Evaporative cooling basically evaporates water into the air to create a cooling effect. A simple example of this principle at work is putting a wet cloth in front of an open window and cooling the air as it passes through the cloth. An evaporative system for cooling is quite an effective way to cool your home. This is an excellent system that provides you with a cool and comfortable environment through a network of outlets located in the ceiling.
Economically speaking, the initial cost and operation of an evaporative cooling system is far less than a traditional one. Basically, the two essential mechanical parts you need to deal with in the evaporative system are the water pump and the fan motor. Both can be easily repaired when needed. Controls usually consist of on-off switches, timers, and thermostats. Operating costs are about 1/3 of that of conventional air-conditioning.
Evaporative cooling is more affordable for industries. Discomfort in the work place leads to low production and absent employees, not to mention health issues. The constant re-circulation of air inside an industrial building may lead to what is usually referred to as “Sick Building Syndrome,” when stale and contaminated air is shared by everyone in the environment. An evaporative cooler changes the air every 1-3 minutes, instead of re-circulating it.
Overusing chlorofluorocarbons (CFC’s) is the one major cause of air pollution. Ordinary air-conditioners produce these CFC’s into the atmosphere, evaporative cooler system does not. It uses 100% fresh air and cleans the cooled air it produces.
There are indirect and direct evaporative cooling systems. The indirect evaporative cooler is more expensive and uses a heat exchanger which keeps humidity lower. On the other hand, a direct evaporative cooler blows air through a water-soaked pad. The air is filtered and cooled as it passes through the pad. Direct evaporative coolers run about $700 – $1000, installed.
Usually, an evaporative cooler is installed on the roof of a building, or sometimes it is mounted on the ground in a shaded area. Service and maintenance should be done regularly. If the system has not been used for awhile, drip pans need to be cleaned to prevent mold caused by stagnant water. If natural fiber pads are used, they should be replaced every year.
Further information can be found here: https://en.wikipedia.org/wiki/Evaporative_cooler