Attitude Control Method and Model Test for the Wave-Absorbing Buoy of the Sharp Eagle Wave Energy Converter Under All-Sea-State Operations

As a critical component of marine renewable energy, wave energy has long remained a focal point in research on development and use. The Sharp Eagle wave energy converter (hereafter, Sharp Eagle WEC) exhibits wave energy capture efficiency-related advantages, which are attributed to the unique structural configuration of its Sharp Eagle wave-absorbing buoy (hereafter, buoy). Operational observations reveal that under severe sea conditions, buoy motion amplitude increases significantly. Consequently, the downstream hydraulic and power generation systems experience excessive power loads, and the converter exceeds displacement limits, causing collisions with end-stop structures, which compromises operational safety. Research findings indicate that the attitude of the buoy directly governs its motion characteristics. We proposed a ballast-and-load-based attitude control method for the buoy. This approach provides safe and efficient operation across all sea conditions. Via scaled model tests, converter operational data covering various ballast configurations were compared and analyzed, focusing on the effects of ballast on the capture width ratio (hereafter, CWR) and piston displacement range of energy conversion hydraulic cylinders. Herein, the feasibility of adjusting capture efficiency and motion displacement by controlling the buoy attitude is validated, providing a technical framework for efficient and safe operation of the WEC under all sea conditions.