Green Grid Unveils New Metrics for Data Center Carbon, Water Use

PORTLAND, OR — Companies undertaking a sustainability initiative of any kind follow a well trodden path, steadily expanding how broad and deep their measurements and improvements go.

It's a pattern that we've seen in the greenhouse gas reporting that the Carbon Disclosure Project regularly highlights, but the same holds true for green projects from supply chain greening to packaging redesign.

Now, the Green Grid, a consortium of technology companies dedicated to boosting data center energy efficiency around the world, has followed the same path: Last week, the group published a paper that expands its efficiency metrics to include the carbon output of a data center, as well as the water use of a data center.

"We see sustainability as a much broader issue than power," explained Christian Belady, Microsoft's Director of Hardware Architecture and a board member at the Green Grid, who edited the white paper. "How can we come up with some similar metric that will allow us to benchmark carbon intensity or efficiency in the data center, and then similarly with water?"

The results follow on the Green Grid's widely accepted Power Usage Effectiveness (PUE) formula for IT equipment energy efficiency: Take the total power entering a data center, and divide it by the amount of power used by IT equipment.

PUE has become the gold standard of data center energy efficiency since it was launched in early 2007. It is now something of a "miles per gallon" rating for data center energy efficiency. And while Belady describes PUE as "a fantastic metric," having more comprehensive ways of measuring the full impacts of a data center is getting more important as facilities get greener.

PUE is "the equivalent of buying a stock based solely on earnings per share," Belady said. "There are things you can do within your company to manipulate your earnings per share. At the end of the day there are other metrics [you should use] when you evaluate your stock."

When PUEs were high -- after measurement became popular, PUEs were averaging 3, while now the average PUE is between 2 and 2.5, depending on who you ask. And Belady said that when you start to move toward lower and lower PUEs -- 1 is the theoretical lowest -- data center owners and managers can end up raising their carbon emissions while they're lowering their PUEs.

That's where CUE comes in. The formula divides the total CO2 emissions of the total data center energy use by the energy used by IT equipment. The ideal CUE is zero, where a facility is 100 percent powered by renewable energy.

Using CUE, even in its currently fledgling state, can allow data center owners to detail the carbon impacts of potential changes to the data center -- for example, switching from chilled water to water coolers could affect the energy used by the data center, and if your energy supply is more highly carbon-intensive than your water supply, then choosing one over the other will improve your CUE while still lowering your PUE.

Water efficiency is critical in measuring data center efficiency, the Green Grid believes, and the next metric it will release after CUE is WUE -- Water Usage Effectiveness. Transporting water is one of the hidden energy hogs in the economy today. And that realization is what brought the Green Grid to develop WUE.

"Carbon and water are incredibly linked, there's a tremendous amount of energy associated with water delivery," explained Jack Pouchet, a Green Grid board member and Emerson Network Power's Director of Energy Initiatives. "If we can develop some metrics to evaluate, 'now, if PUE moved the needle, what was the overall impact on the environment?"

"Water is going to be another resource that's going to be harder and harder to come by in the future," Belady added. "So let's be proactive and drive our benchmarks in a way that will get people to reduce their resource use."

CUE and WUE will help companies proceed down that path of continual progress toward sustainable operations. Once a firm has a handle on its PUE and knows how much energy it uses in its data centers, it can then make sure it's operating in the lowest-carbon and most water-efficient ways possible.

Although when PUE as a metric was launched and began to be adopted, it had its share of critics complaining of various shortcomings, but in the years since it took off, it has come into its own, Belady said.

"At the end of the day, PUE has driven the right behaviors overall, but I look at the whole and not the individual, and the whole has driven to vast improvements. I think you're going to see the same with CUE and WUE."

Photo: Citi's LEED-certified Frankfurt data center, courtesy of Citi.