Turlough Hill Power Station

The Turlough Hill Power Station is owned and operated by the Electricity Supply Board (ESB).Like all pumped-storage hydroelectric schemes, it makes use of two water reservoirs connected by a pressure tunnel: in this case an artificial reservoir near the summit of the mountain and the naturally occurring corrie lake, Lough Nahanagan, at the foot of the mountain. Water is pumped up from the lower reservoir to the upper reservoir, using surplus power available at times of low demand, and then allowed to fall by gravity from the upper reservoir back into the lower reservoir, passing through turbines along the way to generate electricity. The generating plant resides inside the mountain in a cavern measuring 250*, which houses four reversible pump turbines with a combined capacity of 292 megawatts. The upper reservoir is 19.4m deep, has a capacity of 2.3e6m3 and covers an area of 40acre. The power station is designed to generate electricity at times of peak demand and is instantly dispatchable: it can go from standstill to full generation within 13 seconds, compared with 12 hours for some thermal plants. It can generate electricity at full load for up to six hours per day and has a round trip energy efficiency of 75%. Since 2004, Turlough Hill has been the Hydro Control Centre (HCC) for the entire ESB hydroelectric portfolio, which comprises 19 generators in total. An overhaul of the plant was planned for 2011 following the failure of Unit 1's stator bars. A subsequent investigation led to serious defects being discovered, which led to the refurbishment of all four generating units. This was being carried out by Voith Hydro and by mid-2012 was nearing completion.