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Time to update cooling techniques

Published: 2 January 2012 - Joe Bush

Data centres are one of the biggest consumers of energy. With cooling technology typically representing 45% of overall data centre running costs, plus sustained energy price rises, it’s clear that expensive air conditioning technologies are becoming unsustainable. Jason Preston, director of 2bm, investigates

Some current cooling technologies and methodologies have been in use for the past 15 years, and as such have become outdated. Therefore, replacing these systems can yield significant cost reductions.

Soaring energy costs are having an impact on all UK businesses. Yet while organisations are embarking upon a number of initiatives to drive down costs, one of the major opportunities to drive down power consumption is being overlooked.

It is estimated that two percent of the power consumption of the US is due to data centres, and a key contributor to that consumption is cooling. This is because traditional air conditioning technologies are incredibly power hungry. From the inappropriate use of office style air conditioning units in smaller data centres, to the use of direct expansion compressors to drive the air conditioning, too many organisations are over spending on data centre cooling.

Indeed, in the past decade the only major change to data centre cooling policies has been the adoption of aisle containment, enclosing either the hot or cold aisle to improve air conditioning efficiency. And even this methodology has yet to be adopted by the majority of data centres.

There is so much more that can be done. Indeed, walk into any legacy data centre environment in the UK and it is 95% certain that some changes could be made to reduce energy consumption - from the use of new air conditioning technology to more intelligent air flow.

Free air

The most compelling technology, and one that has a phenomenal payback, is fresh air evaporative cooling. Used extensively in the US and Australia, this direct free cooling (DFC) technology combines external air with the mechanically generated hot air from the data centre to create the right temperature - typically around 21°C. This mode works up to external temperatures of circa 19°C - once the temperature exceeds that figure the system automatically switches to evaporative cooling, passing the fresh air over water saturated pads, in addition to mixing it with the hot air from the data centre, to achieve the desired temperature. The result is a technology that enables companies to choose to use fresh air even when ambient temperatures reach as high as 38°C.

It is of note that much of the existing refrigeration plant that is at present relied on to cool data centres has been designed to operate in ambient temperatures of up to 32°C. Over this temperature legacy air conditioning equipment failures rise dramatically and performance is compromised markedly.

Critically a DFC system can ensure that air temperature and humidity will fall within the ASHREA (American Society of Heating, Refrigeration and Air-Conditioning Engineers), Class 1 Guidelines of up to 27°C inlet temperatures for servers and allowable range for relative humidity of up to 80% RH - safeguarding the effective running of the data centre.

The payback on this technology is also compelling, with most organisations able to save between 80-90% of cooling running costs and attaining a return on investment (ROI) within one or two years. A further incentive is that DFC qualifies for the Enhanced Capital Allowance (ECA), which allows companies to claim the entire investment back against tax in the first year, making the financial argument even greater.

Of course, not every data centre can exploit DFC due to limitations of the site design or location. However, there are alternatives - organisations with an existing data centre located in the middle of the office and limited access to the outside air can use indirect free cooling technology. This approach uses traditional styles of air cooling systems, such as DX gas or water, but exploits outdoor plant to use the outside air temperature to cool a secondary medium which is in turn used to cool the data centre.

The drop in running costs is not quite as dramatic as DFC but at around a 40-60% reduction on cooling costs, the argument is still convincing.

Quantifiable energy reduction

There is a huge data centre industry effort being placed on driving down power usage efficiency (PUE) ratios to attain the most efficient and cost effective data centre environment. Cooling is a fundamental component of that usage model, and organisations really need to consider every opportunity for improving performance and removing unnecessary expenditure.

The ideal set-up for any data centre would be to use the most up to date technology, combining DFC with aisle containment and optimised air flow management. However, in today’s economic environment, capital expenditure is severely constrained. There are considerable benefits to be gained from considering any one of these options in isolation - and the cost can be minimal, especially when looking at just using air flow management techniques.

If the organisation is using a raised access floor in the data centre, how is the air being distributed within the floor void? Is there an option to use different types of floor grill, introduce baffles within the floor void to move the air in different directions or remove hot spots, or simply relocate cabinets within the room? Air management techniques can be inexpensive to implement and deliver clear reductions in energy consumption.

New Model

Energy costs appear to be heading in one direction - upwards. And every business is considering opportunities to reduce power consumption and cap fast escalating operational expenditure. There is simply no way any data centre can continue operating with air cooling models that have been in place over a decade - it is not sustainable, either environmentally or economically. It is time to reconsider the way data centre cooling is delivered and explore opportunities for reducing the primary source of energy consumption within the business.



 
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