At the recent AFCOM Data Center World Conference, David Pickut, the VP of IBX operations engineering at Equinix, said that air-side and water-side economizers can take advantage of natural outside temperatures to cool data centers instead of relying entirely on chillers that suck up utility power. The company has been installing them for the past two years and plans to continue to do so where possible.
Lately, economizers have gotten attention in the industry, as data centers try to make their facilities more energy efficient, which can translate into savings on power costs in the near term and delay the multimillion-dollar capital costs of building new server rooms. The United Parcel Service of America uses water-side economizers to get about five months of free cooling every year in its Atlanta data center. In its report to Congress last year, the federal Environmental Protection Agency recommended air-side and water-side economizers as a way for data centers to reduce their power consumption.
According to Pickut, companies should consider economizers wherever there is an opportunity to do so. In one example Pickut cited, a Silicon Valley-area data center has the potential to use an air-side economizer – which filters in mild outside air to cool the data center -- essentially for the entire year. That means the data center needs only about 11 days of mechanical refrigeration to supplement the outside air cooling.The limits of economizers
That's not to say, of course, that economizers are the solution for every data center cooling problem.
Indeed, Pickut acknowledged the limitations of economizers, though. Air-side economizers work best in mild conditions; Pickut gave Silicon Valley and Reading, England, as examples. Air-side economizers do OK in more variable environments, such as Chicago and Washington, D.C., but they're not worth it in locations that are hot year-round, such as Miami or New Orleans, he said.
In addition, he said the filtration systems that bring outside air into a facility can create hassles.
"These things are inherently problematic," he said, where the controls for filtration systems can be complex, and "poor quality and poor maintenance can cause quick degradation."
Meanwhile, water-side economizers offer another way for data centers to take advantage of the cooler outside air to cool IT equipment. Water-side economizers use cold –typically nighttime – air to cool an outside water tower and use that chilled water for the air conditioners inside the data center instead of mechanically chilled water, which requires energy costs.
Again, Pickut said there are limitations. In contrast to air-side economizers, which work best in mild weather like in San Francisco, Pickut said water-side economizers are best in climates with a cool fall and spring and cold winter, such as Chicago or New York (although tower freezing can be a problem in severe cold). They work a little less well in mild conditions, and then not as much in hot, humid environments. But in optimal environments – cold weather in the right location – data centers could save 78% in energy costs cooling their facilities.
The bottom line: Facility managers have to make sure that economizers work for them. "You have to monitor operations and savings, and if savings are not being achieved, you have to find out why," Pickut said.
Todd Kise, the facilities manager at Columbus, Ohio-based Grange Insurance, said that economizers aren't always feasible. When he joined Grange Insurance, the had already built its company data center, so adding economizers was far more difficult.
"You've got to make that decision right at the beginning," he said. "The problem with retrofitting is if the building is completely done, to go in and change things could be disrupting to the environment."
Kise added that justifying the cost of retrofitting an existing facility, especially if it's one that is fairly new, can be a difficult proposition to sell to company executives.
"It's all about ROI," Kise said with a smile.