How Long Can Air Cooling Continue to Get the Job Done?

As virtualization and consolidation drive consumption down in terms of energy per square foot, those spaces are getting hotter due to the increased density of the components. At some point, it seems natural that the energy required to keep things cool will start to outweigh the savings you get from running fewer boxes.

There have always been alternatives to the computer room air-conditioning (CRAC) unit, but they have generally come with significant up-front costs and can become quite complex when applied to very large rooms. But the very fact that increased density reduces the physical scale of the data center is causing some to argue for a renewed look at these options.

One of them is, obviously, water-cooling. According to IBM fellow Roger Schmidt, air-cooling’s biggest energy weakness is the fan. The bigger the room, the more fans you need and the faster they need to spin to get the job done. Now that systems are consolidating, he tells Computerworld, we could take a page from the mainframe days and use water-based heat transfer plates directly on hardware.

Another approach is refrigerant cooling. Alcatel-Lucent says it has come up with a cost-effective solution called Phase-Change Cooling that involves piping a low-pressure coolant directly to equipment racks. The company says it can provide a lower OPEX than air-cooling and can be installed with minimal disruption to existing infrastructure.

Switching over to a new cooling architecture isn’t exactly the kind of job that most IT executives look forward to. So a key question in all this is: “How long do we have?”

That will depend on circumstances, of course. But according to HP’s Peter Gross, VP/GM of Critical Facilities Services, the average cabinet today draws between 4 and 5 kW. A fully optimized airflow can take you to a maximum of 25 kW, with a theoretical limit of maybe 30 kW. That’s why you see super-dense organizations, like Industrial Light & Magic, scrambling for a cooling solution even though, at upwards of 28 kW per rack, they see overall energy usage dropping 84 percent.

And to be sure, it’s not like development of air-cooled techniques and technology is on the way out. Oracle, for one, has come up with an approach called Containment for its Austin, Texas, facility. Designed as an alternative to hot-aisle/cold-aisle architectures, Containment draws hot air from the top of the rack and hustles it right back to the CRAC. Through this kind of isolation, the company can reduce the energy draw by adjusting airflow speed. Projected savings: $1.2 million per year.

So, to answer our initial question: yes, air-cooled technology is on the way out, but there’s still time to figure out how you’re going to address it.

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