Experimental and numerical study of dynamic responses of a new combined TLP type floating wind turbine and a wave energy converter under operational conditions

This paper deals with a novel concept by combining a tension leg platform (TLP) type floating wind turbine and a heave-type wave energy converter, that is referred as the ‘TWWC’ (TLP-WT-WEC- Combination) system herein. Dynamic responses of the TWWC system under operational seas cases (in South China Sea) have been investigated by using both time-domain numerical simulation and scale model tests (1:50). For the numerical model, hydrodynamic loads of the TLP and the WEC are calculated by the AQWA code, which is available for modeling multi-body systems including both mechanical and hydrodynamic couplings between the TLP and the WEC. The aerodynamic loads of the wind turbine are calculated based on the NREL 5 MW wind turbine. The scale model tests have been done in Harbin Institute of Technology’s wind tunnel & wave flume joint laboratory. The power-take-off (PTO) system of the WEC device is simulated by two nonlinear air-dampers, and aerodynamic loads of the wind turbine are simulated by a scaled rotating wind turbine model with equivalent mean thrust effect. Main dynamic characteristics of the TWWC system under operational sea cases have been clarified. Numerical and experimental results are presented and compared. Good agreements are achieved, although the numerical model tends to overestimate dynamic responses of the TWWC system due to ignoring the viscous damping effect in the scale test model. The validated numerical model of the TWWC system will be useful for future optimal design of the WEC PTO system.