Evaporative Coolers, sometimes called swamp coolers, is another way to cool air in warm climates with low humidity. It is the addition of water vapor into air, which causes a lowering of the temperature of the air.
An evaporative cooler (also swamp cooler, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from typical air conditioning systems which use vapor-compression or absorption refrigeration cycles. For direct evaporative cooling, the direct saturation efficiency, , measures in what extent the temperature of the air leaving the direct evaporative cooler is close to the wet-bulb temperature of the entering air. The cooling potential for evaporative cooling is dependent on the wet bulb depression, the difference between dry-bulb temperature and wet-bulb temperature. In arid climates, evaporative cooling can reduce energy consumption and total equipment for conditioning as an alternative to compressor-based cooling. For direct evaporative cooling, the direct saturation efficiency, , measures in what extent the temperature of the air leaving the direct evaporative cooler is close to the wet-bulb temperature of the entering air. Evaporative air conditioning uses evaporation to cool the air. In an evaporative cooler, such as Breezair, a pump circulates water from the reservoir on to a cooling pad, which in turn becomes very wet. A fan draws air from outside the unit through the moistened pad. As it passes through the pad the air is cooled by evaporation. When considering water evaporating into air, the wet-bulb temperature, as compared to the air's dry-bulb temperature, is a measure of the potential for evaporative cooling. The dry and wet bulb temperature can be used to calculate the relative humidity. The Science of Evaporative Cooling. Evaporative cooling is based on a physical phenomenon in which evaporation of a liquid (usually water) into surrounding air cools an object or a liquid in contact with it. As the liquid turns to a gas, the phase change absorbs heat. Technically, this is called the “latent heat of evaporation”.  Evaporative coolers lower the temperature of air using the principle of evaporative cooling, unlike typical air conditioning systems which use vapor-compression refrigeration or absorption refrigerator. Evaporative cooling is the addition of water vapor into air, which causes a lowering of the temperature of the air. For direct evaporative cooling, the direct saturation efficiency, , measures in what extent the temperature of the air leaving the direct evaporative cooler is close to the wet-bulb temperature of the entering air. Evaporative Coolers. Evaporative coolers, also called swamp coolers, are well suited for climates where the air is hot and humidity is low. They combine the natural cooling properties of water with a steady breeze to lower indoor temperatures. There are, however, several important factors to consider before making your selection Solve the cooling needs of your home or business with an Evaporative Cooler (also referred to as a Swamp Cooler). Coolers like the high performing Champion Cooler or uniquely designed Port-A-Cool, use evaporated water to lower a rooms temperature-a tremendous money saving solution.  Evaporative Coolers, sometimes called swamp coolers, is another way to cool air in warm climates with low humidity. | Photo courtesy of Public Domain Photos. In low-humidity areas, evaporating water into the air provides a natural and energy-efficient means of cooling. Evaporative coolers, also called swamp coolers, rely on this principle, cooling outdoor air by passing it over water-saturated pads, causing the water to evaporate into it. When operating an evaporative cooler, windows are opened part way to allow warm indoor air to escape as it is replaced by cooled air. Unlike central air conditioning systems that recirculate the same air, evaporative coolers provide a steady stream of fresh air into the house. In an evaporative cooler, such as Breezair, a pump circulates water from the reservoir on to a cooling pad, which in turn becomes very wet. A fan draws air from outside the unit through the moistened pad. As it passes through the pad the air is cooled by evaporation. 
https://en.wikipedia.org/wiki/Evaporative_cooler https://en.wikipedia.org/wiki/Evaporative_cooler http://www.breezair.com/us/why-evaporative/how-evaporative-works http://www.allianceforwaterefficiency.org/evap_cooling_intro.aspx https://en.wikipedia.org/wiki/Evaporative_cooler http://www.homedepot.com/c/finding_the_right_evaportive_cooler_for_your_home_HT_BG_AP http://www.homedepot.com/b/Heating-Venting-Cooling-Air-Conditioners-Coolers-Evaporative-Coolers/N-5yc1vZc4lr http://www.energy.gov/energysaver/evaporative-coolers http://www.breezair.com.au/why-evaporative/how-evaporative-works
what is evaporative cooling