Munich. On behalf of the Schwäbisch Hall district administration, TÜV SÜD carried out the structural assessment of the towers, water reservoirs and foundations of the Gaildorf natural energy storage plant in Germany, the world’s first combined wind-pumped storage project. The pilot project includes the first realisation of the water battery concept developed by Max Bögl Wind AG. The natural-energy storage plant comprises four wind turbines and one pumped-storage hydropower plant. Even for the experienced experts from TÜV SÜD, the complex project presented a major challenge.

The water battery is a new power-station concept developed by Max Bögl Wind AG, now implemented in practice for the first time at the Gaildorf natural-energy storage plant. The water battery at Gaildorf comprises four wind turbines and one pumped-storage hydropower plant. The water battery uses the foundations of the hybrid tower system developed by Max Bögl as water reservoirs. Pipelines connect these reservoirs to a hydropower station and the associated lower reservoir, located 200 m below in the valley. Excess power is used to pump the water up and fill the reservoirs in the towers. The reservoirs are emptied at times of peak demand when power is needed. The water reservoirs increase the hub heights of the four wind turbines by 40 metres to 155 and 178 metres respectively. Gaildorf is thus the location of the current world’s highest wind turbine. According to Max Bögl, the modular concept of the water battery is a storage solution suitable for all types of regenerative energy.

Solution-focused testing and inspection of technical innovations

The innovative concept of the natural energy storage plant in Gaildorf also presented major challenges to the TÜV SÜD experts. “The full scope of our expertise and our extensive experience with certification and inspection of concrete and hybrid structures for wind turbines are specifically valuable in the realisation of sophisticated and complex projects of this kind”, says Stephan Mayer, Project Manager TÜV SÜD Industrie Service GmbH. After commissioning by the Schwäbisch Hall district administration, the TÜV SÜD experts started their work in April 2015.

“In innovative projects such as the natural energy storage plant in Gaildorf, changes compared to the original planning are inevitable”, explains Mayer. “This requires a high level of commitment and flexibility by all stakeholders.” This also applies for the solution-focused assessment of technical innovations during the construction of water reservoirs using pre-fabricated concrete parts and innovative pre-stressed concrete solutions. When certifying the water reservoirs that also served as foundations for the hybrid towers, the TÜV SÜD experts needed to combine very complex demands regarding tolerances and water tightness with highly dynamic stress conditions resulting from the wind turbines.

In consultation with the Schwäbisch Hall district administration, the TÜV SÜD inspectors also supervised the construction of the hybrid towers in 2017. Again, TÜV SÜD’s know-how and experience in this field were crucial for winning the contract. The four wind turbines will feed electricity into the grid from December 2017 onwards, while full-scale operation of the total water battery in Gaildorf is expected to start in autumn 2018.

Wind energy services from TÜV SÜD

TÜV SÜD looks back on a long and successful track record in the certification of both onshore and offshore wind farms, wind turbines and their components. The international testing and certification organisation also supports planners, contractors, investors and owners in technical assessment and inspection of all components and in risk analyses, occupational health and safety concepts and quality assurance during construction. Other core fields of activity include quality assurance in component manufacturing, and periodic testing and inspection throughout the service life of the wind turbines.