CFD Software

The Debate about Liquid Cooled Data Centers

I’ve been remiss in not posting for a couple of weeks, so I’m trying to get back in the saddle. I’ve been working on other things that have taken up a fair bit of time. One is a web seminar on heatsinks – Heatsink 201 – Even More about Heat Sinks which follows on from Alexandra Francois-Saint-Cyr’s very successful Heat Sink 101 web seminar.

Back in March I posted about IBM’s work on liquid cooling to take Moore’s Law to 2025. As a side note I observed that, one of the main benefits of liquid cooling in a data center is that the high grade waste heat generated can be used for heating purposes. This changes both the economics of deploying a liquid cooling solution and the environmental impact. The reason this is so important is that data centers are one of the fastest growing consumers of energy.

Last week Google posted about this issue on its Public Policy Blog in response to ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers) adding data centers to their building efficiency standard, 90.1. Google’s concern is that the ASHRAE standard is too prescriptive, stating that the building should use economizers (which bring in ambient cooling air from outside for cooling). The term ‘economizer’ reflects the fact that using natural ventilation is more energy efficient than using mechanical ventilation systems, particularly those that incorporate chillers, which are commonplace in data centers. As Google note, this can in some cases work very well, but to quote a British expression, its horses for courses.

Google argue that an efficiency-based approach should be taken with aggressive targets for non-computing power consumption. To me this makes sense. In terms of liquid cooling, the target should take into account useful waste heat that can be used for heating homes and offices in the locality. Although this is harder to measure, I believe it’s important to take a holistic approach to measuring and reducing the ‘non-useful’ energy consumption of data centers.

The leading thinkers in the industry are on the right track in pursuing Power Usage Effectiveness. Simply dumping the heat generated by tens of thousands (and in a few cases hundreds of thousands) of servers to the ambient air, albeit with an energy-efficient ventilation system, is not the way to go. Hopefully common sense will prevail.

That’s it for now, back to work on my forthcoming Heatsink 201 web seminar.

Dr. J, Hampton Court