One of the things that makes evaporative coolers so great for cooling outdoor spaces and events is that they take advantage of the natural air to create cooling. They draw the hot air through the evaporative media to create the cool air that gets distributed where you need it most. Does this mean you need an open-air source for them to work?
Technically, no, but the effectiveness of evaporative cooling diminishes if you don’t have one. Here’s why.
Evaporative coolers work by using the energy in the air to evaporate water. Hot air has a lot more energy than cold air. This means that hot air will evaporate more water and get cooler than cold air.
If you don’t have an open-air source for your evaporative cooler, you’ll be drawing already-cooled air through the cooler, and each pass will be less effective than the previous pass.
The amount of water that evaporates from the media also depends on how dry the air is. Drier air leads to more evaporation, which means more cooling.
Each time air passes through the evaporative cooler, it also picks up water from the evaporative media, becoming more humid. If you’re taking in the previously humidified air that’s already gone through the evaporative cooler, less water will evaporate, and you’ll get less cooling.
Evaporative coolers can function well in many of the same applications as air conditioning, such as home cooling. However, where they really excel are applications where there’s a good supply of open-air and no good option for drawing in already-cooled air.
For an air conditioner to effectively cool a space, it has to cool the entire space, making multiple passes over the already-cooled air to make the whole space cool. On the other hand, an evaporative cooler doesn’t need to cool the entire space. It can effectively drop the temperature with a single pass over the evaporative media to effectively spot-cool the working area in a large space like an aircraft hangar.
Air conditioners often have trouble cooling a drafty space like a barn. All the cooled air keeps escaping, so the air conditioner is never able to re-cool the air to achieve the full cooling effect. But an evaporative cooler doesn’t need to re-cool the air – it just takes in new air from outside, so it doesn’t matter if some of the cooled air escapes, making it a great cooling solution for agricultural applications.
The same is true of outdoor events. An outdoor air conditioner will never cool all the air. In fact, it will put more heat into the air than it takes out. But with its one-pass cooling, an evaporative cooler can create a dramatically cooler area outdoors even if you can’t trap the cooled air.
Spaces like shops and hangars must open their doors regularly to let cars and/or planes in and out. This means that air conditioners have a hard time keeping these spaces cool. An evaporative cooler can rapidly cool these areas after the doors are opened and even keep them cool when the doors remain open.
In many events centers, guests will undermine your efforts to keep the space cool. Post all the signs you want, but people will still open the doors, either carelessly or in a misguided attempt to “help” cooling. An evaporative cooler makes sense for these spaces because it doesn’t matter as much if you lose some of the cooled air.
Whenever you have a location or event that is either partly or completely open to the air, it can be impractical and expensive to use an air conditioner. On the other hand, evaporative coolers are highly effective and efficient under these conditions.