Opening the air‐chamber of an oscillating water column spar buoy wave energy converter to avoid parametric resonance

The oscillating-water-column (OWC) spar-buoy is a type of wave energy converter that may exhibit undesirable large roll and pitch amplitudes caused by dynamic instability induced parametric resonance. occurrence this phenomenon not only reduces the power extraction but significantly increases structural loads on buoy, turbine rotor mooring system. paper compares resonance behaviour two configurations an OWC using experimental data obtained in flume at scale 1:100. investigated were: (1) closed (2) fully open-air chamber. tests covered wide range regular irregular waves, as well free decay experiments. Results showed opening air chamber coupling between buoy within, thus shifting damped natural heave frequency system comparison with configuration. This effect changes characteristics due to roll/pitch modes. Moreover, for specific frequencies, observed when do occur while open. These results suggest possibility controlling pressure relief valve installed top device reduce whenever detected.