A quasi-zero adjustable stiffness magnetoelectric generator of an inverted pendulum for ultra-low frequency blue energy harvesting

As a common renewable energy source of the ocean, wave energy has the advantages of high energy density and wide distribution, but it is also characterized by time variability and ultra-low frequency, which makes it a challenging task to obtain. Here, by combining the quasi-zero adjustable stiffness (QZS) mechanism with magnetoelectric (ME) composites, we propose a QZS magnetoelectric generator (QZS-MEG) to effectively adapt to wave energy in different low-frequency (< 2 Hz) environments. To improve the energy response and conversion efficiency at ultra-low frequencies, an inverted pendulum and abrupt magnetic change architecture are designed in the QZS mechanism and ME generator, respectively. Moreover, the adjustable clamp, flexible hinge and swing block are further introduced to accommodate the variable frequency and multi-directional wave energy. Finally, the practicability of QZS-MEG is verified through experiments. When the driving frequency ranges from 0.5 to 1.6 Hz, QZS-MEG reaches a maximum output power of 1.37 mW at 0.33 M Omega and shows broadband non-resonance characteristics. This work may provide an effective strategy for the large-scale acquisition of ultra-low frequency blue energy.