13 Oct, 2022 / BY Neil Sharp

How Switzerland’s water battery will help charge Europe’s EVs

The current energy crisis is terrorising Europe’s ambition to become the first ‘climate neutral’ continent. The continent (geographical, not political) was marching towards green energy at the beginning of 2022, but the war in Ukraine stopped that like a Javelin. Even the greenest of countries, Germany, has passed a law to resurrect oil and coal-fired power plants to supply its grid. This ridicules the continent’s position on promoting EVs as sustainable transport. 

But it’s not all bad news. Fortunately, Switzerland recently unveiled an engineering project that just might help keep Europe’s lights on—and our EVs charged.  

The Nant de Drance power station 

Emosson and Vieux Emosson reservoirs lay high in the Swiss Alps, but Nant de Drance’s six turbines are hidden 600 metres underneath the mountain range. They are reversible turbines, meaning they can almost immediately change from storing energy (they act as a water battery) to supplying electricity. The power plant’s lights were turned on in July this year after the completion of a 14-year project involving 650 workers tunnelling 18 km through Alpine rock. 

The plant will stabilise the energy supply, be a significant contributor of renewable energy to Europe’s grid, and help curb emissions from burning dirty energy sources.

  • 900 MW – the capacity of the Nant de Drance plant, which is equivalent to that of the Gösgen nuclear power plant
  • 6 – the number of Francis turbines, each with a capacity of 150 MW
  • 20 million kWh – the plant's storage capacity, corresponding to the capacity of 400,000 electric car batteries
  • Less than 5 minutes – the time needed for the power plant to stop pumping at full speed and start turning the turbines at full speed; and less than 10 minutes to switch from turbine mode to pump mode.
  • 25 million m3 – the capacity of the Vieux Emosson, which is more than 6,500 Olympic-sized swimming pools

How does the water battery work?

Too much energy in the grid, and the electrical frequency increases, meaning power plants run the risk of disconnecting. But too little energy in the grid can wreak havoc everywhere, from factories to farms. So energy grids must always be balanced. And the Nant de Drance does exactly that. 

When too much energy is in the grid, the power plant pumps water from the Emosson reservoir to the Vieux Emosson reservoir, which acts as a battery storing energy to be used when needed. And when there is a dearth of energy in the grid, the water flows in the opposite direction, passing through the turbines to supply it with electricity. The two reservoirs act as a scale, always ensuring that energy levels in the grid remain balanced.

In Europe's transition to becoming the first climate-neutral continent, water batteries that store energy will be essential. This is because energy production from solar and wind (renewables) is unreliable—they often provide not enough or too much. And the unpredictable weather we face due to climate change—extreme heat waves and cold spells—also create spikes in energy demand.

Not climate neutral: EVs powered by ‘dirty’ energy 

European countries are currently promoting electric vehicles to reduce emissions and help hit climate targets. However, the transition is slower than expected. While there are several reasons for this, one is Europe’s continued reliance on ‘dirty energy’. Gas and coal-burning plants are still being fired up to produce electricity—especially during peak hours when the grid does not have much stored energy. While it is true that the lack of Russian gas flowing into the continent has exacerbated the situation, burning gas is still a dirty way of producing electricity—‘natural’ gas is a fossil fuel.

Driving an electric car that is powered by fossil-fueled power stations is absurd. If you add the environmental costs of mining metals and generating electricity from ‘dirty’ sources, EVs could be as bad for the environment as petrol cars. They must be powered by green energy—otherwise, emissions reductions will be minimal. 

For example, before the energy crisis, an EV driven in Poland (with a battery made in China) was only a third more efficient than driving a car with a combustion engine. However, an EV driven in Sweden (with a battery made in Sweden) was 87% more efficient than a normal car. The difference in these figures is because Poland’s energy mix is still dominated by fossil fuels, whereas Sweden has one of the lowest use of fossil fuels in the world. In addition, China relies heavily on fossil fuels to make EV batteries.  

The water battery is key to powering Europe’s EVs with clean energy

Projects such as the Swiss Nant de Drance power plant offer relief to European energy problems—making energy greener, more stable, and less dependent on fossil fuel power stations. 

If the European grid can rely more heavily on renewables, it is hoped that an electric car bought in 2030 will reduce CO2 emissions four-fold.

And greener EVs create a virtuous cycle. If they produce fewer emissions, it will be easier for governments and businesses to hit their targets, leading to more of them on the roads, making them cheaper, meaning more people can afford them.

And EVs themselves could also help power the grid.

The water battery can store as much energy as 400,000 electric car batteries, but in the future, EVs could also store energy and send it back to the grid during peak demand. 

Currently, several vehicle-to-grid trials are being carried out in Europe, exclusively with Nissan Leaf EVs. When plugged in, the cars are charged at a time of low energy demand (around midday). However, at times of high energy demand (between 5–10 pm), the cars send energy back to the grid—making it more stable. 

There are approximately 477,000 EVs in the UK. If the trial is a success, they could store more electricity for the grid than the Swiss water battery. 

Conclusion

If European countries want to become climate neutral, they will need to depend on renewable energy as well as batteries for when energy is scant or at times of high demand. The Swiss water battery is an excellent example of how this can be achieved. And what’s more, more clean energy will likely mean more EVs—which could even end up making the grid more stable. 

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