SUPPLEMENT FEATURE DATA CENTRES & UPS Balancing sustainability and resilience

in data centre UPS installations Alex Emms, operations director at Kohler Uninterruptible Power, explains why the search for ever-improving efficiency can conflict with the Uptime Institute’s Tier lV redundancy and resiliency requirements, and proposes a solution that uses smart modular UPS technology while providing upfront assistance during the design phase


PS users of all sizes mostly view power resilience and efficiency as

their two highest priorities. While the balance between these factors varies according to the load’s size and criticality, the power efficiency aspect is assuming an ever-increasing urgency. Organisations today must improve efficiency not just to reduce costs, but also to demonstrate a responsible, green energy policy. Further, they must be government compliant, as highlighted by Theresa May’s commitment to achieve net zero carbon emissions by 2050.

SUSTAINABILITY CONCERN DigiPlex, a pan-Nordic green data centre operator, has released a survey of almost 300 decision makers in Sweden and Norway, titled ‘A Perfect Storm: Nordic Data Centre Trends 2018’, containing extensive research into changing attitudes and business priorities. Survey results revealed sustainability to be the fastest rising data centre concern, from 27th place to fourth place in just two years since the 2016 survey. Carbon costs are becoming a global

issue, with pressure from activist groups like Greenpeace and increased government awareness pointing to potential fines, new taxes or reputation damage down the line.

TIER CLASSIFICATION The Uptime Institute’s four-tier classification system allows users to balance resilience levels against cost. However, the uptimes are achieved through various redundancy levels, which have differing impacts on UPS utilisation and efficiency. Tier ll, for example, calls for

redundant capacity components and single non-redundant distribution path to site computer equipment. This could be fulfilled by two standalone UPSs on a single path, each rated at 300kW. The N+1 redundancy requirement is satisfied; however, neither UPS will ever be utilised beyond 50 per cent.


Unusually low data centre demand could push UPS loading into a less efficient operating region. An alternative, more efficient

configuration could be fulfilled, for example, by a PowerWAVE 9500DPA modular UPS system. With four 100kW modules supporting the 300kW load for N+1 redundancy, per-module utilisation improves to 75 per cent; more margin for energy efficient operation. This energy efficiency issue is more

problematic in Tier lV infrastructures, which call for redundant capacity systems and multiple distribution paths. A 2(N+1) UPS system, as shown in Figure 1, can meet this requirement. Figure 1’s configuration, although

modular, has a maximum utilisation per module of 37.5 per cent; uncomfortably close to the UPS’s inefficient operating region. However, it’s possible to overcome this issue using smart modules, as described below.

XTRA VFI Efficiency for modern, modular UPS systems remains high for most load values, only falling significantly once loading drops to 25 per cent or less. Accordingly, the 37.5 per cent 2(N+1) loading, while low, still allows full efficiency operation, provided it is maintained. Xtra VFI achieves this ‘load level

maintenance’. The mode automatically adjusts the number of active modules to match current load requirements. Excess modules, while switched to standby, become active immediately if the load increases. Suppose, for example, Figure 1’s load

falls to 200kW. The per-module loading drops to 25 per cent accordingly. However, Xtra VFI could then disconnect one 100kW module per UPS while still preserving 2(N+1) redundancy for the reduced load. Meanwhile, utilisation improves back to 200kW/6 modules = 33.33 per cent, so the UPS continues supporting the reduced load with both full redundancy and full efficiency.


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300 kW LOAD

Figure 1: 2(N+1) modular UPS

configuration for a Tier lV installation

OPTIMUM SOLUTION From this article we can see that the optimum UPS solution for any installation depends entirely on its circumstances and priorities. Accordingly, when KUP sales engineers discuss new projects with clients, they take a consultative approach. They find that informal, wide ranging conversations can be the most productive, as these can surface not only the obvious issues, but others that are less so, yet also important. A good starting point can be to discuss configurations that will help a client to best balance their expectations of budget, resilience and energy efficiency.

CONCLUSION Whether embarking on a newbuild project or an existing system upgrade, UPS system users will benefit greatly from engaging with a supplier like Kohler Uninterruptible Power, whose advanced modular technology is backed by nationwide technical support and long-term business stability.

Kohler Uninterruptible Power

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