I’d like you to start thinking about how much water your data center uses a day, a month, and a year. Not just for personnel, but for the cooling towers, chiller plants and related IT process applications.
Why worry about water? Well, when more than 1 billion people do not have access to safe drinking water and fully one-third of the world’s population lives in “water stressed” countries, it is time for us to seriously rethink our use of water within our data centers. Water is a life necessity that we must carefully guard and protect in order to ensure our way of life.
As a first step, we need a way to measure water usage in terms of productivity. There has been much discussion around measuring energy usage and productivity in data centers. We need a similar discussion for water usage.
So consider for a moment the ideas of Power Usage Effectiveness, a.k.a. PUE, as defined by The Green Grid, as well as the general concept of productivity, where tangible outputs are related to a unit of input. Now let’s take that idea and tie it to water.
Many people feel that water is the next oil. Though that analogy is probably not the best, it helps us understand water’s value as a unit of measure of productivity. By relating output to water input, we can report, measure and improve data centers’ water productivity and water-use footprints.
It is time for the data center industry to formulate a Water Systems Productivity metric (WSP). Take useful work or even a proxy for useful work, such as the proposed Compute Units Per Second, and divide that by the amount of water used during the period. Water may be measured in units, with 1 unit equal to an acre-foot. However, gallons/liters is also acceptable.
This WSP metric would ideally be reported monthly with your other metrics. Once we start to measure and report water utilization, we will quickly realize that simply flowing more cooling water in order to “economize” may not always be the best answer. Now we will be able to have a meaningful tool to determine the ideal mix between dry-coolers, CW plants and evaporative cooling towers compared to the increased energy used with alternative solutions.
Let’s help the EPA, EU, Green Grid, and others drive a water productivity metric suitable for use within the data center community and a reporting system for rewarding Energy Star-type performance levels.
Jack Pouchet is director of energy initiatives for Emerson Network Power.