For people who live in a dry climate, an evaporative cooler is an effective, energy efficient alternative to an air conditioner. An evaporative cooler, sometimes called a “swamp cooler,” works on a simple principle.
A small motor pumps water from the bottom to the top of the cooler. The water then runs down the insides, and is absorbed by filter pads. Another small motor works a fan. This fan brings air into the evaporative cooler for the outside, then through the device, and then out into the warm room. What causes the cooling is the evaporation of water as the hot dry air goes through it.