A Vertical Axis Rotor for Wave Energy Conversion

The present work augments vertical-axis unidirectional wave energy converter (WEC) designs with a new approach. The enabling technique is the hydrodynamic design of a special rotor, which consists of a series of uniquely shaped blades in a certain formation. Specifically, individual blades are realized by revolving a two-dimensional symmetric hydrofoil about its chord line. Then the blades are arranged around a vertical shaft in a desired formation to form the rotor. When driven by an approaching flow through interaction, the rotor naturally rotates about the vertical shaft in a predefined direction. The approaching flow could be from any spatial direction, and could have changing speed and direction in any fashion, but the unidirectional behavior of the rotor never changes. Such a behavior guarantees a unidirectional performance of the rotor in waves, where the water flow is omnidirectional and constantly evolving. In validating the proof of concept and characterizing the rotor’s unidirectional performance, experiments were carried out under various flow conditions. Specifically, three types of flows were employed: horizontally oscillating flow, vertically oscillating flow, and orbital flow along a circular path in a vertical plane. The three flows were actually created by translating the rotor in still water, with the first two to characterize the rotor’s responsiveness to the flow direction and the third one to simulate rotor interaction with deep waves. For each flow type, different rotor configurations/blade formations were examined under various testing parameters. For all the cases, the rotor shaft was kept vertically all the time. The experimental results are discussed in details in the paper.