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Author: Selmen Laabidi Publisher: GRIN Verlag ISBN: 3656963959 Category : Technology & Engineering Languages : en Pages : 69
Book Description
Bachelor Thesis from the year 2015 in the subject Engineering - Mechanical Engineering, grade: 1,7, Swiss Federal Institute of Technology Zurich (Institute of machine tools and manufacturing), language: English, abstract: With the rising cost of energy, the increasing environmental awareness and the global warming, alternative drive systems are becoming increasingly important. Here, the fuel cell technology makes as clean and reliable method of energy production a great contribution. Many automotive companies like Hyundai, Daimler and Toyota are working intensively on fuel cell vehicles. Toyota has succeeded in December 2014 to bring the first car powered by hydrogen, the Toyota Mirai, on the market and it expects in the 2020s already with tens of thousands of vehicles annually. Therefore, the sales numbers will be increasing, which will require a mass production of fuel cells. Fuel cell technology is based on the principle of electrolysis. In order to generate electricity, hydrogen and oxygen are supplied to the fuel cell, where they react to electricity, water and heat. Thus cars powered by fuel cells have many advantages over cars with conventional sources, because they are environmentally friendly and save the long load time characterizing electric cars. However, the current manufacturing way does not meet the requirements of mass production. To date, the components of the fuel cell are often assembled to a stack without sufficient testing, which significantly increases the potential for errors. After assembly, an end-of-line test is performed, wherein the fuel cell and its functions are checked up for up to 24 hours. To achieve higher production volume, the duration of the end-of-line tests must be reduced to a few minutes. This requires a total quality management and quality assurance during production in order to achieve a quick and error-free one. The aim of this work is to shorten the duration of the end-of-line test by the development of a montage accompanying control plan. The first part deals with the basics of the fuel cell technology. The most important historical events of the development of fuel cells are mentioned. In order to understand their functioning, the chemical and physical principles are explained and the functions of the individual components are described. In the second part, a Failure mode and effect analysis (FMEA) is performed. Based on a literature review, this analysis aims at determining the most important errors in the components of the fuel cell. Its results deduce the most necessary test characteristics to be checked during the manufacturing of the fuel cell. [...]
Author: Selmen Laabidi Publisher: GRIN Verlag ISBN: 3656963959 Category : Technology & Engineering Languages : en Pages : 69
Book Description
Bachelor Thesis from the year 2015 in the subject Engineering - Mechanical Engineering, grade: 1,7, Swiss Federal Institute of Technology Zurich (Institute of machine tools and manufacturing), language: English, abstract: With the rising cost of energy, the increasing environmental awareness and the global warming, alternative drive systems are becoming increasingly important. Here, the fuel cell technology makes as clean and reliable method of energy production a great contribution. Many automotive companies like Hyundai, Daimler and Toyota are working intensively on fuel cell vehicles. Toyota has succeeded in December 2014 to bring the first car powered by hydrogen, the Toyota Mirai, on the market and it expects in the 2020s already with tens of thousands of vehicles annually. Therefore, the sales numbers will be increasing, which will require a mass production of fuel cells. Fuel cell technology is based on the principle of electrolysis. In order to generate electricity, hydrogen and oxygen are supplied to the fuel cell, where they react to electricity, water and heat. Thus cars powered by fuel cells have many advantages over cars with conventional sources, because they are environmentally friendly and save the long load time characterizing electric cars. However, the current manufacturing way does not meet the requirements of mass production. To date, the components of the fuel cell are often assembled to a stack without sufficient testing, which significantly increases the potential for errors. After assembly, an end-of-line test is performed, wherein the fuel cell and its functions are checked up for up to 24 hours. To achieve higher production volume, the duration of the end-of-line tests must be reduced to a few minutes. This requires a total quality management and quality assurance during production in order to achieve a quick and error-free one. The aim of this work is to shorten the duration of the end-of-line test by the development of a montage accompanying control plan. The first part deals with the basics of the fuel cell technology. The most important historical events of the development of fuel cells are mentioned. In order to understand their functioning, the chemical and physical principles are explained and the functions of the individual components are described. In the second part, a Failure mode and effect analysis (FMEA) is performed. Based on a literature review, this analysis aims at determining the most important errors in the components of the fuel cell. Its results deduce the most necessary test characteristics to be checked during the manufacturing of the fuel cell. [...]
Author: Muneendra Prasad Arkhat Publisher: ISBN: Category : Fuel cells Languages : en Pages : 207
Book Description
Polymer electrolyte membrane fuel cells (PEMFC) have the potential to deliver high power density with a lower weight and volume compared to other fuel cells. However, some of the barriers to the successful commercialization of PEMFCs include problems associated with durability, stability and cost. Fuel cell defects that arise and propagate in the membrane electrode assembly (MEA) components during manufacturing and subsequent operation are the biggest factors limiting their durability and stability, leading to shortened lifetimes, reduced performance or cell failure. Defects in the production line must be minimized if PEMFCs are to become reliable electrochemical energy devices on a commercial scale. A conventional PEMFC electrode consists of layers (CL) of nanoscale Pt catalyst particles mixed with an ionomer on a high surface area carbon support deposited on the polymer electrolyte membrane (PEM) and sandwiched between gas diffusion media (GDM). The defects in these components originate from the raw materials used in the catalyst layers, process conditions during catalyst mixing, coating techniques, drying process, thickness variations in the casting substrate and the temperature and humidity of the processing environment. These defects can lead to reduced performance and can increase fuel cell degradation, specifically in the MEA components. Understanding the MEA component defects that affect fuel cell performance and lifetime is integral to the successful development of an on-line quality control strategy. Previous research studies have been conducted on defects in catalyst-coated membranes (CCMs) and gas diffusion layers (GDLs) with various dimensions that have been introduced artificially at specific locations, which does not satisfactorily mimic the situation with real manufacturing defects. Very few studies on real defects have been reported to date with limited work on localized effects on CL defects such as loss of catalyst, the morphology of defect growth or the effect of defect location within the CCM on the resulting cell performance. This has limited our fundamental and comprehensive understanding of the nature of defects in the beginning-of-life (BOL) state and the manner in which they may or may not propagate during PEMFC operation. The focus of this research is to analyze real catalyst layer defects and membrane pinholes on commercial CCMs that are developed during mass production. Specifically, the objectives of this study are to: (i) develop a non-destructive method to identify and quantify defects in CCM electrodes, (ii) implement a defect analysis framework to age CCMs using open-circuit voltage(OCV)- accelerated stress tests (AST), (iii) characterize the electrochemical performance of CCM/MEAs with varying extent of manufacturing defects (catalyst layer thickness, degree of catalyst non-uniformity) and compare this to a baseline, defect-free CCM/MEA using ASTs as well as in-situ and ex-situ methods and (iv) investigate defects on GDL-microporous layer (MPL) using infrared (IR) imaging and surface conductivity measurements. The first set of quality control experiments were performed on CCMs by using optical microscopy to characterize catalyst layer defects. Defects such as micro/macro cracks, catalyst clusters, missing catalyst layer defects (MCLDs), void/empty areas, CL delamination and pinholes in the CCM were characterized in terms of areal dimension (size, shape, and orientation) prior to electrochemical analysis. The OCV-AST protocol was developed to age defected CCMs in a custom-designed test cell and track defect propagation and behavior during aging. The geometric features of the defects were quantified and their growth measured at regular time intervals from beginning-of-life (BOL) to end-of-life (EOL) until the OCV had dropped by 20% from its initial value (as per the DOE-designed protocol). Overall, two types of degradation were observed: surface degradation caused by catalyst erosion and crack degradation caused by membrane mechanical deformation. Furthermore, the catalyst layer defects formed during the decal transfer process exhibited a higher growth rate at middle-of-life (MOL-1) before stabilizing by EOL. The results of the crack propagation analysis during AST showed that the defected area covered under cracks increased from 2.4% of the total CL area at BOL to 10.5% by EOL with a voltage degradation rate of 2.55mV/hr. This type of analysis should provide manufacturers with baseline information that will allow them to select and reject CCMs, increasing the lifetime of fuel cell stacks. Once the CCM defects were analyzed comprehensively, research was carried out on the MEA stack. MEAs containing defected CCMs (incomplete catalyst layer defects-MCLD), pinhole across sealant and artificial pinholes at inlet/middle/outlet were investigated using a cyclic open-circuit voltage (COCV)-AST. Different RH cycling periods from 80% RH to 20% RH with time delays from 5 mins to 30 mins were applied to the cathode to study the propagation of defects and their effect on overall cell performance. In-situ analysis included the measurement of polarization curves, linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) to measure electrode degradation. Non-destructive ex-situ analysis using IR thermography was conducted every 100 cycles to monitor the evolution of defects in the MEA. The growth of pinholes was studied on the basis on hydrogen crossover curves. Sealing defects were found to have a major impact on performance loss compared to catalyst layer defects. It was also observed that MCLDs degraded within a short period of time and developed pinholes although the extent of this degradation depended on defect thickness. The MCLD defects were unstable and observed to continually grow due to gradual loss of catalyst particles inside the defected areas that accelerated pinhole formation in CCMs. This effect was clearly reflected in the continuous decay of OCV during the fuel cell operation. Therefore, CCMs leaving the production line with missing and /or thin portions of CL are not recommended for MEA fabrication as they ultimately affect the long-term stability of PEMFC. The last set of quality control experiments was conducted on GDL-MPL defects in samples that were being aged by RH cycling in a custom-design test cell. Thermal image analysis using IR thermography was carried out by passing DC current through the GDL sheet mounted on a porous vacuum stage to identify hot and cold spots reflecting defective areas. The morphological features and surface conductivity of MPL cracks were characterized using optical microscopy and four-point probe conductivity measurements. Interestingly, the nature of defects/cracks propagation in the GDL-MPL was found to affect cell performance in the mass transfer region at high currents. Crack propagation in GDL-MPL increased mass transport losses due to water flooding on the cathode, which was clearly observed in the polarization curves. Finally, the overall effects of catalyst layer defects, membrane pinholes and GDL defects on cell performance were compared. MEA sealant defects (pinholes) had such a negative effect on cell performance that EOL was reached after only ~ 50 hours of COCV operation at 80% - 20% RH cycling. Thus, the detection of such a defect in a CCM should be sufficient cause to reject it for use in a commercial stack. We also observed that CCMs with defects that led to 70% reduced thickness of the CL failed faster than those with the same type of defects that had resulted in 30% reduced thickness of the CL, presumably due to less available catalyst for electrochemical reactions. Clearly, CL defects should be given high priority in quality control inspection strategies devised by CCM electrode manufacturers and PEMFC operators.
Author: M. C. Williams Publisher: The Electrochemical Society ISBN: 1566775493 Category : Technology & Engineering Languages : en Pages : 876
Book Description
This issue of the 2006 Fuel Cell Seminar, held in Honolulu, Hawaii in 2006, marks the 30th Anniversary of the seminar, and contains papers dealing with stationary fuel cell systems, technology development, demonstration, and commercialization of fuel cells. Major topic of discussions throughout the three oral sessions and poster sessions were stationary fuel cell systems, hydrogen systems, and their efficient use as backup systems. Their use as alternative energies and portable fuel cells were also discussed.
Author: Felix N. Büchi Publisher: Springer Science & Business Media ISBN: 038785536X Category : Science Languages : en Pages : 489
Book Description
This book covers a significant number of R&D projects, performed mostly after 2000, devoted to the understanding and prevention of performance degradation processes in polymer electrolyte fuel cells (PEFCs). The extent and severity of performance degradation processes in PEFCs were recognized rather gradually. Indeed, the recognition overlapped with a significant number of industrial dem- strations of fuel cell powered vehicles, which would suggest a degree of technology maturity beyond the resaolution of fundamental failure mechanisms. An intriguing question, therefore, is why has there been this apparent delay in addressing fun- mental performance stability requirements. The apparent answer is that testing of the power system under fully realistic operation conditions was one prerequisite for revealing the nature and extent of some key modes of PEFC stack failure. Such modes of failure were not exposed to a similar degree, or not at all, in earlier tests of PEFC stacks which were not performed under fully relevant conditions, parti- larly such tests which did not include multiple on–off and/or high power–low power cycles typical for transportation and mobile power applications of PEFCs. Long-term testing of PEFCs reported in the early 1990s by both Los Alamos National Laboratory and Ballard Power was performed under conditions of c- stant cell voltage, typically near the maximum power point of the PEFC.
Author: Detlef Stolten Publisher: John Wiley & Sons ISBN: 3527330127 Category : Science Languages : en Pages : 1298
Book Description
Fuel cells are expected to play a major role in the future power supply that will transform to renewable, decentralized and fluctuating primary energies. At the same time the share of electric power will continually increase at the expense of thermal and mechanical energy not just in transportation, but also in households. Hydrogen as a perfect fuel for fuel cells and an outstanding and efficient means of bulk storage for renewable energy will spearhead this development together with fuel cells. Moreover, small fuel cells hold great potential for portable devices such as gadgets and medical applications such as pacemakers. This handbook will explore specific fuel cells within and beyond the mainstream development and focuses on materials and production processes for both SOFC and lowtemperature fuel cells, analytics and diagnostics for fuel cells, modeling and simulation as well as balance of plant design and components. As fuel cells are getting increasingly sophisticated and industrially developed the issues of quality assurance and methodology of development are included in this handbook. The contributions to this book come from an international panel of experts from academia, industry, institutions and government. This handbook is oriented toward people looking for detailed information on specific fuel cell types, their materials, production processes, modeling and analytics. Overview information on the contrary on mainstream fuel cells and applications are provided in the book 'Hydrogen and Fuel Cells', published in 2010.
Author: Cornelia Breitkopf Publisher: Springer ISBN: 3662466570 Category : Technology & Engineering Languages : en Pages : 1019
Book Description
This comprehensive handbook covers all fundamentals of electrochemistry for contemporary applications. It provides a rich presentation of related topics of electrochemistry with a clear focus on energy technologies. It covers all aspects of electrochemistry starting with theoretical concepts and basic laws of thermodynamics, non-equilibrium thermodynamics and multiscale modeling. It further gathers the basic experimental methods such as potentiometry, reference electrodes, ion-sensitive electrodes, voltammetry and amperometry. The contents cover subjects related to mass transport, the electric double layer, ohmic losses and experimentation affecting electrochemical reactions. These aspects of electrochemistry are especially examined in view of specific energy technologies including batteries, polymer electrolyte and biological fuel cells, electrochemical capacitors, electrochemical hydrogen production and photoelectrochemistry. Organized in six parts, the overall complexity of electrochemistry is presented and makes this handbook an authoritative reference and definitive source for advanced students, professionals and scientists particularly interested in industrial and energy applications.
Author: Yun Wang Publisher: Momentum Press ISBN: 1606502476 Category : Technology & Engineering Languages : en Pages : 450
Book Description
Polymer Electrolyte Membrane (PEM) fuel cells convert chemical energy in hydrogen into electrical energy with water as the only by-product. Thus, PEM fuel cells hold great promise to reduce both pollutant emissions and dependency on fossil fuels, especially for transportation—passenger cars, utility vehicles, and buses—and small-scale stationary and portable power generators. But one of the greatest challenges to realizing the high efficiency and zero emissions potential of PEM fuel cells technology is heat and water management. This book provides an introduction to the essential concepts for effective thermal and water management in PEM fuel cells and an assessment on the current status of fundamental research in this field. The book offers you: • An overview of current energy and environmental challenges and their imperatives for the development of renewable energy resources, including discussion of the role of PEM fuel cells in addressing these issues; • Reviews of basic principles pertaining to PEM fuel cells, including thermodynamics, electrochemical reaction kinetics, flow, heat and mass transfer; and • Descriptions and discussions of water transport and management within a PEM fuel cell, including vapor- and liquid-phase water removal from the electrodes, the effects of two-phase flow, and solid water or ice dynamics and removal, particularly the specialized case of starting a PEM fuel cell at sub-freezing temperatures (cold start) and the various processes related to ice formation.
Author: Selmen Laabidi
Author: Selmen Laabidi
Author: Muneendra Prasad Arkhat
Author: D. J. Jones
Author: D. J. Jones
Author: M. C. Williams
Author: Felix N. Büchi
Author: Detlef Stolten
Author: Cornelia Breitkopf
Author: 
Author: Yun Wang