Networks Europe Jul-Aug 2017 | Page 54

54 GREEN DATA CENTRES Improving sustainability By Alan Luscombe, Director, Uninterruptible Power Supplies UPS systems can make a valuable contribution to overall efficiency Data centre operators are under steady pressure to run a facility with visibly green attributes. Not only does this become increasingly important as electricity prices inexorably rise, but it also improves a data centre’s carbon footprint in line with corporate responsibility endeavours. This contributes to an amenable working environment and enhanced relationships with local communities, while at the same time meeting legislative pressures and incentives to create and maintain ecologically responsible businesses. Many large undertakings qualify for participation in the Energy Savings Opportunities Scheme (ESOS) – an energy assessment and saving scheme run by the Environment Agency. Organisations that meet these definitions must carry out an ESOS assessment covering all their energy use, unless they have an up to date and comprehensive ISO 50001 energy management system that’s certified by an accredited certification body. ESOS compliant energy audits must identify energy saving opportunities, although these should be reasonably practical and cost-effective to implement. Participants will probably wish to implement any such opportunities, provided the money saved by reduced energy use exceeds the cost of implementation. However, there is no regulatory requirement to do so. Any participant comprising or including a data centre, will almost inevitably contain a power protection system complete with an uninterruptible power supply (UPS). This can offer opportunities for energy savings depending on the type of UPS installed, and how it’s being used. Ideally the on-site installation utilises a modern modular design that can deliver great power efficiency, as well as other benefits including high availability and scalability. However, in reality many sites have older legacy systems and these are where the energy reduction opportunities can mainly be found. Transformerless technology vs legacy installations Energy savings arise firstly from a move to modern transformerless technology made possible by advances in power semiconductor technology, and the advent of Insulated Gate Bipolar Transistor (IGBT) devices. The technology is more efficient than the earlier, transformer-based designs with an overall improvement in efficiency across the load spectrum of around 5%. This yields substantial reductions in heat losses and energy running costs. Transformerless systems also bring the input power factor closer to unity with less load dependence. Input current magnitude is decreased, with associated reductions in switchgear and cable sizing. In some cases, electricity costs are also reduced. Legacy systems are often operated below their optimum efficiency because they’re not easily scalable. This lack of scalability means that until recently many systems were significantly oversized to allow for the prevailing load and any expected future growth. The graph in Fig. 1 demonstrates this by showing an expected load profile that starts at 35% of the data centre capacity, with a projected growth to 90% of capacity over 10 years. The same graph also reveals that a UPS sized for 100% data centre capacity was installed, yet in reality the load only ever reached 35%. Accordingly, the UPS remained significantly underloaded, which seriously impacted its efficiency over its lifespan. A legacy UPS has a maximum efficiency of about 93% when fully-loaded, dropping to about 90% at 50% loading, and even less at the levels shown in the graph.