SciDAC Review 14 - NEWS: LCFs Tailor Energy Saving Efforts to Environment

News

Energy-Efficient HPC

LCFs Tailor Energy Saving Efforts to Environment

The Leadership Computing Facilities (LCFs) at Argonne and Oak Ridge are using some different approaches to energy efficiency, taking into account not only their different computing architectures, but also the different environmental conditions that come from their geographic locations.

HPC centers face unprecedented power demands. The biggest electricity cost associated with supercomputers is not operating the computer, but the cooling of the computer and computer room. So it is no surprise that both LCFs have focused on some aspect of cooling to improve their energy efficiency.

Argonne’s leadership system, an IBM Blue Gene/P known as Intrepid, is one of the fastest and most energy-efficient computers in the world—it uses about one-third as much electricity as other comparable supercomputers. But the folks at the Argonne Leadership Computing Facility (ALCF) are always looking for additional ways to save energy—and dollars. In the winter, the ALCF saves as much as $25,000 every month by leveraging the Chicago area’s cold climate to chill the water used to cool Intrepid for free. For extra energy efficiency, Argonne has focused on fine-tuning the chilled water system. By determining the warmest chilled water required for a given machine load, they can reduce the electrical load on the chillers and maximize the cooling period. It is still too early to calculate the exact energy savings, but the change is noticeable.

ORNL’s leadership system, a Cray XT known as Jaguar, is now the fastest computer in the world for open science with a maximum speed of 1.6 petaflop/s. With this great power comes great responsibility, especially when it comes to energy consumption. ORNL is located in an area of the country with high humidity, so keeping moisture out of the air is a high priority. Too much moisture in the air can lead to water condensation on equipment, while too little can cause static electricity to build up—both of which can be problematic for a room filled with expensive electronics. Both removing and adding moisture to the air use a lot of power, so keeping the humidity stable is a great tool for reducing energy consumption. The Oak Ridge computing room is sealed off from the rest of the building by a vapor barrier to reduce infiltration of humidity. The air pressure inside the computer room is kept slightly higher than the surrounding area so air will flow out without any outside air flowing in.

ORNL’s Computational Sciences Building (CSB) was among the first Leadership in Energy and Environmental Design (LEED)-certified computing facilities in the country, meaning that its design satisfies criteria used by the U.S. Green Building Council to measure the efficiency and sustainability of a building. A newly introduced Cray cooling system for Jaguar, dubbed ECOphlex, complements the chillers and the CSB’s efficiency. Using a common refrigerant and a series of heat exchangers, ECOphlex efficiently removes the heat generated by Jaguar to keep the computer room cool. The combination of air- and refrigerant-based cooling is much more efficient than traditional systems, which rely almost solely on air for temperature control. Without ECOphlex, the number of air-based units would not fit into the CSB’s computer room. This high-efficiency cooling system makes Jaguar possible.

Further Information
http://www.hpcwire.com/offthewire/Argonnes-Leadership-Computing-Facility-Working-to-Get-More-Science-Per-Watt-42986587.html

http://www.nccs.gov/2009/02/23/supercomputing-seeks-energy-savings/