There are many different kinds of air conditioning available on the market today. Evaporative air conditioning is a system that cools air by harnessing the natural forces of evaporation and has earned the nickname "swamp coolers" due to the moisture they create. This low-cost, low-tech alternative to traditional air conditioning is not very effective in humid areas but can be used with great effect in dry regions. The western and mountain states of the United States are a good example of a suitable climate for evaporative air conditioning and cities like Denver, Salt Lake City, Tucson, and Fresno have embraced the technology. Southern Australia is also well-suited to this system of air conditioning.

As far back as Ancient Rome, humans have been harnessing the power of evaporation to keep them homes cooler by covering their windows with damp cloth. This blocked the outside dust as well as heat from entering the home. By using the latent heat in the air to evaporate the water, the air is cooled as it travels inside. Evaporative cooling has been used for millennia. Porous earthenware vessels were used to cool water by harnessing their ability to allow evaporation through their walls and milk and butter were kept fresh for as long as possibly by storing them in vessels surrounded by water and covered with a wet cloth that dips into the water.

Evaporative air conditioning requires much less energy than traditional air conditioning but does require a source of water. For this reason they may not be recommended in drought areas. Simpler and less expensive, these units do not require the special high-amperage circuits which are common to air conditioning units.

Essentially a large fan with water moistened pads placed in front of the flowing air, this type of air conditioning relies on the dry outside air to operate effectively. By pulling outside air into the home and blowing it through the damp pads, the fan circulates fresh air through the home as well as adding humidity. The pads are usually made of wood shavings or another material that will absorb and hold water while resisting mildew and need to be replaced every season or two for maximum effectiveness.

The effectiveness of this system greatly depends on the temperature and humidity of the air going on and therefore works best at the hottest times of day. Water levels inside the unit are controlled by a float pump (similar to the one in your toilet) and the system can use between 3 and 15 gallons of water per day depending on usage and outdoor temperatures.

Benefits

• Uses as much as 75% less energy than air conditioning
• Simpler to operate and install
• Less expensive and low tech
• No special outlet required
• Fresh air constantly entering home

Drawbacks

• Will not work in humid climates
• Requires a water source to operate