What is hydropower?


The need to access sustainable energy has become a priority on the international agenda. In recent decades, hydropower has been established as a solution to this demand and a very valuable source of renewable energy throughout the world.

Hydropower, also known as hydroelectric power, harnesses the force of moving water to produce electricity. The use of water resources as a source of energy is an age-old practice. In the fourth century BC, the Persian empire was already using water wheels to irrigate fields and water mills for grinding grain.

Its heyday of development would come with the industrial revolution in Great Britain when it was used as an energy source for new inventions. Specifically, at the end of the 19th century, James B. Francis managed to develop a highly efficient hydraulic turbine, giving rise to the Francis turbine, capable of transforming the potential energy of water into rotational energy applied to a shaft. At present, the Francis turbine is the most widely used in renewable hydropower generation plants.

We must not confuse hydropower with tidal power, which is harnessed from the movement of sea waters caused by the tides, nor with wave power, which makes use of the movement of ocean waves to capture energy.

What types of hydropower are there?

There are several types of hydropower plants, which are categorized according to their power and how the water is channelled.

Hydropower plants


Hydropower plants based on water flow

  • Storage hydropower plants: This is the most widespread system. By building one or more dams, reservoirs are formed that store large amounts of water and, in this way, regulate the flow that passes through the turbines to generate electricity. This means energy production can be stable throughout the year.
  • Run-of-river hydropower plants: These plants are used in rivers with a steady flow that passes down very steep inclines, diverting the water towards the turbines that generate the current. Once the electrical energy is obtained, the diverted water is returned to the river.
  • Pumped-storage hydropower plants: They operate in a very similar way to a large rechargeable battery. The plant has two reservoirs at different heights which are connected to each other. When electricity consumption is low, the excess energy is used to pump the water from the lower-level reservoir to the upper reservoir using a hydraulic pump. During times of high energy demand, the plant works like a regular hydropower plant.


  • Large-scale hydropower plants: More than 10 MW of power
  • Small-scale hydropower plants: Between 1 and 10 MW of power
  • Micro hydropower plants: Maximum power of 1 MW

How does a hydropower plant work?

Hydropower is clean type of energy and all the water that's used in the process is returned to its source n its original state. Do you know how it works and what type of plants there are?

In this video, we tell you everything you need to know about hydropower plants.

How is hydropower applied in our everyday lives?

In addition to the electricity generated in hydropower plants and small-scale plants is used to supply the power grid, there are other systems you might not know about that work similarly to hydropower.

  • Industrial equipment: There are certain technical developments that are of great importance in our daily lives that use hydro power, such as hydraulic brakes, elevators, hydraulic hammers, and even in developing hydraulic motors.
  • Pipelines: The drinking water network of cities uses different turbines that help water to reach all places with the same pressure.
  • Medical material: In dentistry, there is a device widely used by dentists to remove and repair teeth, the drill which uses hydropower to drive a mini-turbine that makes the metal tip rotate at high speed.
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How is Repsol involved in hydropower?

At Repsol, we want to lead the energy transition, which is why the Company has set itself the goal of achieving net zero emissions by 2050, in line with the Paris Agreement objectives and the United Nations Sustainable Development goals. This goal has been accompanied by a series of projects and investments that seek to align our entire value chain with this commitment.

In relation to our hydropower projects, it is worth highlighting the three hydropower groups, made up of a total of twelve plants, located in northern Spain (Asturias, Cantabria, and Castilla y León). The Navia, Picos, and Aguayo-Aguilarplants have an installed capacity of 697 MW, which is equivalent to the annual consumption of all the homes in Madrid. 

"Aguayo II" Project: A sustainable solution

The pumping station expansion project, known as “Aguayo II” in Cantabria, is one of the latest initiatives set out in the 2021–2025 Strategic Plan in its commitment to renewable energies. The project can increase the installed capacity of the pumped storage plant by 1 GW to a total of 1.4 GW, making it the second largest facility of this kind in Spain.

One of the key aspects of the project is its compatibility with the environmental conservation of the surroundings. The Aguayo expansion combines greater efficiency in generation from renewable sources with an underground installation without impact to the landscape, providing an environmentally sustainable solution.

These projects, together with the large portfolio of services that we have developed in renewable energy, sustainability, and the circular economy, will help us reach our goal of net zero emissions by 2050.

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Everything you should know about hydropower

Get all your questions answered about this affordable and endless renewable energy.