Start of preparations for Trianel’s offshore wind farm

Sound protection for marine animals


Preparations for the construction of Trianel’s Borkum West II wind farm are in full swing. Currently the main focus of the project developers is on environmental protection. Trianel Windkraftwerk Borkum GmbH & Co. KG wants to provide comprehensive protection to marine mammals, in particular porpoises, against construction noise underwater.

“Our offshore project is the first commercial wind farm worldwide at which all wind turbines will be equipped with underwater sound protection walls”, reports Klaus Horstick, Managing Director of the Trianel wind farm. To achieve this, Trianel uses the so-called large bubble wall. This has been scheduled for testing during the summer when construction work starts at the Borkum West II wind farm, to ensure that it is suitable for serial operation.

Sound protection becomes necessary because of the anchoring of the wind turbine foundations to the ocean seabed. This process involves steel piles being rammed in to the ground to a depth of over 30 metres. Each ramming stroke causes a sound wave which, underwater, can be heard as far as several kilometres away. In order to give the porpoises, which live in these waters, the opportunity to move away from the construction site, the intensity of ramming will be gradually increased. 

“Porpoises navigate by echolocation, i.e. by using their hearing. Just as with people, too much noise can cause hearing damage to cetaceans too. If this happens, the animal can no longer orientate itself. We want to avoid that”, comments Horstick on the issue.

The function of these large bubble walls is based on a simple phenomenon based on physics. The sound produced during the ramming work is dispersed and attenuated by the rising bubbles. A nozzle hose about 400 metres long and filled with compressed air is placed underwater around the pile at a distance of 60 to 70 metres. The nozzles are of different sizes, so that the bubbles vary in size. The rising bubbles form the sound protection wall. In collaboration with Hydrotechnik Lübeck GmbH, BioConsult GmbH & Co. KG in Husum and ITAB GmbH in Oldenburg, this sound protection technology will be tried and tested on a large scale during the construction of the Trianel wind farm. 

“We hope that our sound protection concept will substantially reduce the impact on marine life”, explains Horstick. “We will discuss our experience with the bubble wall with the relevant authorities as well as generally so that it will be available for other wind farm developers so as to be able to provide the best possible protection for porpoises in the future.” 

The decision to build Trianel’s Borkum West II wind farm was made in December 2010. In addition to Trianel GmbH, 33 municipal and regional utility companies from Germany, Austria, Holland and Switzerland are involved in the wind farm. The wind farm is being constructed 45 km north of the coast of Borkum, in water with a depth of 30 metres. During the first construction phase starting from August 2011, forty wind turbines with an output of 5 megawatts each will be installed. Commissioning of the wind farm has been scheduled for the end of 2012/beginning of 2013.

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