II. PRINCIPLE OF HPWC
A. Human Power Harvesting in HPWC
Based on its virtues of independence on climate and
geography condition, energy conservation and environmental
protection, human power is well suited to provide energy to
mobile electronic products. For HPWC, it mainly harvests the
kinetic energy of human body, which is produced by the muscle
of body parts such as hand, arm, finger, leg and so on. In detail,
muscle converts metabolism energy into kinetic energy with
the maximum conversion efficiency of 25% [24]. In HPWC,
using a hand crank, the kinetic energy of hand rotary motion
can be collected and then delivered to magnet via transmission
mechanism. In order to increase the revolving speed of magnet,
four gears meshing with each other were employed as the
transmission mechanism. According to the definition of
transmission ratio, one has: