Omnidirectional piezoelectric energy harvesting with triple-V-beam spherical joint structure for hybrid vibration and wind energy conversion

Ambient vibrations and wind energy are often multi-directional and random. Traditional unidirectional piezoelectric harvesters are efficient only in specific directions and frequencies, limiting their energy capture. To overcome this, a multi-directional piezoelectric energy harvester, based on the working principle of flexible spherical joints, was designed to efficiently capture and convert both vibrational and wind energy. The harvester features a unique structure with three V-shaped beams arranged spatially, which eliminates the directional constraints of conventional harvesters and enables omni-directional energy collection. To reveal the energy harvesting potential of the device, a dynamic model was established to describe its mechanical and electromechanical coupling behavior. Numerical simulations were conducted under different structural parameter conditions to evaluate the system's response and energy conversion capability. Experimental tests are performed under base excitation and wind-induced vibrations to assess the harvester's actual energy harvesting performance. The results show that the harvester maintains uniform stiffness in all directions, ensuring effective strain generation in at least three sub-beams under any excitation. The harvester's output voltage increases with beam length, and increases first, then decreases with beam thickness, showing a peak-to-peak voltage of 46.1 V at 23 Hz in base excitation. In wind excitation, the harvester generates a peak-to-peak voltage exceeding 20 V at a wind speed of 3.2 m/s, with power reaching 9.98 μW. The triangular cross-section bluff body demonstrates optimal performance, and adjustments to its length allow the device to adapt to varying wind speeds.