Why not store energy In hollow tanks on the bottom of the sea? The German Fraunhofer Institute started a test with spherical storage tanks.
In November 2016, the first tank has been placed at the bottom of the Bodensee, near the German border with Switzerland.
Ultimately, the aim is to place the tanks in the area of offshore wind farms. But for now, the institute choose the lake because it is more practical for the tests. Read More