- Four Swiss companies spent 2 billion Euros and 14 years constructing a huge “water battery” energy storage system high in the Alps at Nant de Drance, Switzerland.
- The “water battery” consists of two large water reservoirs, one higher than the other. A giant engine room and six turbines connect them and provide the operational part of the battery setup.
- The facility can store up to 20 GWh (gigawatt hours), which is the same as 400,000 fully charged 50 kWh electric cars. Tesla equipped the Tesla Model 3 with a 50 kWh battery at its 2017 debut. However, Drive reports Tesla has boosted Model 3 battery sizes to 62 kWh to 82 kWh depending on trim since.
- Water gets pumped from the lower reservoir to the higher when excess power is available. The water is then sent back down through the turbines to create power at times of lower generation.
- The hydroelectric plant or “water battery” is needed to smooth out the electrical supply as generated by renewable sources. It’s one of several possible solutions to making the renewable energy grid stable.
- The Nant de Drance water battery has a 900 MW capacity. It’s also profitable despite its immense cost. Its 80% efficiency currently makes it one of the world’s most effective power storage systems.
Nant de Drance Water Battery: History
The Nant de Drance water battery, also called the Nant de Drance Hydropower Plant, went into operation on July 1st, 2022. Achieving this milestone resulted from years of painstaking design and construction by some of Switzerland’s and Europe’s most brilliant engineers. The site’s remote location required building 11 miles of tunnels through the Alps simply to bring the needed equipment and materials there.
The two artificial lakes comprising the Nant de Drance site preexisted the modern water battery by decades. Located more than a mile above sea level amid spectacular walls of snow-streaked alpine rock, the lower lake, Lac d’Emosson, was constructed between 1921 and 1925. Engineers built an initial dam during that period, a structure known as the Barberine Dam. Workers raised a new 590-foot dam in 1973 to address the rising need for electric power, with more expansions to follow.
The dam creating the upper reservoir, Lac du Vieux Emosson (Lake of Old Emosson), was built in the early Fifties and completed in 1955. The Swiss state did not significantly expand it. Once the Hydropower Plant project began, private construction increased the dam’s height, approximately doubling Vieux Emosson reservoir’s volume.
The Water Battery Project
A consortium of Swiss companies approached the government of Switzerland about turning the twin Emosson reservoirs into an enormous water battery in 2008. The two main members are Alpiq and SBB. Alpiq is a publicly traded utility company specializing in hydroelectric power, while SBB is the state-owned Swiss national railway company. The two other members are electric company FMV SA and Industrielle Werke Basel (Basel Industrial Works). Initially, the government approved a 600 GWh power plant, but in 2011 they upped this to 900 GWh.
Nant de Drance SA built the vast majority of the facility underground. The companies based their choice on keeping the local mountain landscape as pristine as possible. Tourists are still able to enjoy the scenery and hike the Old Emosson Geological Trail. This trail, starting at the lower reservoir dam, features 240 million-year-old petrified reptile trackways, as Swiss Mountain Fun reports.
According to cement manufacturer Sika Group, the project involved excavating around 60 million cubic feet of stone. This quantity is about two-thirds of the Great Pyramid of Giza’s volume. Sika Group turned some of the stone dug out of the mountains into specialized concrete used in building the facilities and heightening the dam.
Finishing the Project
Carried out in frigid, snowy mountain conditions on steep slopes and in remote terrain, construction took 14 years to complete. 650 workers from five dozen different companies labored at the site with advanced boring and construction equipment. Besides building the tunnels and a cavernous subterranean power house, the consortium’s construction crews raised the height of the upper reservoir’s dam. This increased the lake’s volume twofold to 25 million cubic meters, or about 6.6 billion gallons, Energy Storage News says. Boosting the size of the upper lake was a critical step in making the huge water battery capable of realizing its full electricity generation potential.
Construction finally ended and operation began on July 1st, 2022. Several officials visited the site on that date. However, Nant de Drance SA also plans a major commissioning ceremony on September 10th and 11th, 2022. Alpiq says it invites the public to tour the facilities and join the planned celebration, though reservations are limited.
Nant de Drance Water Battery: How it Works
The Nant de Drance water battery doesn’t store energy like conventional batteries, such as lithium-ion electric vehicle (EV) batteries. Instead, energy is stored and released, or generated, by moving water between the two reservoirs. The two lakes are about a thousand feet apart with Vieux Emosson at the higher level.
Renewable energy generators work irregularly depending on the weather and the time of day. Solar energy generation is reduced in cloudy or rainy weather and stops at night. Wind turbines work only when the wind is blowing. The Nant de Drance Hydropower Plant’s designers created it to stabilize this pattern.
Balancing Out Wind and Sun Power Generation
During times of high power generation, there’s plenty of surplus electricity in the grid. At these times the Hydropower Plant uses that cheap, excess energy to pump water from the lower reservoir to the upper. When power generation is low on the grid, technicians activate the water battery system by opening two approximately 1,400-foot high vertical penstocks. The water gushes down these massive pipes, each 23 feet in diameter, into six Francis turbines each able to generate 150 megawatts of energy. This accounts for the battery’s potential 990 MW total generation.
Francis turbines resemble gigantic metal snail shells. The kinetic energy of the water passing through them spins the turbines. The spinning is transmitted through a shaft to a generator. Francis turbines can convert energy at around 95% efficiency if correctly designed. Nant de Drance has only 80% efficiency overall, but this is because of the energy used to pump water into the upper reservoir. The efficiency is still high enough so the process produces positive net profits for the companies involved.
At the basic level, the Nant de Drance water battery works by using renewable electricity to pump water uphill into the upper reservoir when generation is strong. When generation weakens, the plant’s controllers let the water flow downhill through enormous turbines. These generate a huge surge of energy and pump it into the grid. The Hydroplant is an electricity user during high generation times. It becomes a powerful generator during low generation times by using the potential energy “stored” in the reservoir water to drive its half-dozen huge turbines. With evaporation low at cold temperatures and high altitudes, the device reuses the same water over and over again.
The Swiss Water Battery Control System
The six machine systems of a paired pump and turbine operate separately. This enables the personnel controlling the plant to choose how much water is pumped, or how much flows into the turbines to generate energy. It requires only five minutes to change over from pumping to turbine generation, and ten minutes for the reverse. Being able to quickly change from pumping to sluicing gives the facility plenty of operational flexibility.
Alpiq engineer Emanuele Facchinetti and his team developed a software system called the Pump Storage Management Tool, abbreviated to PSMT. Technicians at the Hydropower Plant use the PSMT to control the six turbines’ separate schedules. According to Facchinetti, the PSMT features “an optimization algorithm to manage the complex system and help the dispatchers set up production and pumping schedules for each machine.”
Nant de Drance Water Battery: Historical Significance
More than a hundred years have passed since the “water battery” form of power plant was first built in the late 19th century. However, Nant de Drance offers a much bigger scale of water battery power production than most earlier designs. It is also made to stabilize the power grid as more solar and wind energy replaces traditional power plants. The plant’s director, engineer Alain Sauthier, highlighted the facility’s size and its central location in Europe in a SwissInfo interview. He noted these elements will help it balance power production and use between different European countries in real-time.
Sauthier said that lacking the flexibility offered by the huge water battery and its quick-switch pumps and turbines can cause major disruptions in electrical supply. He remarked “you risk a collapse of the grid and blackout, as happened in Texas at the beginning of the year” without a place like Nant de Drance in the grid.
Electric vehicles are quickly winning popularity and Europe has mandated a near-future EV changeover. Strongly boosting renewable energy at a time of mounting power demand could be crucial to the EV revolution’s success. Australian university researcher Matthew Stocks guesses more than 600,000 potential pumped storage power plant sites exist around the world. Nant de Drance could be the spearhead of a water battery transformation matching and supporting the advance of EVs.