German noise emission mitigation
Topic of the practice
Good Practice Information
The research project ESRa (evaluation of systems for the reduction of ramming noise) tested various new noise reduction systems designed to mitigate the spread of ramming noise when installing foundations for offshore wind farms. To this end, a field test was conducted in the German Baltic Sea approximately three kilometres off Travemünde in August 2011. A total of five novel noise mitigation systems were tested on a test pile in Neustädter Bucht. The companies Bard Engineering, DONG Energy, EnBW Erneuerbare Energien, E.ON Climate Renewables, EWE Energie, RWE Innogy, Stadtwerke München and Vattenfall participated in the ESRa project. Different sound mitigation concepts were used on the so-called Brodtener pile at a water depth
of about nine metres; they work with air-filled enveloping bodies, multi-layer hose curtains bubble curtains and combinations of acoustic cladding and bubble curtains. All systems were used under identical ambient conditions: the test was designed to compare the potential noise mitigation levels with one another by way of a uniform measurement protocol. The Institut für Technische und Angewandte Physik (ITAP – Institute for Technical and Applied Physics) at Oldenburg developed a specific measuring and evaluation concept for underwater noise measurements. The institute also conducted and evaluated the measurements. Each of the noise mitigation systems manufactured as prototypes withstood the harsh conditions at sea and demonstrated a noise-mitigating effect. When corrected for site-specific effects, the mitigation effect totalled up to nine decibels in the relevant range. This brought the noise level much closer to the noise emission limit of 160 decibels at a distance of 750 meters around the source of the noise.
Evidence of success
The protection of the environment, when building and operating offshore wind farms, is a very serious issue in Germany. Basic research like the ESRa project is extremely important for a better understanding of the effects on the maritime environment and to initiate further measures. More research and development work is required in order to reliably meet the limit in the future. The most important findings of the ESRa project have already been presented in workshops to the manufacturers of the noise mitigation systems and the relevant approving authority.
Contact details to obtain further information on the practice
German Offshore Wind Energy Foundation