Power & Cooling
Adiabatic cooling for data centres
By increasing the ASHRAE limits, consultants have an opportunity to explore alternative design solutions focusing on reducing the air conditioning energy consumption of the data centre, writes Iain McNeil of CAREL UK.
Data centres require continuous air conditioning to address high internal heat loads and maintain indoor temperatures within recommended operating levels for computers. Traditional mechanical cooling methods using chillers, computer
room air conditioners (CRAC) or air handlers can consume typically 33 – 40% of facilities total power consumption. Data centre efficiency is typically referred to by PUE (Power Usage Effectiveness) which is simply the ratio of overall power consumption
of the data centre vs. IT power consumption. Not long ago data centres had a typical PUE of 2.0 meaning only 50% of their energy was used in IT. Recent changes in design recommendations such as ASHRAE TC 9.9, Environmental guidelines for datacom equipment – expanding the recommended environmental envelope, and continued product development has led to efficient designs of PUE 1.5 and below.
Looking at ASHRAE guidelines, we can see above how the envelope has expanded allowing designers to consider new design solutions. The red area was ASHRAE’s previous recommended range (2004).
Fig 1 February/March 2011
The orange area is the revised recommended range where IT manufacturers test their equipment to ensure reliability of operation. The green area is ASHRAE’s allowable range, which defines the area to which the environment can support IT equipment, however this area is marked as reduced reliability of equipment and is recommended no more than a few days per year.
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