The emergence of microwave energy harvesting systems, commonly referred to as rectenna or Wireless Power Transfer (WPT) systems, has enabled numerous applications in many areas since their primary goal is to recycle the ambient microwave energy. In such systems, microstrip antennas are used as the main source for collecting the electromagnetic energy. In this work, a novel collector based on metamaterial particles, in what is known as a Split Ring Resonator (SRR), to harvest electromagnetic energy is presented. Such collectors are much smaller in size and more efficient than existing collectors (antennas). A feasibility study of SRRs to harvest electromagnetic energy is conducted using a full wave simulator (HFSS). To prove the concept, a 5.8 GHz SRR is designed and fabricated and then tested using a power source, an Infiniium oscilloscope and a commercially available patch antenna array. When excited by a plane wave with an H-field normal to the structure, a voltage build up of 611 mV is measured across a surface mount resistive load inserted in the gap of a single loop SRR. In addition, a new efficiency concept is introduced, taking into account the microwave-to-AC conversion efficiency which is missing from earlier work. Finally, a 9X9 SRR array is compared with a 2X2 patch antenna array, both placed in a fixed footprint. The simulation results show that the array of SRRs can harvest electromagnetic energy more efficiently and over a wider bandwidth range.

<p>Over the past decade, a significant amount of research activity has been devoted to developing electromechanical systems that can convert ambient mechanical vibrations into usable electric power. Such systems, referred to as vibratory energy harvesters, have a number of useful of applications, ranging in scale from self-powered wireless sensors for structural health monitoring in bridges and buildings to energy harvesting from ocean waves. One of the most challenging aspects of this technology concerns the efficient extraction and transmission of power from transducer to storage. Maximizing the rate of power extraction from vibratory energy harvesters is further complicated by the stochastic nature of the disturbance. The primary purpose of this dissertation is to develop feedback control algorithms which optimize the average power generated from stochastically-excited vibratory energy harvesters. </p><p>This dissertation will illustrate the performance of various controllers using two vibratory energy harvesting systems: an electromagnetic transducer embedded within a flexible structure, and a piezoelectric bimorph cantilever beam. Compared with piezoelectric systems, large-scale electromagnetic systems have received much less attention in the literature despite their ability to generate power at the watt--kilowatt scale. Motivated by this observation, the first part of this dissertation focuses on developing an experimentally validated predictive model of an actively controlled electromagnetic transducer. Following this experimental analysis, linear-quadratic-Gaussian control theory is used to compute unconstrained state feedback controllers for two ideal vibratory energy harvesting systems. This theory is then augmented to account for competing objectives, nonlinearities in the harvester dynamics, and non-quadratic transmission loss models in the electronics.</p><p>In many vibratory energy harvesting applications, employing a bi-directional power electronic drive to actively control the harvester is infeasible due to the high levels of parasitic power required to operate the drive. For the case where a single-directional drive is used, a constraint on the directionality of power-flow is imposed on the system, which necessitates the use of nonlinear feedback. As such, a sub-optimal controller for power-flow-constrained vibratory energy harvesters is presented, which is analytically guaranteed to outperform the optimal static admittance controller. Finally, the last section of this dissertation explores a numerical approach to compute optimal discretized control manifolds for systems with power-flow constraints. Unlike the sub-optimal nonlinear controller, the numerical controller satisfies the necessary conditions for optimality by solving the stochastic Hamilton-Jacobi equation.</p> / Dissertation

Un nombre croissant d’appareils électroniques portatifs et portables entraîne une demande croissante de module d’alimentation électrique durable et localisé de petite taille et de poids, et offrant une puissance de sortie élevée. En tant que choix prometteur pour l’alimentation électrique, les moissonneuses d’énergie cinétiques (REC), qui transforment les vibrations ou les mouvements ambiants en énergie électrique, sont étudiées de manière intensive ces dernières années. Les performances des RECs miniatures disponibles dans la littérature sont généralement limitées par leur taille. Les vibrations ambiantes sont généralement abondantes en basse fréquence, ce qui est également un facteur majeur limitant la puissance de sortie du REC. Afin d’améliorer la puissance de sortie, nous devrions améliorer l’efficacité de la conversion d’énergie, qui est liée au principe de transduction. Ce travail présente l’amélioration de la puissance de sortie des RECs électrostatiques basse fréquence grâce à un mécanisme de conversion de fréquence mécanique couplé par impact, et propose un modèle numérique prédictif du prototype qui prend en compte l’effet d’amortissement de l’air et les impacts dans le prototype. Un prototype est proposé avec une géométrie améliorée du module capacitif réduisant la force d’amortissement de l’air. Des approches alternatives pour ajuster les RECs à des applications variées sont proposées, y compris un REC entièrement flexible conçue pour l’électronique portable, et un REC à basse fréquence 2-D sensible aux vibrations suivant deux directions orthogonales. De plus, un système d’étiquette RFID entièrement autonome en énergie mettant en œuvre le REC à basse fréquence en tant que module d’alimentation électrique et un module de communication RFID semi-passif est présenté / A growing number of portable and wearable electronics results in an increasing demand of sustainable and localized power supply module of small size and weight, and offering high output power. As a promising choice for the power supply, Kinetic energy harvesters (KEHs), transforming the ambient vibrations or motions into electrical energy, are studied intensively in recent yeas. The performance of the miniature KEHs available in literature are generaly confined by their sized. The ambient vibrations are usually abundant in low frequency, which is also a major factor restricting the output power of the KEH. In order to enhance the power output, we should improve the energy conversion efficiency, which is related to the transduction principle. This work presents the improvement of the output power of low frequency electrostatic KEHs through impact-coupled mechanical frequency up conversion mechanism, and proposes a predictive numerical model of the prototype which considers the squeeze film air damping effect and the impacts in the prototype. A prototype is proposed with improved geometry of capacitive module reducing the air damping force. Alternative approaches to adjust the KEHs to varied applications are proposed, including a fully flexible KEH designed for wearable electronics, and a 2-D low frequency KEH that is sensible to vibrations along two orthogonal directions. In addition, a fully energy-autonomous RFID tag system implementing the low frequency KEH as the power supply module and a semi-passive RFID communication module is presented

The aim for this thesis was to investigate if harvesting of ambient radio waves could be a viable source of energy and where and when it can be used. A survey of the signal strengths at different locations in Uppsala, Sweden was performed which showed that the cellular frequency bands were the ones that carried the most energy. One circuit was manufactured and two more were simulated, together with the circuitry required to measure and display how much energy that was being harvested. The design was tested at the same locations as the survey of the signal strength was conducted at. The maximum harvested energy was 35µW which was at a location inside in a window facing a cellular transmittor with an approximate distance of 100m. At 200m away from a cellular transmitter, the output was 1µW. In a typical city environment, the output from the harvester was 0µW. The harvesting technique was also compared to energy from solar- and thermal energy. The comparison showed that it is almost always more beneficial to use an alternative source of energy, such as solar cells, even indoors.

This dissertation presents a case study which attempts to implement a passive Ultra High Frequency Radio Frequency Identification (UHF RFID) system on aircraft landing gear (LG) to permit component configuration management. It is shown that a monostatic RFID system with two reader antennas, one on the LG main fitting and one in the wing bay allows up to 64 kbits of data to be associated with each LG component. A 7 dB system margin allows data on each LG component to be updated wirelessly and will also enable a passive UHF RFID-based LG health and usage monitoring system when tags with required sensors become available. Results from an electromagnetic simulation show that when a metal is illuminated by a nearby antenna the E-field distribution close to its surface is stronger than in free space. To explore if the stronger E-field can be used to enhance the performance of a conventional passive tag, a 5 cm × 6 mm × 3.02 m aluminium bar has been selected as the tagging object and connected to the reader via an RF feed. It is shown that a conventional metal tag which has a maximum free space range of 1.3 m when mounted on a metal plate can be detected up to 30 m along the aluminium bar from the RF feed. When orientated with the long axis normal to the metal surface a conventional passive tag with a dipole antenna can efficiently harvest the E- field and can be read at least 50 m away from the antenna feed. The proposed use of metal objects as a nearfield antenna is well suited to some applications, but in others a significant wireless path is still required. In such a case, a semi-passive tag can be used. It is demonstrated that a semi-passive tag only requires 14.4 ̧&#x9d;&#x153;&#x2021;̧&#x9d;&#x2018;&#x160; to be read over 42 m in a bistatic RFID system. Such a power consumption can be easily achieved by most energy harvesting techniques. It is demonstrated that a solar-powered semi-passive tag can be read at a range of 22 m, but its performance is still limited by multipath effects. A distributed antenna system (DAS) can be used to overcome these effects by using frequency and phase hopping techniques. It is demonstrated that 50 solar-powered semi-passive tags can be read with no missed detections over a 10 m × 20 m office area with 4 dB system margin.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016. / Landfill gases, principally methane, CH4 are produced from the decomposition of the municipal solid wastes deposited on landfill sites. These gases can be captured and converted into usable energy or electricity which will assist in addressing energy needs of South Africa. Its capture also reduces the problems associated with greenhouse gases. The aim of this study is to estimate gases that can be produced from the Bellville landfill site in Cape Town. The landfill gas capacity was estimated using Intergovernmental Panel on Climate Change (IPCC) model. The IPCC model showed that 48 447m3/year of landfill gas capacity was determined only in 2013. The LFGTE process plant is designed in a manner of purifying landfill gas, which at the end methane gets up being the only gas combusted. As a matter of fact 14 544kg/year of gases which consists mainly methane gets combusted. The average energy that can be produced based on the generated landfill gas capacity (methane gas) is 1,004MWh/year. This translates to R1. 05million per year at Eskom’s current tariff of R2.86 /kWh) including sales from CO2 which is a by-product from the designed process plant. A LFGTE process plant has been developed from the gathered information on landfill gas capacity and the amount of energy that can be generated from the gas. In order, to start-up this project the total fixed capital costs of this project required amounted up to R2.5 million. On the other hand, the project made a profit amounted to R3.9million, the Net profit summed up to R1. 3million and the payback time of Landfill Gas ToEnergy (LFGTE) project is 4years.The break-even of the project is on second year of the plant’s operation. The maximum profit that this project can generate is around R1. 1million. The life span of the plant is nine years. Aspen plus indicated that about 87% of pure methane was separated from CO2 and H2S for combustion at theabsorption gas outletstream. I would suggest this project to be done because it is profitable when by-products such as CO2 sales add to the project’s revenues.

O desenvolvimento de fontes alternativas de energia, com o intuito de diminuir a poluição gerada pela queima de combustíveis fósseis, tem estimulado cientistas a procurar novos meios de converter e armazenar energia. Adicionalmente, mudanças climáticas e o crescimento populacional têm gerado uma preocupação crescente com relação à escassez de água. Atualmente, cerca de 3% do consumo global de energia elétrica é referente ao tratamento de águas residuais oriundas de zonas urbanas. A humanidade precisa encontrar meios de usar água limpa e potável de forma mais eficiente. O armazenamento de energia durante o tratamento de águas residuais pode encorajar a preservação ambiental, e desta forma, contribuir para um crescimento mais sustentável, pois pode tornar-se rentável para as indústrias que geram e tratam estes resíduos. Uma estratégia é a utilização de gradientes iônicos e, então, convertê-los em energia elétrica. Pesquisas têm sido realizadas com sistemas contendo soluções eletrolíticas, com diferentes concentrações, e utilizando ciclos eletroquímicos para produzir trabalho elétrico. Neste contexto, são propostos sistemas eletroquímicos, chamados máquinas ácido-base foto-assistidas, que possibilitam a conversão, e o armazenamento, de energia elétrica durante a neutralização de soluções ácidas mediante irradiação de luz UV. Configurações alternativas destes dispositivos permitem, também, a dessalinização de soluções salinas com a possibilidade de recuperar parte da energia utilizada no procedimento. O princípio operacional destes sistemas baseia-se na variação entrópica, oriunda da mudança nas atividades de prótons e íons alcalinos, como também, na conversão de energia eletromagnética em energia elétrica. Através de experimentos de prova de conceito, foi possível obter 108 kJ por mol de íon eletroinserido, valor que corresponde a 10,8 kJ dm-3 de solução ácida neutralizada. / The development of alternative energy sources to mitigate the pollution generated by fossil fuel combustion has stimulated the search for new ways to convert and to harvest energy. Climate change, pollution, and population growth have raised concern about water scarcity. Nowadays, about 3% of the global electricity is consumed by municipal wastewater treatment plants. Humankind has to find the means to use clean and potable water more effectively. One strategy to harvest energy is to employ an ionic gradient and then convert it into electrical energy. Researchers have recently tested systems that apply electrolytic solutions containing different salt concentrations to deliver work after electrochemical cycles. Energy harvesting during wastewater treatment should encourage environmental preservation and contribute to sustainable growth. In this context, electrochemical systems are proposed, so-called photo-assisted acid-base machines, which promote energy conversion and harvesting during acidic solution neutralization under UV irradiation. Also, alternative configurations of these systems allow the desalination of salt solutions with regain of part of the used energy. Operating principle of these machines is based upon entropic variation, associated with proton and alkali ion activity changes, and in the conversion of the electromagnetic energy into electrical energy. Proof-of-concept experiments provided 108 kJ per mol of electroinserted ion, which corresponds to 10.8 kJ dm-3 of neutralized acid solution.

The agricultural sector is an emerging application area for Wireless Sensor Networks (WSNs). This requires sensor nodes to be deployed in the outdoor environment so as to monitor pertinent natural features, such as soil condition or pest infestation. Limited energy supply and subsequent battery replacement are common issues for these agricultural sensor nodes. One possible solution is to use energy harvesting, where the ambient energy is extracted and converted into usable electrical form to energise the wireless sensors. The work presented in this thesis investigates the feasibility of using Radio Frequency (RF) energy harvesting for a specific application; that is powering a generic class of wireless ground-level, agricultural sensor networks operating in an outdoor environment. The investigation was primarily undertaken through a literature study of the subject. The first part of the thesis examines several energy harvesting/ wireless energy transfer techniques, which may be applicable to power the targeted agricultural WSN nodes. The key advantages and limitations of each technique are identified, and the rationale is being given for selecting far-field RF energy harvesting as the investigated technique. It is then followed by a theoretical-based system analysis, which seeks to identify all relevant design parameters, and to quantify their impact on the system performance. An RF link budget analysis was also included to examine the feasibility of using RF energy harvesting to power an exemplar WSN node - Zyrox2 Bait Station. The second part of the thesis focuses on the design of two energy harvesting antennas. The first design is an air-substrate-based folded shorted patch antenna (FSPA) with a solid ground plane, while the second design is a similar FSPA structure with four pairs of slot embedded into its ground plane. Both antennas were simulated, fabricated and tested inside an anechoic chamber, and in their actual operating environment - an outdoor field. In addition, a power harvester circuit, built using the commercially available off-the-shelf components, was tested in the laboratory using an RF signal generator source. The results from both the laboratory and field trial were analysed. The measurement techniques used were reviewed, along with some comments on how to improve them. Further work on the RF energy harvester, particularly on the improvement of the antenna design must be carried out before the feasibility and viable implementations for this application can be definitively ascertained.

Photoinduced electron transfer in self-assembled via axial coordination porphyrin-fullerene dyads is investigated. Fullerene functionalized with imidazole and fullerenes functionalized with pyridine are chosen as electron acceptors, while zinc pophyrin derivatives are utilized as electron donors. The electron withdrawing ability of halogen atoms make the porphyrin ring electrophilic, which explained the binding of (F20TPP)Zn with fullerene derivatives having the highest binding constant around 105M-1. Another important observation is that the fullerene imidazole binding to zinc pophyrin had higher stability than fullerene pyridine-porphyrin dyad. Computational DFT B3LYP-21G(*) calculations are used to study the geometric and electronic structures. The HOMO and LUMO was found to be located on the porphyrin and fullerene entities, respectively. Photoinduced electron transfer is investigated by the steady-state absorption and emission, differential pulse voltammetry, and nanosecond and femtosecond transient absorption studies. The measurements provided the same conclusion that the increasing number of the halogen atoms on the porphyrin ring leads to the higher binding of porphyrin-fullerene supramolecular dyads and efficient charge separation and charge recombination processes.

Nanomaterials have been served as essential building blocks in the era of nanotechnology. Nanomaterials often exhibit different properties compared to their bulk phase, due to heavily enlarged portion of surface characteristics to the bulk. Beyond the simple size- effect, nanomaterials can be classified into 0D, 1D, and 2D materials depends on the number of restricted dimensionalities. They exhibit different unique properties and transport mechanism due to the quantum confinement effect. MXenes are one of the latest additions of 2D material family that can be obtained by selective chemical etching and exfoliation of layered ternary precursors (Mn+1AXn phases). Due to the unique etch process, surface functional groups (such as oxygen, hydroxyl, fluorine, etc) are formed at the surface of MXenes. This benefits MXenes for stable aqueous dispersions due to their hydrophilic surface. The coexistence of hydrophilicity and high electrical conductivity promised MXenes in superior performance in electrochemical energy storage and electromagnetic interference shielding applications. These characteristics are equally important for electronic applications. From the synthesis of MXene suspension to thin film deposition by spray-coating and photolithography patterning of MXene films are discussed for electronic device applications of MXenes. Vacuum-assisted filtration method was used for Mo-based MXene freestanding papers for investigation of thermoelectric energy harvesting performances. Both n-type ZnO and p-type SnO thin film transistors with MXene electrical contacts (gate, source, and drain electrodes) have been demonstrated by lift-off patterning method. Their complementary metal-oxide-semiconductor (CMOS) inverter exhibits a high gain value of 80 V/V at a supply voltage of 5 V. The lift-off patterning is simple but effective method for top-contact electrode patterning. However, it has a disadvantage of remaining sidewall-like MXene residue, resulting in leakage issues in the bottom-contact transistor structure. Hence, dry-etch patterning method is developed which allows direct patterning of MXene nanosheet thin films through conventional photolithography process. The conductive MXene electrode array was integrated into a quantum dot electric double layer transistors by all solution processes, which possess impressive performance including electron mobility of 3.3 cm2/V·s, current modulation of 104, threshold voltage as low as 0.36 V at low driving gate voltage range of only 1.25 V.