A Multilayer Approach To Reducing Data Center Heat

The continued growth in server density and related heat issues is transforming how businesses approach data center cooling strategies. And within the next two years, the use of cooling systems that are directly attached to hot chips or built inside specialized server blades is expected to see significant growth.

Emerson Network Power said its Cooligy division is readying multiple approaches.

"We have got to get cooling closer to the heat source, and that is happening," Bob Bauer, group VP of Emerson and president of Liebert, said in the opening keynote of the AdaptiveXchange 2007 user and partner conference in Baltimore on Thursday. "The concern and work being done today is at the rack level, and not at the room level."

The next step is to move the cooling effort from the rack level to the server and device level. Cooligy is working with leading server manufacturers to integrate its close-proximity cooling techniques into "off-the-shelf" implementations that are expected to be commercially available by the end of next year, said Mark McMaster, VP of cooling technologies for Cooligy.

"We have delivered prototype systems that provide direct heat transformation, and can make servers between 37% and 40% more power efficient," McMaster said. "And the really nice aspect of the new designs is that the IT personnel don't really have to think about the cooling process once it is designed directly into the server itself."

Cooligy was acquired by Emerson/Liebert in 2005, and the unit has been working to commercialize its direct cooling technologies for the past two years. Cooligy's original cooling approach involves the spraying of chemically-treated water onto a cold plate that is placed directly on top of a processor or other heat source. The plate has 100 or more microchannels that direct coolant onto the chip's hot spots. To date, the approach has been used in about 50,000 workstations and high-end gaming platforms, McMaster said.

Over the past year, Cooligy has developed multiple approaches for moving chilled water or refrigerant on to blade servers which transfer heat loads from processors and memory modules. Coolant is pumped around the server blade using specialized pipes, and the individual blades themselves sit on top of preinstalled cold plates that can dramatically reduce total heat in the server, he said.

The key to gaining commercial traction for the direct-attached cooling systems will be the continued growth in high-density server installations, McMaster said. A typical rack today operates between 5 kilowatts and 7 kilowatts, while the "sweet spot" for direct-attached cooling technologies is around 10 kilowatts, which Cooligy believes will become increasingly prevalent by 2010.

Cooligy is among a handful of companies attempting to commercialize chip-level and direct-attached cooling. SprayCool has two commercial products that include a direct chip-cooling technology in which a module is attached to the surface of a hot chip and liquid is sprayed across a cold plate attached above the chip. SprayCool also has a server-level approach that sprays nonconductive fluid across an entire motherboard. Hewlett-Packard and IBM also have been working on chip-level cooling techniques.

A recent survey of about 100 businesses conducted by the Data Center's Users' Group announced at AdaptiveXchange found that 64% of respondents found heat density as the greatest challenge facing facilities and data center management, while 55% cited power density, and 39% said energy efficiency.