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February 14, 2014

Immersion Cooling Floated as Green Energy Solution

Tiffany Trader
tsubame kfc image

At the same time as Moore’s Law progress is slowing down, the demand for processing data is at an all-time high. A full 90 percent of all the data in the world was created in the last two years, and datacenters are responsible for 2 percent of overall US electrical usage. Keeping all those warehouse-scale server farms and supercomputers at their optimal operating temperature is costly from an economic and an environmental perspective. The challenge has some big iron operators giving their computers a bath, as highlighted by a recent piece in The New York Times.

Japan has been especially motivated by energy concerns. The country has been operating with a reduced electricity supply ever since the March 2011 earthquake and tsunami and subsequent meltdown at the Fukushima Daiichi power plant. As a protective measure, the country limited the output of its other nuclear facilities, which curtailed electricity supplies.

With energy budgets constrained, organizations with major electricity needs had to get creative. Such was the case at the Tokyo Institute of Technology. The university administration had capped power supplies, but the institute required more supercomputing capacity. Thus the idea for the oil-cooled Tsubame KFC was born. The supercomputer employs a mineral oil-based cooling solution, called CarnotJet, developed by Austin, Texas-based Green Revolution Cooling. Last November Tsubame KFC was declared by the Green500 list as the most energy-efficient machine of its kind. The system is 50 percent more powerful than an older machine with the same energy footprint.

KFC CarnoJet Fluid-Submersion Rack image

Other companies involved in the space include Iceotope, a start-up based in Sheffield, England, which is promoting the use of liquid fluoroplastic, rather than oil. Another vendor, the Hong Kong-based Allied Control, used 3M’s “passive two-phase liquid immersion cooling system” for a 500kW datacenter that mines for Bitcoins.

Liquid cooling is not new. Compared to air, liquids are more efficient coolants because they are better thermal conductors and have a higher heat capacity. In fact, liquids are estimated to be about 4,000 times more effective at removing heat than air.

Iconic American supercomputer maker Cray used submersion liquid cooling back in the 1980s, but the approach never fully caught on because of cost concerns and also the coolants of that era were known ozone-depleters. A combination of air conditioning and pipe-based water cooling worked “good enough” and reduced the cost and complexity of the datacenter build.

Now dimensions have aligned to make immersive cooling attractive again. Supercomputer centers can easily spend tens of millions of dollars a year on energy bills. For the biggest corporate datacenters, the cost is even higher, running to hundreds of millions a year. In both cases, it’s not uncommon for 50 percent of that bill to go to energy and cooling costs.

At this time, immersive cooling has made it into more supercomputers than datacenters, according to Christiaan Best, chief executive of Green Revolution, who suggests that corporations are more risk averse than the academic crowd, which tend to be more open to experimentation.

“You can imagine, if we walk in and say, ‘Why don’t you take your data center and put it in oil,’ you have to have something pretty solid to point to,” Mr. Best said.

And yet Green Revolution’s method has been part of several datacenter deployments, including a United States Department of Defense facility. A one-year study of the system performed by Intel found that the servers suffered no ill effects, and power consumption dropped considerably.