ALL THINGS GREEN
After adiabatics T
he data centre industry’s rapid expansion in recent years is well documented and shows no sign of abating. However, with great power comes responsibility. A recent report suggests that by 2025, data centres will consume one-fifth of all the electricity in the world. Stats like this have served to bring the sector under the spotlight and it has come under increasing pressure in recent years to reduce its carbon footprint and operate more efficiently. The primary source of energy consumption in most data centres is cooling. This energy usage mainly comes from large industrial equipment such as pumps, chillers and cooling towers, which are used to regulate data centre temperature. It is important for the air conditioning industry to take its energy efficiency responsibilities seriously. Measures like Power Usage Effectiveness
(PUE) have helped steer the industry down a greener path and technological strides have been made in order to increase efficiencies, but PUE does not tell the whole story. The use of water in data centres is increasingly coming under the microscope.
Global water crisis
We live on a blue planet, yet only 1% of the world’s water is useable. Growing populations, intensive urbanisation and industrialisation are putting strains on this 1% like never before. In 2015 the World Economic Forum in Davos listed ‘water crises’ for the first time as the world’s leading threat and this is not a crisis limited to developing countries. As an industry we cannot ignore this.
Air-side optimisation Around 10 years ago, the optimisation of air
Stuart Kay of Airedale explains how to achieve low energy cooling in high density data centres while minimising water usage.
temperatures was introduced as the latest way for data centres to increase efficiencies. At the time, many data centres ran at 20°C to 22°C. However, as server technology advanced, data centres were able to run at higher temperatures which reduced the cooling requirement and provided more opportunity to utilise free-cooling. Airedale International pioneered this with the introduction of chillers specifically designed to take advantage of the free-cooling opportunity, resulting in a lower cost of ownership for operators. Adiabiatic cooling systems
In recent years, air-side optimisation has been built on with the introduction of adiabatic cooling systems. This technique incorporates both evaporation and air cooling into a single system. The evaporation of water, usually in the form of a mist or spray, is used to pre-cool the ambient air to within a few degrees of the wet bulb, allowing cooler and more efficient operation.
The use of spray or mist means water use is significantly lower than with more traditional evaporative systems, but a conservative water usage estimate for a modern data centre, employing an adiabatic cooling system would still be 500,000 litres/1MW/annum. As data centres grow larger, this becomes a real concern, particularly in regions where water shortages have been identified as a threat. To put the figures in context, a typical 50MW data centre employing adiabatic cooling would use approximately 25,000,000 litres per year, about the same as 152 UK houses. The water usage itself is not even the whole story. This water still has to be stored and treated, which increases capital costs and as with any mechanical equipment exposed
32 July 2019
www.acr-news.com
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