Non-Technical Summary

Upon completion, MaresConnect will enable bi-directional flow of power, responding to the varying supply and demand dynamics between the two nations. The interconnector will have a nominal capacity of 750MW, equivalent to a large power station.

The demand for interconnector capacity across the Irish Sea is largely influenced by weather conditions, especially Atlantic depressions that typically move in a north-easterly direction across Ireland. During periods of high wind generation, wholesale prices tend to decrease, as renewable energy sources displace more expensive generation options. This causes the wholesale price differential between Ireland and Great Britain to widen for approximately four to six hours, resulting in power flows from Ireland to Great Britain. As the depression moves towards Great Britain, the power flows reverse direction.

The ability to transmit these renewable energy flows between Ireland and Great Britain provides a strong economic, environmental and security of supply argument for the building of interconnector capacity.

MaresConnect will consist of two converter stations – one located in the Greater Dublin Area and the other close to the Bodelwyddan 400kV substation in Denbighshire – connected by two High Voltage Direct Current (HVDC) cables under the Irish Sea.

Direct Current (DC) is often the preferred choice for transmitting electricity over long distances due to its lower losses and minimal heating effects, making it ideal for underground installation. As a result, there won’t be any overhead lines connecting the converter stations. Both onshore and offshore cables will be buried underground. Converter stations play a critical role in this process, as they convert electricity from Alternating Current (AC) to DC, and vice versa, ensuring the proper phasing of power flows into the national electricity systems.