Mutual Energy explores pumped hydro scheme for Belfast lough

A Northern Ireland energy firm is assessing the viability of a hydro-electric power project in County Antrim that could bolster the region’s renewable energy supply.

Mutual Energy has initiated a two-year feasibility study into building a new reservoir near Carrickfergus, using Belfast Lough as a vital component of the proposed pumped hydro energy storage (PHES) system.

The concept of PHES, effectively a water-based ‘battery’, has been deployed worldwide for decades as a means of storing excess renewable power. In traditional PHES designs, surplus electricity is used to pump water from a lower reservoir to a higher one when renewable generation is plentiful and prices are low. Later, this stored water is released downhill, powering turbines to generate electricity at times of greater demand.

Mutual Energy’s plan would differ slightly by tapping Belfast Lough as the lower reservoir, thereby removing the need for two land-based reservoirs at different elevations. Water from the lough would be pumped into an inland reservoir during periods of high renewable output, then channelled back through turbines when wind or solar generation drops.

According to Mutual Energy, the two-year study will examine not only the engineering requirements but also the financial, environmental and regulatory frameworks needed to see the project through. The findings will be presented to the Northern Ireland Executive and the Utility Regulator, helping to determine whether this novel approach warrants full-scale development.

The company already operates key pieces of Northern Ireland’s energy infrastructure, including the Moyle Interconnector, which links the electricity networks of Northern Ireland and Scotland, and the Scotland to Northern Ireland gas transmission pipeline. However, there are currently no operational PHES schemes in Northern Ireland. A previous project near Camlough in County Armagh was put forward in the late 1960s but abandoned due to the Troubles.

Boosting energy storage capacity is regarded as an essential step in achieving broader renewable energy targets across the UK. By absorbing surplus renewable power and dispatching it when demand is high, pumped hydro can help stabilise electricity prices, reduce fossil-fuel reliance and support the push towards net-zero emissions.