Attempts have been made to convert the motion of automobiles and ships induced by road surface roughness and ocean waves into electricity using generators. Although wave-induced sea-surface roughness causes significant ship motion, it also offers considerable potential for wave energy harvesting, which can contribute to suppress such motion. Since 2008, the authors have been researching and developing small ships called WHzer (Wave Harmonizer) that both suppress motion and harvest wave energy. The development history of the small ships was summarized along with the functions of each configuration. The WHzer consists of a cabin, multiple floats, and a suspension system, in which the cabin and floats are connected by springs and suspension linkages. To suppress cabin motion, the springs are actively controlled to expand or contract based on the vertical velocity of the cabin. During power generation, electricity is produced when the springs return to their original length, driving a generator through a rack-and-pinion mechanism. The control model can be switched between the motion reduction mode and energy harvesting mode depending on whether people are onboard. A 1.6 m scale model, assuming an 8 m full-scale ship, was fabricated and tested under wave conditions in the IIS Ocean Engineering Basin. Subsequently, a 3.3 m prototype was constructed and tested in Yuya Bay off Nagato City in Yamaguchi Prefecture and off Hiratsuka City in Kanagawa Prefecture. The performance of motion reduction and energy harvesting was evaluated in real sea conditions. Based on the results obtained from the prototype experiments, the potential reduction in energy consumption was estimated for a fishing vessel equipped with this technology. In the future, further research and development are expected not only in wave energy harvesting but also in new energy-saving ships that utilize wave energy for motion suppression, including technologies that enhance propulsion through wave-energy-assisted propulsion systems.
KITAZAWA et al. (Sun,) studied this question.