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August 8, 2022
By
Steve Hanley
14 Years In The Making, 20 GWh
Pumped Hydro Storage Facility Comes To Switzerland
Image credit: Nant de Drance / Sébastien Moret
One of the largest pumped hydro
facilities in the world is about to go online in Switzerland near the
border with France.
Switzerland is about to bring one of the
largest pumped hydro facilities in the world online. 14 years in the
making, the Nant de Drance installation has a maximum energy storage
capacity of 20 gigawatt-hours. And of course, being a pumped hydro
system, it can theoretically store energy for months or even years,
something battery storage technology cannot do as easily.
The installation uses gravity. The
Emosson reservoir is an artificial lake built high in the Alps near
the border with France in 1955 and has a capacity of 25 million cubic
meters (about 6.5 trillion gallons). Over the past 14 years, miles of
tunnels have been dug into the mountains to connect it to the Vieux
Emosson reservoir to the south.
In between is a giant underground cavern
tall enough to fit the Eiffel Tower, where 6 of the largest
water-driven turbines in the world are waiting for water rushing down
from above to make them spin and generate electricity. Between 2012
and 2016, the height of the Vieux Emosson dam was raised by some 20
meters to increase the reservoir’s capacity and thus store more
energy, according to a report by
Swiss Info.
The theory behind pumped hydro is simple.
Fill the upper reservoir and when you need electricity, let the water
flow downhill to power turbines. When there is an abundance of
electricity, use it to pump water back uphill for use later. “It is an
ecological battery that uses the same water over and over. “The output
is more than 80% — for every kilowatt-hour of electricity used to pump
the water upstream, 0.8 is fed into the grid,” explains Alain Sauthier,
chief engineer and director of the Nant de Drance pumped hydro
facility. “The electric storage capacity of the reservoir surpasses
that of 400,000 electric car batteries.”
“In the future, it will be increasingly
necessary to store large amounts of electricity, as renewable sources
gradually replace nuclear and fossil energy,” Sauthier says. He adds
that solar and wind power are volatile resources that do not
necessarily generate electricity when it is needed, which is why
systems such as this are so important. They can store energy and help
keep the entire European electrical grid stable.
Inside The
Nant de Drance Pumped Hydro Facility
Image credit: Nant de Drance /
Sébastien Moret
Since the project began 14 years ago, 18
kilometers of tunnels have been cut into the Valais Alps between the
two reservoirs. Heavy vehicles used those tunnels to bring in all the
material and equipment needed to complete the project, from
prefabricated buildings with offices to ball valves weighing over 100
tons. The engine room at the heart of the system is 200 meters long,
32 meters wide, and 52 meters high. With a capacity of 900 megawatts,
Nant de Drance is one of the most powerful generating plants in
Europe.
Sauthier is especially proud of the 6
pump/turbines, which are almost unique in the world in terms of their
sheer size and the technology used. “In less than ten minutes, we can
reverse the direction of rotation of the turbines and switch from
electricity production to storage. Such flexibility is key in order to
react promptly to the needs of the electricity grid and adapt
electricity generation and consumption. Otherwise, you risk a collapse
of the grid and blackout, as happened in Texas at the beginning of the
year.”
The plant is vital in order to guarantee
electricity supply and grid stability, “but it is far too big for
Switzerland,” according to Sauthier. “It can play a role in
stabilizing the grid at European level. We are geographically at the
heart of the continent and energy flows pass through Switzerland. If
there is an overproduction of wind power in Germany, we can use the
surplus electricity to pump and store water.”
The Nant de Drance power plant is owned
by a consortium led by electricity producer Alpiq and Swiss Federal
Railways. Once it is operational, it will need 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
differential. We need to react quickly and pump when the price is low
and (generate electricity) when it is high. In the past, we used the
turbines by day and pumped by night, but now the situation has
changed, with consumption peaking late in the evening,” Sauthier says.
Nant de Drance will be fully operational
for commercial production by summer 2022. Its owners hope it will
become profitable once nuclear power plants have finally been shut
down and when renewable energy sources have taken over from fossil
fuels.
616,000
Pumped Hydro Sites Worldwide
According to Matthew Stocks of the
Australian National University, there are
616,000 sites around the world where closed circuit pumped hydro
facilities could be built. Building just 1% of them could solve all
problems associated with the storage of intermittent energies based
solely on geographical considerations, he says.
In the future, pumped storage power
stations will enable the storage of ever greater amounts of green
electricity, for release later in times of shortage, writes the
Association of Swiss Electricity Companies. “Thanks to its power
plants, Switzerland can help balance irregularities in electricity
production in Europe. However, we should not overestimate their role,
which above all depends directly on the capacities of existing lines,”
the association adds.
“Pumped-storage hydro-power is a mature
technology,” says Benoît Revaz of the Swiss Federal Office of Energy.
More progress is needed however, he believes, to make the system more
flexible compared with current operating conditions. Together with 11
other countries, Switzerland is taking part in an international forum
aimed at reinvigorating the development of pumped hydro storage in
electricity markets.
Serendipity
Bringing the Nant de Drance pumped hydro
facility on line this summer couldn’t come at a better time for
Europe. The war crimes being perpetrated by Russia on Ukraine have
roiled European energy markets as the supply of cheap methane from
Russia has been dramatically curtailed.
Switzerland is planning a number of steps
to lower the demand for electricity this winter. First the government
will request voluntary conservation steps, then it plans to curb
non-essential uses like illuminating shop windows, using mobile
heaters, or other uses of nighttime lighting. Finally, it could order
as many as 30,000 companies to save up to 30% of their electricity
usage if necessary. It is estimated those three steps could cut power
demand by up to 30%. As a last resort, the government could shut down
parts of the electrical grid.
“You have to imagine this as a puzzle.
Individual segments would be removed for four hours, then turned back
on while others are removed. Some parts of the network — the pieces of
the puzzle — would have no power for four hours, then have power again
for four or eight hours again depending on the situation,” Michael
Frank, director of the VSE association of Swiss electricity companies,
tells
Reuters.
The Takeaway
Pumped hydro may seem like 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, way too long. Plus, too, and also, it can’t be built just
anywhere, which means high voltage transmission lines need to be
constructed to link the renewables with the storage.
But for those situations where it makes
economic sense, it’s a brilliant solution to the energy storage
problem. There are no lithium, nickel, cobalt, or manganese deposits
that have to be mined or processed in order to manufacture batteries.
The only active medium is water and so once construction is complete,
there are no carbon emissions associated with pumped hydro facilities.
Some even suggest all that water in the reservoirs are a perfect
opportunity to add
floating solar to the picture, which does seem like a match made
in heaven for renewable power advocates.
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