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Electrical efficiency has long been a concern for data-centre design engineers. In recent years, though, increased economic, environmental and customer pressure has seen this overtaken by a need for overall sustainability.
The growing global energy transition – to a grid dominated by variable renewable generation – represents a significant opportunity for data-centre operators to not only reduce their carbon footprint, but to also improve the resilience of their power network, and of the grid they rely on for the delivery of power.
While it is to be welcomed, the energy transition will create specific challenges, such as managing variations in frequency from renewable sources, and disturbances in the grid.
Balancing the grid and maintaining frequency relies on two methods of matching supply with demand. The first of these, long-term balancing, is based on demand and generation forecasts, while the second, real-time balancing, or frequency containment, is based on real-time frequency, allowing small differences in the balance to be fine-tuned and regulated accordingly.
In synchronous generation, where traditional power-generation methods like solid fossil fuel, oil and gas are used to spin turbines, spinning mass is directly coupled to system voltage and frequency. When the grid frequency varies, the spinning mass either accelerates or decelerates and absorbs or releases energy, thus dampening the frequency variance. With non-synchronous generation, on the other hand, in which renewable energy-generation technologies like wind, solar and hydrogen fuel cells are connected to the grid through a converter, system inertia is reduced. As inertia reduces, the size and speed of frequency variations increase, and it becomes more difficult to contain the frequency – especially during large contingency events.
One obvious way to mitigate low inertia is to connect more spinning mass to the grid. The cost of running all these turbines is enormous, however. Reducing the size of large units like nuclear plants is also a very efficient means of mitigation. But nuclear power plants have long-term contracts to sell their capacity to the energy market. They need to be compensated for taking down production, and this can be hugely expensive. And while more traditional frequency containment reserves could be added to the grid, they can be slow to respond – the number required would be economically unviable.
New types of faster reserves are needed. Providing a first, immediate response to frequency barriers, for example in the form of fast reserves, is far more efficient at mitigating low inertia than traditional spinning reserves. It’s little surprise, then, that they’re becoming more widely adopted – particularly given the need for greater flexibility in the system.
Grid-interactive data centres and EnergyAware UPSs are a huge and, as yet, under-utilised capacity. Importantly, it’s not the future, it’s existing technology.
Looking ahead, there’s a real need for sector coupling, where everything that’s connected to the grid is part of the grid, providing flexibility and helping to balance the grid and mitigate the environmental problems faced by society today.
Data centres have a considerably greater amount of power infrastructure than most other buildings. Typically connected to a high- or medium-voltage grid, they contain UPSs, energy-storage devices and cooling systems, all of which provide a degree of flexibility or fast response. What’s more, data-centre power systems tend not to run with a full design load, meaning there can be excess capacity in the supply-side hardware, further increasing their capabilities to support the grid. Leveraging these existing assets can have ecological as well as economic benefits.
Compare a data-centre system using UPSs with a large grid-connected battery energy-storage system. Half of the cost of the latter comes from the batteries. The other half comes from fitting out the building itself, installing the transformers, grid connections and switchgear it needs. Using a large commercial data-centre building in which these are already available will save on costs. At the same time, as there is no need to build these additional features, the embodied carbon footprint they represent can be avoided. It’s a smart way of working that’ll have a positive impact on the environment, reducing carbon emissions outside of an organisation’s regular operations.
Running costs aside, as we move toward renewable energy, there’s a need for greater flexibility in a system so that power will still be generated, even when the wind doesn’t blow or the sun doesn’t shine. And, as we’ve seen, there’s also the challenge of managing low inertia and containing frequency during contingency events. This is where fast reserves, or dynamic containment with a technology like UPS, comes into its own.
Data-centre UPSs will often have sufficient capacity to provide the necessary response. The aim is not to replace wind power for hours or days, but to leverage the capability of UPSs to momentarily use stored energy to manage these contingency events and low inertia to ensure higher penetration of renewables to the grid, without sacrificing its reliability.
On average, data centres account for two-thirds of UPS installations in Europe. In Ireland, for example, three years of large UPS sales, at over 200 MW per year, would completely fulfil the country’s need for fast frequency reserves (FFR) – especially when you consider that the average UPS has a lifespan of 10 years. Over time, it’s predicted that data centres as a load will account for up to a third of Ireland’s grid capacity. This level of potential flexibility and fast response could easily satisfy the demand for these services.
Grid-interactive data centres and EnergyAware UPSs are a huge and, as yet, under-utilised capacity. Importantly, it’s not the future, it’s existing technology. And as the energy transition continues to progress, it represents an opportunity for data-centre operators to improve both their efficiency and their sustainability, giving back to the grid what they take out.
Click the links below to find more information on Eaton's EnergyAware UPSs or hear the full story within our on-demand 'Transform your data centre for a sustainable future' conference
