Floating Wind Turbine Challenge
Author S├ębastien Gueydon, Samuel Harding
Title Floating Wind Turbine Challenge
Conference/Journal INORE
Month June
Year 2011

As wind turbines move into deeper water, floating structures might be preferred to fixed foundations to reduce both their production cost and their installation cost. A floating foundation has the advantage that the turbine can be mounted on the floater in a sheltered area before the whole structure is towed to the wind farm. In this way the installation can be limited to the towing of the floating turbine and the mooring of the floater, which is quicker than for a fixed offshore wind turbine. This operation only requires tugs and anchor handling vessels which are more widely available and cost less than crane vessels needed for the installation of bottom fixed offshore wind turbines. Thus a floating foundation cuts installation time and cost in comparison to a bottom fixed foundation. Large maintenance refit actions can also be carried out in the harbour for a smaller cost than at sea in the case of fixed wind turbines. However designing an offshore floating wind turbine (OFWT) brings new mechanical constraints to the nacelle and the rotor. The motions of the floater affect the performance of the wind turbine and vice-versa. In an economically viable concept, the mass of the floater would most likely not be much bigger than the mass of the wind turbine. Therefore the rotating rotor and the conversion of kinetic energy to electricity will also be felt by the floater. As wind turbines get taller to catch higher wind flows, even small pitch or roll rotations already result in large motions at the location of the nacelle. This is also true for the velocities and accelerations high up in the turbine causing large loading on the most sensitive components of the wind turbine. Both the weight aspects and the motion response aspects were addressed in the floating wind turbine challenge. Indeed the request to the participants was to design and build a floater with the lightest weight as possible for which the horizontal acceleration at the nacelle will remain small in survival condition.

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