Fri, 27th Oct 2023

Powering Ireland: Why weather forecasting is key

Thursday 26 October 2023 was an interesting one for the all-island electricity grid. This article provides some insights into what occurred and how these events may become increasingly commonplace and the requirement for flexibility more critical.

Power System in Transition

Power systems worldwide are undergoing a paradigm shift as they transition away from fossil fuels and increase levels of variable renewable generation. This presents a range of challenges for power system operators who are mandated to deliver a safe, secure & reliable supply of electricity to the end customer at all times.

In Ireland, this transition is well underway with renewable generation increasing by more than 1,000% between 2001-2021(1). Today, wind is the dominant renewable energy source with more than 5.8 GW of installed wind capacity across the island of Ireland(2). With ambitious 2030 targets for 80% renewable electricity, we will continue to see a significant increase in renewable generation on our power system.

Power system operators have the difficult task of continuing to provide the same level of resilience with a system progressively dominated by inherently variable renewable generation such as wind and solar.

26 October 2023

One could be excused for not expecting any notable events on the all-island power system on Thursday 26th October, given demand and wind forecast were similar to the previous evening.

However, Grid Operators in EirGrid’s National Control Centre would have started to feel uneasy throughout Thursday as they witnessed the actual wind generation diverge from the wind forecast. Without perfect foresight, the Grid Operators are faced with a dilemma, do they call on additional conventional generation, which potentially needs hours of advance notice, on the chance they will be needed, but incur unnecessary costs to the end consumer if they are not? Or, do they hope that the wind will pick up and start to track back towards the wind forecast and they will have sufficient MW to meet the evening peak?

As the evening peak approached, the situation had deteriorated. By 4pm the actual wind generation was c. 1 GW below the wind forecast (1 GW represented c. 20% of all-island demand at that time).

Figure 1 – Source: EirGrid SmartGrid Dashboard

To compound matters, a conventional plant that was due to come online to help meet the evening peak failed to start, or tripped, leaving the Grid Operators without another c. 250 MW. Thankfully, Grid Operators were able to call on other providers to help alleviate the situation, and Demand Response played a key role.

133 MW of demand response was called on to meet the evening peak on Thursday 26th October including many commercial and industrial sites within the VIOTAS portfolio. This type of flexibility, with fast response times, is of high value to the power system.

Evolving role of Demand Response

Historically, Demand Response was only called on for a relatively small number of hours each year, to support the grid during the classic winter evening demand peaks. However, in recent years, the role of demand response has evolved. We have seen demand response called on in summer months (when system demand is typically at its lowest) as well as during morning load rises.

As we accommodate more renewables, the flexibility provided by Demand Response offers a solution to challenges such as uncertainties in wind forecasts or ramping which will become more pronounced as the levels of fossil fuel-based generation decreases. This is yet another example of the vital role this low-cost, low-carbon technology can play in the power system of the future.


Managing a system with high levels of renewable generation is an impressive feat, especially a relatively isolated power system. Managing such a system at times of low, or rapidly changing, levels of renewable generation and still ensuring the lights stay on regardless of unforeseen events transpiring is what makes Ireland’s power system truly world leading.

While unpredictable weather forecasts can result in an umbrella and suncream both being brought on the same trip, weather forecasts also have a significant impact on the operation of the all-island power system. Ireland’s often unstable weather conditions are particularly challenging to forecast, particularly the exact timing of the frontal systems associated with the Atlantic weather systems which typically pass overhead. With an electricity system so dominated by wind generation, weather forecasting has become even more central to managing the grid.

In order to successfully manage any power system with high levels of variable renewable generation, technologies like demand response must be part of the solution.

VIOTAS would like to thank our customers who continue to play a vital role in providing the highly valuable flexibility that enables the grid to accommodate ever increasing levels of renewable generation. VIOTAS would also like to extend our gratitude to EirGrid, particularly the staff of the National Control Centre, who seamlessly manage days like this so most of us are unaware and unimpacted.

(1) Energy-in-Ireland-2022.pdf (
(2) Wind-Installed-Capacities.png (806×1046) (