Effects of structural design parameters on the hydrodynamic interaction and response of the combined WindWEC concept

A very recently proposed combined wind and wave energy system is the WindWEC; a hybrid offshore energy system that consists of a floating wind turbine supported by a spar-type substructure (e.g. Hywind) and of the Wave Energy Converter (WEC) Wavestar. The evaluation and assessment of the hydrodynamic interaction effects between the different floating bodies are of high importance for the further successful development of the combined concept WindWEC. In this paper, the effects of structural design parameters on the hydrodynamic interaction between the different floating bodies, spar and buoys, are evaluated and examined. The examined structural design parameters are: (a) the distance of the WEC buoys with respect to the spar platform of the wind turbine (b) the dominant wave direction with respect to the arrangement of the different floating bodies and (c) the number of the WEC buoys that are used simultaneously. It is found that strong hydrodynamic interaction effects appear, depending on the relative distance between the spar and WEC. In particular, the relative motion in heave degree of freedom is significant for small distance between the spar and WEC, and, it becomes insignificant for larger distances. Also, the configuration of the WEC respect to the floating wind turbine affects the relative motions.