Дисертації: "ENERGY HARVESTING APPLICATIONS"

1

Martin, Benjamin Ryan. "Energy Harvesting Applications of Ionic Polymers." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/32024.

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The purpose of this thesis is the development and analysis of applications for ionic polymers as energy harvesting devices. The specific need is a self-contained energy harvester to supply renewable power harvested from ambient vibrations to a wireless sensor. Ionic polymers were investigated as mechanical to electrical energy transducers. An ionic polymer device was designed to harvest energy from vibrations and supply power for a wireless structural health monitoring sensor.The ionic polymer energy harvester is tested to ascertain whether the idea is feasible. Transfer functions are constructed for both the open-circuit voltage and the closed-circuit current. The impedance of the device is also quantified. Using the voltage transfer function and the current transfer function it is possible to calculate the power being produced by the device.Power generation is not the only energy harvesting application of ionic polymers, energy storage is another possibility. The ionic polymer device is tested to characterize its charge and discharge capabilities. It is charged with both DC and AC currents. An energy storage comparison is performed between the ionic polymers and capacitors. While the polymers performed well, the electrolytic capacitors are able to store more energy. However, the ionic polymers show potential as capacitors and have the possibility of improved performance as energy storage devices. Current is measured across resistive loads and the supplied power is calculated. Although the power is small, the ionic polymers are able to discharge energy across a load proving that they are capable of supplying power.
Master of Science

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2

Ersoy, Kurtulus. "Piezoelectric Energy Harvesting For Munitions Applications." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613589/index.pdf.

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In recent years, vibration-based energy harvesting technologies have gained great importance because of reduced power requirement of small electronic components. External power source and maintenance requirement can be minimized by employment of mechanical vibration energy harvesters. Power sources that harvest energy from the environment have the main advantages of high safety, long shell life and low cost compared to chemical batteries. Electromagnetic, electrostatic and piezoelectric transduction mechanisms are the three main energy harvesting methods. In this thesis, it is aimed to apply the piezoelectric elements technology to develop means for energy storage in munitions launch. The practical problems encountered in the design of piezoelectric energy harvesters are investigated. The applicability of energy harvesting to high power needs are studied. The experience compiled in the study is to be exploited in designing piezoelectric energy harvesters for munitions applications. Piezoelectric energy harvesters for harmonic and mechanical shock loading conditions with different types of piezoelectric materials are designed and tested. The test results are compared with both responses from analytical models generated in MATLAB®
and ORCAD PSPICE®
, and finite element method models generated in ATILA®
. Optimum energy storage methods are considered.

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3

Sze, Ngok Man. "Switching converter techniques for energy harvesting applications /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20SZE.

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4

Oliva, Alexander. "Multi-source energy harvesting for lightweight applications." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119580.

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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 193-197).
This thesis analyzes, designs and tests circuit topologies for simultaneous energy harvesting from solar and 915-MHz RF energy sources. An important design objective is to minimize system weight while maximizing output power and operating time for applications in the sub-170-mg and single-mW ranges. The resulting energy harvesting system uses a unique approach of categorizing the harvesters as primary and auxiliary harvesters due to the power levels of each in relation to the high load demand. This work results in a 162-mg supercapacitor-powered system capable of powering a 2-V load at up to approximately 2-3 mW and a 150-mg battery-powered system capable of powering a 2-V load at up to 6 mW. The auxiliary RF harvester uses a fully-integrated charge pump to impedance-match to a rectenna with greater than 94% matching. The parasitic models developed for the RF harvester show errors less than 1.4% in the measured system.
by Alexander Oliva.
M. Eng.

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5

Smilek, Jan. "Energy Harvesting Power Supply for MEMS Applications." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-386765.

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Tato práce se zabývá vývojem nezávislého elektrického zdroje pro moderní nízkopříkonové elektrické aplikace. Protože tradiční řešení napájení drobných spotřebičů s využitím baterií či akumulátorů snižuje uživatelský komfort kvůli potřebě pravidelné údržby, navrhovaný zdroj využívá principu energy harvesting. Tento princip spočívá v získávání energie přímo z okolního prostředí napájené aplikace a její přeměně na energii elektrickou, která je dále využita pro na-pájení moderních MEMS (mikroelektromechanických) zařízení. Potenciální aplikací vyvíjeného zdroje je především moderní nositelná elektronika a biomedicínské senzory. Tato oblast využití ovšem klade zvýšené nároky na parametry generátoru, který musí zajistit dostatečný generovaný výkon z energie, dostupné v okolí lidského těla, a to při zachování prakticky využitelné velikosti a hmotnosti. Po stanovení předběžných požadavků a provedení analýz vhodnosti dostupných zdrojů energie ke konverzi byla k využití vybrána kinetická energie lidských aktivit. Byla provedena série měření zrychlení na lidském těle, především v místě předpokládaného umístění generátoru, aby bylo možno analyzovat a generalizovat hodnoty energie dostupné ke konverzi v daném umístění. V návaznosti na tato měření a analýzy byl vyvinut inovativní kinetický energy harvester, který byl následně vyroben jako funkční vzorek. Tento vzorek byl pak testován v reálných podmínkách pro verifikaci simulačního modelu a vyhodnocení reálné použitelnosti takového zařízení. Kromě samotného vývoje generátoru je v práci popsán i originální způsob zvýšení generovaného výkonu pro kinetické energy harvestery a jsou prezentována statistická data a modely pro predikci využitelnosti kinetických harvesterů pro získávání energie z lidské aktivity.

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6

Wang, X., S. Dong, Ashraf F. Ashour, and B. Han. "Energy-harvesting concrete for smart and sustainable infrastructures." A Springer Nature Publication, 2021. http://hdl.handle.net/10454/18553.

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Yes
Concrete with smart and functional properties (e.g., self-sensing, self-healing, and energy-harvesting) represents a transformative direction in the field of construction materials. Energy-harvesting concrete has the capability to store or convert the ambient energy (e.g., light, thermal, and mechanical energy) for feasible uses, alleviating global energy and pollution problems as well as reducing carbon footprint. The employment of energy-harvesting concrete can endow infrastructures (e.g., buildings, railways, and highways) with energy self-sufficiency, effectively promoting sustainable infrastructure development. This paper provides a systematic overview on the principles, fabrication, properties, and applications of energy-harvesting concrete (including light-emitting, thermal-storing, thermoelectric, pyroelectric, and piezoelectric concretes). The paper concludes with an outline of some future challenges and opportunities in the application of energy-harvesting concrete in sustainable infrastructures.
The full-text of this article will be released for public view at the end of the publisher embargo on 19 Jul 2022.

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7

Constantinou, Peter. "A magnetically sprung generator for energy harvesting applications." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508049.

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8

Simone, Dominic J. "Modeling a linear generator for energy harvesting applications." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/44669.

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Approved for public release; distribution is unlimited
The intent of this research is to draw attention to linear generators and their potential uses. A flexible model of a linear generator created in MATLAB Simulink is presented. The model is a three-phase, 12-pole, non-salient, synchronous permanent magnet linear generator with a non-sinusoidal back electromotive force (EMF) but could easily be adapted to fit any number of poles or any back EMF waveform. The emerging technologies related to linear generators such as wave energy converters and free-piston engines are explained. A selection of these technologies is generically modeled and their results are discussed and contrasted against one another. The model clearly demonstrates the challenges of using linear generators in different scenarios. It also proves itself a useful tool in analyzing and improving the performance of linear generators under a variety of circumstances.

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9

Choi, Yeonsik. "Novel functional polymeric nanomaterials for energy harvesting applications." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/282877.

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Polymer-based piezoelectric and triboelectric generators form the basis of well-known energy harvesting methods that are capable of transforming ambient vibrational energy into electrical energy via electrical polarization changes in a material and contact electrification, respectively. However, the low energy conversion efficiency and limited thermal stability of polymeric materials hinder practical application. While nanostructured polymers and polymer-based nanocomposites have been widely studied to overcome these limitations, the performance improvement has not been satisfactory due to limitations pertaining to long-standing problems associated with polymeric materials; such as low crystallinity of nanostructured polymers, and in the case of nanocomposites, poor dispersion and distribution of nanoparticles in the polymer matrix. In this thesis, novel functional polymeric nanomaterials, for stable and physically robust energy harvesting applications, are proposed by developing advanced nanofabrication methods. The focus is on ferroelectric polymeric nanomaterials, as this class of materials is particularly well-suited for both piezoelectric and triboelectric energy harvesting. The thesis is broadly divided into two parts. The first part focuses on Nylon-11 nanowires grown by a template-wetting method. Nylon-11 was chosen due to its reasonably good ferroelectric properties and high thermal stability, relative to more commonly studied ferroelectric polymers such as polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)). However, limitations in thin-film fabrication of Nylon-11 have led to poor control over crystallinity, and thus investigation of this material for practical applications had been mostly discontinued, and its energy harvesting potential never fully realised. The work in this thesis shows that these problems can be overcome by adopting nanoporous template-wetting as a versatile tool to grow Nylon-11 nanowires with controlled crystallinity. Since the template-grown Nylon-11 nanowires exhibit a polarisation without any additional electrical poling process by exploiting the nanoconfinement effect, they have been directly incorporated into nano-piezoelectric generators, exhibiting high temperature stability and excellent fatigue performance. To further enhance the energy harvesting capability of Nylon-11 nanowires, a gas -flow assisted nano-template (GANT) infiltration method has been developed, whereby rapid crystallisation induced by gas-flow leads to the formation of the ferroelectric δʹ-phase. The well-defined crystallisation conditions resulting from the GANT method not only lead to self-polarization but also increases average crystallinity from 29 % to 38 %. δʹ-phase Nylon-11 nanowires introduced into a prototype triboelectric generator are shown to give rise to a six-fold increase in output power density as observed relative to the δʹ-phase film-based device. Interestingly, based on the accumulated understanding of the template-wetting method, Nylon-11, and energy harvesting devices, it was found that thermodynamically stable α-phase Nylon-11 nanowires are most suitable for triboelectric energy generators, but not piezoelectric generators. Notably, definitive dipole alignment of α-phase nanowires is shown to have been achieved for the first time via a novel thermally assisted nano-template infiltration (TANI) method, resulting in exceptionally strong and thermally stable spontaneous polarization, as confirmed by molecular structure simulations. The output power density of a triboelectric generator based on α-phase nanowires is shown to be enhanced by 328 % compared to a δʹ-phase nanowire-based device under the same mechanical excitation. The second part of the thesis presents recent progress on polymer-based multi-layered nanocomposites for energy harvesting applications. To solve the existing issues related to poor dispersion and distribution of nanoparticles in the polymer matrix, a dual aerosol-jet printing method has been developed and applied. As a result, outstanding dispersion and distribution. Furthermore, this method allows precise control of the various physical properties of interest, including the dielectric permittivity. The resulting nanocomposite contributes to an overall enhancement of the device capacitance, which also leads to high-performance triboelectric generators. This thesis therefore presents advances in novel functional polymeric nanomaterials for energy harvesting applications, with improved performance and thermal stability. It further offers insight regarding the long-standing issues in the field of Nylon-11, template-wetting, and polymer-based nanocomposites.

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10

Thompson, Nicholas John. "Singlet exciton fission : applications to solar energy harvesting." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89959.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 141-147).
Singlet exciton fission transforms a single molecular excited state into two excited states of half the energy. When used in solar cells it can double the photocurrent from high energy photons increasing the maximum theoretical power efficiency to greater than 40%. The steady state singlet fission rate can be perturbed under an external magnetic field. I utilize this effect to monitor the yield of singlet fission within operating solar cells. Singlet fission approaches unity efficiency in the organic semiconductor pentacene for layers more than 5 nm thick. Using organic solar cells as a model system for extracting photocurrent from singlet fission, I exceed the convention limit of 1 electron per photon, realizing 1.26 electrons per incident photon. One device architecture proposed for high power efficiency singlet fission solar cells coats a conventional inorganic semiconducting solar with a singlet fission molecule. This design requires energy transfer from the non-emissive triplet exciton to the semiconducting material, a process which has not been demonstrated. I prove that colloidal nanocrystals accept triplet excitons from the singlet fission molecule tetracene. This enables future devices where the combine singlet fission material and nanocrystal system energy transfer triplet excitons produced by singlet fission to a silicon solar cell.
by Nicholas J. Thompson.
Ph. D.

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11

Abeywickrama, Thulitha Madawa. "Metal-Organic Hybrid Nanocomposites For Energy Harvesting Applications." TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1748.

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Various synthetic methods have been developed to produce metal nanostructures including copper and iron nanostructures. Modification of nanoparticle surface to enhance their characteristic properties through surface functionalization with organic ligands ranging from small molecules to polymeric materials including organic semiconducting polymers is a key interest in nanoscience. However, most of the synthetic methods developed in the past depend widely on non-aqueous solvents, toxic reducing agents, and high temperature and high-pressure conditions. Therefore, to produce metal nanostructures and their nanocomposites with a simpler and greener method is indeed necessary and desirable for their nano-scale applications. Hence the objective of this thesis work is to develop an environmentally friendly synthesis method to make welldefined copper and iron nanostructures on a large-scale. The size and shape-dependent optical properties, solid-state crystal packing, and morphologies of nanostructures have been evaluated with respect to various experimental parameters. Nanostructures of copper and iron were prepared by developing an aqueous phase chemical reduction method from copper(II) chloride and Fe(III) chloride hexahydrate upon reduction using a mild reducing agent, sodium borohydride, under an inert atmosphere at room temperature. Well-defined copper nanocubes with an average edge length of 100±35 nm and iron nanochains with an average chain length up to 1.70 μm were prepared. The effect of the molar ratios of each precursor to the reducing agent, reaction time, and addition rate of the reducing agent were also evaluated in order to develop an optimized synthesis method for synthesis of these nanostructures. UV-visible spectral traces and X-ray powder diffraction traces were obtained to confirm the successful preparation of both nanostructrues. The synthesis method developed here was further modified to make poly(3-hexylthiophene) coated iron nanocomposites by surface functionalization with poly(3-hexylthiophene) carboxylate anion. Since these nanostructrues and nanocomposites have the ability to disperse in both aqueous-based solvents and organic solvents, the synthesis method provides opportunities to apply these metal nanostructures on a variety of surfaces using solution based fabrication techniques such as spin coating and spray coating methods.

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12

Thomas, Michael Brandon. "Donor-Acceptor Systems: Photochemistry and Energy Harvesting Applications." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703335/.

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Donor-acceptor systems have unique properties that make them ideal candidates for solar energy harvesting through mimicry of natural photosynthesis. This dissertation is focused on unraveling those unique properties in various types of donor-acceptor systems. The systems investigated are categorized as closely linked, push-pull, supramolecular, and multi-unit. As part of the study, photosynthetic analogues based on BF2-chelated dipyrromethene (BODIPY), porphyrin, phthalocyanine, truxene, ferrocene, quinone, phenothiazine (PTZ), perylenediimide (PDI), fullerene (C60), dicyanoquinodimethane (DCNQ), tetracyanobutadiene (TCBD), and triphenylamine (TPA) are investigated. The effects of proximity between donor-acceptor entities, their geometrical orientation relative to each other, push-pull character of substituents, and competitive energy and electron transfer are examined. In all systems, primary events of photosynthesis are observed, that is absorption and energy transfer and/or electron transfer is witnessed. Ultrafast transient absorption spectroscopy is utilized to characterize the photo-induced events, while other methods such as steady-state luminescence, cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and computational calculations are used to aid in the characterization of the donor-acceptor systems, in particular their applicability as solar energy harvesters.

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13

Olgun, Ugur. "Efficient Microwave Energy Harvesting Technology and its Applications." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1348776239.

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14

Chen, Zhi Yuan. "Efficient power management design for energy harvesting biomedical applications." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3952096.

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15

Nagode, Clement Michel Jean. "Electromechanical Suspension-based Energy Harvesting Systems for Railroad Applications." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50611.

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Currently, in the railroad industry, the lack of electrical sources in freight cars is a problem that has yet to find practical solutions. Although the locomotive generates electricity to power the traction motors and all the equipment required to operate the train, the electrical power cannot, in a practical manner, be carried out along the length of the train, leaving freight cars unpowered. While this has not been a major issue in the past, there is a strong interest in equipping modern cars with a myriad of devices intended to improve safety, operational efficiency, or health monitoring, using devices such as GPS, active RFID tags, and accelerometers. The implementation of such devices, however, is hindered by the unavailability of electricity. Although ideas such as Timken\'s generator roller bearing or solar panels exist, the railroads have been slow in adopting them for different reasons, including cost, difficulty of implementation, or limited capabilities.

The focus of this research is on the development of vibration-based electromechanical energy harvesting systems that would provide electrical power in a freight car. With size and shape similar to conventional shock absorbers, these devices are designed to be placed in parallel with the suspension elements, possibly inside the coil spring, thereby maximizing unutilized space. When the train is in motion, the suspension will accommodate the imperfections of the track, and its relative velocity is used as the input for the harvester, which converts the mechanical energy to useful electrical energy.

Beyond developing energy harvesters for freight railcar primary suspensions, this study explores track wayside and miniature systems that can be deployed for applications other than railcars. The trackside systems can be used in places where electrical energy is not readily available, but where, however, there is a need for it. The miniature systems are useful for applications such as bicycle energy.

Beyond the design and development of the harvesters, an extensive amount of laboratory testing was conducted to evaluate both the amount of electrical power that can be obtained and the reliability of the components when subjected to repeated vibration cycles. Laboratory tests, totaling more than two million cycles, proved that all the components of the harvester can satisfactorily survive the conditions to which they are subjected in the field. The test results also indicate that the harvesters are capable of generating up to 50 Watts at 22 Vrms, using a 10-Ohm resistor with sine wave inputs, and over 30 Watts at peak with replicated suspension displacements, making them suitable to directly power onboard instruments or to trickle charge a battery.

Ph. D.

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16

Roscow, James. "Composite ferroelectric materials for energy harvesting and storage applications." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761037.

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In this study composite ferroelectric materials have been investigated for their ability to harvest energy from mechanical vibrations via the piezoelectric effect, and store electrical energy as capacitor materials. A combination of modelling and experimental techniques have been used to understand the consequences of using multiphase materials for energy harvesting and storage applications, with particular focus on the significance of interactions between composite structure, electric field distributions and the effective material properties. A detailed investigation into the properties of ferroelectric ceramic-air composites, such as porous barium titanate, is presented. Introducing isotropic, randomly distributed porosity into barium titanate was found to increase the energy harvesting figure of merit from ~1.40 pm^2/N for the dense material to ~2.85 pm^2/N at 60 vol.% porosity. Finite element modelling was used to better understand the poling behaviour of barium titanate with different porous structures (uniform, porous sandwich layer and aligned), enabling the design of materials with improved energy harvesting capabilities. Complex porous structures were found to have enhanced energy harvesting figures of merit, with maximum values achieved of 3.74 pm^2/N and 3.79 pm^2/Nin barium titanate with a 60 vol.% porosity sandwich layer (overall porosity ~34 vol.%) and highly aligned freeze cast barium titanate with 45 vol.% porosity, respectively. Dense and porous barium titanate samples were mechanically excited and the derived electrical energy used to charge a capacitor. The porous barium titanate was found to charge the reference capacitor more effectively than the dense material, demonstrating the benefits of introducing porosity into ferroelectric materials for energy harvesting applications. Ferroelectric composites, in which either a conductive filler was added to a high permittivity ferroelectric matrix or a high permittivity ferroelectric phase was added to a low permittivity polymer matrix, were evaluated for their potential as a new generation of capacitor materials using finite element modelling. The studies suggested that the rise in effective permittivity due to the forming of composites is fundamentally linked to the rapid decline in dielectric breakdown strengths observed in composites, resulting in nearly all cases reported in the literature demonstrating a reduction in the energy storage figure of merit. It is concluded that future efforts into finding the next generation of energy storage materials should focus on single phase, or intrinsic, high permittivity materials rather than composite materials.

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17

Wang, Xiaoyu. "An Ambient Energy Harvesting System for Passive RFID Applications." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175154.

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Radio-frequency identification(RFID)is the wireless use of electromagnetic fields to transfer data, for the purpose of automatically identifying and tracking tags attached to objects. It is one of hot topics recently. The power supply is one of key factors restricting the lifetime and performance of RFID. The main focus is to power RFID system with clear power source. In this work, a harvester consisting of a matching network, a rectifier and a load is investigated. The operation of a Schottky diode based rectifier which is the core part inthe harvester is researched seriously. The Schottky diode based rectifier consistingof single-stage or multi-stage of voltage doublers is applied in radio frequency (RF) power harvesting.Analytical modeling of the equivalent circuits composedof a resistor and a capacitor. The resistor and the capacitor from the analytical modeling are applied in the simulation of impedance matching. The design trade-off among the stages of the voltage doubler, load of the harvester, the output voltage and the efficiency is discussed owing to the variation of input impedance with the input power. Moreover, a trade-off betweenthe load inthe harvester and the stages of the voltage doubler is stated based on the analysis of the simulation resultsby Advanced Design System (ADS)with the criteria that the output voltage is higher than 1V.Some conclusions about the harvester are obtained by the simulation and analysis. The sensitivity of the harvester is around -23dBm. Rectifiers with more stages have lower input impedance and lower speeds of variation in input impedance. Larger loading impedance in the harvester leads to higher output voltage but lower conversion efficiency. Four-stage voltage doubler and 5M ohm load should be chosen when the input power ranges from -23 to -20dBm. Two-stage voltage doubler with 500k ohm load is a better choice with input power between -20 and -15dBm. For input power from -15 to -5dBm, single-stage voltage doubler and 50k ohm are utilized. When the input power is larger than -5dBm, two-stage voltage doubler and 50k ohm should be chosen.

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18

Shen, Dongna Kim Dong Joo. "Piezoelectric energy harvesting devices for low frequency vibration applications." Auburn, Ala., 2009. http://hdl.handle.net/10415/1603.

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19

Carvalho, Carlos Manuel Ferreira. "CMOS indoor light energy harvesting system for wireless sensing applications." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2014. http://hdl.handle.net/10362/13127.

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Анотація:

Dissertação para obtenção do Grau de Doutor em Engenharia Electrotécnica e de Computadores
This research thesis presents a micro-power light energy harvesting system for indoor environments. Light energy is collected by amorphous silicon photovoltaic (a-Si:H PV) cells, processed by a switched-capacitor (SC) voltage doubler circuit with maximum power point tracking (MPPT), and finally stored in a large capacitor. The MPPT Fractional Open Circuit Voltage (VOC) technique is implemented by an asynchronous state machine (ASM) that creates and, dynamically, adjusts the clock frequency of the step-up SC circuit, matching the input impedance of the SC circuit to the maximum power point (MPP) condition of the PV cells. The ASM has a separate local power supply to make it robust against load variations. In order to reduce the area occupied by the SC circuit, while maintaining an acceptable efficiency value, the SC circuit uses MOSFET capacitors with a charge reusing scheme for the bottom plate parasitic capacitors. The circuit occupies an area of 0.31 mm2 in a 130 nm CMOS technology. The system was designed in order to work under realistic indoor light intensities. Experimental results show that the proposed system, using PV cells with an area of 14 cm2, is capable of starting-up from a 0 V condition, with an irradiance of only 0.32 W/m2. After starting-up, the system requires an irradiance of only 0.18 W/m2 (18 mW/cm2) to remain in operation. The ASM circuit can operate correctly using a local power supply voltage of 453 mV, dissipating only 0.085 mW. These values are, to the best of the authors’ knowledge, the lowest reported in the literature. The maximum efficiency of the SC converter is 70.3% for an input power of 48 mW, which is comparable with reported values from circuits operating at similar power levels.
Portuguese Foundation for Science and Technology (FCT/MCTES), under project PEst-OE/EEI/UI0066/2011, and to the CTS multiannual funding, through the PIDDAC Program funds. I am also very grateful for the grant SFRH/PROTEC/67683/2010, financially supported by the IPL – Instituto Politécnico de Lisboa.

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20

Hawes, David. "Nonlinear stochastic vibration analysis for energy harvesting and other applications." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/263016.

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With the rapid development of electronic technology, the power consumption of electronic devices has decreased significantly. Consequently, there is substantial interest in harvesting energy from ambient sources, such as vibration, in order to power small-scale wireless devices. To design optimal vibration harvesting systems it is important to determine the maximum power obtainable from a given vibration source. Initially, white noise base excitation of a general nonlinear energy harvester model is considered. The power input from white noise is known to be proportional both to the total oscillating mass of the system and the magnitude of the noise spectral density, regardless of the internal mechanics of the system. This power is split between undesirable mechanical damping and useful electrical dissipation, where the form of the stiffness profile and device parameters determine the relative proportion of energy dissipated by each mechanism. An upper bound on the electrical power is derived and used to guide towards optimal harvesting devices, revealing that low stiffness systems exhibit maximum performance. Many engineering applications will exhibit more complicated spectra than the flat spectrum of white noise. Expanding upon the white noise analysis, a method to investigate the power dissipation of nonlinear oscillators under non-white excitation is developed by extending the Wiener series. The relatively simple first term of the series, together with the excitation spectrum, is found to completely define the power dissipated. An important property of this first term, namely that the integral over its frequency domain representation is proportional to the oscillating mass, is derived and validated both numerically and experimentally, using a base excited cantilever beam with a nonlinear restoring force produced by magnets. Another form of excitation prevalent in many mechanical systems is a combination of deterministic and broadband random vibration. Lastly, the Duffing oscillator is used to illustrate the behaviour of a nonlinear system under this form of excitation, where the response is observed to spread around the attractor that would be seen if purely deterministic excitation was present. The ability of global weighted residual methods to produce the complex responses typical of nonlinear oscillators is assessed and found to be accurate for systems with weak nonlinearity.

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21

Chanyawadee, Soontorn. "Resonant energy transfer in light harvesting and light emitting applications." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72508/.

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The performance of light emitting and light harvesting devices is improved by utilising resonant energy transfer. In lighting applications, the emission energy of a semiconductor heterostructure and the absorption of organic dyes or colloidal quantum dots (QDs) are engineered so that the excitations in the semiconductor heterostructure can be transferred to the light emitters by means of resonant energy transfer. The emitters subsequently emit colour-tunable light ranging from the visible to the near-infrared. As a result, a twofold enhancement of QD emission is demonstrated in a hybrid QD/semiconductor heterostructure. In light harvesting applications, a hybrid structure of colloidal QDs and a quantum well (QW) p-i-n heterostructure is investigated. After highly absorbing QDs absorb photons, the excitations are efficiently transferred to a QW p-i-n heterostructure via resonant energy transfer. The generated electron-hole pairs in the heterostructure are subsequently separated by the built-in electric held and collected by the corresponding electrodes. In order to increase the energy transfer rate, the donor-acceptor separation distance is minimised by fabricating channel structures on the heterostructure surface penetrating its active layers. Consequently, a sixfold enhancement of photocurrent conversion efficiency is demonstrated. Photocurrent of the hybrid structure is further improved by replacing the QW heterostructure with a bulk p-i-n heterostructure which has higher carrier transport efficiency. Hence, the photocurrent of the hybrid bulk heterostructure is about two orders of magnitude higher than that of the hybrid QW heterostructure. The proposed hybrid structures offer efficient light harvesting devices where high absorption of the colloidal QDs is utilised and their low charge transfer is overcome.

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22

Osborne, Daniel Josiah. "A Nanoengineering Approach to Oxide Thermoelectrics For Energy Harvesting Applications." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/36133.

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The ability of uniquely functional thermoelectric materials to convert waste heat directly into electricity is critical considering the global energy economy. Profitable, energy-efficient thermoelectrics possess thermoelectric figures of merit ZT â ¥ 1. We examined the effect of metal nanoparticle â oxide film interfaces on the thermal conductivity Îº and Seebeck coefficient Î± in bilayer and multilayer thin film oxide thermoelectrics in an effort to improve the dimensionless figure of merit ZT. Since a thermoelectricâ s figure of merit ZT is inversely proportional to Îº and directly proportional to Î±, reducing Îº and increasing Î± are key strategies to optimize ZT. We aim to reduce Îº by phonon scattering due to the inclusion of metal nanoparticles in the bulk of thermoelectric thin films deposited by Pulsed Laser Deposition. XRD, AFM, XPS, and TEM analyses were carried out for structural and compositional characterization. The electrical conductivities of the samples were measured by a four-point probe apparatus. The Seebeck coefficients were measured in-plane, varying the temperature from 100K to 310K. The thermal conductivities were measured at room temperature using Time Domain Thermoreflectance.
Master of Science

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23

Shao, Hui. "System design and power management for ultra low energy applications using energy harvesting techniques /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?ECED%202009%20SHAO.

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24

McVay, Elaine D. "Large scale applications of 2D materials for sensing and energy harvesting." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111925.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references.
In this project we demonstrate the fabrication and characterization of printed reduced graphene oxide strain sensors, Chemical Vapor Deposition (CVD) 2D material transistors, and tungsten diselenide (WSe₂) photovoltaic devices that were produced through a combination of printing and conventional microfabrication processes. Each of these components were designed with the purpose of fitting into a "smart skin" system that could be discretely integrated into and sense its environment. This thesis document will describe the modification-of a 3D printer to give it inkjet capabilities that allow for the direct deposition of graphene oxide flakes onto a 3D printed surface. These graphene oxide flake traces were then reduced, making them more conductive and able to function as strain sensors. Next, this thesis will discuss the development of CVD molybdenum disulfide (MoS₂) and CVD graphene transistors and how they can be modified to function as chemical sensors. Finally, this work will detail steps taken to design, fabricate, and test a WSe₂ photovoltaic device which is composed of a printed active layer. In summary, these devices can fit into the sensing, communication, and energy harvesting blocks required in realizing a ubiquitous sensing system.
by Elaine D. McVay.
S.M.

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25

Zainal, Nurfarina. "Rapid melt growth of crystalline germanium for solar energy harvesting applications." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677964.

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Recent development of energy conversion devices namely photovoltaic (PV) cells or solar cells and thermophotovoltaic (TPV) cells require the use of bulk germanium as substrate material for efficient devices performance. Germanium is preferred to be employed in solidstate structure of terrestrial or space energy conversion devices due to its excellent electrical properties. With bandgap of 0.66 e V energy from infrared region of solar or thermal spectrum can be absorbed and converted into electrical energy. At present, multi-junction solar cells show the highest performance with bulk germanium as substrate material.' but have complicated and expensive manufacture processes. The major contributor to the high cells cost is the substrate material, germanium, which is an expensive and scarce material. One of the possibilities to resolve these issues is by using thin film instead of thick bulk germanium. To date, development of thin film germanium for energy conversion devices has not been established. By providing germanium on insulator structures a good quality thin film germanium can be attained and thus, offer a low cost route. The rapid melt growth (RMG) technique has been proposed, where it could potentially produces thin film germanium with quality similar to that of bulk germanium. In the existing technology via the RMG process germanium thickness was limited to 100 run. For photovoltaic applications thicker germanium films are required to have more energy absorption, thus leads to efficient performance.

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26

Abdelmoaty, Ahmed A. "Circuit and System Techniques for Energy-Harvesting Platforms for Mobile Applications." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1481832223757049.

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27

Cavalheiro, David. "Ultra-low power circuits based on tunnel FETs for energy harvesting applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/406391.

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There has been a tremendous evolution in integrated circuit technology in the past decades. With the scaling of complementary metal-oxide-semiconductor (CMOS) transistors, faster, less power consuming and more complex chips per unit area have made possible electronic gadgets to evolve to what we see today. The increasing demand in electronic portability imposes low power consumption as a key metric to analog and digital circuit design. While dynamic power consumption decreases quadratically with the decrease of power supply voltage, leakage power presents a limitation due to the inverse sub-threshold slope (SS). A power supply reduction implies a consequent threshold voltage reduction that, given the fixed SS, cause an exponential increase in leakage current. This poses a limitation in the reduction of power consumption that is inherent to the conventional thermionicbased transistors (MOSFETS and FinFETs). In thermionic-based transistors the SS at room temperature is limited to 60 mV/dec. To circumvent the SS limitation of conventional transistors, devices with different carrier injection mechanisms independent of the thermal (Boltzmann) distribution of mobile charge carriers are required. The Tunnel Field-Effect Transistor (TFET) is presented as the most promising post CMOS-technology due to its non-thermal carrier injection mechanism based on Band-To-Band Tunneling (BTBT) effect. TFETs are known as steep slope devices (SS < 60 mV/dec at room temperature). Large current gain (ION/IOFF > 105) at low voltage operation (sub-0.25 V) and extremely low leakage current have already been demonstrated, placing TFETs as serious candidates for ultra-low power and energy efficient circuit applications. TFETs have been explored mostly in digital circuits and applications. In this thesis, the use of TFETs is explored as an alternative technology also for ultra-low power and voltage conversion and management circuits, suited for weak energy harvesting (EH) sources. As TFETs are designed as reverse biased p-i-n diodes (different doping types in source/drain regions), the particular electrical characteristics under reverse bias conditions require changes in conventional circuit topologies. Rectifiers, charge pumps and power management circuits (PMC) are designed and analyzed with TFETs, evaluating their performance with the proposal of new topologies that extend the voltage/power range of operation compared to current technologies and circuit topologies. TFET-based PMCs for RF and DC EH sources are proposed and limitations (with solutions) of using TFETs in conventional inductor-based boost converters identified.
Ha habido una tremenda evolución en la tecnología de circuitos integrados en las últimas décadas. Con el escalado de transistores de metal-óxido-semiconductor (CMOS), se han hecho posibles chips más rápidos, con menos consumo de energía y más complejos con menos área y esto ha posibilitado la existencia de los aparatos electrónicos que vemos en la actualidad. La creciente demanda de portabilidad implica que el consumo de energía es un indicador clave en el diseño analógico y digital. Mientras que el consumo de potencia dinámica disminuye cuadráticamente con la disminución de la tensión de fuente de alimentación, la potencia de fugas presenta una limitación debido a la pendiente sub-umbral inverso (sub-threshold slope, SS). Una reducción de la tensión de alimentación implica una consecuente reducción de tensión umbral a fin de mantener las prestaciones que, dado el SS fijo, causa un aumento exponencial de la corriente de fuga. Esto plantea una limitación en la reducción de consumo de energía que es inherente a los transistores convencionales basados en inyección de portadores termoiónicos (MOSFETS y FinFETs). En transistores termoiónicos la SS a temperatura ambiente está limitado a 60 mV / dec. Para eludir la limitación SS de transistores convencionales se requieren dispositivos con mecanismos diferentes de inyección de portadores. El transistor túnel de efecto campo (TFET) se presenta como la tecnología más prometedora debido a su mecanismo de inyección de portadores no térmico basado en el efecto Band-To-Band Tunneling (BTBT). Los TFETs se conocen como dispositivos de alta pendiente sub-umbral (SS <60 mV / dec a temperatura ambiente). Han sido ya demostradas ganancias de corriente elevadas (ION / IOFF> 10 ^ 5) en operación de baja tensión (sub-0,25 V) y una corriente de fugas extremadamente bajo, colocando los TFETs como serios candidatos para aplicaciones de circuitos eficientes de ultra-baja potencia y energía. Los TFETs se han explorado sobre todo en circuitos digitales y aplicaciones. En esta tesis, el uso de TFETs se explora como una tecnología alternativa también para circuitos de potencia y de conversión de tensión ultra-bajas, adecuada para fuentes de energía del ambiente, usualmente muy limitadas en magnitud. Debido a que los TFETs están diseñados como diodos p-i-n en polarización inversa (hay diferente tipo de dopaje en las regiones fuente / drenador), sus características eléctricas particulares en condiciones de polarización inversa requieren cambios en las topologías de circuito convencionales. En la tesis, rectificadores, bombas de carga y circuitos de gestión de la energía (PMC) con TFETs se diseñan y analizan, realizando una evaluación de su rendimiento con la propuesta de nuevas topologías que extienden el rango de tensión y potencia de operación en comparación con tecnologías y topologías de circuitos actuales. Se proponen PMCs basados en TFET para fuentes de RF y DC y se identifican las limitaciones (con soluciones) de la utilización de TFETs en convertidores elevadores convencionales basados en inductores.
Hi ha hagut una tremenda evolució en la tecnologia de circuits integrats en les últimes dècades. Amb l'escalat de transistors de metall-òxid-semiconductor (CMOS), s'han fet possibles xips més ràpids, amb menys consum d'energia i més complexos amb menys àrea i això ha possibilitat l'existència dels aparells electrònics que veiem en l'actualitat. La creixent demanda de portabilitat implica que el consum d'energia és un indicador clau en el disseny analògic i digital. Mentre que el consum de potència dinàmica disminueix quadràticament amb la disminució de la tensió de font d'alimentació, la potència de fuites presenta una limitació a causa del pendent sub-llindar invers (sub-threshold slope, SS). Una reducció de la tensió d'alimentació implica una conseqüent reducció de tensió llindar a fi de mantenir les prestacions que, donat el SS fix, causa un augment exponencial del corrent de fuita. Això planteja una limitació en la reducció de consum d'energia que és inherent als transistors convencionals basats en injecció de portadors termoiònics (MOSFETS i FinFETs). En transistors termoiònics la SS a temperatura ambient està limitat a 60 mV / dec. Per eludir la limitació SS de transistors convencionals es requereixen dispositius amb mecanismes diferents d'injecció de portadors. El transistor túnel d'efecte camp (TFET) es presenta com la tecnologia més prometedora a causa del seu mecanisme d'injecció de portadors no tèrmic basat en l'efecte Band-To-Band Tunneling (BTBT). Els TFETs es coneixen com a dispositius d'alt pendent sots-llindar (SS <60 mV / dec a temperatura ambient). Han estat ja demostrats guanys de corrent gran (ION / IOFF> 10 ^ 5) en operació de baixa tensió (sub-0,25 V) i un corrent de fuites extremadament baix, col·locant els TFETs com a seriosos candidats per a aplicacions de circuits eficients d'ultra-baixa potència i energia. Els TFETs s'han explorat sobretot en circuits digitals i aplicacions. En aquesta tesi, l'ús de TFETs s'explora com una tecnologia alternativa també per a circuits de potència i de conversió de tensió ultra-baixes, adequada per a fonts d'energia de l'ambient, usualment molt limitades en magnitud. Degut a que els TFETs estan dissenyats com díodes p-i-n en polarització inversa (hi ha diferent tipus de dopatge en les regions font / drenador), les seves característiques elèctriques particulars en condicions de polarització inversa requereixen canvis en les topologies de circuit convencionals. En la tesi, rectificadors, bombes de càrrega i circuits de gestió de l'energia (PMC) amb TFETs es dissenyen i analitzen, realitzant una avaluació del seu rendiment amb la proposta de noves topologies que estenen el rang de tensió i potència d'operació en comparació amb tecnologies i topologies de circuits actuals. Es proposen PMCs basats en TFET per fonts de RF i DC i s'identifiquen les limitacions (amb solucions) de la utilització de TFETs en convertidors elevadors convencionals basats en inductors.

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Chang, Samuel C. "A 1-mW vibration energy harvesting system for moth flight-control applications." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/58456.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-98).
This thesis focuses on the approach and methodologies required to build a 1-mW energy-harvesting system for moth flight control applications. The crepuscular hawk moth Manduca sexta is the chosen test subject. This project is part of the Hybrid Insect MEMS (HI-MEMS) program. The objective of the program is to establish an interface between adult insect neural systems, wireless communication and MEMS systems so that insects may be directed to fly to specific locations in real time. As in all micro-air vehicles, power is one of the major concerns. A power source on the moth is required to support the flight control and wireless communication systems. There are two methods by which these payloads might be powered. The first method is to draw power from a battery, while the second method is to harvest energy from the environment. Batteries have the advantage of simplicity, while energy harvesting systems have much longer life and lower mass per total energy delivered. In addition, the total mass of circuitry, MEMS devices, and batteries may severely limit flight duration. Therefore, we have chosen the energy-harvesting method. The energy harvesting system includes a vibration energy harvester and a boost converter that delivers power at the required 1-V level for the entire flight control system.
(cont.) The latest harvester has a mass of 1.28 g and output power of 1.7 mW into a matched resistive load when the moth vibrates with a +0.37-mm amplitude at 25.8 Hz, resulting in a ±7.82-mm harvester amplitude. A 2-stage AC-DC boost converter with off chip inductors has been designed and fabricated in 0.18 um CMOS technology. SPICE simulation and experiments using equivalent discrete components prove that the converter can achieve 71.68% efficiency. The test experiment of the chip will be conducted later this winter and is not included in the scope of this thesis.
by Samuel C. Chang.
S.M.

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29

Martínez-Denegrí, Sánchez Guillermo. "Light harvesting and energy efficiency in perovskite solar cells and their applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/672666.

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The environmental issues associated with the use of conventional fuels necessitates the utilisation of renewable energy sources, as well as the implementation of energy efficient designs, in order to decrease electricity consumption. Photovoltaic (PV) technology can be employed for both approaches by converting not only natural but, also, artificial light into electricity. Among the different emerging PVs, perovskites achieve the highest power conversion efficiency, providing a widely tuneable bandgap with minimum open circuit losses. Moreover, their fabrication uses readily available materials, and does not necessarily require either the use of high temperature processes or vacuum deposition techniques. In this thesis, we enhance light harvesting in perovskite solar cells, and approach the energy efficiency concept through their optimised fabrication and integration in light selective structures. This is accomplished by the implementation of optical and material strategies applied to specific perovskite solar cell designs. The results prove that such strategies provide enhanced light absorption and optimal PV performance in low temperature devices, and enable the recycling of light into electricity for alternative photonic applications. The approaches presented could be utilised in future procedures to decrease the amount of Pb employed in perovskite solar cells, and to reduce the energy consumption during fabrication and the operation of other optoelectronic devices. The thesis is organised into four chapters. Chapter 1 serves as an introduction, where the current energy situation and PV technology are analysed, together with an insight into light harvesting and energy efficiency in perovskite solar cells. In Chapter 2, we demonstrate the employment of a periodic structure to propagate ergodic light in order to increase light absorption in perovskite solar cells, as would happen by employing randomly textured surfaces. This structure serves as a tool to decrease the Pb content used in perovskite solar cells, since 30% less material can be used to obtain a solar cell with equal performance. Then, in Chapter 3, the same periodic configuration with a thin film structure deposited on its surface is applied as a waveguide, which is also able to transmit polarised light. Moreover, two perovskite solar cells integrated on the sides recycle the non-transmitted light into electricity, increasing the energy efficiency of the optical process, with further application in liquid crystal displays (LCDs). Finally, in Chapter 4, we demonstrate the suitable application of a nanoparticle bilayer made of one layer of SnO2 and another of TiO2 as n-type materials in perovskite solar cells. These types of devices, based on low temperature processes, are proven to perform better than those containing one type of nanoparticles, especially in semi-transparent devices. In such devices we achieved an enhancement in performance of up to 30% for solar cells based on extremely thin active layers.
Los problemas medioambientales asociados al uso de combustibles convencionales requieren del uso de fuentes de energía renovables, así como de la implementación de diseños eficientemente energéticos para reducir el consumo de energía. La tecnología fotovoltaica puede emplearse para cubrir ambas estrategias convirtiendo no sólo la luz natural, sino también la artificial, en electricidad. De entre las diferentes tecnologías fotovoltaicas emergentes, las perovskitas alcanzan la más alta eficiencia en conversión de potencia, al mismo tiempo que proporcionan una banda de energía prohibida ampliamente ajustable con pérdidas mínimas de tensión de circuito abierto. Además, su fabricación usa materiales abundantemente disponibles, y no requiere necesariamente de procesos a alta temperatura ni de técnicas de deposición en vacío. En esta tesis, mejoramos la colección de luz en celdas de perovskitas, a la vez que abordamos el concepto de eficiencia energética a través de una fabricación optimizada y su integración en estructuras selectivas de luz. Esto es conseguido gracias a la implementación de estrategias ópticas y materiales aplicadas a diseños específicos de celdas solares de perovskita. Los resultados demuestran que tales estrategias proporcionan una colección de luz y un rendimiento fotovoltaico mayor aplicable a dispositivos fabricados a baja temperatura, y permiten el reciclaje de luz en electricidad para aplicaciones fotónicas alternativas. Las técnicas presentadas podrían ser utilizadas en procedimientos futuros para disminuir la cantidad de Pb empleado en celdas solares de perovskita, y para reducir el consumo de energía durante su fabricación y el funcionamiento de otros dispositivos optoelectrónicos. La tesis está organizada en cuatro capítulos. El Capítulo 1 sirve como una introducción, donde la actual situación energética y la tecnología fotovoltaica son analizadas junto a una descripción de la recolección de luz y la eficiencia energética en celdas solares de perovskita. En el Capítulo 2, demostramos el uso de una estructura periódica para propagar luz ergódicamente y así aumentar la absorción de luz en las celdas solares de perovskita, de manera equivalente a lo que se obtendría usando superficies aleatoriamente texturizadas. Esta estructura sirve como herramienta para reducir el contenido de Pb empleado en celdas solares de perovskita, ya que se puede utilizar 30% menos de material para obtener una celda solar con un rendimiento equivalente. En el Capítulo 3, la misma configuración periódica con una estructura de capa fina depositada en su superficie es empleada como guía de luz, la cual es, además, capaz de transmitir luz polarizada. Además, dos celdas de perovskita integradas en sus laterales reciclan la luz no transmitida en electricidad, incrementando la eficiencia energética del proceso óptico, lo cual podría tener futura aplicación en pantallas de cristal líquido. Finalmente, en el Capítulo 4, demostramos la aplicación de una bicapa de nanopartículas hecha de una capa de SnO2 y otra de TiO2 como materiales de tipo n en celdas solares perovskita. Este tipo de dispositivos, basados en procesos a baja temperatura, funcionan mejor que los que integran un único tipo de nanopartículas, especialmente en dispositivos semitransparentes. En tales dispositivos conseguimos un funcionamiento hasta 30% mejor para celdas solares basadas en capas activas extremadamente finas.
Fotònica

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30

Ramesh, Dinesh. "The Role of Interface in Crystal Growth, Energy Harvesting and Storage Applications." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1752367/.

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A flexible nanofibrous PVDF-BaTiO3 composite material is prepared for impact sensing and biomechanical energy harvesting applications. Dielectric polyvinylidene fluoride (PVDF) and barium titanate (BaTiO3)-PVDF nanofibrous composites were made using the electrospinning process based on a design of experiments approach. The ultrasonication process was optimized using a 2k factorial DoE approach to disperse BaTiO3 particles in PVDF solution in DMF. Scanning electron microscopy was used to characterize the microstructure of the fabricated mesh. The FT-IR and Raman analysis were carried out to investigate the crystal structure of the prepared mesh. Surface morphology contribution to the adhesive property of the composite was explained through contact angle measurements. The capacitance of the prepared PVDF- BaTiO3 nanofibrous mesh was a more than 40% increase over the pure PVDF nanofibers. A comparative study of dielectric relaxation, thermodynamics properties and impact analysis of electrospun polyvinylidene fluoride (PVDF) and 3% BaTiO3-PVDF nanofibrous composite are presented. The frequency dependent dielectric properties revealed micro structural features of the composite material. The dielectric relaxation behavior is further supported by complex impedance analysis and Nyquist plots. The temperature dependence of electric modulus shows Arrhenius type behavior. The observed non-Debye dielectric relaxation in electric loss modulus follows a thermally activated process which can be attributed to a small polaron hopping effect. The particle induced crystallization is supported with thermodynamic properties from differential scanning calorimetric (DSC) measurements. The observed increase in piezoelectric response by impact analysis was attributed to the interfacial interaction between PVDF and BaTiO3. The interfacial polarization between PVDF and BaTiO3 was studied using density functional theory calculations and atomic charge density analysis. The results obtained indicates that electrospinning offers a potential way to produce nanofibers with desired crystalline nature which was not observed in molded samples. In addition, BaTiO3 can be used to increase the capacitance, desired surface characteristics of the PVDF nanofibers which can find potential application as flexible piezoelectric sensor mimicking biological skin for use in impact sensing and energy harvesting applications.

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31

Trimble, A. Zachary. "Energy harvesting of random wide-band vibrations with applications to an electro-magnetic rotational energy harvester." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67604.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 205-207).
In general, vibration energy harvesting is the scavenging of ambient vibration by transduction of mechanical kinetic energy into electrical energy. Many mechanical or electro-mechanical systems produce mechanical vibrations. The kinetic energy associated with these mechanical vibrations represents a potential source of energy for sensors and other electronics. In fact, as the energy requirements for electronics and wireless communications systems has reduced, harvested energy from vibrations has been successfully used to power several wireless sensors. However, these sensors are implemented on systems with harmonic vibration sources. Most ambient vibrations are noisy, wide-band, and/or stochastic. As such, a resonant tuned-mass damper, with a narrow band-width, filters and discards much of the energy in the vibration spectrum, or worse, resonant harvesters will not resonate in stochastic environments. Several solutions are commonly proposed for harvesting energy from wide-band excitations; multiple resonators tuned to different frequencies (farm systems), non-linear systems, input excitation rectification, and frequency tuning are the most common. This thesis addresses some of the wide-band and/or stochastic challenges to vibration energy harvesting by investigating vibration energy harvesting as a power source for sensors and communications in a down-hole environment. This thesis shows that regardless of the transducer, a single resonant harvester tuned to the frequency with the maximum displacement times frequency cubed produces more power than a farm of resonant harvesters tuned to a range of frequencies. Additionally, this thesis shows that an electromagnetic harvester can be passively tuned to increase the power in a non-stationary system with a peak frequency that is a function of time. Finally, this thesis presents a new resonant, rotational architecture, which has the advantage of simultaneously maximizing the coupling inertia and displacement.
by A. Zachary Trimble.
Ph.D.

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32

Cao, Jinwei. "BIOELECTRICITY INSPIRED POLYMER ELECTROLYTE MEMBRANES FOR SENSING AND ENGERGY HARVESTING APPLICATIONS." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1541721597835991.

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33

Alothman, Abdulmohsen Abdulrahman. "Modeling and Applications of Thermoelectric Generators." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/79846.

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We develop a simplified one-dimensional numerical model that simulates the performance of thermoelectric generators (TEG). The model is based on the energy and electrical potential field equations. The Seebeck coefficient, thermal conductivity, electrical resistivity and Thomson coefficient of the TEG material are used to predict the harvested power. Bismuth-telluride is used as semiconductors materials of the TEG, which is the most commonly used material by industry. Experiments on three TEG modules were performed to validate the numerical model. A comparison with predicted levels of harvested energy based on the TEG specifications is also performed. The results show differences between the experimental and numerical values on one hand and the predicted ones on the other hand. The reason for these differences are discussed. A procedure to estimate the sensitivity of the harvested power to different inputs and TEG parameters is detailed. In the second part of the dissertation, we integrate a thermoelectric generator with an organic storage device. The performance of the integrated system for different values of load resistances and temperature gradients is determined. Finally, we demonstrate that power generated from a TEG is related to the flow rate in a pipe and can, thus, be used as a flow meter. Particularly, a dimensionless relation between the TEG's peak power and Reynolds number is determined.
Ph. D.

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34

Song, Hang. "Fabrication and characterisation of electrospun polyvinylidene fluoride (PVDF) nanocomposites for energy harvesting applications." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/12850.

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Three systems of electrospun composite membranes with piezoelectric polymer polyvinylidene fluoride (PVDF) as matrix incorporating: 1) Carbon based fillers: carbon nanotube (CNT) and graphene oxide (GO); 2) Ceramic based fillers-barium titanate (BT), zinc oxide (ZnO) and nanoclays (halloysite and bentonite); 3) Cellulosic fillers: microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC) at different loadings were prepared by electrospinning process. Influence of filler type and loading on total PVDF crystallinity (Xc), relative fraction of β phase (piezoelectric phase) in total crystalline PVDF (Fβ), volume fraction of β phase in the samples (vβ) and piezoelectric coefficient d33 were characterised and analysed. Correlation between vβ and piezoelectric performance (d33) will be focused by this work. A common situation was observed for the composites-d33 increased while vβ is reduced by the fillers, so it can be concluded that d33 of the composites is not totally up to their vβ, there are other factors that need to be taken into account. For example, for carbon based filler like CNT, it increased electric conductivity of sample during and after electrospinning process, making it easier for charges produced by β crystals from inside of sample to be transferred to surfaces of the sample, and possibly promoting orientation of β crystals in d33 direction, therefore enhanced d33 of the composites though β phase formation was significantly hindered by inclusion of CNT; For piezoelectric ceramic fillers like BT and ZnO, a possible combined piezoelectricity from filler and β phase PVDF might enhanced d33 though less β phase was formed; And for non-piezoelectric and non-conductive fillers, enhancement in orientation of β crystals might play a major role in promotion of d33. Keywords: electrospinning; polyvinylidene fluoride (PVDF); nanocomposites; piezoelectric coefficient d33; energy harvesting.

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35

Masghouni, Nejib. "Hybrid Carbon Fiber/ZnO Nanowires Polymeric Composite for Stuctural and Energy Harvesting Applications." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64354.

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Despite the many attractive features of carbon fiber reinforced polymers (FRPs) composites, they are prone to failure due to delamination. The ability to tailor the fiber/matrix interface FRPs is crucial to the development of composite materials with enhanced structural performance. In this dissertation, ZnO nanowires (NWs) were grown on the surface of carbon fibers utilizing low temperature hydrothermal synthesis technique prior to the hybrid composite fabrication. The scanning electron microscopy revealed that the ZnO nanowires were grown uniformly on the surface of the carbon fabric. The surface grown ZnO NWs functionally-graded the composite material properties and ensured effective load transfer across the interface. To assess the influence of the ZnO NWs growth, reference samples were also prepared by exposing the carbon fabric to the hydrothermal conditions. The damping properties of the hybrid ZnO NWs-CFRP composite were examined using the dynamic mechanical analysis (DMA) technique. The results showed enhanced energy dissipation within the hybrid composite. Quasi-static tensile testing revealed that the in-plane and out-of-plane strengths and moduli of the hybrid FRP composite were also boosted. The interlaminar shear strength (ILSS) measurements suggested the improvement in the mechanical properties of the composite to the enhanced adhesion between the ZnO nanowires and the other constituents (carbon fiber and epoxy). It was necessary thus, to utilize the molecular dynamics simulations (MD) to investigate the adhesion within the CFRP structure upon growing the ZnO nanowires on the surface of the carbon fibers. Molecular models of the carbon fibers, the epoxy matrix and the ZnO nanowires were built. The resulting molecular structures were minimized and placed within a simulation box with periodic boundary conditions. The MD simulations were performed using the force field COMPASS to account for the empirical energy interactions between the different toms in the simulation box. Proper statistical thermodynamics were employed to relate the dynamics of the molecular model to the macroscale thermodynamic states (pressure, temperature and volume). Per the computed potential energies of the different components of the composite, it was found that the polar surfaces in the ZnO structures facilitates good adhesion properties in the graphite-epoxy composite. Besides the attractive mechanical properties of the ZnO nanowires, their piezoelectric and semiconductor properties were sought to design an energy harvesting device. To ensure sufficient charges collection from the mechanically stressed individual ZnO nanowires, a copper layer was sputtered on top of the ZnO nanowires which introduced also a Schottky effect. The mechanical excitation was provided by exposing the device to different vibration environment. The output voltage and currents were measured at the conditions (in terms of frequency and resistive load). It was demonstrated that the electrical output could be enhanced by stacking up similar devices in series or in parallel. Finally, in an attempt to exploit the reversibility of the electromechanical coupling of the energy harvesting device, the constitutive properties of the hybrid ZnO nanowires-CFRP composite were estimated using the Mori-Tanaka approach. This approach was validated by a finite element model (FEM). The FEM simulations were performed on a representative volume element (RVE) to reduce the computational time. The results demonstrated that the mechanical properties of the hybrid ZnO NWs-CFRP composite were better than those for the baseline CFRP composite with identical carbon fiber volume fraction (but with no ZnO NWs) which confirmed the experimental findings. Furthermore, the electro-elastic properties of the hybrid composite were determined by applying proper boundary conditions to the FE RVE. The work outlined in this dissertation will enable significant advancement in the next generation of hybrid composites with improved structural and energy harvesting multifunctionalties.
Ph. D.

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36

Deshpande, Samruddhi Aniruddha. "Numerical Investigation of Various Heat Transfer Performance Enhancement Configurations for Energy Harvesting Applications." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/72129.

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Conventional understanding of quality of energy suggests that heat is a low grade form of energy. Hence converting this energy into useful form of work was assumed difficult. However, this understanding was challenged by researchers over the last few decades. With advances in solar, thermal and geothermal energy harvesting, they believed that these sources of energy had great potential to operate as dependable avenues for electrical power. In recent times, waste heat from automobiles, oil and gas and manufacturing industries were employed to harness power. Statistics show that US alone has a potential of generating 120,000 GWh/year of electricity from oil , gas and manufacturing industries, while automobiles can contribute upto 15,900 GWh/year. Thermoelectric generators (TEGs) can be employed to capture some of this otherwise wasted heat and to convert this heat into useful electrical energy. This field of research as compared to gas turbine industry has emerged recently over past 30 decades. Researchers have shown that efficiency of these TEGs modules can be improved by integrating heat transfer augmentation features on the hot side of these modules. Gas turbines employ advanced technologies for internal and external cooling. These technologies have applications over wide range of applications, one of which is thermoelectricity. Hence, making use of gas turbine technologies in thermoelectrics would surely improve the efficiency of existing TEGs. This study makes an effort to develop innovative technologies for gas turbine as well as thermoelectric applications. The first part of the study analyzes heat transfer augmentation from four different configurations for low aspect ratio channels and the second part deal with characterizing improvement in efficiency of TEGs due to the heat transfer augmentation techniques.
Master of Science

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37

Melilli, Giuseppe. "Irradiation and nanostructuration of piezoelectric polymers for nano-sensoring and harvesting energy applications." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX072/document.

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La polyvalence de la technique de track-etching a permis d’étudier plus avant l’effet piezoélectrique direct et indirect d’un film polarisé en poly(fluorure de vinylidène) PVDF en créant des membranes nanostructurées hybrides de nanofils de nickel (Ni NWs)/PVDF. Les propriétés magnétiques du nanofil de nickel, telle que la magnétorésistance anisotrope (AMR), ont été exploitées afin d’étudier la réponse de l’aimantation à la déformation mécanique de la matrice PVDF. En particulier, les déformations ont été induites soit par contrainte thermo-mécanique, soit par contrainte électromécanique (effet piezoélectrique indirect). La sensibilité d’un nanofil unique a permis de déterminer l’amplitude et la direction de la contrainte mécanique exercée à l’échelle nanométrique par la matrice PVDF. La résistance exceptionnelle de la réponse piezoélectrique directe du film PVDF polarisé à l’irradiation, telle que l’irradiation aux ions-lourds accélérés et aux électrons (domaine de doses < 100kGy) a été observée. Mis à part la conservation de la réponse piezoélectrique, les défauts engendrés par l’irradiation dans ce domaine de dose (scissions de chaines, augmentation de phase crystalline, réticulations) ont eu un impact significatif sur la structure du matériau polymère. L’ensemble de ces défauts, les uns prépondérants en-dessous de la dose-gel ( 10kGy), les autres au-dessus, forme une compensation d’effets antagonistes qui mènent à une réponse piezoélectrique globalement inchangée. Stimulé par la grande résistance du PVDF à l’irradiation en termes de réponse piezoélectrique, l’idée a été d’exploiter, en vue d’une application dans la récupération d’énergie, le réseau de nanofils de nickel inclus dans la membrane en PVDF polarisé pour étudier l’influence des nanofils de nickel sur la l’efficacité piezoélectrique. La présence du réseau de nanofils de nickel mène à un accroissement non négligeable de l’efficacité piezoélectrique. Reliée à la présence des nanofils, une augmentation de la permittivité diélectrique dans le PVDF nanostructuré a également été enregistrée. Une polarisation interfaciale entre les nanofils de nickel et la matrice PVDF pourrait expliquer cette valeur accrue par rapport au PVDF nanoporeux sans nanofils
The versatility of the track-etching technique has allowed to investigate deeper the direct and inverse piezoelectric effect of a polarized Poly(vinylidene fluoride) (PVDF) film in building nanostructured hybrid Nickel nanowires (Ni NWs)/PVDF membrane. The magnetic properties of the Ni NW, such as anisotropic magneto resistance (AMR), are exploited to investigate the response of the magnetization to a mechanical deformation of the PVDF matrix. In particular, the deformations were induced either by thermo-mechanical or an electro-mechanical (inverse piezoelectric effect) stress. The sensitivity of the single NW has allowed to determine the amplitude and direction of a mechanical stress exerted at the nano-scale by the PVDF matrix. The outstanding resistance of the direct piezoelectric response of polarized PVDF film to radiation, such as SHI and e-beam, (doses range < 100kGy) was reported. Beyond the conservation of the piezoelectric response, in this dose range, irradiation defects (chain scissions, increase of the crystalline -phase, crosslinking) had a significative impact on the polymer material. All these defects, ones predominant above the gel dose (herein 10 kGy), and the other ones below, compensate their antagonistic effects towards the globally unchanged piezoelectric responses. Motivated by the high radiation resistance of the PVDF in terms of piezoelectric response, the idea was to exploit Ni NWs array embedded in the polarized PVDF membrane to study the influence of the Ni NWs on the piezoelectric response in view of harvesting energy application. The presence of the Ni NWs array leads a non-negligible increase of the piezoelectric efficiency. Related to the presence of the NWs, an increase of the dielectric permittivity in the nanostructured PVDF was also reported. An interfacial polarization between the Ni NWs and the PVDF matrix could explain the higher efficiency value respect to nanoporous PVDF, without NWs

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38

KIPTIEMOI, KIPRONO KORIR. "ZnO nanowires for energy harvesting and gas sensing applications: a quantum mechanical study." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2539901.

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The research activity related to my PhD project is focused on providing a better understanding on energy harvesting capabilities and gas sensing mechanism of ZnO nanowires. Nanowires made of materials with non-centrosymmetric crystal structures are expected to be ideal building blocks for self-powered nanodevices due to their piezoelectric properties, yet a controversial explanation of the effective operational mechanisms and size effects still delays their real exploitation. To solve this controversy, we propose a methodology based on Density Functional Theory (DFT) calculations of the response of nanostructures to external deformations that allows us to distinguish between the different (bulk and surface) contributions: we apply this scheme to evaluate the piezoelectric properties of ZnO [0001] nanowires, with a diameter up to 2.3 nm. Our unified approach allows for a proper definition of piezoelectric coefficients for nanostructures, and explains in a rigorous way the reason why nanowires are found to be more sensitive to mechanical deformation than the corresponding bulk material. Gas-sensing mechanism of ZnO nanowire is investigated using ethanol as our prototype gas. In particular, we show that in the case of ethanol, it has larger binding energy to the ZnO surface compared to oxygen gas, hence able to remove pre-adsorbed oxygen molecules on the surface, and leads to release of trapped electrons to conduction band. Therefore, ZnO sensing is strongly linked to oxygen removal from the surface. Furthermore, in this work oxygen vacancies distribution and concentration in ZnO nanostructures, which is still a question of debate is investigated using combined DFT and Climbing-Image Nudged Elastic Bands (CI-NEB) approach. This work has successfully addressed some of the unanswered questions related to application of ZnO nanowires in field of energy harvesting and gas sensing, and may invaluable in fine-tuning nano-devices to attain enhance performance.

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39

IMBRAGUGLIO, DARIO. "Nanostructured carbon/silicon composite opto-electrochemical devices for sensing and energy harvesting applications." Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2506359.

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My research activity deals with fabrication, characterization and functionalization techniques of silicon-based nanostructures and systems, such as silicon nanowires and nanostructured porous silicon. In particular, I focused my final dissertation thesis on the synthesis and study of a new class of carbon/silicon nanocomposites, produced by a recently discovered carbonization chemistry of porous silicon. Such a new chemistry has been optimized in order to obtain samples amenable for applications into a liquid dynamic environment. The employed carbon nanocasting process provides both a stable and conductive hybrid nanomaterial, allowing the carbonized porous silicon film to act as working electrode in aqueous media. The electrode stability has been tried out in different liquids as well as under voltage applied. Moreover, the optical properties of the nanostructure enable its use as a sensor for electrically charged species in buffer solutions, such as biomolecular complexes. By application of an electrical potential difference between the working and a counter electrode, the sensor is able to simultaneously attract and detect both positively than negatively charged targets. In the case of electroadsorbed biomolecules, indications on the retention of their functional activity after releasing from the electrode surface are also provided. Furthermore, an electrical measurement system has been added to the optical one in order to monitor, in real-time with the optically transduced signal, the current flowing between the two electrodes during the sensing experiments. A few prototypes which synchronize the optical and electrical responses of the sensor have been fabricated and their performances tested by varying the electrical parameters. These new combined opto-electrochemical devices can potentially find applications both in future label-free sensing than in next-generation energy harvesting technologies.

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40

Boughey, Chess. "Electrodeposited functional nanowires for energy applications." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277679.

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Nanostructuring functional materials can lead to a variety of enhanced intrinsic material properties. In particular, nanowires (NWs) have large surface-to-volume ratio and large aspect ratio (length / diameter), which makes them sensitive to low-amplitude vibrations and have increased flexibility compared to the bulk form of the material. In this thesis, piezoelectric, ferroelectric, ferromagnetic and magnetoelectric (ME) NWs have been explored in the context of vibrational energy harvesting and magnetic energy harvesting and sensing; because of their increased piezoelectric coefficients and ME coupling compared to bulk. Low-temperature, solution-processable and hence scalable fabrication techniques have been used throughout this work. Electrochemical deposition or electrodeposition (ED) in conjunction with nanoporous templates i.e. template-assisted electrodeposition (TAED) have been used to grow piezoelectric zinc oxide (ZnO) and ferromagnetic nickel (Ni) NWs and three template-wetting based techniques have been used to grow ferroelectric poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) NWs and nanotubes (NTs). Both techniques have been optimised and subsequently combined to synthesise core-shell or (1-1) Ni - P(VDF-TrFE) composite NWs. The structural and crystalline properties of each type of nanostructure has been studied using a variety of techniques including: scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM) and all of the NWs have been shown to be polycrystalline. The energy harvesting performance of vertically aligned ZnO NW arrays embedded in flexible, polycarbonate (PC) templates when incorporated into a flexible nanocomposite nanogenerator (NG), has been tested via periodic impacting and flexing of the NG at different frequencies. The voltage ($V$), current ($I$) and power were recorded during testing and measured across a range of external load resistances. The aligned nature of the embedded NWs ensures good piezoelectric performance across the entire device under impacting, while the PC template ensures mechanical stability and longevity of the device, confirmed by good fatigue performance over 24 hours of continuous testing, which is rarely studied in this field. The power density ($P_\mathrm{d}$) was found to be 151 mW m$^{-3}$ for low-amplitude (0.68 mm) and low-frequency (5 Hz) impacting, resulting in energy conversion efficiencies ($\chi$) and device efficiencies ($\chi$') of $\approx$ 4.2 \% and $\approx$ 3.76 x 10$^{-3}$ \% respectively. The nanoscale or surface piezoelectric charge coefficient ($d_{33}$) was measured to be $\approx$ 12.5 pm V$^{-1}$ on an individual ZnO NW, using a combination of Kelvin probe force microscopy (KPFM) and non--destructive piezoresponse force microscopy (ND-PFM). Both nanoscale and bulk ME measurements have been performed on Ni - P(VDF-TrFE) ME composite (1-1) NWs, nanocomposite (1-3) films and (2-2) laminates. The latter two structures have been fabricated using TAED and ED for the Ni NW and film respectively, in combination with drop-casting and spin-coating for the P(VDF-TrFE) films. The scanning probe microscopy (SPM) measurements used here include atomic force microscopy (AFM), KPFM, magnetic force microscopy (MFM) and piezoresponse force microscopy (PFM) and it has been found that the ME coupling in the (1-1) composites NWs is enhanced compared to the other structures, confirmed by approximating the converse ME coupling coefficient ($\alpha^\mathrm{C}$) of each composite. Additionally, vibrating sample magnetometry (VSM) has been used to confirm the ferromagnetic nature of the Ni phases in the composite structures. ME composite devices based on (2-2) and (1-3) composite materials and have been fabricated and preliminary bulk ME measurements of the ME coupling coefficient ($\alpha^\mathrm{E}$) plus energy harvesting measurements have also been performed as a proof of concept that the nanoscale ME coupling translates to the bulk, to some extent.

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41

Álvarez-Carulla, Albert. "Energy Harvesting Solutions for Self-Powered Devices: From Structural Health Monitoring to Biomedical Applications." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/670900.

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The thesis reflects the research carried out on the development of truly self-powered devices. The development of devices for the scopes of Structural Health Monitoring (SHM) and Point-of-Care devices (PoC) is shown. New solutions are implemented in the field of energy harvesting to use a single transducer as sensor element and power supply for the system. In this research, the transducers used are piezoelectric generators and galvanic cells, being extrapolated the developments made to other types of transducers or generators.
La tesis recoge la investigación realizada sobre el desarrollo de dispositivos verdaderamente auto- alimentados. Se muestra el desarrollo de dispositivos para el ámbito de la monitorización de la salud de estructuras (SHM) y el ámbito de los dispositivos Point-of-Care (PoC). Para ello, se implementan nuevas soluciones del ámbito de la recolección de energía para utilizar un único transductor como elemento sensor y de fuente de alimentación para el sistema. En esta investigación, los transductores utilizados son generadores piezoeléctricos y celdas galvánicas, siendo extrapolables los desarrollos realizados a otro tipos de transductores o generadores.

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42

Reed, Ryan Tyler. "Wireless Information and Power Transfer Methods for IoT Applications." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104146.

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As Internet of Things (IoT) technology continues to become more commonplace, demand for self-sustainable and low-power networking schemes has increased. Future IoT devices will require a ubiquitous energy source and will need to be capable of low power communication. RF energy can be harvested through ambient or dedicated RF sources to satisfy this energy demand. In addition, these RF signals can be modified to convey information. This thesis surveys a variety of RF energy harvesting methods. A new low complexity energy harvesting system (circuit and antenna) is proposed. Low power communication schemes are examined, and low complexity and efficient transmitter designs are developed that utilize RF backscattering, harmonics, and intermodulation products. These communication schemes operate with minimal power consumption and can be powered solely from harvested RF energy. The RF energy harvester and RF-powered transmitters designs are validated through simulation, prototyping, and measurements. The results are compared to the performance of state-of-the-art devices described in the literature.
Master of Science
Future devices are expected to feature high levels of interconnectivity and have long lifetimes. RF energy from dedicated power beacons or ambient sources, such as Wi-Fi, cellular, DTV, or radio stations can be used to power these devices allowing them to be battery-less. These devices that harvest the RF energy can use that energy to transmit information. This thesis develops various methods to harvest RF energy and use this energy to transmit information as efficiently as possible. The designs are verified through simulation and experimental results.

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43

Chen, Yu-Yin. "Piezoelectric power transducers and its interfacing circuitry on energy harvesting and structural damping applications." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00847336.

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Nowadays with the world oil price soaring, the energy issue is becoming a significant topic and the possibility of harvesting ambient energy receiving much attention. In this dissertation, the main topic surrounds improving the piezoelectric energy harvesting device in several aspects and the final objective is to integrate it with low power consumption device, for example a wireless sensor network (WSN) node to extend the battery lifetime and further supply the energy to device directly. Based on the high mechanical quality factor of the structure, the output power of the piezoelectric energy harvesting device will decrease rapidly when the exciting frequency is out of the resonant frequency range. The tunable resonant frequency technique is proposed to broaden the resonant frequency range and increase the output power effectively. Then this technique is successfully combined with a WSN module to transmit the RF signal. To broaden resonant frequency another method is proposed, based on a bistable vibrating cantilever beam and a switching-type interface circuit (SSHI). It's a new and interesting concept to combine these two techniques. The magnets are used to make mechanical behavior non-linear and increase the output power at non-resonance. The SSHI technique through zero-velocity detection can work well when system is driven in non-linear system. The experimental and simulation results through work-cycles discussion show good performance of combining these two techniques. In the interface circuit design, synchronized switching harvesting on an inductor (SSHI) have been verified a successful technique to increase output power in low-coupling system. In order to make use of the SSHI technique in the real application, the velocity control self-powered SSHI (V-SSHI) system is proposed. Unlike the conventional peak detector technique, the zero-velocity detection is used to make the switching time more accurate. The energy flow is separated into three paths to construct the V-SSHI and the experimental results show good performance. When the system is not low-coupled, the SSHI technique will damp vibration.This technique is called SSDI (synchronized switching damping on an inductor). Based on the self-powered technique and zero-velocity detection used in the V-SSHI, these techniques are further applied in structural damping to construct a self-powered SSDI (SP-SSDI). The major advantage is that it is only necessary to sacrifice a small amount of damping performance to make the system fully self-powered. The theoretical analysis and experiment results of time domain comparison and frequency response testing show the limit and performance of the SP-SSDI technique. The SP-SSDI system is a like a feedback loop system and when the displacement is over the limit the SP-SSDI will effectively damp the vibration.

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44

Wang, Leran. "Mixed technology modelling and optimisation for automotive, energy harvesting and MEMS applications using VHDL-AMS." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/65104/.

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This research work investigates methodologies for VHDL-AMS based mixed technology modelling and optimisation, specifically with automotive, energy harvesting and MEMS applications in mind. The contributions are summarised as follows: Firstly, methodologies that support modelling and simulation of mixed-domain automotive systems have been developed. VHDL-AMS and its standard packages have been used to generate efficient models of complex automotive systems. Secondly, a novel, VHDL-AMS based optimisation of fuzzy logic controllers has been developed. The idea is to optimise the shapes of fuzzy logic membership functions using a genetic algorithm. Since the system to be optimised is also implemented in VHDLAMS, this methodology has resulted in an integrated performance optimisation system that is wholly implemented in a hardware description language. Thirdly, the first complete VHDL-AMS modelling approach has been presented for the DATE’99 benchmark to model a portal crane and embedded control. The model was proposed for a DATE’99 technical panel discussion to compare different languages for system level specification. The obtained new benchmark results have proved the suitability of VHDL-AMS for creating executable specifications of heterogeneous embedded systems. Fourthly, an automated energy harvester design flow which is based on a single HDL software platform that can be used to model, simulate, configure and optimise energy harvester systems has been proposed. VHDL-AMS has been used to incorporate various parts of the energy harvester (micro-generator, voltage booster, etc) into a single model. The salient feature of an integrated model is that it allows optimisation based on system performance, which is not possible in conventional modelling approaches. Fifthly, to enhance the modelling capability of VHDL-AMS for systems with MEMS structures where distributed behaviour is essential, language extensions have been proposed to efficiently implement general partial differential equations. The extended language has been named VHDL-AMSP. A suitable preprocessor has been developed to automatically convert VHDL-AMSP into the existing VHDL-AMS 1076.1 standard, so that models with partial differential equations can be simulated using currently available simulators. Finally, case studies have been presented to validate the developed methodologies. These case studies include: a portal crane and its embedded control, an automotive vibration isolation seating system, a fuzzy logic controller for automotive active suspension systems, a vibration-based electromagnetic energy harvester, and a MEMS accelerometer in high-order sigma-delta-modulator loops.

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45

Meek, Romney. "Synthesis and Characterization of Graphene-family Mesoporous Nanomaterials for Themal Energy Harvesting and Sensing Applications." TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/3090.

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Graphene-family nanomaterials (GFNs) have attracted a great deal of attention both in academia and in industry for a range of applications relevant for homeland security. In this thesis, an array of graphene-based hybrid materials and aerogels are synthesized for use as novel thermo-electrochemical energy harvesters and for ascorbic acid biosensing devices. The graphene-family nanomaterials include graphene oxide-GO, thermally reduced GO-rGOth, nitrogenated functionalized graphene-NFG, graphene aerogel-GA, nitrogen-doped graphene aerogel-NGA, multi-walled carbon nanotube aerogel-MWCNT, single-walled carbon nanotube aerogel-SWCNT, graphene and nanotube combined ‘hybrid’ aerogels-Gr:(SW/MW)CNT of various ratios, along with multilayered nanostructured architectures such as gold (AuNP) and silver nanoparticles (AgNP) decorated NFG coated with a thin layer of polyaniline (PANi). Precursor aerogel materials were also analyzed to demonstrate the effect of mesoporous architectures and the interplay of various components in augmenting physical-chemical properties. These precursors were combined through multiple deposition schemes including electrodeposition, hydrothermal synthesis, and freeze drying techniques. This project was developed in an effort to enhance electrochemical properties through modification of the morphology, surface and structural properties, making them more suitable for thermal energy harvesting and bio-sensing applications. Hydrothermal synthesis created chemical bridged interfaces, interconnectedness, and improved electrical conductivity besides increasing the surface area of mesoporous aerogels created by freeze-drying. This causes an increase in the number density of electrochemically active sites. The surface morphology, lattice vibrations, and electrochemical activity of the materials were investigated using electron microscopy, micro-Raman Spectroscopy, and electrochemical microscopy techniques [namely cyclic voltammetry (CV), alternating current electrochemical impedance spectroscopy (acEIS), amperometric techniques, and scanning electrochemical microscopy (SECM)]. For thermoelectric and thermoelectrochemical power measurements, a custom-designed set up was made for creating a temperature gradient across two legs of a thermocell and experiments were performed in various device configurations (a) symmetric and asymmetric, (b) single thermocells, and (c) multiple (“in-tandem”) thermocells. Interestingly, we observed changes in conducting behavior from Ohmic to semiconducting and polarity shifts from positive to negative or vice versa on introduction of the redox electrolyte solution. The parametric correlations (thermopower and resistivity or conductivity) are established and the results are discussed in terms of the polarity switching behavior observed for some of the aerogels combinations.

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46

Lin, Rui. "Archimedean Screw Turbine Based Energy Harvester and Acoustic Communication in Well Site Applications." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/104385.

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Wireless Sensor Networks (WSNs) has become increasingly important in the Oil and Gas industry. Despite the various advantages WSN has compared to the wired counter parts, it also faces some critical challenges in the oil fields; one of them is the power supply. The periodic replacement of batteries for the WSN in the downhole environments has been economically inconvenient and the enormous cost induced by the maintenance has turned people's attention to the energy harvesting technology, hoping for a more sustainable solution. Power supply is only half of the problem. To retrieve the data recorded by the various sensors in the downhole environments, a reliable way of wireless communication is required. A new approach utilizing acoustic communication was proposed. This thesis presents an Archimedean Screw Turbine (AST) based energy harvester that takes advantage of the abundant flow energy in the upper stream section of the oil production cycle, especially in the water injection wells and oil extraction wells, with the goal of providing power supply to Wireless Sensor Networks (WSNs) and underwater acoustic modems deployed in the various locations in the downhole environments. Parametric study on the number of blades, screw length, screw pitch, and rotational speed was conducted through CFD analysis using Ansys Fluent in order to determine the optimal geometry and operating conditions. The relationship between power generation and AST geometries, such as AST length and AST pitch, were discovered and the optimal rotational speed was revealed to be solely dependent on the screw pitch. Experiments were conducted in the lab environment with various flow rates and various external resistive loads to verify and determine the maximum power generation of the designed harvester. FEA analysis was conducted using the Acoustic and Structural Interaction Module of COMSOL MULTIPHYSICS to determine the attenuation characteristics of acoustic waves propagating in the water-filled pipes buried in soil. Experiments with and without the harvester integrated in the pipe system were conducted in lab environment using a pair of under water acoustic modems to determine the acoustic communication capability. The impact of the integrated harvester on the acoustic communication was tested. Combining energy harvesting technology and underwater acoustic communication together, this system can potentially achieve real-time monitoring and communication in the oil downhole environment.
Master of Science
Oil and Gas industry has been the primary energy source provider for our society for hundreds of years. As this industry evolves with new technologies, it also faces new challenges. One of the main challenges is the power supply problem in the oil field because of the limited lifespan of traditional batteries used in the oil production process. This study present a novel energy harvesting device that can replace the traditional batteries. By taking advantage of the constant fluid flow in various wells at oil field, the device can provide power for electronic devices, including but not limited to wireless sensors, communication modules, at the oil extraction sites, without needing additional power supply. This novel energy harvesting device can also be integrated with communication modules that uses acoustic wave to achieve wireless acoustic communication between underground and the surface. In this study, the harvester design, optimization, tests, and integration with acoustic modems were presented. With the help of such energy harvesting device, Oil and Gas industry will be one step closer to achieving true wireless, and real-time monitoring and communication. This will not only reduce maintenance cost but also greatly improve the production efficiency.

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47

Ahmet, Ibrahim. "An investigation of tin chalcogenide precursors and thin film materials for applications in energy harvesting devices." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715286.

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This thesis ‘’An Investigation of Tin Chalcogenide Precursors and Thin Film Materials for Applications in Energy Harvesting Devices’’ encompasses a range of research areas. The report can be divided into two categories: The first is the design of novel heavy tin chalcogenide complexes and compounds that demonstrate the recent advances in main group chemistry and act as potential precursor candidates for CVD processes. The second category follows on from the previous, and focuses on materials deposited and their successive development, characterisation and optimisation for device applications. Subsequently, an array of metal chalcogenide thin films have been deposited and characterised within this project. By designing of a number of the tin chalcogenide precursors and precursor solutions it has been possible to selectively deposit thin films of Sn, α-SnS and cubic-SnS polymorphs, SnS2, SnSe, and SnTe via a low-cost deposition route known as aerosol assisted chemical vapour deposition (AA-CVD). It is proposed that the processes developed in this PhD can be adapted to deposit a wider spectrum of metal chalcogenide materials using cost effective techniques. Even though there is a wide scope of the possible applications for the aforementioned materials, the study has only been extended towards the characterisation of the optoelectronic properties of phase pure α-SnS and cubic-SnS samples, and SnS2 thin films deposited onto FTO, Mo and graphene substrates. The optimum deposition parameters for the application of these materials has been defined. In collaboration with a research group at the Institut de Recerca de Energia de Catalunya (iREC), Barcelona, Spain, an extended study of the photovoltaic properties of the α-SnS and Cubic-SnS samples is also presented, from which a series of SnS based thin film photovoltaic devices have been fabricated and characterised. This study present some of the few reports explicitly comparing the PV properties of the two α-SnS and Cubic-SnS polymorphs.

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48

Mayer, Matthew T. "Ionic and electronic behaviors of earth-abundant semiconductor materials and their applications toward solar energy harvesting." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3034.

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Thesis advisor: Dunwei Wang
Semiconductor devices offer promise for efficient conversion of sunlight into other useful forms of energy, in either photovoltaic or photoelectrochemical cell configurations to produce electrical power or chemical energy, respectively. This dissertation examines ionic and electronic phenomena in some candidate semiconductors and seeks to understand their implications toward solar energy conversion applications. First, copper sulfide (Cu₂S) was examined as a candidate photovoltaic material. It was discovered that its unique property of cation diffusion allows the room-temperature synthesis of vertically-aligned nanowire arrays, a morphology which facilitates study of the diffusion processes. This diffusivity was found to induce hysteresis in the electronic behavior, leading to the phenomena of resistive switching and negative differential resistance. The Cu₂S were then demonstrated as morphological templates for solid-state conversion into different types of heterostructures, including segmented and rod-in-tube morphologies. Near-complete conversion to ZnS, enabled by the out-diffusion of Cu back into the substrate, was also achieved. While the ion diffusion property likely hinders the reliability of Cu₂S in photovoltaic applications, it was shown to enable useful electronic and ionic behaviors. Secondly, iron oxide (Fe₂O₃, hematite) was examined as a photoanode for photoelectrochemical water splitting. Its energetic limitations toward the water electrolysis reactions were addressed using two approaches aimed at achieving greater photovoltages and thereby improved water splitting efficiencies. In the first, a built-in n-p junction produced an internal field to drive charge separation and generate photovoltage. In the second, Fe₂O₃ was deposited onto a smaller band gap material, silicon, to form a device capable of producing enhanced total photovoltage by a dual-absorber Z-scheme mechanism. Both approaches resulted in a cathodic shift of the photocurrent onset potential, signifying enhanced power output and progress toward the unassisted photoelectrolysis of water
Thesis (PhD) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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49

Ababneh, Majdi M. "Design of Micro-Scale Energy Harvesting Systems for Low Power Applications Using Enhanced Power Management System." Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7117.

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The great innovations of the last century have ushered continuous progress in many areas of technology, especially in the form of miniaturization of electronic circuits. This progress shows a trend towards consistent decreases in power requirements due to miniaturization. According to the ITRS and industry leaders, such as Intel, the challenge of managing and providing power efficiency still persist as scaling down of devices continues. A variety of power sources can be used in order to provide power to low power applications. Few of these sources have favorable characteristics and can be designed to deliver maximum power such as the novel mini notched turbine used as a source in this work. The MiNT is a novel device that can be used as a feasible energy source when integrated into a system and evaluated for power delivery as investigated in this work. As part of this system, a maximum power point tracking system provides an applicable solution for capturing enhanced power delivery for an energy harvesting system. However, power efficiency and physical size are adversely affected by the characteristics and environment of many energy harvesting systems and must also be addressed. To address these issues, an analysis of mini notched turbine, a RF rectenna, and an enhanced maximum power point tracking system is presented and verified using simulations and measurements. Furthermore, mini notched energy harvesting system, RF rectenna energy harvesting system, and enhanced maximum power point tracking system are developed and experimental data analyzed. The enhanced maximum power point tracking system uses a resistor emulation technique and particle swarm optimization (PSO) to improve the power efficiency and reduce the physical size. This new innovative design improves the efficiency of optimized power management circuitry up to 7% compared to conventional power management circuits over a wide range of input power and range of emulated resistances, allowing more power to be harvested from small energy harvesting sources and delivering it to the load such as smart sensors. In addition, this is the first IC design to be implemented and tested for the patented mini notched turbine (MiNT) energy harvesting device. Another advantage of the enhanced power management system designed in this work is that the proposed approach can be utilized for extremely small energy sources and because of that the proposed work is valid for low emulated resistances. and systems with low load resistance Overall, through the successful completion of this work, various energy harvesting systems can have the ability to provide enhanced power management as the IC industry continues to progress toward miniaturization of devices and systems.

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50

Zamparette, Roger Luis Brito. "High efficiency MPPT switched capacitor DC-DC converter for photovoltaic energy harvesting aiming for IoT applications." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/173738.

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Este trabalho apresenta um conversor CC - CC baseado em Capacitores Chaveados de 6 fases e tempos intercalados com o objetivo de coletar energia fotovoltaica projetado em tecnologia CMOS de 130 nm para ser usado em aplicações em Internet das Coisas e Nós Sensores. Ele rastreia o máximo ponto de entrega de energia de um painel fotovoltaico policristalino de 3 cm x 3 cm através de modulação da frequência de chaveamento com o objetivo de carregar baterias. A razão da tensão de circuito aberto foi a estratégia de rastreio escolhida. O conversor foi projetado em uma tecnologia CMOS de 130 nm e alcança uma eficiência de 90 % para potencias de entrada maiores do que 30 mW e pode operar com tensões que vão de 1.25 até 1.8 V, resultando em saídas que vão de 2.5 até 3.6, respectivamente. Os circuitos periféricos também incluem uma proteção contra sobre tensão na saída de 3.6 V e circuitos para controle, que consomem um total máximo de potência estática de 850 A em 3.3 V de alimentação. O layout completo ocupa uma área de 300 x 700 m2 de silício. Os únicos componentes não integrados são 6x100 nF capacitores.

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