Reliability Based Design for Offshore Wind Turbine Foundations

 

reliabilitymapWind turbine siting is the selection of turbine locations within a wind farm. A wind farm should be arranged such that the lowest cost of energy is achieved. The cost of energy (COE) can be defined as the total cost of building, operating, and decommissioning the wind farm, divided by the total value of the electricity sold over its life. One of the largest drivers of cost in an offshore wind farm is the support structure, responsible for up to 34% of the overall project cost. Other significant cost sources, such as the turbine, are largely dependent on the current market and what is available to the developer. Support structure designs however, are unique to a project and are left to the developer to choose. Therefore, the layout of the wind farm must be designed with the support structure design in mind.

When the geotechnical and geophysical characteristics vary significantly at a particular site the designers of an offshore wind farm face additional complexities in the overall design process. A reliability based design method was created assist the engineer in support structure design and wind farm layout in the face of uncertain soil properties. This method deals with the natural spatial variability of soils by treating the soil properties as random variables, allowing for the reliability of different support structure configurations to be calculated. A case study was performed to show how the method can be implemented and what information it can provide to the designer of offshore wind farms.

The objective of this work was to develop a design methodology that uses the uncertainty associated with prediction of soil properties to access the reliability of a support structure design at various locations. This method will help the designer of an offshore wind farm select a particular support structure design for the farm and to find the locations that are best suited for the placement a wind turbine.