Starting in 2018, Germany will no longer operate hard coal mines. However, these abandoned mines could receive a new life to make a great contribution to the development of renewable energy in the country. They could start to store the excess of wind and solar power during the hours with high renewable production by pumping water into the mines, working as giant batteries to serve the electricity market.

According to Bloomberg, the 50 year old coal mine of Prosper-Haniel will became a 200-MW pumped hydropower plant to feed more than 400,000 homes. This installation was used to power the German industry for decades, and now it will keep on powering it, but through renewable electricity.

The operation will be simple. When there is an excess of wind and solar energy (during windy and sunny days with lack of electricity demand), it will be used to pump water from the mine tunnels into an artificial lake over the former mine grounds. When the demand of electricity increases in the country (for instance, at night) the floodgates will be opened, the water will drop through the giant pipes, and it will be driven to the turbines 1,000 meters below the surface, generating up to 200 megawatts of power to feed the German grid with clean and cheap energy.

This new plant will be located in the state of North-Rhine Westphalia and has been developed in collaboration with the University of Duisburg-Essen. To make a power comparison, the nearby Emsland Nuclear Power Plant has a capacity of 1,363 MW. There is more information at the official website of the project.