PUE gains validity as a data centre energy measurement

By Christian Bertolini*
Tuesday, 31 August, 2010



PUE is currently the only energy-efficiency rating available for industry, with PUEs closest to 1 representing highly efficient centres. The average PUE for industries in Australia is between 1.6 and 1.7, with leading-edge data centres acheiveing a PUE of 1.2.

Is PUE the right metric?

While PUE is the industry standard, it is not necessarily an effective metric or the right approach for the future. The current PUE system has failed to specify terms of the energy input to energy output ratio, thus opening the measuring tool to interpretations which have led to questionable results. Different portions of either the input or output can be moved to create unbalanced results.

Today, the market talks about data centres with PUEs that are more relevant to sci-fi stories than reality. The end result is what could be a good tool is prone to misuse for marketing and sales purposes. The hype around PUE means that it is now used as an objective rather than a tool to benchmark and understand where the room for improvement is.

How many times have we heard companies and CIOs say that their next data centre will have a PUE of X? How many times have project briefs asked for specific PUEs even before the project design details are assessed and validated?

Unfortunately, in a society hungry for instant gratification, this is what has become of a simple energy-efficiency metric. We need to look again at overall efficiency and determine the best way to improve standards rather than seek to achieve marketing led PUE targets. The focus needs to be on business objectives and efficiency targets rather than the PUE.

Beyond PUE: improving the efficiency rating system

The government’s target PUE of 1.9 is reasonable to aim for but is a far cry from an aggressive energy-efficiency target.

APC by Schneider Electric has worked with countless organisations to help them decrease their energy footprints. This has included work with hosting and co-location provider Maxnet, who we partnered with to achieve a PUE of 1.2, while our partnership with Canberra Data Centre achieved a PUE of 1.35. These are industry-leading results but our engagement on reducing environmental impacts and increasing efficiencies does not stop at PUE.

Is there more the government should and could be doing and are there other measures outside of PUE that the government, and industry as a whole, should be considering?

The answer is yes. To achieve real carbon and energy reductions there are alternative approaches being developed. In order to achieve any energy-efficiency objective a strong and networked energy monitoring system must be in place.

This is not just about recording the power bills, reading the current consumption from a manual clamp meter or installing a few power meters and calling it an energy-monitoring policy. It should be about intelligently deploying energy-monitoring systems that can report to a central repository of information where data can be analysed and shaped into meaningful reports or instantaneous interpretation.

Still today, there is a strange resistance to proper analytical measurement of how much energy goes into the data centre and how much of that is converted into computational capacity. This mindset has to change if we are to see any movement on this issue.

2015 energy management strategies

The future will see the energy market become more similar to the shares market where energy can be purchased and sold throughout the day and night at different prices. Such a future will need exceptional monitoring and energy management systems, far and above those currently in use.

So what can we expect from a 2015 data centre energy strategy? First of all, proper, smart monitoring. The solutions have been available for many years at very accessible prices - it is only a matter of putting them into practice.

The New South Wales Government is taking a lead in this area through its NABERs for Data Centres initiative. This program is working to establish a standardised benchmarking energy rating for data centres, similar to the green star rating system for buildings.

Another approach being developed is an energy conversion efficiency rating which provides a more quantifiable and specific energy performance rating than the current PUE system.

The PUE, like any other metric, is only as good as the use we make of it. Whether we call it PUE or Energy Conversion Efficiency, the industry needs to agree on a single procedure to monitor and report on energy consumption in the data centre, as free from error as possible.

The 2015 data centre will be more energy centric than today and industry must follow business and political requirements and provide smart systems to make the best use of energy in real time. Once a proper energy monitoring and management system is in place, the next step is to look at what design and engineering decisions can provide a constant improvement of energy efficiency.

*Christian Bertolini is the Chief Technology Officer of APC by Schneider Electric.

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