The Hywind turbine represents the world’s first full-scale floating wind turbine. Statoil’s concept for the Hywind turbine was to create a floating wind turbine that can be operated in waters in excess of 100 m depth that is based on conventional technology and has a simple substructure design. In 2009 a full-scale demonstration turbine (Hywind I) was installed 10 km off the Norwegian west-coast. This 2.3 MW turbine, which has been tested and operated successfully for the last four years, has been verified as a technically viable concept. In order to continue towards achieving the long term vision for developing floating wind on a commercial scale, Statoil is planning to develop a number of Pilot Parks which will be used to demonstrate technological improvements, operation of multiple units, and cost reductions in a park configuration. Hywind Scotland is the first of the pilot parks to be taken forward for development.
The Hywind Scotland pilot park will consist of up to five turbines with a maximum installed capacity of 30 MW. The turbines will be located between 720 and 1,500 m apart and will be attached to the seabed by a three-point mooring spread. Depending on seabed conditions, the moorings will be secured with the most suitable type of anchor. The anchor types currently under consideration include torpedo anchors, suction anchors or weight anchors. The mooring lines are likely to be composed of chains with a diameter extending out from the Hywind turbines to approximately 800 to 1,000 m.
Noise is readily transmitted underwater and there is potential for sound emissions from construction and operation of Hywind to affect marine mammals and fish. By using a floating structure, the installation noise is much reduced by removing the need for driven piles. However, there are likely to be noise impacts due to operation of the turbines as well as other construction activities, such as cable installation and use of vessels. At long ranges the introduction of additional noise could potentially cause short-term behavioural changes, for example to the ability of cetaceans to communicate and to determine the presence of predators, food, underwater features and obstructions. At close ranges and with high noise source levels, permanent or temporary hearing damage might occur, while at very close range, gross physical trauma is possible.
This report provides a high level overview of the potential impacts due to underwater noise from Hywind on the surrounding environment. In particular, this report reviews the underwater noise measurements and analysis previously undertaken by Statoil on the Hywind I demonstrator installed offshore Norway, to assess operational noise from the turbines. The report also makes recommendations for the types of impacts identified should be addressed in the EIA in terms of marine noise.