Dissertations / Theses on the topic 'Energy conversion systems'
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Thorburn, Karin. "Electric Energy Conversion Systems : Wave Energy and Hydropower." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7081.
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Muralidharan, Shylesh. "Assessment of ocean thermal energy conversion." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76927.
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Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 103-109).
Ocean thermal energy conversion (OTEC) is a promising renewable energy technology to generate electricity and has other applications such as production of freshwater, seawater air-conditioning, marine culture and chilled-soil agriculture. Previous studies on the technology have focused on promoting it to generate electricity and produce energy-intensive products such as ammonia and hydrogen. Though the technology has been understood in the past couple of decades through academic studies and limited demonstration projects, the uncertainty around the financial viability of a large-scale plant and the lack of an operational demonstration project have delayed large investments in the technology. This study brings together a broad overview of the technology, market locations, technical and economic assessment of the technology, environmental impact of the technology and a comparison of the levelized costs of energy of this technology with competing ones. It also provides an analysis and discussion on application of this technology in water scarce regions of the world, emphasized with a case study of the economic feasibility of this technology for the Bahamas. It was found that current technology exists to build OTEC plants except for some components such as the cold water pipe which presents an engineering challenge when scaled for large-scale power output. The technology is capital intensive and unviable at small scale of power output but can become viable when approached as a sustainable integrated solution to co-generate electricity and freshwater, especially for island nations in the OTEC resource zones with supply constraints on both these commodities. To succeed, this technology requires the support of appropriate government regulation and innovative financing models to mitigate risks associated with the huge upfront investment costs. If the viability of this technology can be improved by integrating the production of by-products, OTEC can be an important means of producing more electricity, freshwater and food for the planet's increasing population.
by Shylesh Muralidharan.
S.M.in Engineering and Management
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Ahmed, Shehab. "Compact harsh environment energy conversion systems." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1289.
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Boström, Cecilia. "Electrical Systems for Wave Energy Conversion." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-140116.
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Wave energy is a renewable energy source with a large potential to contribute to the world's electricity production. There exist several technologies on how to convert the energy in the ocean waves into electric energy. The wave energy converter (WEC) presented in this thesis is based on a linear synchronous generator. The generator is placed on the seabed and driven by a point absorbing buoy on the ocean surface. Instead of having one large unit, several smaller units are interconnected to increase the total installed power. To convert and interconnect the power from the generators, marine substations are used. The marine substations are placed on the seabed and convert the fluctuating AC from the generators into an AC suitable for grid connection. The work presented in the thesis focuses on the first steps in the electric energy conversion, converting the voltage out from the generators into DC, which have an impact on the WEC's ability to absorb and produce power. The purpose has been to investigate how the generator will operate when it is subjected to different load cases and to obtain guidelines on how future systems could be improved. Offshore experiments and simulations have been done on full scale generators connected to four different loads, i.e. one linear resistive load and three different non-linear loads representing different cases for grid connected WECs. The results show that the power can be controlled and optimized by choosing a suitable system for the WEC. It is not obvious which kind of system is the most preferable, since there are many different parameters that have an impact on the system performance, such as the size of the buoy, how the generator is designed, the number of WECs, the highest allowed complexity of the system, costs and so on. Therefore, the design of the electrical system should preferably be carried out in parallel with the design of the WEC in order to achieve an efficient system.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 727
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Michas, Marios. "Control of turbine-based energy conversion systems." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/117586/.
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This thesis investigated the modelling and control of wind and hydrokinetic turbine-based energy conversion systems. Wind turbines are a mature technology and the technical challenges are associated with their connection to the grid. However, hydrokinetic energy conversion systems are fairly new and their design is usually based on knowledge transferred from the wind industry. Variable-speed wind turbines are either fully or partially decoupled from the frequency of the grid. Therefore, as conventional plants are decommissioned, wind turbines have to comply with requirements issued by the transmission system operator of each country. To investigate this, vector control schemes of a doubly fed induction generator (DFIG) and of a fully rated converter (FRC)-based wind turbine were modelled using MATLAB/Simulink. Simulations showed that in case of a fault at the point of connection to the grid there is a larger impact on the torque of a DFIG than a FRC-based wind turbine. In addition, the FRC-based wind turbines can increase their output to contribute to the restoration of the grid frequency. Technical knowledge from the design, control and the modelling of variable-speed wind turbines was used for the design of an electrical subsystem for a hydrokinetic energy conversion system for man-made waterways. An FRC-based configuration based on a dc-dc converter was used for the control of the laboratory prototype of a hydrokinetic energy conversion system and the derivation of its characteristic power curves. Very high efficiencies of the system were observed due to the restricted flow conditions. Similarly to wind turbines, the variable-speed operation of the hydrokinetic energy conversion system enabled its maximum power point tracking (MPPT). A gradient-based method was analysed and a ‘perturb and observe’ algorithm-based control scheme was used for the maximum power extraction. The technical challenges are associated with the selection of the sampling time of the algorithm according to the inertia of the system and the convergence speed coefficient according to the voltage constant of the generator. The laboratory prototype and the projected full-scale system were modelled and simulated. Simulation and experimental results show good agreement on achieving the MPPT of the hydrokinetic energy conversion system. These findings are very important for the future design of heuristic MPPT control schemes for hydrokinetic energy conversion systems.
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Oh, Sang Joon. "Electromagnetics of inertial energy storage systems with fast electromechanical energy conversion /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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McEnaney, Kenneth. "Thermoelectrics and aerogels for solar energy conversion systems." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97770.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.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 115-124).
Concerns about climate change, the world's growing energy needs, and energy independence are driving demand for solar energy conversion technologies. Solar thermal electricity generation has the potential to ll this demand. Solar thermal technology could also be used to displace fossil fuels in applications which require heat as an input. This thesis addresses the potential of two solar thermal technologies: solar thermoelectric generators and aerogel-based solar thermal receivers. Thermoelectrics are materials which produce a voltage when subjected to a temperature gradient. In a solar thermoelectric generator (STEG), sunlight heats one end of the thermoelectric materials, generating a voltage across the device. The voltage can be connected to a load and useful work can be extracted. By adding optical concentration and using higher-temperature materials, the power output and energy conversion eciency of STEGs can be increased. In this work, segmented thermoelectric generators (TEGs) made of bismuth telluride and skutterudite alloys are modeled, optimized, built, and tested. These TEGs achieve a heat-to-electricity conversion efficiency of 10.7% at a hot side of 550° C, the highest TEG eciency reported in this temperature range. From these TEGs, STEGs are built which achieve a sunlight-to-electricity conversion eciency of 5.7% at less than 60 suns, higher than the best reported literature values in this concentration range. With further improvements, it is projected that these STEGs will achieve 10% eciency at 100 suns. In any type of solar thermal system, heat losses from the system must be suppressed to achieve high eciency. Aerogels, which are stable ultra-low density foams, can suppress radiative and convective losses. It is shown that aerogel-based solar thermal receivers can increase the eciency of traditional solar thermal electricity and hot water generation. These results can help advance the field and expand the scope of solar thermal technologies.
by Kenneth McEnaney.
Ph. D.
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Yassin, Ali M. "Functional conjugated systems for energy conversion and storage." Angers, 2011. http://www.theses.fr/2011ANGE0080.
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Ce travail intitulé « Systèmes Conjugués Fonctionnelle pour la Conversion et le Stockage de l'Energie » porte sur la conception et la synthèse de nouvelles classes de systems π-conjugués fonctionnels pour la conversion photovoltaïque et le développement de nouveaux matériaux microporeux. Après une présentation générales de la structure et des propriétés électroniques des principales classes de systèmes conjugués et plus particulièrement des molécules conjuguées utilisées comme matériaux donneur dans les cellules solaires organiques (CSO), le second chapitre décrit la synthèse et l'étude d'une série de donneurs moléculaires obtenus par greffage de groupes dicyanovinle sur trois types de blocs conjugués rigides : carbazole cyclopentadithiophène et dithiénopyrrole (DTP). L'évaluation de ce systèmes dans des CSOs de type hétérojonction donneur-accepteur bicouche montre que le DTP conduit aux meilleurs résultats. Une étude de l'évolution des propriétés électroniques d'une série d'oligo-DTPs avec la longueur de la chaîne confirme par ailleurs l'intérêt de ce bloc donneur pour la conception de systèmes conjugués à faible bande interdite. Le chapitre suivant traite de la synthèse d'une série de molécules conjuguées de type donneur-accepteur-donneur (D-A-D) construites autour d'un cœur isoindigo ou alcoxy-cyanobithiophène et décrit une première anlyse de leurs potentialités comme matériaux donneurs dans les CSOs. Le quatrième chapitre porte sur la synhtèse d'une séries de molécules 3D issues du greffage de groupes donneurs sur une cœur quaterthiophène de géométrie quasi-tétraédrique engendrée par effet stérique et étudie les relations entre la structure des molécules la mobilité des charges positives dans les matériaux correspondants et les performances dans des CSOs. Enfin le cinquième et dernier chapitre décrit les premières étapes vers la conception et l'utilisation de molécules conjuguées 3D en vue de développer de nouvelles classes de matériaux électroactifs microporeux par polymérisation de systèmes moléculaires 3D munis de groupes terminaux réactifsThis work entitled « Functional Conjugated Systems for Energy Conversion and Storage » involves the design and synthesis of new classes of functional π-conjugated systems for photovoltaic conversion and the development of new microporous materials. After a general introduction to the structure and electronic properties of the major classes of conjugated systems and more particularly conjugated molecules used as donor material in organic solar cells (OSC), the second chapter describes the synthesis and study of a series of molecular donors obtained by grafting dicyanovinylene on three types of conjugated rigid blocks : carbazole, cyclopentadithiophene and dithienopyrrole (DTP). The evaluation of these systems in donor-acceptor bilayer heterojunction OSCs shows that the DTP leads to best results. A study of the evolution of the electronic properties, of a series of oligo-DTPs, with the chain length further confirms the interest of the donor block for low band gap conjugated systems. The next chapter deals with the synthesis of a series of conjugated molecules of donor-acceptor-donor (D-A-D) type, built around a core of isoindigo, and describes a first evaluation of their potential as donor materials in OSCs. The fourth chapter deals with the synthesis of a series of 3D molecules derived from the grafting of donor groupas on a quaterthiophene core with a quasi-tetrehedral geometry caused by steric effect, and examine the relationship between the structure of the molecules, the mobility of positive charges in these materials and their performance in OSCs. Finally the fift and last chapter describes the first steps towards the design and use of 3D conjugated molecules in order to develop new classes of electro-active materials by polymerization of microporous 3D molecular systems provided with reactive end groups
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Buehrle, Bridget Erin. "Modeling of Small-Scale Wind Energy Conversion Systems." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/50920.
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As wind turbines are increasingly being adopted for meeting growing energy needs, their implementation for personal home use in the near future is imminent. There are very few studies conducted on small-scale turbines in the one to two meter diameter range because the power generated at this scale is currently not sufficient to justify the cost of installation and maintenance. The problem is further complicated by the fact that these turbines are normally mounted at low altitudes and thus there is necessity to have the optimum operating regime in the wind speed range of 3-10 mph (1.34 -- 4.47 m/s). This thesis discusses two methods for increasing the efficiency of horizontal axis small-scale wind energy conversion systems, 1) adding a diffuser to increase the wind speed at the rotor and 2) designing tubercles to enhance the flow characteristics over blades. Further, it was identified during the course of thesis that for simple installation and maintenance in the residential areas vertical axis turbines are advantageous. Thus, the second chapter of this thesis addresses the design of vertical axis turbines with power generation capability suitable for that of a typical US household. The study of the diffuser augmented wind turbine provides optimum dimensions for achieving high power density that can address the challenges associated with small scale wind energy systems; these challenges are to achieve a lower start-up speed and low wind speed operation. The diffuser design was modeled using commercial computational fluid dynamics code. Two-dimensional modeling using actuator disk theory was used to optimize the diffuser design. A statistical study was then conducted to reduce the computational time by selecting a descriptive set of models to simulate and characterize relevant parameters\' effects instead of checking all the possible combinations of input parameters. Individual dimensions were incorporated into JMP® software and randomized to design the experiment. The results of the JMP® analysis are discussed in this paper. Consistent with the literature, a long outlet section with length one to three times the diameter coupled with a sharp angled inlet was found to provide the highest amplification for a wind turbine diffuser.
The second study consisted of analyzing the capabilities of a small-scale vertical axis wind turbine. The turbine consisted of six blades of extruded aluminum NACA 0018 airfoils of 0.08732 m (3.44 in) in chord length. Small-scale wind turbines often operate at Reynolds numbers less than 200,000, and issues in modeling their flow characteristics are discussed throughout this thesis. After finding an appropriate modeling technique, it was found that the vertical axis wind turbine requires more accurate turbulence models to appropriately discover its performance capabilities.
The use of tubercles on aerodynamic blades has been found to delay stall angle and increase the aerodynamic efficiency. Models of 440 mm (17.33 in) blades with and without tubercles were fabricated in Virginia Tech\'s Center for Energy Harvesting Materials and Systems (CEHMS) laboratory. Comparative analysis using three dimensional models of the blades with and without the tubercles will be required to determine whether the tubercle technology does, in fact, delays the stall. Further computational and experimental testing is necessary, but preliminary results indicate a 2% increase in power coefficient when tubercles are present on the blades.
Master of Science
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Trilla, Romero Lluís. "Power converter optimal control for wind energy conversion systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134602.
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L'energia eòlica ha incrementat la seva presència a molts països i s'espera que tingui encara un pes més gran en la generació elèctrica amb la implantació de la tecnologia eòlica marina. En aquest context el desenvolupament de models dels Sistemes de Generació per Turbina de Vent (SGTV) precisos és important pels operadors de xarxa per tal d'avaluar-ne el comportament. Els codis de xarxa ofereixen un seguit de normes per validar models amb dades obtingudes de proves de camp. A la primera part d'aquesta tesi un model de SGTV amb màquina d'inducció doblement alimentada (DFIG) és validat d'acord amb les normatives espanyola i alemanya. Avui dia molts parc eòlics utilitzen DFIG i, en conseqüència, les dades de camp disponibles son per aquesta tecnologia. Per a la indústria eòlica marina un avanç prometedor son els SGTV amb generadors síncrons d'imants permanents (PMSG). Per aquesta raó la segona part d'aquesta tesi es centra en SGTV basats en PMSG amb convertidor back-to-back de plena potència. Aquest convertidor es pot dividir en dues parts: el costat de xarxa (GSC) que interactua amb la xarxa elèctrica i el costat de màquina (MSC) que controla el generador.
En general, el sistema de control del convertidor recau en els tradicionals controladors PI i, en ocasions, incorpora desacoblaments per reduir les influencies creuades entre les variables. Aquest controlador pot ser sintonitzat i implementat fàcilment donat que la seva estructura és simple, però, no presenta una resposta ideal donat que no aprofita tots els graus de llibertat disponibles en el sistema. És important desenvolupar controladors fiables que puguin oferir una resposta previsible del sistema i proveir robustesa i estabilitat. En especial per zones on la presència eòlica és gran i per parcs eòlics connectats a xarxes dèbils.
En aquest treball es proposa un sistema de control pel convertidor basat en teoria de control H-infinit i en controladors Lineals amb Paràmetres Variants (LPV). La teoria de control òptim proveeix un marc de treball on més opcions es poden tenir en consideració a l'hora de dissenyar el controlador. En concret la teoria de control H-inifinit permet crear controladors multivariables per tal d'obtenir una òptima resposta del sistema, proveir certa robustesa i assegurar l'estabilitat. Amb aquesta tècnica durant la síntesi del controlador el pitjor cas de senyals de pertorbació és contemplat, d'aquesta manera el controlador resultant robustifica l'operació del sistema. Es proposa aquest control per al GSC posant especial èmfasi en obtenir un control de baixa complexitat que mantingui els beneficis d'aplicar la teoria de control òptim i faciliti la seva implementació en computadors industrials. Pel MSC es proposa una estratègia diferent basada en control LPV donat que el punt d'operació del generador canvia constantment. El sistema de control basat en LPV és capaç d'adaptar-se dinàmicament al punt d'operació del sistema, així s'obté en tot moment la resposta definida durant el procés de disseny. Amb aquesta tècnica l'estabilitat del sistema sobre tot el rang d'operació queda garantida i, a més, s'obté una resposta predictible i uniforme. El controlador està dissenyat per tenir una estructura simple, com a resultat s'obté un control que no és computacionalment exigent i es proveeix una solució que pot ser utilitzada amb equips industrials.
S'utilitza una bancada de proves que inclou el PMSG i el convertidor back-to-back per tal d'avaluar experimentalment l'estratègia de control dissenyada al llarg d'aquest treball. L'enfoc orientat a la implementació dels controls proposats facilita el seu ús amb el processador de senyals digitals inclòs a la placa de control de la bancada. Els experiments realitzats verifiquen en un ambient realista els beneficis teòrics i els resultats de simulació obtinguts prèviament. Aquestes proves han ajudat a valorar el funcionament dels controls en un sistema discret i la seva tolerància al soroll de senyals i mesuresWind energy has increased its presence in many countries and it is expected to have even a higher weight in the electrical generation share with the implantation of offshore wind farms. Consequently, the wind energy industry has to take greater responsibility towards the integration and stability of the power grid. In this sense, there are proposed in the present work control systems that aim to improve the response and robustness of the wind energy conversion systems without increasing their complexity in order to facilitate their applicability. In the grid-side converter it is proposed to implement an optimal controller with its design based on H-infinity control theory in order to ensure the stability, obtain an optimal response of the system and also provide robustness. In the machine-side converter the use of a Linear Parameter-Varying controller is selected, this choice provides a controller that dynamically adapts itself to the operating point of the system, in this way the response obtained is always the desired one, the one defined during the design process. Preliminary analysis of the controllers are performed using models validated with field test data obtained from operational wind turbines, the validation process followed the set of rules included in the official regulations of the electric sector or grid codes. In the last stage an experimental test bench has been developed in order to test and evaluate the proposed controllers and verify its correct performance.
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Anheden, Marie. "Analysis of gas turbine systems for sustainable energy conversion." Doctoral thesis, KTH, Chemical Engineering and Technology, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2914.
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Increased energy demands and fear of global warming due tothe emission of greenhouse gases call for development of newefficient power generation systems with low or no carbondioxide(CO2) emissions. In this thesis, two different gasturbine power generation systems, which are designed with theseissues in mind, are theoretically investigated and analyzed.Inthe first gas turbine system, the fuel is combusted using ametal oxide as an oxidant instead of oxygen in the air. Thisprocess is known as Chemical Looping Combustion (CLC). CLC isclaimed to decrease combustion exergy destruction and increasethe power generation efficiency. Another advantage is thepossibility to separate CO2without a costly and energy demanding gasseparation process. The system analysis presented includescomputer-based simulations of CLC gas turbine systems withdifferent metal oxides as oxygen carriers and different fuels.An exergy analysis comparing the exergy destruction of the gasturbine system with CLC and conventional combustion is alsopresented. The results show that it is theoretically possibleto increase the power generation efficiency of a simple gasturbine system by introducing CLC. A combined gas/steam turbinecycle system with CLC is, however, estimated to reach a similarefficiency as the conventional combined cycle system. If thebenefit of easy and energy-efficient CO2separation is accounted for, a CLC combined cyclesystem has a potential to be favorable compared to a combinedcycle system with CO2separation.
In the second investigation, a solid, CO2-neutral biomass fuel is used in a small-scaleexternally fired gas turbine system for cogeneration of powerand district heating. Both open and closed gas turbines withdifferent working fluids are simulated and analyzed regardingthermodynamic performance, equipment size, and economics. Theresults show that it is possible to reach high power generationefficiency and total (power-and-heat) efficiency with thesuggested system. The economic analysis reveals that the costof electricity from theEFGT plant is competitive with the moreconventional alternatives for biomass based cogeneration in thesame size range (<10 MWe).
Keywords:power generation, Chemical Looping Combustion,CO2separation, oxygen carrier, biomass fuel, closedcycle gas turbine, externally fired gas turbine
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Mendonca, Jose Manuel de Araujo Baptista. "Microcomputer on-line control of wind energy conversion systems." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38101.
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Ren, Yaxing. "Perturbation estimation based control of electric energy conversion systems." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3005548/.
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The traditional power system includes the centralised power generation, high voltage AC power transmission and three phase energy consumption. Electric energy conversion systems (ECSs) have been applied to the power generation, energy storage and power consumption to convert energy between the electric form and other forms. In the future power system, the ratio of distributed power generation and storage will have a rapid increment with the development of power electronics technology. Thus, the robustness and stability are significant to the ECSs in the future power electronics enabled power system. This thesis deals with the design and analysis with theoretical contribution, and the implementation of a perturbation estimation based nonlinear adaptive control (NAC) on ECSs, i.e. the wind turbine (WT), the energy storage system (ESS) in converter based microgrid (MG), and the induction motor (IM), respectively, in simulation and experimental validation. The wind turbine is one of the most promising distributed power generation resources. The challenge in controlling a wind turbine is its nonlinear behaviour of aerodynamics under random wind speed. This makes it difficult to obtain the optimal control performance operating under the time-varying wind speed via conventional linear control method. In addition, as the future power system including plenty of distributed generation and consumption, typically in MG application, the ESS is necessary to balance the power difference between power generation and consumption. Due to the low stiffness and inertia of an islanded MG, the challenge is the stability problem and power quality of MG under unknown disturbance and unbalanced power demand. Moreover, other than the disturbance from power generation side, plenty of unknown disturbance also appears on the power consumption. The most popular workhorse for industrial application is the induction motor (IM), which is affected by the disturbance of unknown load torque under operation. The IM has highly coupled states and nonlinear interactions between states. The conventional vector control depending on the flux position is sensitive to parameter changes. And the use of a speed encoder increases the risk in the IM speed drive in the electric vehicle application. To cope with these challenges in the ECS applications, the perturbation estimation based control method is studied and applied to improve the robustness of the ECSs for power generation, storage and consumption of the future power system. In the control method, a state and perturbation observer is used to estimate the perturbation term, which includes the nonlinear interactions between states, external disturbance, parameter changes and unmodeled dynamics. In the WT pitch angle control, a nonlinear PI-based controller is designed with a perturbation observer to estimate and compensate the system nonlinearities and disturbance of WT system. In the ESS voltage control of islanded MG, a voltage controller is designed for the ESS in MG via estimating and compensating the unknown disturbance to reduce the voltage unbalance rate. In the IM speed drive, an NAC based speed controller is investigated to control the IM directly under the stationary frame to improve its robustness under disturbance and parameter uncertainty. Another contribution is to propose a speed sensorless NAC controller with a combined SPO to control the IM without the dependency of a speed sensor. The proposed control methods are compared with the conventional methods regarding their control performance. The results show that the perturbation estimation based method can improve the robustness of ECS under disturbance and parameter uncertainty in the renewable power generation, MG bus voltage regulation, and IM speed drive. However, the great observer bandwidth can amplify the sensor noise and reduce the robustness and stability of the closed loop system. In the study, the observer and controller bandwidth is set greater than the controller bandwidth and lower than the sensor noise bandwidth, with optimised bandwidth tuned via pole placement method and the closed loop stability of the ECS systems is analysed using Lyapunov theory.
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Tsujimura, Seiya. "Studies on energy conversion systems based on bioelectrocatalytic reactions." Kyoto University, 2007. http://hdl.handle.net/2433/59291.
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Kyoto University (京都大学)0048
新制・論文博士
博士(農学)
乙第12049号
論農博第2636号
新制||農||944(附属図書館)
学位論文||H19||N4268(農学部図書室)
UT51-2007-H604
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 加納 健司, 教授 清水 昌, 教授 坂田 完三
学位規則第4条第2項該当
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Presby, Andrew L. "Thermophotovoltaic energy conversion in space nuclear reactor power systems." Thesis, Monterey, Calif. : Naval Postgraduate School, 2004. http://edocs.nps.edu/npspubs/scholarly/theses/2004/Dec/04Dec%5FPresby.pdf.
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Thesis (Astronautical Engineer and M. S. in Astronautical Engineering)--Naval Postgraduate School, December 2004.Thesis Advisor(s): Gopinath, Ashok ; Michael, Sherif. "December 2004." Description based on title screen as viewed on March 13, 2009. Includes bibliographical references (p. 123-127). Also available in print.
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FORCINETTI, RENATO. "MAGNETO-FLUID-DYNAMIC ENERGY CONVERSION SYSTEMS FOR AEROSPACE APPLICATIONS." Doctoral thesis, Università degli Studi di Cagliari, 2017. http://hdl.handle.net/11584/249563.
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The study concerns the application of Magnetohydrodynamics (MHD) to the Space flights. This field puts a number of challenging issues due both to the severe service conditions and to the launch requirements. Space vehicles are subject to radiations and are hit by high-energy particles; during the launch, the vehicle undergoes very strong vibrations, which can cause severe damages to the equipment with moving parts, such as pistons and gears, making them unsuitable for Space missions. Furthermore, the minimization of mass and volume of the on board devices is a critical aspect of the design, particularly for the energy conversion equipment, such as electric power generators, active cooling devices and propulsion systems. Any static energy conversion technology, with a high ratio power/volume and power/weight and that can adapt its shape to the vehicle, is suitable for space applications. Due to the static nature, MHD energy converters withstand the vibrations during the take-off, can work at high temperatures and, due to the limited mechanical stress during the functioning, they can be manufactured by using light materials, reducing the load. This thesis deals with two aspects of the MHD energy conversion in Space: the energy supply of the on board electrical devices and the cruise propulsion. In PART I two concepts of MHD induction generators are proposed aiming overcoming the main drawbacks of classic MHD generators, but holding all their advantages. The first is a Flowing MHD generator; a mono-dimensional Model is solved in Simulink® environment performing preliminary dimensioning and performance estimation of the generator. The second is the TA-MHD generator, a quasi-static converter combining thermoacoustics (TA) and MHD. First, a theoretical study has been developed in order to perform a coarse sizing and performance estimation for a set of parameters; then, a series of FEM simulations allowed a preliminary assessment of the behavior of the charges subject to an acoustic wave and an electric field. The charges segregated inside the capacitor’s plates, move forward and backward due to the acoustic wave and distribute in the whole cross section without sticking to the walls. The results show that the charge carriers can give rise to an alternate electric current in the fluid, which the energy conversion process is based on. The Multi-objective Tabu Search (MO-TS) algorithm has been customized in order to investigate the optimal design of the MHD section of the generator. 2D and 3D optimization problems have been solved considering as objective functions, first the power to be maximized and the voltage to be minimized, and then adding the mass to be minimized. The solutions confirm the suitability of the TA-MHD generator for aerospace but shows different optimal points, depending on the specific application. PART II deals with the MagnetoPlasmaSail (MPS), a Space propulsion concept exploiting the solar wind energy. A FEM analysis of the sail formation and inflation is conducted. The results, even if the simulation parameters are right different from the real ones, is a first step in the comprehension of the phenomenon and create the premises for a dimensionless analysis. The Magnetic Reynolds number is much greater than one, so the magnetic field is in frozen conditions (its field lines are strongly advected by the plasma). Also the Interaction Parameter is much larger than one, so that the fluid streamlines will be heavily modified by the magnetic field. Under optimum conditions this will lead to the plasma confinement inside the magnetic bubble, reinforcing the magnetic field, and allowing excellent fuel efficiency. The FEM simulation confirms the expected behavior of the magnetic field interacting with the plasma: the magnetosphere formation process is qualitatively shown as its interaction with the solar wind. The introduction of non-dimensional parameters allows extending the results to different orders of magnitude.
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Carpintero, Moreno Efrain. "Wave energy conversion based on multi-mode line absorbing systems." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/wave-energy-conversion-based-on-multimode-line-absorbing-systems(dc39c038-c89e-4243-be4c-062a6e27be5b).html.
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Wave energy conversion remains a promising technology with substantial renewable resources to be exploited in many parts of the world. However to be commercially attractive more effective conversion is desirable. There is scope for increasing power capture by use of several bodies responding with several modes, some or all of which may undergo resonance for frequencies within a wave climate. This theme is explored here with a floating moored line absorber system where the relative motion generates power by incorporation of a damper to represent the power take off. To be most effective the bodies should be responding in anti-phase requiring spacing between adjacent bodies of half a wavelength. First a converter design including two bodies is investigated experimentally and numerically responding solely in heave. The bodies have drafts to provide resonant frequencies within a wave spectrum, the stern diameter is as large as possible within the inertia regime and the bow diameter is optimised to provide maximum power. Experiments showed this system to be limited since the desirable anti phase heave modes were contaminated with other modes for off resonance response considerably reducing power generation. To stabilise motion in the desired modes another small float was introduced as the bow float rigidly connected by a beam to the mid float with the added benefit of adding forcing due to surge and pitch to some degree (following Prof Peter Stansby’s design). The sizes of the three floats increase from bow to stern, causing the line absorber to align with the wave direction. This system was optimised through experiments varying float spacing, diameter, draft and the hinge point above the mid float about which relative angular motion occurs. These experiments were undertaken at small scale in the wide Manchester University flume at about 1/40th scale. Regular and random (JONSWAP) waves were investigated including directionality and different spectral peakedness factor. Corresponding experiments were undertaken at five time larger scale (about 1/8th) in the wave basin at the COAST laboratory of Plymouth University. These tests were for a flat-based floats; the mechanical damping coefficient for larger scale was within the range for the smaller scale tests after appropriate (Froude) scaling. Tests at Manchester showed that the more rounded base floats (the mid float being hemi spherical) provided improved power capture. Device effectiveness is defined in terms of capture width ratio; that is the average power divided by the wave power per metre divided by the wavelength, defined by the energy period in the case of irregular waves. The experiments showed that capture width ratios were greater than 25% in regular waves and greater than 20% in irregular waves across a broad range of wave periods. With rounded base floats capture width ratios over 20% were achieved for a broad range of wave frequencies up to a maximum greater than 35%. Limited experiments at larger scale showed that increasing the damping coefficient could increase power capture by about 50%. Characterisation by capture width ratio is convenient for determining annual energy yield from scatter diagrams. This was undertaken for six sites of interest for wave energy conversion. It was assumed that the greatest power to weight ratio determines the most economic device; it was found that large devices could produce very large average power, for example average power of 2 MW, but the optimum power/weight ratio occurred at smaller scale, with average power typically 0.3 MW.
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Topal, Emre Tan. "A Mems Thermoelectric Energy Harvester For Energy Generation In Mobile Systems." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613636/index.pdf.
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In this thesis design, optimization, fabrication and performance characterization of MEMS thermoelectric (TE) energy harvesters for harnessing waste heat in mobile systems are presented. As a proof of concept, chromium and nickel are used as the thermoelectric material in the proposed design. The feasibility of the state of the art thermoelectric materials is also discussed.
MEMS TE energy harvesters proposed in this study are designed to generate power at relatively lower &DeltaT values. The performance of the MEMS TE energy harvesters was optimized using analytical and 3-D finite element models. An analytical code was used for profiling the electrical power output with varying geometry. The design points with maximum generated power were selected, and the microfabricated thermoelectric energy harvesters were designed accordingly. The fabricated devices are formed on a silicon wafer and composed of Nickel and Chromium thermocouples on SiO2/Si3N4 diaphragms, and Titanium heater and monitor resistors for testing purposes. Microfabrication was followed by the performance characterization of MEMS TE energy harvesters with the conducted tests. For 10 °
C temperature difference between the hot and cold junctions (a heat source at 35 °
C), the proposed TE energy harvesters are capable of providing 1.1 µ
W/cm2 power density and 1.71 V voltage. The performance of the thermoelectric generators in general is limited by Carnot cycle efficiency. Nevertheless, the validated practical performance of MEMS TE energy harvesters proposed in this thesis is comparable to other examples in literature. It is anticipated by the calculations that this design will be able to provide the highest thermoelectric efficiency factor (4.04 µ
W/K2cm2) among the lateral TE energy harvesters if thermoelectric materials having high Seebeck coefficient values (such as p-Si, n-Si, polysilicon, Bi2Te3 etc.) are used. According to the performance results, the MEMS TE energy harvesters can be implemented in mobile systems to convert waste heat into electricity. The fabrication process can be adapted to CMOS with some modifications if needed. The lateral MEMS thermoelectric energy harvesters can also be combined with vibration energy harvesters to realize multi-mode energy scavenging. For prospective study, vertical thermoelectric generator configurations are also discussed in order to further increase the power density generated. The finite element simulations for proposed vertical configurations with air and water convection were completed. The vertical TE generators proposed can supply up to 4.2 mW/cm2 with a heat source at a temperature of 310 K.
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Wu, Feng. "Modelling and control of wind and wave energy conversion systems." Thesis, University of Birmingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525483.
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The modelling and control of wind and wave energy conversion systems is carried out in this thesis. The thesis comprises two parts. The first part is focused on the modelling and control of wind conversion system while the second part is on the modelling and control of wave energy conversion system (WEe). In the first part, the small signal stability of the \\lind turbine (\VT) with doubly fed induction generator (DFIG) and the WT with direct-drive permanent magnet generator (DDPMG) an: analysed using detailed models. A parameter tuning algorithm and a nonlinear controller are proposed, respectively, to improve dynamic performance of WT with DFIG. The impacts of WT with DFIG, WT with DDPMG and WT the induction generator (lG) on power system transient stability are compared. In the second part, a new coordinate transformation is proposed for the model of Archimedes wave swing (A WS) based WEe system, the transformed model is compatible with the power system dynamic analysis. The controllers for A WS based WEe are designed so as to extract maximum power from the wave, output constant power and maintain the terminal voltage. The application of battery energy storage in smoothing the output power of WEe system is studied.
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Melville, Guy T. "Hydrodynamic and economic modelling of tidal current energy conversion systems." Thesis, Robert Gordon University, 2008. http://hdl.handle.net/10059/695.
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This thesis examines the contribution of computational modelling to the development of the tidal current energy industry, against the background of increasing commercial, government, academic and public interest. It does this through the practical application of a number of computational techniques in the areas of: 1. Tidal current analysis and prediction 2. Hydrodynamic flow modelling 3. Tidal resource analysis 4. Optimised economic modelling Appropriate survey set-up is essential in gathering data. Given this, processing the data using velocity profiles; statistical techniques; and harmonic analysis can produce valuable data for site development, device design and grid management. This work developed the application of a directional and time-dependent power coefficient and demonstrates its importance in resource evaluation from tidal flow data. It further concludes that hydrodynamic flow modelling of sites prior to development is important in determining suitable sites, given the scarcity of tidal information in the areas suitable for tidal developments. The same scarcity of data, in terms of boundary conditions, interior validation points and depth does limit the accuracy of such models. The work demonstrates that using differing resource analyses can obtain dramatically different results; and develops a correlation relating energy extraction to developed energy extraction using a one dimensional channel model. In doing so it concludes that energy resource estimates may be reduced from contemporary estimates. Overall, computational modelling of tidal current energy conversion systems can have a significant contribution to their design and site development. The most significant capital costs arise from installation, decommissioning and the turbine itself, however significant reduction in the cost of energy production can result from correct placement, array size and component selection This work contributes to knowledge in a number of areas, namely: 1. It is the first published work on survey data analysis prior to deployment of a large-scale prototype tidal current energy conversion system; 2. At the time that the work was carried out, it was the first published work considering the use of the least-squared harmonic method for prediction of energy output from a tidal current energy device; 3. It is the first work to propose a directional power coefficient in the process of resource analysis for a tidal current energy conversion system; 4. The work on economic modelling was the first to produce an optimised economic model for tidal current energy conversion systems (TCECS); 5. It is the first work to use an optimised economic model for TCECSs to demonstrate the effect of device placement on the cost of energy produced; 6. It is the first work to use an optimised economic model for TCECSs to demonstrate that the cost of energy for TCECSs is minimised by maximising the rated power, given no topographical impedence; 7. It proposes a method to determine the energy resource available including energy extraction.
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MacRae, Angus Neil. "Economic and cost engineering aspects of wind energy conversion systems." Thesis, Robert Gordon University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258961.
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Macmillan, Susan. "An appraisal of wind energy conversion systems for agricultural enterprises." Thesis, Robert Gordon University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330282.
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Zoric, I. "Multiple three-phase induction generators for wind energy conversion systems." Thesis, Liverpool John Moores University, 2018. http://researchonline.ljmu.ac.uk/8387/.
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During the past decade, there has been a considerable increase in the number of published works on multiphase machines and drives. This increased interest has been largely driven by a need for the so-called green energy, i.e. energy generated from renewable sources such as wind, and also an increased emphasis on greener means for transportation. Some of the advantages multiphase machines offer over three-phase counterparts are better fault tolerance, smaller current and power per phase, and higher frequency torque ripple. This thesis examines use of a multiphase induction generator in wind energy conversion systems (WECS). In particular, multiphase generators that comprise multiple 3-phase winding sets, where each winding set is supplied using an independent 3-phase voltage source inverter (VSI), are studied. It is claimed that these topologies offer advantages in cases where a WECS is connected to a multitude of independent ac or dc microgrids, systems where a single high-voltage dc link is needed or where a simple fault tolerance is achieved when a complete winding set is switched off. All of these examples require an arbitrary power or current sharing between winding sets. In order to achieve arbitrary current and power sharing, the control can be implemented using multi stator (MS) variables, so that the flux and torque producing currents of each winding set can be arbitrarily set. As an alternative, this thesis uses vector space decomposition (VSD) to implement the control, while individual winding set flux/torque producing currents are governed by finding the relationships between MS and VSD variables. This approach has all the advantages of both MS and VSD, i.e. access to individual winding set variables of MS and the ability to implement control in the multiple decoupled two dimensional subspaces of VSD, while heavy cross coupling between winding set variables, a weakness of MS, is avoided. Since the goal of the thesis is to present use of multiphase machines in WECS, modelling and simulation of a simple multiphase WECS in back-to-back configuration has been performed at first. All systems relevant to machine control where considered, such as grid and machine side VSIs, grid filter, indirect rotor field oriented control, current control in both flux/torque producing and non-producing subspaces, low order harmonic elimination, maximum power point tracking control, and voltage oriented control of the grid side VSI. Moreover, various WECS supply topologies were considered where developed current and power sharing would be a necessary requirement. Development of the proposed current sharing control commences with an analysis of multiple 3-phase machine modelling in terms of both MS and VSD variables. Since the actual control is implemented using decoupled VSD variables, VSD modelling has been studied in detail, resulting in an algorithm for creation of the VSD matrix applicable to any symmetrical or asymmetrical multiphase machine with single or multiple neutral points. Developed algorithm always decouples the machine into orthogonal two-dimensional subspaces and zero sequence components while making sure that all odd-order harmonics are uniquely mapped. Harmonic mapping analysis is offered as well. Next, relationship between MS and VSD variables has been developed by mapping MS variables into VSD subspaces. Since VSD matrix creation algorithm is valid for any multiphase machine, relationship between MS and VSD variables is applicable to any multiple 3-phase machine regardless of the configuration (symmetrical/asymmetrical), number of neutral points or machine type (synchronous or induction). Established relationship between MS and VSD has been used to implement current sharing control in decoupled VSD subspaces of the machine. It is shown that in order to achieve arbitrary current sharing it is only necessary to impose currents in flux/torque non-producing subspaces. Hence, total machine’s flux and torque are not affected at all. Besides verification by Matlab simulations, two topologies are experimentally investigated, a parallel machine side converter configuration and the case when a single high voltage dc link is created by cascading dc-links of the machine side VSIs. In the first case the ability of arbitrary current sharing between winding sets is validated, while the second tested topology demonstrates use of the developed control for the purpose of voltage balancing of the cascaded dc links.
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Ghosh, Suvradip. "Energy and data conversion circuits for low power sensory systems." Thesis, University of Missouri - Kansas City, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3610195.
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This dissertation focuses on the problem of increasing the lifetime of wireless sensors. This problem is addressed from two different angles: energy harvesting and data compression. Energy harvesting enables a sensor to extract energy from its environment and use it to power itself or recharge its batteries. Data compression, on the other hand, allows a sensor to save energy by reducing the radio transmission bandwidth.
This dissertation proposes a fractal-based photodiode fabricated on standard CMOS process as an energy harvesting device with increased efficiency. Experiments show that, the fractal based photodiodes are 6% more efficient compared to the conventional square shaped photodiode. The fractal shape photodiode has more perimeter-to-area ratio which increases the lateral response, improving its efficiency.
With increased efficiency, more current is generated but the open-circuit voltage still remains low (0.3V–0.45V depending on illumination condition). These voltages have to be boosted up to higher values if they are going to be used to power up any sensory circuit or recharge a battery. We propose a switched-inductor DC-DC converter to boost the low voltage of the photodiodes to higher voltages. The proposed circuit uses two on-chip switches and two off-chip Components: an inductor and a capacitor. Experiments show a voltage up to 2.81V can be generated from a single photodiode of 1mm2 area. The voltage booster circuit achieved a conversion efficiency of 59%.
Data compression was also explored in an effort to reduce energy consumption during radio transmission. An analog-to-digital converter (ADC), which can jointly perform the tasks of digital conversion and entropy encoding, has also been proposed in this dissertation. The joint data conversion/compression help savings in area and power resources, making it suitable for on-sensor compression. The proposed converter combines a cyclic converter architecture and Golomb-Rice entropy encoder. The converter hardware design is based on current-mode circuits and it was fabricated on a 0.5 μm CMOS process and tested. Experiment results show a lossless compression ratio of 1.52 and a near-lossless compression of 5.2 can be achieved for 32 × 32 pixel image.
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Deal, Michael William. "Net Primary Production in Three Bioenergy Crop Systems Following Land Conversion." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1309362383.
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Zhang, Zhen, and 張鎮. "Advanced control and analysis of energy conversion systems for electric vehicles." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206458.
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By utilizing the electric motor as the propulsion system, the electric vehicle (EV) establishes a new bridge between renewable energies and our daily life, which meanwhile has to face with a brand new technical issue, namely the energy management and conversion. Then, the performance of energy conversion systems has become a new evaluation criteria for EVs. Accordingly, this study works on the analysis and control of the EV energy conversion system, including the secure charging system via wireless power transmission (WPT), advanced driving control via electric propulsion system, and bidirectional power interface via electromagnetic interference (EMI) mitigation technique.
First, this study proposes a novel energy encryption algorithm for WPT systems. In the presented scheme, the energy can be encrypted by chaotically regulating the frequency of the power source based on the unpredictable security key. The authorized receptor can effectively receive the energy by simultaneously adjusting the circuit to decoding the encrypted energy based on the acquired security key, while the unauthorized receptor cannot obtain the energy without knowledge of the security key. In this study, both simulation and experimental results are provided to verify the feasibility of the proposed secure WPT system.
Subsequently, this study proposes a new dynamic model of EV powering steering systems, by synthetically taking into account characteristics of the electric propulsion motor, driver’s operation, and uncertain disturbances caused by irregularities of the road surface. By using various nonlinear analysis methods, the unstable chaotic behaviors can be revealed in the power steering system, especially when the vehicle turns a concern at a high speed. Additionally, a new control algorithm is designed and implemented to stabilize the EV power steering system, and corresponding validity is also mathematically proved in this study.
Thirdly, an integrated driving control system is designed based on the aforementioned dynamic analysis, which is used to enhance the stability and maneuverability performances of four-in-wheel independently-driven (4WID) EVs. By adopting the supervisor-actuator structure, the proposed driving control scheme not only effectively improves the performance of tracking reference paths, but also optimally distribute the desired yaw moment to each in-wheel motor. In this study, the mathematical proof and the simulation are both conducted to demonstrate the feasibility of the proposed integrated driving control strategy.
Lastly, this study also works on the EMI issue caused by switch-mode energy conversion devices for EVs. In this section, a new pulse-width-modulation (PWM) method is designed by utilizing the random-like sequence, aiming to suppress the conducted peaky EMI over the whole power spectrum, thereby ensuring the working performance for electronic instruments in EVs. For demonstrating the effectiveness of the proposed soft-chaoizing scheme, this study takes two exemplifications such as the electric propulsion drive system and the bidirectional power interface for vehicle-to-grid (V2G) systems.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
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Greenhut, Andrew David. "Modeling and analysis of hybrid geothermal-solar thermal energy conversion systems." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/58087.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 116-118).
Innovative solar-geothermal hybrid energy conversion systems were developed for low enthalpy geothermal resources augmented with solar energy. The goal is to find cost-effective hybrid power cycles that take advantage of the potential synergies of solar thermal and geothermal resources. One aspect is to determine the hybrid configuration that yields the highest annualized electricity generation. The levelized cost of electricity (LCOE) is estimated using equipment costing rules of thumb developed from Aspen HTFS and Aspen ICARUS software and from other sources. Detailed models for the hybrid solar-geothermal system were developed using Aspen Plus and Aspen Dynamics. Turbine flexibility relative to vapor flow rate, temperature and pressure variations was analyzed. In one scenario, a parametric steady-state study was carried out to examine the performance over the range of conditions resulting from diurnal and seasonal variations. The results of the diurnal and seasonal parametric studies were grossly weighted to approximate a typical year in Nevada, and these results led to an estimate of the annualized electricity generation. In another scenario, a dynamic model was selected from possible "greenfield" hybrid systems and used to examine the transient performance for a typical January day and a typical July day in Nevada. The dynamic model approximates the thermal inertial of the heat exchangers and the working fluids in the exchangers, solar collectors, piping and storage tanks. The dynamic model is driven with forcing functions for solar input and ambient temperature to approximate the typical winter and summer days.
(cont.) In all cases, solar energy was found to come at a higher cost per kW capacity than geothermal when the cost of geothermal wells was not considered. However, including well costs had an effect of evening out the levelized cost of electricity. Model complexity increased as more solar heat was added to existing geothermal systems, which suggests that moving a higher exergy heat source down to a lower exergy heat source is difficult, especially given the transient nature of the solar resource. The models developed in this thesis demonstrate the design decisions and complex dynamic behavior inherent in this type of hybrid system.
by Andrew David Greenhut.
S.M.
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Qiao, Huan. "Electrochemical Studies on Molten Fluoride Systems for Energy Conversion Related Applications." Kyoto University, 2003. http://hdl.handle.net/2433/148652.
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Kyoto University (京都大学)0048
新制・課程博士
博士(エネルギー科学)
甲第10334号
エネ博第70号
新制||エネ||20(附属図書館)
UT51-2003-H755
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 伊藤 靖彦, 教授 片桐 晃, 教授 尾形 幸生
学位規則第4条第1項該当
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Choudhury, Fatema A. "Heteroatom doped porous carbon for alternative energy conversion and storage systems." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5588.
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Abstract
The electrocatalysis of oxygen plays a significant role in several electrochemical energy storage and conversion systems including metal−air batteries, fuel cells, electrocatalytic and photocatalytic water splitting. The sluggish kinetics and complex reaction mechanism of this cathodic oxygen reduction reaction (ORR) affect the performance and practical application of such renewable energy technologies. To address this limiting factor, a suitable electrocatalyst is required for ORR. In general, platinum or highly dispersed Pt-based nanoparticles on carbon black are considered as the best ORR catalyst. But platinum being very scarce and expensive tends to increase the cost. Moreover, platinum-based catalysts are prone to several serious problems, including declining activity, the fuel-crossover, and poisoning effects. This has initiated overwhelming research attention towards the development of low cost ORR catalysts. Jasinski et al. pioneered in reporting that a N4-chelate complex with a transition metal could be used for electrochemical oxygen reduction. Subsequently many nonprecious ORR catalysts have been investigated so far to replace platinum which include transition metal chalcogenides, nitrogen-doped carbon nanotubes or graphene, carbon nitride, and metal-N4 chelate macrocycles (M-N4-macrocycles). However, most of these current catalysts exhibited insufficient activity and low stability in corrosive environment of fuel cells. Thus, new strategies to develop catalysts which can meet the combined requirements of low cost, high catalytic activity and long-term durability still remains a challenge.
Recently our group has reported synthesis of heteroatom doped porous carbon through chemical activation of simple monomers. The facile synthetic route, high surface areas with abundant micropores, inherent presence of heteroatoms and tunable structure/composition at the molecular level make them potential for high-performance ORR electrocatalysts. To increase the catalytic performance in both acidic and basic media, it is important to incorporate or coordinate the doped heteroatom centers with 3d transition metals such as iron or cobalt. Herein, two different synthetic strategies will be presented to synthesize transition metal-based heteroatom doped porous carbon as ORR catalyst. In the first approach, iron (III) thiocyanate as iron salts was pyrolyzed with benzimidazole to introduce sulfur along with nitrogen and iron in the porous carbon. Another synthetic approach involved hydrothermal synthesis of cobalt oxide on the surface of benzimidazole derived porous carbon. ORR can proceed via either one step four-electron reduction pathway producing water or two step two-electron reduction pathway producing HO2-, OH- and H2O2. Both of these synthesized catalysts favored 4e- reduction pathway which is energetically efficient and do not produce corrosive byproducts. The electrochemical performance of the synthesized catalyst will be analyzed by cyclic voltammetry, linear sweep voltammetry and amperometric i-t technique and compared with commercially available 20 wt% Pt based carbon in both acidic and basic media. The effect of pore size, nitrogen content, bonding configurations of nitrogen and sulfur, influence of cobalt and iron on ORR performance will also be discussed.
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Isopi, Jacopo <1990>. "Nanostructured Systems for Electrocatalysis of Reduction Reactions for Energy Conversion Applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9771/1/Tesi%20PhD%20Isopi%20Jacopo%202021.pdf.
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Oxygen Reduction Reaction (ORR) requires a platinum-based catalyst to reduce the activation barrier. One of the most promising materials as alternative catalysts are carbon-based, graphene and carbon nanotubes (CNT) derivatives. ORR on a carbon-based substrate involves the less efficient two electrons process and the optimal four electrons process. New synthetic strategies to produce tunable graphene-based materials utilizing graphene oxide (GO) as a base inspired the first part of this work.
Hydrogen Evolution Reaction (HER) is a slow process requiring also platinum or palladium as catalyst. In the second part of this work, we develop and use a technique for Ni nanoparticles electrodeposition using NiCl2 as precursor in the presence of ascorbate ligands. Electrodeposition of nano-nickel onto flat glassy carbon (GC) and onto nitrogen-doped reduced graphene oxide (rGO-N) substrates are studied.
State of the art catalysts for CO2RR requires rare metals rhenium or rhodium. In recent years significant research has been done on non-noble metals and molecular systems to use as electro and photo-catalysts (artificial photosynthesis). As Cu-Zn alloys show good CO2RR performance, here we applied the same nanoparticle electrosynthesis technique using as precursors CuCl2 and Cl2Zn and observed successful formation of the nanoparticles and a notable activity in presence of CO2. Using rhenium complexes as catalysts is another popular approach and di-nuclear complexes have a positive cooperative effect. More recently a growing family of pre-catalysts based on the earth-abundant metal manganese, has emerged as a promising, cheaper alternative. Here we study the cooperative effects of di-nuclear manganese complexes derivatives when used as homogeneous electrocatalysts, as well as a rhenium functionalized polymer used as heterogeneous electrocatalyst.
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Jain, Chinmay. "Design, control and implementation of grid tied solar energy conversion systems." Thesis, IIT Delhi, 2017. http://localhost:8080/xmlui/handle/12345678/7058.
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Li, Wenyan Kusiak Andrew. "Predictive engineering in wind energy a data-mining approach /." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/399.
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Hostettler, Jacob. "Advanced Control of Permanent Magnet Synchronous Generators for Variable Speed Wind Energy Conversion Systems." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1588620.
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Various environmental and economic factors have lead to increased global investment in alternative energy technologies such as solar and wind power. Although methodologies for synchronous generator control are well researched, wind turbines present control systems challenges not presented by traditional generation. The varying nature of wind makes achieving synchronism with the existing electrical power grid a greater challenge. Departing from early use of induction machines, permanent magnet synchronous generators have become the focus of power systems and control systems research into wind energy systems. This is due to their self excited nature, along with their high power density. The problem of grid synchronism is alleviated through the use of high performance power electronic converters. In achievement of the optimal levels of efficiency, advanced control systems techniques oer promise over more traditional approaches. Research into sliding mode control, and linear matrix inequalities with nite time boundedness and H∞ performance criteria, when applied to the dynamical models of the system, demonstrate the potential of these control methodologies as future avenues for achieving higher levels of performance and eciency in wind energy.
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Diaz, Matias. "Control of the modular multilevel matrix converter for wind energy conversion systems." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/47157/.
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The nominal power of single Wind Energy Conversion Systems has been steadily growing, reaching power ratings close to 10 MW. In the power conversion stage, medium-voltage power converters are replacing the conventional low-voltage back-to-back topology. Modular Multilevel Converters have appeared as a promising solution for Multi-MW WECSs due to their characteristics such as modularity, reliability and the capability to reach high nominal voltages. Thereby, this thesis discusses the application of the Modular Multilevel Matrix Converter to drive Multi-MW Wind Energy Conversion Systems (WECSs). The modelling and control systems required for this application are extensively analysed and discussed in this document. The proposed control strategies enable decoupled operation of the converter, providing maximum power point tracking capability at the generator-side, grid-code compliance and Low Voltage Ride Through Control at the grid-side and good steady-state and dynamic performance for balancing the capacitor voltages of the converter. The effectiveness of the proposed control strategies is validated through simulations and experimental results. Simulation results are obtained with a 10MW, 6.6 kV Modular Multilevel Matrix Converter based WECS model developed in PLECS software. Additionally, a 5 kVA downscale prototype has been designed and constructed during this Ph.D. The downscale prototype is composed of 27 H-Bridges power cells. The system is controlled using a Digital Signal Processor connected to three Field Programmable Gate Array which are equipped with 50 analogue-digital channels and 108 gate drive signals. Two programmable AMETEK power supplies emulate the electrical grid and the generator. The wind turbine dynamics is programmed in the generator-side power supply to emulate a generator operating in variable speed/voltage mode. The output port of the Modular Multilevel Matrix Converter is connected to another power source which can generate programmable grid sag-swell conditions. Simulation and experimental results for variable-speed operation, grid-code compliance, and capacitor voltage regulation have confirmed the successful operation of the Modular Multilevel Matrix Converter based WECSs. In all the experiments, the proposed control systems ensure proper capacitor voltage balancing, keeping the flying capacitor voltages bounded and with low ripple. Additionally, the performance of the generator-side and grid-side control system have been validated for Maximum Power Point Tracking and Low-Voltage Ride Through, respectively.
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Díaz, Díaz Matías David. "Control of the modular multilevel Matrix converter for wind energy conversion systems." Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/147484.
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Doctor en Ingeniería Eléctrica.
Doctor of Philosophy in Electrical and Electronic EngineeringLa potencia nominal de los Sistemas de Conversión de Energía Eólica se ha incrementado constantemente alcanzando niveles de potencia cercanos a los 10 MW. Por tanto, convertidores de potencia de media tensión están reemplazando a los convertidores Back-to-Back de baja tensión habitualmente empleados en la etapa de conversión de energía. Convertidores Modulares Multinivel se han posicionado como una solución atractiva para Sistemas de Conversión de Energía Eólica de alta potencia debido a sus buenas prestaciones. Algunas de estas prestaciones son la capacidad de alcanzar altos voltajes, modularidad y confiabilidad. En este contexto, esta tesis discute la aplicación del Convertidor Modular Matricial Multinivel para conectar Sistemas de Conversión de Energía Eólica de alta potencia. Los modelos matemáticos y estrategias de control requeridas para esta aplicación son descritos y discutidos en este documento. Las estrategias de control propuestas habilitan una operación desacoplada del convertidor, proporcionando seguimiento del máximo punto de potencia en el lado del generador eléctrico del sistema eólico, cumplimiento de normas de conexión en el lado de la red eléctrica y regulación de los condensadores flotantes del convertidor. La efectividad de las estrategias de control propuestas es validada a través de simulaciones y experimentos realizados con un prototipo de laboratorio. Las simulaciones se realizan con un Sistemas de Conversión de Energía Eólica de 10 MW operando a 6.6 kV. Dicho sistema se implementa en el software PLECS. Por otro, se ha desarrollado un prototipo de laboratorio de 6kVA durante el desarrollo de este proyecto. El prototipo de laboratorio considera un Convertidor Modular Matricial Multinivel de 27 módulos Puente-H . El sistema es controlado empleando una plataforma de control basada en una Digital Signal Processor conectada a tres tarjetas del tipo Field Programmable Gate Array que proveen de 50 mediciones análogo-digital y 108 señales de disparo. La entrada del convertidor es conectada a una fuente programable marca Ametek que emula el comportamiento de la turbina eólica. A su vez, la salida del convertidor es conectada a otra fuente programable con capacidad de producir fallas en la tensión. Los resultados obtenidos, tanto en el prototipo experimental como en simulación, confirman la operación exitosa del Convertidor Modular Matricial Multinivel en aplicaciones eólicas de alta potencia. En todos los casos, las estrategias de control propuestas aseguran regulación de la tensión en los condensadores flotantes, seguimiento del máximo punto de potencia en el lado del generador eléctrico del sistema eólico y cumplimiento de normas de conexión en el lado de la red eléctrica.
The nominal power of single Wind Energy Conversion Systems has been steadily growing, reaching power ratings close to 10MW. In the power conversion stage, medium-voltage power converters are replacing the conventional low-voltage back-to-back topology. Modular Multilevel Converters have appeared as a promising solution for Multi-MW WECSs due to their characteristics such as modularity, reliability and the capability to reach high nominal voltages. Thereby, this thesis discusses the application of the Modular Multilevel Matrix Converter (\mc) to drive Multi-MW Wind Energy Conversion Systems (WECSs). The modelling and control systems required for this application are extensively analysed and discussed in this document. The proposed control strategies enable decoupled operation of the converter, providing maximum power point tracking capability at the generator-side, grid-code compliance and Low Voltage Ride Through Control at the grid-side and good steady state and dynamic performance for balancing the capacitor voltages of the converter.\\ The effectiveness of the proposed control strategies is validated through simulations and experimental results. Simulation results are obtained with a 10MW, 6.6 kVM3C based WECS model developed in PLECS software. Additionally, a 5 kVA downscale prototype has been designed and constructed during this Ph.D. The downscale prototype is composed of 27 H-Bridges power cells. The system is controlled using a Digital Signal Processor connected to three Field Programmable Gate Array which are equipped with 50 analogue-digital channels and 108 gate drive signals. Two programmable AMETEK power supplies emulate the electrical grid and the generator. The wind turbine dynamics is programmed in the generator-side power supply to emulate a generator operating in variable speed/voltage mode. The output port of the M3C is connected to another power source which can generate programmable grid sag-swell conditions. Simulation and experimental results for variable-speed operation, grid-code compliance, and capacitor voltage regulation have confirmed the successful operation of the \mc{} based WECSs. In all the experiments, the proposed control systems ensure proper capacitor voltage balancing, keeping the flying capacitor voltages bounded and with low ripple. Additionally, the performance of the generator-side and grid-side control system have been validated for Maximum Power Point Tracking and Low-Voltage Ride Through, respectively.
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Navaporn, Kaerkitcha. "Materials design and processing development of electrospun nanofibers for energy conversion systems." Kyoto University, 2018. http://hdl.handle.net/2433/232391.
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Augustine, Chad R. "Hydrothermal spallation drilling and advanced energy conversion technologies for Engineered Geothermal Systems." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51671.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
The purpose of this research was to study the various factors affecting the economic and technical feasibility of Engineered Geothermal Systems, with a special emphasis on advanced drilling technologies. The first part of the thesis was devoted to modeling and analysis of the technologies used to develop EGS projects. Since the cost of completing wells is a major factor in determining the economic feasibility of EGS projects, it is vital to be able to accurately predict in determining the economic feasibility of EGS projects, it is vital to be able to accurately predict their costs. Historic well cost data was analyzed to identify trends, and a drilling cost index for updating historic geothermal well costs to present day costs was developed. The effects of different advanced drilling technologies on drilling costs were estimated and incorporated into a techno-economic model to estimate their impact, as well as the impact of advanced reservoir stimulation technologies, on EGS levelized electricity costs. A technical analysis of geothermal binary Rankine cycle surface power plants was also performed to determine the effect of novel working fluids on plant efficiency for both sub- and supercritical binary cycles. The objective of the second part of the thesis was the application of thermal spallation drilling to deep boreholes. Thermal spallation is the fragmentation of a brittle solid into small, disc-like flakes by rapidly heating a confined fraction of the rock. It was proposed that the necessary temperatures and heat fluxes needed to induce thermal spallation in the high pressure, high density deep borehole environment could be achieved using hydrothermal flame technologies. An autoclave reaction system was designed and constructed to create flame jets in water at a pressure of 250 bar. The temperatures of these flames were measured, and attempts were made to use the flames to spall small rock samples. The experimental system was modified to study the centerline temperature decay of supercritical water jets injected at temperatures up to 525 °C into ambient temperature water. A device for measuring the heat flux from these jets was designed, constructed, and used to determine the heat transfer coefficients of the jets impinging against a flat surface. Together, these studies indicate that the necessary temperatures and heat fluxes required to induce thermal spallation in rocks can be achieved in a deep borehole.
by Chad R. Augustine.
Ph.D.
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Riber, Marklund Anders. "Passive acoustic leak detection in energy conversion systems of sodium fast reactors." Doctoral thesis, KTH, Reaktorteknologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199415.
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Reaching the goals of Generation IV nuclear power is challenging. However, no less than six reactor concepts have been identified as capable of fulfilling the demands. Among these, the Sodium Fast Reactor (SFR), probably represents the most mature technology as about 20 SFR plants have been operated to this day. One design-specific issue of the SFR is the risk of leak and sodium-water reaction inside a steam generator. Standard monitoring is based on hydrogen detection, resulting in high sensitivity but slow response. The alternative of acoustic leak detection methods has been studied since the 1970s since they are able to respond much faster. Demonstrating low false alarm rate while detecting the fairly weak and possibly unknown acoustic signals of leaks has however proven to be difficult. Today, the CEA performs R&D, notably within the scope of the ASTRID project, with the aim of eliminating the sodium-water reaction risk. This is achieved by a Brayton cycle, using a nitrogen turbine and compact sodium-nitrogen heat exchangers. In case of a leak in this system, the low solubility of nitrogen in sodium and the high pressure in the tertiary circuit would increase the secondary pressure, locally deteriorate performance and possibly result in harmful hydrodynamic effects. Together with the risks of a potential gas leak over to the reactor, this motivates the use of leak detection also for this design. This thesis concerns passive acoustic leak detection, primarily for a SFR sodium-nitrogen heat exchanger, arguing that this method is suitable based on experiments, numerical simulations and studies on algorithms. The word “passive” here refers to a system that does not send out any signals, but rather records the noise of the plant and detects leaks as changes in this signal. The thesis covers experiments on normal operation and leak-simulating setups as well as machine-learning based detection methods intended to be of interest also for change detection in general.QC 20170109
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Muhammad, Musbahu. "High gain non-isolated DC-DC converter topologies for energy conversion systems." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3665.
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Emerging applications driven by low voltage level power sources, such as photovoltaics, batteries and fuel cells require static power converters for appropriate energy conversion and conditioning to supply the requirements of the load system. Increasingly, for applications such as grid connected inverters, uninterruptible power supplies (UPS), and electric vehicles (EV), the performance of a high efficiency high static gain power converter is of critical importance to the overall system. Theoretically, the conventional boost and buck-boost converters are the simplest non-isolated topologies for voltage step-up. However, these converters typically operate under extreme duty ratio, and severe output diode reverse recovery related losses to achieve high voltage gain. This thesis presents derivation, analysis and design issues of advanced high step-up topologies with coupled inductor and voltage gain extension cell. The proposed innovative solution can achieve significant performance improvement compared to the recently proposed state of the art topologies. Two unique topologies employing coupled inductor and voltage gain extension cell are proposed. Power converters utilising coupled inductors traditionally require a clamp circuit to limit the switch voltage excursion. Firstly, a simple low-cost, high step-up converters employing active and passive clamp scheme is proposed. Performance comparison of the clamps circuits shows that the active clamp solution can achieve higher efficiency over the passive solution. Secondly, the primary detriment of increasing the power level of a coupled inductor based converters is high current ripple due to coupled inductor operation. It is normal to interleaved DC-DC converters to share the input current, minimize the current ripple and increase the power density. This thesis presents an input parallel output series converter integrating coupled inductors and switched capacitor demonstrating high static gain. Steady state analysis of the converter is presented to determine the power flow equations. Dynamic analysis is performed to design a closed loop controller to regulate the output voltage of the interleaved converter. The design procedure of the high step-up converters is explained, simulation and experimental results of the laboratory prototypes are presented. The experimental results obtained via a 250 W single phase converter and that of a 500 W interleaved converter prototypes; validate both the theory and operational characteristics of each power converter.
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Xu, Jing. "FUNDAMENTAL STUDIES OF ELECTROCATALYTIC SYSTEMS WITH RELEVANCE TO ENERGY CONVERSION AND STORAGE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1449139728.
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Popli, Nipun. "Multi-layered Energy Conversion and Frequency Control in Complex Electric Power Systems." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/916.
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The main performance objective in an electric power grid entails timely and efficient generation and delivery to the time-varying electricity demand. As the electricity industry is witnessing proliferation of the mainstream renewables, the minute-by-minute variations in wind and solar power generation may result in temporary electricity scarcity that jeopardizes grid stability and quality of service. The evolving electricity markets are aimed at incentivizing the conventional generators to reinforce their operating flexibility. This dissertation concerns the goal of enhancing the dynamic response rates of interconnected controllable resources by means of a multi-layered fuel input control of electrically coupled heterogeneous energy conversion components. Both power engineering and large-scale control contributions are made in support of this enhancement. First, improved fuel input controls are designed to enable flexible physics-based energy conversion dynamics required by the interconnected grid. To efficiently utilize the resources load-following and regulation problems are stated. The efficacy of proposed fuel input control designs in enhancing the dynamic response rates is illustrated on IEEE 14-bus system. Second, the problem is formalized as multi-input multioutput time-varying trajectory tracking based on a decentralized spatiotemporal composite control design. The concepts of vector-Lyapunov function and singular perturbation are invoked to formalize model decompositions, over space and time, respectively. Next, the assumptions for model simplifications are relaxed and the problem of parametric uncertainty is addressed. A minimumcost resilient co-design approach is introduced for storage-sensors-communication channels in a complex electric power grid. The notion of selective strong structural fixed modes is explored as a characterization of feasible decentralized control laws for an arbitrary system realization satisfying a pre-specified structure. Finally, it is proposed that planning of generation portfolio must be driven by the objective of maintaining adequate operating flexibility in the system. The goal is to ensure sufficient ramp capacity to sustain the significant integration of intermittent renewable resources.
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Al-Qrimli, Fadhil Abbas Mehdi. "An energy conversion scheme using a permanent magnet generator and a PWM, GTO converter." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304736.
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Freas, Rosemarv M. "Analysis of required supporting systems for the Supercritical CO2 power conversion system." Thesis, Cambridge Massachusetts Institute of Technology, 2007. http://hdl.handle.net/10945/2992.
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Recently, attention has been drawn to the viability of using S-CO(2) as a working fluid in modern reactor designs. Near the critical point, CO2 has a rapid rise in density allowing a significant reduction in the compressor work of a closed Brayton Cycle. Therefore, 45% efficiency can be achieved at much more moderate temperatures than is optimal for the helium Brayton cycles. An additional benefit of the S-CO2 system is its universal applicability as an indirect secondary Power Conversion System (PCS) coupled to most GEN-IV concept reactors, as well as fusion reactors. The United States DOE's GNEP is now focusing on the liquid Na cooled primary as an alternative to conventional Rankine steam cycles. This primary would also benefit from being coupled to an S-CO2 PCS. Despite current progress on designing the S-CO2 PCS, little work has focused on the principal supporting systems required. Many of the required auxiliary systems are similar to those used in other nuclear or fossil-fired units; others have specialized requirements when CO2 is used as the working fluid, and are therefore given attention in this thesis. Auxiliary systems analyzed within this thesis are restricted to those specific to using CO2 as the working fluid. Particular systems discussed include Coolant Make-up and Storage, Coolant Purification, and Coolant Leak Detection.Contract number: N62271-97-G-0026.
US Navy (USN) author
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Ochsmann, Julian Robert [Verfasser]. "Excited-state dynamics in donor-acceptor systems for energy conversion / Julian Robert Ochsmann." Mainz : Universitätsbibliothek Mainz, 2015. http://d-nb.info/1079623396/34.
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Karakus, Uzuner Melike [Verfasser]. "Charge carrier dynamics in hybrid systems for solar energy conversion / Melike Karakus Uzuner." Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1132608430/34.
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Schutte, Adriaan Nicholaas. "A bi-directional, direct conversion converter for use in household renewable energy systems." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1726.
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Thesis (MScIng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.A bi-directional, direct conversion switch-mode converter is proposed for use in distributed household renewable energy systems. The converter is intended as the central interface between the household energy system’s low voltage Direct Current bus and the high voltage Alternating Current bus. The low voltage DC bus is connected to renewable generation and storage devices, while the high voltage AC bus is connected to the user’s equipment and the mains grid. The converter overcomes the inherent reverse-duty cycle problem associated with bi-directional converters by using a combination step-up / step-down half-bridge converter on the high voltage side of a high frequency transformer. The low voltage side of the transformer is driven by a full bridge inverter that acts as a rectifier during reverse mode. In order to control the flow of power in both directions the converter implements Average Current Mode Control. A method is developed to determine the transfer functions of common switch-mode converters by inspection alone. This method is applied to the proposed converter, and both current and voltage mode control loops are designed with the frequency response method. The control system is implemented using a Digital Signal Processor. A method of simultaneously simulating both the converter hardware and software is developed using VHDL. This method greatly reduced the development effort of the converter. The operation of the proposed converter is verified through this method of simulation. A prototype converter is constructed and successfully tested, thereby proving the viability of the proposed converter topology and control methodology.
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Vidakovič-Koch, Tanja Verfasser], and Kai [Gutachter] [Sundmacher. "Bioelectrochemical systems for energy and materials conversion / Tanja Vidakovič-Koch ; Gutachter: Kai Sundmacher." Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2019. http://d-nb.info/1219965375/34.
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Matas, Adams Alba Maria. "Semiconductor Nanoparticles as Platform for Bio-Applications and Energy Related Systems." Doctoral thesis, Universitat Rovira i Virgili, 2015. http://hdl.handle.net/10803/334391.
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Aquesta tesi està dedicada a la síntesi, caracterització i aplicacions de diferents nanomaterials que presenten la propietat de ser semiconductors.
Aquesta dividida en tres blocs, en els quals, en el primer d'ells es parla sobre quantum dots (QDs), que són nanoparticulas fluorescents la longitud d'ona d'emissió varia amb la mida. Aquests materials s'estan utilitzant últimament com a substituts dels colorants orgànics ja que presenten avantatges, la principal és que no perden la seva emissió amb el temps.
Aquests QDs han estat usats per estudiar la seva interacció amb l'or (que augmenta la seva intensitat de fluorescència), han estat encapsulats usant polímers per usar-los com a controls en citometria de flux i per silica per usar-los (un cop units a un peptido i un colorant orgànic adequat) com a detectors de fibrosi quística. Finalment també han estat usats en aquesta tesi per intentar seguir el moviment d'un receptor en plaquetes.
En el segon bloc de la tesi es parla de up conversió nanoparticles, la diferència enfront dels QDs és que s'exciten a major longitud d'ona a la que emeten, pel que són capaços d'absorbir en el infraroig i emetre en el visible, fent-ideals per a aplicacions en biologia. En aquesta tesi es van usar per a reconèixer un receptor en neutrofilos i per introduir-lo dins de hidrotalcites (material que no és reconegut pel cos com estrany) per així poder alliberar-ho en l'organisme.
Finalment, en el tercer bloc s'han sintetitzat materials per catalisis (sulfur de bismut) i per cel·les solars (òxid de titani)Esta tesis esta dedicada a la sintesis, caracterizacion y aplicaciones de diferentes nanomateriales que presentan la propiedad de ser semiconductores. Esta dividida en tres bloques, en los cuales, en el primer de ellos se habla sobre quantum dots (QDs), que son nanoparticulas fluorescentes cuya longitud de onda de emision varia con el tamaño. Dichos materiales se estan usando ultimamente como sustitutos de los colorantes organicos ya que presentan ventajas, la principal es que no pierden su emision con el tiempo. Estos QDs han sido usados para estudiar su interaccion con el oro (que aumenta su intensidad de fluorescencia), han sido encapsulados usando polimeros para usarlos como controles en citometria de flujo y por silica para usarlos (una vez unidos a un peptido y un colorante organico adecuado) como detectores de fibrosis quistica. Finalmente tambien han sido usados en esta tesis para intentar seguir el movimiento de un receptor en plaquetas. En el segundo bloque de la tesis se habla de up conversion nanoparticles, cuya diferencia frente a los QDs es que se excitan a mayor longitud de onda a la que emiten, por lo que son capaces de absorber en el infrarojo y emitir en el visible, haciendolos ideales para aplicaciones en biologia. En esta tesis se usaron para reconocer un receptor en neutrofilos y para introducirlo dentro de hidrotalcitas (material que no es reconocido por el cuerpo como extraño) para asi poder liberarlo en el organismo. Finalmente, en el tercer bloque se han sintetizado materiales para catalisis (sulfuro de bismuto) y para celdas solares (oxido de titanio).
This thesis is dedicated to the synthesis, characterization and application of different nanomaterials that are semiconductors. It is divided in three blocks, in the first one we talk about quantum dots (QDs), that are fluorescent nanoparticles whose wavelength of emission changes with size. Such materials are being used as substitutes of organic dyes, due to the many advantages they present, the main one is that the fluorescence is not lost with time. These QDs have been used to study their interaction with gold ( that increases the fluorescence intensity), they have been encapsulated with polimers to be used as controls in flow cytometry or by silica to use them as sensors for cystic fibrosis (once they have been attatched to the right polymer and dye). Finally, in this thesis, they have been also used to track the movement of a platelet receptor. In the second block we talk about up conversion nanoparticles, which only difference regarding QDs is that they are excited using a longer wavelength than the emission, so they are able to absorb in the infrared and emit in the visible range of light, making them ideal for biological applications. We have use this materials to recognice an specific receptor in neutrophils as well as to be surrounded by hydrotalcite (body friendly material) so it can be released in the organism. Finally, in the third block we have syntesized materials for catalysis (bismuth sulfide) and for solar cells (titanium oxide for perovskite solar cells).
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Motjolopane, Bokang Patrick. "A power harvesting technique to facilitate energy conversion in distributed wireless sensor networks." Thesis, Cape Peninsula University of Technology, 2008. http://hdl.handle.net/20.500.11838/1113.
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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2008.
Includes bibliographical references (leaves 67-72).Distributed wireless sensor networks (DWSNs) are applied in a variety of applications that can enhance the quality of human life or even save lives, such as in fire monitoring, where DWSN microsensors relay the exact location of the fire to water sprinkler actors to automatically extinguish the fire. Batteries are currently the predominant source of energy in DWSNs. one of the key obstacles in the adoption of DWSN technology is the limited lifetime of batteries in microsensors. Recharging or replacing depleted batteries can significantly increase costs in DWSNs. The aim of this study is to address the power challenge in DWSNs by proposing a sixteen-element equiangular spiral rectenna to ahrvest ambient microwave energy to supply indoor DWSNs. The study concludes that this rectenna model has the potential to generate power that enables long periods of operation of the DWSNs without human intervention in the power manageement process, thus reducing maintenance and administration costs. The efficiency of the rectenna model was tested in an anechoic chamber. Efficiency test results indicated that the highest efficiency of 2% for the rectenna model was achieved as 2 GHz for an ambient power of -6 dBm across a 1 K ohm load resistence. The study further concludes that the current rectenna model size of sixteen elements is a limiting factor for the deployment of DWSNs.
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Chahwan, John A. "Vanadium-redox flow and lithium-ion battery modelling and performance in wind energy applications." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100223.
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As wind energy penetration levels increase, there is a growing interest in using storage devices to aid in managing the fluctuations in wind turbine output power. Vanadium-Redox batteries (VRB) and Lithium-Ion (Li-Ion) batteries are two emerging technologies which can provide power smoothing in wind energy systems. However, there is an apparent gap when it comes to the data available regarding the design, integration and operation of these batteries in wind systems. This thesis presents suitable battery electrical models which will be used to assess system performance in wind energy applications, including efficiency under various operating conditions, transfer characteristics and transient operation. A design, sizing and testing methodology for battery integration in converter based systems is presented. Recommendations for the development of operating strategies are then provided based on the obtained results.