Kyle Myers is director of environmental health, safety, and sustainability at CyrusOne.
Water has long been thought of as free or cheap, especially when compared to electricity. After all, 70 percent of the planet’s surface is covered in it. But only a fraction of that water is usable, and demand for it is increasing, making water scarcity a growing concern.
The United Nations’ 2019 world water development report shows that water scarcity is a problem that will only worsen in many parts of the world. Water usage worldwide has jumped by about 1 percent every year since the 1980s, and it’s expected to keep rising at that rate until 2050 – resulting in a 20 to 30 percent increase from today. Combined with a potential decrease in water supply due to climate disruption, the UN expects water demand to outpace supply by almost 40 percent as soon as 2030.
Data centers, which consume a huge amount of water, must start working to radically reduce water use for cooling now.
Supply Versus Demand
When we think of water demand, the obvious uses that come to mind might be human consumption and agriculture. But other industries also use water, often in large amounts, to make the products all around us. For example, it takes 700 gallons of water on average to grow the cotton for and assist in the fabrication of a basic shirt. Producing a pair of blue jeans might require 2,600 gallons, while manufacturing a car requires nearly 40,000 gallons.
Data centers also add substantially to the demand for potable water. IT equipment they house uses enormous amounts of energy, generating enormous amounts of heat, which data centers are designed to remove. The cooling process often involves evaporating water for cooling with cooling towers or evaporative coolers. When water is perceived as cheap and plentiful, this makes sense due to savings in electricity and the cost benefits. But in the face of growing water scarcity, we as an industry need to rethink our priorities in this area.
To address their environmental impact, data center operators have generally focused on Power Usage Effectiveness (PUE), a metric of energy efficiency. By shifting the cooling burden from electricity to water, facilities can improve their PUE, because water consumption is invisible to the calculation.
While this has helped data centers reduce energy consumption, quantifying a data center’s impact on the environment has to include its water use. Concentrating many servers inside a single hyperscale data center concentrates water consumption required to cool all those servers in a single watershed, exasperating water stress. Since many data centers operate in areas where water is scarce or may become scarce in the near future, Water Usage Effectiveness (WUE) becomes a critically important metric. Combined with PUE, WUE gives a full picture of a facility’s efficiency.
WUE is calculated as the ratio between water used at the data center and electricity delivered to the IT hardware. According to a US Department of Energy report, the WUE of an average data center is 1.8L per 1kWh. Data centers with a WUE of 0.2 L/kWh or less use less than one cup of water for every kilowatt-hour delivered to servers.
Site Selection Alone Isn’t the Answer
So, how can data center operators plan for sustainable operations in a water-scarce future?
While operating sustainably begins with good site selection, simply building data centers in regions with ample water supplies may not be a good long-term solution. Because of climate disruption, many regions are expected to see their water supply shrink ad their population increases. A region with ample water today may become water-stressed in 10 to 30 years.
Many data center operators have worked hard toward carbon-neutral facilities. To complete the transition to a sustainable future, we must also think about ways to make our facilities water-neutral. By doing so, we not only protect water supplies to meet growing scarcity but also increase the resilience of our data centers in the likely future scenario in which water becomes much more expensive and significantly less available.
Design a Better Cooling System
Since most of the water data centers consume is used for cooling, data centers should adopt alternatives to water-based cooling systems.
Data centers are already locked into water-consuming cooling can explore methods of using water more efficiently, such as increasing cycles of concentration in cooling towers, switching to chemical treatments to demineralize evaporating surfaces, or simply recommissioning to reduce cooling load.
Facilities that need to reduce water use further can retrofit to air-cooled chilling, such as compressor and condenser systems like CRAC (Computer Room Air Conditioning) units or centralized air-cooled chillers with an integrated compressor and condenser. With this technology, there is no evaporative cooling, no blowdown, no new water usage, and no release into the sewer system.
Of course, the most efficient method is to design the data center with waterless cooling from the beginning, which allows the whole cooling system to be balanced for air-cooled chilling rather than a retrofit. Moving forward, data centers should create water-free cooling and work with suppliers to optimize for air-cooled chilling.
When designing data centers for a sustainable future, the goal should be near-zero water consumption. While small amounts of water may still be used for humidification, facility maintenance, and sinks and toilets, these uses account for a fraction of the water consumed by water towers and evaporative cooling.
Many data center companies have done some outstanding work to improve sustainable practices for themselves and the industry as a whole. But we need to start taking the longer view of the challenges the industry and world will face in the coming years. Sea-level rise will happen. More extreme weather will come. And water scarcity will be a much bigger issue.
This would hold true even if the planet completely ceased emitting greenhouse gases tomorrow. Since the data centers built today will still be in operation 30 years from now, data center operators must prepare now for the coming changes or fail to anticipate one of the most critical components of a sustainable future.
Opinions expressed in the article above do not necessarily reflect the opinions of Data Center Knowledge and Informa.
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