Mechanical Characteristics of Some Deepwater Floater Designs for Offshore Wind Turbines

Abstract

This paper presents an initial study of the mechanical characteristics of some deepwater floater designs for offshore wind turbines. Three different concepts (NREL TLP Dutch Tri-floater, and Japanese SPAR) are summarized, based on data from the available studies. A 5 MW Horizontal Axis Wind Turbine is used for the reference wind turbine and the steady wind load is calculated from the Blade Element Momentum method. These three concepts are simplified to 2D models and the static analyses of NREL TLP and Dutch Tri-floater are compared. The 2D NREL TLP model is selected for dynamic analysis, in which: (1) regular and irregular wave loads are calculated from the Morison equation for the relative motions in the time domain; (2) Airy's linear wave theory is applied to compute the wave kinematics; (3) The 10-minutes irregular waves are realized from the JONSWAP spectrum. For comparison, the same 2D NREL TLP floater model is also developed and implemented as a subsystem in the wind turbine simulation program, HAWC. The HAWC results are compared with those from our model.