Sensitivity Analysis of O&M Costs for Offshore Wind Farms
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- Institutt for fysikk 
The offshore wind farm industry is challenged by high costs related to operation and maintenance (O&M), and a study on how to significantly reduce these costs is essential to make this industry competitive with other energy industries. For this purpose, it is important to understand which factors related to operation and maintenance are influencing the O&M costs. This study is concerned about sensitivity analysis, a common tool used to identify influential input parameters for computer models.Three Sensitivity analysis methods were implemented and integrated with the computer model NOWIcob that simulates the operation and maintenance of an offshore wind farm. Two of the methods were local, and studied effects in the cost by changing one variable at the time, keeping all other parameters constant at their reference value. The third had a global perspective where all parameter values were selected randomly from a specified range around each parameters reference value. The capabilities of these methods were illustrated by applying them on a case with data for a hypothetical offshore wind farm.Among the 15 single parameters considered, the local analysis identified a group of five single parameters (three failure rates, the variable cost for the jack-up vessel and the wave access limit for the mother ship) as the most influential on the total O&M cost on this wind farm. The global method confirmed that results from the local method are also valid for a wider range of the parameter values. The results provide suggestions about how to reduce the cost, and the installation of a more robust access system on the mother ship seems to be a possible way to significantly reduce the total O&M cost for the wind farm under consideration.