The Stored Energy In The Sea Project

The Stored Energy in the Sea (StEnSEA) project is a new pumped storage system aimed at large-scale marine storage of electrical energy.

There is currently a lack of storage within the UK grid system and but it is expected that storage levels will triple worldwide by 2030, while installed capacity is expected to multiply more than four times over.

Considering the fact that there were roughly 4.3GW of European offshore wind energy in 2012 and there is expected to be more than 150GW installed by 2030, renewable energy should surpass the EU’s target (20 percent) significantly.

What Is It?

The StEnSEA project helps with the development, testing and increase of offshore electrical energy storage. It consists of a 30 m diameter sphere, 2.70 m walls and a large pump turbine that will be submerged underwater. The operating principle is rather similar to that of the conventional pumped storage unit and includes many of it’s key aspects.

While the water pressure’s depth acts as somewhat of a hydraulic system for the kinetic energy, excess wind and solar energy will be used to pump the water out and charge the spheres. If for any reason the wind and solar power fail to do their job, it will enable water to enter back into the spheres and cause the turbine to discharge the spheres by generating additional electricity.

Through the thoroughly tested and developed storage concept, the sea will be used as somewhat of a storage compartment. Soon after the water is pumped out of the seabed’s hollow sphere, it flows back into the sphere in order to drive the turbine during the discharging phase.

While the eventual storage volume is expected to be 12,000 m and the capacity is expected to be 5-6 MW, the project will need a water depth of at least 700 m. Fortunately for the StEnSEA, their “underwater pumped hydro system” has been thoroughly and successfully tested.

Before the StEnSEA project officially began, a pre-study was done comprising a thorough and detailed analysis of the construction needed for it’s implementation. By analyzing these important details and running tests in inland lakes, an exact blueprint was formulated which lead to the StEnSEA project.


Countries such as Spain, France, Portugal and Italy have already installed wind parks equipped with deep water floating devices. The project has also received a tremendous amount of backing, reporting worldwide investments in their power plants, air compressors and batteries to be somewhere near $200 billion by the year 2030.

Considering the fact that the uptake is also less expensive than fossil fuel, this renewable energy storage system could be world changing.