March 2020

40 March 2020 www.drivesncontrols.com Curbing data centres’ ravenous appetite for energy D ata centres already use around 2% of the world’s energy, and their demand is predicted to quadruple, to some 3,200TWh, by 2030. About 40% of this energy is needed for the cooling systems that ensure the facility remains operational around the clock. In Ireland, for example, Amazon is building a €1bn data centre that will assume around 4.4% of the country’s total energy demand by 2026. And around 100 other large-scale data centres are either already operating or planned for the country. Not surprisingly, a lot of effort is going into improving data centre PUE (power usage effectiveness) by improving the energy efficiencies of the fans, pumps, and compressors that form the heart of the cooling systems. The cooling systems are sized to handle peak loads under the most adverse conditions – in the heat of summer, or if a component fails, for example. But, inmost cases, they are not operating at their design loads. For much of the time, they operate in a lightly loaded state. The challenge is to ensure that the cooling system can adjust to match the varying load profile to maintain high system efficiency, even at partial loads. There are numerous options when it comes to motors and speed controls for fans, pumps, and compressors. When considering their efficiency, it is important to consider the total effect of both electrical and mechanical performance. A high-efficiency motor operating in combination with a VSD (variable- speed drive) can offer superior efficiency. Power quality Reliability is critical for data centres, and their cooling systems play a vital role in ensuring the facility is always up and running. Harmonics in the power network is one of the key factors that affects reliability. While VSDs make a significant contribution to energy efficiency, together with other non- linear loads (such as UPS and battery storage systems) they can cause current and voltage waveform distortion, increasing troublesome harmonics in the power supply. Harmonic currents result in power losses that add heat to the power chain. This can increase the risk of downtime by causing equipment to malfunction and fail. Harmonic currents therefore need to be minimised. From a system perspective, there is, of course, the opportunity to simply over- dimension the cables, fuses and switchgear. But if there is no mitigation at all – as is the case with some EC (electronically commutated) fans – the need for over-dimensioning can be up to 30%. In addition to costs incurred due to shorter equipment lifetimes, process issues, and frequent maintenance of malfunctioning devices, costs can be increased further by penalty charges imposed by electrical utilities As data centres proliferate to support cloud services and other computing operations, they are creating a massive demand for energy. Frank Grundholm, vice-president of global HVAC sales at ABB Motion, considers how this demand can be met and managed cost-effectively. n BUILDING SERVICES