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Jia, Nengyou. "Electrochemistry of proton-exchange-membrane electrolyte fuel cell (PEMFC) electrodes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0019/MQ54898.pdf.
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Mustafa, M. Y. F. A. "Design and manufacturing of a (PEMFC) proton exchange membrane fuel cell." Thesis, Coventry University, 2009. http://curve.coventry.ac.uk/open/items/272310c1-2614-c525-0f72-77c2c68cc626/1.
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This research addresses the manufacturing problems of the fuel cell in an applied industrial approach with the aim of investigating the technology of manufacturing of Proton Exchange Membrane (PEM) fuel cells, and using this technology in reducing the cost of manufacturing through simplifying the design and using less exotic materials. The first chapter of this thesis briefly discusses possible energy alternatives to fossil fuels, arriving at the importance of hydrogen energy and fuel cells. The chapter is concluded with the main aims of this study. A review of the relevant literature is presented in chapter 2 aiming to learn from the experience of previous researchers, and to avoid the duplication in the current work. Understanding the proper working principles and the mechanisms causing performance losses in fuel cells is very important in order to devise techniques for reducing these losses and their cost. This is covered in the third chapter of this thesis which discusses the theoretical background of the fuel cell science. The design of the fuel cell module is detailed in chapter 4, supported with detailed engineering drawings and a full description of the design methodology. So as to operate the fuel cell; the reactant gases had to be prepared and the performance and operating conditions of the fuel cell tested, this required a test facility and gas conditioning unit which has been designed and built for this research. The details of this unit are presented in chapter 5. In addition to the experimental testing of the fuel cell under various geometric arrangements, a three dimensional 3D fully coupled numerical model was used to model the performances of the fuel cell. A full analysis of the experimental and computational results is presented in chapter 6. Finally, the conclusions of this work and recommendations for further investigations are presented in chapter 7 of this thesis. In this work, an understanding of voltage loss mechanism in the fuel cell based on thermodynamic irreversibility is introduced for the first time and a comprehensive formula for efficiency based on the actual operating temperature is presented. Furthermore, a novel design of a 100W (PEMFC) module which is apt to reduce the cost of manufacturing and improve water and thermal management of the fuel cell is presented. The work also included the design and manufacturing of a test facility and gas conditioning unit for PEM fuel cells which will be useful in performing further experiments on fuel cells in future research work. Taking into consideration that fuel cell technology is not properly revealed in the open literature, where most of the work on fuel cells does not offer sufficient information on the design details and calculations, this thesis is expected to be useful in the manifestation of fuel cell technology. It is also hoped that the work achieved in this study is useful for the advancement of fuel cell science and technology.
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DeLashmutt, Timothy E. "Modeling a proton exchange membrane fuel cell stack." Ohio : Ohio University, 2008. http://www.ohiolink.edu/etd/view.cgi?ohiou1227224687.
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Yakisir, Dincer. "Development of gas diffusion layer for proton exchange membrane fuel cell, PEMFC." Thesis, Université Laval, 2006. http://www.theses.ulaval.ca/2006/24094/24094.pdf.
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Yakisir, Dinçer. "Development of gas diffusion layer for proton exchange membrane fuel cell, PEMFC." Master's thesis, Université Laval, 2006. http://hdl.handle.net/20.500.11794/18765.
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Tan, Chiuan Chorng. "A new concept of regenerative proton exchange membrane fuel cell (R-‐PEMFC)." Thesis, La Réunion, 2015. http://www.theses.fr/2015LARE0012.
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Les travaux précédents trouvés dans la littérature ont mis l'importance sur la pile à combustible PEM ou électrolyseur PEM. Certains articles ont étudié également la pile à combustible réversible et le système d'alimentation en hydrogène par énergie solaire en intégrant à la fois la pile à combustible et électrolyseur. Contrairement à un « Unitised regenerative fuel cell (URFC)», notre conception a un compartiment individuel pour chaque système de PEM-Fuel Cell et d'electrolyseur-PEM et nommé Quasi - URFC. Grâce à ce nouveau concept, l'objectif principal est de réduire le coût de la pile à combustible régénératrice (RFC) en minimisant le rapport de surface superficielle géométrique du catalyseur de l'assemblage membrane électrodes (AME) des deux modes dans la cellule. D'ailleurs, nous visons également à construire un RFC plus compact, léger et portable par rapport à une pile à combustible ou l'électrolyseur classique. Ce travail de recherche est divisé en trois parties : la modélisation et simulation numérique, l'assemblage du prototype et le travail d'expérimentation. Quant à la partie de modélisation, un modèle physique multi-2D a été développé dans le but d'analyser les performances d'une pile à combustible à régénérée à trois-compartiments, qui se compose d'une piles à combustible et d'électrolyseur. Ce modèle numérique est basée sur la résolution des équations de conservation de masse, du momentum, des espèces et du courant électrique en utilisant une approche par éléments finis sur des grilles 2D . Les simulations permettent le calcul de la vitesse, de la concentration de gaz, la densité de courant et les distributions de potentiels en mode pile à combustible et en mode d'électrolyse, ainsi nous aider à prédire le comportement de quasi - RFC. En outre, l'assemblage du premier prototype du nouveau concept de pile à combustible à combustible régénérée a été achevée et testée au cours des trois années d'études dans le cadre d'une thèse. Les résultats expérimentaux de la 3 Compartiments R-PEMFC ont été prometteurs dans les deux modes, soit en mode piles à combustible et soit en mode d'électrolyseur. Ces résultats valideront ensuite les résultats de la simulation, obtenus auparavant par la modélisationThe past works found in the literature have focused on either PEM fuel cell or electrolyzer-PEM. Some of the papers even studied the unitised reversible regenerative fuel cell (URFC) and the solar power hydrogen system by integrating both fuel cell and electrolyzer. Unlike the URFC, our design has an individual compartment for each PEMFC and E-PEM systems and named Quasi-URFC. With this new concept, the main objective is to reduce the cost of regenerative fuel cell (RFC) by minimizing the ratio of the catalyst’s geometric surface area of the membrane electrode assembly (MEA) of both cell modes. Apart from that, we also aim to build a compact, light and portable RFC.This research work is divided into three parts: the modeling, assembly of the prototype and the experimentation work. As for the modeling part, a 2D multi-physics model has been developed in order to analyze the performance of a three chamber-regenerative fuel cell, which consists of both fuel cell and electrolyzer systems. This numerical model is based on solving conservation equations of mass, momentum, species and electric current by using a finite-element approach on 2D grids. Simulations allow the calculation of velocity, gas concentration, current density and potential's distributions in fuel cell mode and electrolysis mode, thus help us to predict the behavior of Quasi-RFC. Besides that, the assembly of the first prototype of the new concept of regenerative fuel cell has been completed and tested during the three years of PhD studies. The experimental results of the Three-Chamber RFC are promising in both fuel cell and electrolyzer modes and validate the simulation results that previously obtained by modeling
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Sethi, Amrit. "A Prognostics and Health Monitoring Framework for Self-Humidified Proton Exchange Membrane Fuel Cell Stacks." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25556.
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Proton exchange membrane fuel cells (PEMFCs) systems are of considerable interest in clean energy research because of their advantages. Self-humidified PEMFCs, specifically, are noteworthy since they can operate without many of the auxiliary components present in traditional PEMFC configurations. However, cost, performance issues, and short lifetimes limit their widespread usage, prompting the need for a prognostics and health monitoring (PHM) framework. Novel methods are developed and compared against those in literature to address issues specific to self-humidified PEMFCs. The framework is developed using the following steps:
-Find suitable features for health diagnosis: Health monitoring (HM) strategies applied to externally humidified PEMFC systems are compared to determine their suitability to self-humidified systems. A relative health scale is also developed to address the absence of suitable state-of-health definitions for self-humidified PEMFCs operating in real-world applications.
-Develop an HM framework for the stack: A data-driven framework based on Gaussian process regression (GPR) is developed. The framework provides estimations for the system’s current health. The framework can provide uncertainty measurements, and variational learning is used to reduce the associated computational cost. An alternative model is also developed that can work with less training data.
-Develop a hybrid probabilistic prognostics methodology: Data from the HM framework is repurposed to build a steady-state diagnostics (SSD) model of the stack. The SSD model can adapt to the highly fluctuating performance of self-humidified stacks. This SSD model is then used to provide basic prognostics predictions, which, when combined with a modified Gaussian process–Long short-term memory (GP-LSTM) network, forms a powerful generative prognostics model suitable for self-humidified PEMFC systems operating under dynamic loads. The hybrid model also provides an uncertainty estimate.
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Armstrong, Kenneth Weber. "A Microscopic Continuum Model of a Proton Exchange Membrane Fuel Cell Electrode Catalyst Layer." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/10080.
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A series of steady-state microscopic continuum models of the cathode catalyst layer (active layer) of a proton exchange membrane fuel cell are developed and presented. This model incorporates O₂ species and ion transport while taking a discrete look at the platinum particles within the active layer. The original 2-dimensional axisymmetric Thin Film and Agglomerate Models of Bultel, Ozil, and Durand [8] were initially implemented, validated, and used to generate various results related to the performance of the active layer with changes in the thermodynamic conditions and geometry. The Agglomerate Model was then further developed, implemented, and validated to include among other things pores, flooding, and both humidified air and humidified O₂. All models were implemented and solved using FEMAP™ and a computational fluid dynamics (CFD) solver, developed by Blue Ridge Numerics Inc. (BRNI) called CFDesign™. The use of these models for the discrete modeling of platinum particles is shown to be beneficial for understanding the behavior of a fuel cell. The addition of gas pores is shown to promote high current densities due to increased species transport throughout the agglomerate. Flooding is considered, and its effect on the cathode active layer is evaluated. The model takes various transport and electrochemical kinetic parameters values from the literature in order to do a parametric study showing the degree to which temperature, pressure, and geometry are crucial to overall performance. This parametric study quantifies among a number of other things the degree to which lower porosities for thick active layers and higher porosities for thin active layers are advantageous to fuel cell performance. Cathode active layer performance is shown not to be solely a function of catalyst surface area but discrete catalyst placement within the agglomerate.Master of Science
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Agarwal, Rohit. "Preparation and Characterisation of Stabilized Nafion/Phosphotungstic Acid Composite Membranes for Proton Exchange Membrane Fuel Cell (PEMFC) Automobile Engines." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4236.
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Membrane durability is one of the limiting factors for proton exchange membrane fuel cell (PEMFC) commercialisation by limiting the lifetime of the membrane via electrochemical / mechanical / thermal degradation. Lower internal humidity in the membrane at high temperature (>100 oC) and low relative humidity (25-50 %RH) operating conditions leads to increased resistance, lowering of performance and higher degradation rate. One of the promising candidates is composite proton exchange membranes (CPEMs) which have heteropoly acid (HPA) e.g. Phosphotungstic acid (PTA) doped throughout the Nafion® matrix. HPA is primarily responsible for carrying intrinsic water which reduces the external water dependence. The role of relative humidity during membrane casting was studied using surface analysis tools such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermo-gravimetric analysis (TGA), and Scanning electron microscopy (SEM) / Energy dispersive spectrometer (EDS). Membrane casting at lower relative humidity (30% approx.) results in finer size, and better PTA incorporation in the composite membrane. The effect of increase in PTA concentration in the Nafion matrix was studied with regards to conductivity, performance and durability. In-plane conductivity measurements were performed at 80 oC and 120 oC. During theses measurements, relative humidity was varied from 20% to 100% RH. Membrane conductivity invariably increases on increasing the relative humidity or operating temperature of the cell. Membrane conductivity increases with increasing PTA content from 3% to 25% PTA but never reaches the conductivity of membrane with 0% PTA. Possible explanation might be the role of cesium in PTA stabilisation process. Cesium forms a complex compound with PTA inside host matrix, rendering the PTA incapable of holding water. In plane conductivity measurements only measure surface conductivity, hence another reason might be the existence of a PTA skin on the membrane surface which is not truly representative of the whole membrane. XRD revealed that the structure of the composite membrane changes significantly on addition of PTA. Membrane with 3% PTA has structure similar to Nafion® and does not exhibit the characteristic 25o and 35o 2Ө peaks while membrane with 15% PTA and 25% PTA have strong characteristic PTA peaks. Also the membrane structure with 25% PTA matches well with that of PTA.6H2O. By applying the Scherer formula, PTA particle size was calculated from Full width half maximum (FWHM) studies at 17o 2Ө peak of the membranes. Particles coalesce on increasing the PTA concentration in the membrane leading to larger particles but still all particles were in nanometer range. Also the FWHM of membranes decreased at 17o 2Ө peak on increasing the PTA concentration, leading to higher crystallinity in the membrane. Structure analysis by FTIR indicated increase in PTA signature intensity dips, as the PTA concentration in membrane increases from 0-25%. Also by FTIR studies, it was found that some PTA is lost during the processing step as shown by comparison of as cast and protonated spectra. Possible reasoning might be that some amount of PTA does not gets cesium stabilized which gets leached away during processing. TGA studies were performed which showed no signs of early thermal degradation (temperature >300 oC); hence the assumption that all membranes are thermally robust for intended fuel cell applications. The membranes with different amounts of PTA were then catalyst coated and tested for 100-hour at open circuit voltage (OCV), 30% RH and 90 oC. By increasing the PTA in the host Nafion® matrix, the percent change in fuel crossover decreases, percent change in ECA increases, cathode fluoride emission rate decreases, and percent change in OCV decreases after the 100 hour test. Possible reasons for decreasing percentage of fuel crossover might be the increased internal humidity of the membrane due to increasing PTA incorporation. It is reported that during higher relative humidity operation, there is decrease in fuel crossover rate. Increasing ECA percentage loss might be due to the fact that HPA in the membrane can get adsorbed on the catalyst sites, rendering the sites inactive for redox reaction. Decrease in cathode fluorine emission rate (FER) might be due to the fact that there is more water available internally in the membrane as compared to Nafion®. It is reported that at higher relative humidity, FER decreases. ECA and crossover both contribute to the OCV losses. Higher component of OCV is crossover loss, which results in mixed potentials. Hence decreasing percentage of crossover might be the reason behind the decreasing OCV loss. Initial performance of fuel cell increases with increasing PTA concentration, but after the 100 hour test, higher PTA membrane exhibited highest performance loss. Increasing initial fuel cell performance can be due to the lowering of resistance due to PTA addition. Increasing ECA losses might be responsible for the increasing performance losses on adding more PTA to host membrane.M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr MSMSE
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Oyarce, Alejandro. "Electrode degradation in proton exchange membrane fuel cells." Doctoral thesis, KTH, Tillämpad elektrokemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-133437.
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The topic of this thesis is the degradation of fuel cell electrodes in proton exchange membrane fuel cells (PEMFCs). In particular, the degradation associated with localized fuel starvation, which is often encountered during start-ups and shut-downs (SUs/SDs) of PEMFCs. At SU/SD, O2 and H2 usually coexist in the anode compartment. This situation forces the opposite electrode, i.e. the cathode, to very high potentials, resulting in the corrosion of the carbon supporting the catalyst, referred to as carbon corrosion. The aim of this thesis has been to develop methods, materials and strategies to address the issues associated to carbon corrosion in PEMFC.The extent of catalyst degradation is commonly evaluated determining the electrochemically active surface area (ECSA) of fuel cell electrode. Therefore, it was considered important to study the effect of RH, temperature and type of accelerated degradation test (ADT) on the ECSA. Low RH decreases the ECSA of the electrode, attributed to re-structuring the ionomer and loss of contact with the catalyst.In the search for more durable supports, we evaluated different accelerated degradation tests (ADTs) for carbon corrosion. Potentiostatic holds at 1.2 V vs. RHE were found to be too mild. Potentiostatic holds at 1.4 V vs. RHE were found to induce a large degree of reversibility, also attributed to ionomer re-structuring. Triangle-wave potential cycling was found to irreversibly degrade the electrode within a reasonable amount of time, closely simulating SU/SD conditions.Corrosion of carbon-based supports not only degrades the catalyst by lowering the ECSA, but also has a profound effect on the electrode morphology. Decreased electrode porosity, increased agglomerate size and ionomer enrichment all contribute to the degradation of the mass-transport properties of the cathode. Graphitized carbon fibers were found to be 5 times more corrosion resistant than conventional carbons, primarily attributed to their lower surface area. Furthermore, fibers were found to better maintain the integrity of the electrode morphology, generally showing less degradation of the mass-transport losses. Different system strategies for shut-down were evaluated. Not doing anything to the fuel cell during shut-downs is detrimental for the fuel cell. O2 consumption with a load and H2 purge of the cathode were found to give around 100 times lower degradation rates compared to not doing anything and almost 10 times lower degradation rate than a simple air purge of the anode. Finally, in-situ measurements of contact resistance showed that the contact resistance between GDL and BPP is highly dynamic and changes with operating conditions.Denna doktorsavhandling behandlar degraderingen av polymerelektrolytbränslecellselektroder. polymerelektrolytbränslecellselektroder. Den handlar särskilt om nedbrytningen av elektroden kopplad till en degraderingsmekanism som heter ”localized fuel starvation” oftast närvarande vid uppstart och nedstängning av bränslecellen. Vid start och stopp kan syrgas och vätgas förekomma samtidigt i anoden. Detta leder till väldigt höga elektrodpotentialer i katoden. Resultatet av detta är att kolbaserade katalysatorbärare korroderar och att bränslecellens livslängd förkortas. Målet med avhandlingen har varit att utveckla metoder, material och strategier för att både öka förståelsen av denna degraderingsmekanism och för att maximera katalysatorbärarens livslängd.Ett vanligt tillvägagångsätt för att bestämma graden av katalysatorns degradering är genom mätning av den elektrokemiskt aktiva ytan hos bränslecellselektroderna. I denna avhandling har dessutom effekten av temperatur och relativ fukthalt studerats. Låga fukthalter minskar den aktiva ytan hos elektroden, vilket sannolikt orsakas av en omstrukturering av jonomeren och av kontaktförlust mellan jonomer och katalysator.Olika accelererade degraderingstester för kolkorrosion har använts. Potentiostatiska tester vid 1.2 V mot RHE visade sig vara för milda. Potentiostatiska tester vid 1.4 V mot RHE visade sig däremot medföra en hög grad av reversibilitet, som också den tros vara orsakad av en omstrukturering av jonomeren. Cykling av elektrodpotentialen degraderade istället elektroden irreversibelt, inom rimlig tid och kunde väldigt nära simulera förhållandena vid uppstart och nedstängning.Korrosionen av katalysatorbäraren medför degradering av katalysatorn och har också en stor inverkan på elektrodens morfologi. En minskad elektrodporositet, en ökad agglomeratstorlek och en anrikning av jonomeren gör att elektrodens masstransportegenskaper försämras. Grafitiska kolfibrer visade sig vara mer resistenta mot kolkorrosion än konventionella kol, främst p.g.a. deras låga ytarea. Grafitiska kolfibrer visade också en förmåga att bättre bibehålla elektrodens morfologi efter accelererade tester, vilket resulterade i lägre masstransportförluster.Olika systemstrategier för nedstängning jämfördes. Att inte göra något under nedstängning är mycket skadligt för bränslecellen. Förbrukning av syre med en last och spolning av katoden med vätgas visade 100 gånger lägre degraderingshastighet av bränslecellsprestanda jämfört med att inte göra något alls och 10 gånger lägre degraderingshastighet jämfört med spolning av anoden med luft. In-situ kontaktresistansmätningar visade att kontaktresistansen mellan bipolära plattor och GDL är dynamisk och kan ändras beroende på driftförhållandena.
QC 20131104
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de, la Torre Jorge. "FUEL CELLS: HYPE OR REALITY? OVERVIEW OF FUEL CELL TECHNOLOGIES FEASIBILITY STATUS WITH AN EMPHASIS ON AUTOMOTIVE AND RESIDENTIAL PROTON EXCHANGE MEMBRANE FUEL CELLS (PEMFCs)." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1309540374.
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Radhakrishnan, Arjun. "Thermal conductivity measurement of gas diffusion layer used in PEMFC /." Online version of thesis, 2009. http://hdl.handle.net/1850/10839.
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Castanheira, Luis Filipe Rodrigues. "Corrosion of high surface area carbon supports used in proton-exchange membrane fuel cell electrodes." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI084/document.
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Cette thèse est consacrée à l’étude des mécanismes de dégradation de noirs de carbone de forte surface spécifique (HSAC) utilisés comme supports d’électrocatalyseurs dans une pile à combustible à membrane échangeuse de protons (PEMFC). Nous avons montré que le mécanisme et les cinétiques de la corrosion électrochimique du carbone (COR) sont influencés par la présence d’ionomère Nafion®, la limite supérieure de potentiel électrochimique, la nature et le nombre de caractérisations intermédiaires présentes dans des tests de dégradation accélérés. En utilisant la spectroscopie Raman,il apparaît que la COR est sensible à la structure cristallographique des HSAC et procède plus rapidement sur les domaines désordonnés (carbone amorphe, cristallites de graphite présentant des défauts). Le taux de recouvrement en espèces oxygénées évalué par spectroscopie de photoélectrons X a été comparé à celui trouvé en intégrant l’intensité du pic quinone/hydroquinone (Q/HQ) envol tampérométrie cyclique. Finalement, une comparaison avec des matériaux carbonés ayant fonctionné pendant 12860 heures en PEMFC confirme nos principaux résultats et permet d’élaborer des stratégies pour atténuer les conséquences de la CORThis thesis investigates the degradation mechanism of high surfacearea carbon (HSAC) supports used in proton-exchange membrane fuel cell (PEMFC) electrodes. The structural and the chemical properties of different HSAC supports were established. The effectof the Nafion® ionomer used as a proton conductor, the gas atmosphere, the upper potential limit and the intermediate electrochemical characterizations used to monitor the changes ofthe electrochemical surface area during accelerated stress tests(ASTs) were investigated. The long-term physical and chemical changes of Pt/HSAC electrocatalysts were investigated insimulated PEMFC operating conditions. Using Raman spectroscopy, we showed that the COR is strongly structure sensitive and proceeds more rapidly on disordered domains of the HSAC (amorphous carbon and defective graphite crystallites) thanon graphitic domains. The coverage with carbon surface oxides was investigated with X-ray photoelectron spectroscopy and bridged tothe intensity of the quinone/hydroquinone (Q/HQ) peak monitored by cyclic voltammetry. Finally, the analyses realized on membrane electrode assemblies operated for 12,860h disclosed a perfect agreement between model and real PEMFC operating conditions, and confirmed the structural dependency of the COR kinetics
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Chen, Cheng. "Membrane degradation studies in PEMFCs." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29712.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Fuller, Thomas; Committee Member: Beckham, Haskell; Committee Member: Hess, Dennis; Committee Member: Koros, William; Committee Member: Meredith, Carson. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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De, Beer Chris. "Dynamic modelling and emulation of a high temperature proton exchange membrane fuel cell (HT PEMFC)." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10330.
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Includes bibliographical references (p. 152-157).Fuel cells (FC) are power sources that convert chemical energy into electrical and thermal energy in a clean and efficient manner. In the 21st century, fuel cells appear poised to meet the power demands of a variety of applications, ranging from portable electronics to utility power plants. Compared to systems utilizing fossil fuels, fuel cells offer greater efficiency and superior reliability. In particular, proton exchange membrane FCs (PEMFCs) presents a good alternative energy source for distributed generation (DG) systems. FCs however, have had limited commercial success despite their performance, durability and low environmental impact in comparison to other energy conversion and power generation devices. This lack of success has led to low commercial production levels resulting in high costs. Therefore, an increase in research and development is being conducted with the aim of producing cost effective, more efficient and reliable fuel cells for portable transportation and stationary applications. This dissertation aims to produce an emulator design for a HT PEM FC system. A model is developed that takes into account the steady state and the dynamic characteristics of the fuel cell. The emulator hardware is developed from first principles and tested to evaluate performance under dynamic operating conditions. Phenomena such as polarization curve hysteresis and fuel starvation is investigated, simulated and reproduced with the emulator system. The experimental results are compared with that of an actual HT PEM FC stack and evaluated. It was shown that the final system is able to deliver accurate steady state and transient state outputs when compared with the fuel cell stack. The final design can be used for hardware in the loop applications, specifically for fuel cell power conditioning system development.
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Wang, Hang. "Synthesis and Characterization of Multiblock Copolymers for Proton Exchange Membrane Fuel Cells (PEMFC)." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/26026.
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Nanophase-separated hydrophilic-hydrophobic multiblock copolymers are promising proton exchange membrane (PEM) materials due to their ability to form various morphological structures which enhance transport.
Four arylene chlorides monomers (2,5-Dichlorobenzophenone and its derivatives) were first successfully synthesized from aluminum chloride-catalyzed, Friedel-Crafts acylation of benzene and various aromatic compounds with 2,5-dichlorobenzoyl chloride. These monomers were then polymerized via Ni (0)-catalyzed coupling reaction to form various high molecular weight substituted poly(2,5-benzophenone)s. Great care must be taken to achieve anhydrous and inert conditions during the reaction.
A series of poly(2,5-benzophenone) activated aryl fluoride telechelic oligomers with different block molecular weights were then successfully synthesized by Ni (0)- catalyzed coupling of 2,5-dichloro-benzophenone and the end-capping agent 4-chloro-4'-fluorobenzophenone or 4-chlorophenly-4â -fluorophenyl sulfone. The molecular weights of these oligomers were readily controlled by altering the amount of end-capping agent. These telechelic oligomers (hydrophobic) were then copolymerized with phenoxide terminated disulfonated poly (arylene ether sulfone)s (hydrophilic) by nucleophilic aromatic substitution to form novel hydrophilic-hydrophobic multiblock copolymers.
A series of novel multiblock copolymers with number average block lengths ranging from 3,000 to 10,000 g/mol were successfully synthesized. Two separate Tgs were observed via DSC in the transparent multiblock copolymer films when each block length was longer than 6,000 g/mol (6k). Tapping mode atomic force microscopy (AFM) also showed clear nanophase separation between the hydrophilic and hydrophobic domains and the influence of block length, as one increased from 6k to 10k. Transparent and creasable films were solvent-cast and exhibited good proton conductivity and low water uptake.
These PAES-PBP multiblock copolymers also showed much less relative humidity (RH) dependence than random sulfonated aromatic copolymers BPSH 35 in proton conductivity, with values that were almost the same as Nafion with decreasing RHs. This phenomenon lies in the fact that this multiblock copolymer possesses a unique co-continuous nanophase separated morphology, as confirmed by AFM and DSC data. Since this unique co-continuous morphology (interconnected channels and networks) dramatically facilitates the proton transport (increase the diffusion coefficient of water), improved proton conductivity under partially hydrated conditions becomes feasible. These multiblock copolymers are therefore considered to be very promising candidates for high temperature proton exchange membranes in fuel cells.Ph. D.
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Dyantyi, Noluntu. "Factors influencing fuel cell life and a method of assessment for state of health." University of the Western Cape, 2018. http://hdl.handle.net/11394/6753.
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Philosophiae Doctor - PhDProton exchange membrane fuel cells (PEMFC) converts chemical energy from the electrochemical reaction of oxygen and hydrogen into electrical while emitting heat, oxygen depleted air (ODA) and water as by-products. The by-products have useful functions in aircrafts, such as heat that can be used for ice prevention, deoxygenated air for fire retardation and drinkable water for use on board. Consequently, the PEMFC is also studied to optimize recovery of the useful products. Despite the progress made, durability and reliability remain key challenges to the fuel cell technology. One of the reasons for this is the limited understanding of PEMFC behaviour in the aeronautic environment. The aim of this thesis was to define a comprehensive non-intrusive diagnostic technique that provides real time diagnostics on the PEMFC State of Health (SoH). The framework of the study involved determining factors that have direct influence on fuel cell life in aeronautic environment through a literature survey, examining the effects of the factors by subjecting the PEMFC to simulated conditions, establishing measurable parameters reflective of the factors and defining the diagnostic tool based on literature review and this thesis finding.
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BALDO, WILIANS R. "Desenvolvimento de um metodo de preparacao de conjuntos eletrodo - membrana - eletrodo para celulas a combustivel a membrana trocadora de protons (PEMFC)." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11079.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Al-Asad, Dawood Khaled Abdullah. "The design and evaluation of a water delivery system for evaporative cooling of a proton exchange membrane fuel cell." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1814.
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Carrère, Pierre. "Modelling and numerical simulation of water transfer in Proton Exchange Membrane Fuel Cells." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0123.
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La gestion de l’eau dans les piles à combustible à membrane d’échange de proton (PEMFC) est une problématique principale pour assurer leur efficacité et leur durabilité. La couche de diffusion côté cathode est considérée comme l’un des composants critiques concernant cette problématique. Dans ce contexte, l’objectif principal de la thèse est d’améliorer la compréhension des mécanismes intervenants dans la formation et le transport de l’eau dans la couche dediffusion côté cathode. Pour ce faire, un modèle en réseau de pores d’injection mixte liquidevapeur (MIPNM) est développé. Ce nouveau modèle permet de simuler la formation et le transport de l’eau dans la couche de diffusion côté cathode sur une plus large gamme de conditions de fonctionnement de la pile (température, densité de courant et humidité relative dans le canal) qu’avec les modèles des travaux précédents. Différents régimes de formation et de transport del’eau sont identifiés et décrits. Dans une seconde partie, le travail de thèse se focalise sur l’impact du traitement hydrophobe de la couche de diffusion. Les couches de diffusion actuellement commercialisées sont rendues hydrophobes en déposant une couche de polytétrafluoroéthylène (PTFE) sur les fibres de carbones hydrophiles. Il a été observé que le revêtement peut être non uniforme sur des couches de diffusion neuves et que le revêtement peut se dégrader au cours dufonctionnement de la pile. L’impact de ces deux phénomènes sur la distribution de l’eau liquide et sur l’accès du gaz réactif jusqu’à la couche catalytique est étudié en utilisant le modèle MIPNM pour des réseaux à mouillabilité mixte. Dans une troisième partie, un travail visant à l’amélioration de l’efficacité des piles est réalisé. Le but est d’optimiser l’accès du gaz réactif jusqu’à la couche catalytique en modifiant la microstructure des couches de diffusion. Ce travail est réalisé en couplant le modèle en réseau de pore avec un algorithme génétique. En complément, la modification des propriétés de mouillabilité des couches de diffusion est étudiée dans le but d’améliorer l’accès du gaz réactif. Enfin, un modèle 1D de tout l’assemblage anode-cathode est développé pour prendre en compte à la fois les conditions de fonctionnement à la cathode et à l’anode. Ce modèle 1D est couplé au MIPNM afin d’évaluer l’impact des conditions de fonctionnement côté anode sur la distribution d’eau liquide dans la couche de diffusion côté cathodeWater management is considered as a key issue in order to improve Proton Exchange Membrane Fuel Cells efficiency and durability. One of the critical components regarding this issue is the athode Gas Diffusion Layer (GDL). In this context, the main goal of the PhD work is to improve the understanding of the mechanisms responsible for the liquid water formation and transport in the cathode GDL. To this end, a Mixed liquid-vapour Injection Pore Network Model (MIPNM) is developed. This new model enables one to simulate the liquid water formation and transport in the cathode GDL for a larger range of operating conditions (temperature, current density and channel relative humidity) than in previous works. Different regimes of water formation and transport are identified and described. In a second part, the PhD work focus on the impact of the GDL hydrophobic treatment. Currently commercialized GDLs are rendered hydrophobic by coating Polytetrafluoroethylene (PTFE) onto the hydrophilic carbon fibres. It has been reported that the coating can be nonuniform on fresh GDLs and also that the coating can be altered during the operation of the fuel cell. The impact of these two phenomena on the liquid water distribution and on the reactant gas access to the catalyst layer is studied using the MIPNM for mixed wettability networks. In a third part, a work aiming at the improvement of PEMFC efficiency is developed. The goal is to optimise the reactant gas access to the catalyst layer by modifying the microstructure of GDLs. This is performed by coupling the PNM with a genetic algorithm. In a complementary study, the improvement of the reactant gas access is studied through modifications of the GDL wettability properties. Finally, a 1D model of the whole anode-cathode assembly is developed so as to take into account both anode and cathode operating conditions. This 1D model is coupled with the MIPNM in order to assess the impact of the anode operating conditions on the liquid water distribution in the cathode GDL
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BONIFACIO, RAFAEL N. "Desenvolvimento de processo de produção de conjuntos eletrodo-membrana-eletrodo para células a combustível baseadas no uso de membrana polimérica condutora de protons (PEMFC) por impressão a tela." reponame:Repositório Institucional do IPEN, 2010. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9520.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Wu, Yiming. "Long term performance prediction of proton exchange membrane fuel cells using machine learning method." Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0308/document.
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Les questions environnementales, en particulier le réchauffement de la planète en raison de l'effet de serre, estdevenu de plus en plus critique au cours des dernières décennies. Candidate potentielle parmi les différentessolutions alternatives d'énergie verte pour le développement durable, la pile à combustible à membrane échangeusede protons (PEMFC en anglais) a fait l'objet de nombreux travaux de recherche, dans les domaines de l'énergie etdes transports. Les PEMFC peuvent produire de l'électricité directement à partir de la réaction électrochimique entrel'hydrogène et l'oxygène de l'air, avec comme seul sous-produits de l'eau et de la chaleur. Si l'hydrogène est produità partir de sources d'énergie renouvelables, cette conversion de l'énergie est complètement écologique.Cependant, la durée de vie relativement courte des PEMFC fonctionnant dans des conditions dynamiques (pour lesvéhicules, par exemple) empêche son utilisation massive. La prévision précise de leurs mécanismes devieillissement peut ainsi aider à concevoir des modèles de maintenance appropriés des PEMFC en fournissant desinformations prévisibles sur la dégradation des performances. De plus, la prédiction pourrait également contribuer àatténuer la dégradation indésirable des systèmes PEMFC en cours d'exploitation. Ces travaux proposent unenouvelle approche guidée par les données pour prédire la dégradation des performances des PEMFC en utilisantune méthode d'apprentissage améliorée (Relevance Vector Machine : RVM).Tout d'abord, la description théorique des PEMFC en fonctionnement est présentée. Ensuite, une illustrationdétaillée de l'impact des conditions opérationnelles sur la performance des PEMFC est exposée, ainsi que desmécanismes de dégradation de chaque composant des PEMFC.Une méthode de prédiction de performance en utilisant la RVM améliorée est ensuite proposée et démontrée. Lesrésultats de prédiction basés sur des zones d'apprentissage différentes à partir des données historiques sontégalement discutés et comparés avec les résultats de prédiction utilisant les machines à vecteurs de support(Support Vector Machine : SVM).En outre, une méthode de prédiction RVM à noyau auto-adaptatif (Self-Adaptive Kernel) est présentée. La matricede conception de la formation du RVM est également modifiée afin d'acquérir une plus grande précision lors de laprédiction. Les résultats de la prévision sont illustrés et discutés en détails.En résumé, ces travaux permettent de discuter principalement de l'analyse de la prédiction de la performance desPEMFC en utilisant des méthodes d'apprentissage statistiqueThe environmental issues, especially the global warming due to greenhouse effect, has become more and morecritical in recent decades. As one potential candidate among different alternative "green energy" solutions forsustainable development, the Proton Exchange Membrane Fuel Cell (PEMFC) has been received extensiveresearch attention since many years for energy and transportation applications. The PEMFC stacks, can produceelectricity directly from electrochemical reaction between hydrogen and oxygen in the air, with the only by-productsof water and heat. If the hydrogen is produced from renewable energy sources, this energy conversion is 100% ecofriendly.However, the relatively short lifespan of PEMFCs operating under non-steady-state conditions (for vehicles forexample) impedes its massive use. The accurate prediction of their aging mechanisms can thus help to designproper maintenance patterns of PEMFCs by providing foreseeable performance degradation information. In addition,the prediction could also help to avoid or mitigate the unwanted degradation of PEMFC systems during operation.This thesis proposes a novel data driven approach to predict the performance degradation of the PEMFC using animproved relevance vector machine method.Firstly, the theoretical description of the PEMFC during operation will be presented followed by an extensivelydetailed illustration on impacts of operational conditions on PEMFC performance, along with the degradationmechanisms on each component of PEMFC. Moreover, different approaches of PEMFC performance prediction inthe literature will also be briefly introduced.Further, a performance prediction method using an improved Relevance Vector Machine (RVM) would be proposedand demonstrated. The prediction results based on different training zones from historical data will also bediscussed and compared with the prediction results using conventional Support Vector Machine (SVM).Moreover, a self-adaptive kernel RVM prediction method will be introduced. At the meantime, the design matrix ofthe RVM training will also be modified in order to acquire higher precision during prediction. The prediction resultswill be illustrated and discussed thoroughly in the end.In summary, this dissertation mainly discusses the analysis of the PEMFC performance prediction using advancedmachine learning methods
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SANTOS, ANTONIO R. dos. "Análise por impedância eletroquímica 'on line' de conjuntos eletrodo/membrana (MEA) de células a combustível a membrana polimérica (PEMFC)." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11617.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
FAPESP:03/08041-6
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Pereira, Franck. "Elaboration par voie sol-gel de membranes hybrides organique-inorganique pour application en pile à combustible PEMFC." Paris 6, 2006. http://www.theses.fr/2006PA066645.
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ZHENG, WEIBO. "Pore-Scale Simulation of Cathode Catalyst Layers in Proton Exchange Membrane Fuel Cells (PEMFCs)." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555436163992345.
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ANDRADE, ALEXANDRE B. de. "Desenvolvimento de conjuntos eletrodo-membrana-eletrodo para células a combustível a membrana trocadora de prótons (PEMFC) por impressão à tela." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11713.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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CUNHA, EDGAR F. da. "Avaliacao e aplicacao de tecnologias de celulas a combustivel tipo PEMFC desenvolvidas no IPEN em um modulo de 500 Wsub(e) de potencia nominal." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9401.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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PAULINO, ANDRE L. dos R. "Estudo da geometria de canais de fluxo em células a combustível tipo PEMFC utilizando fluidodinâmica computacional." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23598.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Mougenot, Mathieu. "Elaboration et optimisation d'électrodes de piles PEMFC à très faible taux de platine par pulvérisation plasma." Phd thesis, Université d'Orléans, 2011. http://tel.archives-ouvertes.fr/tel-00667739.
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Cette thèse réalisée dans le cadre des projets PIE CNRS AMELI-0Pt et AMEPlas et ANR AMADEUS a regroupé plusieurs entités autour de la thématique des piles à combustible : Dreux Agglomération puis l'Agence Innovation Made In Dreux (MID), le GREMI, le LACCO et initialement l'industriel MHS Equipment. L'objectif de ce travail est l'élaboration par voie plasma et l'optimisation d'électrodes de piles à combustible de type PEMFC et SAMFC dans le but d'obtenir de bonnes performances avec des charges de platine ultra faibles ou sans platine. Le projet a été organisé en quatre étapes : l'étude de la croissance simultanée de platine et de carbone co-pulvérisés par plasma, la dispersion optimale de quantités ultra faibles de catalyseur, le remplacement du platine par un alliage bimétallique à base de palladium, et le dépôt direct du catalyseur sur la membrane par plasma. En utilisant un faisceau synchrotron de rayons X (Synchrotron SOLEIL), en collaboration avec le CRMD, l'étude GISAXS des couches minces Pt-C co-pulvérisés a révélé l'organisation particulière du platine dans ce type de nanostructure. Ces couches minces Pt-C offrent d'excellentes performances (20 kW.gPt-1) avec des charges de platine ultra faibles. Des électrodes PdPt (5 %at Pt) faiblement chargées permettent d'atteindre de bonnes performances en PEMFC quasiment sans platine (12,5 kW.gPd-1 et 250 kW.gPt-1). L'étude de l'activité de catalyseurs PdAu vis-à-vis de l'oxydation du glycérol a révélé l'origine des effets synergiques du palladium et de l'or en milieu alcalin. Le dépôt plasma direct de platine associé ou non au dépôt de carbone sur membrane a été optimisé. Les performances obtenues avec des CCM (Catalyst Coated Membrane) plasma démontrent l'intérêt de ce type d'architecture.
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GRECO, Giorgia. "Study of the atomic structure and morphology of the Pt3Co nanocatalyst for applications in proton exchange membrane fuel cells (PEMFC)." Doctoral thesis, Università degli Studi di Camerino, 2010. http://hdl.handle.net/11581/401867.
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The thesis reports about a detailed investigation of the local structure and chemical disorder of a commercially available Pt-Co alloy nanocatalyst. This material, supported on high surface area carbon electrodes, is used in proton exchange membrane fuel cells (PEMFC) diminishing the amount of noble metal needed for those devices. Various state-of-the art material science techniques have been used to study microscopic properties of those nanomaterials, including XAS (X-ray Absorption Spectroscopy) ex-situ and in-situ (in an operating PEMFC), XRD (X-Ray Diffraction), high resolution TEM (Transmission Electron Microscopy), XRF (X-Ray Fluorescence). High-quality XAS spectra at the Co K-edge and Pt L3-edge were obtained using original procedures both at BM29 (European Synchrotron Radiation Facility, Grenoble) and XAFS beamline at ELETTRA (Trieste). XAS double-edge multiplescattering structural refinements of the Pt-Co spectra have been performed accounting for the reduction of the coordination numbers and degeneracy of three-atom configurations, resulting from the measured size distribution obtained by TEM and XRD. This robust approach for nanomaterial characterization, combining different techniques, can be in principle applied for structural refinements of any binary nanocrystalline functional system, including those for energy-related applications. In particular, XAS spectra are shown to be sensitive to the degree of chemical disorder in the alloy, here analyzed through an order parameter s related to the deviation from a chemically ordered crystalline compound (s=1). The initial nanocrystals are only partially ordered (s-0.6) and become more ordered as an effect of ageing when used as a catalyst in PEMFCs. Moreover, interatomic Pt-Pt and Pt-Co distances are found to be slightly longer for higher current densities and working time in operating PEMFCs, while distance variances (σ2) tend to reduce. The small amount of Co oxide initially present is found to disappear gradually in operating PEMFCs. We have also found, combining XRD, XAS, and XRF data, that the stoichiometry of the considered alloy changes from the initial value Pt-3Co (similar to that of the stable compound Pt3Co) to Pt-4Co during and after controlled cycles of usage within PEMFCs. No substantial aggregation processes increasing the sizes of the nanoparticles are observed for these alloys, in contrast with what happens pure Pt nanoparticles. The degradation of the PEMFC performances appears thus to be related to specific changes of the microscopic structural properties of the nanocatalysts, occurring under the typical operating conditions of the PEMFC. Correlations between structural properties and performances and possible consequences on the selection and optimization of the nanomaterials are briefly discussed.
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Brunello, Giuseppe. "Computational modeling of materials in polymer electrolyte membrane fuel cells." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48937.
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Fuel cells have the potential to change the energy paradigm by allowing more efficient use of energy. In particular, Polymer Electrolyte Membrane Fuel Cells (PEMFC) are interesting because they are low temperature devices. However, there are still numerous challenges limiting their widespread use including operating temperature, types of permissible fuels and optimal use of expensive catalysts. The first two problems are related mainly to the ionomer electrolyte, which largely determines the operating temperature and fuel type. While new ionomer membranes have been proposed to address some of these issues, there is still a lack of fundamental knowledge to guide ionomer design for PEMFC.
This work is a computational study of the effect of temperature and water content on sulfonated poly(ether ether ketone) and the effect of acidity on sulfonated polystyrene to better understand how ionomer material properties differ. In particular we found that increased water content preferentially solvates the sulfonate groups and improves water and hydronium transport. However, we found that increasing an ionomer’s acid strength causes similar effects to increasing the water content.
Finally, we used Density Functional Theory (DFT) to study platinum nano-clusters as used in PEMFCs. We developed a model using the atom’s coordination number to quickly compute the energy of a cluster and therefore predict which platinum atoms are most loosely held. Our model correctly predicted the energy of various clusters compared to DFT. Also, we studied the interaction between the various moieties of the electrolyte including the catalyst particle and developed a force field.
The coordination model can be used in a molecular dynamics simulation of the three phase region of a PEMFC to generate unbiased initial clusters. The force field developed can be used to describe the interaction between this generated cluster and the electrolyte.
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Piga, Matteo. "New hybrid inorganic-organic proton conducting membranes for PEMFC: synthesis, properties and conduction mechanisms." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3421723.
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Electrochemical devices for the conversion of chemical energy into electrical power, such as proton exchange membrane fuel cells (PEMFCs), are of intense interest to industry and the scientific community because of their high energy conversion efficiency, low environmental impact, and the possibility for use in a wide variety of applications from portable electronic devices to light-duty electric vehicles. At the core of the fuel cell is a PEM that allows the transport of hydrogen ions, evolved at the anode, to the cathode where oxygen is reduced to water. Todays prevalent PEMs feature perfluorinated main chains functionalized with perfluoroether side chains terminated with acidic -SO3H groups. These materials (DupontTM Nafion®, Asashi Aciplex®, Dow®, and Flemion®) generally are characterized by a high chemical, thermal and mechanical stability; they also exhibit good proton conductivity at high levels of hydration. The hydration requirements limit the widespread commercial use of conventional PEMs, which have inadequate proton conductivity at temperatures above 90C and at low values of relative humidity. Fuel cells capable of operating above 120C at low levels of hydration would: obviate the need of bulky and expensive water management modules, simplify thermal management; and reduce the impact of catalyst poisons such as carbon monoxide. In an effort to overcome the limitations of conventional PEMs, this work reports the synthesis and characterization of new proton conducting membrane alternatives to classic fluorinated polymers for application in PEMFCs. The materials were synthesized according to two distinct strategies: 1) dope a Nafion membrane in order to improve its thermo-mechanical properties and proton conductivity or extend its operating conditions to temperatures above 100°C and an anhydrous environment; 2) synthesize and characterize proton exchange membranes based on polybenzimidazole and polysulfone as an alternative to perfluorinated polymers.
The first point regarded the study of two different systems obtained by doping a Nafion membrane with the [(ZrO2)(Ta2O5)0.119] inorganic “core-shell” nanofiller or with two different proton conducting ionic liquids, triethylammonium methanesulfonate and triethylammonium perfluorobutanesulfonate. The study of new PEMs alternative to fluorinated polymers has been developed considering polybenzimidazole and sulfonated poly(p-phenylenesulfone) membranes whose properties have been modulated by the addition of phosphoric acid and an hybrid filler or poly(1-oxotrimethylene) and silica, respectively. All the proposed materials were extensively characterized in terms of their thermal, mechanical, structural and electrical properties in order to highlight the interactions between the different components present within the membranes. These interactions govern the membranes macroscopic properties that need to be improved in order to optimize and predict the behavior of these materials under operating conditions in fuel cells.Celle a combustibile basate su membrane a scambio protonico (PEMFCs) sono dispositivi elettrochimici per la conversione di energia chimica in energia elettrica. Le PEMFCs suscitano notevole interesse sia nel mondo industriale che accademico a causa della loro elevata efficienza di conversione, basso impatto ambientale e vasta gamma di utilizzo che spazia dall’elettronica portatile fino all’autotrazione. All’interno della cella a combustibile si trova la membrana a scambio protonico (PEM), che consente il trasferimento di protoni dall’anodo al catodo. Attualmente le membrane polimeriche a scambio protonico maggiormente utilizzate sono costituite da polimeri fluorurati funzionalizzati con gruppi polieterei terminanti con gruppi acidi (tipicamente -SO3H). Questi materiali (DupontTM Nafion®, Asashi Aciplex®, Dow®, and Flemion®) generalmente presentano elevata stabilità chimica, termica e meccanica ma tuttavia mostrano valori di conducibilità sufficienti per il loro impiego in cella a combustibile solo per elevati livelli di idratazione. La scarsa conducibilità protonica dei polimeri perfluorurati per temperature maggiori di 90°C e bassi livelli di idratazione limita fortemente il loro utilizzo su larga scala. Celle a combustibile che operano a temperature superiori a 120°C e bassi livelli di idratazione non necessitano dell’introduzione di sistemi di umidificazione e raffreddamento, riducendo il costo e semplificando la realizzazione ed ingegnerizzazione del dispositivo finale. Inoltre, l’aumento di temperatura riduce l’avvelenamento del catalizzatore da contaminanti esterni come ad esempio il monossido di carbonio. Al fine di superare le limitazioni delle PEMs convenzionali, questo lavoro di tesi riporta la sintesi e la caratterizzazione di nuove membrane polimeriche a conducibilità protonica alternative ai classici polimeri fluorurati per applicazioni in celle a combustibile. I materiali sono stati sintetizzati seguendo due diverse strategie: 1) drogare una membrane di Nafion al fine di aumentare il suo intervallo di stabilità termico e meccanico e la sua conducibilità protonica così da estenderne le condizioni operative di utilizzo a temperature maggiori di 90°C e per bassi o nulli livelli di idratazione; 2) sintetizzare e caratterizzare PEMs basate su polibenzimidazolo e polisulfone come materiali alternativi ai classici polimeri fluorurati. Il primo punto ha riguardato lo studio di due diversi sistemi ottenuti drogando una membrana di Nafion con il filler inorganico [(ZrO2)(Ta2O5)0.119] oppure con due diversi liquidi ionici a conducibilità protonica, il trietilammonio-metansolfonato ed il trietilammonio-perfluorobutansolfonato. Lo studio di nuove membrane alternative ai polimeri fluorurati è stato sviluppato considerando membrane di polibenzimidazolo (PBI) e polisulfone solfonato (sPSO2) le cui proprietà sono state modulate dall’aggiunta di acido fosforico e di un filler ibrido a base di silice funzionalizzata (nel caso del PBI) o di poliossotrimetilene e silice (per le membrane a base di sPSO2). Al fine di delucidare le interazioni esistenti tra i diversi componenti presenti all’interno delle membrane, tutti i materiali sono stati ampiamente caratterizzati dal punto di vista delle loro proprietà termiche, meccaniche, strutturali ed elettriche. Queste interazioni governano le proprietà macroscopiche delle membrane che necessitano di essere migliorate al fine di ottimizzare e prevedere il comportamento di questi materiali in condizioni di esercizio in celle a combustibile.
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Mezzi, Rania. "Contrôle tolérant au vieillissement dans des systèmes pile à combustible PEMFC." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCD031.
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Les travaux présentés dans cette thèse portent sur la réalisation d’un contrôle tolérant au vieillissement pour un système pile à combustible à membrane échangeuse de protons (PEMFC). Afin d’atteindre cet objectif, des outils de supervision, comprenant le suivi de variables critiques, l’évaluation de l’état de santé présent et la prédiction de l’état futur sont étudiés et réalisés. L’information collectée est utilisée pour adapter la stratégie de contrôle du système. La priorité du système de supervision développé est d’assurer l’approvisionnement énergétique requis par l’utilisateur, tout en assurant une dégradation minimale de la pile à combustible. Le travail effectué consiste à déterminer les valeurs optimales de la température, des coefficients de stœchiométries de la cathode et de l’anode et du courant de pile pour fournir la puissance requise par la charge, tout en prolongeant la durée de vie de la PEMFC. La stratégie proposée permet d'éviter les dégradations réversibles et de ralentir le taux de vieillissement des composants, tout en maintenant la valeur de la tension dans une plage de fonctionnement optimale et peu dégradante. Cette plage de variation de la tension a été déterminée grâce à l’étude des mécanismes de dégradation de la PEMFCThe objective of this work is to realize an aging-tolerant control for a proton exchange membrane fuel cell system (PEMFC). In order to achieve this goal, supervision tools, including the monitoring of critical variables, the state of health evaluation and the prediction of the future state are studied and realized. The information collected are used to adapt the system control strategy. The priority of the monitoring system developed is to ensure the energy supply required by the user, while ensuring minimal degradation of the fuel cell. The work consists on determining optimal temperature values, cathode and anode stoichiometry coefficients, and fuel cell current to provide the power required by the load, while extending the lifetime of the PEMFC. The proposed strategy avoids reversible damage and slows the aging rate of the components, while maintaining the value of the voltage in an optimal and low degrading operating range. This voltage variation range was determined by studying the degradation mechanisms of PEMFC
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Andrea, Vinicius. "Estudo comparativo de desempenho e durabilidade de células a combustível do tipo PEM." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-29012018-103733/.
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O objetivo desse trabalho foi investigar as relações entre a durabilidade e as diversas configurações dos componentes de uma célula a combustível do tipo PEM por meio de Testes de Durabilidade de Longa Duração. Foram comparados três tipos de geometria de fluxo, duas espessuras de membranas poliméricas e dois níveis de cargas de platina. Em diversos aspectos, a geometria de canais de fluxo do tipo serpentina se mostrou superior aos demais. Em relação às membranas, as do tipo Nafion 212 se mostraram bastante frágeis e suscetíveis ao crossover de H2, apesar de fornecerem maior potência elétrica que as membranas Nafion 115, as quais exibiram maior durabilidade. No que diz respeito à carga de platina nos eletrodos, verificou-se que os eletrodos preparados com 0,1 mg Pt cm-2 perderam, proporcionalmente, mais área eletroquimicamente ativa que aqueles preparados com 0,4 mg Pt cm-2, mas, ao mesmo tempo, apresentaram as menores taxas de perdas irreversíveis de desempenho. As análises por diversas técnicas eletroquímicas indicaram que os aumentos das resistências ôhmicas e de transporte de massas são os fatores que mais contribuem para as perdas irreversíveis de desempenho, enquanto que o aumento da resistência de transporte de cargas devido ao encharcamento dos eletrodos é o principal responsável pelas perdas reversíveis de desempenho. A proporção de ionômero na camada catalítica foi investigada e verificou-se que, apesar de facilitar para que ocorram perdas reversíveis de desempenho, a maior proporção de ionômero na camada catalítica contribuiu em mitigar a degradação do MEA. Por fim, observou-se que a qualidade do contato entre os eletrodos e a membrana tem grande contribuição na durabilidade das células a combustível do tipo PEM.The aim of this work was to investigate the relations between durability and the several Proton Exchange Membrane Fuel Cell (PEMFC) setups via long-term durability tests. Comparisons were made with three types of flow field designs, two polymeric membranes thicknesses and two platinum loadings. In many aspects, the serpentine flow field design has presented better results than the others. Regarding the membranes, Nafion 212 has shown to be very fragile and susceptible to H2 crossover, although it provides more electrical power than the Nafion 115 membrane which exhibited better durability. Concerning the platinum loading, the electrodes prepared with 0.1 mg Pt cm-2 have lost proportionally more electrochemical surface area than the ones prepared with 0.4 mg Pt cm-2 but at the same time, the electrodes with the lowest platinum load presented lower irreversible performance loss rate. The analyses made by several electrochemical techniques have indicated that the raise of the ohmic and mass transport resistances are the factors that most contribute to the irreversible performance loss, meanwhile the charge transport resistance due to the electrodes flooding is the main responsible for the reversible performance loss. The proportion of ionomer in the catalytic layer was studied and it was possible to infer that the highest ionomer proportion contributes to mitigate the MEA degradation, although it facilitates the reversible performance loss occurrence. Finally, it was observed that the contact quality of the electrodes and the membrane has remarkable influence on the PEMFCs durability.
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Dur, Ender. "INVESTIGATIONS ON THE CORROSION RESISTANCE OF METALLIC BIPOLAR PLATES (BPP) IN PROTON EXCHANGE MEMBRANE FUEL CELLS (PEMFC) - UNDERSTANDING OF THE EFFECTS OF MATERIAL, COATING AND MANUFACTURING." VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/2628.
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Polymer Electrolyte Membrane Fuel Cell (PEMFC) systems are promising technology for contributing to meet the deficiency of world`s clean and sustainable energy requirements in the near future. Metallic bipolar plate (BPP) as one of the most significant components of PEMFC device accounts for the largest part of the fuel cell`s stack. Corrosion for metallic bipolar plates is a critical issue, which influences the performance and durability of PEMFC. Corrosion causes adverse impacts on the PEMFC`s performance jeopardizing commercialization. This research is aimed at determining the corrosion resistance of metallic BPPs, particularly stainless steels, used in PEMFC from different aspects. Material selection, coating selection, manufacturing process development and cost considerations need to be addressed in terms of the corrosion behavior to justify the use of stainless steels as a BPP material in PEMFC and to make them commercially feasible in industrial applications. In this study, Ti, Ni, SS304, SS316L, and SS 430 blanks, and BPPs comprised of SS304 and SS316L were examined in terms of the corrosion behavior. SS316L plates were coated to investigate the effect of coatings on the corrosion resistance performance. Stamping and hydroforming as manufacturing processes, and three different coatings (TiN, CrN, ZrN) applied via the Physical Vapor Deposition (PVD) method in three different thicknesses were selected to observe the effects of manufacturing processes, coating types and coating thicknesses on the corrosion resistance of BPP, respectively. Uncoated-coated blank and formed BPP were subjected to two different corrosion tests: potentiostatic and potentiodynamic. Some of the substantial results: 1- Manufacturing processes have an adverse impact on the corrosion resistance. 2- Hydroformed plates have slightly higher corrosion resistance than stamped samples. 3- BPPs with higher channel size showed better corrosion resistance. 4- Since none of the uncoated samples meet the 2015 target of the U.S. Department of Energy, surface coating is required. 5- ZrN and CrN coated BPPs exhibited higher corrosion resistance meeting DOE target while TiN coated samples had the lowest corrosion resistance. Higher coating thicknesses improved the corrosion resistance of the BPPs. 6- Process sequence between coating and manufacturing is not significant for hydroforming case (ZrN and CrN) and stamping case (CrN) in terms of the corrosion resistance. In other words, coating the BPP`s substrate material before manufacturing process does not always decrease the corrosion resistance of the BPPs.
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von, Kraemer Sophie. "Membrane Electrode Assemblies Based on Hydrocarbon Ionomers and New Catalyst Supports for PEM Fuel Cells." Doctoral thesis, KTH, Tillämpad elektrokemi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9208.
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The proton exchange membrane fuel cell (PEMFC) is a potential electrochemicalpower device for vehicles, auxiliary power units and small-scale power plants. In themembrane electrode assembly (MEA), which is the core of the PEMFC single cell,oxygen in air and hydrogen electrochemically react on separate sides of a membraneand electrical energy is generated. The main challenges of the technology are associatedwith cost and lifetime. To meet these demands, firstly, the component expensesought to be reduced. Secondly, enabling system operation at elevated temperatures,i.e. up to 120 °C, would decrease the complexity of the system and subsequentlyresult in decreased system cost. These aspects and the demand for sufficientlifetime are the strong motives for development of new materials in the field.In this thesis, MEAs based on alternative materials are investigatedwith focus on hydrocarbon proton-conducting polymers, i.e. ionomers, and newcatalyst supports. The materials are evaluated by electrochemical methods, such ascyclic voltammetry, polarisation and impedance measurements; morphological studiesare also undertaken. The choice of ionomers, used in the porous electrodes andmembrane, is crucial in the development of high-performing stable MEAs for dynamicoperating conditions. The MEAs are optimised in terms of electrode compositionand preparation, as these parameters influence the electrode structure andthus the MEA performance. The successfully developed MEAs, based on the hydrocarbonionomer sulfonated polysulfone (sPSU), show promising fuel cell performancein a wide temperature range. Yet, these membranes induce mass-transportlimitations in the electrodes, resulting in deteriorated MEA performance. Further,the structure of the hydrated membranes is examined by nuclear magnetic resonancecryoporometry, revealing a relation between water domain size distributionand mechanical stability of the sPSU membranes. The sPSU electrodes possessproperties similar to those of the Nafion electrode, resulting in high fuel cell performancewhen combined with a high-performing membrane. Also, new catalystsupports are investigated; composite electrodes, in which deposition of platinum(Pt) onto titanium dioxide reduces the direct contact between Pt and carbon, showpromising performance and ex-situ stability. Use of graphitised carbon as catalystsupport improves the electrode stability as revealed by a fuel cell degradation study.The thesis reveals the importance of a precise MEA developmentstrategy, involving a broad methodology for investigating new materials both as integratedMEAs and as separate components. As the MEA components and processesinteract, a holistic approach is required to enable successful design of newMEAs and ultimately development of high-performing low-cost PEMFC systems.QC 20100922
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Jalal, Ahmed Hasnain. "Multivariate Analysis for the Quantification of Transdermal Volatile Organic Compounds in Humans by Proton Exchange Membrane Fuel Cell System." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3886.
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In this research, a proton exchange membrane fuel cell (PEMFC) sensor was investigated for specific detection of volatile organic compounds (VOCs) for point-of-care (POC) diagnosis of the physiological conditions of humans. A PEMFC is an electrochemical transducer that converts chemical energy into electrical energy. A Redox reaction takes place at its electrodes whereas the volatile biomolecules (e.g. ethanol) are oxidized at the anode and ambient oxygen is reduced at the cathode. The compounds which were the focus of this investigation were ethanol (C2H5OH) and isoflurane (C3H2ClF5O), but theoretically, the sensor is not limited to only those VOCs given proper calibration.
Detection in biosensing, which needs to be carried out in a controlled system, becomes complex in a multivariate environment. Major limitations of all types of biosensors would include poor selectivity, drifting, overlapping, and degradation of signals. Specific detection of VOCs in multi-dimensional environments is also a challenge in fuel cell sensing. Humidity, temperature, and the presence of other analytes interfere with the functionality of the fuel cell and provide false readings. Hence, accurate and precise quantification of VOC(s) and calibration are the major challenges when using PEMFC biosensor.
To resolve this problem, a statistical model was derived for the calibration of PEMFC employing multivariate analysis, such as the “Principal Component Regression (PCR)” method for the sensing of VOC(s). PCR can correlate larger data sets and provides an accurate fitting between a known and an unknown data set. PCR improves calibration for multivariate conditions as compared to the overlapping signals obtained when using linear (univariate) regression models.
Results show that this biosensor investigated has a 75% accuracy improvement over the commercial alcohol breathalyzer used in this study when detecting ethanol. When detecting isoflurane, this sensor has an average deviation in the steady-state response of ~14.29% from the gold-standard infrared spectroscopy system used in hospital operating theaters.
The significance of this research lies in its versatility in dealing with the existing challenge of the accuracy and precision of the calibration of the PEMFC sensor. Also, this research may improve the diagnosis of several diseases through the detection of concerned biomarkers.
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Campagne, Benjamin. "Nouveaux copolymères fluorés porteurs de fonctions azole (imidazole, benzimidazole ou triazole) pour membranes pour piles à combustible (PEMFC) fonctionnant en conditions quasi-anhydres." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2013. http://www.theses.fr/2013ENCM0006.
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Ce travail de thèse s'inscrit dans la continuité des travaux de recherche sur l'utilisation d'hétérocycles azotés pour l'élaboration de membranes échangeuses de protons pour piles à combustible de type PEMFC fonctionnant sous faible taux d'humidité relative (HR < 25 %) et à des températures allant jusqu'à 200 °C pour l'application automobile. Pour cela, trois nouveaux copolymères partiellement fluorés porteurs de trois groupements azole (imidazole, benzimidazole et 1H-1,2,4-triazole) ont été synthétisés et caractérisés. Ils ont ensuite été utilisés pour l'élaboration de membranes polymères (20 µm < épaisseurs < 100 µm) par mélange avec le s-PEEK. Ces membranes sont stables thermiquement jusqu'à 210 °C. Les trois séries de membranes ont été comparées et les meilleurs résultats de conductivité protonique ont été obtenus pour celles contenant le 1H-1,2,4-triazole (σ = 7,0 mS.cm-1, 140 °C, HR < 25 %). Les propriétés mécaniques de ces membranes ont été mesurées et ont montré des valeurs comparables à celles des principales membranes commerciales (de type Nafion®). Afin d'obtenir une meilleure structuration de ces membranes, une stratégie d'élaboration de pseudo réseaux semi-interpénétrés de s-PEEK dans un réseau polymère réticulé a été mise au point. Pour cela, de nouveaux terpolymères porteurs de groupements 1H-1,2,4-triazole et de groupements cyclocarbonate réticulables par la réaction cyclocarbonate / amine ont été synthétisés et caractérisés. Ces terpolymères ont été mélangés à du s-PEEK puis réticulés par une diamine pour former des pseudo réseaux semi-interpénétrés de faibles épaisseurs (20 µm < e < 60 µm) qui ont été caractérisés. Ces membranes à architecture pseudo réseaux semi-interpénétrés ont montré de meilleures propriétés mécaniques mais des valeurs de conductivité protonique légèrement inférieures à celles des membranes non réticulées. Enfin, les membranes réticulées ou non ont été dopées par l'acide phosphorique pour augmenter leurs valeurs de conductivité protonique. Des essais en mono-cellule de PAC de ces membranes dopées ont été effectués et ont montré de bonnes performances. Des estimations par extrapolations des résultats ont ensuite été effectuées à plus hautes températures (140 – 200 °C) et ont montré que les valeurs de conductivité protonique atteignent jusqu'à 210 et 250 mS.cm-1, à 180 et 200 °C, HR < 25 % (valeurs extrapolées). Ces valeurs extrapolées doivent être vérifiées par la réalisation de mesures de conductivité protonique à ces températures (140 – 200 °C)This work concerns the syntheses and characterizations of new proton exchange polymer membranes containing N-heterocyclic compounds for PEMFC working under low relative humidity (HR < 25 %) and temperatures up to 200 °C for automotive applications. Three new partially fluorinated copolymers bearing different azole compounds (imidazole, benzimidazole or 1H-1,2,4-triazole) as pendant groups have been synthesized and characterized. Then, they have been used to synthesize blend polymer membranes with s-PEEK (20 µm < thickness < 100 µm) that showed thermal stabilities up to 210 °C. These new families of membranes have been compared and highest proton conductivity values have been observed for 1H-1,2,4-triazole containing membranes (σ = 7,0 mS.cm-1, 140 °C, HR < 25 %). Mechanical properties and oxidative stability of these membranes have been assessed and showed similar values than main commercially available membranes. To improve membranes structuration, pseudo semi-interpenetrating polymer networks have been synthesized. Thus, original cross-linkable terpolymers bearing 1H-1,2,4-triazole and cyclocabonate functions as pendant groups have been synthesized and blended with s-PEEK as linear polymer to synthesize new polymers membranes (20 µm < thickness < 60 µm). Cross-linking has been carried from the cyclocarbonate/diamine reaction to get pseudo semi-interpenetrated polymer networks. Finally, both pseudo semi-interpenetrated polymer networks and uncross-linked membranes were doped by immersion in phosphoric acid solution to increase proton conductivity of these materials. Single cell fuel cell tests have been carried out and showed good performances. High temperatures (140 – 180 °C) proton conductivity values of these doped membranes have been estimated from extrapolation curves and reached up to 210 and 250 mS.cm-1, at 180 and 200 °C, HR < 25 %, respectively (extrapolated values). Proton conductivity values should be assessed at these targeted temperatures (140 to 200 °C)
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BONIFACIO, RAFAEL N. "Estudo e desenvolvimento de conjuntos membrana-eletrodos (MEA) para célula a combustível de eletrólito polimérico condutor de prótons (PEMFC) com eletrocatalisadores à base de paládio." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10597.
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Made available in DSpace on 2014-10-09T12:42:20Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:59:42Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Tichagwa, Anesu. "Micro combined heat and power management for a residential system." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/16914.
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Fuel cell technology has reached commercialisation of fuel cells in application areas such as residential power systems, automobile engines and driving of industrial manufacturing processes. This thesis gives an overview of the current state of fuel cell-based technology research and development, introduces a μCHP system sizing strategy and proposes methods of improving on the implementation of residential fuel cell-based μCHP technology. The three methods of controlling residential μCHP systems discussed in this thesis project are heat-led, electricity-led and cost-minimizing control. Simulations of a typical HT PEMFC -based residential μCHP unit are conducted using these control strategies. A model of a residential μCHP system is formulated upon which these simulated tests are conducted. From these simulations, equations to model the costs of running a fuel-cell based μCHP system are proposed. Having developed equations to quantify the running costs of the proposed μCHP system a method for determining the ideal size of a μCHP system is developed. A sizing technique based on industrial CHP sizing practices is developed in which the running costs and capital costs of the residential μCHP system are utilised to determine the optimal size of the system. Residential thermal and electrical load profile data of a typical Danish household are used. Having simulated the system a practical implementation of the power electronics interface between the fuel cell and household grid is done. Two topologies are proposed for the power electronics interface a three-stage topology and a two-stage topology. The efficiencies of the overall systems of both topologies are determined. The system is connected to the grid so the output of each system is phase-shifted and DC injection, harmonic distortion, voltage range and frequency range are determined for both systems to determine compliance with grid standards. Deviations between simulated results and experimental results are recorded and discussed and relevant conclusions are drawn from these.
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Seminerio, Davide. "Modellazione e controllo di un sistema a celle a combustibile di tipo PEM." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
Find full textAbstract:
Le celle a combustibile sono dispositivi elettrochimici che convertono l’energia chimica di un combustibile gassoso in elettricità. Questa tecnologia sta assumendo un ruolo sempre più importante nello sviluppo futuro dello scenario energetico, essendo una soluzione alternativa e rinnovabile di produzione di energia elettrica. Un sistema fuel cell è composto da diversi sottosistemi che interagiscono tra di loro e la risposta del FCS (Fuel Cell System) dipende dall’alimentazione di aria e idrogeno, dalla regolazione dei flussi e delle pressioni, dalla gestione del calore e dell’acqua. In questo elaborato viene presentato un modello dinamico adatto alla comprensione del comportamento del sistema e allo studio del sistema di controllo. Il modello è stato sviluppato in ambiente Simulink, dove vengono inclusi i fenomeni transitori della dinamica dei flussi dei reagenti, l’inerzia del compressore, la dinamica di riempimento del collettore e l’umidità della membrana. La tecnica di controllo utilizzata, si basa su un classico controllo in retroazione (feedback) e in avanti(feed-forward) che utilizza un controllo proporzionale e integrativo (PI). La strategia di controllo viene applicata al flusso di ossigeno in ingresso al catodo e alla portata dell’idrogeno in ingresso all’anodo
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Östling, Erik. "Model on degradation of PEM fuel cells in marine applications." Thesis, KTH, Kemiteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299446.
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Sjöfarten står för 3 % av världens totala växthusgaser och är idag högst beroende av fossila bränslen. Ett alternativ för att gå över till en fossilfri flotta är användning av bränsleceller och vätgas som drivmedel. Om vätgasen produceras från elektrolys med förnyelsebara energikällor så är driften utsläppsfri och koldioxidneutral. Bränsleceller kan användas i många olika sammanhang, men har ännu inte slagit igenom med full kraft. En anledning till detta är livslängden som är för kort. För att sjöfarten ska kunna implementera bränslecellsdrift behöver nedbrytningen av bränslecellen bli vidare utforskad och motverkad. Syftet med detta examensarbete var att hitta de mest signifikanta nedbrytningsmekanismerna för sjöfarten samt att bygga en modell för att förutspå livslängden utifrån lastprofiler från fartyg. Rapportens avgränsningar var att enbart studera PEM-bränsleceller tack vare dess höga energitäthet och att teknologin är närmast marknaden för mobila applikationer. En litteraturstudie genomfördes för att fastställa de viktigaste nedbrytningsmekanismerna samt de faktorer som begränsar livslängden. Dessa bestämdes till start/stop cykler samt lastcykler vilka försämrar konduktiviteten i membranet samt minskar den elektrokemiska ytarean. En empirisk modell från experiment från litteraturen etablerades för att hitta relationen mellan parametrarna konduktivitet och elektrokemisk ytarea som funktion av start/stop cykler respektive lastcykler. En Comsol-modell användes för att utvärdera bränslecellens prestanda med dessa försämrade parametrar. Två lastprofiler analyserades och tolkades som antal start/stop cykler samt lastcykler för att utvärdera prestandan som funktion av antal år i drift. Båda fallen var i drift till dess att prestandan minskat med 20 % utvärderat vid strömtätheten 0.6 A/cm2. Båda lastprofilerna var utvärdera med olika körstrategier för att jämföra den modellerade livslängden beroende på ingångsvärden. Den första lastprofilen delades in i Case 1a och Case 1b där antalet start/stop cykler och lastcykler varierade. Resultatet visade att antalet timmar i drift mer än tredubblades i Case 1b där båda ingående indata hade minskats. Case 2 delades upp i tre olika körstrategier där Case 2a var en referens som jämfördes mot Case 2b respektive Case 2c. Skillnaden mot Case 2b var att antalet start/stop cykler per dag multiplicerades med faktor 4. Resultatet från modellen var att livstiden minskade från 6 till 4 år. Vidare utvärderades Case 2c där istället antalet lastcykler dividerades med faktor 4, allt annat identiskt med Case 2a. Utfallet var en ökad livslängd från 6 år till 11 år, med totalt 32 032 timmar i drift. Denna livslängd kan jämföras med kommersialiserade marina produkter från Ballard och Powercell, där livslängden är 30 000 respektive 20 000 timmar i drift. Sammanfattningsvis kan det konstateras att både start/stop cykler och lastcykler bryter ner bränslecellen och därmed minskar dess prestanda. Lastcykler var den faktor som var mest förödande gällande livslängden. Den modellerade livslängden på 32 032 timmar indikerar att den empirisk modellen tillsammans med Comsol-modellen genererade realistiska resultat. Slutligen kan sägas att ett område för framtida forskning inom ämnet innefattar lastcykler eftersom denna hade störst påverkan på modellen. Att särskilja olika typer av lastcykler och koppla till olika degradering skulle skapa än mer förståelse för livslängden. Då denna studie genomfördes på bränslecellsnivå skulle framtida studier kunna inkludera att analysera degradering på systemnivå för att få mer insikt i dessa processer.The shipping industry emits 3 % of the global GHG-emissions and is highly dependent on fossil fuels. One alternative to decarbonise the sector is by utilising hydrogen in fuel cells. The propulsion is free from emissions if hydrogen is produced from renewables. The fuel cell technology can be applied in various applications but have not been fully commercialised. One of the biggest bottlenecks for fuel cell technology is the durability that needs to be improved. In order for marine vessels to implement hydrogen propulsion, the degradation need to be further understood and mitigated. The purpose of this thesis was to assess the most significant degradation mechanisms for marine applications and to build a model to evaluate the lifetime depending on load profiles. The scope of the thesis was to include PEMFCs since they have the highest power density and are closest to commercialisation for transport applications. A literature review was conducted to assess the most important degradation mechanisms and operating conditions that limits the lifetime, which concluded in start/stop cycling and load cycling. These conditions deteriorate the membrane conductivity and the electrochemical surface area. An empirical model based on experimental data from the literature was conducted to find relationships for conductivity and ECSA as function of start/stop cycling and load cycling, respectively. A Comsol model was established to evaluate performance reduction with degraded parameters. Two different load cycles were interpreted as number of start/stop cycles and load cycles in order to simulate the degradation. The output was polarization curves as function of operating years. Each case was operated until a performance reduction of 20 % was obtained at the current density of 0.6 A/cm2. Both load profiles were analysed with different operation strategies to compare the resulting lifetime. The first load curve was divided into Case 1a and Case 1b where start/stop cycles and load cycles were altered. The results showed that the lifetime in operation hours was more than three-folded in Case 1b when the number of start/stop cycles and load cycles was reduced. Case 2 was divided into three operating strategies. For comparison with Case 2a, the number of start/stop cycles per day in Case 2b was increased by a factor of 4. The result was that the lifetime declined from 6 to 4 years. Furthermore, Case 2c evaluated the lifetime if the number of load cycles per day decreased by a factor of 4, all else being equal to Case 2a. The outcome was an increment in lifetime from 6 to 11 years, with a total of 32 032 hours of operation. This lifetime can be compared to commercialised products from Ballard and Powercell with lifetimes of 30 000 and 20 000 operating hours, respectively. Conclusively, the simulations showed that both start/stop cycling and load cycling deteriorates the fuel cell performance. Load cycling is the operating condition that cause the most severe degradation. Moreover, the modelled lifetime of 32 032 hours indicates that the empirical model in combination with the Comsol model generate realistic lifetimes. Finally, since load cycling had the most vital impact on the lifetime, one of the topics for future research would be to distinguish different types of load cycles and connect to separate degradation outcomes. Since the model was on fuel cell level, future work could also include systems effects such as ripple current or distributions within fuel cell stacks.
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Karo, Jaanus. "The Rôle of Side-Chains in Polymer Electrolytes for Batteries and Fuel Cells." Doctoral thesis, Uppsala universitet, Strukturkemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-100738.
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The subject of this thesis relates to the design of new polymer electrolytes for battery and fuel cell applications. Classical Molecular Dynamics (MD) modelling studies are reported of the nano-structure and the local structure and dynamics for two types of polymer electrolyte host: poly(ethylene oxide) (PEO) for lithium batteries and perfluorosulfonic acid (PFSA) for polymer-based fuel cells. Both polymers have been modified by side-chain substitution, and the effect of this on charge-carrier transport has been investigated. The PEO system contains a 89-343 EO-unit backbone with 3-15 EO-unit side-chains, separated by 5-50 EO backbone units, for LiPF6 salt concentrations corresponding to Li:EO ratios of 1:10 and 1:30; the PFSA systems correspond to commercial Nafion®, Hyflon® (Dow®) and Aciplex® fuel-cell membranes, where the major differences again lie in the side-chain lengths. The PEO mobility is clearly enhanced by the introduction of side-chains, but is decreased on insertion of Li salts; mobilities differ by a factor of 2-3. At the higher Li concentration, many short side-chains (3-5 EO-units) give the highest ion mobility, while the mobility was greatest for side-chain lengths of 7-9 EO units at the lower concentration. A picture emerges of optimal Li+-ion mobility correlating with an optimal number of Li+ ions in the vicinity of mobile polymer segments, yet not involved in significant cross-linkages within the polymer host. Mobility in the PFSA-systems is promoted by higher water content. The influence of different side-chain lengths on local structure was minor, with Hyflon® displaying a somewhat lower degree of phase separation than Nafion®. Furthermore, the velocities of the water molecules and hydronium ions increase steadily from the polymer backbone/water interface towards the centre of the proton-conducting water channels. Because of its shorter side-chain length, the number of hydronium ions in the water channels is ~50% higher in Hyflon® than in Nafion® beyond the sulphonate end-groups; their hydronium-ion velocities are also ~10% higher. MD simulation has thus been shown to be a valuable tool to achieve better understanding of how to promote charge-carrier transport in polymer electrolyte hosts. Side-chains are shown to play a fundamental rôle in promoting local dynamics and influencing the nano-structure of these materials.
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Linares, Lamus Rafael Antonio. "Alimentation d’une bobine supraconductrice par une pile à combustible à hydrogène et conception d'un aimant vectoriel de 3 T." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0249/document.
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La pile à combustible convertit l’énergie chimique des réactants en énergie électrique continue, en chaleur et en eau. Elle est généralement utilisée autour d’un point de fonctionnement (ou zone) correspondant à un maximum de puissance électrique. Le courant continu produit par la réaction d’oxydo-réduction est proportionnel à la surface active de la pile et la tension, qui est d’environ 0,6 V au point de nominal de fonctionnement, peut être augmentée par la mise en série de plusieurs cellules (constituant un stack). En raison de son faible niveau de tension continue, son utilisation dans des systèmes électriques nécessitent de l’associer à des convertisseurs de puissance. Les travaux effectués dans le cadre de cette thèse s’intéressent au potentiel d’une source électrique continue basse tension et plus exactement à l’utilisation de la pile à combustible en fonctionnement source de courant commandée (par le débit d’un des réactants). L’expertise du laboratoire GREEN dans le domaine des supraconducteurs, nous a conduits naturellement vers une application innovante à savoir substituer les alimentations de puissance dédiées aux dispositifs supraconducteurs par une pile à combustible. Un premier essai prometteur mené sur une bobine supraconductrice de 4 mH a mis en évidence tout le potentiel d’une telle application et nous a encouragés à étendre l’étude à des bobines supraconductrices fortement inductives, des plusieurs henrys. En effet, les énergies mises en jeu sont alors plus importantes et exigent de dimensionner avec soin le banc d’essai, aussi bien du point de vue de la protection de la pile que des conditions opératoires. Pour ce faire, une modélisation et une expérimentation d’un ensemble pile à combustible/bobine supraconductrice ont également été réalisées. En parallèle du travail mené sur la partie alimentation de la bobine supraconductrice, nous avons travaillé sur le dimensionnement d’un dispositif supraconducteur innovant, communément appelé aimant vectoriel, à trois axes. Ce système peut servir comme charge pour une pile à combustible mais aussi, et surtout, comme outils de caractérisation d’échantillons supraconducteurs. Cet aimant vectoriel permet d’orienter dans les 3 directions de l’espace un champ magnétique de plusieurs teslas, uniforme à plus de 95 % dans une sphère de 100 mm de diamètre. Ce dimensionnement, nous a permis de concevoir et réaliser la structure supportant le bobinage du fil et de choisir un certain fil supraconducteur. Le système complet devant coûter moins de 50 k€, cryostat inclus, nous nous sommes orientés vers du fil supraconducteur à basse température critique, refroidi à l’hélium liquideThe fuel cell (FC) converts the chemical energy of the reactants into direct electrical energy, heat and water. The FC is generally used around an operating point (or area) corresponding to a maximum of electric power. The direct current produced by the redox reaction is proportional to the active surface of the single cell and its voltage, which is approximately 0.6 V at the nominal operating point, can be increase by connecting several cells in series (constituting a stack). Due to its low DC voltage amplitude, its use in electrical systems requires the use of power converters. In this work, we have been interested taking benefit of such DC low voltage power source and more precisely the use of the FC as a current source controllable by the one of the reactant flow rates. The expertise of GREEN laboratory in the field of superconductors has naturally led us to an innovative application, namely to substitute the power supplies dedicated to the superconducting devices by a FC. A first promising test conducted on a 4 mH superconducting coil highlighted the full potential of such an application and encouraged us to extend the study to highly inductive superconducting coils where the energies involved are more important. This requires to carefully design the test bench with a protection system for the FC as well as operating conditions. To this end, a FC model supplying a superconducting coil has been developed and tested experimentally. At the same time, we have focused on the supply part of the superconducting coil by designing an innovative superconducting device, commonly called a three-axis vector magnet. This system can be used as a load for a fuel cell, but also, and above all, as a tool for the characterization of superconducting samples. This vector magnet allows to orient a magnetic field of several tesla in the three space directions, with a uniformity of more than 95 % in a 100 mm sphere of diameter. This design allowed us to realize the windings supporting structure and to choose a superconducting wire. The complete system has to cost less than 50 k€, including the cryostat, we have finally choose a superconducting wire with low critical temperature, cooled by liquid helium
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Kamara, Konakpo Parfait. "Stratégies d’utilisation du bio hydrogène pour la technologie PEMFC : utilisation directe." Electronic Thesis or Diss., Université Grenoble Alpes, 2024. http://www.theses.fr/2024GRALI037.
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La France dans le but de décarboner son mix énergétique et baisser ses émissions de CO2 a décidé d’investir massivement dans la production décarbonée d’hydrogène comme vecteur d’énergie pour des applications de mobilités ou stationnaires[1]. Sur le million de tonnes d’hydrogène produit en France, 96 % est produit par vaporeformage d’hydrocarbures. La stratégie Française vise à développer la filière hydrogène en investissant dans l’installation d’électrolyseurs. De plus les dernières découvertes d’énormes gisements d’hydrogène naturel (46 millions de tonnes d’hydrogène en Lorraine) crée l’enthousiasme et agrandi le champ des perspectives. [2]. Une autre filière de production d’hydrogène décarboné dont on parle le moins est la filière biologique qui présente un grand potentiel de diversifications des voies de productions. L’hydrogène issu de ces filières pose le problème de sa qualité pour une application dans la mobilité ou le stationnaire dans des systèmes de pile à combustible.L’objet de ces travaux de thèse est de définir des stratégies pour l’utilisation du bio hydrogène ou hydrogène naturel par la technologie de pile à combustible à membrane échangeuse de protons (PEMFC) et en passant par les étapes de production de l’hydrogène jusqu’à sa conversion électrochimique.La première partie a consisté à étudier l’impact des impuretés ou diluants (N2, Ar, He, CH4, CO2) contenus dans l’hydrogène issu des filières biologique et natif dans une demi-cellule (cellule de diffusion de gaz, GDE). Ensuite cette étude a été étendue à une mono cellule de pile à combustible à membrane échangeuse de protons. Enfin un réacteur biologique à échelle du laboratoire a permis de produire de l’hydrogène à partir de sources organiques par photo fermentation (PF) qui a ensuite été testé en GDE. Plusieurs techniques de caractérisations électrochimiques et physicochimiques comme la voltammétrie cyclique, la chrono amperommétrie, la mesure de surface électro-active par CO stripping, la microscopie électronique à balayage et à transmission, la chromatographie ionique etc…ont permis d’évaluer les performances de la PEMFC alimenté par du bio hydrogène ainsi que son impact sur les éléments d’une pile à combustible.Les résultats de l’activité des électrodes pour la réaction d’oxydation de l’hydrogène en GDE ont mis évidence des effets de limitations par le transport de matières pour l’ensemble mélange, avec des comportements particuliers observés pour le mélange à l’azote, et les mélanges au méthane et au dioxyde de carbone qui en plus de la dilution ont un effet d’empoisonnement au monoxyde de carbone de l’électrode.Ensuite, les tests en mono cellule alimenté par les mélanges H2/Ar, H2/N2 et H2/CO2 à 30 et 40 % volumique en H2 pour une application stationnaire ont révélé des pertes de performances plus importantes pour le mélange au dioxyde carbone, les mélanges à l’argon et à l’azote ont des performances quasiment équivalentes. Ces pertes de performances sont dues à des pertes de surfaces électro actives.Enfin la production de bio hydrogène par PF a montré que le choix de la biomasse, le prétraitement et la souche bactérienne influençaient la qualité du biogaz produit et les performances électrochimiques obtenues à partir de ce dernier sans étapes de purification.Références[1] « Présentation de la stratégie nationale pour le développement de l’hydrogène décarboné en France ». Consulté le: 11 janvier 2024. [En ligne]. Disponible sur: https://www.economie.gouv.fr/presentation-strategie-nationale-developpement-hydrogene-decarbone-france[2] « Le plus gros gisement d’hydrogène naturel du monde vient d’être découvert en France », SudOuest.fr. Consulté le: 11 janvier 2024. [En ligne]. Disponible sur: https://www.sudouest.fr/economie/energie/le-plus-gros-gisement-d-hydrogene-naturel-du-monde-vient-d-etre-decouvert-en-france-17826239.phpWith the aim of decarbonizing its energy mix and lowering its CO2 emissions, France has decided to invest massively in the decarbonized production of hydrogen as an energy carrier for mobility and stationary applications [1]. Of the one million ton of hydrogen produced in France, 96% is produced by steam reforming of hydrocarbons. France's strategy is to develop the hydrogen sector by investing in the installation of electrolyzers. What's more, the latest discoveries of huge deposits of natural hydrogen (46 million tons of hydrogen in Lorraine) are creating enthusiasm and expanding the field of prospects. [2]. Another decarbonated hydrogen production sector that is less talked about is the biological sector, which offers great potential for diversifying production routes. Hydrogen from these sources raises the question of its quality for use in mobility or stationary fuel cell systems.The aim of this thesis is to define strategies for the use of bio-hydrogen or natural hydrogen using proton exchange membrane fuel cell (PEMFC) technology, from hydrogen production to electrochemical conversion.The first part consisted in studying the impact of impurities or diluents (N2, Ar, He, CH4, CO2) contained in hydrogen from biological and native processes in a half-cell (gas diffusion electrode, GDE). This study was then extended to a single-cell proton exchange membrane fuel cell. Finally, a laboratory-scale biological reactor was used to produce hydrogen from organic sources by photo fermentation (PF), which was then tested in a GDE. Several electrochemical and physicochemical characterization techniques, such as cyclic voltammetry, chrono amperometry, CO stripping for electroactive surface measurement, scanning and transmission electron microscopy, ion chromatography, etc., were used to assess the performance of the PEMFC fed by bio-hydrogen, and its impact on fuel cell components.The results of the electrode activity for the hydrogen oxidation reaction in GDE revealed mass-transport limitation effects for the mixtures, with a particular behavior observed for the nitrogen mixture, and the methane and carbon dioxide mixtures, which in addition to dilution have a carbon monoxide poisoning effect on the electrode.Next, single-cell tests using H2/Ar, H2/N2 and H2/CO2 mixtures at 30 and 40% H2 by volume for stationary applications revealed greater performance losses for the carbon dioxide mixture, while the argon and nitrogen mixtures performed almost equally well. These performance losses are due to electroactive surface losses.Finally, the production of biohydrogen by PF showed that the choice of biomass, pre-treatment and bacterial strain influenced the quality of the biogas produced and the electrochemical performances obtained from it without purification steps.References[1] « Présentation de la stratégie nationale pour le développement de l’hydrogène décarboné en France ». Consulté le: 11 janvier 2024. [En ligne]. Disponible sur: https://www.economie.gouv.fr/presentation-strategie-nationale-developpement-hydrogene-decarbone-france[2] « Le plus gros gisement d’hydrogène naturel du monde vient d’être découvert en France », SudOuest.fr. Consulté le: 11 janvier 2024. [En ligne]. Disponible sur: https://www.sudouest.fr/economie/energie/le-plus-gros-gisement-d-hydrogene-naturel-du-monde-vient-d-etre-decouvert-en-france-17826239.php
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Santos, Antonio Rodolfo dos. "Análise por impedância eletroquímica \"on-line\" de conjuntos eletrodo/membrana (MEA) de células a combustível a membrana polimérica (PEMFC)." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-16052012-093213/.
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Este trabalho apresenta resultados de estudos e caracterizações de Conjuntos Eletrodo/Membrana (MEAs) de Células a Combustível a Membrana Polimérica (PEMFC). Algumas condições de operação de células e diferentes processos de produção de MEA foram investigados. A técnica de Espectroscopia de Impedância Eletroquímica (EIE) (em situ - 0 a 16 A) foi usada \"on-line\" como uma ferramenta de diagnóstico, relativa ao desempenho de célula. As medidas de EIE foram feitas através do Sistema de EIE para células a combustível FC350 (GAMRY), junto a um PC4 Potentiostato/Galvanostato e conectado à carga dinâmica (TDI) para experimentos de EIE \"on-line\" (100 mHz - 10 kHz, dU = 5 mV). MEAs com 25 cm2 de área ativa, usando eletrocatalisadores PtM/C 20 % (M = Ru, Sn ou Ni) fabricados usando o Método de Redução por Álcool (MRA). A tinta catalítica foi diretamente aplicada no Tecido de Carbono (GDL) e este prensado na membrana de Nafion® (105). MEAs usando eletrocatalisadores Pt/C e PtRu/C 20 % da E-TEK foram fabricados para comparação. Todos os cátodos foram confeccionados com Pt/C 20% da E-TEK. Foram fixadas as concentrações de metal nobre em 0,4 mg Pt.cm-2 no anodo e 0,6 mg Pt.cm-2 no catodo (E-TEK). Diagramas de Nyquist dos MEAs com Pt/C e PtRu/C da E-TEK ou PtM/C MRA apresentaram as mesmas resistências de ôhmicas para os MEAs. Este fato pode ser explicado por supressão de aglomerados durante o processo de preparação do MEA ou pela homogeneidade do eletrocatalisador ancorado ao carbono. Também pôde ser observado, a baixas densidades atuais que há uma diferença de desempenho significante entre o eletrocatalisadores da ETEK e os preparados pelo MRA. Os resultados das curvas de polarização confirmaram que PtM/C MRA apresentara um aumento de atividade para as células alimentadas com metanol e etanol. A técnica de EIE se mostrou eficiente para a avaliação do método de preparação dos MEAs e do desempenho da célula, os resultados de EIE mostraram uma coerência na escolha do modelo do circuito elétrico para os MEAs utilizando hidrogênio, metanol e etanol. Esta coerência indica que outras resistências não consideradas no modelo não são relevantes na resistência total dos MEAs.This work reports results of studies and characterization on Membrane Electrode Assemblies (MEAs) for Proton Exchange Membrane Fuel Cell (PEMFC). Some cell operation conditions and different processes of MEA production were investigated. The Electrochemical Impedance Spectroscopy Technique (EIS) (in situ - 0 to 16 A) was used \"on-line\" as a tool for diagnosis, concerning the cell performance. The EIS measurements were carried out with a FC350 Fuel Cell EIS System (GAMRY), coupled to a PC4 Potentiostat/Galvanostat and connected to the electronic load (TDI) for \"on-line\" EIS experiments (100 mHz - 10 kHz, dU = 5 mV). MEAs with 25 cm2 surface area, using PtM/C 20% (M = Ru, Sn or Ni) electrocatalysts were manufactured using the Alcohol Reduction Process (ARP). The catalytic ink was applied directly into the Carbon Cloth (GDL) and pressed in the NafionR membrane (105). MEAs using Pt/C and PtRu/C 20% from E-TEK electrocatalysts were manufactured by comparison. All the cathodes were sprayed with Pt/C 20% from E-TEK. The noble metal concentrations used were set to 0.4 mg Pt.cm-2 at the anode and 0.6 mg Pt.cm-2 at the cathode (E-TEK). Nyquist diagrams of the MEAs with Pt/C and PtRu/C from E-TEK or PtM/C (M = Ru, Sn or Ni) ARP showed essentially the same ohmic resistances for the MEAs. This fact can be explained by suppression of agglomerates during the MEA preparation process or by the homogeneity of the anchored electrocatalysts at the carbon surface. It could also be observed, at low current densities, that there was a significant performance difference between the electrocatalysts from E-TEK and those prepared with the Alcohol Reduction Process. The polarization curves results confirmed that the PtM/C (M = Ru, Sn or Ni) ARP showed an activity increase for the methanol and ethanol fed cells. The technique of EIE was shown efficient for the evaluation of the method preparation of MEAs and the acting of the cell, the results of EIE showed coherence in the choice of the model the electric circuit for MEAs using hydrogen, methanol and ethanol. This coherence indicates that other resistances no considered in the model are not relevant in the total resistance of MEAs.
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SANTORO, THAIS A. de B. "Preparacao e caracterizacao de eletrocatalisadores Pt-terras raras/C para celulas a combustivel do tipo PEMFC." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9411.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Weißbach, Thomas. "Blending of Proton Conducting Copolymers." Master's thesis, Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-61695.
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Highly proton conducting polymers for operation in hydrogen/oxygen proton exchange membrane fuel cells (PEMFCs) provide often a poor mechanical strength due to high water contents. To strengthen the conducting polymers, blends with different ratios of partially fluorinated sulfonic acid graft and diblock copolymers with perfluorinated polymers were prepared. To analyze the effect of the different quantities of the compounds, with regard to water sorption and proton conducting properties, membranes were prepared by dissolving the components and drop casting.
Partially sulfonated poly([vinylidene difluoride-co-chlorotrifluoroethylene]-g-styrene) (P(VDF-co-CTFE)-g-SPS) was blended with polyvinylidene difluoride (PVDF), decreasing the ion exchange capacity (IEC). The blended polymers absorbed less water. However, the by AC impedance spectroscopy determined proton conductivity stayed stable or increased slightly. The effective proton mobility remained constant. Partially sulfonated poly([vinylidene difluoride-co-hexafluoropropylene]-b-styrene) (P(VDF-co-HFP)-b-SPS) with two different PS-block lengths were blended with different amounts of poly(vinylidene difluoride-co-hexafluoropropylene) (P(VDF-co-HFP)). In that case, the polymers absorbed less water and the proton conductivity decreased stepwise by adding more than 20 wt% P(VDF-co-HFP). The results indicate that a blending of P(VDF-co-CTFE)-g-SPS with PVDF inhibits swelling without having an effect on the proton conductivity, though water sorption and IEC are reduced.
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SENNA, ROQUE M. de. "Desenvolvimento e demonstração de funcionamento de um sistema híbrido de geração de energia elétrica, com tecnologia nacional, composto por módulo de células a combustível tipo PEMFC e acumulador chumbo ácido." reponame:Repositório Institucional do IPEN, 2012. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10121.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Rouhet, Marlene. "Etude de l'influence des protons sur la réduction de l'oxygène dans des couches catalytiques ordonnées en vue d'une application en pile à combustible." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF031/document.
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Les couches catalytiques avec une structure ordonnée à base de nanoparticules de Pt supportées sur des nanofilaments de carbone verticalement alignés ont montré des performances intéressantes grâce à l’amélioration des propriétés du transport de matière et à une meilleure utilisation du Pt. Des études électrochimiques combinées à une modélisation mathématique ont mis en évidence l’influence du transport de protons sur les processus d’oxydo-réduction, la cinétique et le mécanisme de réduction de l’O2 (ORR), et sur H2O2 qui s’échappe des couches pendant l’ORR. Nous avons montré que (i) les protons sont impliqués dans l’étape limitante de la réaction, (ii) pour un pH ≥ 3, un plateau de courant limité par la diffusion des protons est observé et, (iii) pour un pH ≥ 3, le mécanisme de l’ORR implique non seulement les ions hydroniums mais aussi les molécules d’eau. L’intégration de ces couches catalytiques dans des PEMFCs haute température a ensuite été étudiée. Les performances obtenues sont légèrement plus basses que celles des couches conventionnelles. Un travail d’optimisation reste donc à accomplir pour améliorer les performancesOrdered catalytic layers based on vertically aligned carbon nanofilaments with Pt nanoparticles demonstrate high efficiency for oxygen transport and Pt utilization in the catalytic layer. Electrochemical studies combined with mathematical modeling confirm the influence of the proton transport on surface red-ox processes, the kinetics and the mechanism of the O2 reduction (ORR), and on the H2O2 escape. We show that (i) protons are involved in the rate-determining step of the O2 reduction, (ii) for pH ≥ 3, a plateau corresponding to the diffusion-limited current of protons is observed and, (iii) for pH ≥ 3, the mechanism of the ORR involves not only the hydronium ions but also water molecules. The integration of these catalytic layers in high temperature PEMFCs was then studied. The performance is slightly lower than that for conventional layers. An optimization work is required to improve the performance