John Byrne, Managing Director Ireland at Enel X, and Evan Barker, Manager, Facilities Engineering at Digital Realty, explain how leveraging data centre UPS through dynamic frequency response is supporting Ireland’s renewable energy transition. 

Electricity grids of the future will depend on the evolving relationship model between user, technology and local regulations. This evolution unlocks a massive opportunity for businesses of all types – but especially data centres – to use their energy storage assets in new ways that add commercial value, resilience, and improved sustainability, for their organisation and for the grid.

Grid stability – a growing challenge

Ireland has emerged as a major hub for data centre activity, attracting both domestic and international companies. The sector is an important source of income for the country, with revenue projected to reach US$1,198m in 2024. 

At the same time, the sector is coming under criticism for its heavy use of electricity – consuming up to 18% of the country’s electricity in 2022. Capacity constraints on the grid have caused so much concern that there has effectively been a moratorium on the connection of new data centres in the Dublin area until 2028. 

This is coupled with Ireland’s Climate Action Plan’s ambitious target for 80% of the country’s electricity to come from renewable sources by 2030. Ireland is well on the way to meeting this target with over 35% of its power currently generated from renewable sources. 

Renewable energy sources are more sporadic than traditional carbon fuelled power sources. Integrating them makes the grid less stable. Variations in power production cause small shifts in the balance between supply and demand on the grid that can be seen as frequency fluctuations.  

Ireland’s secure and sustainable electricity policy

EirGrid, the electricity Transmission System Operator (TSO) in Ireland, has designed its ‘Delivering a Secure, Sustainable Electricity System’ (DS3) with the specific aim of creating the right conditions to safely and securely add more renewable energy to the Irish power system – without having to rely on traditional power stations for backup.

DS3 works by balancing the frequency of the grid as it fluctuates in response to variations in the quantity of renewable energy generation. If the frequency of the grid can be maintained at 50 Hz, more carbon-free electrons from renewable generation can be added to the power transmission lines feeding businesses and homes around the country. 

Frequency response programmes, including DS3, require standby energy assets that can react to grid signals within seconds or even milliseconds. This is where data centres come in. Battery energy storage systems (BESS) are a highly versatile form of storage found in the Uninterruptible Power Supply (UPS) of most data centres. The main purpose of the UPS is to provide power conditioning and backup electricity for the servers. 

UPS systems – a fast acting remedy 

With response times below 0.5 seconds, UPS systems are fast enough to prevent data centres from losing power during an outage. Data centre-scale UPS systems typically store enough energy for a few minutes of backup power. After providing backup power, UPS systems can recharge their batteries from the grid.

The availability required by the data centre determines the capacity of the battery and generator installation to ensure that the facility keeps the IT load going, no matter what. This results in often unused capacity that, with the right tools, can be made available to the grid to help it recover from an outage or even prevent one occurring. 

A collaboration between Enel X and Digital Realty is implementing this approach in Europe, in what is known as grid-interactive UPS. 

Enel X installed hardware at Digital Realty’s data centres to both meter the UPS and send power requests to the UPS during times of grid disturbance. These devices have been designed and built to meet the requirements set out by the TSO. Grid compliance testing ensured that the system worked as expected following its installation.

In order to provide frequency balancing support to the electricity grid, the data centre batteries had to meet essential criteria: 

• 20 millisecond event data
• GPS time synchronisation of +/- 2 ms
• 1 second real-time data
• 5 second data latency
• Response time <2 seconds.

How data centres can reduce grid stress and costs

Digital Realty is now using batteries on its installed UPS systems to give back to and support the grid through dynamic frequency balancing services. Whenever minute fluctuations in grid frequency occur, its UPS batteries are enacted to remove load from the grid in sub-2-seconds. This supports the constraint on the grid and allows the frequency to reset to its normal operating frequency of 50 Hz, and avoids the need for taxpayers’ money being used to have power plants on standby. 

The project is setting a scalable precedent for data centres and other large energy consumers to use their UPS to bolster the electricity grid they depend on, becoming an intrinsic part of Ireland’s electricity system and facilitating the country’s transition to renewable energy.

By creating a solution that was compliant with EirGrid’s strict programme rules, the data centre batteries can provide frequency balancing support to the electricity grid. This turns a largely idle asset into an active facilitator that helps to create the grid necessary to achieve renewable targets.

A triple win 

There are benefits to the data centres through this approach in addition to becoming good grid citizens. As well as supporting the grid through frequency balancing services, the grid-interactive UPS can help data centre operators become more energy aware and use their UPS to support demand management programmes with the local grid – also known as ‘peak shaving’. 

In this way, data centres can lower their energy consumption by switching to on-site power generation or using stored capacity in batteries. This helps to avoid grid outages and reduce overall energy cost, with a positive impact on a facility’s Total Cost of Operation (TCO) – which is primarily led by the cost of energy. 

A study by Baringa considers that if all data centres utilised their UPS as grid-interactive UPS, the need for peaking power plants that rely on fossil fuels would be negated, saving 1.5 million tonnes of CO2 annually for the Irish power sector. For context, this is equivalent to 2.47% of total CO2 emissions in Ireland in 2022, or the annual carbon emissions of more than 700,000 private cars on Irish roads. Without the need to burn fossil fuels to provide these frequency balancing services, the cost passed on to end consumers for electricity could also be reduced with estimated savings of €270 million per year. 

Rising to a global challenge 

As other countries transition to a greater reliance on renewable energy, they are encountering a similar situation to the one in Ireland. In the UK and Europe recent grid modifications and code changes have been introduced to accommodate more variable renewable energy.

Such reforms are enabling the innovative use of data centre battery assets to support electricity grid stability – as homes and businesses around the world make the transition to net zero.