Redundancy protection

Businesses should prepare for disruption to their power supply in the future, says Alan Luscombe of Kohler Uninterruptible Power Ltd. He explains how modular, redundant UPS systems maximise the protection and availability of critical loads, while delivering valuable flexibility, efficiency and environmental benefits.

Candle power, the domestic solution to blackouts in the 1970s, could make an unwelcome return if renewed power cut predictions transpire.

In the past, politicians have assured that there is “no danger” of mass power cuts in the UK during the next decade, while others such as Professor David MacKay, of Cambridge University, warned that the UK could face blackouts by 2016 as green energy is slow coming on stream to replace older coal-powered stations. Other expert opinions suggest this energy shortfall could even occur as soon as 2012.

In any event, most prudent households will have a ready supply of tealights and torches, but how well are businesses prepared – now and into the future – for disrupted mains supply? The UK’s aging power stations are undoubtedly a cause for concern and until a clear and consensual picture emerges, trusting that the ‘generation gap’ will be bridged remains a high risk strategy.

35 years ago, while candles provided households with a simple source of alternative energy and ‘back-up power‘, the three-day week limit on commercial electricity consumption literally pulled the plug on business and industry – an unthinkable scenario for today’s 24/7 IT requirements and round-the-clock trading. Even comparatively moderate shortages would now have a far greater and more widespread commercial impact, given the deep dependency on continuous power for critical applications.

UPS solutions

While uninterruptible power supply (UPS) systems coupled with standby generators provide back-up against power cuts and fluctuations, they are increasingly stretched by rising energy demands and the need for flexibility to meet capacity and configuration changes required by IT installations. Growth in this sector continues apace, despite the prevailing downturn in industrial output.

The rapid expansion of Internet applications, and the proliferation of microprocessor-based equipment in industry and commerce, has dramatically increased the numbers and types of electrical load falling into the ‘critical’ category. This is outstripping the level of protection many existing UPS systems were originally designed for and consequently failing to provide any form of redundancy and presenting a potential risk of failure.

Such issues are easily resolved with today’s modular, parallel redundant UPS solutions, which provide their own ‘backup’ should capacity be exceeded or in the event that any single module shuts down or requires maintenance. With a minimum of one module over and above that required for capacity, UPS redundancy ensures continuous support of critical loads, without any of the historic concerns about expense or expanse. The notion that redundancy meant ‘doubling up’ on budget and physical footprint has in fact been reversed, with today’s modular rack-mounted systems offering significant savings in space and total cost of ownership, as well as providing high power density and contributing to lower emissions.

Size and Space

The development of transformerless, modular UPSs has significantly reduced their size compared with free-standing legacy systems, taking up only 25 percent of the floor space. Rack-mounted, vertically scalable modules mean that additional capacity for redundancy or load upgrades can be achieved without increasing the footprint, a major benefit in light of the burgeoning space and capacity crunch faced by today’s server rooms and data centres. An N+1 configuration (compared with traditional 1+1) means that extra modules can be installed in an existing cabinet at a fraction of the cost of an additional stand-alone unit.

When specifying a UPS system, it can understandably be difficult to predict what the final load is going to be, particularly given the exponential growth of IT power and data storage needs, so installations are often oversized to provide contingency. While this may ensure sufficient UPS capacity, it means inefficient operation and poor cost control. By choosing a parallel redundant solution to increase availability, users also gain the benefit of ‘scalability’. Modularity gives users the flexibility to correctly size the system from day one and, when loads increase, additional UPS units can be inserted cost-effectively and without downtime. ‘Hot-swappable’ UPS modules can also be transferred from one floor or server suite to another or even to a different site, providing capacity and redundancy when and where it is most needed – a welcome boon for flexibility and reconfiguration.

Energy and Cost Efficiency

Specifiers have a tough task planning systems today that will cater for energy needs over the next ten to twenty years. Pressure to shrink carbon footprints, plus rising energy costs and recessionary impact, make this issue all the more pressing.

Trying to cater for future needs with traditional stand-alone UPS systems can lead to over-specification, creating a wasteful gap between installed capacity and the size of the actual critical load. Such inefficiencies mean that companies could be burning excess electricity and creating needless heat emissions, costing thousands of pounds and compromising efforts to reduce their carbon footprint.

Modern UPS technologies, such as transformerless, modular configurations, are providing new ways to save energy and costs including rightsizing the UPS over time, higher efficiency for partial loads, lower cooling requirements,improved input power factor,and improved input current total harmonic distortion.

We can compare a single stand-alone non-redundant 100kVA UPS solution with a parallel redundant 3 x 50kVA UPS rack-mounted solution. While the latter may carry a price premium, the cost-benefit is quickly apparent. The modular configuration provides redundancy if one of the units fails, and spare ways can accommodate an increase in capacity in affordable, incremental steps without interruption to the critical load. The stand-alone system provides no redundancy, and the addition of a second parallel 100kVA unit to increase capacity would be more costly, take up twice the space, and would also incur downtime during installation.

Right-sizing

UPS with higher power density and ‘hot swappable’ rack-mount configurations mean that modules can be inserted or removed to continually match the capacity of UPS systems to their respective critical loads.

Figure x illustrates how the ability to right-size modular UPS systems promotes efficiency. The limited flexibility of a stand-alone UPS would require the initial installed power to exceed anticipated capacity requirements, resulting in an inefficient, over-sized system. However, the flexibility and scalability of modular rack-mounted systems means they can now be ‘right-sized’ from the outset by inserting or removing ‘hot-swappable’ modules, enabling power to be cost-effectively added as requirements grow and without any footprint penalty.

When compared with conventional parallel protection systems, modular redundant UPS solutions not only maximise system flexibility and availability, but meet wider strategic aims on energy efficiency and environmental compliance, reducing electricity costs, heat loss and CO2 emissions, while delivering the industry’s smallest footprint and N+1 parallel redundancy.

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