The Effect of Electromechanical Coupling on the Bennet Doubler Based Vibration Energy Harvester

The analysis of the single-capacitor Bennet doubler based electrostatic vibration energy harvester (e-VEH) operation is carried out taking into account the variable capacitor moveable electrode dynamics. The variable capacitor with out-of-plane overlap geometry is used for simulations. The electromechanical model of the investigated e-VEH is developed taking into account electromechanical coupling (EMC) between the variable capacitor electrodes. Time dependences of the output voltage and power are obtained. It has been established that the presence of electrostatic force shifting the resonant frequency of the movable electrode vibrations toward higher frequencies can have a significant influence to the e-VEH operation. It has been observed that at frequencies of external vibrations lower than the movable electrode initial resonant frequency, the efficiency of the system with EMC is significantly lower than the efficiency without EMC. However, at frequencies greater than the resonant one, while the voltage without taking into account EMC has a steady value, the voltage taking into account EMC has the character of exponential growth, subsequently passing into a steady state, also due to the influence of EMC.