Development of a micro energy harvester using multiple vibration modes

Energy harvesting from ambient vibrations provides a clean and regenerative solution for powering autonomous sensors which have been widely utilized in numerous practical applications including general, medical and military industries. In recent years, numerous research works on energy harvesting have been carried out using piezoelectric, electromagnetic, electrostatic and thermoelectric mechanisms. In this work, we have proposed a micro piezoelectric energy harvester with a wide operating frequency range. The device consists of a movable circular-mass with three sets of double-layer aluminum coils, a circular-ring which incorporates a permanent magnet and a supporting beam. The harvester is capable of harnessing energy at multiple vibration modes with various 3-dimensional (3-D) excitation frequencies. The 3-D dynamic behavior and performance of the device show that the first vibration mode is an out-of-plane motion, while the second and third modes are in-plane motion at angles of 60° and 150° respectively to the horizontal axis. For a specific excitation acceleration, maximum power densities can be achieved at different 3-D vibration modes. Experimental results obtained show good agreement with that of simulated and the results indicate a good potential for the device to be developed into a practical tool for harnessing energy at multiple 3-D vibration modes.