DENMARK:Tests have been carried out in Åarhus, Denmark about options for reducing noise from offshore turbine foundation piling. Such noise can cause harm to sea mammals, such as porpoise, dolphins and seals
The tests using cofferdams were carried out off of the town of Hojbjerg, by a Denmark-based marine consultancy, Advanced Offshore Solutions. The tests were conduction at the end of 2011 at the request of the German Federal Maritime and Hydrographic Agency (BSH), with the aim of gauging the effectiveness of the noise reduction system, which can work at water depths of up to 45 metres, before deployment later this year.
"The concept is based on the physical principle that if you decouple the pile from the water, the noise will be transferred into the air, which of course is compressible," explained Kurt Thomsen, chief executive of Advanced Offshore.
"When the cofferdam is open to the atmosphere, the air will disappear upwards and therefore transport most of the noise away from the water column. Our patent is therefore an industrialised version of the cofferdam, which works in a fast and flexible way in different water depths, securing noise mitigation and providing passive noise reduction for pile driving offshore," said Thomsen.
Speaking at last week’s Coastal Futures event in London, professor Han Lindeboom of Dutch research institute, IMARES, warned against building offshore wind farms in marine protection areas because of the noise impacts on marine species, specifically noise from hammering monopiles. Lindeboom said there was clear evidence that mammals such as harbour porpoises had moved away from wind farm sites during construction. "Floating turbines are definitely better for wildlife in terms of construction disruption," he said.
The Advanced Offshore cofferdam system has now been declared ready for use by the BSH and will be used for the first time in two offshore projects in the German North Sea in July this year.