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Paving the way
Victor Avelar , director and senior research analyst at Schneider Electric ’ s Data Center Science Center , examines the impact of a new energy saving initiative .
By focusing on the trade-offs between mechanical load and electrical losses as a means to ensure energy efficiency , ASHRAE ’ s new energy standard for data centres is paving the way for industry best practices and a standards based approach to data centre design .
A recent UK news article publicised a long awaited energy standard for data centres by the American Society of Heating , Refrigerating and Air- Conditioning Engineers ( ASHRAE ). Classed as Standard number 90.4-2016 , it establishes the minimum energy efficiency requirements for data centres and includes recommendations on their design , construction , operation and maintenance as well as on the use of on site and off site renewable energy .
Crucially , the new standard does not require a Power Usage Effectiveness ( PUE ) rating to ensure compliance , although this was considered at an earlier stage of the drafting process . In this , the Society clearly recognises that energy management in data centres is a more complex problem than can be resolved with a single metric such as PUE , useful though that figure certainly is in guiding energy efficiency efforts . Recent research detailed in Schneider Electric ’ s White Paper 221 , ‘ The Unexpected Impact of Raising Data Centre Temeperatures ’, found that only a full understanding of the cooling and power infrastructure of the data centre and the operational requirements of the IT equipment itself , will yield optimum results in terms of efficiency and power consumption .
A joined up approach
Laying undue emphasis on a single metric such as PUE for efficiency , or on simple strategies such as allowing ambient temperatures to rise as a means of reducing overall power consumption , are insufficient in themselves . The theory supporting raised temperatures is that cooling equipment can operate in economy mode and will not need to be used as frequently , resulting in a lower energy requirement .
However , experience shows that the results of this strategy have been mixed .
PUE has the advantage of simplicity , in that it represents efficiency as a single metric allowing data centre operators to measure the effectiveness of the power and cooling systems over time . However , it is quite limited as it measures only the relative difference between power consumed on IT equipment and the energy consumed on IT and infrastructure combined .
Therefore , lowering your PUE rating does not necessarily mean that your overall energy consumption has been reduced . In fact , PUE is only a measure of how efficient the physical infrastructure systems are in providing power to the IT load . It says nothing about the total energy being consumed by the data centre and is more indicative
of a ratio , not a value that indicates a quantity of energy .
In essence , your PUE can improve ( ie . power and cooling systems are more efficient ) but your energy use throughout the data centre might be the same or higher . But greater collaboration with IT equipment manufacturers is necessary to gain a better understanding of how the operational IT load and how its reliability is impacted at high temperatures .
By allowing greater latitude to data centre designers to build their facilities to their specific requirements and by taking into account the differing load and cooling strategies that must be deployed in differing climactic regions , ASHRAE ’ s new 90.4 standard will encourage innovation in the development of efficient data centres , resulting in more reliable , efficient and cost effective IT services .
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