Dynamics and power absorption of a self-react wave energy converter with mechanical power takeoff system

Abstract

A self-react wave energy converter which consists of a floating buoy and a submerged body is studied in this paper. The energy is extracted through the relative motion of the floating buoy and submerged body. Two kinds of power takeoff(PTO) system, which is the technique approaches to extract energy from the ocean, are considered for the proposed wave energy converter. One is a ball screw system with mechanical motion rectifier gearbox (which is called MMR system) and another one is solely a ball screw system (which is called non-MMR system as a comparison). The design of the proposed wave energy converter is presented and the model for both power takeoff systems are established based on their mechanisms. A time domain method is adopted to investigate the dynamics and power absorption for the proposed wave energy converter. The effect of equivalent mass on the optimal power and corresponding optimal power takeoff damping are studied both in regular and irregular waves. It is found that the equivalent mass plays different roles in the MMR system and non-MMR system. Due to the disengagement in MMR system, the equivalent mass helps to increase the power absorption at small wave 1periods, both in regular waves and irregular waves. The uncertainty of the drag coefficient on the power absorption of MMR system and non-MMR system is also investigated.