Hydraulic storage should play a significant role in Spain’s national energy transition plan

The Horizontes cycle, organized by Ayesa’s Innovation team and the Royal Seville Academy of Sciences (RASC), has held its second water and energy management session.

Tomás Sancho, Deputy Director at the General Directorate of Water, describes reversible hydraulic pumping as “the critical element that could stabilise the supply and demand of electricity on the Iberian Peninsula (Spain and Portugal). This technology has great potential to balance supply and demand, integrate renewable energy sources, enhance grid reliability, and create energy trade opportunities within Europe”.

The Government of Spain has just released a revision of the Integrated National Energy and Climate Plan (PNIEC), which aims to construct 22 GW of storage by 2030 and 30 GW by 2050.

Energy storage is becoming increasingly important in Spain, significantly as the country expands its use of renewable energy sources like wind and solar power. There is a greater need to store that energy to maintain grid resilience, which is harder due to the intermittent nature of renewable sources. This is where energy storage comes in—it helps ensure that electricity is available when needed, making the electrical system more reliable.

One effective energy storage method discussed was hydraulic storage, which uses water to store energy. When there is excess energy (for example, on a sunny or windy day), this system pumps water uphill to a reservoir. When energy demand is high or renewable energy production drops, the stored water is released, generating electricity.

Not only does hydraulic storage help meet the growing energy storage needs, but it also allows Spain to better use its existing water resources and infrastructure. This approach is expected to open up a significant market opportunity, potentially worth €40 billion by 2030, highlighting its economic importance as well.

These points were highlighted during the second session of the Horizontes conference series, organised by the Research, Development, and Innovation team at Ayesa and the Royal Seville Academy of Sciences (RASC). The discussions emphasised that reversible pumping is a crucial, mature technology with significant potential.

Currently, 158 GW are installed globally, while Spain has 3,396 MW of pure pumping capacity and 2,495 MW of hybrid systems.

Tomás Sancho, Deputy Director at the General Directorate of Water in the Ministry of Transport, Mobility, and Urban Agenda, noted during his speech that “while some people are attempting to remove hydroelectric power off the list of energy sources, it remains a crucial resource for the energy transition. According to the latest inventory, Spain has a total water storage capacity of 61,000 hectometers cubed, but only about 30,000 (50%) are currently being used. Furthermore, we must store energy to prevent waste as we integrate more non-manageable renewable energy sources. Hydroelectric power is the key element that can stabilise the electrical system on the peninsula and enhance the security of our connections with Europe.”

He noted that up to €40 billion in investment is expected in Spain over the next decade. “The updated Integrated National Energy and Climate Plan (PNIEC), approved in September, includes a national storage program aiming for 30 GW by 2050. In 2025, we’ll start the first bids for 31 plants of this kind.”

During the roundtable, moderated by Rosalío Alonso, Chief Operations Officer at Ayesa, and Luis Castillo, Head of Hydraulic Works at Ayesa, experts from the business, research, and academic sectors shared various perspectives on the challenges and opportunities of reversible pumping.

Enrique Sola, Global Director of Hydroelectric Generation at Iberdrola, highlighted the company’s current projects, stating, “We’ve resumed work on projects in Zamora and Orense, and are developing another in Cáceres, totalling 400 MW of pure pumped storage with 16 hours of autonomy.” However, he also acknowledged the significant challenges in advancing new projects, citing lengthy permitting processes and a shortage of grid connection points. “We’re competing with the solar boom,” he explained. “We need faster progress on environmental permits and stronger grid connections. This is a national opportunity. It takes nine years to bring a project online, but securing grid access alone can take five, leaving just four years for construction. At this pace, I doubt we’ll be able to bring 12,000 MW to market by 2030.”

According to César Enamorado, Head of Water at Ferrovial, another challenge is the risks placed on the EPC contractor. “That approach isn’t working. We also need a mechanism to address unexpected geotechnical issues. These projects are technically complex and carry a high level of risk, especially in underground locations.”

However, he added, “they also present a great opportunity for innovation. Technologies like artificial intelligence and automation will play a key role in the efficient construction of these infrastructures. Additionally, these projects offer a chance to attract young talent to a sector that often doesn’t seem as appealing as others.”

The discussion continued with a comment on alternatives to hydraulic storage. José Ignacio Linares from the Rafael Mariño Energy Chair at ICAI highlighted thermal pumping as a promising option. He explained that, while still in development, thermal pumping could complement hydraulic storage systems: “With thermal pumping, we could use heat sources at intermediate temperatures, store them in salts or fluids from solar thermal plants, and potentially increase system efficiency to around 82%.”

Antonio Gómez, a professor at the University of Seville and an expert in electric power systems, noted that “battery costs have fallen thanks to the growth of the electric vehicle market, making them a viable alternative.” However, he emphasised that reversible pumping remains an irreplaceable option in locations suited for its use—especially in a country like Spain, which has the ideal landscape and natural sites for its development.

Finally, Tomás Sancho concluded the session by stating, “What is clear is our shared desire and objective to use our resources efficiently. It is essential to find investors to finance these projects”, paving the way for a future “capacity market.”