Significant progress has been made in recent months towards EirGrid’s 2030 goal of being able to operate the power system with up to 95 per cent renewables at any one time.
That’s the level required for the system to meet the government’s target of having an average of 80 per cent of the country’s power supplied by renewables by that date.
“We have been on a journey over the past decade in respect to the level of renewables on the system,” explains EirGrid head of future operations Eoin Kennedy.
“From our perspective as a transmission system operator [TSO], when we connect wind and solar it changes the characteristics of the system and presents challenges. We have made huge strides in operating with higher levels of renewables and have achieved 75 per cent. That’s at the forefront internationally. Only a handful of TSOs around the world have achieved that.”
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To put that achievement in context, a decade ago the upper limit was 50 per cent. Since then, the organisation has run a series of projects to increase limits in increments of 5 per cent.
Among the challenges to be faced is the fundamental difference between renewable power and the electricity generated by conventional power stations. The grid is designed to operate at a frequency of 50hz and, conveniently, conventional power stations use spinning turbines to generate electricity at that frequency. Renewable power, on the other hand, needs to be converted electronically to be used on the grid.
System operators therefore need to keep the grid in balance and prevent sudden or rapid changes in frequency. That requires inertia, which has been provided by conventional power stations effectively as a byproduct of their electricity supply.
“Inertia is the glue that holds the system together,” Kennedy points out. “It slows down frequency changes.”
That requirement for inertia entails a need for a certain level of conventional generating capacity on the system at any one time.
“A year ago, the requirement was for five conventional units on the system in the Republic of Ireland,” he adds. “We have now reduced that to four. When system conditions allow, that frees up space for additional conventional generation.”
During a 10-month trial, between May 2023 and March 2024, those conditions were met for about 11 per cent of the time. Naturally, at times of lower renewable generation availability, a larger number of fossil-fuelled generators will still be required to operate to meet power demand.
Looking forward to 2030, Kennedy explains that the minimum level will have to be reduced still further to accommodate peak levels of 95 per cent renewable power on the system. The solution there is to have the required inertia services delivered by non-generating providers.
“We ran a procurement process for low-carbon inertia services [LCIS] to offer us the non-generating inertia services required to further reduce the minimum number of conventional units on the system,” says Kennedy.
“Earlier this year we awarded four contracts for renewable energy integration technologies, called synchronous condensers. They look like a motor with a large flywheel attached. They consume a small amount of power but provide a large amount of inertia. They can provide a certain amount of reactive power as well.”
The new condensers will be located in Counties Sligo, Galway, Kerry and Wexford and it is anticipated that all of them will be operational in either 2027 or 2028.
“We are doing lots of other things as well,” Kennedy adds. “We are working collaboratively with Soni in Northern Ireland on a number of programmes. For example, in advance of the new Greenlink interconnector between Ireland and Wales going live, we are running trails to enable us to increase the rate at which the flow of electricity across the interconnector can change.
“The current limit is 10Mw per minute and we are running a trial to increase that to 15Mw per minute for the island of Ireland. By allowing the flow to change more rapidly we will enable the interconnector to better capture the market conditions on both sides.”
Looking forward, the next key thing we are studying is the impact of moving to 80 per cent renewables on the system.
“We are trialling that at the moment and looking to make the change permanent soon. We will also look at a further phase of LCIS procurement next year. It’s all about the continued development of the grid.
“Collectively, all these changes allow us to operate the system with higher levels of renewables generation. It all feeds into the 95 per cent goal. But a lot of jigsaw pieces have to come together to make it happen. We are working very closely with Soni, the distribution system operators, industry and other market participants on this and they will all contribute in different ways.”