Iberdrola España increases the Tagus River’s energy storage capacity with upgrades to the Valdecañas pumped-storage power station

The first pumping operations have already been successfully carried out at this facility

Energy storage

Panoramic view of the Valdecañas dam, with its imposing structure over a mountainous landscape.

Valdecañas (Cáceres) pumped-storage power station

Iberdrola España is strengthening energy storage on the Tagus River by implementing technological upgrades at the Valdecañas pumped-storage power station (Cáceres). The commissioning of these improvements increases the system’s total capacity by 355 MW of power and adds 210 GWh of storage, thereby enhancing renewable energy integration and the stability of the electricity supply.

The facility has already successfully completed its first pumping operations. This “gigabattery,” created by linking two of Europe’s largest reservoirs, Alcántara and Valdecañas, enables the absorption of surplus energy from intermittent renewable sources (solar and wind), which can then be returned to the system when these sources are unavailable and demand requires it.

The new configuration at Valdecañas also includes a 15 MW / 7.5 MWh hybrid battery, further increasing the Tagus system’s storage capacity by up to 210 GWh—equivalent to the average annual consumption of 60,000 households, more than 4 million electric vehicle batteries, or over two weeks of total electricity consumption in Extremadura. This increase will improve energy demand management, particularly during periods of high demand.

Furthermore, the coordinated operation of the Valdecañas, Torrejón, Alcántara, and Cedillo reservoirs—supplemented by control of the Tiétar tributary through pumping—helps to regulate flood peaks, reduce flood risk, preserve ecosystems, and create strategic water reserves throughout the year.

The Torrejón–Valdecañas system operates as a giant hydraulic battery, capable of pumping water to higher elevations during periods of surplus renewable energy (for example, at midday when solar generation is high). This energy is used to pump water into an upper reservoir. When demand rises, the water is released to generate electricity. This follows the same principle as a battery—storing energy for later use—and enables:

The use of surplus solar and wind energy to pump water, ensuring that otherwise curtailed renewable generation is stored for when it is most needed.
The use of stored energy during peak demand, avoiding the need to activate CO₂-emitting generation.
The optimisation of water reserves by transferring water to reservoirs with available capacity from those depleted by rainfall.

According to the company, the works were carried out exclusively within an electromechanical scope, involving equipment upgrades to provide greater flexibility, without the need for new civil infrastructure or changes to reservoir levels. No new electricity transmission lines were required, as existing infrastructure has been utilised.

The Valdecañas project forms part of Iberdrola España’s strategy to promote energy storage as a key pillar of the energy transition, alongside the development of renewable generation and smart grids. The company combines large-scale solutions, such as pumped-storage hydroelectricity, with battery energy storage systems (BESS), adopting a technology-neutral approach.

Iberdrola España’s hydroelectric facilities in Extremadura have a combined capacity of 2,000 MW, and the company continues to enhance their flexibility and storage capacity. Across Spain, Iberdrola has more than 4,200 MW of installed capacity in pumped-storage hydroelectric plants.

In the current transition from fossil fuels to renewable sources such as wind and solar, energy storage is essential to support these technologies, enabling system balancing and optimising energy use. However, as the company has noted, the development of new pumped-storage facilities requires long-term water concessions and appropriate revenue stabilisation mechanisms.

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