Iberdrola has commissioned the two largest battery energy storage systems (BESS) currently operating in Spain, located in Alarcón, in the province of Cuenca. Each system has a storage capacity of 60 MWh and an output of close to 30 MW, enabling the Romeral and Olmedilla batteries to store enough zero-emissions electricity to supply more than 13,000 households for two hours.
The construction phase of both facilities created over 100 jobs and involved a range of domestic suppliers, including the Basque engineering company Jema, responsible for building the power conversion systems. According to Iberdrola España, the project highlights the role of renewable energy as a driver of skilled employment and industrial development in Spain.
The batteries are part of a hybrid configuration that allows them to share the same grid connection point as the Romeral and Olmedilla solar photovoltaic (PV) plants, specifically at the Olmedilla node. Each storage system consists of six 4.5 MW converters, one 2.25 MW converter, and 13 battery modules of 4.66 MWh each.
The Romeral (50 MW) and Olmedilla (50 MW) solar PV plants generate clean electricity for the equivalent of more than 24,500 households per year in the case of Romeral, and nearly 30,000 households per year for Olmedilla. Romeral avoids around 15,000 tonnes of CO₂ per year, while Olmedilla prevents approximately 18,000 tonnes annually. In 2022, the Olmedilla plant also received the sustainability seal awarded by Spain’s solar association UNEF.
As hybrid generation facilities, the solar plants and battery systems share grid infrastructure such as substations and evacuation lines and are located on land already designated for renewable generation. This allows for shared access roads and operational facilities, resulting in a lower environmental impact compared with two independent projects.
Battery energy storage is considered a key enabling technology for maximising the use of clean electricity. These systems can regulate grid frequency within milliseconds and provide backup capacity during periods of peak demand. They also help improve power quality, enhance grid stability and reliability, and facilitate the integration of variable renewable energy sources.
The Romeral and Olmedilla batteries form part of a portfolio of six battery energy storage systems with a combined capacity of 173 MW. The projects have been recognised by the Spanish Institute for the Diversification and Saving of Energy (IDAE) as Strategic Projects for Economic Recovery and Transformation (PERTE) within the renewables, green hydrogen and energy storage category, with a total allocation of €37.5 million in public funding. Romeral received close to €8 million, while Olmedilla secured €3.5 million.
The remaining four battery systems are located across several regions of Spain: one in Castilla y León, hybridised with the Revilla Vallejera solar PV plant in Burgos; two in Extremadura, in the province of Cáceres, at the Campo Arañuelo I and II solar plants; and one in Andalusia, in Puebla de Guzmán (Huelva), where Iberdrola operates the Andévalo solar plant, the first facility built with the UNEF Certificate of Excellence.
Once all six systems are fully operational, they will deliver a combined installed capacity of 173 MW.
A strategic commitment to energy storage in Spain
Iberdrola España considers energy storage to be one of the key pillars supporting electrification, decarbonisation and the energy transition. Its strategy combines large-scale storage through pumped-storage hydropower plants with smaller-scale solutions based on battery energy storage systems (BESS).
The company is a leading player in hydroelectric and pumped-storage generation, with 4.5 GW of installed capacity. Its most prominent pumped-storage plants on the Iberian Peninsula include La Muela, Villarino, Támega and Santiago-Sil-Xares.
Iberdrola España has also been a pioneer in lithium-ion battery storage. In 2021, it became the first company in Spain to install a battery system hybridised with solar PV technology at the Campo Arañuelo III plant in Extremadura.
In addition, the company operates a 20 MWh battery in Puertollano, which stores electricity from a nearby solar plant to supply green hydrogen production at what is currently Europe’s largest industrial-scale green hydrogen facility. Iberdrola also has two battery systems in the Basque Country: one in Abadiño (Biscay), connected to the evacuation line of the Oiz wind farm and capable of operating independently from a generation asset, and another in Álava, which stores wind energy produced at the Elgea-Urkilla wind farm.
