Is Water the Elephant in the Room for Data Center Efficiency?
As historic drought spreads in California, environmentalists are turning their attention towards potable water. While this isn’t an entirely new subject for conservation—we’re intimately familiar with water shortages here in Colorado and Wyoming—accelerating buzz and knowledge about climate change is making water shortages a hot topic, and data centers aren’t about to escape unscathed.
An investigative report in the Financial Times is shedding some light on the current water situation in industries around the world. The report includes a look at Google’s data centers, with Joe Kava, Google’s head of data center operations, quoted as saying that water is the “big elephant in the room” for data center companies.
Why Do Data Centers Need Water?
Data centers require vast amounts of water, mostly for cooling, even with the proliferation of advanced, highly efficient evaporative cooling systems. Despite many operators raising their operational temperatures and taking advantage of free cooling, with outside air filtered nearly directly onto the data floor, hundreds of thousands of gallons of water are needed to cool even small operations.
For example, Green House Data’s original facility uses highly efficient cooling units and is only 10,000 square feet (tiny compared to the 200,000 square foot facilities operated by large data center companies). In mid-summer, the WY1 facility uses 180,000 gallons of water each month.
Our new WY2 facility will be 35,000 square feet, launching with about 10,000 sq ft of operational data center space. We have four super efficient Emerson Liebert EVI indirect evaporative cooling units ready for opening day. On a 75F degree day, operating with just a 1MW load, which is pretty low, the units would evaporate 460 gallons an hour (115 gallons each).
Beyond cooling, the data center floor also must stay at an ideal humidity. Inefficiencies and water waste can therefore occur when one computer room is humidifying while another is dehumidifying.
That Seems Like a Lot of Water — Is It?
In a word, yes. That’s a lot of water. With a 200,000 square foot data center, we can assume up to 30,000,000 gallons of water a month, even if the cooling units are 20% more efficient than ours.
However, data centers aren’t the biggest culprits when you consider the industrial world. A power plant with an outdated once-through cooling system will suck in more than a million gallons per minute. For something a little closer to home, a garden hose running nonstop would use about 750 gallons in a month.
That doesn’t mean our industry should be ignoring our water usage, especially as the resource becomes more scarce. And we haven’t been, at least not entirely. The Green Grid put out its Water Usage Effectiveness measurement (WUE) back in 2011, recommending that operators start measuring and improving their water efficiency.
WUE = Annual Water Usage / IT Equipment Energy Usage. It is measured in liters/kilowatt-hour. They also include a more advanced equation that measures the water use in comparison to total site energy use, which can also be used to compare the water use inside the facility with the water used in the generation of said energy. Few data center operators are reporting on this metric.
Large operators like Google, Facebook, and Microsoft have also introduced efforts to increase efficiency through "penthouse" facility designs that include large free cooling plenums, cleaning and reusing grey water, cooling entire facilities with seawater, or even going so far as to overhaul treatment plants.
As liquid cooling technologies become more common, more efficient cooling will be within reach and with much less water use. However, the chemicals used for liquid cooling carry their own environmental burden. Will we see a Liquid Cooling Usage Efficiency metric? Probably. In the meantime, more and more data center operators are reporting on energy efficiency. As our neighboring states and countries struggle to keep their crops watered, it’s time we start considering and conserving our water, too.
Posted By: Joe Kozlowicz