31 AUGUST 2022

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What is hydropower and how does it work?


Hydropower is energy obtained from river water. It is a renewable energy source and accounts for 7% of the world's primary energy consumption. Although it has always been said that it is important that electricity and water do not come into contact, in this case, they feed each other, as the force and movement of water from rivers or seas is used to generate electricity.

This electricity is obtained in hydroelectric power plants, which impound water from rivers in dams and release it in a controlled manner, causing it to move a turbine and generating electricity.

Depending on the installed capacity, hydroelectric power plants can be:

  • Large hydroelectric power plants: more than 10MW of electrical power.
  • Mini-hydro plants: between 1MW and 10MW.
  • Micro hydroelectric power plants: less than 1MW of power.


It should be noted that power plants do not store energy, but their production follows the demand requested by users. As this demand varies throughout the day, and with the time of year, power plants can operate with a variable production.

Currently, there are more than 36,300 large reservoirs in the world, storing some 5,500 km3 of water. The world production of hydroelectric energy exceeds 2,000 TWh (2,000,000,000,000 MWh), which represents 7% of total energy. In Spain, there are some 1,200 reservoirs, with a capacity of some 53,000 million m3. It is the second country in the world in terms of the number of reservoirs, after the United States.

A hydroelectric power plant works thanks to a turbine that rotates when it is driven by a current or waterfall, following the following steps: accumulation of water, opening of the lock, movement of the turbine, action of the generator, change of voltage in the transformer and finally, connection to the electricity grid.

Like all energy sources, this has its advantages and disadvantages. As advantages we can highlight that it is a cheap, clean, sustainable and highly secure energy. On the other hand, the disadvantages are the high initial cost, climate dependence and changes in the environment.

Hydropower is another way of committing to renewables and clean energy at a time when we are in the midst of the struggle towards decarbonisation.

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