The measurement results of hydro sound levels in connection with piling activities for the installation of offshore wind energy converters in the Baltic Sea and in the North Sea show that the recommended values defined by the German Umweltbundesamt (UBA) are seriously exceeded. In this regard it is clearly necessary to provide effective sound reduction techniques while piling. However, those activities have to be cost-effective and should be used without disturbing the building project.
During the installation of the research platform FINO3 in July 2008 a closed bubble curtain surrounding the monopile at a higher distance was used to achieve sound reduction. The operation of this bubble curtain succeeded and led to significant level decreases, although the recommended values mentioned above couldn’t be reached. Within the framework of the workshops arranged by the Stiftung Offshore-Windenergie it was decided to test a little bubble curtain close to the foundation. The conceptional design and construction of the little bubble curtain was developed by Menck GmbH in cooperation with Hydrotechnik Lübeck GmbH.
By the end of May 2009 the required hydro sound measurements were carried out during the installation of a wind energy converter of type AD 5-116 in the offshore test field Alpha Ventus. The little bubble curtain was mounted directly at the monopile.