An automatic energy storage and release high-performance micro-harvester with steady-state output for low-frequency random energy harvesting

Abstract

Harvesting wideband and random vibration energy in the vehicle environment is a promising route to power mobile electronic devices. Conventional energy harvesters cannot realize steady-state output, making the energy management circuit design difficult. This work presents an electromagnetic harvester with a counterweight unit, a gearbox, and a generator, which can be adapted to wideband automatic energy storage and quantized output release. The counterweight unit with the low-frequency response can effectively sense the weak vibration. The coil spring in the energy storage gear train is in particular used to store low-frequency random vibration energy in the environment and release the energy stored by the coil spring by switching the gear train. Finally, the coil spring drives the generating gear train to realize the steady-state output of mechanical energy to electrical energy. At a frequency of 2.5 Hz and an acceleration of 0.4 g, the average output power of the automatic energy storage and steady-state output release energy harvester (ASSR) by using a coil spring to first store energy and then quantize the output is 114.5 times higher than that of the method of continuous generating without using a coil spring. The ASSR's energy output can charge the lithium battery (3.7 V, 40 mAh) from 2.6 to 3.716 V during a 60 km ride at an average speed of 12.7 km/h while powering the mobile phones and Bluetooth devices continuously through the energy management circuit. The strategy shows the great potential of micro-energy harvester in various wideband random vibration environments for powering electronics.