Facilities are under continuous pressure to reduce costs and operate in a more environmentally responsible manner. In many locations, the reduced availability and increased cost of water are making water conservation a much more attractive goal than in the past. More and more facilities are being limited on how much water can be used; while there are alternatives to oil and gas, there is no substitute to water. Thus, the economic and environmental payback on reducing water usage is greater than ever.
Chillers, air conditioners, and other process equipment use cooling towers, which dissipate heat through evaporation to quickly cool water. Cooling towers, therefore, use significant amounts of water. Approximately 0.1 percent of the water circulated through a cooling tower is lost to evaporation for each degree the water is cooled. As a point of reference, a 400-ton water cooled chiller operating at a 30 percent load year-round requires almost 1.9 million gallons of makeup water just to replace evaporation losses. One potential source of nearly pure, cold water is from air handler cooling coils. These coils condense a large amount of water during normal operation; particularly in warm, humid climates. Rather than sending that water down the drain, why not use it?
Case studies have shown 10 to 40 percent of cooling tower water requirements can be met with air handler condensate in commercial buildings, universities, manufacturing plants, and similar facilities that operate in warm, humid climates. Most of the time, a gravity-fed tank, level controller, and pump are enough to do the job—though corrosion-resistant tanks and pipes are recommended because such pure water can be highly corrosive. Microbiological problems can also be avoided if an oxidizing biocide is added to the storage tank. Overall, the water collection system will have to be engineered to the existing system and environment.
Using water condensed from air for cooling towers reduces the amount of water simply going down the drain, improves the water quality used in the cooling tower, and improves the cooling tower’s overall efficiency. All of this saves money.
While each facility is different, the water savings and payback on using air handler condensate for cooling towers or closed system makeup water can be substantial. For example, a 164,000 sq. ft. office building in Texas was able to use air handler condensate for 17 percent of their cooling tower makeup requirements. That’s a significant amount of almost free water.
Written by: Pat Guccione