Switzerland is about to bring online one of the world’s largest pumped water facilities. For 14 years, the Nantes de Drance facility has a maximum energy storage capacity of 20 gigawatt-hours. And of course, being a pumped water system can theoretically store energy for months or even years, something battery storage technology can’t do so easily.
The installation uses gravity. The Emosson Reservoir is a man-made lake built in 1955 high in the Alps near the border with France and has a capacity of 25 million cubic meters (about 6.5 trillion gallons). Over the past 14 years, kilometers of tunnels have been dug to connect the mountains to the Vieux Emosson reservoir in the south.
In between is a huge underground cavern, tall enough to fit the Eiffel Tower, where six of the world’s largest water-driven turbines await water flowing down from above to spin and generate electricity. Between 2012 and 2016, the height of the Vieux Emosson dam was raised by approximately 20 meters to increase the reservoir’s capacity and thereby store more energy. Swiss information.
The theory behind pumped hydro is simple. Fill the upper reservoir and let the water flow down the ramp to power turbines when you need electricity. When you have plenty of electricity, use it to make water disappear for later use. “This is an ecological battery that uses the same water over and over again. “The output is more than 80% – for every kilowatt-hour of electricity used to pump water upstream, 0.8 is fed into the grid,” explains Alain Sauthier, chief engineer and director of the Nantes de Drance pumped water plant. “The reservoir’s electrical storage capacity exceeds 400,000 electric car batteries.”
“In the future, as renewable sources gradually replace nuclear and fossil energy, it will be more necessary to store large amounts of electricity,” says Sauthier. He adds that solar and wind power are volatile resources and don’t necessarily produce electricity when needed, which is why systems like this are so important. They can store energy and help keep the entire European power grid stable.
Inside the Nantes de Drance pumped hydro plant
Since the project began 14 years ago, 18 kilometers of tunnels have been cut between the two reservoirs into the Vale Alps. Heavy vehicles used these tunnels to bring all the materials and equipment needed to complete the project, from prefabricated office buildings to ball valves weighing more than 100 tons. The engine room at the center of the system is 200 meters long, 32 meters wide and 52 meters high. With a capacity of 900 megawatts, Nantes de Drance is one of the most powerful generating stations in Europe.
Sauthier is particularly proud of its 6 pump/turbines, which are almost unique in the world in terms of their large size and the technology used. “In less than ten minutes, we can reverse the direction of rotation of the turbines and switch from electricity generation to storage. Such flexibility is essential to respond promptly to the needs of the electricity grid and to adjust the production and consumption of electricity. Otherwise, you risk grid collapse and blackouts like what happened in Texas earlier this year.”
According to Sauthier, the plant is vital to guarantee electricity supply and grid stability, “but it is too big for Switzerland”. “This can play a role in stabilizing the network at the European level. We are geographically in the center of the continent and energy flows through Switzerland. “If there is an overproduction of wind energy in Germany, we can use the excess electricity to pump and store water.”
The Nantes de Drance power station is owned by a consortium led by electricity producer Alpig and the Swiss Federal Railways. Once it’s up and running, it needs to be profitable to justify the investment needed to make it a reality. This is no easy feat in a sector that has had to contend with financial difficulties and the unpredictability of the electricity market in recent years.
“We are working on the price difference. We have to react quickly and pump when the price is low and (generate electricity) when it is high. Earlier, we used to use the turbines during the day and pump at night, but now the situation has changed and consumption peaks in the late evening,” says Sauthier.
Nantes de Drance will be fully operational for commercial production by summer 2022. Its owners hope that it will become profitable once nuclear plants are finally shut down and renewables move away from fossil fuels.
616,000 Pumped Hydro Sites Worldwide
According to Matthew Stokes of the Australian National University, there are 616,000 sites around the world where closed-loop pumped water facilities could be built. Building only 1% of them can solve all the problems of storing intermittent energies based on geographical considerations alone, he says.
In the future, pumped-storage power plants will allow larger volumes of green electricity to be stored and then released during shortages, writes the Association of Swiss Electricity Companies. “Thanks to its power plants, Switzerland can help balance disturbances in electricity production in Europe. However, we should not overestimate their role, it directly depends on the capabilities of the existing lines,” the association adds.
“Pumped storage is a mature technology,” says Benoit Revaz of the Swiss Federal Energy Office. However, according to him, more progress is needed to make the system more flexible than the current working conditions. Together with 11 other countries, Switzerland is participating in an international forum aimed at revitalizing the development of pumped storage in electricity markets.
There could not be a better time for Europe to launch the Nantes de Drance pumped water facility this summer. Russia’s war crimes against Ukraine have rattled European energy markets as supplies of cheap methane from Russia have been severely curtailed.
Switzerland plans to take a number of steps to reduce electricity demand this winter. First, the government will require voluntary conservation steps, then it plans to prevent non-essential uses such as lighting storefronts, using mobile heaters or other uses of nighttime lighting. Ultimately, it could order up to 30,000 companies to save up to 30% of their electricity use if needed. It is estimated that these three steps can reduce energy demand by up to 30%. As a last resort, the government can shut down parts of the electricity grid.
“You have to think of it as a puzzle. Individual segments will be removed for four hours, then restarted while others are removed. Some parts of the grid – pieces of the puzzle – will be without power for four hours, then have power again for four or eight hours, depending on the situation,” says Michael Frank, director of the VSE association of Swiss electricity companies. Reuters.
Pumped hydro may be seen as a magic bullet by many proponents of renewable energy. But at 14 years from start to finish, development times are similar to new nuclear power plants – in other words, too long. Moreover, it cannot be built everywhere, meaning that high-voltage transmission lines must be built to connect renewables to storage.
But for situations where it makes economic sense, it’s a brilliant solution to the energy storage problem. There are no deposits of lithium, nickel, cobalt or manganese that need to be mined or processed to produce batteries. The only active medium is water, and therefore there are no carbon emissions associated with pumped water installations once construction is complete. Some even suggest that water in reservoirs is the perfect opportunity to add a floating sun to the picture, which seems like a match made in heaven for renewable energy advocates.
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