The number of data centers in the United States continues to grow in response to the enormous amount of digital information stored and streamed. The massive computer power within these data centers generates heat, making efficient cooling a key building system requirement. Evaporative cooling towers are an integral part of many data center cooling systems.
Recently some have questioned the use of cooling towers, citing water scarcity to bolster their arguments. But a thorough examination of water use for local onsite cooling towers compared to water use to generate power at regional fossil fuel power plants reveals surprising results.
Data Center Cooling Options
There are multiple ways to cool data centers, depending on the size, computer capacity that must be cooled, regional energy costs and the data load and density. Popular options include:
- Water-cooled chiller plant – includes chiller system, pumps, cooling tower and plate/frame heat exchanger in series with the chiller
- Air-cooled chiller plant – includes chiller system and pumps
- Direct evaporative cooling – without mechanical refrigeration, also referred to as “swamp cooling”
- Adiabatic cooling – air-cooled system assisted by water-cooled system during peak conditions
To attract customers, data center operators weigh the options and look for systems that reduce operating costs and environmental impact. They pay close attention to power use effectiveness (PUE), defined as the ratio of the total amount of energy used by a data center to the energy delivered to the computing equipment. A PUE of 1 means the heat rejection power equals the power used for the computing equipment.
Data center operators are also concerned about water use effectiveness (WUE). Cooling towers evaporate water, but the impact depends on location. According to Tim Chiddix, PE, VP Mechanical Engineering at Swanson Rink, a leader in the design of data center facility infrastructure, data centers can range from a few hundred square feet to several hundred thousand square feet and no cooling technology works well for all regions, client criteria and applications. “Each and every facility must be analyzed to determine the approach that best meets the needs of the customer and takes advantage of energy and water savings opportunities of the particular region.”
Swanson Rink specifies equipment as part of its data center practice and frequently combines cooling towers with mechanical chillers for efficient cooling.