Design and experiments of a self-charged power bank by harvesting sustainable human motion

In this study, a self-charged power bank integrated with an energy harvester was developed to harness human biomechanical energy and sustainably recharge a power bank. In the energy harvester, a spring–mass damping system is used to transform the human body’s movement during walking into the rotation of a gear train and drive rotary generators to produce electricity to recharge the battery through a rectifying circuit. A mathematical model was built to examine the power output of the energy harvester under different excitation conditions. A prototype was built to test the performances of the harvester, and experiments on the prototype fixed on the ankle, wrist, and torso were conducted, which indicated that the measured power output was 0.35 W, 0.16 W, and 10 mW, respectively, when testers walked at 2.0 m/s (the circular frequency of foot step is about 14.5 rad/s). The experiments indicate that a higher walking velocity as well as excitation amplitude and frequency could result in higher output power.