Omnidirectional hybrid wave energy harvester for self-powered sensors in sea-crossing bridges

The application of energy harvesting technology for monitoring sea-crossing bridges has gained significant attention in recent years. Utilizing continuous wave energy to supply power to sensors affixed to sea-crossing bridges constitutes an emerging trajectory towards sustainable practices. This paper proposes an omnidirectional piezoelectric–electromagnetic hybrid wave energy harvester (HWEH) based on a pendulum structure for self-powered sensors in sea-crossing bridges. The HWEH is composed of three components: a piezoelectric module, an electromagnetic module, and an energy management module. The piezoelectric module mainly consists of six piezoelectric sheets, magnets, and a pendulum. The piezoelectric sheet is bent by the impact of the pendulum, thus generating electric energy. The electromagnetic module is composed of a fixed coil and a magnet that swings with the waves. The magnetic flux in the coil changes with the swing of the magnet fixed to the bottom of the pendulum, which will produce the induced current. The generated energy will be rectified and stabilized by the energy management module to power bridge monitoring devices and sensors. Bench test results showed that the output voltage of the piezoelectric module can reach 17.4 V, and its power density can reach 0.27 W/m2; meanwhile, the output voltage of the electromagnetic module can reach 1.64 V, and its power density can reach 47.56 W/m2. In wave tank field experiment, the maximum output voltages of the piezoelectric and electromagnetic modules of HWEH reached 17.6 V and 0.87 V respectively at a wave height of 30 mm, which verified that our scheme can be practically applied. According to the case study, the power generation capacity of the device is enough to power 36 sensors for 2801 days per year.