A contra-rotating free-spinning energy harvester

In the field of energy harvesting from motions or vibrations, enhancing the performance of a harvester under ultralow frequency and intermittent input sources remains challenging. To address this issue, this paper presents an electromagnetic energy harvester design featuring a novel design and compact arrangement of dual one-way bearings in the magnet and coil layers. The unique one-way bearing design is capable of significantly enhancing the energy harvesting performance by eliminating springs to reduce friction for contra-rotating high-speed free-spinning motions. The devised harvester is characterised under various controlled low-frequency excitation conditions, yielding a maximum average power of 8 mW at the excitation frequency of 1 Hz. A finite element simulation is then performed to validate the performance of the energy harvester. Furthermore, with a minimized form factor, the energy harvesting capability of the proposed harvester in real-life applications of powering electronic devices is demonstrated. The innovative approach from this work holds substantial promise for high-performance energy harvesting from reciprocating motions in ultralow frequency scenarios.