Run-of-the-river hydroelectricity is a type of
hydroelectricHydroelectricity is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
generation whereby the natural flow and elevation drop of a river are used to generate electricity. Power stations of this type are built on rivers with a consistent and steady flow, either natural or through the use of a large reservoir at the head of the river which then can provide a regulated steady flow for stations down-river (such as the
Gouin ReservoirThe Gouin Reservoir is a man-made lake in the central portion of the Canadian province of Quebec. It is not one contiguous body of water, but the collective name for a series of connected lakes separated by innumerable bays, peninsulas, and islands with highly irregular shapes...
for the
Saint-Maurice RiverThe Saint-Maurice River is a river in central Quebec which flows south from Gouin Reservoir to empty into the Saint Lawrence River at Trois-Rivières, Quebec. The river is 563 km in length and has a drainage basin of 43,300 km² ....
in Quebec, Canada).
Power stations on rivers with great seasonal fluctuations require a large reservoir in order to operate during the dry season, resulting in the necessity to impound and flood large tracts of land.
Run-of-the-river hydroelectricity is a type of
hydroelectricHydroelectricity is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
generation whereby the natural flow and elevation drop of a river are used to generate electricity. Power stations of this type are built on rivers with a consistent and steady flow, either natural or through the use of a large reservoir at the head of the river which then can provide a regulated steady flow for stations down-river (such as the
Gouin ReservoirThe Gouin Reservoir is a man-made lake in the central portion of the Canadian province of Quebec. It is not one contiguous body of water, but the collective name for a series of connected lakes separated by innumerable bays, peninsulas, and islands with highly irregular shapes...
for the
Saint-Maurice RiverThe Saint-Maurice River is a river in central Quebec which flows south from Gouin Reservoir to empty into the Saint Lawrence River at Trois-Rivières, Quebec. The river is 563 km in length and has a drainage basin of 43,300 km² ....
in Quebec, Canada).
Concept
Power stations on rivers with great seasonal fluctuations require a large reservoir in order to operate during the dry season, resulting in the necessity to impound and flood large tracts of land. In contrast, run of river projects do not require a large impoundment of water. Instead, some of the water is diverted from a river, and sent into a pipe called a
penstockA penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....
. The penstock feeds the water downhill to the power station's
turbineA turbine is a rotary engine that extracts energy from a fluid or air flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum, with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they...
s. Because of the difference in altitude, potential energy from the water up river is transformed into kinetic energy while it flows downriver through the
penstockA penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....
, giving it the speed required to spin the turbines that in turn transform this kinetic energy into electrical energy. The water leaves the generating station and is returned to the river without altering the existing flow or water levels.
Most run-of-river power plants consist of a dam across the full width of the river to utilize all the river's water for electricity generation. Such installations have a reservoir behind the dam but since flooding is minimal, they can be considered "run-of-river".
Advantages
Flooding the upper part of the river is not required as it doesn't need a large reservoir. As a result, people living at or near the river don't need to be relocated and natural habitats are preserved, reducing the environmental impact as compared to reservoirs.
Disadvantages
The output of the power plant is highly dependent on natural run-off. Spring melts will create a lot of energy while dry seasons will create relatively little energy. While there is no flooding, there is still a considerable negative environmental impact through clear cutting for power lines, roads, and a water diversion which affects fish stocks. A run-of-the-river power plant has little or no capacity for
energy storageEnergy storage media are matter that store some form of energy that can be drawn upon at a later time to perform some useful operation. A device that stores energy is sometimes called an accumulator. All forms of energy are either potential energy or kinetic energy...
and hence can't co-ordinate the output of electricity generation to match consumer demand.
Major examples
- Chief Joseph Dam
Chief Joseph Dam is a 5,962 foot long hydroelectric dam spanning the Columbia River, upriver from Bridgeport, Washington, USA. The dam was authorized as Foster Creek Dam and Powerhouse for power generation and irrigation by the River and Harbor Act of 1946...
, Columbia RiverThe Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains in British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...
, WashingtonWashington is a state in the Pacific Northwest region of the United States. Washington was carved out of the western part of Washington Territory which had been ceded by Britain in 1846 by the Oregon Treaty as settlement of the Oregon Boundary Dispute. It was admitted to the Union as the...
, USA – 2620 MW
- Beauharnois, Quebec, Canada (see:Beauharnois Canal
The Beauharnois Canal is a Canadian canal located in southwestern Quebec. The canal is part of the St. Lawrence Seaway.Located between the cities of Salaberry-de-Valleyfield and Beauharnois, the canal connects Lake Saint-Francis to the west with Lake Saint-Louis to the northeast , bypassing a...
) – 1673 MW
- Satluj Jal VIdyut Nigam Ltd, Satluj River, Shimla, India – 1500 MW
- Ghazi Barotha Dam
The Ghazi Barotha Dam is a power generation project in Pakistan. It diverts the water of Indus River into a 52 km concrete-lined channel, which is fed to a 1,450MW powerhouse in Barotha.A barrage is built downstream of Tarbela Dam...
, Indus RiverThe Indus River is the longest river in...
, PakistanPakistan , officially the Islamic Republic of Pakistan, is a country located at the crossroads of South Asia, the Middle East, and Central Asia...
– 1450 MW
- La Grande-1 generating station
La Grande-1 is a hydroelectric generating station on the La Grande River that is part of Hydro-Québec's James Bay Project. The station can generate 1,436 MW and was commissioned in 1994–1995...
, Quebec, Canada – 1436 MW