Offshore Wind Turbines

Ødegaard & Danneskiold-Samsøe has extensive experience in performing investigations of underwater noise and airborne noise.

Our services extend to measurements, evaluationand predictions of the noise from wind turbines in operation as well as under construction during piling and other noise generating operations during the project of establishing offshore wind turbines at sea.

• Ambient Noise
• Operational Noise
• Constructional Noise e.g. Pile Driving
• Propogation of Noiselishing offshore
  wind turbines at sea
• Measurement
• Assessment
• Verification
• Prediction

Offshore Wind Turbines

Introduction

When establishing offshore wind turbine parks, noise will be radiated into the marine environment during construction and during operation.

In order to evaluate the impact on marine life, the noise must be quantified.

Airborne noise can be predicted by use of standardized methods. The results can be shown on a noise map. Often national noise limits on the shore will have to be observed.

The estimation of the underwater noise is often based on measurement results from similar sites and wind turbines.

The annoyance and expected disturbance caused by the noise from offshore wind turbines to the marine environment are assessed by biologists. No national or international noise limits apply to the underwater noise.

Environmental Impact Assessment
As part of the environmental impact assessment of offshore wind turbines the noise radiated into the water must be documented. This is also required for the airborne noise reaching the shore.

ØDS is experienced in preparing the investigations and presenting the data for the further treatment in the process of the environmental impact assessment.

Often the biologists are using our results for assessment of impact on the marine mammals and fish.

Underwater Noise

Ambient Noise
The background noise in the water is called the ambient noise.

The underwater ambient noise level is dependent on the specific site. Often the ambient noise is dominated by noise from bubbles, waves, and ship traffic. Wind speed and sea bed conditions have a clear influence on the ambient noise level.

As part of our investigations, we perform measurements of the ambient noise, for comparison to the noise during operation of the wind turbines.

Noise during Operation
The underwater noise is measured during operation of the wind turbine. Hydrophones are used to pick up the noise signals.

• Noise Spectra is found
• Comparison to Ambient Noise

Propagation of Noise

Noise in the water propagates in a rather complex manner depending on sea depth, seabed characteristics, underground characteristics, etc.

Hence, precise prediction of the noise at large distances from the wind turbines, is a complex task.

ØDS has advanced prediction tools, however, the available input data describing the environment is often
very poor.

Rough estimates for the noise transmission can be given based on a simplified method.

Noise during Construction

The underwater noise is measured under the noise generating operations during construction. As an example the noise from pile driving can be measured.

Estimation of Underwater
Noise at New Sites For a specific site the noise transmission can be measured enabling a more accurate prediction of the noise propagation from the wind turbine in operation.

So with the measured noise transmission and the measured noise spectrum for a wind turbine, we can predict the noise transmitted into the surroundings.

Airborne Noise
Airborne noise can be predicted by use of standardised methods based on data provided by the wind turbine manufacturer. The results can be shown on a noise map, enabling comparison to the national noise limits that must be observed.

Such predictions can also be used for setting noise requirements to the wind turbines in order to ensure that noise limits can be observed.

• Noise Prediction
• Noise Mapping
• Environmental Noise Limits
• Noise requirements to the Wind Turbines

Recent Offshore Projects:

• Vindeby (DK)
• Gottland (SE)
• Middelgrunden (DK)
• Öland (SE)
• Hagesholm (DK)