Comparison of Spar and Semisubmersible Floater Concepts of Offshore Wind Turbines Using Long Term Analysis

Abstract

The longterm probability distributions of a spartype and a semisubmersibletype offshore floating wind turbine response are calculated for surge, heave, and pitch motions along with the sidetoside, fore–aft, and yaw tower base bending moments. The transfer functions for surge, heave, and pitch motions for both spartype and semisubmersibletype floaters are obtained using the fast code and the results are also compared with the results obtained in an experimental study. The longterm predictions of the most probable maximum values of motion amplitudes are used for design purposes, so as to guarantee the safety of the floating wind turbines against overturning in high waves and wind speed. The longterm distribution is carried out using North Atlantic wave data and the shortterm floating wind turbine responses are represented using Rayleigh distributions. The transfer functions are used in the procedure to calculate the variances of the shortterm responses. The results obtained for both spartype and semisubmersibletype offshore floating wind turbine are compared, and the study will be helpful in the assessments of the longterm availability and economic performance of the spartype and semisubmersibletype offshore floating wind turbine.