Energy Harvesting from Mechanical Vibrations Essay Example

Energy Harvesting from Mechanical Vibrations Essay Human power-based energy harvesting strategies for mobile electronic devices a. Describe the application (10%) 1. 2. 3 Wearable or implantable medical devices Implantable or wearable medical devices refer to any device that could help monitor metabolic parameters, assist defective physical function or cure diseases. Structural devices such as artificial joints, vascular grafts and artificial valves are called passive devices and their working does not need external power. But active devices can consume energy with different orders of magnitude from microwatts to several watts, as shown in Table 2. b.Identify how the mechanical vibration is induced (20 %) 2. 3. 1 Characterization of vibration system for motion harvesting Displacement driven generators are typically inertial mechanism-based, second-order vibration systems excited by periodical human body movement of the legs, limbs or feet. Ideally, these systems can be described as spring-mass systems , as shown in Fig. 5. The frame i s attached to the moving body. A proof mass (m) is suspended inside. A spring (with stiffness of k) and a damper (with damping coefficient of c) couple the relative movement (Z1) between these two parts. Z1 induces electricity by the ransduction mechanism of the damper. Assuming that the mass of the vibration source is significantly larger than that of the seismic mass and therefore not affected by its presence, and that the external excitation is harmonic, then the differential equation of motion is described as (5) The standard steady-state solution for the mass displacement is given by (6) where f is the angle phase given by : (7) Maximum energy can be extracted when the excitation frequency matches the natural resonant frequency of the generator system ? n, given by : (8) The vibration structure for which resonant frequencies ange from 10 kHz to 1 MHz is good at converting the high frequency energy of machine vibration with small amplitude to electrical energy. However, the huma n body moves at a low frequency of less than 10 Hz [49] and at high amplitude. For the human being as the excitation source, a specific design must be developed. The state-of-the-art technique to harvest vibration energy from low frequency excitation is especially reviewed in this paper. It should be noted that the damping coefficient [50] is comprised of parasitic losses, cp, and electrical energy extracted by the transduction mechanism, ce. As the xtracted energy is characterized by the transduction mechanism or the coupling efficiency of ce, a comprehensive review of existing transduction mechanisms and their specific characteristic equations are presented and compared in the following section. c. Describe how the operation utilises the source of mechanical vibration to achieve the desired outcomes (30%) 2. 2. 3 Electromagnetic induction Based on Faraday’s law on electromagnetic induction, the variation in magnetic flux through an electrical circuit yields an open circuit voltage. Almost all traditional conductors take the form of a coil and the electricity is enerated by either the relative movement of the magnet and coil, or by changes in the magnetic field. The most natural method to innocuously tap human activity power is by placing sets of coil and magnet to extract their relative activities [43,44]. Low transduction efficiency yet high power output [45] due to cumbersome mounting and bulk scale has been described in many applications. Their power generation ability is characterized by direct proportion to the scale of coils or length of stroke. However, innovative designs [46] particularly engineered by human activity outperform their predecessors everal times 2. 3. 2 Piezoelectric property An expression for the piezoelectric damping coefficient is [51] , (9) where k is the piezoelectric material electromechanical coupling factor, Cload is the load capacitance, and Rload is the load resistance. The amount of energy generated by piezoelectric d. Relate this to the course material covered (20%) Page 7 of the Human movement one. http://en. wikipedia. org/wiki/Piezoelectricity http://www. sensorsmag. com/sensors/acceleration-vibration/sonic-nirvana-mems-accelerometers-acoustic-pickups-musical-i-5852 http://www. engineeringvillage. com. zproxy. lib. monash. edu. au/controller/servlet/Controller? CID=quickSearchAbstractFormatamp;searchtype=Quickamp;SEARCHID=75055c4f13e72f6c8b0M5b5dprod2con2amp;DOCINDEX=5amp;database=2285571amp;format=quickSearchAbstractFormatamp;tagscope=amp;displayPagination=yes http://www. engineeringvillage. com. ezproxy. lib. monash. edu. au/controller/servlet/Controller? CID=quickSearchAbstractFormatamp;searchtype=Quickamp;SEARCHID=75055c4f13e72f6c8b0M5b5dprod2con2amp;DOCINDEX=14amp;database=2285571amp;format=quickSearchAbstractFormatamp;tagscope=amp;displayPagination=yes http://www. ngineeringvillage. com. ezproxy. lib. monash. edu. au/controller/servlet/Controller? CID=quickSearchAbstractFormatamp;search type=Quickamp;SE ARCHID=75055c4f13e72f6c8b0M5948prod2con2amp;DOCINDEX=52amp;database=2285571amp;format=quickSearchAbstractFormatamp;tagscope=amp;displayPagination=yes Abstract Energy problems arise with the proliferation of mobile electronic devices, which range from entertainment tools to life saving medical instruments. The large amount of energy consumption and increasing mobility of electronic devices make it urgent that new power sources hould be developed. It has been gradually recognized that the human body is highly flexible in generating applicable power from sources of heat dissipation, joint rotation, enforcement of body weight, vertical displacement of mass centers, and even elastic deformation of tissues and other attachments. These basic combinations of daily activities or metabolic phenomena open up possibilities for harvesting energy which is strong enough to power mobile or even implantable medical devices which could be used for a long time or be recharged permanen tly. A comprehensive eview is presented in this paper on the latest developed or incubating electricity generation methods based on human power which would serve as promising candidates for future mobile power. Thermal and mechanical energy, investigated more thoroughly so far, will particularly be emphasized. Thermal energy relies on body heat and employs the property of thermoelectric materials, while mechanical energy is generally extracted in the form of enforcement or displacement excitation. For illustration purposes, the piezoelectric effect, dielectric elastomer and the electromagnetic induction couple, which can convert orce directly into electricity, were also evaluated. Meanwhile, examples are given to explain how to adopt inertia generators for converting displacement energy via piezoelectric, electrostatic, electromagnetic or magnetostrictive vibrators. Finally, future prospects in harvesting energy from human power are made in conclusion. Keywords mobile electronic dev ice, human power, energy harvesting, micro/miniaturized generator, battery, green energy 1 Introduction 1. 1 Energy issue and large scale solution Electricity is increasingly consumed by proliferating electronic products and appliances.The development of an energy-efficient, stable, yet cheap and convenient power source has been the focus of research. Meanwhile, the energy issue has always been a potential threat to society ever since industrialization. The biggest problem is the environmental and health pressure caused by generating electricity using fossil fuels. Emissions of primary small particles (less than 2. 5 ? m), secondary small particles (less than 10 ? m), sulphur dioxide and nitrogen oxides directly cause pneumoconiosis, progressive massive fibrosis, emphysema, chronic bronchitis, and accelerated loss of lung function1.Greenhouse gases are also contributing to the warmer climate and increasing number of floods, tornadoes and other forms of disastrous weather. According to a WHO study [1], 1500000 people were killed by greenhouse gas-related diseases from 1900 to 2000. Clearly, sustainable and long-term development can not rely only on the finite reserves on earth. Although energy efficiency is improving and recoverable reserves are increasingly being adopted, exhaustion of traditional energy is just around the corner. It is now recognized that renewable and clean energy sources are among the 2. Displacement driven generator (inertia vibration) 2. 3. 1 Characterization of vibration system for motion harvesting Displacement driven generators are typically inertial mechanism-based, second-order vibration systems excited by periodical human body movement of the legs, limbs or feet. Ideally, these systems can be described as spring-mass systems , as shown in Fig. 5. The frame is attached to the moving body. A proof mass (m) is suspended inside. A spring (with stiffness of k) and a damper (with damping coefficient of c) couple the relative movement (Z1) between these two parts.Z1 induces electricity by the transduction mechanism of the damper. Assuming that the mass of the vibration source is significantly larger than that of the seismic mass and therefore not affected by its presence, and that the external excitation is harmonic, then the differential equation of motion is described as mâ‚ ¬z? t? ? c_z? t? ? kz? t? ? –mâ‚ ¬y? t? : (5) The standard steady-state solution for the mass displacement is given by z? t? ? ! 2 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ? k=m– ! 2? 2 ? ?c! m? 2 q Y0sin ?! t – f? , (6) where f is the angle phase given by f ? tan– 1 c! k – ! 2m _ _ : (7) Maximum energy can be extracted when the excitation frequency matches the natural resonant frequency of the generator system ? n, given by !n ? ffiffiffiffi k m r : (8) The vibration structure for which resonant frequencies range from 10 kHz to 1 MHz is good at converting the high frequency energy of machine vibration with small amplitude to electrical energy. However, the human body moves at a low frequency of less than 10 Hz [49] and at high amplitude. For the human being as the excitation source, a pecific design must be developed. The state-of-the-art technique to harvest vibration energy from low frequency excitation is especially reviewed in this paper. It should be noted that the damping coefficient [50] is comprised of parasitic losses, cp, and electrical energy extracted by the transduction mechanism, ce. As the extracted energy is characterized by the transduction mechanism or the coupling efficiency of ce, a comprehensive review of existing transduction mechanisms and their specific characteristic equations are presented and compared in the following section. 2. 3. 2 Piezoelectric propertyAn expression for the piezoelectric damping coefficient is [51] ce ? 2m! 2n k2 2 ffiffiffiffiffiffiffif fiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ! 2n ? 1=? RloadCload? 2 q , (9) where k is the piezoelectric material electromechanical coupling factor, Cload is the load capacitance, and Rload is the load resistance. The amount of energy generated by piezoelectric Accession number: | 20102713059950| | Title: | Towards a self-tunable, wide frequency bandwidth vibration energy harvesting device| | Authors: | Challa, Vinod R. 1 ; Prasad, M. G. 1 ; Fisher, Frank T. | | Author affiliation: | 1 Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, United States | | Corresponding author: | Challa, V. R. ([emailprotected] edu) | | Source title: | ASME International Mechanical Engineering Congress and Exposition, Proceedings| | Abbreviated source title: | ASME Int Mech Eng Congress Expos Proc| | Volume: | 6| | Monograph title: | Proceedings of the ASME International Mechanical Engineering Congress and Ex position 2009, IMECE2009| | Issue date: | 2010| | Publication year: | 2010| | Pages: | 57-65| | Language: | English| ISBN-13: | 9780791843796 | | Document type: | Conference article (CA)| | Conference name: | 2009 ASME International Mechanical Engineering Congress and Exposition, IMECE2009| | Conference date: | November 13, 2009 November 19, 2009| | Conference location: | Lake Buena Vista, FL, United states| | Conference code: | 80879 | | Publisher: | American Society of Mechanical Engineers, 3 Park Avenue, New York, NY 10016-5990, United States| | Abstract: | Vibration energy harvesting is increasing in popularity due to potential applications such as powering wireless sensors and ultra low power devices.For efficient energy harvesting, matching the device frequency to the source frequency is a major design requirement. Since mechanical vibrations differ in characteristics (frequency and acceleration amplitude), it is difficult to design an individual energy harvesting device for every source. Recently, several groups have pursued techniques to tune the resonance frequency of the vibrating structure through active and passive methods.In this paper, work has been done to attain a self-tunable energy harvesting device, which utilizes a magnetic force resonance frequency tuning technique to tune the device. The device is successfully tuned with in a bandwidth of  ± 27% of its untuned resonance frequency, considering root mean square of the peak power output as the cutoff for frequency bandwidth. Since the technique is semi-active, energy is only consumed to tune the resonance frequency and is not required to remain at that specific frequency. The device consists of a