As Ireland continues its transition to a cleaner electricity system, renewable generation is playing an increasingly significant role in meeting demand. Wind energy now supplies a substantial proportion of Ireland’s electricity, with ever greater volumes of renewable generation connecting to the system in the years ahead.
However, as renewable penetration increases, so too does the challenge of dispatch down. While often discussed within the electricity sector, dispatch down remains a relatively unfamiliar concept to many outside the industry, despite its growing importance for consumers, investors, and policymakers alike.
What is Dispatch Down?
Dispatch down refers to occasions when renewable generators—primarily wind farms—are instructed by the Transmission System Operators (TSOs), EirGrid and SONI, to reduce their electricity output below what they could otherwise generate.
This occurs even when sufficient renewable resources, such as wind, are available. Rather than being driven by a lack of generation, dispatch down reflects the operational realities of maintaining a secure and stable electricity system.
Dispatch down consists of two distinct elements:
- Curtailment, which occurs when there is more renewable generation available than the electricity system can safely accommodate, even if there are no network constraints. This is typically driven by system-wide operational requirements, such as maintaining sufficient system stability, frequency control and minimum levels of synchronous generation.
- Constraint, which occurs when electricity cannot be transported from where it is generated to where it is needed because of limitations on the transmission network. In these cases, renewable generation may be reduced even though there is demand elsewhere on the system.
As renewable generation continues to grow, effectively managing both curtailment and constraints is becoming increasingly important to delivering Ireland’s climate ambitions.
Why Does Dispatch Down Matter?
At first glance, dispatch down may appear to be an unavoidable consequence of operating a power system with high levels of renewable generation. However, it carries significant implications across the electricity sector.
Lost Renewable Energy
Every megawatt-hour of renewable electricity that is dispatched down represents clean, low-carbon generation that could otherwise have displaced fossil fuel generation. While dispatch down is sometimes necessary to maintain system security, reducing its occurrence enables greater utilisation of renewable resources which, as discussed in our previous articles, is pivotal in bringing down electricity prices through what is known as the merit order.
Increased Costs for Consumers
Dispatch down also has financial implications. Where renewable generation is reduced, the electricity system often needs to rely on alternative generation sources to meet demand and maintain operational requirements. This can increase the overall cost of operating the system.
In addition, depending on contractual arrangements and market rules, renewable generators may receive compensation when instructed to reduce output. These costs are captured in the imperfections charge that is levied on suppliers and ultimately passed down to consumers.
Why Grid Investment Matters
One of the principal drivers of dispatch down is the ability—or inability—to transport electricity around the network. Ireland’s renewable resources are concentrated in particular regions, while electricity demand is often located elsewhere. Where transmission infrastructure is insufficient to transfer this power, renewable generation may need to be constrained despite strong demand elsewhere on the system. Investment in transmission infrastructure is therefore fundamental to reducing dispatch down.
A Whole-System Approach to Reducing Dispatch Down
Recognising the growing importance of this issue, both EirGrid and SONI have placed significant emphasis on identifying practical measures to reduce dispatch down while maintaining the safe and secure operation of the electricity system. This requires coordinated action across planning, network development, market design and operational practices.
Through their respective Dispatch Down Working Groups, the TSOs continue to engage closely with generators, suppliers, technology providers, and other industry stakeholders to identify opportunities for improvement and to provide regular updates on the progress of their solutions currently under development.
Current areas of focus for the TSOs include:
- Optimising how the system is operated. EirGrid and SONI are continually reviewing operational policies and control room practices to determine where renewable generation can be safely accommodated without compromising system security. These changes are evidence-based and undergo extensive technical assessment and operational trials before implementation.
- Unlocking greater system flexibility. Greater flexibility allows the system to make better use of renewable generation during periods of high output. This includes exploring new flexibility services, increasing the role of storage technologies and ensuring operational reserves can increasingly be provided by low-carbon technologies where appropriate.
- Deploying innovative network technologies. Technologies such as Dynamic Line Rating (DLR) can increase the amount of electricity existing transmission lines are able to carry by using real-time weather and operating conditions rather than fixed seasonal assumptions. This enables network capacity to be utilised more efficiently and can help reduce renewable constraints before major network reinforcements are completed.
- Procuring new low-carbon system services and storage. New procurement programmes, including Low Carbon Inertia Services (LCIS) and long-duration energy storage, aim to provide many of the system stability services traditionally supplied by conventional generators. Over time, these technologies can reduce the need to keep conventional generation online during periods of high renewable output, allowing more renewable electricity to remain on the system.
- Continuing strategic investment in network infrastructure. While operational improvements can deliver meaningful benefits, long-term reductions in dispatch down will ultimately depend on continued investment in transmission infrastructure. Projects such as the North-South Interconnector, together with wider transmission reinforcement, will increase the network’s ability to transport renewable electricity to where it is needed, reducing bottlenecks and supporting greater renewable integration.
Collectively, these measures seek to maximise the amount of renewable electricity that can remain on the system while continuing to uphold the high standards of security and reliability upon which consumers depend.
EAI Recommendations
The EAI welcomes the collaborative work being undertaken by EirGrid and SONI to reduce dispatch down and believes continued engagement with industry will be essential to delivering long-term improvements.
Key priorities include:
- Strengthening industry engagement through structured processes that enable market participants to propose and work on solutions to specific network issues.
- Increasing transparency around network developments, outage planning, transmission upgrades, and longer-term challenges.
- Continuing to update dispatch tools to provide participants with greater visibility of dispatch decisions and allow for the scheduling and dispatch of newer technologies.
- TSO support and facilitation in areas such as energy storage, hybrid projects, data centres, private wires, electrification of heat and transport, and network tariffs.
- Maintaining momentum on the Operational Policy Roadmap, with clear communication on progress and future milestones to provide certainty for industry investment.
Looking Ahead
Dispatch down is likely to remain an important feature of Ireland’s electricity system as renewable generation continues to expand. In the short term, some level of dispatch down will remain necessary to ensure the secure operation of the grid. However, its long-term trajectory is not fixed.
Continued investment in electricity networks, greater deployment of energy storage, advances in network technologies, and ongoing collaboration between system operators and industry all have an important role to play in reducing dispatch down over time.
As Ireland progresses towards a net zero electricity system, success will depend not only on building more renewable generation, but also on ensuring that as much of that clean electricity as possible can be delivered to homes, businesses, and industry. The ongoing work of EirGrid, SONI, and industry stakeholders demonstrates a shared commitment to achieving that objective and ensuring that Ireland’s electricity system remains secure, efficient and capable of supporting the country’s ambitious climate and energy goals.