The condensate harvesting system at the FDA Lab in Laurel, MD captures condensate for reuse in cooling tower make-up. The system harvests 3-6 gallons per minute during peak cooling periods.
Though rainwater and stormwater harvesting typically come to mind when evaluating reusable water sources, condensate is an excellent source of water for collection and reuse.
As explained by Wahaso president John R. Bauer, “Cooling condensate is one of the least understood or appreciated sources for on-site water collection – yet in a typical commercial building, it can yield hundreds of thousands of gallons of water savings per year.” He continued, “Condensate is generally clean and a great source for water harvesting, yet most buildings discard it to the sewer drain- adding a burden to the municipal water treatment system. Unlike collecting greywater, which requires a lot of additional plumbing in a building, and is nearly impossible in a retrofit, condensate collection is usually very easy and inexpensive to do – even in an existing building.”
Condensate comes from the cooling coils of any air conditioning system, and in a large commercial building, a million gallons or more of condensate can be generated each cooling season. This quality source of harvestable water is typically redirected into the municipal stormwater system, wasting clean water that could have been harvested, treated, and reused. Harvesting cooling condensate is often a fairly simple operation, even in an existing building, and can be as simple as redirecting the wastewater line to the water harvesting system.
What is the value of a condensate harvesting system? When evaluating it in terms of the number of gallons of condensate that can be harvested each year, its value depends on the size of the building and the amount of cooling required each year. The following chart provides rough estimations based on 50,000 square foot buildings located in different cities throughout the country. Actual water savings will likely vary from the values listed here, but this chart is helpful in understanding the potential for a condensate harvesting system in different areas.
*In the chart above, the “Cooling Degree Day” (CDD) metric is the number of degrees that a day’s average temperature is above 65 degrees Fahrenheit. This is typically when people begin to use air conditioning to cool their buildings. The price of weather derivatives trading in the summer are based on an index made up of monthly cooling degree day values.
In many cases, the amount of condensate coming from a cooling system is directly proportional to the load on the system, meaning that the more water that is lost through evaporation, the more that is available as condensate for reuse. Also, not only can condensate be reused on its own to reduce cooling tower and air conditioning water use, but it is also an excellent way to increase the efficiency of a rainwater harvesting system. By providing a daily supply of harvested water even during periods of drought, utilizing condensate in addition to rainwater can help reduce the number of days that municipal water needs to be added to the system.
About the Writer: Emily Avellana is an Elmhurst College graduate with a degree in Marketing, and a Marketing Assistant at Wahaso.