The Development of an Expert System for the determination of Availability and O&M costs for Offshore Wind Farms

With the availability of the wind turbine at a land based location as a starting point the expert system calculates the offshore availability as a function of distance to shore, average (offshore) wind speed and of course amount of money to be spend for maintenance. The average wind speed is linked to a storm database, from which the accessibility of the offshore wind farm is estimated. This accessibility and the amount of money available determines the actual offshore availability and with it the contribution of O&M expenditure to the costs of a kWh. Assuming a land based availability of 97% it is found that the actual offshore availability will become some 76% for a location 15 km offshore assuming a moderate 25% inaccessibility factor due to high winds and/or waves. An increase to 5 Million ECU's per year on top of a fixed yearly O&M budget of 3.8 MECU (for a wind farm consisting of 100 wind turbines) does not significantly increase the availability (only to about some 80%). Increase of the land based availability to a rather ambitious 99% however results into 96% availability on that site at a moderate expense of 2.2 MECU (on top of the fixed budget). The newly developed expert system is a fast and easy to handle tool for the assessment of offshore wind farm availability and the related O&M costs. The expert system can be used to balance the investment cost for increased reliability against exploitation costs for O&M in such a way that the most economical solution is established. Furthermore an estimate is obtained of the demanded O&M expenditure to achieve the required availability level