A bistable X-structured electromagnetic wave energy converter with a novel mechanical-motion-rectifier: Design, analysis, and experimental tests

Highlights: • A novel bistable X-structured ocean energy converter is proposed and investigated. • The inherent bistable stiffness and quasi-zero stiffness are shown to be very beneficial to enhance ocean power generation. • The novel MMR with the energy-storing-releasing mechanism achieves 200% higher instant voltage than its traditional counterparts. • It has great potentials in powering electronic devices for monitoring and sensing in smart oceans. Beneficial nonlinearities have been intentionally introduced to improve energy harvesting performance. However, few results are reported on the issues of exploiting bistable and quasi-zero stiffness structures or mechanisms simultaneously to enhance ocean energy conversion in the literature. In this study, a novel bistable electromagnetic wave energy converter is proposed, which includes a bio-inspired X-shaped supporting structure/mechanism and a mechanical-motion-rectifier. This is for the first time that the bistable stiffness and quasi-zero stiffness are employed together (in all working range) to strengthen wave energy conversion, by developing a novel bistable X-structured system as a wave energy converter, which can bear with large vibration stroke simultaneously. Additionally, a novel mechanical-motion-rectifier with a novel energy-storing-releasing mechanism is specially designed as the power take-off system to convert linear motion to rotary motion, which greatly improves the instant voltage and power generated. The novel X-structured system demonstrates very designable nonlinear bistable and quasi-zero stiffness and thus can significantly enhance the wave energy conversion performance. Compared with traditional linear converters, much more power can be generated, especially in the low-frequency range due to the quasi-zero and bistable properties. The experiments show that, with the wave height of 0.15 m as well as the wave period of 4 s, it can generate a voltage peak at around 15 V and a power peak at about 1 W. The present results indicate that, the proposed nonlinear bistable X-structured system holds promising potentials in acting as a floating-point energy converter, which could power seashore environmental monitoring systems and wireless communication devices for smart oceans.