What are gravity batteries and how can they help solve our energy storage problems?

Despite their futuristic name, gravity batteries are already widely used.

Written by James Felton, edited by Laura Simons

IFL Science – As we move away from feeding our civilizations with ancient non-dinosaur remains, we will have to overcome some teething problems.

The first is that renewables don’t necessarily generate electricity at the precise point we need it (the wind doesn’t know—or doesn’t care—to blow harder when everyone is watching the Super Bowl, for example). On particularly windy or sunny days, too much electricity can be generated, leading to a situation where consumers pay for their electricity consumption rather than overloading the grid. But power that is not used is wasted.

Obviously, the best solution is to store this energy for later use. Storing it in conventional batteries such as lithium-ion batteries presents more environmental problems because of the way the lithium is extracted, even before we look at problems like loss of capacity when using the batteries.

One solution that is already widely used is to convert energy generated from renewable sources into potential energy for later use. And back in 1907, at the Ingwehir pump-storage hydroelectric power station in Switzerland, we used “gravity batteries” to do just that.

The idea is really very simple, but still effective. During periods when energy sources produce more energy than demand, excess energy is used to pump water up into reservoirs, converting it into potential energy. Releasing water into another lower reservoir releases this energy, which can be used by passing the water through hydroelectric generators.

The idea has also been called a “water battery,” where the energy is “stored” as water, at a slightly higher altitude than it was previously. Although the efficiency is not perfect, it is much better than wasting excess energy.

“There are losses like any storage, but the return is very good,” Alain Sautier, director of the Nantes-de-Drance hydropower station, told Reuters when the station began operating. “We have about 80% efficiency throughout the entire cycle.”

“In less than 10 minutes, we can reverse the direction of rotation of the turbines and switch from producing electricity to storing it,” Sautier added to Swissinfo. “This flexibility is necessary to quickly respond to the needs of the electrical grid and adapt to electricity generation and consumption. Otherwise, there is a risk of grid collapse and power outages.

Batteries of similar gravity could be created by moving weights up and down in abandoned mines, moving sand up when there is excess capacity, and down again when supplies are low, using a process known as regenerative braking. As challenging as the transition to renewable energy may be, involving a race toward fusion technology, at least part of the problem is as simple as moving some things up and then letting them fall back to the ground later.


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