Because data centers are responsible for one to two percent of the world's electricity use, they are the target of considerable research into how to reduce their carbon emissions. However, assessing the true carbon intensity of data centers has not been easy. There are numerous metrics in circulation, as well as claims about their energy and carbon emissions performance. Climate policies with financial incentives for reducing carbon intensity can help push data centers towards greater energy efficiency, but policymakers do not have a clear way to discern which metrics are useful for defining a low-carbon data center.
In a recent Perspective in the journal Nature Climate Change, Eric Masanet, Arman Shehabi and Jonathan Koomey propose that energy models of data centers provide "actionable guidance" to policymakers, and they present the results of one such model that offers a typical U.S. data center carbon footprint, and how much its footprint is reduced through different carbon management strategies.
Masanet is with Northwestern University, McCormick School of Engineering, Shehabi, the Environmental Energy Technologies Division of Lawrence Berkeley National Laboratory, and Koomey, Stanford University's Steyer-Taylor Center for Energy Policy and Finance.
Their research suggests that the carbon footprint reduction resulting from managing the lifecycle of IT devices (through lifetime extension and recycling initiatives) is dwarfed by that of best practice energy efficiency in the data center. "Efficient IT device operation is the most important feature to reinforce through policy incentives," says Masanet.
Best practice efficiency reduces the emissions from data centers during their operation. It includes such strategies as using the most energy-efficient equipment available, as well as server virtualization and application consolidation, which together lead to higher utilization of each server's computing capacity.
Low-carbon electricity, for example, from renewable power sources, also contributes substantially to reducing carbon footprint. Therefore where possible, they should be located close to access to grids that provide low-carbon electricity.
However, their research suggests that while using renewable electricity helps reduce data center carbon emissions, this strategy must be coupled with best practice efficiency. "The critical lesson from this analysis is that existing data centers should maximize IT-device efficiency. "These devices turn over quickly so this strategy can deliver rapid improvements," says Koomey.
"Data centers that are inefficient would use far more low-carbon electricity than technically required and end up squandering scarce renewable power that could otherwise be reducing the emissions of more energy-efficient customers elsewhere," says Shehabi."
Data centers should also be located in areas with cool outside air. The "free cooling" of appropriate climate zones reduces the need for mechanical cooling, and electricity use.
For more of their recommendations, see:
Masanet, Eric, Arman Shehabi, and Jonathan Koomey. 2013. "Characteristics of Low-Carbon Data Centers." Nature Climate Change. vol. 3, no. 7. July. pp. 627-630. [Article Preview and Supplementary Information]