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rDATA CENTRE MANAGEMENT


Reducing reliance on unsustainable mechanical cooling in data centres


Carbon emissions from the world’s nine million data centres equalled that of global air travel in 2019, with the pandemic likely growing this figure further. Taking this into account, Gemma Reeves, business unit manager specialising in Data Centres for EMEA at Alfa Laval, looks at how greener IT solutions can be implemented, with particular focus on efficient heat transfer within facility cooling systems


and working-from-home arrangements has led to drastically increased data usage, placing existing digital infrastructure under strain. This strain translates into increased energy demand for data centres, and with cooling alone accounting for 40% of a facility power demand, developing more efficient heat transfer systems is a must. Beyond just improving efficiency, there are the 2050 net zero carbon emissions targets to consider, making it necessary to identify methods to reclaim waste heat. Yet despite the sector looking to become greener, many in the industry are too reliant on unsustainable, traditional mechanical cooling techniques. New solutions, including heat exchanger technology, are therefore required to reduce the sector’s carbon footprint.


T


THE ROLE OF THE HEAT EXCHANGER


Heat exchangers are available in many varieties, from gasketed to copper-brazed, and can be used for multiple applications within data centres. For example, the sensitive electronic equipment used in the server room needs to be kept at an exact temperature and shielded from external contaminants – two functions an exchanger can fulfil. They can also be used as a cooling tower interchanger, to provide free cooling by utilising nearby water bodies, or operate as a free cooling interface with dry or adiabatic air coolers. Finally, they can be used in new greener applications like liquid immersion cooling and waste heat recovery. The taxing performance requirements associated with reducing data centre power and water usage makes them well-suited to this environment. Such pressures make it vital to work with heat exchanger manufacturers during the data centre design process, and specify application-appropriate exchangers to ensure excellent performance throughout the site’s lifetime.


A good way of appraising a heat exchanger’s quality is checking if it is certified by the industry- trusted Air-Conditioning, Heating and Refrigeration Institute (AHRI). This independent organisation develops standards and certification programmes


S4 ELECTRICAL ENGINEERING • SUPPLEMENT • JUNE 2021


hough the pandemic has led to reduced emissions due to the significant drop in air travel, the concurrent rise in videoconferencing


and reduced thermal efficiency. Such issues can be bypassed by installing a gasketed heat exchanger as an intermediate, without compromising system performance. As most electrical energy in a data centre will be transferred to waste heat, recovering this is another option available to facility owners and operators. Alfa Laval, for example, provided equipment that helped recover server heat and redistribute it to a local district heating network. This example saved 100,000 MW – enough energy to power New York City for nine days.


to ensure supplied units perform as specified.


REDUCING MECHANICAL COOLING REQUIREMENTS


Mechanical cooling has doubtlessly fulfilled its purpose to date but as data centre usage has increased, sites’ use of fossil fuels or electricity to lower system temperatures means it is now seen as an energy drain. As such, it should only be used minimally. Free cooling presents an alternative – bringing in low-temperature ambient air to cool the centre, so chillers are used less. As chillers constitute a large proportion of a centre’s utility electricity requirement, and therefore present large financial and carbon costs, this method is attractive to sustainability-minded facility owners and operators. Cooling towers, which dissipate data centre heat, are also used in free cooling to bypass chillers, further improving the site’s carbon footprint. Yet they also present a large fouling risk for cooling systems, resulting in a greater possibility of equipment failure, alongside added maintenance


IMMERSION COOLING?


Machine learning and high computing applications like blockchain technology use high density processors, this requires more efficient cooling strategies beyond blowing air over equipment, with liquid cooling considered a viable option. As liquids like water are thousands of times more efficient at absorbing heat than air, innovation has continued in this space, especially around ‘immersion cooling’. This involves submerging servers and components into thermally conductive liquids known as dielectric coolants. Crucially, this medium does not conduct electricity. Multiple immersion cooling options are available, including single-phase and two-phase variations. From initial results, both appear to typically provide a significant, 35-75% reduction in cooling energy usage. Though the overall sustainability savings of this method remain under evaluation, one thing is clear – growing server power density means air- cooled systems cannot cope. Consequently, more efficient liquid cooled solutions like immersion cooling are required.


HEAT EXCHANGER POTENTIAL


In conclusion, heat exchanger technology has a vital role to play in improving the efficiency of current and future data centre systems. Alfa Laval is continuing to innovate in this space and raise awareness of this integral equipment’s role in optimising energy use in cooling applications and improving overall sustainability.


ALFA LAVAL alfalaval.com


electricalengineeringmagazine.co.uk


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