Research on the Hydraulic Power Take-off Unit of a Hybrid Wave Energy Converter

As an economical and easy deployment wave energy converter (WEC), oscillating bodies WEC is gained more and more attention, and it has great significance of research, especially on supplying power for buoy observation and underwater sensor network. Hybrid wave energy converter, it also named combined mode wave energy converter, can capture the kinetic energy of multiple degrees of freedom of an oscillating body. This paper presents a design of hybrid wave energy converter equipped with a hydraulic power take-off (PTO) unit, and builds the mathematical model of the hydraulic PTO circuit. According to the result of the numerical simulation of the hydraulic circuit, a steady system pressure and an essentially constant motor speed can be obtained with the help of accumulators. More cylinders than one are applied in the hydraulic circuit, and the relative spatial positions of the cylinders will affect the stability of the system pressure. Additionally, the stability of hydraulic system pressure is influenced also by the size of the accumulator and the number of the cylinders.