disused mines to easily store renewable energy!

We have found an ingenious and relatively cheap way to store energy from solar or wind power: recycling deep disused mines into “gravity batteries”. The first experiment will take place in Finland.

To store irregular or intermittent production coming from the sun or wind, disused mines offer an interesting and inexpensive solution. It’s about making them into gravity batteries (or gravity batteries) to be precise. The first will be built north of Helsinki in Finland, in one of the deepest mines in Europe.

Weights lifted then released

The principle is simple: weights are placed at the bottom of a mine. They are hung at the end of ropes from a winch at the top of the well. When excess solar or wind energy is produced, it will power an electric motor which will raise the weights. Then, when we need to recover energy, typically when there is no more wind or sun, we let the weights fall by gravity. They will then turn a dynamo and generate electricity.

Until now, it was mostly a concept with some experimentation. But this time, it is a first commercial installation, connected to an electrical network. This project is led by the start-up Gravitricity.

According to their calculations, the capacity of the battery would be around 2 MWh (megawatt hours), or the equivalent of around thirty electric car batteries. This doesn’t seem like much, but the objective is not to power homes. It is more about responding to peaks in consumption. For example, when there is a cold snap, it will be sufficient and above all more ecological than relying on coal-fired power plants.

Huge potential

There are other types of gravity batteries, like those being tested by the start-up Energy Vault in China. But they require the construction of immense towers, to the top of which the weights are raised. The advantage of relying on mines is that the infrastructure already exists. It will therefore be much cheaper and more discreet since everything happens underground.

Many other sites could be envisaged, even in France. The only constraint is to have a well at least 300 meters deep. The potential is therefore enormous with all the coal mines closing all over Europe. It would even be the height of energy transition to transform them into batteries to store renewable energy.