Improved bistable mechanism for wave energy harvesting. (15th July 2021)

• Record Type: Journal Article
• Authors: Liu, Bingqi; Yi, Huanggao; Levi, Carlos; Estefen, Segen F.; Wu, Zhijia; Duan, Menglan
• Is Part Of: Ocean engineering. Volume 232(2021)
• Publication Date: 2021-07-15
• Subjects: Wave energy converter -- Point absorber -- Improved bistable mechanism -- Nonlinear stiffness -- Broadband energy harvesting; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2021.109139
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: As one of the renewable and clean energy sources, wave energy has high density and all-day availability characteristics. However, the development of wave energy converters has been hampered, mainly because of the low efficiency induced high levelized energy costs. The present study introduces an improved bistable mechanism composed of three linear springs, aiming to enhance the performance of a point absorber employed as a wave energy converter. The improved bistable mechanism features an asymmetric configuration of three linear stiffness springs: one horizontal and two obliques on a vertical plane. Numerical simulations based on Cummins equations in the time domain describe the point absorber dynamic behavior in regular and irregular waves. The improved bistable wave energy converter featured a wider low equivalent stiffness range than linear and conventional bistable counterparts, improving its ability to frequency shifting. Its lower potential barrier greatly improves the capture width ratio and frequency bandwidth at low excitations. Such characteristics facilitate the improved bistable wave energy converter to achieve higher efficiency than its linear and conventional bistable counterparts at low frequencies, and enhance its robustness against power-take-off damping detuning and sea state changes. These features altogether make the improved bistable mechanism an efficient alternative to explore the benefits of the bistable dynamics applied to wave energy converters. Highlights: Introduced a simple but effective improved bistable mechanism to a point absorber wave energy converter. The IB-WEC has a strong frequency shifting ability. The IB-WEC has a high power capture width ratio and wide frequency bandwidth under low wave excitations. The IB-WEC has strong robustness against PTO damping detuning and sea state changes.