This Swiss lake is also a huge 900 MW battery

Not all batteries run on dangerous chemicals.

In Switzerland, near Nant de Drance, a huge 900 MW battery has finally seen the light of day after 14 years of construction. And if this project took so long, it’s because the battery in question has little to do with the one that powers your smartphone or your car. Here, we are not talking about gigantic clusters of nickel, cobalt and lithium, but… of a perfectly normal lake.

Very briefly, a batteryit is neither more nor less than a potential energy reserve, that is to say energy that can be restored in another form at the end of a conversion. For example, a spring accumulates potential energy when it is compressed and releases it mechanically when it is released.

In traditional batteries, this potential energy is chemical ; when it is connected, it is a reaction between the anode, the cathode and the electrolyte which makes it possible to restore the energy of the system in the form ofelectricity.

But even in a battery, this potential energy does not have to be chemical. It can also take other forms. When you lift an object, it also accumulates potential energy due to gravitation. And it will seek to return to an energetically favorable state, that is to say more stable — a bit like a compressed spring that wants to relax at all costs.

When the object is dropped, it returns this energy by falling to the ground. And it is precisely this concept that is at the heart of the operation of these “water batteries”; it is potential energy gravitational.

Potential energy from gravitation

The idea is very simple, ingenious and elegant at the same time. It rests on two basins located at different heights. When the demand for electricity increases occasionally on the network, as is the case for example in the early evening, it suffices to open the valves in the highest lake.

Some of its contents are then free to flow into the reservoir below. But along the way, it also spins turbines cleverly positioned along the way to generate electricity using gravity alone. This amounts to converting gravitational potential energy into electricity.

In other words, we dump the battery to the mains. And to recharge it, all you have to do is pump the contents of this reservoir towards the lake at altitude, and you’re done; all that remains is to open the floodgates to start a new cycle.

To sum up, it’s a bit like a closed circuit hydroelectric dam. But it is important to note that it is not a means of energy production! In the same way that a chemical battery is not able to recharge itself, water cannot make the reverse path on its own and therefore energy must be spent; technically, this therefore remains a means ofstore energy, not produce it.

An old concept adapted to today’s challenges

But what is very interesting with this approach is its strength and flexibility. Indeed, it can start producing electricity very rapidly from the first peaks of consumption. This is a big advantage compared to other means of production, which can be relatively slow to get started. This therefore allows respond quickly to a shortage.

This is all the more interesting in the era of renewable energies. Indeed, despite all their advantages, these technologies often have the defect of being intermittent ; the balance of wind energy remains zero as long as the air is calm, like that of photovoltaics during the night, and so on. With such technology, it is possible to store this energy and restore it laterregardless of the weather.

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Doing without the dangerous high-voltage chemicals found in standard batteries is also a big plus. © 7News

In addition, this approach makes it possible to take advantage of energy market fluctuations. Thanks to its responsiveness, it helps amortize the price per kilowatt-hour during peak consumption. Conversely, water can be pumped back overnight, when prices are much more reasonable.

An evolution to follow

The Swiss project is not the first in the world, far from it. The Dinorwig hydroelectric power station, which operates on this concept, has also housed the largest battery in the United Kingdom for a few years. It lost this title with the inauguration of a huge solar power plant in Wiltshire in 2021, but it remains a essential element of the English network.

There are also plants of this type in the United States. According to Interesting Engineering, China also plans to build a gigantic battery of this type by 2025.

Even if this concept is advantageous in many respects, it has not yet really democratized for rather obvious reasons. For starters, not all territories are suitable. And even when this is the case, its implementation also involves pharaonic work. Swiss engineers, for example, needed 14 years to dig almost 20 km of tunnels through the Alps.

But the game was worth it, since the 900 MW of this battery can now supply more than 900,000 homes. It will therefore be very interesting to see how widespread this technology will become over the next few decades. In the meantime, those who want to visit this engineering marvel can do so by registering now for the open doors next September (at this address).

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