How can the enormous amounts of electricity generated through offshore wind power be temporarily stored on site? Until now there was no answer to this question. After several years’ research work, the StEnSea project (Stored Energy in the Sea) funded by the Federal Ministry for Economic Affairs and Energy is now entering the test phase.
The Marine Egg, an invention by Horst Schmidt-Böcking and Gerhard Luther, two physics professors from Goethe University Frankfurt and Saarland University in Saarbrücken, is the basis for a novel marine pumped storage system developed by the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES).
A model on the scale of 1:10 with a diameter of about 3m is to be tested for four weeks: “Pumped storage power plants installed on the seabed can use the high water pressure in very deep water to store electrical energy with the aid of hollow spheres”, explains Horst Schmidt-Böcking, emeritus professor at Goethe University Frankfurt. To store energy water is pumped out of the sphere using an electric pump and to generate power water flows through a turbine into the empty sphere and produces electrical energy via a generator. Together with his colleague Dr. Gerhard Luther from Saarland University, Professor Schmidt-Böcking filed a patent for their principle for offshore energy storage in 2011, just a few days before the Fukushima disaster.
“There is great potential for the use of marine pumped storage systems in coastal areas, in particular near the coast in highly populated regions too, for example in Norway (Norwegian Trench),” says IWES Head of Division Jochen Bard. “But Spain, the USA and Japan also have great potential. With a storage capacity of 20MWh per sphere and standard technology available today, we can envisage a total electricity storage capacity of 893,000MWh worldwide. This would make an important and inexpensive contribution to compensating fluctuations in electricity generation from wind and solar power.”