Hydro Sound

Research and testing of a “Layered Bubble Curtain (LBC)” at the offshore test site alpha ventus

Background

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 testfield alpha ventus. The little bubble curtain was mounted directly at the monopile.

Thematic Issues

  • Conceptional design and development of the little bubble curtain,
  • Testing and subsequent evaluation regarding the capability of the little bubble curtain under offshore conditions with respect to the major building process.
  • Determination of the influence of drift velocity and direction on the sound reduction of the bubble curtain in progress.
  • Investigation of the influence of air pressure and volume flow on the sound reduction in the surrounding area.

Associated partners

  • Institut für Statik und Dynamik (ISD), Uni Hannover
  • Menck GmbH, Kaltenkirchen

Other Partners

  • Institut für technische und angewandte Physik GmbH (itap), Oldenburg
  • UL International GmbH (DEWI), Wilhelmshaven
  • Hydrotechnik Lübeck GmbH, Lübeck
  • Prokon Nord Energiesysteme GmbH, Leer
  • Prokon Nord Offshore Installations GmbH, Leer
  • Karl Wrede Stahl- und Maschinenbau GmbH, Eddelak
  • Bode und Wrede GmbH, Itzehoe