Improving Operational Efficiencies of UPS systems Reduces Energy Consumption

13 Nov, 2018 | Articles

Availability of power is essential in today’s ever-increasing digital world and IT business critical environments. As well as the obvious interruption to power to the critical load, power outages can also potentially cause physical damage to equipment and essential data can become corrupted or inaccessible leading to issues keeping the business going long after the lights have come back on. Concerningly, it has been reported that power outages in the UK are on the increase.

The solution is to implement a reliable uninterruptible power supply (UPS) and in today’s increasingly competitive environment maintaining operational efficiency is essential to keep running costs down.

Over the last 10-15 years the biggest driver for UPS development has been efficiency. By utilising a more efficient UPS unit, and units within larger resilient systems, minimises OPEX, reduces carbon footprint attracting Government funded tax incentives, and aids Corporate Social Responsibility (CSR). So what are the main considerations when considering an efficient UPS solution?

Firstly, all manufacturers will claim very impressive efficiency figures for their UPS units, initially the marketing “glossies” focussed on a maximum efficiency value with the UPS operating at 100% capacity, although in reality a UPS unit/system never operates at such a figure. A typical single UPS unit may operate around 50-70%, although even this is generous. However, within a resilient system offering redundant parallel UPS units the individual load capacity is often much lower, 20-30% is common. Therefore, it is important to look at the efficiency figures at the range in which the UPS will be operating in. Transformerless UPS units greatly aided this drive with their flat efficiency curve down to 25% capacity but even these tailed off quite significantly below this figure. The latest generation of UPS system are now achieving 95.5% efficiency at load capacities of only 10%! An amazing success when compared with legacy systems of only a few years ago. A good source of information is the Energy Technology List, a completely independent list which continues to raise the standards of UPS efficiency, look to see if your UPS is listed.

An inefficient UPS system generates heat, increasing your UPS efficiency decreases the cooling requirement to remove this heat.

Replacing legacy UPS systems has become a powerful argument when comparing the potential OPEX saving with installing the latest more efficient UPS units. One such recent replacement was on a traditional multiple unit system, offering N+1 resilience, comprising of three 250 kVA UPS units running in parallel.

The site load averaged only 200kVA. With all UPS units sharing this load, each individual unit was supporting 67KVA and therefore operating at 27% of its capacity. As the units were some 15+ years old, and of the legacy transformer-based design, the overall electrical efficiencies were measured at only 80-85% and you have to add the heat losses which were significant. .

By calculation the savings in OPEX was an amazing £62,000 per year, a CO2 reduction over 5 years of > 850 tonnes with a carbon neutral offset of some 1,350 trees!

So, what do we need to look at when considering a UPS system with regard to operating costs. The first step is to find a system with the highest efficiency for online operation.

As systems are not run at 100% load all the time, check the UPS unit reaches peak efficiency when operating at your own sites expected load, taking into account the resilient nature of the topology, ie multiple UPS units operating in parallel. Select a technology that offers a flatter efficiency curve across the widest load range. CENTIEL’s UPS technology is 95.5% efficient even at l0% load.

So, let’s get back to our 3 x 250KVA example and it’s replacement system. With a new modular system based on CENTIEL’s Distributed Active Redundant Architecture (DARA), with twelve 50kVA modules installed, each module would be at 33%, still quite a low figure but the solution was also dictated by the existing electrical infrastructure available.

At these values of load the Centiel system was at 96.75% efficient. Over five years, the calculated OPEX savings are >£300,000! With the Modular concept ongoing maintenance costs are also minimized further reducing the total cost of ownership and crucially there are no single points of failure. Significant savings on operating and maintenance costs, mitigation of risk, with the highest availability of power protection.

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