Decision Support for Offshore Wind Turbine Installation: Statistical estimation of Probabilities of Failed Offshore Operations

The costs of operation & maintenance (O&M), assembly, transport and installation of offshore wind turbines (OWT) contribute significantly to the total cost of offshore wind farm. The O&M access and installation operations are mostly carried out by specific ships, that have to be hired for the operational phase and for duration of the installation process, respectively. The duration, and therefore the ship hiring costs, is among others driven by waiting time for weather windows for weathersensitive operations. Today the state of the art decision making criteria for weather-sensitive operations are the significant wave height and the average wind velocity at reference height, however the actual limitations are physical and related to the response of equipment that is used e.g. crane wire tension, air gap between rotor assembly and nacelle, etc. Transition from weather windows to physical response criteria in decision making would improve the cost predictions and, furthermore, potentially reduce the cost of energy. Computer tools can be applied to simulate motions of floating vessels (barges and cranes) representing the access and installation of offshore wind turbines. Since weather predictions have a certain degree of uncertainty the response of the installation equipment is expected to be uncertain also. Assessment and appropriate incorporation of response uncertainties into the decision making processes is essential in order to make accurate decisions.