Evaporative Cooling: An Ancient Technology Solution for a Timeless Problem
What Is Evaporative Cooling?
Remember the chill after swimming on a hot, dry day, then getting out of the water and feeling the wind hitting your wet skin? Or simply try dipping your finger in a glass of water, then blowing air across your finger and feeling the cool sensation as the water evaporates. That’s evaporative cooling.
Evaporative cooling units recreate this naturally occurring process and provide a constant flow of cool, refreshing air into a hot, uncomfortable environment. In the first half of the last century when signs advertising “refrigerated air” at restaurants and motels heralded the arrival of traditional air conditioning, evaporative coolers had already been in use for many years.
The early evaporative units were referred to as “swamp coolers” because of the high moisture content released into the air from the primitive technology. While today’s generation of evaporative coolers are engineered to achieve maximum cooling in exchange for minimal moisture content in the air, the term “swamp coolers” is still commonly used to describe any kind of evaporative cooler.
How Does It Work?
Evaporative cooling units, like those manufactured by Port-A-Cool, LLC, circulate water through saturated cooling media while drawing air across the surface of the saturated media. Hot air absorbs moisture from the media reducing the air temperature that is discharged from the unit.
The heart of an evaporative cooling system is the media, commonly called the “pad,” where the water evaporates and the air passing through the pads is cooled. Evaporative cooling pads, like Küül® pads from Port-A-Cool, LLC, are manufactured of fluted cellulose sheets that are glued together. These sheets are chemically impregnated with special compounds to prevent rot and ensure a long service life.
A special water distribution system spreads water over the surface of the pad, ensuring a uniform supply of water to keep the entire air contact surface thoroughly soaked. Fans create a negative pressure, causing air to be drawn through the pads. Evaporation results from contact between air and water. A control system operates the water pump and the fan distributes the cool air. The relative humidity is lowest in the afternoon when the temperature is at its highest. And the lower the humidity, the better the evaporative cooling effect. In other words, the cooling effect is best when you need it the most.
Evaporative Cooling vs. Traditional Air Conditioning
Evaporative coolers and central air conditioners both serve the same important purpose: keeping us cool. But these two systems operate very differently. Understanding the difference can help get the most out of any system and minimize energy.
Evaporative cooling systems work best when a small amount of outside air circulates into the space where the evaporative cooler is employed. This also introduces fresh air into the environment and reduces the risk of poor indoor air quality.
Central air conditioners, on the other hand, work by taking humidity out of the air. These systems produce cold, dry air and work best in an airtight environment. The major advantage of an evaporative cooler is that its operating costs are typically much less than those of a traditional air conditioner.
The initial equipment cost, depending on the size of the unit and the size of the area being cooled, can also be less than air conditioners, and there is no installation involved in a portable evaporative cooling unit. Along with lower unit costs and lower operating, evaporative cooling can also be a perfect, ozone-friendly alternative to traditional air conditioning.
Is It Good for the Environment?
Refrigerated cooling makes the air dry and uses chemicals which may harm the environment if released into the atmosphere. Evaporative cooling, however, is based on a totally natural process of air cooled by water, which means it won’t dry out the air, irritate your skin, throat or eyes, or affect the environment.
Evaporative cooling is one of the healthiest ways to cool because it replaces stale air with clean, fresh air many times an hour. Remember, you keep your doors and windows open. The air is never re-circulated which means smells and airborne germs are expelled.
Will it Save Me Money?
In addition to typically lower costs for equipment purchase, and requiring lower or no installation costs, evaporative cooling is, in most cases, also cheaper to operate than refrigerated cooling. Typically, the cost for water and electricity for a 36” portable unit is about $1.56 based on tests conducted by Port-A-Cool, LLC for 8 hours in standard lab conditions. Costs will vary depending on local utility cost and ambient climate conditions. (1)
So, the question is, can a cooling technique that's been around for centuries be effective in today's high tech society? Not only can it provide effective cooling solutions, evaporative cooling can do it without harming the environment with ozone depleting chemicals. That sounds like a smart choice for anyone.
1. Calculation is based on the following: standard lab conditions for temperature and humidity; based on 8 hours of continuous run time; 2007 national average electricity rate of $.0909 per kilowatt-hour; 2007 national average water cost of $6.52 per thousand gallons. Performance, electric rates and water rates will vary depending on the location of the unit. The water cost could be higher in dry climates, but the cooling effect will also increase with water consumption.