16 research outputs found
Electromagnetic micropower generation - system design and analyses
There has been a huge reduction in size and power consumption of MEMS devices like transducers and sensors. These devices are usually designed to run on batteries. The limited lifespan of batteries may induce costly maintenance, in the case of contaminated areas for instance. That led to a surge of research in the area of energy harvesting. Sustainable power generation may be achieved in converting ambient energy into electrical energy. Since mechanical vibrations exist in most systems, many works focused on vibration-driven generators. In this field, the electromagnetic induction is well suited for the mechanical to electrical energy conversion. The design of the mechanical system that transmits the surrounding vibratory energy to the electromagnetic generator is a critical importance. This thesis presents an optimization of an electromagnetic microgenerator. It describes the theory, design and simulation of an energy converter based on electromagnetic induction. The objectives of this research are designing, improving the performance and operational reliability of electromagnetic microgenerator. These have been achieved by identifying the desirable design features of the electromagnetic microgenerator. Extensive analytical investigation has been conducted to develop an efficient design of an electromagnetic microgenerator. An analytical model is developed. Numerical analyses using Mat Lab software investigate the optimum design parameters to get maximum power output. This thesis deals with the design and simulation of a number of flat springs to be used for supporting the moving magnet of an electromagnetic microgenerator. The flat spring and moving magnet are equivalent to a basic spring-mass system, in which the moving magnet is attached to a platform suspended by four beams. These flat springs were designed by modelling and finite element method simulation using ANSYS 5.7. A series of structural and vibration analyses were carried out using ANSYS to evaluate the flat spring characteristics and to choose the desirable mode of vibration. Finite element method is also used for the analysis, evaluation and optimization of the electromagnetic design of the electromagnetic microgenerator. The objectives behind this analysis are to characterize the permanent magnet and to investigate the optimum position of the coil relative to the magnet. Output power is estimated using the ANSYS simulation results of the magnetic field induced on the coil. It is also found that the magnetic field of the permanent magnet in the vertical direction is higher in magnitude than the magnetic field in the horizontal direction. Estimated power was calculated for different distance between the coil and the permanent magnet. The methodology and findings in this research provided a number of contributing elements to the field of MEMS power generation, and provided an insight into the development of an electromagnetic microgenerator. This thesis is concluded with a discussion on the performance of the proposed electromagnetic microgenerator and suggestions for further research
Energy harvesting technologies for structural health monitoring of airplane components - a review
With the aim of increasing the efficiency of maintenance and fuel usage in airplanes, structural health monitoring (SHM) of critical composite structures is increasingly expected and required. The optimized usage of this concept is subject of intensive work in the framework of the EU COST Action CA18203 "Optimising Design for Inspection" (ODIN). In this context, a thorough review of a broad range of energy harvesting (EH) technologies to be potentially used as power sources for the acoustic emission and guided wave propagation sensors of the considered SHM systems, as well as for the respective data elaboration and wireless communication modules, is provided in this work. EH devices based on the usage of kinetic energy, thermal gradients, solar radiation, airflow, and other viable energy sources, proposed so far in the literature, are thus described with a critical review of the respective specific power levels, of their potential placement on airplanes, as well as the consequently necessary power management architectures. The guidelines provided for the selection of the most appropriate EH and power management technologies create the preconditions to develop a new class of autonomous sensor nodes for the in-process, non-destructive SHM of airplane components.The work of S. Zelenika, P. GljuĆĄcic, E. Kamenar and Ćœ. Vrcan is partly enabled by using
the equipment funded via the EU European Regional Development Fund (ERDF) project no. RC.2.2.06-0001:
âResearch Infrastructure for Campus-based Laboratories at the University of Rijeka (RISK)â and partly supported
by the University of Rijeka, Croatia, project uniri-tehnic-18-32 âAdvanced mechatronics devices for smart
technological solutionsâ. Z. Hadas, P. Tofel and O. Ć evecek acknowledge the support provided via the Czech
Science Foundation project GA19-17457S âManufacturing and analysis of flexible piezoelectric layers for smart
engineeringâ. J. Hlinka, F. Ksica and O. Rubes gratefully acknowledge the financial support provided by the
ESIF, EU Operational Programme Research, Development and Education within the research project Center of
Advanced Aerospace Technology (Reg. No.: CZ.02.1.01/0.0/0.0/16_019/0000826) at the Faculty of Mechanical
Engineering, Brno University of Technology. V. Pakrashi would like to acknowledge UCD Energy Institute, Marine
and Renewable Energy Ireland (MaREI) centre Ireland, Strengthening Infrastructure Risk Assessment in the
Atlantic Area (SIRMA) Grant No. EAPA\826/2018, EU INTERREG Atlantic Area and Aquaculture Operations with
Reliable Flexible Shielding Technologies for Prevention of Infestation in Offshore and Coastal Areas (FLEXAQUA),
MarTera Era-Net cofund PBA/BIO/18/02 projects. The work of J.P.B. Silva is partially supported by the Portuguese
Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/FIS/04650/2020.
M. Mrlik gratefully acknowledges the support of the Ministry of Education, Youth and Sports of the Czech
Republic-DKRVO (RP/CPS/2020/003
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The Convergence of Parametric Resonance and Vibration Energy Harvesting
Energy harvesting is an emerging technology that derives electricity from the ambient environment in a decentralised and self-contained fashion. Applications include self-powered medical implants, wearable electronics and wireless sensors for structural health monitoring. Amongst the vast options of ambient sources, vibration energy harvesting (VEH) has attracted by far the most
research attention. Two of the key persisting issues of VEH are the limited power density compared to conventional power supplies and confined operational frequency bandwidth in light of the random, broadband and fast-varying nature of real vibration.
The convention has relied on directly excited resonance to maximise the mechanical-to-electrical energy conversion efficiency. This thesis takes a fundamentally different approach by employing parametric resonance, which, unlike the former, its resonant amplitude growth does not saturate due to linear damping. Therefore, parametric resonance, when activated, has the potential to accumulate much more energy than direct resonance. The vibrational nonlinearities that are almost always associated with parametric resonance can offer a modest frequency widening.
Despite its promising theoretical potentials, there is an intrinsic damping dependent initiation threshold amplitude, which must be attained prior to its onset. The relatively low amplitude of real vibration and the unavoidable presence of electrical damping to extract the energy render the onset of parametric resonance practically elusive. Design approaches have been devised to passively
minimise this initiation threshold.
Simulation and experimental results of various design iterations have demonstrated favourable results for parametric resonance as well as the various threshold-reduction mechanisms. For instance, one of the macro-scale electromagnetic prototypes (âŒ1800 cm3) when parametrically driven, has demonstrated around 50% increase in half power band and an order of magnitude higher peak power (171.5 mW at 0.57 msâ2) in contrast to the same prototype directly driven at fundamental resonance (27.75 mW at 0.65 msâ2). A MEMS (micro-electromechanical system) prototype with the additional threshold-reduction design needed 1 msâ2 excitation to activate parametric resonance while a comparable device without the threshold-reduction mechanism required in excess of 30 msâ2. One of the macro-scale piezoelectric prototypes operated into auto-parametric resonance has demon-strated notable further reduction to the initiation threshold. A vacuum packaged MEMS prototype demonstrated broadening of the frequency bandwidth along with higher power peak (324 nW and 160 Hz) for the parametric regime compared to when operated in room pressure (166 nW and 80 Hz), unlike the higher but narrower direct resonant peak (60.9 nW and 11 Hz in vacuum and 20.8
nW and 40 Hz in room pressure).
The simultaneous incorporation of direct resonance and bi-stability have been investigated to realise multi-regime VEH. The potential to integrate parametric resonance in the electrical domains have also been numerically explored. The ultimate aim is not to replace direct resonance but rather for the various resonant phenomena to complement each other and together harness a larger region of the available power spectrum
Development of MEMS Piezoelectric Vibration Energy Harvesters with Wafer-Level Integrated Tungsten Proof-Mass for Ultra Low Power Autonomous Wireless Sensors
La gĂ©nĂ©ration dâĂ©nergie localisĂ©e et Ă petite Ă©chelle, par transformation de lâĂ©nergie vibratoire disponible dans lâenvironnement, est une solution attrayante pour amĂ©liorer lâautonomie de certains noeuds de capteurs sans-fil pour lâInternet des objets (IoT). GrĂące Ă des microdispositifs inertiels rĂ©sonants piĂ©zoĂ©lectriques, il est possible de transformer lâĂ©nergie mĂ©canique en Ă©lectricitĂ©. Cette thĂšse prĂ©sente une Ă©tude exhaustive de cette technologie et propose un procĂ©dĂ© pour fabriquer des microgĂ©nĂ©rateurs MEMS offrant des performances surpassant lâĂ©tat de lâart.
On prĂ©sente dâabord une revue complĂšte des limites physiques et technologiques pour identifier le meilleur chemin dâamĂ©lioration. En Ă©valuant les approches proposĂ©es dans la littĂ©rature (gĂ©omĂ©trie, architecture, matĂ©riaux, circuits, etc.), nous suggĂ©rons des mĂ©triques pour comparer lâĂ©tat de lâart. Ces analyses dĂ©montrent que la limite fondamentale est lâĂ©nergie absorbĂ©e par le dispositif, car plusieurs des solutions existantes rĂ©pondent dĂ©jĂ aux autres limites. Pour un gĂ©nĂ©rateur linĂ©aire rĂ©sonant, lâabsorption dâĂ©nergie dĂ©pend donc des vibrations disponibles, mais aussi de la masse du dispositif et de son facteur de qualitĂ©.
Pour orienter la conception de prototypes, nous avons rĂ©alisĂ© une Ă©tude sur le potentiel des capteurs autonomes dans une automobile. Nous avons Ă©valuĂ© une liste des capteurs prĂ©sents sur un vĂ©hicule pour leur compatibilitĂ© avec cette technologie. Nos mesures de vibrations sur un vĂ©hicule en marche aux emplacements retenus rĂ©vĂšlent que lâĂ©nergie disponible pour un dispositif linĂ©aire rĂ©sonant MEMS se situe entre 30 Ă 150 Hz. Celui-ci pourrait produire autour de 1 Ă 10 ÎŒW par gramme. Pour limiter la taille dâun gĂ©nĂ©rateur MEMS pouvant produire 10 ÎŒW, il faut une densitĂ© supĂ©rieure Ă celle du silicium, ce qui motive lâintĂ©gration du tungstĂšne.
Lâeffet du tungstĂšne sur la sensibilitĂ© du dispositif est Ă©vident, mais nous dĂ©montrons Ă©galement que lâusage de ce matĂ©riau permet de rĂ©duire lâimpact de lâamortissement fluidique sur le facteur de qualitĂ© mĂ©canique Qm. En fait, lorsque lâamortissement fluidique domine, ce changement peut amĂ©liorer Qm dâun ordre de grandeur, passant de 103 Ă 104 dans lâair ambiant. Par consĂ©quent, le rendement du dispositif est amĂ©liorĂ© sans utiliser un boĂźtier sous vide.
Nous proposons ensuite un procĂ©dĂ© de fabrication qui intĂšgre au niveau de la tranche des masses de tungstĂšne de 500 ÎŒm dâĂ©pais. Ce procĂ©dĂ© utilise des approches de collage de tranches et de gravure humide du mĂ©tal en deux Ă©tapes. Nous prĂ©sentons chaque bloc de fabrication rĂ©alisĂ© pour dĂ©montrer la faisabilitĂ© du procĂ©dĂ©, lequel a permis de fabriquer plusieurs prototypes. Ces dispositifs ont Ă©tĂ© testĂ©s en laboratoire, certains dĂ©montrant des performances records en terme de densitĂ© de puissance normalisĂ©e. Notre meilleur design se dĂ©marque par une mĂ©trique de 2.5 mW-s-1/(mm3(m/s2)2), soit le meilleur rĂ©sultat rĂ©pertoriĂ© dans lâĂ©tat de lâart. Avec un volume de 3.5 mm3, il opĂšre Ă 552.7 Hz et produit 2.7 ÎŒW Ă 1.6 V RMS Ă partir dâune accĂ©lĂ©ration de 1 m/s2. Ces rĂ©sultats dĂ©montrent que lâintĂ©gration du tungstĂšne dans les microgĂ©nĂ©rateurs MEMS est trĂšs avantageuse et permet de sâapprocher davantage des requis des applications rĂ©elles.Small scale and localized power generation, using vibration energy harvesting, is considered as an attractive solution to enhance the autonomy of some wireless sensor nodes used in the Internet of Things (IoT). Conversion of the ambient mechanical energy into electricity is most often done through inertial resonant piezoelectric microdevices. This thesis presents an extensive study of this technology and proposes a process to fabricate MEMS microgenerators with record performances compared to the state of the art. We first present a complete review of the physical and technological limits of this technology to asses the best path of improvement. Reported approaches (geometries, architectures, materials, circuits) are evaluated and figures of merit are proposed to compare the state of the art. These analyses show that the fundamental limit is the absorbed energy, as most proposals to date partially address the other limits. The absorbed energy depends on the level of vibrations available, but also on the mass of the device and its quality factor for a linear resonant generator. To guide design of prototypes, we conducted a study on the potential of autonomous sensors in vehicles. A survey of sensors present on a car was realized to estimate their compatibility with energy harvesting technologies. Vibration measurements done on a running vehicle at relevant locations showed that the energy available for MEMS devices is mostly located in a frequency range of 30 to 150 Hz and could generate power in the range of 1-10 ÎŒW per gram from a linear resonator. To limit the size of a MEMS generator capable of producing 10 ÎŒW, a higher mass density compared to silicon is needed, which motivates the development of a process that incorporates tungsten. Although the effect of tungsten on the device sensitivity is well known, we also demonstrate that it reduces the impact of the fluidic damping on the mechanical quality factor Qm. If fluidic damping is dominant, switching to tungsten can improve Qm by an order of magnitude, going from 103 to 104 in ambient air. As a result, the device efficiency is improved despite the lack of a vacuum package. We then propose a fabrication process flow to integrate 500 ÎŒm thick tungsten masses at the wafer level. This process combines wafer bonding with a 2-step wet metal etching approach. We present each of the fabrication nodes realized to demonstrate the feasibility of the process, which led to the fabrication of several prototypes. These devices are tested in the lab, with some designs demonstrating record breaking performances in term of normalized power density. Our best design is noteworthy for its figure of merit that is around 2.5 mW-s-1/(mm3(m/s2)2), which is the best reported in the state of the art. With a volume of 3.5 mm3, it operates at 552.7 Hz and produces 2.7 ÎŒW at 1.6 V RMS from an acceleration of 1 m/s2. These results therefore show that tungsten integration in MEMS microgenerators is very advantageous, allowing to reduce the gap with needs of current applications
Wideband Micro-Power Generators for Vibration Energy Harvesting
Energy harvesters collect and convert energy available in the environment into
useful electrical power to satisfy the power requirements of autonomous systems.
Vibration energy is a prevalent source of waste energy in industrial and built environments.
Vibration-based energy harvesters, or vibration-based micro power
generators (VBMPGs), utilize a transducer, a mechanical oscillator in this application,
to capture kinetic energy from environmental vibrations and to convert it into
electrical energy using electromagnetic, electrostatic, or piezoelectric transduction
mechanisms.
A key design feature of all VBMPGs, regardless of their transduction mechanism,
is that they are optimally tuned to harvest vibration energy within a narrow
frequency band in the neighborhood of the natural frequency of the oscillator. Outside
this band, the output power is too low to be conditioned and utilized. This
limitation is exacerbated by the fact that VBMPGs are also designed to have high
quality factors to minimize energy dissipation, further narrowing the optimal operating
frequency band. Vibrations in most environments, however, are random and
wideband. As a result, VBMPGs can harvest energy only for a relatively limited
period of time, which imposes excessive constraints on their usability.
A new architecture for wideband VBMPGs is the main contribution of this
thesis. The new design is general in the sense that it can be applied to any of the
three transduction mechanisms listed above. The linear oscillator is replaced with
a piecewise-linear oscillator as the energy-harvesting element of the VBMPG. The
new architecture has been found to increase the bandwidth of the VBMPG during
a frequency up-sweep, while maintaining the same bandwidth in a frequency downsweep.
Experimental results show that using the new architecture results in a 313%
increase in the width of the bandwidth compared to that produced by traditional
architecture. Simulations show that under random-frequency excitations, the new
architecture collects more energy than traditional architecture.
In addition, the knowledge acquired has been used to build a wideband electromagnetic
VBMPG using MicroElectroMechanical Systems, MEMS, technology.
This research indicates that a variety of piecewise-linear oscillators, including impact
oscillators, can be implemented on MPG structures that have been built using
MEMS technology. When the scale of the MPGs is reduced, lower losses are likely
during contact between the moving oscillators and the stopper, which will lead to
an increase in bandwidth and hence in the amount of energy collected.
Finally, a design procedure has been developed for optimizing such wideband
MPGs. This research showed that wideband MPGs require two design optimization
steps in addition to the traditional technique, which is used in all types of
generators, of minimizing mechanical energy losses through structural design and
material selection. The first step for both regular and wideband MPGs minimizes
the MPG damping ratio by increasing the mass and stiffness of the MPG by a common
factor until the effect of size causes the rate at which energy losses increase
to accelerate beyond that common factor. The second step, which is specific to
wideband MPGs, tailors the output power and bandwidth to fit the Probability
Density Function, PDF, of environmental vibrations. A figure of merit FoM was
devised to quantify the quality of this fit. Experimental results show that with this
procedure, the bandwidth at half-power level increases to more than 600% of the
original VBMPG bandwidth
Urubu: energy scavenging in wireless sensor networks
For the past years wireless sensor networks (WSNs) have been coined as one of the most
promising technologies for supporting a wide range of applications. However, outside the
research community, few are the people who know what they are and what they can offer.
Even fewer are the ones that have seen these networks used in real world applications. The
main obstacle for the proliferation of these networks is energy, or the lack of it. Even
though renewable energy sources are always present in the networks environment,
designing devices that can efficiently scavenge that energy in order to sustain the operation
of these networks is still an open challenge.
Energy scavenging, along with energy efficiency and energy conservation, are the current
available means to sustain the operation of these networks, and can all be framed within
the broader concept of âEnergetic Sustainabilityâ. A comprehensive study of the several
issues related to the energetic sustainability of WSNs is presented in this thesis, with a
special focus in todayâs applicable energy harvesting techniques and devices, and in the
energy consumption of commercially available WSN hardware platforms.
This work allows the understanding of the different energy concepts involving WSNs and
the evaluation of the presented energy harvesting techniques for sustaining wireless sensor
nodes. This survey is supported by a novel experimental analysis of the energy
consumption of the most widespread commercially available WSN hardware platforms.HĂĄ jĂĄ alguns anos que as redes de sensores sem fios (do InglĂȘs Wireless Sensor Networks -
WSNs) tĂȘm sido apontadas como uma das mais promissoras tecnologias de suporte a uma
vasta gama de aplicaçÔes. No entanto, fora da comunidade cientĂfica, poucas sĂŁo as
pessoas que sabem o que elas sĂŁo e o que tĂȘm para oferecer. Ainda menos sĂŁo aquelas que
jå viram a sua utilização em aplicaçÔes do dia-a-dia. O principal obståculo para a
proliferação destas redes Ă© a energia, ou a falta dela. Apesar da existĂȘncia de fontes de
energia renovåveis no local de operação destas redes, continua a ser um desafio construir
dispositivos capazes de aproveitar eficientemente essa energia para suportar a operação
permanente das mesmas.
A colheita de energia juntamente com a eficiĂȘncia energĂ©tica e a conservação de energia,
sĂŁo os meios disponĂveis actualmente que permitem a operação permanente destas redes e
podem ser todos englobados no conceito mais amplo de âSustentabilidade EnergĂ©ticaâ.
Esta tese apresenta um estudo extensivo das vårias questÔes relacionadas com a
sustentabilidade energética das redes de sensores sem fios, com especial foco nas
tecnologias e dispositivos explorados actualmente na colheita de energia e no consumo
energético de algumas plataformas comercias de redes de sensores sem fios.
Este trabalho permite compreender os diferentes conceitos energéticos relacionados com as
redes de sensores sem fios e avaliar a capacidade das tecnologias apresentadas em suportar
a operação permanente das redes sem fios. Este estudo é suportado por uma inovadora
anålise experimental do consumo energético de algumas das mais difundidas plataformas
comerciais de redes de sensores sem fios
Human movement energy harvesting : a non-linear electromagnetic approach
Energy harvesting is one of the methods that currently engage actively in energy ârecyclingâ. Of the many energy sources that carry the potential to have energy harvested and recycled, humans are seen as a potential source of energy. High amounts of energy are wasted from daily activities that humans do, if only a portion of the wasted energy can be harvested and reused with the aim of improving the quality of life of the user.To do that, the accelerations of selected movements are recorded from sensors attached to four different locations of the body. Human movements operate on a low and wide frequency scale, nonlinear energy harvesting techniques is seen as a suitable technique to be applied. Nonlinear energy harvesting techniques are expected to increase the bandwidth of operation of the energy harvester. The electromagnetic method of transduction is also selected (using two opposing magnets) to be paired with the nonlinear energy harvesting techniques to evaluate the potential of energy harvesting from human movements. The pick-up coil to be used will be placed at a novel location within the energy harvester prototype.Through simulations and experiments, frequency responses obtained did show an increase in bandwidth which agrees with literature from nonlinear energy harvesting techniques. Phase portraits are also used to provide a more in depth understanding on the movements from the cantilever under linear and nonlinear dynamics. Result comparisons were made between the simulation model and the experimental prototype to verify the agreement between the two.Additionally, results obtained also showed that the resonant frequency of the system was reduced when operating under the nonlinear regime. These attribute favour energy harvesting though human movements.Finally, the novel placement of the pick-up coil within the nonlinear electromagnetic energy harvester had the desired effect. Similar power outputs were achieved even though the separation distances between the two opposing magnets were varied