Session: 09-05-04 Wave Energy: Power Take Off Systems

Submission Number: 178249

Study on Nonlinear Gyroscopic Motion of a Gyroscopic Wave Energy Converter For Maximizing Energy Absorption Efficiency 

Renewable energy plays a crucial role in establishing a carbon-neutral society. Among the various renewable sources, wave energy stands out due to its higher density compared to wind and solar energy.  A Gyroscopic Wave Energy Converter (GWEC), which generates electricity from the gyroscopic effect due to wave-excited body motion, is notable for its built-in structure. Furthermore, it provides significant control flexibility owing to its two control parameters: the damping coefficient of the PTO system and the rotational speed of the flywheel. However, it is not easy to address such a complex interaction among waves, body motion, and gyroscopic motion. Recently, an interaction theory was developed, which highlighted that the GWEC can realize the maximum theoretical energy absorption efficiency at all wave frequencies within the linear theory. Nonetheless, the potential for frequency-independent maximum energy absorption efficiency through the nonlinear gyroscopic motion of the GWEC remains unexplored, as previous studies have primarily focused on the linear gyroscopic motion of the GWEC.
In this study, the energy absorption efficiency of the nonlinear gyroscopic motion of the GWEC was investigated. To demonstrate such motion, various wave amplitudes of incident waves were employed, including high wave steepness conditions. Based on the wave–body–gyroscope interaction theory and a real-time wave exciting force prediction method, the motion of the GWEC and the energy absorption efficiency were computed in the time domain. The first-order response analysis indicated that the theoretical maximum energy absorption efficiency could be achieved even with the nonlinear gyroscopic motion of the GWEC. In addition, the results emphasized that the optimal control parameters of the GWEC have a distinct relationship with the wave amplitude of the incident waves. This study provides insights into the fundamental characteristics of the GWEC to achieve the theoretical maximum energy absorption efficiency, regardless of the wave conditions. We believe that the GWEC represents a promising option for energy generation on a global scale.

Presenting Author: Ryo Yoshimura The University of Osaka

Presenting Author Biography: Ryo Yoshimura holds a Master of Engineering degree from The University of Osaka, where he is currently pursuing his Ph.D. in the field of wave energy conversion. His research focuses on improving the energy absorption efficiency of wave energy converters. After conducting studies on point absorbers, he shifted his focus to gyroscopic wave energy converters and continued to examine their performance and control characteristics.

Authors:

Ryo Yoshimura The University of Osaka
Takahito Iida The University of Osaka