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Tuesday, January 22, 2013

Make-Up Water in Data Centers: Increased Community Awareness

I noticed more discussions on data center water consumption in the Linkedin Groups that I belong to. Below is a snippet from the "DCD Group" on Linkedin with several members posting excellent discussions about water consciousness. (search "Water" to see the same chain if you belong to that group)

Water usage is an important OPEX component in data centers that have cooling towers or those that use evaporative cooling.  It is an essential component of the mechanical system  infrastructure as supply disruption could lead to site downtime. 

In 2007, I wrote an article in DCD's FOCUS Magazine about the topic. I've put a link to the paper here: Water Usage.  In 2008, I presented the  topic at the Fall AFCOM show to which there were references and discussions in other blogs  (see Google header); and in a step in the right direction, in 2011 the introduced the concept of Water Usage Effectiveness WUE (See white paper #35). 

In my case, I really stumbled upon the topic when I had to calculate the amount of make-up water in one of the projects.  After the shock subsided, I really wanted to make the community aware of the enormity of the consumption numbers.  The graph below is an excerpt from the paper; it shows the monthly peak water demand in a fictitious data center with a 5000 ton chiller plant. (This is equivalent to a 16-17 MW data center using a super efficient overall plant 0.85 kW/ton and a PUE of 1.25). The vertical axis equates to millions of gallons used per month: Quite a large number to ask of the local municipality.

So what can be done to reduce demand for make up water?  In the case of cooling towers, a graph below shows what happens when we raise the cycles of concentration (CoC) from the 3's to 8's for the 5000 ton plant. (Raising is good). You can see the drastic reduction in gallons of make up water per day during peak summer conditions. 

Lessons learned: Check water chemistry, raise CoC, automate blowdown, and invest in a newer cooling tower! I'll discuss evaporative cooling some other time. 

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