A Curved Electromagnetic Energy Harvesting System for Wearable Electronics

Abstract

In this paper, a new curved electromagnetic energy harvesting system is designed, developed, and tested. This system is able to capture energy through oscillatory motion and proposes the use of a curved oscillatory electromagnetic harvester over the regular linear electromagnetic harvester due to its ability to harvest energy in two directions while walking/running. This paper also examines how the curvature of an oscillatory energy harvester affects its conversion efficiency from kinetic energy to electrical energy which is then stored. An enameled copper coil, having 1000 windings, is fixed at the center of a high-density polyethylene tube, in which a freely moving neodymium iron boron (NdFeB) magnet is housed. The $0.21~{\mathrm{ m}} \times 0.016~\text{m}$ harvester curved at a 0.25 m radius is able to produce the no load dc voltages of between 2.55 and 4.07 V when shaken at frequencies ranging from 2 to 5Hz. The 0.140 kg prototype is also tested by the human body motion during walking and running. The experimental results show that the harvester could generate a power of 5.185 mW.