Preliminary data published by EirGrid, Ireland’s transmission system operator (TSO), shows that Northern Ireland’s total dispatch down rate – the percentage of renewable energy curtailed and constrained – was 25.5% in 2024.
Wind was the main contributor to this figure, but even when it was taken out, the numbers for solar show a doubling of dispatch down rates between 2023 and 2024.
In 2023, Northern Ireland’s solar curtailment was 7.9%; in 2024 it more than doubled to 16.9%. Most of this percentage – 15.6% – was turned down due to constraints.
The solar dispatch down rate for the Republic of Ireland was 5.3%, and unlike Northern Ireland, the region mostly turned down solar due to curtailments as opposed to constraints. Just 1% of the total 5.3% was attributed to transmission constraints, whereas the rest was all curtailed.
Across the entire country, more than 7% of solar was dispatched down during 2024, down slightly from 2023 levels of 9.1%. Of this, 3.9% was curtailed and 3.2% was due to constraints.
“These numbers very much reflect the differences in wind dispatch down as well between Ireland and Northern Ireland,” said Fei Wang of Green Collective, a data and research company focused on the Irish grid. “Wind dispatch down in Ireland was equally due to curtailment and constraints, while wind dispatch down in Northern Ireland was overwhelmingly due to transmission constraints.”
Wang added that the usual reason cited for curtailment tends to be the system non-synchronous penetration (SNSP), but 30-minute data released by EirGrid show SNSP was only responsible for 1% of all dispatch down across the island in 2024.
This is essentially the limit of how much inverter-based generation like wind and solar the grid can take at a time. The limit currently sits at 75% in Ireland, which according to Wang, is “one of the highest if not the highest in the world”.
This means that even if renewable energy could generate more power, it cannot be used beyond this limit. Fossil fuels are easier to keep at the grid’s standard frequency and are not subject to curtailment.
“The most likely reason behind curtailment is high frequency or minimum generation; this is used when the system attempts to alleviate an emergency high frequency event or in order to facilitate the minimum level of conventional generation on the system to satisfy reserve requirements,” Wang explained. “When I look at time periods with significant curtailment, it's almost always during hours with lower demand – mid-day to early afternoon and in the middle of the night, usually. To me, this indicates renewable energy is curtailed not because the system has reached the limit of taking on wind and/or solar, but because demand is not high enough. This also shows huge opportunities to use flexible demand to reduce renewable curtailment in Ireland.”
Separately, energy analyst Cornwall Insight has cited wasted and unused renewables as a major contributing factor in the likelihood that Ireland and Northern Ireland will miss their respective 2030 power emissions targets.
Both jurisdictions are on course to miss their targets by up to 20%, the analyst reported in its SEM Benchmark Power Curve Report.
Ireland is targeting a 75% reduction in electricity emissions by 2030. However, Cornwall Insight forecasts it is only set to reduce power emissions by 50% by the end of the decade.
The analyst’s forecasts for Northern Ireland showed it is likely to miss its emissions targets by 20%. The government set a target to reduce emissions by 73% by 2030, but it is only likely to achieve a reduction of around 50%.
Tom Musker, modeling manager at Cornwall Insight, said that while the potential is there for Ireland and Northern Ireland to reach their emissions targets, “serious investment in grid infrastructure and storage” needs to happen.
“While both jurisdictions are on track to make sweeping changes to their energy systems, as coal and oil-fired generators make way for cleaner energy, this alone will not be enough to reach the ambitious emissions target,” he added. “It’s clear while renewable growth is going in the right direction, dispatch down means it’s just not being used to its full potential. The clock is ticking, and both the governments and other stakeholders will need to think long and hard about investment in the energy system if they don’t want to see targets slip further out of reach.”
Unused renewables is a problem in other European markets such as Cyprus, which curtailed 29% of its total renewable energy in 2024. Curtailment is also an ongoing issue in the Netherlands and Spain.
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