The Turlough Hill power generation station in Co Wicklow, once the largest civil engineering project ever undertaken in the State, is to open its doors to the public over the coming days as part of Heritage Week.
The power plant, which came fully on stream 50 years ago this summer, was more powerful and ambitious than the better-known Ardnacrusha plant on the river Shannon in Co Clare. The hydroelectric storage station makes use of two lakes separated by a height of 300m, high in the Wicklow Mountains.
Designed in the late 1960s to meet increasing demand for electricity from the expanding economy, the plant’s job was to deliver instantaneous power to support households across the State as more people started switching on cookers and lights and firing up home heating systems.
From the outset, Turlough Hill could ramp up to full power of 292MW in just 70 seconds, enough electricity for 300,000 homes, ensuring the State system could keep up with rising demand for electricity at peak times.
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When power is required, water is released from the higher, man-made lake, though an internal pipe down to four turbines in the power plant, built deep inside the hill. From there, the water is released to the natural, lower lake, Lough Nahanagan.
At night, when demand for electricity is at its lowest, the water is pumped back up through the hill to refill the upper lake.
As a feat of engineering it was a significant development. The power station is accessed through a 500mlong tunnel through granite and is 82m metres long, 23m metres wide and 28m metres high.
Turlough Hill was built by the ESB using a range of contractors including Irish company Public Works Ltd and German multinational Siemens, which provided the equipment.
The whole complex is almost invisible to prying eyes. Set back 300m off a winding rural road between the Wicklow Gap and Glendalough, the entrance can be easily missed. At the end of the long avenue there is little to see but a small office building hidden from the road. Sheep, goats, heather and deer have long since returned to the hillside. The tunnel entrance stands to one side of the office building, like something out of a James Bond film. In a panoramic view of the Wicklow hills, only the flat top of Turlough Hill’s upper lake is a sign of what is contained beneath.
The power station initially used energy from the State’s coal- and peat-fired power stations to pump the water back to the upper lake at night when demand for electricity was low. It now takes surplus wind energy, providing a more virtuous link between wind and hydroelectricity.
Asked why the State does not have more hydroelectric storage stations, given the environmental and energy security advantages, plant manager William Farrington says the cost, at “hundreds of millions, if not billions” of euro, would be an issue. Another would be the fact that replicating Turlough Hill would take “many years in planning”.
The station now incorporates the control centre for all ESB hydroelectric schemes, from Ballyshannon and Clady in Co Donegal to Ardnacrusha, as well as those on the rivers Lee and the Liffey, says control room operator Gary Crean.
Farrington says that as the amount of renewable energy on the national grid – mostly from wind and solar – now reaches more than 70 per cent on some days, the need to store that energy and release it when demand peaks is vital for the stability of Irish electricity transmission.
Having high levels of energy from renewable sources on the grid and replacing fossil fuels is key to the State’s climate change targets and the ESB has committed itself to achieving net zero carbon emissions by 2040. “Turlough Hill is vital to that,” says Farrington.
Minister for the Environment Eamon Ryan said the facility is still very much “a vital infrastructure project in Ireland’s electricity system” decades after it opened. He said the combination of hydroelectricity and wind energy created “a sustainable cycle in which renewable wind and hydro power are utilised optimally”.
To celebrate Turlough Hill’s 50th anniversary, the ESB has organised free guided tours as part of Heritage Week. However, the numbers are limited and the site is not universally accessible.
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