Papers by Keyword: Power Harvesting

Abstract: In future, demand on portable electronic devices will create the requirements of enduring recharged sources of power. A non-environmental friendly conventional battery with limited lifetimes has no longer feasible option. One of the mostly used solution is the piezoelectric composite structure with sensing and also actuating capabilities, mainly as a MEMS device. The optimum between actuating and energy harvesting functions is difficult to obtain. The article is presenting a study regarding the posibility to optimize both functions, performed using an analytical model and also by simulation using a FEA model.

Abstract: This paper focuses on the design and development of a low-cost multifunctional composite component integrated into a shoe hill that generates power in the order of milliwats (mW) through piezoceramic (PZT) stacks and stores this harvested energy in a capacitor integrated into the composite. The use of a thin-film lithium battery integrated into the composite is also explored as a means of permanent power storage. PZT bimorph elements are stacked in a cantilever manner. The space in-between and around the elements is being filled with foam, which provides structural support as well as walking comfort. An insole composite with a PZT layer is also developed that is capable of producing 2.2mW of power to give a total power output of 12.2mW for the in-heel insole combination. The experimental results revealed that the use of PZT bimorph elements (d33=110) instead of polyvinylidene difluoride PVDF sheets (d33=20) increased the power generation potential over five folds, which is further compounded by stacking the PZT elements.

Abstract: In this article, a novel electro-mechanical energy conversion model of power harvesting from the vibration-induced the piezoelectric stator of the traveling wave rotary ultrasonic motor was proposed. Based on the curvature basis approach, the relationship between the deduced voltage and the mechanical stain induced by piezoelectric polarization was formulated. In addition to the relationships between the maximum induced voltages at the resonance frequency, the conversion energy density and the dimensions of the piezoelectric stator were also derived. The analytical model shows that the vibration-induced voltage is proportional to the exciting electrical voltage magnitude and square of height of the piezoelectric ceramic (PZT) but is inversely proportional to the permittivity of PZT and the damping coefficient of the stator. Some simulations and experimental results demonstrate that the maximum output voltage coincides with the energy conversion analytical model.

Abstract: The paper presents the ability of the piezoelectric devices to capture the environmental vibrations, in order to generate electric power for supplying electronic small portable devices. Theoretical and experimental investigations were performed, both for stack and cantilever beam configuration of the piezoelectric devices, with good agreement between results. An improved mechanical architecture is proposed.

Abstract: A composite piezoelectric energy converter intended for Micro-electromechanical Systems (MEMS) from background vibrations is presented. The converter is composed of a piezoelectric circular plate bonded to a brass substrate with different diameters. The vibration of the structure is analyzed based on the thermal-piezoelectric-elastic theory and Kirchhoff’s assumption. The vibration solutions and the relation between the vibration and output charge are obtained. The effects of geometric characteristics and environment temperatures on the electrical energy generation are numerically discussed. The numerical results show that the vibration-induced voltage is proportional to the excitation frequency and the thickness of the device, but is inversely proportional to the temperature of the environment. The experimental data show good agreement with the energy conversion analytical model.

Abstract: The certification of retro-fitted structural health monitoring (SHM) systems for use on aircraft raises a number of challenges. One critical issue is determining the optimal means of supplying power to these systems, given that access to the existing aircraft power-system is likely to be problematic. Other conventional options such as primary cells can be difficult to certify and would need periodic replacement, which in an aircraft context would pose a serious maintenance issue. Previously, the DSTO has shown that a structural-strain based energy harvesting approach can be used to power a device for SHM of aircraft structures. Acceleration-based energy harvesting from airframes is more demanding (than a strain based approach) since the vibration spectrum of an aircraft structure varies dynamically with flight conditions, and hence a frequency agile or (relatively) broad-band device is often required to maximize the energy harvested. This paper reports on the development of a prototype vibro-impacting energy harvester with a ~59 gram flying mass and two piezoelectric bimorph-stops. Over the frequency range 29-41 Hz using a continuous-sine 450 milli-g r.m.s. excitation, the harvester delivers an average of 5.1 mW. From a random band-passed 25-45 Hz excitation with r.m.s. 450 milli-g, the average harvester output is 1.7 mW.

Abstract: The focus of this research is to use flying insects, coupled with lightweight electronics, to develop cyborg MAVs, or CMAVs. The premise isn't simply to build telemetry devices on the insects, but to embed controls and power systems within the insects to create MAVs that are alive yet manipulated in their actions. The model insect implemented is the Manduca sexta moth, which has a wingspan up to 10cm, a body mass up to 2 grams, and can withstand payloads up to 1 gram. The technique used to create these CMAVs is an integration of MEMS and CMOS devices onto a single silicon device that is surgically inserted into the moth. The control and sensor systems are powered by harvesting energy from the vibration of the insect flight by means of piezoelectric material and inductor-coils. Methods for controlling the insect flight include reactionary responses to visual and direct stimulation. Guidance is achieved through an ultra-wideband communication system and a micro GPS system. The primary discussion topics of this paper are the power harvesting devices employed and the control schemes used to manipulate the flight of the CMAVs.

Abstract: This paper experimentally investigates the power generation property of carbon nanotubes in an aqueous environment. Carbon nanotube based films are investigated in this paper as a new method for power generation based on ionic conductivity of the fluid. It is demonstrated that a carbon nanotube film that is bonded onto a structure vibrating with an electrolyte on the surface produces an alternating current without a net fluid flow. The power produced is smaller than for a piezoelectric material of the same size, but the CNT power generator is lightweight and has no moving parts, and does not require the structure to be immersed in an electrolyte. There are various possible applications for nanotube power generators.