In an effort to reduce the use of precious land to build renewable energy storage facilities,关键字2 the Fraunhofer Institute has been cooking up a wild but plausible idea: dropping concrete storage spheres down to the depths of our oceans.

Since 2011, the StEnSea (Stored Energy in the Sea) project has been exploring the possibilities of using the pressure in deep water to store energy in the short-to-medium term, in giant hollow concrete spheres sunken into seabeds, hundreds of feet below the surface.

An empty sphere is essentially a fully charged storage unit. Opening its valve enables water to flow into the sphere, and this drives a turbine and a generator that feed electricity into the grid. To recharge the sphere, water is pumped out of it against the surrounding water pressure using energy from the grid.