With more than 30 years’ experience in the UK power protection business, Alex Emms, Operations Director at Kohler Uninterruptible Power, notes the strategic choices that should be made for competent power usage.
Data centres are estimated to be responsible for up to 3% of global electricity consumption and are projected to touch 4% by 2030. The average hyperscale facility consumes 20-50MW annually – theoretically enough electricity to power up to 37,000 homes. With this massive power requirement and the need to look after our planet, government scrutiny has increased. In some places around the world, including Dublin, Ireland and Singapore, steps to control data centre energy use among other carbon reduction objectives have already been put in place.
For many years, the efficiency of an Uninterruptible Power Supply (UPS) has been gradually improving but it has been the mechanical cooling systems that have attracted the most attention regarding the energy overheads reduction. Integrating more efficient, modular UPS systems that include Insulated Gate Bipolar Transistors (IGBTs) rather than transformers, power management systems and smart modes help to reduce energy loss and decrease an organisation’s Power Usage Effectiveness (PUE).
PUE can be defined as a measure of how efficiently power is used within a data centre. It is calculated by measuring the ratio of total amount of power used to the amount of power delivered to computing equipment.
Although a small cog in a larger environment, UPS power and built-in redundancy are crucial factors in bringing the PUE down. There are three key areas of innovations in technology and processes that are being implemented for sustainable UPS systems. These are: reducing power loss by choosing a high-efficiency UPS; matching the size to actual load by taking advantage of the correct load and smart running modes and reviewing battery technologies; taking a wider view including management and recycling. By taking all three of these points into consideration, data centre managers can improve their energy efficiency with immediate effect.
However, choosing the most appropriate UPS solution for your site does need consideration as one size does not fit all. The choice must allow for the user’s business model as well as their site conditions. Accordingly, an in-depth discussion with an experienced supplier will pay dividends. Their experience, which equips them to explore the relevant issues, is backed by the know-how and the products needed to implement an appropriate solution – one that ensures reliability of power protection.
Transformerless versus legacy systems in UPS
There has been a lot of development in UPS design recently – and some of these have offered greater energy efficiencies. Energy savings first arose when the design moved to modern, transformerless technology made possible by advances in power semiconductor technology and the advent of IGBT devices. This technology is more efficient than the earlier, transformer-based designs with an overall improvement in efficiency across the load spectrum of about 5%. This can lead to substantial reductions in heat loss and energy running costs.
Transformerless systems also bring the input power factor closer to unity with less load dependence. This is important as anything less than one means that extra power is required to achieve the actual task at hand.
Managing the load
Traditionally, UPS design involved a large framework system which had to cover all the capacity required. Therefore, the system was always on at full power – operating below its optimum efficiency because it was not easily scalable. Nowadays, there are modular designs where calculating and managing the load, so there is always redundant capacity for spikes in power usage.
When working out energy efficiency, reviewing the power required is critical so the design of the data centre and its systems, as well as its ability to handle maximum load, are put in place and future-proofed. System engineers will now look to only fit and connect what is needed but with smarter procurement and flexible modular systems. These designs can offer more longevity and still cover redundancy for the critical power needed.
Newer modular systems offer flexibility in a single infrastructure cabinet which can be run smarter, such as in Kohler’s Xtra VFI mode where spare modules go into standby mode when not required to support the load while still maintaining the required level of active redundancy. This also means a reduction in energy use and subsequent less cooling in some situations.
Expansion of capacity is a matter of adding a further module and contraction is a simple matter of turning off modules, reducing the need for systems to be always on, powered to the max, 100% of the time. The aim is to allow the UPS to be loaded to 30-60% at any given load – where the UPS will be able to provide its highest efficiency rating.
The ability to continuously ‘right-size’ the UPS capacity to the load lets users minimise their power and cooling requirements, which consequently reduces power usage over the life of the UPS.
Also, when we look at the load/efficiency curves for modern, modular systems we can see they are not entirely flat but instead produce slightly higher efficiency at partial loads. This is because UPS manufacturers recognise that modular systems are typically operated in ‘redundant mode’, so no single module will be fully loaded. For example, in an N+1 system comprising two modules in parallel and sharing the load equally, neither will ever have more than 50% loading.
Moving to newer UPS solutions over a legacy framework can offer a significant reduction in PUE as well as a more cost-effective ROI. But planning, research and choosing the right supplier are key to obtaining energy efficiency and critical power backup with no compromise on reliability.
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