In the present study a Froude scale model of an offshore wind turbine (OWT) was designed, based on the NREL 5MW-OC3-Hywind floating OWT concept minor modifications, and its dynamic response was experimentally tested under varying wave conditions. Spectral analyses of the measurements were carried out to investigate the dynamic behavior of the wind turbine including the calculation of the Response Amplitude Operator (RAO) for the critical motions of the OWT. Results demonstrate that the critical motions of the OWT under incident regular and irregular waves are surge and pitch. For regular waves the critical frequency of the OWT motions coincides with the frequency of the waves, while for irregular waves the critical frequency is the free oscillation (natural) frequency of the respective OWT motion.
In the last years, the increased demand for electricity, in combination with the commitments to significantly reduce CO2 emissions at the same time, makes the need of sustainable energy extremely imperative. Among the different sources for renewable energy production, blue energy is becoming more and more popular regarding energy production from wind, waves, and tidal potential.
The first to visualize large scale floating offshore wind turbines (OWTs) was Heronemus in 1972 (Tomasicchio et al., 2018). However, until nowadays the dynamic response of such structures, under the combined attack of wind and waves, remains a multiparametric and challenging topic that still attracts the interest of researchers worldwide.
Greece, with its exceptional wind potential and vast marine space, should pursue the installation and use of floating OWTs so that it will both meet its energy needs and effectively deal with potential shortfalls of wind turbines on land. The implementation of such systems should be planned according to the winds blowing in Greece as well as by the relatively small depth of its coastal seas. To date, mainly the high cost associated with such ventures has proved to be a stumbling block since the existing floating OWTs are extremely sizeable for the environmental conditions not only of Greece but in the Mediterranean in general. Therefore, designing a smaller and more economical floating OWT, adapted to the conditions in Greece, as well as the assessment of its hydrodynamic behavior has been deemed appropriate.