Parkwind N.V.’s Northwester 2 offshore wind farm is the seventh of eight wind farm projects in the Belgian waters of the North Sea. The Northwester 2 wind farm includes 23 turbines rated at 9.5 MW each, providing a total capacity of 219 MW.
With the project’s completion in spring 2020, Belgium reached 1,775 MW installed capacity and became the world’s fourth largest offshore wind energy producer.
JASCO Applied Sciences was commissioned by Parkwind to analyze the underwater sound emissions from the piling of the turbine foundations during installation of the wind farm and provide a comprehensive report for the Belgian Authorities to meet construction consent requirements.
Belgian authorities have implemented the Marine Strategy Framework Directive (MSFD) at a national scale and put in place a peak sound pressure level (Lp,pk) threshold of 185 dB re 1 µPa2 for underwater impulsive noise at 750 m from the source to mitigate effects on marine life. The focus species in this area of the North Sea is the harbour porpoise (Phocoena phocoena). To reduce the noise level propagating from hydraulic hammer pile driving, a double bubble curtain surrounded the piles during installation.
In the study JASCO assessed whether compliance was achieved and determined the influence of water currents and uneven bathymetry at the site on the performance of the bubble curtain. As noted in the wind farm’s EIA review document, the strong tidal currents of the Belgian North Sea can lessen the effectiveness of the curtain. This review of the efficacy of mitigation tools informs regulatory authorities on how to improve national guidelines to better meet MSFD requirements.
Furthermore, JASCO reviewed the measurement campaign and provided expert advice on possible improvements that may be applicable to other projects. This can benefit any situations where reliable monitoring of compliance with underwater sound thresholds during piling is essential to the execution of a project, which applies to regulatory jurisdictions that include Germany, The Netherlands, and Taiwan.
Example of a double bubble curtain sound mitigation system around an offshore pile installation. Photo by Hydrotechnik Lübeck.
