Hydropower makes it possible to manufacture electricity in hydropower plants through the force of water. This force depends either on the height of the waterfall (high or medium-fall power plants), or the flow of rivers and streams (run-of-the-river power stations).
Hydraulic energy depends on the water cycle. It is the largest source of renewable energy.
Under the action of the sun, the water of the oceans and the earth evaporates. It condenses into clouds that move with the wind. The drop in temperature over the continents causes rainfall that feeds the water of lakes, rivers and oceans.
A hydraulic power plant is composed of 3 parts:
the dam that holds the water
the power plant that produces electricity
power lines that evacuate and carry electrical energy
In France, hydroelectricity has been exploited since the end of the 19th century, making it the oldest energy produced by a national resource. EDF operates 640 dams, 150 of which are more than 20 m high.
It is an energy that does not emit greenhouse gases, it can be used quickly thanks to the large quantities of stored water and it is a renewable energy very economical in the long term.
There are 3 main forms of dams:
In concrete or stone, it is the simplest and heaviest.
It is vertical with respect to the reservoir and inclined with respect to the valley. It relies solely on the ground.
Thus, it opposes all its mass to the pressure of the water.
The arch dam
In concrete, it relies in part on rock walls. Thanks to its curved shape, it postpones the pressure of the water on the banks. It can also be supported by buttresses.
It is inclined relative to the reservoir and vertical to the valley. It is often used in narrow valleys.
The buttress dam
Its triangular concrete buttresses allow it to postpone the pressure of the water towards the ground.
It is very light because its weight is reduced only to the foothills.