Experimental study on the wave energy harvesting performance of a small suspension catamaran exploiting the maximum power point tracking approach

Abstract

A novel design of a suspension catamaran, named Wave Harmonizer Type 6 (WHzer-6), is proposed and developed. The cabin is suspended upon two displacement hulls by four compression springs and suspension linkages. Owing to the newly designed pantograph and Watt’s link, the heave, pitch, and roll motions of the cabin can be separated from the twin-hull. Meanwhile, the relative surge, yaw, and sway motions between the cabin and twin-hull are suppressed. Four sets of modified rack & pinion gears and four brushed DC motor/generators (M/Gs) are utilized to transmit the forces between the cabin and twin-hull at four control locations, respectively. When the twin-hull is excited by incident waves, the induced relative vertical motions between the cabin and twin-hull are converted into rotary motion of the rotor of the M/Gs, consequently producing electrical currents. An indirect maximum power point tracking (MPPT) algorithm is developed to maximize wave energy extraction. The maximum power points (MPPs) are sought using a hill-climbing method in a quarter-ship simulation program and verified by bench tests. Then a series of towing tank experiments is carried out in regular head and beam waves, respectively. The power production, the wave energy capture width ratio (CWR), and the corresponding motion responses of the ship are investigated and analyzed. The peak power production and the peak CWR are 0.63W and 47.4%, respectively, at the wave encounter frequency of 8.89rad/s, the wave amplitude of 0.02m, and the forward speed of 1.5m/s in head waves.