WATER HARVESTING AND EVAPORATIVE COOLING SYSTEMS
Many commercial buildings are cooled with systems using evaporative towers and cooling water systems that can be tremendous consumers of potable water. For example, a 200,000 square foot building with 1,000 tons of cooling can consume 2-3 million gallons of potable water in one season! In warmer climates, the consumption can even be greater. Obviously, these heavy consumers need to be evaluated and addressed in a holistic approach to water sustainability in commercial buildings.
USING HARVESTED WATER FOR COOLING TOWERS
Because of their high consumption of water during a cooling season, evaporative cooling towers and cooling water systems are an excellent use for water harvested from rainwater or greywater. In colder climes that experience frozen precipitation during the winter months, the demand by cooling towers coincides with the warmer months when rainwater is available for harvesting.
The high demand by cooling towers can easily outpace rooftop rainfall – even from buildings with large roof areas. In these cases, we recommend adding additional sources of harvested water – especially parking lot stormwater. Underground caverns can effectively store millions of gallons of water while greatly reducing stormwater run-off from the property. Water from the harvesting system storage tank is directed to the cooling tower “make-up” inlet. Water chemistry is critical to cooling tower efficiency and may require additional filtration or additives before adding to make-up. To see a case study on one our systems that used cooling condensate for cooling tower make-up, click here.
CONSERVING WATER IN COOLING TOWERS
All cooling towers go through a process called “blow down” that is meant to flush minerals from the cooling water to maintain their ability to exchange heat efficiently. In a typical system, this “blow down” water consumes about 25% of total water used by the systems – which can total a million gallons or more during the cooling season! In addition to wasting water, sulfuric acid and other hazardous chemicals are used to maintain mineral solubility – and the chemicals and waste are then dumped into the municipal water system.
Innovative new systems are able to remove scale and other calcium deposits without harmful chemicals. At the same time, the amount of blow down water required is dramatically less – saving 25-50% of water that would have otherwise been wasted. The result is lower water costs, less chemical costs and less discharge into municipal sewer systems
COOLING SYSTEMS AS A WATER HARVESTING SOURCE
An overlooked source for harvested water is the condensate that comes from cooling coils of any air conditioning system. Condensate is an excellent source of clean water that can be directed back into the cooling tower system or other uses with minimal treatment. The amount of condensate coming from a cooling system is directly proportional to the load on the system, meaning that the more water being lost through evaporation, the more is available from the condensate. A cooling system in a commercial building can generate a million gallons or more of condensate each cooling season. This quality source of harvestable water is usually wasted into the municipal sewer or stormwater system.
Harvesting condensate water is usually a fairly simple operation – even in an existing building — and can be as simple as redirecting the waste line or adding a discharge pit and pump to the water harvesting system.
Wahaso is happy to talk with you about your cooling system and the opportunities for saving water or applying harvested water. Please Contact Us.