large scale renewable storage

Hydraulic pumping not only improves the storage capacity of renewable energy compared to batteries, it is also capable of taking advantage of the infrastructure already existing in our country. This technology represents a flexible energy management model in the face of fluctuations in wind and solar generation, which ensures a reliable and continuous supply that improves the capacity of the electrical system.

The energy transition is advancing by leaps and bounds. Every year, wind and solar energy gain more weight in Spanish and European electricity generation, making progress in reducing carbon dioxide (CO2) emissions. However, this advance poses a challenge: How do we ensure that that energy is available at the exact moment we need it?

Production and demand peaks

The very nature of renewables is intermittent. The sun does not shine twenty-four hours a day, the wind does not always blow with the same intensity and the rains necessary for hydraulic generation are seasonal. This mismatch between production moments and demand peaks makes storage is an essential piece to guarantee the electricity supply. Currently, producing more renewables is no longer enough; The key is to conserve excess electricity to be able to release it at times of highest consumption.

The International Energy Agency (IEA) estimates that global storage capacity will have to increase five-fold between now and 2030, going from the 272 GW that was registered in 2023 to more than 1,500 GW. Spain, for its part, has set an ambitious goal in the latest update of the National Integrated Energy and Climate Plan (PNIEC 2023-2030): reaching 22.5 GW of storage by the end of this decade, compared to the current 6 GW.

Goal: store energy on a large scale

To meet this objective, our country needs to develop resources that allow it to store energy on a large scale. Along with battery storage, one of the technologies already available that will allow conserving the renewable energy and recovering it when there is more demand is hydraulic pumping, which today provides almost 85% of the electrical storage capacity installed in the world.

It is “one of the most viable and efficient solutions for energy storage on a large scale and for long periods,” he explains. Carlos Gutiérrez, Technology Manager at Repsol Renovables. It consists of two reservoirs located at different altitudes. At times of high demand, water is released from the upper tank to descend through pipes, moving turbines that generate electricity. And when there is excess renewable electricity generation, it is used to pump water back from the lower reservoir to the higher one, which will allow that potential energy to be reused when it is needed again.

“Pumping provides exceptional flexibility to the electrical system in managing fluctuations in wind and solar generation, ensuring a reliable and continuous supply,” says Gutiérrez. Furthermore, he adds that the advantage of this technology not only lies in its capacity, but also in its durability. While current batteries have a useful life of approximately 15 years due to the degradation of their materials, pumping stations can operate for several decades, as demonstrated by the Niederwartham plant in Germany, inaugurated in 1930 and still in operation.

Take advantage of infrastructure

In Spain, the project Aguayo II, in Cantabriaillustrates the potential of hydraulic pumping in the energy transition. The repowering of the Aguayo I hydroelectric plant, in operation since 1983, will allow its capacity to be multiplied by almost four, reaching 1,360 MW. “In this expansion we will not only take advantage of the upper and lower reservoirs, but also a large part of the existing infrastructure, thereby minimizing the environmental impact of the work,” he details. Luis González, deputy director of the project at Repsol.

Once completed, Aguayo will be one of the largest pumping facilities in Europe, capable of generating electricity equivalent to the average consumption of more than 500,000 homes per year, and will become a key infrastructure to integrate the growing volumes of renewables expected for 2030.