Electrical Evaluation of an Omnidirectional Vibration Energy Harvester

Due to the importance of energy sources, it is a good practice to think of devices that can harvest the energy available in the environment, which would be otherwise wasted. Vibration energy harvesters are among the promising options currently under investigation to provide clean energy. However, the literature is mostly devoted to conventional vibrating harvesters that react to only one direction of excitation. In this research, a novel approach is introduced to expand this capability of conventional harvesters. To this purpose, a spiral beam was proposed as the vibrating element, in the plane perpendicular to the gravity direction, capable of extracting energy from vibrations in any direction. One of the main applications of this design is to harvest energy in environments with planar motion where the excitation changes direction, like in rotating machinery. The research began with mathematical analysis, followed by numerical simulations using commercial FEA software. An experimental prototype was assembled, using a combination of commercial and 3D printed parts, to validate the theoretical model. Voltage outputs from the piezoelectric patches on the spiral beam were then compared with the strain integral from the static analysis for different excitation directions. Results were in a good agreement, thus proving the omnidirectional capability of energy extraction. Finally, the prototype was tested with the piezoelectric patches operated on different loads, to study the electrical power output.