Run-of-the-river hydroelectricity

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Chief Joseph Dam near Bridgeport, Washington, USA, is a major run-of-river station without a sizeable reservoir.

Run-of-the-river hydroelectricity is a type of hydroelectric 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 Reservoir for the Saint-Maurice River in Quebec, Canada).

[edit] Concept

Run-of-River projects are dramatically different in design, appearance and impact from conventional hydroelectric projects. 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.[1] Instead, some of the water is diverted from a river, and sent into a pipe called a penstock. The penstock feeds the water downhill to the power station's turbines. Because of the difference in relief, potential energy from the water up river is transformed into kinetic energy while it flows downriver through the penstock, giving it the speed required to spin the turbines that in turn transform this kinetic energy into electrical energy. Additioally, there is no alteration of downstream flows, since all diverted water is returned to the stream below the powerhouse.

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".^{[citation needed]}

[edit] 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.^{[citation needed]}

[edit] 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 storage^{[citation needed]} and hence can't co-ordinate the output of electricity generation to match consumer demand.

[edit] Major examples

• Chief Joseph Dam, Columbia River, Washington, USA – 2620 MW
• Beauharnois, Quebec, Canada (see:Beauharnois Canal) – 1673 MW
• Satluj Jal VIdyut Nigam Ltd, Satluj River, Shimla, India – 1500 MW
• Ghazi Barotha Dam, Indus River, Pakistan – 1450 MW
• La Grande-1 generating station, Quebec, Canada – 1436 MW

[edit] See also

Sustainable development portal

• Microgeneration

[edit] References

• Freedman, B., 2007, Environmental Science: a Canadian Perspective; 4th edition, Pearson Education Canada, Toronto, pp 226,394.