a water reservoir (usually with level controlled by a float valve), a pump to circulate water over the excelsior pads and a centrifugal fan to draw air through the pads and into the house. This design and this material remain dominant in evaporative coolers in the American Southwest, where they are also used to increase humidity. In the United States, the use of the term swamp cooler may be due to the odor of algae produced by early units.
Externally mounted evaporative cooling devices (car coolers) were used in some automobiles to cool interior air—often as aftermarket accessories—until modern vapor-compression air conditioning became widely available.
Passive evaporative cooling techniques in buildings, such as evaporative cooling towers, have only been developed and studied in the last 30 years. In 1974, William H. Goettl invented the "Combination Refrigeration and Evaporative Cooling Air Conditioner" in Arizona after noticing that evaporative cooling technology works better in arid climates rather than humidity but that a combination unit would be more effective. In 1986, two researchers at the University of Arizona, Tucson, W. Cunningham and T. Thompson, constructed the first passive evaporative cooling tower in Tucson, AZ. This performance data from this experimental facility became the foundation of today’s evaporative cooling tower design guidelines, developed by Baruch Givoni.