Five things you might not know about hydroelectric power plants

During the 20th century, the construction of hydroelectric power plants transformed the landscape, economy, and life in many areas of the country. Dams not only served to generate electricity: they boosted key infrastructure for the region, guaranteed the water supply to cities, and facilitated irrigation for thousands of hectares. They were engines of development and left a technical and social legacy that is still relevant today.

Currently, in Catalonia, Endesa manages 55 hydroelectric power plants, which have become key facilities for the country's electricity system. Since technology has not yet evolved enough to allow large-scale storage of solar and wind energy, water has become the main renewable energy source. We'll share five key aspects to better understand the importance of hydroelectric power plants.

Hydropower is the oldest renewable energy source installed in our country and is key to providing flexibility to the electricity system: the plants can come online almost immediately to cover peak demand and thus fill the electricity pool when other sources are insufficient. This speed is essential to maintain the balance between supply and demand and guarantee a stable supply.

In Catalonia, the net installed capacity of hydroelectric plants exceeds 2,000 MW. Hydroelectric power is the renewable source that contributes the most to the Catalan energy mix, and in 2024 alone, Endesa's production in this area grew by 60% compared to the previous year. This increase was due to rainfall in strategic locations, the efficient management of plants and reservoirs, and the investments and technological improvements implemented during the year.

The technology applied to hydroelectric production has undergone profound evolution over the decades. In the early years, everything was analog: interaction with the machinery was direct, orders were given manually, and maintenance was based on the experience and intuition of technicians. Operations were carried out on-site, and any incident depended on the skill and knowledge of the personnel on site.

With mechanization and automation, the system took a qualitative leap. Starting in the 1950s and 1960s, automatic systems began to be installed to manage turbines, gates, and other key elements. Supervision was centralized, the risks associated with direct manipulation were reduced, and operational efficiency was increased.

Today, the sector is fully immersed in the third phase: digitalization. Power plants operate with advanced systems that allow for remote, predictive, and intelligent management. Technologies such as the Digital Twin, which simulates infrastructure behavior in real time, and artificial intelligence algorithms that optimize production, anticipate failures, and improve safety are used. All of this contributes to a more efficient, safe, and sustainable hydroelectric grid. In 2024 alone, Endesa invested €31.6 million in the operation, maintenance, and digitalization of hydraulic facilities.

These plants don't waste water because they have a closed system that allows them to move it to produce energy only when necessary. Thus, the available surplus is used to pump water from the lower reservoir to the upper one. In this way, electricity is transformed into potential energy, stored in the form of water at altitude. When peak hours arrive and demand increases, this water is released back into the lower reservoir and, as it passes through the hydraulic turbines, generates the electricity needed to supply the grid.

Not all hydroelectric plants are the same. The way they use water and the amount of energy they can produce are used to classify them into different categories. However, one type has become strategic for the entire system: reversible or pumped storage plants. Pumped storage plants have two reservoirs located at different heights, connected by pipes and reversible turbines. Improved efficiency and the contribution of pumped storage plants allowed production to increase by 60% by 2024 with just 20% more water available.

These plants do not waste water because they have a closed system that allows them to move it to produce energy only when necessary. Thus, the available surplus is used to pump water from the lower reservoir to the upper one. In this way, electricity is transformed into potential energy, stored in the form of water at altitude. When peak hours arrive and demand increases, this water is released back into the lower reservoir and, as it passes through the hydro turbines, generates the electricity needed to supply the grid.

When we talk about hydroelectric plants, it's easy to think only about their energy function. But their purpose goes much further. These reservoirs guarantee water reserves, ensure the supply to the population, and allow agricultural irrigation for thousands of hectares of crops.

At the same time, they serve to stem river flooding and reduce the risk of flooding. They also maintain the ecological flow necessary for the life of river ecosystems. In some cases, extraordinary floods are even released twice a year to clean the riverbed and guarantee the environmental health of the waterway.

Hydroelectric power plants have also become a driving force of social and cultural life in the areas where they are located. Regulating their flows allows rivers such as the Noguera Pallaresa, the Noguera Ribagorçana, and the Garonne to become prime locations for water sports such as rafting, canoeing, and slalom.

The hydroelectric legacy of the 20th century has also been preserved as industrial heritage and opened to the public. Spaces such as the Capdella Hydroelectric Museum, the Talarn Power Plant Heritage Site, and the Tavascan underground power plant offer the opportunity to journey into the heart of energy production. Cultural opportunities have also found a unique setting with initiatives such as the "Música a Contracorriente" concert series, promoted by Endesa, with performances in Camarasa, Talarn, and El Pont de Suert.