Experimental study of a floating two-body wave energy converter

A novel floating two-body wave energy converter (WEC) is tested in regular waves. The WEC consists of a streamlined conical outer buoy that surrounds an elongated inner buoy, with a hydraulic power take-off (PTO) system and an optimized mooring system. Free decay tests quantify the natural frequency characteristics of two-buoy system. A parameter study characterizes the multi-degree-of-freedom coupled motion response of the system dynamics in regular waves. It is found that the two-body system with two resonant frequencies broadens the motion frequency band and possesses stability and survivability attributes that enhance energy capture performance. By quantifying the peak energy, the influence of key parameters on energy absorption is revealed, and the two-body system optimized through systematic parameter selection. Nonlinear effects of fluid viscosity and mooring chain stiffness on energy absorption are analyzed by considering change in wave height. Estimates are made of the optimal energy acquisition interval of the device and its optimal sea area for delivery. By determining the optimal mass ratio for maximum WEC power absorption insight is also provided into the likely optimal energy capture in the deep sea off the coast of China. This paper offers information on floating two-body WEC systems, including guidance on optimization of PTO control strategy, that should be useful to WEC device analysts and developers worldwide.