Hybrid vibration and wind energy harvesting using combined piezoelectric and electromagnetic conversion for bridge health monitoring applications

In this paper a novel multimodal hybrid bridge energy harvester (HBEH) using combined piezoelectric and electromagnetic conversion is reported. The architecture, fabrication, and characterization of the harvester is discussed. The devised HBEH consists of a permanent magnet, a wound coil, a piezoelectric plate, an airfoil, and two cantilever beams attached to a base support frame. The upper cantilever is holding a permanent magnet and an airfoil as tip mass. A piezoelectric plate is bonded on this beam near its fixed end. On the other hand, the lower beam holds a wound coil. The coil is adjusted in such a way that it is in-line and close to the permanent magnet. The harvester is capable of converting bridge vibrations and ambient wind energy into useful electrical energy to operate wireless sensor nodes (WSNs) for the health monitoring of bridges. Experimentally, the HBEH operated at three, low frequency resonant modes, ranging from 11 to 45 Hz, concentrated around 11, 38 and 43 Hz. Moreover, under sinusoidal base acceleration of 0.6 g, the harvester produced a maximum power of 2214.32 mu W across a matching impedance of 28 Omega from its electromagnetic portion at 1st resonance (11.1 Hz). However, a peak power of 155.7 mu W was generated by the harvester from its piezoelectric part under 0.4 g base excitation across 130 k Omega load resistance. Furthermore, at 6 m/s pulsating wind speed, the harvester generated load voltages of 25 mV and 114 mV from its electromagnetic and piezoelectric portions when connected to optimum load impedance of 28 Omega and 130 k Omega respectively.