Once Through Cooling

Cooling water demands have been estimated to account for up to 70 percent of water use in commercial, industrial, and institutional buildings. Many large cooling systems discharge water after it has passed through a single cycle (called once-through cooling) - these types of cooling systems can be significantly water intensive. Once-through cooling can be a wasteful practice because water is used only one time before being discharged to the wastewater system. Typical equipment types that may use once-through cooling include ice makers, refrigeration compressors, vacuum pumps, air compressors, condensers, hydraulic equipment, rectifiers, degreasers, X-ray processors, welders, and occasionally even air conditioners.

Some areas of the country prohibit the use of once-through cooling practices.

Facility managers looking for opportunities to cut water use should minimize once through cooling wherever possible. Converting to a "closed loop" system that reuses water, or to an air-cooled system can reduce water use by a significant amount -- on the order of 20 to 95 percent. Options to eliminate once-through cooling are typically very cost effective and can include the following measures:

• Connect equipment to a recirculating cooling system. Installation of a chiller or cooling tower can be an economical alternative.
• Consider replacing water-cooled equipment with air-cooled equipment. One example of such an alternative is switching from a water-cooled to an air-cooled ice making machine.
• Reuse once-through cooling water for other facility water requirements such as rinsing, washing, and landscape irrigation. One of the most prominent uses of reused water is for irrigation of golf courses and other large commercial landscapes.
• Look for opportunities in existing plants to utilize excess cooling capacity.