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FACILITIES power+cooling

plan will allow for the take up of ‘free floor space’ to house additional servers and extra associated power and cooling services, if required. For a micro-data centre, expansion may simply mean installing additional servers in the existing server cabinet. For a large data centre, it can be the addition of one or more server cabinet rows.

Over recent years, changes to data centre infrastructure, for example virtualisation and advances in servers that have made them smaller in size but just as power hungry (if not more so), have made it more difficult to predict data centre power demand when future proofing. Although virtualisation actually reduces the power demand of the servers and enables them to work more efficiently, it also frees up more space in the data centre which allows for expansion of the server estate. This often results in greater demand for power than before.

Such factors should be taken into account early on in the design of the data centre power structure so that future expansion plans can be incorporated and the best UPS solution can be identified from the outset. Historically, UPS systems have been oversized to meet the needs of tomorrow, today. But this scenario is wholly unacceptable in today’s efficiency- conscious data centres. Systems should be right-sized and expanded incrementally by adding new units one at a time and simply sliding them into place.

Everything in modulation It is new ‘modular’ technology which has allowed for flexibility and ease for expansion in data centres ranging in size from micro to large scale. According to global research body Frost & Sullivan, the market for modular UPS is expected to grow to £260m (US $400m) by 2017. Whilst only representing less than 10 per cent of the overall UPS market, it demonstrates a growing acceptance of the modular component UPS. This is driven in part by the growing development of small to medium sized data centres and their need to rapidly expand to meet the demand for cloud-type services.

The 2012 Best Practice Guide for the EU Code on Data Centres also recommends a modular approach to data centre design. Modular ultimately offers the maximum in availability, scalability, reliability and serviceability whilst also offering high efficiency, low cost of ownership and a high power density as space is always a premium in the modern data centre. Key highlights include:

£ Floor space flexibility

Modular component UPS systems can be expanded vertically provided there is room within the existing cabinet for additional UPS modules. Alternatively a modular component UPS system can expand horizontally with the addition of a further UPS cabinet.

£ Operating efficiency

The basic argument for a modular component UPS system is that by rightsizing the UPS to the load size, maximum operating efficiency can be achieved. This is because maximum efficiency is typically achieved when operating at 80-100 per cent of the design capacity.

£ Expansion

In a modular component UPS system, additional UPS modules can be added to meet future expansion or a standalone UPS can be oversized to allow for this. Load sharing within the chosen system is also important and can affect operating efficiency. As UPS modules or standalone UPS are added to a parallel configuration, the load is shared between the UPS modules.

£ Ease of use

Modular component UPS systems are slightly easier to service and repair in situ because a failed UPS module can be ‘hot-swapped’. The failure or suspect module is then returned to a service centre for investigation. To return a standalone UPS system to active service may require a board swap.

£ Single points of failure Standalone systems operate as a single UPS with no shared components other than a communications cable. Failure

of the cable or accidental disconnection is accommodated in firmware algorithms within each UPS to ensure that the entire system continues to function and support the load.

Modular vs standalone In terms of resilience, both modular and standalone UPS approaches can be configured to provide similar levels of availability. Modular component UPS systems have a premium price compared to standalone UPS but when the space saved and the total cost of ownership are considered, the overall price is comparable. Resilience is a major factor and when selecting a modular solution, close attention should be paid to any single points of failure such as a common controller as should this fail, the whole system will fail in spite of any redundant module. Due diligence is always recommended when selecting the right modular solution.

Technology to boost energy efficiency in the DC With efficiency a key data centre driver, there is a shift towards energy generated from renewable power sources, such as solar panels. Consequently, UPS manufacturers are developing products that are Smart Grid ready so that they can be integrated with alternative renewable power sources and facilitate switching between the grid and solar, while allowing export back to the grid. The introduction of Lithium Ion (Li-ion) batteries has made it more feasible to utilise UPS batteries as energy accumulators.

Again, this allows the export of power back to the grid but it can also enable the data centre to operate in island mode when a generator is present − effectively taking the data centre off grid for a short period of time. For data centre operators, this not only helps to manage energy costs but also creates an additional revenue stream and offers an opportunity to test the resilient power system in real time with minimal operational risk.

The data centre of the future With a continued reliance on the internet and vast amounts of data out there, it is clear that there will be more demand placed on data centres. Technology is continually advancing and approaches like modular should therefore be embraced to continue to raise the bar in data centre efficiency. UPS will continue to play a vital role in the power chain but the role will go beyond simply back up power and focus on the additional benefits to businesses.

February 2015 I 35

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