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Ireland’s first 4-hour battery project indicates market evolution, challenges remain


The first 4-hour duration battery storage project to be built in Ireland exemplifies both the challenges and opportunities of the country’s growing and evolving market.

Norwegian state-owned energy company Strakraft is developing a 20MW/91.2MWh battery energy storage system (BESS) project at the site of its Cushaling wind farm in County Offaly, in the midlands of the Republic of Ireland.

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Battery storage technology for the project is being provided and integrated by Fluence. The company’s growth and market development director for the EMEA region, Julian Jansen, told that Ireland has been among the markets to see the fastest evolution, and most diverse set of BESS assets built.

“When we look at the island of Ireland, it really is an interesting testbed for the energy transition as a whole,” Jansen told

“You have this island with limited interconnectivity, very high wind penetration, increasing electricity demand, driven, in particular, by the data centre industry, and then [grid] congestion issues between the west of Ireland, towards the Dublin region.”

Long-duration batteries help IPPs balance generation portfolios

Stakraft Ireland head of grid services Rory Griffin has written about the project for the latest edition of PV Tech Power (Vol.39), which is out now and available to Premium subscribers.

The article details both the technical aspects of the project and the market dynamics that led Statkraft to become a first mover on a grid that has typically seen systems of 0.5-hour to 2-hour duration built, tied to opportunities in the DS3 grid services market.

The longer-duration project at Cushaling will enable renewable energy sources in the midlands to be stored at times of low demand and outputted at times of peak demand, reducing the need for costly curtailment.

This is important for companies like Statkraft which are building up portfolios of solar PV and onshore wind on the island of Ireland. Energy stored in batteries can be traded through the Integrated Single Electricity Market (ISEM).

Fluence’s Jansen said that while he cannot comment on how Statkraft’s trading portfolio is operated, independent power producers (IPPs) that own large portfolios of generation are seeing energy storage assets as a useful tool for managing the imbalance cost of those portfolios.

Jansen said this is being seen in Ireland already but is also likely to characterise the Great Britain (GB) market (note: the Irish grid includes Northern Ireland, part of the UK, as well as the Republic of Ireland) and is also being seen in other European markets.

“There’s a clear interest towards that and I think that often means you may start seeing longer-duration assets being developed in a merchant context because they’re not looking at it from an asset perspective,” Jansen told

“They’re looking at it from a portfolio perspective, which is a very different investment approach from what we may have seen historically in the UK, where it’s been very much a single-asset type of assessment.”

Uncertainty around future direction of market

In addition to trading, the project will provide ancillary services to transmission system operator (TSO) EirGrid, while Cushaling also has in place a 10-year capacity market contract.

However, each of these three available revenue streams: ancillary services, energy trading and capacity market, come with attendant challenges, Griffin wrote in his PV Tech Power piece.

While DS3 has driven rapid market development to date, leading to about 800MW of 0.5-hour, 1-hour and 2-hour systems being deployed, the regime was introduced in 2017 and the market is now “overheated”.

It is now unclear what will happen to tariff rates for ancillary services, which have already been cut in response to that market saturation, at least until April 2026, when DS3 is due to be replaced with a new regime, the Future Arrangements System Services (FASS) market.

The Statkraft team decided to build a 4-hour duration asset meanwhile based on the capacity market design, which incentivised longer-duration storage through de-rating factors in place at the time of the contract’s award in 2020.

Since then, the de-rating factors have halved, and it is unclear if future opportunities for new-build storage with 4-hour discharge duration will be present. That means capacity auctions “are no longer providing the revenue certainty required to make an investment decision,” Griffin wrote.

As with its British neighbours, the Irish government has been holding a consultation on the role that long-duration energy storage (LDES) can play in the country’s energy transition from fossil fuels and in providing energy security and stability of supply.

Griffin wrote that Statkraft will be awaiting the next step in that consultation, the publication of a recommendations paper to policymakers.

(De-rating factors for energy storage in the Capacity Market in GB have also been falling, and the electricity market operator for GB, National Grid ESO, is currently re-assessing them.)

‘One-size-fits-all’ doesn’t work for energy storage

Statkraft’s BESS at Kilathmoy wind farm, commissioned in 2020, was the first to play in the DS3 market. Image: Statkraft.

Fluence’s EMEA VP for sales and market development, Brian Perusse, noted some of the project design differences that come with stepping up duration from anything up to 2-hour, to double that.

“The duty cycle and lower C-rate of longer-duration storage systems are less strenuous for the battery cell,” Perusse told

“However, the engineering, controls, data collection, and operational aspects of the systems become more complex and important. For example, meeting the speed of response requirements of DS3 and inertia-like response with longer-duration storage is more challenging from a controls and design perspective.”

While Fluence has delivered 4-hour duration projects in other markets to date, perhaps most notably California where the company was behind some of the earliest projects in the multiple megawatt-scale, a one-size-fits-all approach does not work for energy storage, Perusse said.

“Each market is unique and has its own requirements, so storage needs to be tailored to those market-specific needs. Much of the hardware is similar across markets, so, to the casual observer, the systems look the same,” Perusse said.

“However, high-performing systems are localised to ensure they operate at the best level in each of the markets they operate. This includes different software controls, different types of electrical equipment, and various commercial structures.  A one-size-fits-all approach in storage leaves money on the table for the customer.”

That localisation piece has already been evident in Fluence’s projects in Ireland, the company’s VP said, highlighting that the DS3 market on introduction had “among the fastest and most stringent response times” among ancillary services opportunities.

Another aspect of the project’s technology is its co-location with wind power. It is still more common to see energy storage deployed together with solar PV, which Perusse said is often due to the commercial or regulatory benefits in many markets of that combination.

However, Perusse notes that the first energy storage project he worked on, commissioned in 2011, was a co-located wind and battery project, and going forward, Fluence expects the case for co-located wind and storage in Ireland to grow stronger.

Around 8.5% of all wind power generated on the island in 2022, around 1,280GWh, was curtailed according to EirGrid’s own Annual Renewable Energy Constraint and Curtailment Report.

Both Perusse in his interview, and Starkraft’s Rory Griffin in his article said that one of the key challenges for wind and BESS co-location is that current regulations make it difficult for renewable energy and storage systems to share the same grid connection.

Regulators are aware of this and other challenges that have limited opportunities for hybrid resources of this type to date, and Perusse said Fluence is “hopeful regulators are working to solve these shortly”.

Read Rory Griffin’s article, ‘The benefits of longer-duration storage and energy project co-location’ in the newest edition of PV Tech Power (Vol.39), out now and included in your ESN Premium subscription.

Solar Media Market Research’s ‘Republic of Ireland Battery Storage Project Database Report’ provides comprehensive details across the rapidly growing pipeline of battery storage projects across the Republic of Ireland and Northern Ireland.

12 November 2024
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