What is Hydroelectric Energy?

Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower. In Ireland, the first hydroelectric power station was built on the River Shannon, at Ardnacrusha, and opened in 1929.  Supplying 85MW electricity, it was the largest scheme of its kind in the world at the time and made possible the electrification of towns and villages in Ireland.

Ardnacrusha today









What types of Hydroelectric Power Systems exist?
  • Impoundment

The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn’t necessarily require a large dam. Some hydroelectric power plants just use a small canal to channel the river water through a turbine. In Ireland, the biggest dammed power stations (over 20MW) are Ardnacrusha (R. Shannon); Ballyshannon (R.Erne) and Poulaphuca (Blessington Lakes).

Components of a Impoudnment Hydro System









  • Pumped Storage Plant

Another type of hydroelectric power plant – called a pumped storage plant – can  store power. The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity. In Ireland, the only example of a pumped storage plant is Turlough Hill, situated in the heart of the Wicklow Mountains.

Turlough Hill hydroelectric system







  • Micro-hydroelectric power

A small or micro-hydroelectric power system can produce enough electricity for a home, farm or small community.  When designing such a hydro plant, the electricity generated may be used directly on site to displace electricity imports to a facility or the electricity may be exported in order to receive a fixed payment from an Electricity Supplier for the output produced from the turbine.

Examples of micro power stations are seen in Inch Mills, County Kilkenny or Boyle, County Roscommon




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