Abstract
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.
Highlights
As the popularity of portable electronics increases, mobile power banks are necessary to ensure that devices remain available when working outdoors for long periods of time; for example, a cell phone used on a trip could be recharged from a mobile power bank
Solar cells are capable of being embedded in cloth, a large-sized solar cell is required to harness considerable energy and is available only under the condition of sufficient light, which hinders the widespread use of the solar cell
It is known that significant kinetic energy dissipates in the form of heat during human motion, which implies that the human body can be a tremendous source of energy
Summary
As the popularity of portable electronics increases, mobile power banks are necessary to ensure that devices remain available when working outdoors for long periods of time; for example, a cell phone used on a trip could be recharged from a mobile power bank. Using a mobile power bank as an oscillating mass, a new energy-harvesting device was proposed to harness human kinetic energy and sustainably recharge the power bank This energy-harvesting device consists of a battery in a power bank, which serves as the oscillating mass, spring components, gear train to speed up the motion, generator for mechanical–electrical energy conversion, and circuit interface to regulate the electricity from the generator. The proposed energy-harvesting device with a mobile power bank can be used for daily use, which could spontaneously work anywhere if carried on any part of the human body, including the torso and the upper and lower limbs. The total transient power transferred from the human motion to the oscillating system is a product of the electrical damping force Cu_ and the relative velocity u_ , which can be expressed as follows. The irregular output electricity from the generator is first rectified by the bridge
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