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Data centre cooling best practices

Climate change
Image: Adobe Stock / severin

For those of us who have worked in the data centre industry for years, we appreciate that these technical buildings are fundamental to the functioning of today’s economy and modern society.

As our reliance on digital technology grows, so does the amount of data, and the need for data centres as the foundation of the digital infrastructure. Without them, businesses simply couldn’t operate.

According to Allied Market Research, the global data centre market was valued at $187.35 billion in 2020, and it is projected to more than double, reaching $517.17 billion by 2030. However, the increasing reliance on technology comes with an increase in energy consumption and associated carbon emissions. Many countries have set targets for reducing carbon emissions and engineers are expected to play a role in helping data centres to achieve these goals. Adding to the pressure, customers are choosing to work with providers that have strong sustainability practices. As a result, data centres are facing pressure to be more sustainable.

What can’t be avoided is that data centres need energy to keep the systems housed within them at the right temperature and humidity so that they are as efficient as possible. This makes cooling technology critical, not only to maintain an optimum environment for the IT systems, but also to consume power responsibly. The result is innovative cooling solutions which have the potential to slash the environmental impact of the data centre. The right cooling solutions are crucial to helping providers meet their green ambitions and positively affect customer ESG targets.

A sustainable approach to water cooling

Today, more and more providers are turning to chilled water systems as an economical, effective and efficient way to maintain cooling. This is because once a system is operational, only limited amounts of make-up water are required. The cooling demands of hyperscale data centres tend to favour chilled water-cooling systems because the water impact is negligible.

Chilled water systems have significantly improved in terms of energy efficiency with the increase in ‘free-cooling’ capability, i.e. using ambient outside temperatures for cooling instead of high-energy mechanical units. Furthermore, many servers are now being manufactured to operate at temperatures as high as 27°C, so natural air cooling has become a more viable option for data centres in a range of locations. With the addition of Artificial Intelligence (AI), internal cooling systems can be optimised by automatically matching weather and operational conditions, reducing cooling energy usage by up to 40%.

Adiabatic cooling makes up a relatively small percentage of the overall cooling infrastructure in the UK, but the sector is increasingly looking to deliver this method more widely, using alternative water sources, without impacting mains supplies.  With the de-carbonisation of the grid, the purchase of accredited green energy, innovations in compute and mechanical cooling, the use of an additional valuable natural resource, i.e. water, isn’t always necessary to cool systems. As an alternative, electricity can be used with little to no impact to the environment – provided it comes from renewable sources – and still achieve the same Power Usage Effectiveness (PUE) or less.

Harvesting the elements

Rainwater harvesting can bring increased efficiency and cost savings. Many data centres in the UK have the ability to collect and store rainwater from their rooftops, which can then be used for non-potable purposes such as supplementary cooling or even for use in toilets. It also helps to reduce the strain on local water resources, especially during times of drought or water scarcity. By collecting and reusing rainwater, data centres can reduce their dependence on treated municipal water, which can be a finite resource in some areas. This not only helps to reduce the environmental impact of data centres, but also ensures a more reliable and sustainable water supply for the facility.

Aquifers are another natural source of water that some data centres can benefit from. By digging a borehole at the inception of a site, this can be used as a natural water source for cooling, thereby reducing demand on the mains water supply. Combined with the local climate (if the temperature is below a certain level), the air in the data centre can be chilled without any mechanical cooling This efficient cooling technology delivers low Water Usage Efficiency (WUE) for the site.

If there isn’t access to an aquifer and instead mains supplied water is being used, then this is a major challenge. Heating Ventilation and Air Conditioning (HVAC) systems are good cooling solutions to use in areas where water is a concern or where that technology is more appropriate. The customer usage of the facilities is a key element in how efficient the data centre can be. So it is important that the data centre provider and their customers work in harmony; if a provider operates the most efficient PUE environment but the customer deploys their IT systems in a way that degrades the performance, then investments in plant technology are almost wasted.

Cooling with less energy

Indirect Evaporative Air Cooling (IEAC) can provide the cooling needed but with a very low energy use. It produces better PUE statistics in comparison to traditional HVAC systems. However, there are some additional operational overheads, so the technology needs to be considered holistically rather than as a standalone cost. Furthermore, to deploy IEAC in the most efficient way, the data centre build needs to have a particular layout, so the technology isn’t appropriate for every building.

Liquid cooling can be used to maintain optimal operating temperatures, notably in the High Performance Computing arena, together with innovative techniques like using indirect evaporative air. This strives to produce a 1.0x PUE which, according the Uptime Institute’s annual survey, is well below the 2020 average of 1.58x. All operators attempt to get the PUE ratio down to as near to 1.0x as possible, with most new builds falling between 1.2x and 1.4x.

Direct chip liquid cooling in another energy efficient solution. It offers some of the lowest PUE possible, as the temperature at which it operates means that no mechanical or adiabatic cooling would be required. The warm water can be reused within the data centre or exported to other heating requirements. If a Computer Room Air Conditioning (CRAC) system was deployed, the waste heat and water from the units could be used to cool liquid cooled compute, which means that the cooling medium would be used twice, making it more sustainable.

These methods not only improve the operational sustainability of the data centre, they also reduce the site’s dependence upon local distribution networks.

Up and coming solutions

Immersion cooling systems are gaining traction. These require bespoke IT hardware that is immersed in dielectric liquids which are much better thermal conductors than both air and water, and do not require as much supporting infrastructure to ensure the IT equipment stays at the right operating temperature. This is not suitable for standard IT equipment yet but is an option for High Density Computing requirements.  

Data centre operators are making significant strides towards a greener future by taking a proactive approach to sustainability and implementing innovative cooling solutions. In doing so, the industry is not only reducing its environmental impact, but it is positioning itself as industry trailblazers and leading by example. Crucially, these innovative solutions reduce the environmental impact of data centres and bring cost savings and increased efficiency for customers.

David Watkins
David Watkins
Solutions Director at Virtus Data Centres

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