ESRa: Evaluation of Systems for Sound Reduction on an Offshore Test Pile
Offshore wind farms are usually built using rammed foundations. Typically, these offshore construction activities are mainly carried out below the water's surface. The sound pollution resulting from the ramming of conventional foundations is considered by the authorities to be a risk factor, especially for marine mammals.
The responsible authority (BSH) in the Exclusive Economic Zone requires in existing installation authorizations that state-of-the-art construction methods be utilized in order to minimize noise pollution. Discussions with marine biologists and approval authorities show that the use of practicable noise reduction methods during pile-ramming is an important goal when developing and producing foundations for future offshore wind power plants.
The selection, testing, efficacy and manageability of noise abatement methods is therefore crucial with regards to the continued growth of offshore wind energy in the North Sea and Baltic Sea.
The aim of the ESRa project was to identify, test and evaluate novel design and operation concepts for safe, practically manageable and cost-effective noise protection in the construction of offshore wind energy foundations.
In the research project, various new sound insulation systems were tested which are designed to reduce the propagation of the ramming sound during foundation installation for offshore wind turbines. For this purpose, a field test was carried out in August 2011 in the German Baltic Sea about three kilometres off Travemünde. A total of five new sound insulation systems were tested on a test pile in Neustadt Bay. Different noise protection concepts such as bubble curtains were used on the Brodtener pile at a water depth of about nine metres. All systems were used under identical environmental conditions in order to be able to compare noise reduction potential based on a uniform measurement concept. The Institute for Technical and Applied Physics (ITAP) in Oldenburg developed a corresponding measurement and evaluation concept for underwater sound measurements. Each of the sound reduction system prototypes stood up to the harsh conditions at sea and demonstrated a sound-absorbing effect. The damping effect, corrected for specific site influences, was up to nine decibels in the relevant area. This allowed a clear approximation to the sound emission limit of 160 decibels at a distance of 750 metres around the sound source. The ESRa project was the largest research project in the field of underwater sound reduction, with the measurement series providing a unique database of over 650 data sets.
Project partners and funding:
Under the umbrella of the German Offshore Wind Energy Foundation, the companies Bard Engineering, DONG Energy, EnBW Erneuerbare Energien, E.ON Climate Renewables, EWE Energie, RWE Innogy, Stadtwerke Münschen and Vattenfall participated in the ESRa project. The research project was also funded by the German Federal Ministry of the Environment.
01.03.2011 – 31.12.2011