Analysis of a Fixed Yaw Weathervane Offshore Wind Turbine Having Single Point Mooring

Abstract In the recent years, offshore wind energy has gained much importance owing to its viability and technical advances in the performance predictions. The thirst for steady energy supply from wind has pushed the wind turbine industry to offshore waters requiring floaters as the only possible and feasible solution. The floater along with wind turbine sets up the basis for any offshore floating wind turbines. The costs and the complexity involved in yaw mechanism are very high. To tackle this issue, a weathervane wind turbine system is proposed to eliminate the use of turbine yaw mechanism. In the concept of weathervane wind turbines, the floating wind turbine is connected to a single point mooring (SPM) about which it weathervanes. To better understand and to make practical decisions in real scenarios, performance analysis is carried out for a weathervane wind turbine system of a semisubmersible type. For present study, NREL 1.5 MW wind turbine is chosen as it is readily available and is widely preferred for preliminary studies. The numerical simulations are carried out using effective coupling of FAST code with OrcaFlex. The responses of the floating wind turbine systems not only depend on the floater but also on the coupled motions of wind turbine with SPM subjected to turbulence wind loadings. This non-linear coupling is analyzed in the time domain combining the effects of floater hydrodynamics, wind turbine system and mooring system. Numerical results along with discussions are presented. This preliminary global performance analysis gives a vision on its capability to better suit offshore, meeting the global standards.