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Vibrating instead of hammering: new research project investigates innovative installation technique for offshore foundations

“VISSKA” is the German acronym for a research project aimed at aimed at exploring the use of vibratory pile driving at the Kaskasi II offshore wind farm, in terms of installation, noise emissions and impacts on harbour porpoises. BioConsult SH and RWE Renewables, itap GmbH as well as the University of Stuttgart (Institute of Geotechnical Engineering) and Technische Universität Berlin (Foundation Engineering and Soil Mechanics) just recently signed a corresponding cooperation agreement. The German Federal Ministry of Economic Affairs and Energy is funding the research project, which is being coordinated by RWE Renewables.

This year, RWE Renewables will start constructing the Kaskasi offshore wind farm (342 megawatts) off the German island of Heligoland. It will be the first offshore wind farm in the world to use the improved installation method for driving the wind turbine foundations into the seabed to target penetration depth. The innovative vibro pile driving method significantly speeds up the process of installing the foundations, is gentler in its impact on the structure and produces far less noise.
Up to now, foundations for offshore wind turbines have been driven into the seabed with individual blows from a hydraulic hammer. The new, reduced-noise process uses vertical vibrations to drive the foundations into position.

The pilot at Kaskasi is accompanied by a comprehensive research project. Together, the partners want to develop forecast models for installing monopiles using the vibro pile driving method, the associated noise emissions, and to validate these models through measurements in offshore conditions.
The response of harbour porpoises to continuous noise in contrast to impulse noise in terms of avoidance or displacement of these animals is still largely unknown. To gain more insight into this, BioConsult SH surveys harbour porpoises in digital aerial surveys (HiDef) and continuous recording of echolocation sounds using C-PODs in and around the site of offshore wind farm “KASKASI II” prior to, during and after vibratory piling. These data will allow to detect a possible response of harbour porpoises during construction works and to evaluate the acoustic effect of vibratory piling in the context of the protection of these animals.

The first offshore surveys are scheduled for summer 2021. The overall 38 foundations for the wind turbines will be installed from the third quarter of 2021 onwards. The final report of the 28-month research project is to be completed by early 2023.
The project’s objective is to build and expand on the results from previous research in the area of vibro pile driving. In the long term, the innovative pile driving method is to be established as a lower noise and more environmentally friendly alternative to conventional hammering techniques.