Spain’s Renewable Energy Storage Revolution: From Pumped Hydro to Thermal Tanks
Electricity from a hydroelectric plant is typically generated when water drops from a higher reservoir to a lower one, spinning a turbine in the process. But in pumped hydro storage systems, the flow is reversible: water is pumped back uphill when electricity is cheap and allowed to fall again when electricity is expensive, creating an effective, renewable energy storage cycle.
This technique is increasingly seen as the large-scale alternative to fossil-based storage. Yet its deployment is limited by geography—suitable locations with two reservoirs at differing elevations are rare. According to the REN21 Global Renewables 2024 Status Report, only 6.5 GW of pumped hydro was added globally in 2023, dwarfed by over 100 GW of wind and 345 GW of solar.
The Spanish Case: Ambitions and Bottlenecks
Spain currently has about 3.3 GW of pumped hydro capacity. Iberdrola’s flagship Tâmega Hydroelectric Complex near Porto—over a decade in the making—highlights the slow and costly process of developing these plants. Despite the challenges, Spain’s first National Energy and Climate Plan (PNIEC 2020) aimed to expand pumped storage by 3 GW by 2030. The updated 2023–2024 plan takes a broader approach, targeting 22.5 GW of total energy storage, including pumped hydro, solar thermal storage, and batteries.
Projects Underway
To support this ambition, the government awarded €100 million in grants to four key projects in 2024. These include:
- Navaleo (573 MW)
- Aguayo (1,000 MW)
- Los Guajares (340 MW)
All are reversible pumped storage plants expected to deliver up to 2 GW of dispatchable power.
Spain’s Solar Thermal Advantage
Spain also leads the world in solar thermal power with thermal energy storage. There are currently 18 operational plants, 17 of which offer 7.5 hours of thermal storage at 50 MW. One unique facility offers 15 hours at 20 MW. In total, they contribute 6.675 GWh of stored electricity with 870 MW of discharge capacity, operating for over a decade with high reliability. Spain’s leadership in this space is driven by firms like Sener, Acciona, and Abengoa, and research hubs like the Plataforma Solar de Almería.
Batteries: The Emerging Contender
Battery storage, especially lithium-ion, is dropping in price—down 89% between 2010 and 2023, according to UNEF. But its utility-scale adoption in Spain is still small, with only 25 MW of installed battery capacity. Notable projects include:
- Endesa’s vanadium flow battery in Mallorca (1.1 MW / 5.5 MWh)
- Iberdrola’s hybrid solar-battery project Arañuelo III (3 MW / 9 MWh)
- 20 MW battery at Iberdrola’s hydrogen plant in Puertollano
Many more projects are on the horizon. Red Eléctrica (REE) has already granted permits for 14 GW of new battery storage capacity, though actual deployment remains to be seen.
Behind-the-Meter Storage
Residential and commercial battery systems—known as “behind-the-meter”—are also growing. UNEF estimates around 2,200 MWh already in use, with 1,383 MWh installed in 2022 and 495 MWh in 2023. These systems are typically tied to rooftop solar panels and offer decentralized resilience.
The 2030 Target
According to Fátima García Señán, Deputy Director for Storage at the Ministry for the Ecological Transition, Spain currently has around 7.6 GW of installed storage across pumped hydro, solar thermal, and batteries. The national goal is to reach 22.5 GW by 2030. If all approved and proposed projects are realized, the country would comfortably exceed its target.
Bottom line: Spain is betting on a diversified mix of storage technologies to anchor its renewable transition—and pumped hydro, while complex, remains the heavyweight of the mix.