NUMERICAL VERIFICATION OF FLOATING OFFSHORE WIND TURBINES WITH EXTERNAL BUOYS EMPLOYING INERTERS FOR VIBRATION SUPPRESSION AND WAVE ENERGY CONVERSION

Abstract

In recent years, ocean energy such as winds and waves has been attracting attention as promising renewable energy sources. Especially, offshore wind turbines (OWTs) show great potential, and various kinds of OWTs have been proposed so far. Among these, floating OWTs are considered more suitable for Japan due to the deep waters in the nearshore area. However, floating type is vulnerable to wind- and wave-induced vibration compared to bottom-fixed OWTs. On the other hand, a novel wave energy converter (WEC) with an inerter mechanism was proposed. This study is inspired by this WEC and proposes floating OWTs with externally installed buoys employing inerters for vibration suppression and wave energy conversion. A simple analytical model including the effects of additional mass, radiation damping, and wave excitation force on the floating body is developed for the heave direction. Then, appropriate design parameters are examined, and active control scheme is also applied to improve the performance further. The results obtained from WEC-Sim (Wave Energy Converter SIMulator) show that the proposed device works to control the floating OWT and generate wave energy effectively.