Experimental wave termination in a 2D wave tunnel using a cycloidal wave energy converter

A lift based cycloidal wave energy converter (CycWEC) is investigated in a 1:300 scale two-dimensional wave flume experiment. This type of wave energy converter consists of a shaft with one or more hydrofoils attached eccentrically at a radius. The main shaft is aligned parallel to the wave crests and submerged at a fixed depth. The operation of the CycWEC both as a wave generator as well as a wave-to-shaft energy converter interacting with straight crested waves is demonstrated. The geometry of the converter is shown to be suitable for wave termination of straight crested harmonic and irregular waves. The impact of design parameters such as device size, submergence depth, and number of hydrofoils on the performance of the converter is shown. For optimal parameter choices, experimental results demonstrate energy extraction efficiencies of more than 95% of the incoming wave energy. This is achieved using feedback control to synchronize the rotation of the CycWEC to the incoming wave, and adjusting the blade pitch angle in proportion to the wave height. Due to the ability of the CycWEC to generate a single sided wave with few harmonic waves, little energy is lost to waves radiating in the up-wave and down-wave directions.

▸ We conduct 2D wave tunnel experiments with a cycloidal wave energy converter (CycWEC). ▸ The CycWEC is found to be able to terminate waves. ▸ Inviscid termination efficiency of more than 95% is achieved for harmonic deep ocean waves. ▸ Irregular Bretschneider waves can be terminated with better than 75% efficiency. ▸ The experimental findings agree well with earlier numerical results.