Heerema, IQIP Produce 24 dB Less Noise During Monopile Installation at EnBW’s He Dreiht Offshore Wind Farm

July 4, 2024, by Adrijana Buljan

Heerema Marine Contractors has demonstrated a noise reduction of 24 decibels (dB) during installation work at EnBW’s He Deiht offshore wind farm in Germany, where the offshore construction specialist employed a noise mitigation spread with equipment supplied by IQIP.

Heerema Marine Contractors' vessel Thialf at EnBW He Dreiht offshore wind farm equipped with IQIP noise reduction tools — Photo source: Heerema Marine Contractors via LinkedIn

The Netherlands-based Heerema Marine Contractors is installing the XL monopiles and transition pieces at the He Dreiht offshore wind farm under a contract signed with EnBW in April 2022. The company kicked off the work in May this year with the installation of the first monopile using its semi-submersible crane vessel (SSVC), Thialf.

The 960 MW He Dreiht offshore wind farm is located in the German North Sea, approximately 85 kilometres northwest of Borkum and about 110 kilometres west of Helgoland.

In the project design, EnBW has committed to the development of the latest generation noise mitigation system (NMS) in response to the regulations that are applicable in the German Bight which limit underwater noise to 160 dB at 750 metres from the source.

The system EnBW added to the project plan’s installation works is an upscaling of previous systems complemented with the truss frame template structure, enabling its deployment with floating installation vessels.

Heerema accelerated and completed its development by additional research and engineering efforts, the company says.

For the monopile installation work, Heerema has deployed the noise mitigation system T-NMS-10000, constructed in collaboration with IQIP, in combination with a double big bubble curtain and IQIP’s PULSE system. Testing and real-world applications have demonstrated that the combined noise mitigation equipment reduces underwater noise by up to 24 dB, according to the companies.

The T-NMS-10000 is a large subsea noise barrier for monopiles that contains internal noise emissions. Its steel structure comprises an inner tube of approximately 12 metres in diameter that is suitable for a 10-metre-diameter monopile and an outer tube of approx. 13 metres in diameter, separated by rubber blocks.

Air compressors expel the water column between the tubes, creating an air barrier across the entire water depth. The T-NMS-10000 alone contributes to reducing noise up to 15 dB in the noise mitigation spread which, all equipment combined, brings this to 24 dB.

The He Dreiht offshore wind farm is scheduled to go into operation at the end of 2025.

Once operational in 2025, the 64 Vestas V236-15.0 MW wind turbines at He Dreiht will generate green electricity for the equivalent of 1.1 million German households.

EnBW is the majority owner (50.1 per cent) and the developer of the project. A consortium consisting of Allianz Capital Partners on behalf of Allianz insurance companies, AIP and Norges Bank, holds the remaining 49.9 per cent of the wind farm.