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December 18, 2008

Baby, It’s Cold Outside…Let’s Calculate Something

by John West

Argonne National Labs is part of the Department of Energy, so it’s not exactly surprising to learn that they are actively looking for ways to reduce energy use. But using Chicago’s cold winters to save $25,000 a month on cooling costs for the supers in their Leadership Computing Facility is, well, cool.

I talked briefly to Pete Beckman, the division director at Argonne’s Leadership Computing Facility (ALCF), about their overall focus on energy conservation. According to Beckman, it’s an effort that pervades the entire organization, “Across the organization, everyone has been told ‘let’s find ways to reduce power.'” In computing, that mandate gets executed in two ways.

The HPC staff in Beckman’s division are focused on practical ways to design datacenters, and supercomputers, to conserve energy. In the Mathematics and Computer Science division, researchers look at longer term solutions to more energy efficient computation. Among the initiatives Argonne has implemented already are thin clients in offices that don’t need full workstations, and software that automatically sleeps or turns off electronic and computer equipment after hours or during periods of non-use. Farther down the road? How about capturing the heat generated by the ALCF’s supers and doing something useful with it? As Beckman puts it: “no electricity should ever be wasted.”

The ALCF also made some big decisions about energy use, including their investment in IBM’s Blue Gene/P as the centerpiece of their high performance computation. Their largest system, Intrepid, is the production workhouse with nearly 164,000 cores and over 557 TFLOPS of peak performance. This system is complemented by another BG/P used primarily for testing and code development. Intrepid is number 5 on the latest TOP500 list, but for Beckman and his team, it is just as important that the system is very energy efficient — it ranks #16 on the Green500 List released in November. The systems ahead of it on that list are other Blue Gene/P systems or systems built out of IBM’s QS22 cell processor blades, another highly energy efficient option.

All told, the ALCF uses about a megawatt of power, a fraction of the amount used by less power-efficient computers at other centers. “Because the ALCF can effectively meet the demands of this world-class computer, the laboratory ends up saving taxpayers more than a million dollars a year,” said Paul Messina, director of science at the ALCF, in a statement.

Interesting stat? Left uncooled, the Blue Genes would heat up the machine room to 100 degrees Fahrenheit within ten minutes. So with all that heat, how do they save that extra $25,000 a month when it’s cold outside? The ALCF’s chilled water system uses cooling towers. According to Beckman, once the temperature falls to 35 degrees or below outside, the temperature in the chilled water system is maintained solely by the cooling towers. Although humidity control is still an issue, that’s free cooling.