Enlit on the Road visited La Muela, the largest pumped storage hydropower plant in Europe, to find out how Iberdola’s giant battery optimizes the ROI of renewable energy sources and enables grid stabilization for the region of Valencia.
Borja Gonzales doesn’t need to think twice: La Muela is the “crown jewel” of Iberdrola’s energy portfolio in Spain.
The Director of Mediterranean Generation has been working in the hydropower department of the company for more than 18 years, but walking around the hydropower plant still makes him smile.
“Every hydropower plant is unique, and different, and they are located in very beautiful places,” says Gonzales. “And besides, hydro technology is stable technology, sustainable technology, and we are green energy.”
La Muela’s giant storage capacity
Enlit on the Road had good reason to visit La Muela, which is part of Ibedrola’s Cortes-La Muela hydropower complex, because it plays a crucial role in the optimization of the company’s renewable energy assets such as wind and solar.
The plant, located in the Júcar river basin about 1,5 hours southwest of Valencia, Spain, was commissioned in 1988, and got a second phase in 2014. With a total investment of €1.2 billion and a capacity of more than 1,800MW in generation and 1,293MW in pumping, it is a force to be reckoned with.
La Muela functions as a giga battery and this storage capacity is increasingly required now that more and more intermittent renewable energy sources are coming online.
“We use the surplus energy when there is low demand in the system to pump water from the lower reservoir to the upper one,” explains Gonzalez. “We use the water we have stored in the upper reservoir to produce energy when the system requires it.”
La Muela has two penstocks, a surface penstock from the first phase, and an underground penstock for the second phase. Says Gonzalez: “We have a net height of 500 meters between the upper reservoir and the lower reservoir. Both turbines are Francis. We have three different units in phase one and four units in phase two.”
Gonzales remembers the days when they had only one cycle per week. That has changed completely. “Nowadays, we are talking about two or three different cycles. Why? Because the number of megawatts of non-manageable renewable technologies in the system has increased a lot. So that’s the reason why this kind of asset, this technology of pumped storage, is very important for the system, because we give stability and we give firm energy.”
Pumped storage in times of extreme weather
And it is not just the capacity that stands out, the quick response time also makes pumped-storage the most efficient system to store energy on a large scale and provide grid stability. “We can go in La Muela from the minimum power to a full power in a matter of seconds,” explains Gonzales.
This flexibility was proven invaluable during the extreme rainfall that caused unprecedented flooding in the region of Valencia in October 2024. Due to the extreme weather, there were many problems with transmission and distribution lines.
Gonzales remembers the day as a “really difficult day for everybody”. However, he is grateful for the way the hydropower team was able to assist.
“We have to think that the La Muela hydropower plant provides energy for a lot of households every year, so that day, it was very important to give stability and safety to the system. So that’s why the system operator requested us to start our turbines and to produce energy as soon as possible. In a matter of three/four minutes, we were at full power. It’s important to have a different mix of different energies to avoid a blackout.”
Despite its vital role in mitigating the impacts of climate change, La Muela itself is designed to be resilient. “We are in a closed loop, so we don’t have any water consumption, so we can use the water as many times as we want,” Gonzalez clarifies. “We are not affected by the climate condition.”
The future of pumped storage hydropower in Spain
In anticipation of the increasing number of renewable energy in the system, Gonzales says that Iberdrola is interested in developing new pumped storage hydropower.
“We have very important assets here in Spain, also in the north of Portugal. We have just commissioned a new pumped storage in the north of Portugal, very similar to La Muela.”
Gonzalez believes that this strategy will benefit Spain’s energy transition.
“We are going through huge electrification in the system, and it’s very important to be able to integrate these non-manageable renewable technologies that this kind of assets, like La Muela can do.”
Originally published by Julia Kramer in Enlit
