Is Data Centre Energy Efficiency Mission Impossible?

Modern data centres consume huge amounts of energy. One recent report estimates that they will consume one-fifth of the world’s electricity by 2025[i]. UPSs, as major equipment items, contribute significantly to this demand; accordingly, any strategy that improves their energy efficiency will have a major impact on both sustainability and cost-saving within data centres.

Fortunately, various techniques are available to optimise UPS operating efficiency under all conditions, as demonstrated in modern, modular UPSs like Kohler Uninterruptible Power’s new Kohler MF1500 DPA.  Exceptionally resilient, flexible and scalable to 6MW, the modular new UPS offers best-in-market VFI mode energy efficiency.

When double conversion on-line UPSs first appeared in the seventies, they used transformer-based designs. However, advances in power semiconductor technology have facilitated a general industry move towards transformerless solutions. This has brought several advantages, including some related to efficiency.

Firstly, the topology is inherently more efficient. Even at optimal, near full load conditions, transformer-based designs remain well below 95 percent – and as the load reduces towards 25 percent, efficiency approaches just over 85 percent. By contrast, the MF1500 DPA can achieve efficiencies up to 97.4% VFI, reducing environmental impact, optimising PUE measures and delivering significant financial savings in energy and cooling costs.

However, the benefits extend further; the considerable size and weight reductions achieved by transformerless designs mean that complete UPS solutions can be implemented as small, rack-mounting modules rather than as large, monolithic units.

This comprises the UPS supporting, say, a 500 kW load; it would use two of its 250 kW modules – or three, to provide N+1 redundancy. Then, if the load increases, incrementing the UPS’s capacity by sliding in another 250 kW module (vertical scaling) is cost-effective, easy, and can be done without even interrupting power to the load. Further capacity can be provided by horizontal scaling, i.e. adding more racks in parallel.

Note that both benefits – redundant capacity and scalability – are achieved with minimal excess capacity, space and cost, due to the modules’ granularity.

By contrast, a monolithic system typically has to be significantly oversized for future-proofing. Additionally, N+1 redundancy must be implemented using two complete systems, so neither can ever be more than 50 percent loaded even in the best case. These factors force the monolithic system to work with low loads, where efficiency drops away sharply.

Designed with a clear goal in mind, the MF1500 DPA is designed to define that reliability does not require excess, and high power can exist alongside efficient use of energy. The new system combines proven Decentralised Parallel Architecture (DPA™) technology with the latest advances in components and software. This includes high performance materials for the coils core and its smart mechanical cooling design for booster and inverter sinks, reducing heat loss and extending the component lifetime.

To meet ever-increasing pressure to curb power consumption, UPS users must avail themselves of every technique to improve energy efficiency. Their best option is to choose a UPS that not only benefits from modern, modular transformerless topology, but also maintains high efficiency levels under all load conditions and has high quality energy efficient components.

To give an example of the likely cost saving, in a 1.5 MW installation, over 10 years the 0.7% extra efficiency of the MF1500 DPA versus a competitor at 96.7% can save over SG$240,000 in electrical and cooling costs.

A consultation with an experienced supplier like Kohler Uninterruptible Power is always recommended, as they can advise on the options and suggest optimum solutions for energy efficiency.




Originally posted for Mission Critical Power. February 2021

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