Energy Efficiency in Uninterruptible Power Supply Design

By: Alison Campbell

Uninterruptible Power Supply users - and data centres in particular - have never been under greater pressure to manage and reduce energy consumption. On one hand there are ever-stricter environmental requirements and the need to be seen as a good corporate citizen; on the other, the commercial imperative that balances increasing data centre performance with the balance-sheet-led requirement to cut operational costs.

Increasingly green UPS technology

Throw in a few misconceptions about Uninterruptible Power Supplies and the scene is set for an epic debate - with the integrity and performance of the datacentre (and its green credentials) on the line if the wrong approach to energy efficiency and UPS design is taken. In one corner: a small but vocal minority advocating fresh air cooling, UPS-free data centres and higher ambient temperatures (thereby reducing air-conditioning requirements); in the other, the supporters of increasingly green UPS technology as they embrace the latest energy efficient hardware and celebrate a tradition of close co-operation with a trusted UPS manufacturer.

Four main energy efficiency issues affect UPS selection: the energy needed to power them; the way they draw energy; and their effect on upstream supplies and the management of consumables such battery sets and switchgear. The best of modern UPS design offers tangible improvements in all three areas, along with an ever-improving carbon footprint. It's just as well, because if data centre operators agree on one thing it is the importance of reducing power consumption.

The downside of non-UPS data centre operations

Those who argue against proven UPS technology claim that repeated AC to DC switching raises power consumption. Another minority advocate only fresh air-cooling (no power-hungry, server-room air-con) and even the conversion of data centres to DC-only in the interests of energy efficiency.

Unfortunately, this view overlooks possible damage, and almost invariably accelerated wear-and-tear, to sensitive datacentre hardware, fans, consumables and battery sets. That's the likely consequence when equipment is forced to work harder in raised temperature and humidity - or run on a non UPS-unconditioned power supply. How much costly downtime can any business carry? And that's after the potentially massive costs of installing the unfeasibly large quantities of copper wire a DC-only call centre would require.

Rather than taking these radical steps, the intelligent route forward appears to be that which the majority of enlightened data centre operators already follow. A proven route, whereby hugely experienced UPS manufacturers develop increasingly energy efficient devices such as the latest Riello UPS the specification, design and installation phases to tailor correctly-sized UPS solutions without expensive (and power-greedy) over-specification.

Handling the latest high-density servers

It's a fact. As well as reducing electricity consumption, thoughtful UPS design (eliminating, for example, the need for over-specification of power-hungry air-conditioning) supports end users' redefined energy efficiency and environmental objectives. What's more, the latest energy efficient UPS have improved ability to handle the latest high-density servers required by those ever-more-demanding data centre customers

With the latest zero-impact designs, UPS such as Multi Plus, demonstrate low input current distortion, reducing the need for dramatically oversized supply, such as generators and upstream switching. What's more, the latest systems give a near Unity power factor sine wave, again leading to less wasted energy. It all adds up to lower carbon and physical footprints (.26sqm at 20kVA for Multi Plus) - the latter allowing more revenue-earning high-density servers to be fitted into floor space that would previously have been required by older UPS.

Utilising a UPS supplier's energy efficiency consultancy capability

There's one final aspect of UPS energy efficiency that's easily overlooked, but that a suitably experienced manufacturer can offer great help with. While it may be tempting to explore esoteric datacentre solutions for tomorrow's energy efficiency improvements, a more immediate benefit would come from utilising a UPS supplier's energy efficiency consultancy to improve understanding of current and future requirements. Only then is it truly possible to realize the low carbon footprint, high-density data centre of the future.

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