The future belongs to renewable energies. But storage still poses a challenge – for example when there is no wind or sunshine. But a new pump turbine now promises to help.
Storing energy from wind and solar determines the security of our electricity supply. A team from Germany and the USA is therefore testing a pumped storage plant at the bottom of the ocean. The StEnSea project uses water pressure at depths of 650 meters to temporarily store energy. The advantage: Fluctuations in the network can be compensated for.
The system is a hollow concrete ball on the seabed that releases energy when needed. This would allow network operators to avoid having to switch off wind turbines in the event of excess capacity. The competition from China already seems to be one step further technologically, as the company Dongfang Electric has been demonstrating the function of such a system for a long time.
New pump turbine stores energy on the seabed
The Fraunhofer Institute IEE is currently working with partners such as Pleuger Industries and the company Sperra. Pleuger Industries builds the technical unit and is specifically responsible for the measurement, control and regulation technology. The company Sperra prints the ball of the pump turbine from concrete using a special 3D process.
While the one-to-three scale prototype achieves an efficiency of 0.60, the full-scale system targets a value of 0.80. In this way, the developers increase the efficiency of the memory by a third.
An example shows the interaction with wind farms on the high seas. When the wind blows when demand in cities is low, the surplus electricity drives the pumps. These transport the water from inside the concrete ball into the sea. If there is a lull or demand increases during the day, the water pressure from the depths pushes the water back into the ball.
The water passes through the turbine, which then generates electrical energy and feeds it into the power grid. Since the facilities are located on the seabed, they hardly interfere with the landscape. However, researchers are studying the impact on the underwater ecosystem. By building additional spheres, the team adapts the capacity of the facility to the needs of the corresponding region.
Synergies with the offshore industry
The test body off the US coast has a diameter of ten meters and weighs 1,000 tons. At a depth of 650 meters, the system promises a storage capacity of one megawatt hour. Later units could operate at depths of 600 to 800 meters – with a diameter of 30 meters and a weight of 20,000 tons.
The operators use synergy effects with the existing offshore industry and the wind industry. They rely on existing logistics and specialized ships to transport the heavy bullets. Existing methods for corrosion protection permanently protect the technology from aggressive salt water. The experts also take over cables and sensor systems from proven applications in gas and oil production.
The Fraunhofer IEE estimates the global potential to be over 800 terawatt hours. This value exceeds estimates for global electricity storage needs. The researchers are currently actively linking the various individual components of the memory. In addition, experts are solving the problems with laying the submarine cables, which they laid for this application for the first time.
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