In this study, the effectiveness of an oscillating-body WEC with a tuned inerter (TI) proposed by the authors is shown through wave flume testing. The TI mechanism consisting of a tuning spring, a rotational inertial mass, and a viscous damping component is able to increase energy absorption capability by taking advantage of the resonance effect of the rotational mass. This mechanism has been recently introduced for civil structures subjected to external loadings such as earthquakes and winds to decay vibration response immediately. The authors applied this mechanism to oscillating-body WECs and showed that the proposed WEC increased the power generation performance and broadened the effective frequency range without increasing the mass of the buoy itself through numerical simulation studies. To verify the validity of the proposed WEC experimentally, a small-scale prototype of the proposed device is designed and wave flume testing is carried out with various regular wave inputs of different frequencies. The results show that the WEC with the properly adjusted TI mechanism demonstrates better power generation performance compared to the conventional WEC over a wide range of wave frequencies.

No abstract

A novel point absorber wave energy converter with a tuned inertial mass (TIM), which is capable of significantly increasing the energy absorption and broadening the effective bandwidth, is proposed in this paper. The mechanism of the TIM has originally been introduced in the field of civil engineering as a passive energy absorber for structures subjected to external loadings such as earthquakes. It relies on attaching an additional tuning spring and a rotational inertial mass to the primary system, to improve the energy absorption performance by amplifying the displacement of the damper. Thus, considering typical point absorbers modeled as a mass-spring-dashpot system similar way to civil structures, the application of the TIM to wave energy converters can be expected to have a significant effect. In this paper, numerical investigation on the power generation performance of a point absorber with the TIM is conducted under random sea waves. The amplitude response and power generation performance are compared with the conventional point absorber, considering both non-resonant and resonant buoy cases. It is shown that by properly designing the tuning spring stiffness and generator damping, the rotation of the generator can be amplified compared to the buoy, increasing the power absorption drastically.

This paper introduces the mechanism of a buoy-type wave energy converter (WEC) with a tuned inertial mass (TIM) mechanism. The TIM mechanism consists of a rotational mass and motor connected in series with a tuning spring. While it is common to control the current of the power take-off system, the stiffness of the spring is tuned in addition so that the inertial mass part resonates with the dominant frequency of the wave motion. The method to design the parameters to maximize the power generation capability is introduced and numerical studies for both narrowband and broadband sea states are carried out. It is shown that the proposed device demonstrates better energy harvesting performance compared to the WEC without the TIM mechanism to band-limited stationary random vibration.

In this study, the effectiveness of an oscillating-body WEC with a tuned inerter (TI) proposed by the authors is shown through wave flume testing.The TI mechanism consisting of a tuning spring, a rotational inertial mass, and a viscous damping component is able to increase energy absorption capability by taking advantage of the resonance effect of the rotational mass. This mechanism has been recently introduced for civil structures subjected to external loadings such as earthquakes and winds to decay vibration response immediately. The authors applied this mechanism to oscillating-body WECs and showed that the proposed WEC increased the power generation performance and broadened the effective frequency range without increasing the mass of the buoy itself through numerical simulation studies. To verify the validity of the proposed WEC experimentally, a small-scale prototype of the proposed device is designed and wave flume testing is carried out with various regular wave inputs of different frequencies. The results show that the WEC with the properly adjusted TI mechanism demonstrates better power generation performance compared to the conventional WEC over a wide range of wave frequencies.