High-efficiency compressive-mode energy harvester enhanced by a multi-stage force amplification mechanism

Harnessing ambient vibration energy using piezoelectric materials is a promising alternative solution to batteries to inexhaustibly power small-scale mobile devices. This paper presents an innovative energy harvester, named high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH). It consists of a pair of elastic beams and a flex-compressive center where the piezoelectric element bears a dynamic compressive load. The compressive mode is preferred than the commonly-used bending mode and tensile mode due to the superior compressive strength of piezoceramics. To cater to the characteristic of piezoceramics: large ultimate stress, but extremely small ultimate strain, a multi-stage force amplification mechanism is developed in the design. The HC-PEH shows superior capability of high power output and favorable nonlinear phenomena at low frequency range. Under an acceleration of 0.5 g (g = 9.8 m/s²), a maximum power of 19 mW is produced at 21 Hz, which is about one order of magnitude higher than the power output of energy harvesters previously reported. The capability of high power output of the HC-PEH demonstrates the practicability of using energy harvesters to power most of wireless sensors.