The vast majority of data centers rely to some extent on water as part of their cooling system for keeping equipment from overheating. Some estimates have places water usage at a typical 15-megawatt data center at 360,000 gallons of water per day. A Microsoft data center facility in Northlake, Illinois, uses about eight million gallons per month—the equivalent of almost 270,000 gallons per day.

This enormous water usage is fueled in part by the need to use clean water in the cooling system; water fouled by contaminants can reduce the effectiveness of the system, in part by reducing the efficiency of the cooling system’s various components. Thus, some portion of the water is released as drainage (“blowdown”) in an attempt to remove dirt and other contaminants. Furthermore, the use of cooling towers also increases a data center’s water needs, as heat is removed from hot water waste through evaporation. These processes leave only a fraction of the water available for reuse in the system, hence the need for a continual (and large) input of additional water.

For large data centers with concomitantly large water needs, drought and water shortage is a chief concern. Currently, much of the western US is under dry to severe drought conditions; these conditions cover the majority of states such as Nevada, Arizona, and New Mexico. A severe drought also hit the southeast US as recently as 2006 and 2007, with states including Alabama, Florida, Georgia, Maryland, North Carolina, Tennessee, and Virginia all being hit hard. In addition, a general concern over the availability of water throughout the US has been growing in recent years, with the western US being an area of particular concern. Government regulation of water usage has increased accordingly, as have utility prices in many locations.

Data centers (particularly those that rely heavily on water as part of their cooling systems) must therefore be aware of this growing threat. Designers must carefully consider where to locate new data centers, since drought conditions or a general water shortage can lead to extensive interruption of uptime and even heat-related disaster in the case of acute water shortage.

For data centers that continue to rely on water and for those whose design includes water-based cooling, several possible approaches can increase efficiency of water use and even improve the operator company’s image with regard to its impact on the environment. Instead of expelling large amounts of water as blowdown, a data center can use water filtration to remove contaminants. A good filtration system can be of tremendous value in reducing waste water and in maintaining cooling efficiency. Also, instead of relying on public utilities for water, the data center could tap river or canal water, or even recycled (grey) water, if available. Recycled water is simply non-drinkable water that does not contain toxic substances or human waste. For instance, water authorities in San Antonio, Texas, provide recycled water to industry in an attempt to ameliorate pressure on the city’s drinking water supply.

Data centers can also rely in part on rain water, which can be collected and stored. Such a system, however, is limited by the size of the storage tank, and it can at best be used as a backup system, since rainfall is not always a reliable source (especially in drought-prone areas). Drilling a well is another option. This latter approach, however, can still produce a strain on the local aquifer, especially in areas where the aquifer is already depleted or otherwise threatened with overuse or pollution.

In addition to just use of water, disposal of hot water waste is another concern. Even if the waste water contains no other contaminants (which is unlikely), its excess heat can be a threat to aquatic life if it is simply dumped into rivers or lakes. Thus, in light of all these concerns, data center designers must balance a number of factors, just involving water, when selecting a location and appropriate cooling system.

Perhaps the most economical and environmentally friendly option (an option which is also gaining steam) is a simple temperature increase in the data center. An increasing number of data center operators are finding that cooler is not always better, and often, simply using outside air is a feasible alternative to high-tech cooling systems. Such an approach may be beginning to drive data center construction to cooler climates, where cooling by outside air becomes sufficient for a larger portion of the year. This trend also allows for a decreased reliance on water (and, accordingly, a decrease in hot water waste). As the water supply becomes tighter, the likelihood of data centers looking toward such unorthodox approaches increases.

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