What is a Swamp Cooler?
Swamp coolers are household cooling devices that basically do the same thing as an air conditioner: they cool you down! The difference is how they work, and most importantly where they work. They work by evaporating cool water into the ambient air. Won't that make the air more humid? Of course! That's why they only work well in the southwestern part of the country: areas where people suffer from dry heat.
How Swamp Coolers Work
Basic swamp cooler system
Swamp coolers are formally referred to as evaporative coolers since they evaporate cool water into hot, dry air. They look like an outside air conditioning unit commonly found throughout the country, but instead of pushing a refrigerant through a condenser and coil, they use a fan to blow the hot, dry air across cool water. A centrifugal fan and a water pump are the primary components of a swamp cooler. Hot air is brought into the cooler by the fan, and the water pump brings in cool water which is placed onto pads (kind of like sponges). The heat from the hot air then evaporates the water from the pads, and the newly cooled air then flows through the venting system in the house .
Since hot air can hold more moisture than cold air, the hot air evaporates the cool water and holds its moisture content, providing cool air in the house with the use of higher humidity levels. An air conditioner, on the other hand, works by dehumidifying the air in a house, relieving the home owners of the hot, sticky air. To fully understand this concept, April Holladay provides this simple test:
"Wet the back of your hand — then blow on it. Your skin surface feels cooler. That's evaporative cooling." 
This is a simple test that yields simple results but makes understanding swamp coolers much easier.
Who Benefits from Swamp Coolers?
Although swamp coolers have a simple design and are environmentally friendly, they are not meant for everyone. This is due to where you live. As mentioned previously, swamp coolers work by adding humidity into the air. So they need to be placed in areas where there is very little humidity to begin with, otherwise they will not be able to cool the air. In Pittsburgh, PA, for instance, you would suffer if you were trying to cool your home with a swamp cooler! Pittsburgh already has such a high humidity content, so the outside air already has high moisture content. Therefore, if you tried to blow hot air across cool water during the summer months, you would not be able to evaporate much of the water. Your home could not cool by more than a few degrees. In contrast, if you lived in Phoenix, AZ, you would benefit greatly from a swamp cooler because the air is so dry. By blowing this hot, dry air across cool water, you would be able to pick up the moisture and cool your house down by as much as 25 oF.
The map below shows where the hot and dry climate is located throughout the United States. The red area shows where the best choice would be for using a swamp cooler.
Other Uses for Evaporative Coolers
Even though we live in a high humidity area, we still make use for evaporative coolers in the form of cooling towers. Cooling towers are used in power plants to cool down the fuel before and after it goes through the condenser. They are usually built along a reservoir and make use of naturally flowing water to cool the fuel. The fuel enters the cooling tower and is cooled by a combination of air and water. The water is the primary coolant, but the air plays the most vital role. It evaporates the hot fluid and takes out some of the heat.
Advantages and Disadvantages of Swamp Coolers
- Less expensive than normal air conditioning
- Provides cooling in very hot and dry weather with little impact on the environment
- Ventilation of continuous air provides a constant source of fresh air
- Limited to locations with hot, dry air
- Adds moisture - Causes condensation which may damage electrical components
- Adverse health defects from high humidity
We researched swamp coolers and learned many interesting facts with help from the following sources:
Page created by M. Blisard, R. Booth, E. Kristek