The technology that created the concept of evaporative coolers has been around for thousands of years and our modern-day fixed and portable devices still employ the same basics, just in a smaller container. Let’s explore a brief history of these economical cooling machines to see where they came from and how they have evolved into the compact, powerful comfort-makers we use today.
Before humankind enjoyed the luxury of refrigeration, they were forced to find workable solutions to reducing the terribly uncomfortable heat of summer in their dwellings and public buildings. Evaporative cooling came into use millennia ago in response to the great need that existed.
The Ancient State of Cool
In the earliest times, a porous earthenware vessel was used to cool water by evaporating it through its walls. We know this from frescoes dating back to around 2500 BC that depicts slaves fanning jars full of water to cool the rooms.
These early civilizations knew that a vessel could similarly be used to keep milk or butter fresh for longer by placing it in a bowl full of water and covering it with a wet cloth. The cloth could be kept wet by leaving a part of it dipped into the water so it remained soaked.
The windcatcher is a very early form of cooling by evaporation as used in Egypt and Persia several thousands of years ago. It took the form of wind shafts built into the roof that caught the breeze and channeled it down to subterranean water in what was called a “qanat.” As the breeze passed across the water, it evaporated and discharged cooled air up into the building.
20th Century Update
In the early part of the 20th century a number of US patents were filed for smaller, powered ventless evaporative coolers that made use of porous elements to soak up large volumes of water through which moving air could be pass through and bring about evaporation. The elements were made from excelsior (wood wool) pads for the material’s easily absorbent nature.
By 1945, a water reservoir was patented as an integral part of the device that used a float valve to control the water level. It used a mechanical pump to circulate water over the excelsior pads to keep them wet and a powerful centrifugal fan to force air through the pads for evaporation to occur and send the resulting chilled breeze into the building.
It is interesting to note that this early design and the materials used, despite modification are still in use today. The term “Swamp Cooler” may have come about because of the odor of algae that was produced by those early coolers.
Up to the Now
The development and use of passive evaporative cooling techniques, for example evaporative cooling towers in buildings have become widespread only in the last 30 years. The “Combination Refrigeration and Evaporative Cooling Air Conditioner” was developed by William H. Goettl in 1974 in Arizona. He noticed that while evaporative cooling technology worked better in dry climates and not in humidity, a combination unit was more effective.
Today, homeowners and businesses can purchase much smaller yet powerful portable evaporative coolers to cool buildings in arid climates along with larger fixed installations for larger buildings and warehouses. These devices provide users with a very economical alternative to energy hungry air conditioning to create thermal comfort and in very arid climates, a welcome humidifying effect.
These units, unlike portable air conditioners, do not need vent hose pipes to vent hot air to the outside of the building through a window since no hot air is produced by the cooling process. Larger units can be used outside with no fear of wasting energy to provide some welcome coolness on patios, paved terraces and porches during hot weather, making them highly versatile, portable and economical for anyone living in a hot, dry climate.