Stensea research project

Frankfurt/M., Germany

In the deep sea near the coast, StEnSea stores excess power.
In the deep sea near the coast, StEnSea stores excess power.

In the course of the energy transition, suitable energy storage systems are increasingly needed in Germany. To this end, the Fraunhofer Institute's Stensea (Stored Energy in the Sea) research project is investigating a novel system for an underwater pumped storage power plant and testing it in model trials. The operating principle is similar to that of conventional pumped storage power plants. A hollow concrete sphere with an integrated pump turbine is installed on the seabed as the lower reservoir. The surrounding sea represents the upper reservoir, with the pressure difference corresponding to the head of a conventional pumped storage power plant. When energy is needed, a valve is opened and water flows into the hollow concrete sphere, driving the turbine to generate power. If excess energy is available, the water is pumped out of the cavity against the water pressure. In this way, the energy storage system is charged. In cooperation with the research facility, HOCHTIEF developed and built a functional model and successfully tested it in Lake Constance. The main challenge was to cast a three-meter sphere. Following the successful test in Lake Constance, the next stage will be to test a concrete sphere three times as large in the sea, which will then be able to store around 50 to 100 times as much energy.



  • Successfully completed model test 2016-2017