Design of an Optimal Low Cost Miniaturized Piezo-electric Device for Energy Harvesting from Human Motion

Abstract

Energy harvesters collect and convert energy available in the environment into useful electrical power to satisfy the power requirements of autonomous systems. Development of a low-cost miniaturized device that can harvest energy from non-traditional sources is still a very attractive point of research. Such a device is essential for a wide variety of applications such as self-powered wireless sensors and biomedical implants in which energy source is needed. This paper presents a detailed design of a miniaturized energy harvesting device that can harvest human motion energy of low frequency and wide bandwidth. Based on the concept of the 2-DOF vibration system, the optimal parameters; namely, the proper masses and spring constants for maximizing the power output, are selected to harvest energy at low frequency of 1-10 Hz and wide bandwidth of ± 20% of the mean frequency, which matches the human motion. The energy harvester is then subjected to harmonic accelerations of between 0.4g and 1g which represents the acceleration of the human motion [1]. A finite element model is developed in COMSOL to investigate the system performance with the selected parameters. Then, experimental work is carried out to validate the design methodology with the selected parameters and investigate the system performance. By varying the normalized frequency and redesigning the system parameters, the best ratio that gives the highest power output is determined. The designed energy harvester prototype is expected to generate power of microwatts to milliwatt level between the system’s two resonant frequencies. This amount of power is sufficient enough to provide additional power for wearable devices such as an activity monitor that is operated at microwatts power level hence extending the battery life. Keywords—Energy Harvesting; Two Degree of freedom; PVDF, power conditioning circuit