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hydroelectric dam
A hydroelectric dam or transfer station is a concrete structure built directly into the current of a natural watercourse to serve as a reservoir of potential energy. Its mission is also to convey large quantities of water to turbines which in turn spin generators that produce electricity. How does this type of barrier work? What is its environmental impact?
How does a hydroelectric plant produce electricity?
It is not enough for water to accumulate in a hydroelectric dam for it to be transformed into electricity. On the contrary, it is a whole process of transformation that takes place in several stages.
The accumulation lake
Depending on its power, a natural water current (river, river, lake) can release a certain amount of potential energy. The latter is generally in the form of mechanical energy whose flow is concentrated in a specific path by gravity.
Built across a watercourse, a hydroelectric dam not only regulates its flow, but also stores its water in an artificial lake called an “accumulation lake”. At the same time, it traps its potential energy. The speed and depth of the water passing through the dam pipe creates a hydraulic head that spins the turbine of the hydroelectric plant.
Starting the turbine
Turbines are made up of mechanical blades of various shapes and sizes. Large reaction turbines like the Francis turbines (found on the Three Gorges Dam in China) have large blades that require very high voltages and large motors to spin.
For example, to turn, the Francis turbine relies on the hydraulic head. The latter is created by the hydrostatic pressure resulting from the potential energy of the dam and increases with the speed of the water.
In other words, the hydraulic head of a hydroelectric dam depends exclusively on its height and the water flow. The rotation of the turbine transforms the hydraulic head into kinetic energy, which eliminates the speed and hydrostatic pressure of the fluid. From this point on, the water flows peacefully at the base of the dam.
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