Conceptual Design and Dynamic Analysis of a Wind-Wave Energy Converter with a Mass-Adjustable Buoy

To reduce the levelized cost of energy (LCOE) for offshore wind turbines, a novel wind-wave energy converter (WWEC) with a mass-adjustable buoy is designed. To analyze the impact of buoy mass variations on the system, a coupled comprehensive numerical model is established to simulate the aerodynamics of the turbine and the hydrodynamics of the platform and buoy. It is found that the occurrence of the buoy out of water significantly reduces the output power. Adjusting the buoy's mass with suitable strategy can prevent the impact of slamming loads and improve the power output. The mass adjustment strategy is determined based on the output power of the wave energy converter under regular wave conditions. It is found that the mass adjustment strategy can significantly enhance the output power of combined system. The buoy does not move out of the water under the extreme conditions, which avoids the impact of slamming loads on system stability. Moreover, mass-adjustable buoys can reduce the risk of mooring line failure compare to a wind turbine without a buoy.