Giant concrete spheres at the bottom of the ocean could be the batteries of the future. At least that is what experts from Fraunhofer Institute believe after conducting some successful tests in the lake of Constance.
Germany is well known for the Energiewende (energy transition). The European nation is a leader in the production of renewable energy, mainly wind and solar energy. In fact, so much energy is being produced that scientists are faced with a new problem: storing it. Renewable energy production varies greatly based on sunshine and wind speed, and it does not always match demand. Because of insufficient battery capacity, not all the energy produced during peak times can be saved for high demand times, meaning that the grid still has to rely on non-renewable sources of energy (such as coal) to avoid shortages.
Giant hollow balls of concrete could be the solution. These "marine eggs" are submerged and connected to wind farms. Where the wind turbines generate power, water is pumped out of the sphere, which stores energy. When this stored energy is needed in the grid (e.g. if there is no wind), the water is allowed to flow back in the sphere through a turbine, which releases energy that is converted to electricity with a generator.
“With a storage capacity of 20 MWh per sphere and standard technology available today, we can envisage a total electricity storage capacity of 893.000 MWh worldwide. This would make an important and inexpensive contribution to compensating fluctuations in electricity generation from wind and solar power.”
- Jochen Bard, Fraunhofer IWES
The tests in the lake of Constance are just the beginning. Based on these results, the project team wants to conduct similar experiments in Norway and in the Mediterranean Sea. Considering that a large number of new windfarms are built on the water or close to it, it would be a good option to store the energy where it is produced to avoid long transfer lines.
The Fraunhofer Institute for Wind Energy and Energy System Technology (Fraunhofer IWES) is developing this new energy storage system with funding from the Federal Ministry for Economic Affairs and Energy. The project is based on an invention by Professor Horst Schmidt-Böcking (Goethe University Frankfurt) and Dr. Gerhard Luther (Saarland University).