UPS - Balancing UPS efficiency and performance

Typography
Articles

As news reports dwell upon the difficulty of procuring major utility power supply, the need for overall power efficiency has moved into the centre ground and with it prominent sources of consumption are therefore brought into focus. Shri Karve of APC by schneider electric explains

The ‘white space' of a datacentre has been identified as a particularly acute consumer due to the mission-critical nature of IT services, but it is not the only space that commands attention.  ‘Grey space', which houses the electrical switchgear and plant of critical facilities such as hospitals, transportation hubs, commercial and industrial premises entails equally catastrophic risks of failure.

In these situations uninterruptible power supplies (UPS) are required for protection since an interruption lasting no more than a fraction of a second can devastate operations and in some cases, threaten life. The consideration holds true that the greater the degree of mission criticality, the greater the need to avoid downtime, the more complex the deployment of UPS, and therefore the greater the emphasis on achieving high efficiency and reducing waste without compromising availability (resilience). In today's operational climate, no source of efficiency or saving can afford to be overlooked.

With UPS designs in general becoming more reliable, APC suggest that efficiency in terms of energy consumption mainly, but also in respect of footprint and skills, should become the major selection discriminator. The task however, is to understand how efficiency is being quoted by manufacturers, as each will no doubt quote a figure which presents their system in the best possible light. The reality is that under operating conditions, advertised levels of efficiency may never be achieved for a variety of reasons, primarily that efficiency claims are usually made on the basis of a higher loading than is normally faced due to redundant design concepts.

APC highlights a multi faceted approach to enable efficiency strategies to be introduced which are appropriate to individual applications, for example in white space where loads are dynamic, scalable systems are key to ensuring that IT is adequately protected without the energy wastage associated with over-sizing of infrastructure. In grey space physical size and operating efficiency may be essential to ensuring economic operations and low total cost of ownership (TCO) independent of loadings.

To this end, APC by Schneider Electric has recently launched the MGE Galaxy 7000 range of three phase UPS which are designed to offer the highest efficiency as well as the highest power/ footprint ratio unit in its class. The series joins APC's Symmetra series of UPS systems (a component of the company's InfraStruXure solution for on-demand datacentres) which both match the stated criteria for the holistic view which is the basis for achieving both optimum efficiency and low TCO.

Meeting Efficiency Goals
Particular to the choice of UPS using criteria of efficiency is evaluation at true operating conditions. UPS efficiency is invariably quoted by manufacturers at full load, but when operating with lighter loads, efficiency drops off substantially, for example where the load is shared between UPS devices in N+N (Tier 4 Datacentre) configuration or where single devices are operated well below maximum capacity efficiency will be reduced substantially. The chart shown on the right illustrates the performance of the range alongside that of a traditional or legacy UPS unit in various load conditions.

What is most noticeable is the UPS system maintains levels of efficiency below a 30% load and generally has a ‘flatter' efficiency curve than some products of this class. This is important since rarely do datacentres or other electrical installations operate at or close to their maximum capacity. In fact research has shown, for example, that many datacentres only ever achieve 30% of their designed operational capacity due mainly to availability/redundancy mandates and the M&E engineering habit of ‘over-sizing'.  Thus claims of efficiency based on maximum load provision are like the stated maximum speed of a car, rarely a reflection of how the vehicle will be used in the real world. When using efficiency as specifying criteria, it is imperative to look at how a UPS performs under various load levels in which it is likely to operate.

The Financial Perspective
It's one thing to say that higher efficiency infrastructure equates to lower total cost of ownership, but it's obviously another to see how the numbers actually stack up. Take the example below, which compares the costs of running a 400kW Galaxy 7000 to protect a full load at 95% efficiency with that of a legacy UPS at 90% efficiency. Over a 12 year period, assuming energy prices remain static, the user could save almost £200,000. Allow 5% for inflation and the cost savings rise to in excess of £260,000, in other words the annual costs of running the Galaxy 7000 is 50% lower than an equivalent legacy UPS at £30,000.
As discussed earlier, with many UPS designed to provide the highest levels of efficiency at the highest load, the savings become more pronounced as the size of the load is reduced and efficiency starts to tail off. Therefore at 50% load, energy savings by using Galaxy 7000 in place of a legacy system are £128,664 - again, the savings are calculated without the effects of inflation. The savings are substantial with such a wide efficiency gap, but it is also true to say that even a percentage point here or there in efficiency terms particularly where the UPS are used in multiple configurations, could add up to a great deal in energy savings and therefore consequential cost reductions due to lower cooling/ventilation requirements.

Other Efficiency Criteria
APC UPS systems have been designed and manufactured for harsh environments, offering high fault-clearing capabilities, a high load crest factor and excellent voltage stability even for 100% load step changes or unbalanced loads when compared with rotary-type UPSes..
With growing concerns about the shortage of personnel with suitable skills for sophisticated datacentre and electrical environments, there is a premium placed upon ease of installation, operation, monitoring and management. For local management, the Galaxy 7000 has been designed with an intuitive interface to provide clear and relevant operational information including 5000 time-stamped events, analysis and pictograms. The unit can also be managed remotely via a number of different operational protocols and is compatible with APC remote management tools and, in a situation of datacentre deployment, with APC InfraStruXure Central Capacity and Change Management software which enables datacentre operations to monitor and project the impact of changes to the physical layer of the datacentre. Galaxy 7000 is supported by Schneider Electric Critical Power and Cooling Services maintenance services and upgrade solutions.

From an environmental perspective, in addition to the ecological advantages that are realised through higher efficiency and therefore lower emissions, the Galaxy 7000 addresses environmental issues at each stage of the production process. This is done to meet and exceed standards required by international environmental regulation including those relating to the sites at which the technology is manufactured. The series is designed with fewer electronic control boards with 91% of parts suitable for recycling in compliance with the WEEE Directive and its weight is half that of the previous Galaxy generation. The efficiency in its design and its more powerful IGBT rectifier reduces  the size of the electrical distribution system. Higher efficiency can be acheived through use of its Eco mode operation which offers up to a 97% efficiency rating.

There is great financial gain to be had by optimising levels of efficiency from ‘conspicuous consumers' of electricity such as UPS systems. But in order to take advantage, those responsible must carefully consider the demands of the load which is being protected in terms of mission criticality and system design. Strategies such as rightsizing of infrastructure will avoid waste and modular systems can help answer that need. Use of UPS with published efficiency details and which have been designed to be highly efficient even at light loads can help to reduce the operational costs, energy waste and carbon emissions with added sustainability.