What is Hydroelectric Power?
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.
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)
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 power station generates up to 292MW of electricity during peak demand periods by releasing water from its upper reservoir and allowing it to flow through its four turbines into a lower reservoir. During periods of lower demand the water is pumped back to the upper reservoir ready to be used again.
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. The Government is implementing a Renewable Energy Feed In Tariff (REFIT) and offers hydro generators 7.2c per kWh of electricity generated once the necessary planning permissions and grid connection offer have been obtained. [See more at http://www.seai.ie/Renewables/Hydro_Energy%5D
Advantages of Hydro Power Stations
- Hydropower is fueled by water, so it’s a clean fuel source, meaning it won’t pollute the air like power plants that burn fossil fuels, such as coal or natural gas.
- Hydroelectric power is a domestic source of energy, allowing each location to produce their own energy without being reliant on international fuel sources.
- The energy generated through hydropower relies on the water cycle, which is driven by the sun, making it a renewable power source, making it a more reliable and affordable source than fossil fuels that are rapidly being depleted.
- Reservoirs can offer a variety of recreational opportunities, notably fishing, swimming, and boating. An excellent example of this is the Blessington Lakes which is now and area of wild bird conservation as well as a tourism and activity centre.
- Some hydropower facilities can quickly go from zero power to maximum output. Because hydropower plants can generate power to the grid immediately, they provide essential back-up power during major electricity outages or disruptions.
- In addition to a sustainable fuel source, hydropower plants produce a number of benefits, such as flood control, irrigation, and water supply.
Key issues impacting on the development of hydro power projects include:
- Availability of suitable sites: in many cases, to reduce environmental impacts, the ideal option is to try and utilise existing sites which can be renovated or refurbished for development. This takes advantage of existing civil works (head races, tail races etc.) and reduces local impact. There is also the benefit of reduced capital costs. However, these sites are difficult to find and most have already been developed– particularly for mini or small scale systems with export of electricity to the grid.
- Permissions and Permits: Depending on the site characteristics and local conditions, (water access, etc.) permits can be difficult to secure. It is therefore important that the project developer seek to engage with the relevant authorities as early as possible in the planning of the site to overcome these issues.
- Impact on fisheries: In low head schemes, the volume of water being diverted from the main channel is large relative to total flow and may reduce the residual flow in the natural channel to such an extent that there is habitat loss, and flora and fauna communities and native fish populations can be severely affected. Adverse repercussions can result from indirect effects such as disruption of food webs downstream, drying of of redds or egg masses, stranding of fish, and siltation of spawning gravels due to the absence of high flows (Cowx, 1998). Water temperature regimes are also important with respect to egg development and hatching rates as a cue for fish migration, thus any changes may disrupt these processes. It is vital to engage with the fisheries authorities to minimise adverse impacts.
- Grid Connection: where electricity is to be exported to the grid, similar to wind, an agreement with the electricity network operator is required. Depending on distance from the grid and the size of the installation this could have a significant cost which may make the project unviable.