The water cycle
Toby Hunt discusses ways to reduce the environmental impact of data centres using water for cooling without compromising continued operations.
At present, the UK has more square metres of data centres than any of the major European countries – 840,000 m2 compared with next-in-line Germany at 509,000 m2. This figure is set to rise as Edge computing, which brings data storage closer to a location where it is needed, becomes more widespread, with data centres now popping up in more regional areas, moving away from the major city outskirts.
More data centres mean more energy and water usage, particularly when it comes to keeping these hot environments cool. Currently responsible for the consumption of around three per cent of the UK’s energy, the carbon footprint of the data centre sector is set to overtake those of other large electricity and gas using business customers - keeping these hives of infrastructure running may seem at odds with the drive to sustainability.
Overheating is the data centres’ worst enemy, leading to expensive repairs, breakdown and potentially catastrophic downtime so it might seem that sustainability is low down on the list. Operational integrity and improved environmental credentials are not mutually exclusive, however. Whether relying on cooling towers or air, there are ways in which energy and water wastage can be reduced.
Overall, water is a better heat transfer medium than air, therefore many of the larger data centres rely on cooling towers to keep their contents suitably chilled. While effective, this approach uses vast quantities of water. For example, in 2009, Amazon admitted to using 360,000 gallons of water per day to cool their 15 megawatt data centre. If water can be recovered from processes, as well as reusing rainwater, in our experience 60% 70% of water can be recycled, saving a considerable amount of wastage and potentially harmful chemicals.
And the larger the system, the better the returns - amounting to £2 per cubic metre of water recovered. If we use the Amazon data centre as an example, 360,000 gallons equates to over 1636 cubic metres so if 60% of this water was saved, that would be over 981 cubic metres, saving nearly £2,000 per day in water charges. The ROI on a water recycling system can be recouped in less than 6 months, installations can cost between £30,000 to £90,000 dependent on size of plant required.
Data centre water recycling systems use a combination of media filtration, ion exchange and membrane filtration to remove all suspended solids and bacteria. A high percentage of dissolved solids are also removed and all bacteria, algae and viruses are discharged, ensuring recycled water is safe to use – in some cases cleaner than when it came out of the mains in the first place.
In data centres relying on air cooling and supporting closed circuit water systems, water wastage is not so much of an issue - although there are still savings to be made. The main focus here is energy savings, which can be achieved by operational efficiency, in turn leading to reduced risk of downtime – a win, win scenario.
Air monitoring is a relatively sophisticated process, using sensors to monitor conditions in order to provide real-time data on temperature, humidity and air quality, but in many data centres, ensuring the closed circuit water system is running as it should is a less sophisticated affair. If a closed system becomes corroded, for example, expensive repairs and potentially catastrophic downtime could ensue, not to mention the strain that this fouling will place on associated systems, leading to greater energy usage.
The traditional regime for corrosion and other condition issues is sampling, which falls short on a number of factors – results can take weeks to return, it only presents a snapshot in time and sampling fails to identify dissolved oxygen effectively. The latter point is key – oxygen is the pre-cursor to all forms of corrosion, either directly or by creating the conditions for bacteria to thrive, which can lead to Microbial Induced Corrosion (MIC).
A more effective approach for critical operations such as data centres, is 24/7 remote monitoring. We use Hevasure’s technology which provides constant information on a range of parameters, including pH, temperature, pressure, inhibitor levels and the all-important dissolved oxygen. Any changes are instantly detected and sent straight to the in box of responsible parties, meaning small issues can be flagged up and dealt with before they become major problems.
Using monitoring throughout a closed circuit water systems life means expensive repairs and breakdown can be mitigated, systems remain efficient and maintenance regimes are fit for purpose, avoiding knee-jerk reactions which can lead to the unnecessary use of flushing and chemicals. Where possible, flushing should be avoided – the process wastes water, adds O2, can degrade pipework and serves to mask rather than solve the problem.
When data centres go wrong the repercussions and costs escalate quickly, potentially effecting vast numbers of people. For those responsible for data centres, downtime avoidance is the priority; sustainability is a secondary concern. While it has been predicted that the carbon footprint of the data centre sector will even surpass that of the aviation industry soon, there are steps data centre owners and their maintenance teams can take to improve the situation. Whether water or air cooled, by using the latest technologies sustainability can support reliability, meaning that the environmental cost for our continued thirst for all-things digital can be managed and hopefully reduced.
Toby Hunt is from Guardian Water Treatment
