Evaporative Coolers

One of the most economical ways to stay cool on hot summer days is to use an evaporative cooler to blast cold air around the room without using much electricity in the process. This type of cooling device, often also referred to as a swamp cooler has many advantages over traditional air conditioning which makes it highly desirable as a form of indoor climate control. It also has some disadvantages that you should know about.

In this part of the website, I'll be covering a lot of details about the way in which evaporative cooling works, the economical and environmental advantages of using this solution as well as its disadvantages in certain situations. This article is the main overview of this great way to beat the heat and acts as a focus for the several more detailed and specific informational articles on the topic.

What is Evaporative Cooling?

honeywell co25mm portable evaporative coolerThe best way to get an appreciation of exactly what evaporative cooling actually is, go outside on a hot sunny day, stand in the heat for a few minutes, then look down at one of your arms or hands. You should see a nice film of perspiration forming on your skin, which is the body's natural way of regulating its temperature.

If there is no breeze, as can happen on those hot, still days of summer, try blowing as hard as you can on your arm or hand. Feel how cool that short breeze is! That's made possible because the moisture on your skin (the perspiration) is being evaporated by the breeze (when you blew) and it causes the skin to experience a drop in temperature as the skin's heat is quickly reduced as the perspiration evaporates and the resulting water vapour dissipates into the atmosphere.

Another easy experiment you can do to really show this at work is to take a glass of iced water and blow into it with your face right above it so you can feel the breeze coming back off the surface of the water. It feels cold, doesn't it?

Temperature Reduction by Evaporation

Evaporative coolers work by the same principle as a breeze acting on the glass of water or the sweat on your skin.

These coolers have a water reservoir tank to hold water that is soaked up into a porous membrane that is stretched across the back of the unit. A simple fan draws room temperature air into the back of the unit, through the wet membrane where the water is evaporated and blasts the now chilled air out the front of the unit into the room.

The result is a dramatic reduction on the air temperature in the room!

Economical Climate Control

One of the big advantages of this kind of device is that it only uses a very small amount of electricity to run the fan, which is the only power drawing mechanical part of the device. Typically, swamp coolers only need 100-200 watts of electricity to run.

It's not until you compare this energy consumption to that of a comparable air conditioning device, which typically uses around 2,000 watts to achieve the same degree of temperature reduction that you see the very obvious saving in both energy and the cost of that energy in dollar terms.

The saving in energy has a knock-on effect in reduced power generation meaning less fuel is needed, which results in less pollution being produced as fewer natural resources are expended. At the same time, the cost savings can be appreciable as more people switch to this low energy solution.

The Disadvantages

There is one major drawback to making use of evaporation to create cooler air. The air has to be relatively "dry" or low in moisture to begin with or the process will suffer reduced effectiveness. Here's why.

In order to evaporate moisture, there must first be sufficient capacity in the air to accept the additional water vapour. Under normal circumstances, this isn't a problem and the process works perfectly.

Unfortunately, when the humidity of the air is very high, it cannot easily accept more water vapour. As a result, the chilling effect is reduced the higher the level of humidity gets.

Perhaps you have experienced this phenomenon yourself if you have visited a very hot and humid place. Your body will naturally perspire but the moisture will not evaporate into the moisture laden air. As a result you will not experience any coolness even when there is a breeze lowing or you are sitting right in front of a powerful fan.

For this reason, swamp coolers are not recommended for areas that have high relative humidity levels, such as places that are near large expanses of water (lakes, rivers, even the ocean), or places that have high rainfall or low cloud cover for most or all of the time. You can easily check with local weather stations (or their websites) for the local humidity levels.

For all other areas that enjoy lower humidity levels (approximately 60% or lower), you can happily use evaporating coolers to stay cool for less cost instead of the more expensive to run air conditioning.

More Information

To find out more about this type of hot weather climate control, I have included several informational and product review articles covering more details and areas not fully explored in this overview article. You can see the list of titles below to get more information on the particular area that interests you:

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