Review of vibration‐based electromagnetic–piezoelectric hybrid energy harvesters

Summary These days the health monitoring of machines and structures is performed using wireless sensor nodes (WSNs). The disadvantage of short life span of batteries in WSN is overcome by using energy harvesting techniques and the required power is extracted from the environment for operating WSNs. The energy available in environment is in the form of thermal, solar, wind, vibration, RF and acoustic energy. The Piezoelectric (PE), electromagnetic (EM), electrostatic and triboelectric transduction may be utilized to harvest power from vibration energy available on structure which otherwise may be going waste. Moreover, for enhancing power generation hybrid vibration energy harvesters are developed by combining two of such transduction mechanisms. The piezoelectric and electromagnetic based hybrid harvesters are discussed in this work for vibration energy harvesting. The hybrid vibration energy harvesters are classified here as resonant, frequency tuned, nonlinear, non‐resonant, multi‐mode and frequency up conversion harvesters. The architecture, input excitation levels and performance of the reported hybrid harvesters is discussed and compared to know the advantage of harvester's configuration. Moreover, all the reported harvesters are compared on the basis of input vibration to which these harvesters are subjected, their resonant frequencies, size, output voltage, power levels and power density. Most of the developed hybrid energy harvesters are resonant harvesters. The multi‐mode hybrid energy harvesters are generating comparatively higher power levels of up to 250.25 mW and power density 2669.3 µW/cm3 in the reported literature. The overall voltage and power generation range of the hybrid harvesters is from 0.131 mV to 26 V and 0.637 µW to 250.25 mW. Moreover, the power density for the reported energy harvesters is in the range from 1.96 µW/cm3 to 2669 µW/cm3.