A pulsed freestanding triboelectric nanogenerator and power management circuit to harvest rotation energy from an automobile brake

A lot of mechanical energy is lost in the braking process of automobiles, and it is feasible to harvest the energy and power electronic devices by using the technology of a triboelectric nanogenerator (TENG). In this study, we propose a pulsed freestanding TENG (PF-TENG) with a grid structure to harvest mechanical energy in the braking process, and use electric brushes to achieve a unidirectional pulsed output. We also design a passive power management circuit (P-PMC) to process and store the energy output. First, the general analytical solutions of the open-circuit voltage, short-circuit charge and output capacitance are derived from the theoretical model. According to the simulation results by using the finite element method, it is proved that the output energy of PF-TENG is independent of the grid number and proportional to the rotation speed. Second, the circuit simulation results demonstrate that P-PMC achieves impedance matching with the PF-TENG. The output power can maintain the maximum value under a wide load range and the optimal conversion efficiency is 94%. It is also found that the charging speed increases when the inductance value or the capacitance value decreases. In addition, a large pulse width makes the PF-TENG discharge completely. Finally, it is demonstrated that the PF-TENG can be used as a sensor to detect the wear depth of the brake pad with the open-circuit voltage.