... node within wideband frequency vibrations 36 Sustainable Energy Harvesting Technologies – Past, Present and Future 2.5.2 Nonlinear structures The theory of vibration energy harvesting using ... mechanism only consumes power during the tuning operation and uses negligible energy 32 Sustainable Energy Harvesting Technologies – Past, Present and Future once the resonant frequency is matched to ... 30 Sustainable Energy Harvesting Technologies – Past, Present and Future Fig Comparisons of normalized power density of some existing piezoelectric vibration energy harvesters 2 .3 Electrostatic...