November • 2014
What Is a Water-Side Economizer?
A water-side economizer is a high-efficiency option for buildings that generate cooling through the use of water or air chillers. A traditional chiller works by extracting heat from liquids through a vapor-compression or refrigeration absorption cycle, then running that chilled liquid through a heat exchanger to provide cooling to heat-sensitive equipment or to building spaces. For facilities with air- or water-cooled chilled water plants, a water-side economizer is able to harness the power of cooler outdoor air temperatures during certain parts of the year to provide the same chilled water cooling benefit, but at a significant energy savings.
Facilities located in climates where the wet bulb temperature is below 55 degrees Fahrenheit for at least 3,000 hours annually ( which is virtually everywhere in the US except the edges of the southwest and select areas in the southeast.)
Locations with adequate physical space to retrofit the necessary controls, pipes, valves, and other parts to ensure a properly working economizer.
While water-side economizers can be cost-effectively retrofitted (unlike air-side economizers), it is still important to examine the specific economics of every potential site. Generally speaking, chilled water plant costs have been found to be reduced by up to 70% during water-side economizer operation, and California has found these energy-saving systems to show payback from one to four years. In every case, a value-engineering study should be performed to determine whether the energy savings and other benefits will outweigh the added costs.