Ways to cut data centre emissions by 98%

Most big data centres, the global backbone of the internet, could slash their greenhouse gas emissions by 88% by switching to efficient, off-the-shelf equipment and improving energy management, according to Stanford University experts. 

The carbon emissions generated by a search on Google or a post on Facebook are related mostly to three things: the computing efficiency of IT (information technology) data centre equipment, like servers, storage and network switches; the amount of electricity a data centre’s building uses for things other than computing, primarily cooling; and how much of the centre’s electricity comes from renewable or low-carbon sources.

Adding renewable power to the mix can help reduce a data centre’s overall emissions by 98% when combined with other strategies, but renewables are not the first choice for reducing emissions, the analysis shows.

“Of these three, improving the efficiency of the IT devices is overwhelmingly the most important,” said Jonathan Koomey, a co-author of the study, ‘Characteristics of Low-Carbon Data Centers’, published in Nature Climate Change.

It's about the processors

The processors in most server farms perform computations at just 3 to 5% of their maximum capacity. Server virtualisation, consolidation and better software can increase utilisation to more than 30%, and in some cases to as high as 80%, said Koomey, a research fellow at Stanford University’s Steyer-Taylor Center for Energy Policy and Finance, citing a recent account by Google.

Big, outward-facing companies whose business is, primarily, cloud computing have solved the sustainability problem for data centres. In addition to Google and Facebook, companies like Amazon, eBay and Expedia have instituted most or all of the changes, motivated by cost, publicity and pressure from environmental organisations.

“Electricity is a major cost for these companies, and in many of the countries where they operate, carbon emissions have a cost, or soon will,” said Koomey.

Other ways to avoid wasting electricity include faster computers that pay for themselves fairly quickly and using flash memory on the motherboard instead of hard disks.

Not following best practices are innumerable companies and institutions that are not primarily cloud-computing entities and are more inward-facing. Examples include the major media companies, airlines, government, universities and others supplying the vast data that feed the Googles and Expedias of the world.

IT equipment

“Pretty much every organisation whose main job is not computing has done a poor job of improving efficiency,” said Eric Masanet of Northwestern University’s McCormick School of Engineering and a co-author of the paper.

Department heads at such organisations typically want to keep control of their servers rather than centralise, which eliminates most potential optimisation. And the managers who order and operate the equipment are often not accountable for energy costs or efficiency - a major institutional barrier to sustainable computing.

“The utilities and IT departments have separate budgets, and neither operates with the goal of saving the company money overall,” said Koomey. “The IT people don’t care about putting in an efficient server, because they don’t pay the electric bill. Once you fix the institutional problems, then the company can move quickly, because the needed equipment is off the shelf and the energy management practices are well understood.”

This principal-agent problem applies elsewhere in energy, too. “Who designs and builds your cable box? The cable company. Who pays the electric bill? You do,” said Koomey. “So, you end up with a cat warmer on your shelf.”

Koomey noted that the computing efficiency problem is sometimes exaggerated. Data centres consume about 1.5% of the world’s electricity and are responsible for about 0.5% of carbon emissions. And the internet overall is reducing greenhouse gas emissions because it distributes goods digitally that once were delivered physically, like books, music, publications and mail.

Building efficiency

After IT equipment, the second major way to reduce greenhouse gas emissions associated with data centres is to improve the efficiency of the buildings that support them. A key measurement of efficiency is the ratio of electricity used to perform computations to the amount of power consumed for secondary support, like cooling and monitoring systems. Typically, that ratio is about 1 kWh for computing to 0.8 kWh for the facility.

“State-of-the-art data centres have reduced the ratio to about 1 to 0.1 kWh,” said study co-author Arman Shehabi of Lawrence Berkeley National Laboratory’s Environmental Energy Technologies Division. “They locate server farms in cool climates like the US Northwest, Sweden and Iceland. They purchase processors that are less sensitive to heat. And they use efficient cooling equipment and airflow management.”

Of the potential 88% reduction in greenhouse gas emissions, though, IT device efficiency accounts for about 80% and facility energy management for only about 8%. Once those two areas are maximised, sourcing electricity from renewables like wind and solar power, plus green handling of retired equipment, can get a typical data centre’s emissions down 98%.

Policymakers and environmental organisations, however, tend to focus on the third option - renewable energy, which the study finds to be a misplaced priority.

“For data centres, as for all uses of energy, efficiency is always the first thing to do. It’s cheapest and allows you to get more mileage out of your equipment,” said Northwestern’s Masanet.

“Most centres get their electricity from the local utility, rather than generate it themselves,” he said. “So, high-energy data centres that pay their utilities a premium for renewable power unnecessarily tie up low-carbon electrons that might otherwise be used to reduce emissions from other customers.”