Pumped storage |
Above: Production of the 30m spheres for a StEnSea Park. ©Sperra
to each other. Moreover, conventional underwater
motor pumps can still be used at this depth. High- strength special concrete is also not necessary here. There are more than enough potential locations for StEnSea spherical storage at this depth, as a GIS analysis of coastal marine areas shows. Fraunhofer IEE experts have taken parameters like bottom slope, currents, sediment displacement, or distance to land into account. For example, off the coasts of Norway, Portugal, the US East and West Coasts, Brazil, or Japan, the spherical storage could be installed in large numbers. The technology is also suitable for deep natural or artificial lakes, such as flooded open-pit mines. Fraunhofer estimates the global storage potential
Below: Production of the 10m prototype in the current project. ©Sperra
of this technology is 817,000GWh in total. At the ten best European locations, it is still 166,000GWh. In comparison, the capacity of existing pumped storage power plants on land in Germany is just under 40GWh. Fraunhofer IEE researchers estimate storage costs at
around 4.6 cents per kilowatt-hour, investment costs at 1354 euros per kilowatt of power, and 158 euros per kilowatt-hour of capacity. The lifespan of the concrete sphere is 50 to 60 years, with pump turbines and generators needing to be replaced every 20 years. The efficiency over an entire storage cycle is slightly lower than that of a conventional pumped storage power plant, at 75 to 80%. This calculation is based on a storage park with six spheres, a total power capacity of 30MW and a capacity of 120MWh, with 520 storage cycles per year. StEnSea spherical storage is particularly suitable for two business models: for arbitrage, ie, buying electricity at low and selling at high market prices, and for providing ancillary services to stabilise power grids.
Scaling the technology After the successful test in Lake Constance, the next
step is to test the application in deep water under offshore conditions with the new project. The goal is to investigate and evaluate all steps along the manufacture, installation, operation, and maintenance regarding the intended size of the sphere. “With the global energy transition, the demand
for storage will increase enormously in the next few years,” says Bernhard Ernst of Fraunhofer IEE. “With the StEnSea spherical storage, we have developed a cost-effective technology that is particularly suitable for short to medium-term storage. With the test run off the US coast, we are making a big step towards scaling and commercialising this storage concept.” As Sebastian Rose, Head of Engineering at Pleuger Industries, adds: “Our involvement in the StEnSea project underscores Pleuger’s commitment to innovation and sustainable energy solutions. With the significant support from both the US and German governments, we are transforming energy storage and contributing to a future where clean energy is more accessible and reliable for everyone.”
30 | February 2025 |
www.waterpowermagazine.com
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