Numerical investigation on a floating self-reacting resonant wave energy converter

Abstract

A self-reacting resonant C-shaped wave energy converter (SR-C-WEC) consisting of a pair of resonant sub-C-WECs connected by a rigid frame is proposed, which uses the two sub-C-WECs to provide mutual reaction force to solve the efficiency problem caused by floating WECs being hard to provide enough reaction force on WEC and uses the controllable resonant WEC to solve the efficiency problem caused by the temporal variability of waves. Resonant control and equivalent wave force control models are proposed to maximize the absorbed power. The effect of spacing between two sub-C-WECs, natural period, PTO damping and mooring stiffness to absorbed power is investigated. It is found that SR-C-WEC can achieve resonance at each wave condition and the power generation is maximum when the spacing is equal to half wavelength, which is comparable to the power generation when the frame is fixed. In a real sea condition, when the spacing is adjusted or not, the difference in average annual power is only 8.3%. Therefore, constant spacing can be used to simplify the structure and facilitate the application of SR-C-WEC. It is predicted that SR-C-WEC can reach 3638 effective power generation hours per year in real seas off China.