Page 14: of Maritime Reporter Magazine (February 2016)

EYE ON DESIGN

Response of a Semisubmersible

Floating Turbine Foundation

Floating foundations for wind turbines present some technical advantages, which

SEBASTIEN GUEYDON is encouraging more and more industry players to develop new ? oaters.

irstly, they can be deployed in deep seas, independent of the soil conditions. Sec-

Fondly, the installation and heavy mainte- nance can be done in sheltered areas, so that the whole OFWT can be towed directly to the wind farm’s location by conventional tugs. However, ? oating foundations also bring new constraints on the wind turbine due to their motions in waves and wind. The combined use of model tests and simulations gives a better understanding of all the mechanisms at play.

Ideally, OFWTs are designed such that their natural periods are out of reach of the most ener- getic waves. Because waves and ? oater responses are not purely linear, it is useful to examine situ- ations when higher order wave excitations are acting on the ? oater. Therefore, a study on the ef- fects of second order wave loads on the ? oater’s responses was carried out for a semisubmersible.

Second-order wave excitation resonant re- sponse peaks were identi? ed in surge, heave and pitch from the analysis of measurements in waves. When the semisubmersible is exposed to wave only, the second-order response in pitch becomes the largest cause of inertial loading on the turbine. In wind and waves, the motions of the wind turbine are in? uenced by the wind loads on the rotor. This effect is particularly noticeable at the surge and pitch eigen frequencies, when it can potentially damp out the pitch response to second-order wave loads and bene? cially reduce the inertial loads. Interaction between the loads on the rotor, the wind turbine controller and the motions of the ? oater are being thoroughly ex- amined in the LIONS HAT Joint Industry Project set-up by MARIN.

The Author

Sebastien Gueydon is Researcher for the Mari- time Simulation & Software group of MARIN, the

Maritime Research Institute Netherlands. e: [email protected] 14 Maritime Reporter & Engineering News • FEBRUARY 2016

MR #2 (10-17).indd 14 2/3/2016 10:15:30 AM