24 Building Services
improving energy and water usage in data centres With the growth in demand being placed on UK data centres, electrical usage is a continuing focus in efforts to mitigate climate change. Working alongside data centre specialist, Ian Bitterlin, water pump manufacturer, Wilo UK, has identified how chilled water pumps are key to improving energy and water usage.
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he Covid-19 pandemic has caused a surge in demand at data centres in the recent months, with more adults currently working from home and families streaming more content during the day. The implementation of 5G technology and streaming video is also rapidly driving data growth. With users unlikely to reduce their usage, actions such as lowering cooling losses at data centres are important, with better pumps and more efficient controls a key enabler in facilitating this. There is increasing pressure from the EU for data centres to be powered by renewable energy; however, the first step is to reduce the power consumed by the data centre infrastructure. The Green Grid, the innovator of the Power Usage Effectiveness (PUE) metric, has recently proposed the introduction of a new data-centre metric, Water Usage Factor (WUF). As PUE expectations drive lower, data centres are now being judged for water consumption as well as electrical energy use. The majority, 80%, of all data centres utilise chilledwater systems for cooling, 15% use direct-expansion refrigeration systems, and just 5% use air-based evaporative or adiabatic cooling systems. Consulting Engineer, Ian Bitterlin, commented: “Chilled-water systems (the dominant technology used to date) have continued to evolve technically, with better controls, heat-exchanger technology, variable Quarter 3 2020
speed compressors, fans and pumps. They have also developed operationally, with flow water temperatures rising from the legacy 6°C to 18°C (and higher), enabling high percentages of free cooling in suitable climates. Because of this change, an older technology has recently proved more popular – that of evaporative or adiabatic cooling. “In pursuit of achieving an ever lower PUE, the advent of free cooling solutions brought along with it adiabatic cooling solutions, where water is used to take advantage of the wet-bulb ambient temperature and crucially humidification of high volumes of fresh air. Perhaps for the first time in Europe, water consumption in data-centres is a growing issue.” Evaporative and adiabatic cooling technology – which dates back to before Roman times in high-status dwellings – use water to increase the humidity of warm, dry air and reduce its temperature from the dry-bulb to the wet-bulb value. For example, in the UK when the external ambient is near the record high of 35°C drybulb, the addition of water vapour can get the air-stream temperature down to 23°C wet-bulb and this can then be used to cool the data centre. Evaporative and adiabatic cooling systems can save 20-30% of a data centre’s energy (compared to chilled water systems) and do not use pumps. However, they have not proven to be universally popular as they need a lot of space and use a lot of water. www.bpma.org.uk
