The National Security Agency’s Utah data center using much less water than the U.S. spy agency pays for most likely indicates that the facility is not running at full capacity and that it is taking advantage of economization, also known as “free cooling,” a data center engineering expert told Data Center Knowledge.
Mark Monroe, CTO at DLB Associates, an engineering firm that designs data centers among many other types of buildings, said water consumption levels the site was reportedly designed for were probably for worst-case days – or “design days” in engineering lingo – and that the pattern of monthly water usage was normal for a data center.
Data center engineers “calculate the usage on the hottest hour of the hottest day, with the data center fully loaded, and size the system for that peak,” Monroe wrote in an email. “Average usage could be 20-30 percent of that peak, and that still requires the data center to be fully loaded.”
The NSA’s monthly water bills, released recently by the City of Bluffdale, which sells water to the data center, revealed that the agency was paying for a set amount of water every month but never came close to consuming the amount it had contracted for, The Salt Lake Tribune reported. The paper pushed reluctant Bluffdale officials to release the documents until the state’s record committee ordered the city to do so in March.
The Tribune published the data center’s monthly water consumption and payment figures from January 2012 through February 2014 earlier this week, drawing attention to the fact that the NSA is paying the city for a lot more water than it actually consumes.
The agency paid about $32,000 for water in January and in February of this year, but consumed about 4.9 million gallons and 2.8 million gallons during those two months, respectively. Bluffdale can deliver up to 1.7 million gallons a day to the facility, The Tribune reported, citing city council meeting minutes.
Its monthly water bill from July 2013 through December was about $28,000. During that period, however, there were months when the facility consumed 6.2 million gallons, about 2.6 million gallons and 3.8 million gallons of water.
Monroe also said the wide fluctuations in water consumption from month to month indicate use of evaporative cooling and economization. “Water will only be used when the air [temperature] is too high for direct air or dry cooler use,” he wrote in an email.
“Since air [temperatures] in Utah are cool most of the year, they would only be required to use water evaporation in the summer months. Even in summer, air [temperatures] are cool enough at night to allow several hours of no-water cooling each night.”