Hywind Tampen Floating Offshore Wind Farm: Sound Source Characterisation of Operational Floating Turbines
February 2025 - United Kingdom
Client: Equinor Energy AS
JASCO Applied Sciences undertook a sound source characterisation study of the Hywind Tampen floating offshore wind farm, approximately 140 km northwest of Bergen, Norway. Four recording instruments were deployed from the DOF Skandi Iceman to the seabed by remotely operated vehicle in February 2024 at various positions both within and around the wind farm site. Two instruments were set up in a single-hydrophone omnidirectional configuration and two with arrays of four hydrophones to provide directional noise discrimination. Three of the four recorders (one directional system and the two omnidirectional systems) were retrieved in June 2024. The remaining directional recording system remains in situ on a 12-month recording schedule and is expected to be retrieved in early 2025. Recording was conducted at a 64 kHz sample rate with 24-bit resolution, and the total volume of data collected from the first three stations was 7.3 TB. Analysis of the recorded data was undertaken to determine the characteristics of the sound produced by the turbines at Hywind Tampen and compare this to similar sound source characterisation study of the Hywind Scotland floating system. The dominant sound emissions from the Hywind Tampen turbines are narrowband tones, principally below 200 Hz, with two notable tones at around 25 and 75 Hz being the primary contributors to the recorded sound spectra. The sources of these tones are directly related to the rotational rate of the rotor and the number of magnetic pole pairs in the generator, one directly and the other by a factor of three. Consequently, the actual frequencies generated by the rotating components of each turbine depend on the rotor RPM at any given time, where the strong tones at around 25 and 75 Hz are the frequency limits of the rotor related tones associated with the system maximum RPM. Other tones which were variously stable and unstable, continuous and intermittent were found to contribute to the spectra to a lesser extent.