Swiss €2bn pumped hydro storage completed, media calls it a “water battery”

14-07-2022 |   |  By Robin Mitchell

As engineers continue to find economic solutions to storing excess renewable energy, the media continues to exaggerate well-established technologies with the goal of creating hype and wonder. What energy storage solutions currently exist, what has Switzerland spent €2bn on, and how has the media overreacted to such developments?


What energy storage solutions currently exist?


It is well established that renewable energies face many challenges, whether their high cost, low energy density, or unreliability. While energy storage technologies exist, they are hardly widespread, and those that do exist are often more geared towards energy storage research or as a demonstration site instead of being a mainstream commercial facility. But what technologies currently exist for energy storage?

Many energy storage technologies exist, but not all are suitable for use with large national electric grids as the amount of energy storage and instantaneous power needed is enormous. For example, Lithium-ion batteries used in many portable devices can, in theory, be used for grid storage, but some question their cost-effectiveness and safety. While they can deliver large amounts of instantaneous power, they are enormously expensive, have a limited number of charging cycles, fail catastrophically, and the fires they cause are virtually impossible to put out.

Gravity is another option for energy storage whereby lifting something heavy results in stored potential energy. If the heavy object is then lowered, it can be used to drive a dynamo that releases the potential energy. Unlike chemical batteries, such storage solutions are inherently safe as energy is not being stored in a chemical form that is prone to fires, chemical leaks, and explosions. However, the energy density offered by these solutions is often limited, meaning that large heights and heavy objects are needed to make such a setup practical.

Pumped hydro is another example of gravity storage whereby the mass being lifted is water. When energy needs to be stored, a pump is used to move water from one reservoir to another reservoir located at a higher altitude (i.e., higher than the first reservoir). When energy is needed, the water from the higher reservoir is allowed to flow back into the lower reservoir while passing through a turbine. This causes the turbine to spin, which turns a dynamo and generates electricity. This type of energy storage solution is economical as water is effectively free, it only requires two naturally occurring reservoirs, and it is simple in design. But if artificial reservoirs are used, failures in the structure can cause widespread flooding.

Thermal masses can also be used to store excess energy. During times of excess energy, a thermal mass (solid, liquid, or gas) can be heated to a high temperature. When energy is required, this thermal mass can either transfer heat to homes directly (requiring no conversion) or generate steam to power turbines and generate electricity. If the thermal mass is well insulated, such a solution can store energy for extended periods of time, and the use of electric heating makes it highly efficient (close to 100%). However, thermal masses can see significant losses if trying to convert the heat into electricity which is why it is more efficient to pump heated fluids straight into homes for use with central heating.


Switzerland completes €2bn pumped hydro installation


Over 14 years ago, Switzerland started a €2bn project to create a large-scale pumped hydro storage system with the goal of storing excess energy from the grid. The project has finally been completed and is now in operation with a total energy capacity of 20 million kWh. 

The system has a capacity to store 25 million m3 of water in its reservoirs and is said to be equivalent to 400,000 car batteries; at peak capacity, the pumped storage solution can provide power to over 900,000 homes. To create such a large facility, engineers took advantage of two naturally occurring reservoirs in the Swiss alps that are separated in height; the Emosson and the Emosson Vieux.

The installation of the new system allows Switzerland to store renewable energy when it is being generated at its peak and then later use that energy during times of peak demand. Furthermore, the use of pumped storage will help to reduce the overall carbon footprint of Switzerland as well as reduce dependencies on foreign fuel sources.



How the media have overacted


What has been developed is no small feat of engineering, and its ability to store 20 million kWh of energy is impressive, to say the least. Furthermore, storing renewable energy using a relatively safe technology is good for the environment and climate. As such, the engineers behind this project deserve to be praised for their achievement.

But it appears that the media has now decided to invent a new term for pumped hydro storage: “water battery”. Anyone from an engineering background understands that the term “battery” specifically means any device that uses a chemical reaction to generate electricity. As such, a device that stores energy using any means other than chemicals is not considered a battery.

While this need for scientific accuracy may not be perceived as important, it can have serious consequences on the public in general, and the media is often guilty of this. One consequence of scientific inaccuracy and hyped stories with made-up buzz words is that it can lead to false information becoming commonly believed facts. In the case of the pumped hydro project, the term “water battery” may confuse readers into thinking that this is the first time such a project has been created or that this uses some fundamentally different technology that can turn water into electricity.

Such reports also do a disservice to engineers who have devoted their careers to pumped hydro solutions in the past by using the wrong term. For example, if one Google’s “water battery”, only results around the Swiss project show, but if the phrase “Pumped Hydro” is Googled, then many other results come through, showing how the technology has been around for years. It is similar to when Elon Musk announced his “revolutionary” mode of transport, the hyperloop, but this had already been thought of on multiple occasions over the past 100 years.

Overall, it is disheartening to see media reports on remarkable feats of engineering that make up buzz terms to try and gain readership. It’s good to see that these projects are getting recognition, but the widespread use of the term “water battery” also shows that vast portions of the media copy each other without doing any scientific research into the topics they report. 


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By Robin Mitchell

Robin Mitchell is an electronic engineer who has been involved in electronics since the age of 13. After completing a BEng at the University of Warwick, Robin moved into the field of online content creation developing articles, news pieces, and projects aimed at professionals and makers alike. Currently, Robin runs a small electronics business, MitchElectronics, which produces educational kits and resources.

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