Investigation of phase-controlled wave-power buoy

Two methods, reactive control and latching control, for achieving optimum phase of the oscillation of a wave-energy converter, are compared and discussed numerically for a heaving semi-submerged sphere. Absorbed energy is slightly lower for latching control than for reactive control, but the need for reversing energy flow, during parts of each heave cycle, is avoided. Moreover, some numerical and experimental results are reported for a heaving axisymmetric buoy that is shaped as a cylinder with hemispherical bottom. Phase control results in very significantly improved performance for wave frequencies below the natural frequency of the heaving buoy.