Communications of the ACM
Lowering the Energy Overhead For Data
The U.S. Environmental Protection Agency has provided Energy Star certification to energy-efficient data centers since 2010.
Credit: Environmental Protection Agency
Most people shopping for a new computer recognize the Energy Star label that marks a device as especially energy-efficient. Yet once they power up their new device, they are much less aware of the energy that is used remotely on their behalf, as distant servers do the data-crunching that lets them surf the web, shop, and manage their finances. Much of this energy is not used directly for computation, but rather for air conditioning and other support in the buildings that house the servers that do the work. As one step to help reduce this unproductive energy overhead, the U.S. Environmental Protection Agency (EPA) in 2010 extended its Energy Star certification to include data centers.
"There’s no question that data centers are consuming a growing portion of the U.S. electricity supply," said Lauren Pitcher, EPA’s Communications Director for Energy Star Commercial Building and Industrial Plants. "The most recent data from the Department of Energy shows that data-center energy consumption doubled from the year 2000 to 2006, in 2006 reaching more than 60 billion kilowatt-hours per year, roughly 1.5% of all U.S. electricity consumption," Pitcher said. "At that time it was predicted to grow by 12% per year." For these reasons, both the EPA and the U.S. Department of Energy have paid special attention to this growing segment; for example, in their recent joint National Data Center Energy Efficiency Information Program.
To date, 45 data centers in the U.S. have been certified as Energy Star compliant, compared with more than 22,000 commercial buildings and plants of all other types that also have been certified. "From our perspective, the number is not low," said Pitcher. For one thing, the program is relatively recent. "We do expect the number to continue growing," she said. In addition, while only buildings that are primarily dedicated to data processing are eligible for certification, Pitcher said, "many data centers are housed in other buildings" which may be Energy Star certified, for example, as an office building, but will not show up in the data-center statistics.
To be Energy Star certified, a data center must also be in the top quarter of similar facilities (not just those applying for certification), as determined from the Commercial Buildings Energy Consumption Survey (CBECS) conducted by the U.S. Energy Information Administration. This criterion is similar to that for other buildings and plants, but differs from the requirements for products, which generally must meet specific performance goals. For example, Energy Star certification for an enterprise server requires that it be 30% more energy-efficient than standard servers. In both cases, however, the criteria get tougher over time, so companies must apply for periodic recertification.
The emphasis on measured energy consumption distinguishes the Energy Star certification of buildings from the well-known LEED (Leadership in Energy & Environmental Design) certification, sponsored by the private U.S. Green Building Council. The LEED process encompasses a wide range of design decisions that affect sustainability; not just energy, but also other resources and impacts. "Energy Star certification is the only way to really ensure superior energy performance," Pitcher said. "A lot of organizations that want a green building, but also want that building to be verified to perform well, will choose to pursue those two certifications jointly."
A key metric the Energy Star program uses specifically to compare data centers is Power Usage Effectiveness (PUE), introduced in 2007 by industry association The Green Grid. The PUE is essentially the ratio of the total energy used over a period of time to the energy consumed by the servers: the lower this ratio, the greater the fraction of energy consumption that is going to computational tasks. Although this metric actually penalizes more energy-efficient information technology, it encourages engineers to direct as much energy as possible to their computational goals, reducing overhead from air conditioning and other non-computational tasks. EPA provides guidelines for achieving this reduction.
In traditional installations, only about half of the energy goes to computation, said Matt Arisohn, an engineer with L&S Energy Services in New York State. Arisohn helped Internet host Turnkey Internet get Energy Star certification for its data center this year. He said it was relatively easy to get the necessary documentation, because in this small company the operator and the facilities manager "work hand in hand." Because they sell hosting services, the superior energy usage provides a direct advantage in marketing the company’s product, and the Energy Star certification is featured on their web page.
The rewards of certification are somewhat different for a big company that doesn’t directly market computational services, such as Intuit, best known for its Quicken and Turbotax financial software. Nonetheless, "Sustainability is a key part of our corporate culture, "says Bruce Eisele, Intuit's senior manager of data-center operations. "Intuit looks at its entire supply chain as part of its sustainability efforts," including the energy use of its data centers. The tools available through Energy Star help to quantify the success of those efforts. In particular, Energy Star’s Portfolio Manager lets companies benchmark their building’s performance against similar facilities. EPA’s Pitcher emphasizes that data entered into this tool is for the companies’ use, and is never available to the agency.
For a company that is serious about its environmental impact, the documentation needed for certification should be easy to get, says Dave Breland, facilities manager for Intuit’s Quincy, WA, data center, which earned Energy Star certification this year. "Any major data center is going to have online monitoring of the power systems," he said. "The information is readily available. We’re already doing these things."
Don Monroe is a science and technology writer based in Murray Hill, NJ.
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