Sound Propagation Modelling for Offshore Wind Farms technical evaluation
This study looked at predicting noise impacts using modelling – both over water and at land receptors – to inform any future rules and requirements related to noise.
On this page Skip this page navigation
Valcoustics Canada Ltd. was retained by the Ontario Ministry of the Environment and Climate Change (MOECC) to complete a literature review and consult with experts in other jurisdictions to identify and compare the models that are available to analyze and predict the propagation of sound over water specifically from wind turbines located offshore.
This study was prepared to assist the MOECC in determining an appropriate sound propagation model for offshore wind farms to be used in Ontario. The sound propagation models discussed in this study are only applicable to the sound frequencies within the human audible range of frequencies, with the exception of the Parabolic Equation method. Infrasound and underwater sound propagation modelling were not part of the scope of work of this study. Purchasing, training, and use of commercial modelling software, as well as providing recommendations on the results of the study were also beyond the scope of this study.
Wind power is a renewable energy source that has the potential to contribute significantly to meeting energy needs around the world. As the sites on land with good wind potential become less available, an alternative approach is to locate wind farms offshore. Offshore wind resources may be stronger and more reliable than wind over land. However, no offshore wind energy project has been constructed in Ontario to-date. The European Union leads in developing offshore wind turbine technology and offshore wind farm construction.
Propagation of sound from offshore wind turbines over water is different from propagation from land-based wind turbines. Prediction of noise from offshore wind turbines generally involves propagation of noise over large distances meaning small inaccuracies in the prediction models can become significant. Additionally, meteorological and atmospheric conditions that occur over water can affect sound propagation. The sound prediction models commonly used for land-based wind turbines may not be suitable for offshore wind farms. Consequently, the setback distances appropriate for a land-based wind farm may not be suitable for an offshore wind farm.
Sound propagation model identification and international offshore model application
This report identifies various sound propagation models to predict receptor sound levels that were approved for use by regulators in different countries as well as analytical/numerical models and describes the applications of these models in international offshore wind farm projects.
A jurisdictional review was completed to determine the various regulations, guidelines, codes of practices and best practices for assessment and control of environmental noise applicable to wind turbines. The review determined that there are currently no noise guidelines/regulations pertaining specifically to offshore wind turbine noise and that offshore wind turbines are bound by the same noise criteria as onshore wind turbines.
Some jurisdictions indicate a particular acoustical modelling method (e.g. international or national standard or other technical procedure) should be used for wind farm noise assessment. However, many do not specify or require a particular modelling method. Of those that do indicate a specific acoustical model/analysis method, only a small subset requires modifications to the methods to account for propagation of sound over water, such as for offshore wind farms. The strictest noise requirements are found in Sweden, Germany, Finland, New Zealand, the United Kingdom and parts of Australia.
Offshore model application in Ontario
The report describes the practical considerations of the acoustical models that are presented in the report and that may be suitable for use in Ontario to predict sound levels (noise) from offshore wind turbines at land-based receptors. Each model is then summarized to compare advantages and disadvantages as well as the various parameters which each model takes into consideration.
The most applicable sound propagation models are those that are implemented in commercially available software such as CadnaA, windPRO, or SoundPLAN and those that are based on ISO 9613-2 which Ontario has already adopted to model sound propagation from land-based wind farms. The CONCAWE model has previously been used in Ontario and other provinces for industrial stationary sources but may not be relevant to offshore wind farms. The NORD2000 model has greater accuracy but the data required may not be readily available and if it is applied it may need to be applied to onshore projects to ensure consistency.