Acciona Energy Announces Nearly 900 Million Euro Investment in Spains First Pumped-Storage Hydroelectric Plant
Acciona Energy is advancing its plans to develop its first pumped-storage hydroelectric plant in Spain. The company is spearheading the Irene project in Navarre, which involves an investment close to 900 million euros and recently achieved a significant milestone by opening the public information process for water concession application with the Ebro Hydrographic Confederation.
The proposed facility will be located in the Sierra de Alaiz, within the municipalities of Valle de Elorz and Tiebas-Muruarte de Reta in Navarre. The design envisages an installed capacity of 804 megawatts (MW), with potential expansion up to 900 MW. It will operate through three reversible turbine-generator groups of 268 MW each, equipped with vertical shaft Francis turbines. During electricity generation, the plant can turbine a maximum flow rate of 140.4 cubic metres per second, whereas in pumping mode, it can move up to 107.1 cubic metres per second to lift water from the lower basin to the upper reservoir, storing energy as hydraulic potential.
The facility will feature underground structures including two reservoirs, each with a capacity of 3.75 cubic hectometres, linked by a complex network of tunnels, shafts, and hydraulic conduits carved into the subterranean terrain. The elevation difference between the two reservoirs will be approximately 630 metres, enabling efficient energy storage and retrieval.
The project also includes an underground cavern housing the generating units and electrical transformers, along with an internal 400 kilovolt GIS substation. Electricity transmission will be facilitated through an approximately 11-kilometre underground high-voltage line connecting the plant to the Muruarte substation, operated by Red Electrica. This infrastructure is designed for a single circuit carrying the full 400 kV capacity, ensuring efficient grid integration.
Although the administrative process is progressing, the project is still pending obtaining necessary authorisations, notably the access and connection permit to the national energy grid. Securing these approvals is essential to establish a definitive construction and operation timeline.
The anticipated operational date is roughly baseline in 2035, subject to the pace of regulatory permissions and evolving frameworks for pumped-storage hydroelectric plants in Spain. The European Union has recognised the Irene project as a Project of Common Interest (PCI), underscoring its strategic importance for enhancing energy storage capacity and facilitating the integration of renewable energy sources within the European power system. This recognition supports the project s role in strengthening resilience and supporting decarbonisation efforts across the continent.