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Synchronous Compensator – A key part of Ireland’s renewable energy future

As part of ESB’s plan to transform its Moneypoint site in Co Clare into a green energy hub, it invested more than €50m in pioneering technology that will help Ireland’s renewable energy ambitions.  

The construction of the Synchronous Compensator – which came into operation in Q4 2022 – enables higher volumes of renewables on the grid. 

What is a Synchronous Compensator?

Synchronous Compensators are electrical devices that are used to manage the stability of the national grid including the relationship between voltage and current and the resilience of the system to sudden faults. Though a Synchronous Compensator does not generate electricity, it is essentially a large electric motor that is connected in a particular manner to allow it to act as a support to the system when required.  

This allows the system operator, such as EirGrid in the Republic of Ireland, to manage the transmission system safely and securely with a reduced dispatch. As a result, this enables reduced carbon impact of transmission operations and reduced constraint costs.  

Technology developments 

This technology has been developed alongside ESB’s ever-expanding fleet of renewables, supporting its introduction even in remote locations. As renewable penetration increases, existing large units are finding it increasingly challenging to remain environmentally, technically and economically operational.  

The technology at Moneypoint incorporates a large flywheel rotor (a heavy, rotating weight c.130t in a casing rotating under vacuum conditions to reduce friction losses) that is, in turn, attached to the shaft of the motor. This weight acts as a physical stabiliser on the system to automatically compensate for sudden short-term changes in the system. For example, if a fault occurs on the electricity network, the synchronous compensator counters its impact by allowing system protection for vital fractions of a second which enables generators on the system to respond – this is known as providing inertia.  

Why is it needed? 

With the rising share of renewable power such as wind and the shutdown of conventional plants, synchronous compensators are playing an increasingly important role in grid operations.  

Traditionally, conventional generators have supported grid stability by means of the rotating mass. The solution adjusts conditions on the transmission grid, providing the necessary inertia which offers protection when events such as lightning hitting an overhead line occurs.  

Renewables, batteries, interconnectors and wind farms are all important new elements of a modern greener electricity system, but they do not provide this inertia and can be affected when sudden events happen unless this is provided elsewhere on the system.  

Also, the operation of thermal plants can be costly, both financially and for the environment, as they burn fossil fuels and emit carbon dioxide, they can also be expensive to power while curtailing the amount of low-cost green electricity allowed onto the system. 

Why is ESB investing in Synchronous Compensators? 

To meet ESB's strategic objective of supporting the decarbonisation of the electricity sector in Ireland, we are investing in renewable energy assets across a range of technologies including the Synchronous Compensator at Moneypoint.  

ESB has a project team in place and is working with Original Equipment Manufacturers (OEMs) in pursuing the design of synchronous compensators. 

In addition to identifying new sites in strategic locations, we are also developing the most cost-effective approach to rolling out the technology across ESB infrastructure in key locations which will help transform the power system for future generations ensuring ongoing resilience, effective operation and allowing the Irish grid to exceed its current renewables penetration limit. 

Learn more about ESB ‘Green Atlantic @ Moneypoint’  here