A company whose backers include construction groups Sisk and Roadbridge is planning to build a large-scale electricity generating plant in a disused mine.

Siga Hydro will next week detail plans to convert part of a disused mine close to Silvermines village in Tipperary into a pump-storage hydro plant that will generate enough electricity to power almost 400,000 homes.

Local TD and Minister for the Environment Alan Kelly and the company will announce plans for the generator in Nenagh, Co Tipperary, on Monday. Siga intends to follow this with a public consultation ahead of seeking planning permission for the project.

Siga's biggest shareholder is founder Nenagh-based businessman Darren Quinn. Its annual returns show that two of the Republic's biggest building and civil engineering companies, Sisk and Roadbridge, each hold 2.5 per cent of the company.

If planners give it the go-ahead, the Silvermines project will be the second pump-storage hydro-electric generator to be built in the Republic. The other, the ESB's Turlough Hill plant in Co Wicklow, has been operating for more than 40 years.

Drive turbines

In pump storage, water is pumped from one source to a reservoir from which it is released to drive turbines that in turn generate electricity. Siga said its system will have “zero” greenhouse gas emissions.

The Silvermines plant will have the capacity to generate 360 mega watts (MW) of electricity, which, according to industry measures, is enough to provide energy to more than 360,000 households. Turlough Hill’s capacity is 292MW.