Laboratory experiments on the power capture of pitching vertical cylinders in waves

This paper presents results from an experimental study on the power capture of bottom-pivoted pitching point absorbers in intermediate water depth subjected to regular and irregular waves. The present research investigates the respective influence of parameters such as damping and inertia modification (ballasting) on the performance of bottom-pivoted pitching wave energy converters in simulated scaled sea states. Results indicate that this type of wave energy device performs best in moderate sea states, although the net power output would be greater in larger sea states. The pitch displacement angle, relative to vertical, is typically <±15∘<±15∘ under normal operation. The two most influential parameters, damping and ballasting, have a dramatic influence on the performance of the device. Moreover, it is shown that these parameters can be adjusted in response to the wave conditions to optimise power capture. From the results of the tests in unidirectional irregular waves, a full scale cylinder-shaped prototype of 6 m diameter located in 25 m water depth could absorb approximately 130 kW (average) in nominal winter conditions and approximately 40 kW (average) in summer sea states.