Thesis (M. Tech. Engineering: Electrical)--Vaal University of Technology / Fuel cells are electrochemical devices that convert chemical energy of a fuel cell into electricity at high efficiency without combustion. They are viewed as viable power sources for many applications including automobiles, distributed power generation and portable electronics. This dissertation presents the design and development of a phosphoric acid fuel cell. It deals with the experimental studies on phosphoric acid fuel cells and possible integration in replacing the conventional sources of electrical energy in stand-by power supply systems, particularly for use in the telecommunications industry. The design of a DC-DC converter system is also incorporated into the system. The first objective was to establish performance parameters and past studies on phosphoric acid fuel cells and this research revealed that parameters that affect the system's performance include: reactant gas pressures, mass flow rates as well as the operating temperature. Mathematical models in the literature were studied and verified against the simulation models acquired. The second objective was to design and assemble a single cell in order to analyze the cell's performances as well as the operating parameters in order to obtain a model for predicting and simulating the performance of larger fuel cell stacks. The next objective was to analyse from a set of design equations and construct a small DC-DC converter. The converter was used to boost a small fuel cell voltage and regulate it at a higher voltage level. Finally, the performance characteristics of the developed fuel cell, mathematical and simulation models were evaluated and compared. Simulation results for the models and the converter showing a regulated output voltage are presented. Some recommendations for improved system performance and for further studies are suggested.

The demand for higher efficiency and cleaner power sources increases daily. The Direct Methanol Fuel Cells (DMFC) is one of those power sources that produces reliable electrical energy at high efficiencies and very low pollution levels. Remote telecommunication sites need power sources that can deliver reliable power. This dissertation informs the reader about the working principles of the DMFC and the materials it consists of. A good amount of theoretical background is also given on the DMFC, especially on the Membrane Electrode Assembly (MEA). Different membranes as well as their properties are discussed. Results from other researchers on DMFCs are also captured. A DMFC stack including a test rig, was built. The DMFC stack consisted of five single DMFC cells. Each cell contained an MEA, Gas Diffusion Layers (GDLS), highly corrosive resistant metal support grids, bipolar flow field plates and end plates. The DMFC stack was operated and tested in a test rig. The test rig held the air blower which supplied the cathode with the required oxidant (air), and the methanol solution tank plus its liquid pump. The liquid pump circulated the methanol solution through the anode side of the stack. It was observed that the DMFC is very susceptible to corrosion, especially if the methanol solution becomes conductive owing to solubility of C02 in it. Methanol itself is a corrosive substance. However the results obtained from the experiments clearly indicate that the DMFC can be implemented as an electrical power source for telecommunications.

With the threatening of global warming and energy crises, searching for renewable and green energy resources with reduced carbon emissions is one of the most urgent challenges to the sustainable development of human civilization. In the past decades, increasing research efforts have been committed to seek for clean and renewable energy sources as well as to develop renewable energy technologies. Mechanical motion ubiquitously exists in ambient environment and people’s daily life. In recent years, it becomes an attractive target for energy harvesting as a promising supplement to traditional fuel sources and a potentially alternative power source to battery-operated electronics. Until recently, the mechanisms of mechanical energy harvesting are limited to transductions based on piezoelectric effect, electromagnetic effect, electrostatic effect and magnetostrictive effect. Widespread usage of these techniques is likely to be shadowed by possible limitations, such as structure complexity, low power output, fabrication of high-quality materials, reliance on external power sources and little adaptability on structural design for different applications. In 2012, triboelectric nanogenerator (TENG), a creative invention for harvesting ambient mechanical energy based on the coupling between triboelectric effect and electrostatic effect has been launched as a new and renewable energy technology. The concept and design presented in this thesis research can greatly promote the development of TENG as both sustainable power sources and self-powered active sensors. And it will greatly help to define the TENG as a fundamentally new green energy technology, featured as being simple, reliable, cost-effective as well as high efficiency.

M. Tech. (Electrical, Applied Electronics and Electronic Communication, Faculty of Engineering and Technology) Vaal University of Technology| / The demand for efficient and environmentally friendly power sources has become a major topic around the world. This research explores the capability of the zinc-air fuel cell to replace conventional power sources for various applications, more specifically telecommunication systems. The research consisted of a theoretical study of the zinc-air fuel cell and its components, as well as their performance characteristics. A zinc-air fuel ce.ll and test rig were built, and the system was tested under various conditions. It was found that the zinc-air fuel cell has an advantage over other fuel cells in that it does not require any expensive materials or noble metals, reducing the overall cost of such a system. The fuel cell showed the potential to power various applications, but problems persisted in the fueling process as well as constant leaking of the aqueous electrolyte.

Les problématiques énergétiques sont au sommet des préoccupations politiques dans de nombreux pays, du fait des enjeux environnementaux inhérents, du rôle moteur de l’énergie dans tous les secteurs économiques ainsi que des préoccupations relatives à l’indépendance énergétique. Cet intérêt est accru du fait de la part croissante des sources d’énergie renouvelables et intermittentes dans le mix énergétique mondial. En particulier, de par son fort potentiel et la volonté politique de soutien dont elle a bénéficié, l’énergie photovoltaïque est désormais un acteur clé dans la mutation énergétique mondiale, et son intégration dans le mix mondial doit être réalisée avec attention. Afin d’avoir une compréhension approfondie de la façon dont l’énergie solaire peut pénétrer et transformer le panorama énergétique, nous avons adopté une stratégie en trois niveaux avec une approche multidisciplinaire visant à apporter quelques réponses aux questions suivantes : i/ quel sera la position de l’énergie solaire dans le futur mix énergétique ?; ii/ du fait de son inconvénient majeur, l’intermittence, pouvons-nous fournir une architecture optimale d’une système basé sur l’énergie solaire associant des systèmes de stockage ?; iii/ quelle est l’efficacité des politiques incitatives mises en œuvre pour accélérer son déploiement ?Ainsi, dans un premier chapitre, nous analysons la position particulière de l’énergie photovoltaïque dans le mix énergétique. Après un rappel des enjeux des futurs mix énergétiques mondiaux, nous proposons une description sommaire des différentes technologies solaires et de leurs évolutions attendues en termes d’améliorations techniques et de réductions de coûts. Enfin, nous décrivons la croissance très rapide du marché photovoltaïque et de ces conséquences à la fois sur le mix électrique et sur le secteur industriel. Dans le deuxième chapitre, nous nous intéressons à la problématique de l’intégration de cette énergie intermittente dans le mix électrique, en développant une méthodologie d’évaluation multicritère ainsi qu’un outil d’optimisation multicritère sous contraintes qui permet de faire des simulations d’un système composé de panneaux photovoltaïques et de technologies de stockage. Des cas d’applications sur le cas réel du Cirque de Mafate (L’île de la Réunion, France) sont présentés pour illustrer l’intérêt de la méthode.Enfin, dans le troisième chapitre, nous questionnons l’efficacité de différentes politiques de soutien aux technologies photovoltaïques dans les pays les plus pertinents. Nous examinons plus particulièrement la corrélation entre la puissance installée, l’argent publique dépensé, ainsi que les prix de l’électricité. / The energetic issue is on the top of the political agenda in many countries, for environmental reasons, for its driving role in all the economic sectors, as well as for the energetic independency concerns. This problematic is stressed by the increasing weight of renewable intermittent power sources in the global energy mix. In particular, due to its high potential and the strong national policy support it beneficiated, solar photovoltaic energy is now a key player in the world energy mutation, and the way it is integrated into the global mix should be carefully performed. To deeply understand the way solar energy can penetrate and transform the forthcoming energy framework, we adopted a three-level strategy with an multidisciplinary approach to provide some answers to the following questions: i/ how can we situate the photovoltaic power role in future energy mixes?; ii/ due to its main drawback, intermittency, could we provide an optimal design of a system combining storage devices?; iii/ what is the efficiency of the incentive policies that are or have been implemented to accelerate its deployment?That is why, in a first chapter, the peculiar position of the solar photovoltaic energy in the energy mix is analyzed. After recalling the general issue of future global energetic mixes, we propose a brief description of the different photovoltaic technologies and their promising evolutions in terms of technical improvements and cost reductions. Then, we describe the fast growing photovoltaic market and its consequences both on the electricity mix and the industry sector.In the second chapter we investigate the issue of integrating such an intermittent energy in the electricity mix, by developing a multicriteria evaluation methodology and a multicriteria under constraint optimization tool which simulates a system composed of photovoltaic panels and storage devices. Applications on a real case in the Cirque de Mafate (L’île de la Réunion, France) are presented to illustrate the interest of our method.Finally, in chapter three, we question the efficiency of different public support policies to the photovoltaic technologies in the most relevant countries. We focus on correlating the installed power capacity with the spent public money and the electricity prices.

Thesis (M. Tech.) (Engineering: Electrical, Dept.: Electronic Engineering))--Vaal University of Technology, 2008. / The demand for higher efficiency, sustainability and cleaner power sources increases daily. A Direct Methanol Fuel Cell is a power source that can be applied for small to medium household appliances and office equipment. It can ideally be used for operating appliances like notebook computers on remote sites where no electrical power is available. One of the problems in methanol fuel cells is methanol crossover. Methanol crossover occurs when methanol is not completely used in the process of generating electrons, and a certain percentage of the methanol is wasted. Crossover may damage the proton exchange membrane of the fuel cell and reduce the efficiency of a DMFC. Literature reviews were done and suggestions from other writers are discussed on how to reduce methanol crossover. This research focuses primarily on the fact that crossover can be controlled by controlling the methanol / water concentration. A prototype methanol controller was built with an ultrasonic sensor for detecting the density of the methanol/water mixture and a sensor for the temperature of the mixture; this was done because the density of the mixture is dependant on the temperature and the concentration. The controller was calibrated to determine the amount per volume of water and methanol which enables the controller to control the percentage of methanol in the water. The prototype also had the feature built in to adjust the mixture in order to enable the study on the effects of crossover. A data logger function was added to store collected data on a personal computer for the study on methanol and water. It was observed that the sensor was sensitive enough and was able to produce 1% increments of the level of methanol concentration in the water provided the temperature was stable. A methanol controller was successfully built to ensure the correct volume of methanol. / Telkom Centre of Excellence

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A Comprehensive review of literature on electrode materials for lithium-ion batteries is provided in Chapter 1 of the thesis. Chapter 2 deals with the studies on porous, sub-micrometer size LiNi1/3Co1/3O2 as a positive electrode material for Li-ion cells synthesized by inverse microemulsion route and polymer template route. The electromechanical characterization studies show that carbon-coated LiNi1/3Co1/3O2 samples exhibit improved rate capability and cycling performance. Furthermore, it is anticipated that porous LiNi1/3Co1/3O2 could be useful for high rates of charge-discharge cycling. Synthesis of sub-micrometer size, porous particles of LiNi1/3Co1/3O2 using a tri-block copolymer as a soft template is carried out. LiNi1/3Co1/3O2 sample prepared at 900ºC exhibits a high rate capability and stable capacity retention of cycling. The electrochemical performance of LiNi1/3Co1/3O2 prepared in the absence of the polymer template is inferior to that of the sample prepared in the presence of the polymer template. Chapter 4 involves the synthesis of sub-micrometer size particles of LiMn2O4 in quaternary microemulsion medium. The electrochemical characterization studies provide discharge capacity values of about 100 mAh g-1 at C/5 rate and there is moderate decrease in capacity by increasing the rate of charge-discharge cycling. Studies also include charge-discharge cycling as well as ac impedance studies in temperature range from -10 to 40º C. Chapter 5 reports the synthesis of nano-plate LiFePO4 by polyol route starting from two reactants, namely, FePO42H2O and LiOH.2H2O. The electrodes fabricated out of nano-plate of LiFePO4 exhibit a high electrochemical activity. A stable capacity of about 155 mAh g-1 is measured at 0.2 C over 50 charge-discharge cycles. Mesoporous LiFePO4/C composite with two sizes of pores is prepared for the first time via solution-based polymer template technique. The precursor of LiFePO4/C composite is heated at different temperatures in the range from 600 to 800ºC to study the effect of crystalllinity, porosity and morphology on the electrochemical performance. The compound obtained at 700ºC exhibits a high rate capability and stable capacity retention on cycling with pore size distribution around 4 and 46nm. In Chapter 6, the electrochemical characterization of LiMn2O4 in an aqueous solution of 5 M LiNO3 is reported. A typical cell employing LiMn2O4 as the positive electrode and V2O5 as the negative electrode was assembled and the characterized by charge-discharge cycling in 5 M LiNO3 aqueous electrolyte. Furthermore, it is shown that Li+-ion in LiMn2O4 can be replaced by other divalent ions resulting in the formation of MMn2O4 (M = Ca, Mg, Ba and Sr) in aqueous M(NO3)2 electrolytes by subjecting LiMn2O4 electrodes to cyclic voltametry. Cyclic voltammetry and chronopotentiometry studies suggest that MMn2O4 can undergo reversible redox reaction by intercalation/deintercalation of M2+-ions in aqueous M(NO3)2 electrolytes.

This work deals with the deployment of distributed power sources into the electric power grid. The nature of these sources causes that the massive integration may experience problems with power quality in the local context, and also overall reliability of supply in the range of interconnected power systems may be endangered. Work is focused on local voltage quality problems with special emphasis on analysis and design of tools (e.g. reactive power compensation units of power plants or dynamic voltage control by transformers 110/22kV) for voltage control in power distribution systems. These tools should be used as a part of uniform concept of voltage control. The proposed concept is involved.

Hitachi Energy Power transformers in Ludvika wants to investigate the possibilities of developing a cutting tool to streamline one of the many processes for fabrication of windings in transformers. This thesis work at Uppsala University, which has been going on for ten weeks, has thus investigated the possibilities for a cutting tool by studying the basic necessary theories and user requirements that have consequently resulted in the generation of a proposed solution. User requirements were formulated through collection of data in the form of interviews, a questionnaire,and a literature study. Based on the collected user requirements, concepts have been generated for cutting mechanisms, followed by a concept screening for the reason of presenting a concept selection. The remaining problem statements were answered through thematic analysis of all collected information and balancing of developed user requirements. The design of a proposed solution has been done in 3D CAD with a focus on a solution-independent design This study showed that an electric battery-powered and hand-held tool with a focus on user-friendliness is advantageous for the intended application. Theoretically, the tool will improve user safety and time-consuming manual work will be minimized while reducing the risk of accidents. A theoretically functional proposed solution with a basis for all design choices has been presented to act as a basis for continued work. This study has been the first of its kind for this specific area and has thus left much room for further development, but at the same time provided a collection of information that contributes to the possible realization of a cutting tool.