Sensitivity analysis of offshore wind turbine tower caused by the external force

Generally, faster wind speeds are observed in coastal areas than in inland areas. Therefore, for the development of offshore wind energy, more electricity is expected to be generated using wind turbines. This also solves environmental obstacles such as the selection and acquisition of land for a site and the need to protect surrounding sites from noise problems. In this paper, a numerical analysis on the external forces that affects a wind turbine tower is performed, when the wind turbine is installed in a coastal area. To calculate the extreme wind and wave forces, the maximum wind speed is assumed to be 55 m/s, which is observed 10 minutes as the mean maximum wind speed of typhoon Maemi in 2003. During the calculation procedure, the wind force is calculated according to the Korea Building Code 2009. The significant wave height and period are estimated by using the Sverdrup-Munk-Bretschneider (SMB) method. The result data obtained using the SMB method are applied to Morison's equation to compute the wave force. The blade of the wind turbine is designed based on the Blade Element Momentum Theory, and the thrust force of the blade is computed. The diameters of the wind turbine tower are assumed to be 3 m, 4.5 m, and 6 m. The results of this numerical analysis show that wave force acting on the wind turbine tower is increased according to the diameter of the tower and the wind speed.