The Fraunhofer IWES – StEnSEA – Energy Storage Project is a 5,000kW energy storage project located in Lake Constance, Germany.

The electro-mechanical energy storage project uses others as its storage technology. The project was announced in 2013 and was commissioned in 2017.


The Fraunhofer IWES – StEnSEA – Energy Storage Project was developed by Fraunhofer-Institut fur Windenergie und Energiesystemtechnik and HOCHTIEF Construction .

The key applications of the project are electric energy time shift, electric supply capacity and renewables energy time shift.

Contractors involved

Fraunhofer-Institut fur Windenergie und Energiesystemtechnik, HOCHTIEF Construction and University of Stuttgart have delivered the energy storage project.

Additional information

The project comprises the development and testing of a novel pumped storage concept for storing large amounts of electrical energy offshore. This marine pumped storage concept utilizes the sea itself as upper storage reservoir and a hollow sphere on the seabed as the lower storage reservoir. Water is being pumped out of the sphere during pumping/charging operation and water flows back into the sphere and drives a turbine coupled to a generator during generation/discharging operation.

About HOCHTIEF Construction

HOCHTIEF Construction AG is a service-oriented construction company, that engages in the construction and development of shopping centers and malls and a broad spectrum of residential complexes.


All publicly-announced energy storage projects included in this analysis are drawn from GlobalData’s Power IC. The information regarding the projects are sourced through secondary information sources such as country specific power players, company news and reports, statistical organisations, regulatory body, government planning reports and their publications and is further validated through primary from various stakeholders such as power utility companies, consultants, energy associations of respective countries, government bodies and professionals from leading players in the power sector.