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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Hybrid PEM fuel cell systems

Gößling, Sönke, Smyrek, Felix, Bahr, Matthias 27 May 2022 (has links)
Nowadays, PEM fuel cell systems for passenger cars are always realized as hybrid systems. If the architecture of a hybrid system is given, then the dimensioning of the fuel cell and battery subsystems is crucial in terms of costs, dynamics, and driving behavior in general. In order to analyze these dependencies correctly, the ZBT fuel cell model was integrated into a fuel cell system and a full vehicle simulation. The subject of the investigation is the interaction of different drive cycles, which in part are very different, with differently dimensioned sub models for the fuel cell system and the battery. The ZBT fuel cell model is integrated into the simulation environment AVL CRUISE™ M for the fuel cell system and the vehicle. An analysis is presented that compares the different drive cycles and system dimensions and provides specific recommendations for different use cases.
122

Sensor based concept for PEM fuel cell development based on the IPEK-X-in-the-Loop approach

Haußmann, Jan, Bause, Katharina, Ott, Sascha 27 May 2022 (has links)
The development of PEM fuel cell systems can be further improved, if the interactions between the different development levels are considered. The IPEK X-in-the-loop approach allows connecting the operating conditions measured locally at the fuel cell components, like the bipolar plate with data from the drivetrain and the fuel cell system. Measurement data taken from micro sensors can be transmitted to control the fuel cell system components. The mixed virtual-physical approach allows emulating different types of components instantly and facilitates the optimization of fuel cell components and operating strategies. With this development method the fuel cell and the fuel cell system components as well as the operating controls can be improved with respect to power dynamics, power density and lifetime.
123

Gripper integrated vision system for on-the-fly position measurement of individual components in fuel cell stacking

Schäfer, Jens, Fleischer, Jürgen 27 May 2022 (has links)
The stacking of membrane electrode assemblies (MEA) and bipolar plates is a key process in fuel cell stack production, in which requirements for high accuracy and shortest possible process time must be taken into account. In this paper technical systems for fuel cell stack assembly are analysed regarding means for handling, gripping and alignment of the components. The different methods are compared and evaluated, followed by a novel system allowing for an on-the-fly measurement of the position / Das Stapeln von Membran-Elektroden-Einheiten (MEA) und Bipolarplatten ist ein Schlüsselprozess in der Brennstoffzellen-Stack-Produktion, bei dem die Anforderungen an eine hohe Genauigkeit und eine möglichst kurze Prozesszeit berücksichtigt werden müssen. In diesem Beitrag werden technische Systeme für die Montage von Brennstoffzellenstapeln hinsichtlich der Handhabung, des Greifens und der Ausrichtung der Komponenten analysiert. Die verschiedenen Methoden werden verglichen und bewertet, gefolgt von einem neuartigen System, das eine on-the-fly Messung der Position ermöglicht.
124

Design and characterization of a metallic bipolar plate based on phase change cooling with modified surfaces

Steinert, Philipp, Danilov, Igor, Zinecker, Mike, Moritz, René, Schmiedel, René, Enders, Florian, Krähmer, Tom, Reif, Andreas, Fischer, Hendrik, von Unwerth, Thomas, Schubert, Andreas 27 May 2022 (has links)
The increasing demand for more efficient cooling options in the areas of fuel cell technology motivates the development of novel cooling strategies with improved heat transfer. Cooling through phase transition of the coolant from the liquid to the gaseous state is therefore a suitable approach. In this context, the phase transition behaviour in the inner structure of bipolar plates, which is determined by the flow field and its surface properties, must be understood and designed as a central functional element for cooling in a fuel cell. For the integrated development of a metallic bipolar plate based on the phase change cooling with modified surfaces, this paper discusses the design of the flow field, the design of the associated forming technology as well as the coating technology that meets the requirements of the bipolar plates with phase change cooling principle. In this regard, the wetting and the corrosion behaviour of different surface coatings and the in-situ phase transition behaviour within the bipolar plates are demonstrated and discussed.
125

Production of platinum poor electrodes for PEMFC by electrochemical deposition

Werwein, Anton, Kunz, Karina, Reuber, Sebastian, Weiser, Mathias, Goldberg, Adrian, Partsch, Mareike, Michaelis, Alexander 27 May 2022 (has links)
A new R2R capable process to produce platinum-poor fuel cells was presented in the lab scale. Platinum particles were deposited electrochemically on a mesoporous carbon carrier with various carbon carriers (Super P Li, Denka Black Li 400, Denka Black Li 435, Ketjenblack EC300). FESEM images showed particles in the range of 50 nm one the electrode surface. The catalyst containing electrodes were transferred via hot press from different metallic and polymeric decal materials on a polymer exchange membrane. First functional membrane electrode assemblies show the proof-of-principles of this new process. / Ein neuer R2R-fähiger Prozess für die Herstellung platinumarmer Brennstoffzellen wurde im Labormaßstab etabliert. Platinumpartikel wurde elektrochemisch auf einen mesoporösen Kohlenstoffträger mit verschieden Leitrußen (Super P Li, Denka Black Li 400, Denka Black Li 435, Ketjenblack EC300) abgeschieden. FESEM-Aufnahmen zeigen Partikel in der Größenordnung von 50 nm auf der Elektrodenoberfläche. Die katalysatorhaltige Elektrode wird mittels eines Heißpressverfahren auf eine Polymeraustauschmembran übertragen. Erste funktionsfähige Membran-Elektroden-Assemblierungen zeigen die Funktionsfähigkeit des Prozesses.
126

Zielgrößen und Spannungsfelder beim Vergleich von Herstellungs-verfahren für metallische Bipolarplatten

Porstmann, Sebastian, Polster, Stefan, Reuther, Franz, Melzer, Sebastian, Nagel, Matthias, Psyk, Verena, Dix, Martin 27 May 2022 (has links)
Elektrochemische Energiewandler sind eine hervorragende Möglichkeit, die Energieversorgung der Zu-kunft zu sichern. Eine Schlüsselkomponente der hierfür benötigten Polymer-Elektrolyt-Membran-Brenn-stoffzellen und -Elektrolyseurzellen ist die Bipolarplatte. Für die Herstellung metallischer Bipolarplatten sind verschiedene umformende Fertigungstechnologien geeignet, die sich hinsichtlich erreichbarer Fer-tigungskosten, Endeigenschaften der Bipolarplatte und technologischer Prozessgrenzen unterschei-den. In diesem Artikel werden die aktuell präferierten Fertigungstechnologien wie die wirkmedienba-sierte Blechumformung, sowie das Hohlprägen und das Hohlprägewalzen zur Herstellung von metalli-schen Bipolarplatten miteinander verglichen und bewertet. / Electrochemical energy converters are an excellent option to secure the energy supply of the future. A key component of the polymer electrolyte membrane fuel cells and -electrolyser cells required for this purpose is the bipolar plate. Various forming technologies with different manufacturing costs, final prop-erties of the bipolar plates, and technological process limits are suitable for the fabrication of metallic bipolar plates. In this article, the currently preferred manufacturing technologies to produce metallic bipolar plates like precisely media-based sheet forming as well as hollow embossing and roll embossing, are compared and evaluated.
127

Development of a Bypass Valve to Improve Fuel Cell Safety and Durability

Crepet, Guy, Guesne, Samuel, Didier, Dominique, Laire, Louis, Pacot, Pierre 27 May 2022 (has links)
Properly inerting a fuel cell is an essential function for the safety and durability of the product. DAM designs and produces a bypass valve to effectively inert the fuel cell while maintaining the oxidant gas flow in the compressor. The system provides a short closing and opening response time less than 100 ms, while consuming very little energy. In addition to cutting off the oxidant gas supply, the valve can be used to drain the fuel cell, optimize the shutdown and startup cycles, and even optimize the inerting of the fuel cell through the hydrogen circuit. DAM has already produced valve prototypes in diameters 16 mm and 50 mm which are currently in the test phase with first successful results, and whose functions can be extended with a position sensor or heating system. / Die geeignete Inertisierung einer Brennstoffzelle ist eine wesentliche Funktion für die Sicherheit und Lebensdauer des Produkts. DAM entwickelt und produziert ein Bypass-Ventil, das die Brennstoffzelle effektiv inertisiert und gleichzeitig den Oxidationsmittel-Gasstrom im Kompressor aufrechterhält. Das System bietet eine kurze Schließ- und Öffnungszeit von weniger als 100 ms und verbraucht dabei sehr wenig Energie. Neben der Unterbrechung der Oxidationsgaszufuhr kann das Ventil auch zum Entleeren der Brennstoffzelle, zur Optimierung der Abschalt- und Anfahrzyklen und sogar zur Optimierung der Inertisierung der Brennstoffzelle durch den Wasserstoffkreislauf eingesetzt werden. DAM hat bereits Ventilprototypen in den Durchmessern 16 mm und 50 mm hergestellt, die sich derzeit mit ersten Erfolgen in der Testphase befinden und deren Funktionen durch einen Positionssensor oder ein Heizsystem erweitert werden können.
128

Development of a Universal Cell Voltage Monitoring System

Crepet, Guy, Guesne, Samuel, Lavarenne, Cyril, Valentin, Olivier, Pacot, Pierre 27 May 2022 (has links)
The voltage of the fuel cell must be measured during the test phase to characterize and condition it. Similarly, monitoring the fuel cell during its operation in series has many advantages. The CVM is a permanent and individualized measurement system for each cell. DAM has developed a universal system that can be connected to any type of bipolar plate. In addition, its modularity allows it to adapt to the number of cells and the fuel cell voltage, while compensating deformation phenomena. Moreover, its electronic architecture also allows a great modularity while proposing additional functions of diagnosis and measurements of insulation and short-circuit. These features are essential for the mass production of the CVM and the automated assembly of the CVM on the fuel cell, ensuring a cost competitive solution. / Die Spannung der Brennstoffzelle muss während der Testphase gemessen werden, um sie zu charakterisieren und zu konditionieren. Auch die Überwachung der Brennstoffzelle während ihres Serienbetriebs hat viele Vorteile. Das CVM ist ein permanentes und individuelles Messsystem für jede einzelne Zelle. DAM hat ein universelles System entwickelt, das an jede Art von Bipolarplatte angeschlossen werden kann. Außerdem kann es aufgrund seiner Modularität an die Anzahl der Zellen und die Brennstoffzellenspannung angepasst werden, wobei Verformungsphänomene kompensiert werden. Darüber hinaus ermöglicht seine elektronische Architektur eine große Modularität und bietet zusätzliche Diagnosefunktionen und Messungen für Isolation und Kurzschluss. Diese Merkmale sind für die Massenproduktion des CVM und die automatisierte Montage des CVM auf der Brennstoffzelle von wesentlicher Bedeutung und ermöglichen eine kostengünstige Lösung.
129

Nanostructuring noble metals as unsupported electrocatalysts for polymer electrolyte fuel cells

Cai, Bin, Henning, Sebastian, Herranz, Juan, Schmidt, Thomas J., Eychmüller, Alexander 28 December 2018 (has links)
Two major challenges that impede fuel cell technology breakthrough are the insufficient activity of the electrocatalysts for the oxygen reduction reaction and their degradation during operation, caused by the potential-induced corrosion of their carbon-support upon fuel cell operation. Unsupported electrocatalysts derived from tailored noble-metal nanostructures are superior to the conventional carbon-supported Pt nanoparticle catalysts and address these barriers by fine-tuning the surface composition and eliminating the support. Herein, recent efforts and achievements in the design, synthesis and characterization of unsupported electrocatalysts are reviewed, paying special attention to noble-metal aerogels, nano/meso-structured thin films and template-derived metal nanoarchitectures. Their electrocatalytic performances for oxygen reduction are compared and discussed, and examples of successful catalyst transfer to polymer electrolyte fuel cells are highlighted. This report aims to demonstrate the potential and challenges of implementing unsupported catalysts in fuel cells, thereby providing a perspective on the further development of these materials.
130

Tiefdruckverfahren zur Herstellung von Katalysatorschichten für (PEM) Brennstoffzellen / Gravure Printing as Manufacturing Technology for Catalyst Layers of (PEM) Fuel Cells

Siegel, Frank 06 June 2016 (has links) (PDF)
Diese Dissertation befasst sich mit der industrienahen Herstellung von Katalysatorschichten für Polymer-Elektrolyt-Membran-Brennstoffzellen mit Hilfe des Tiefdrucks als Fertigungsverfahren. Um die Anforderungen an die Katalysatorschicht hinsichtlich der Schichtdicke zu erreichen, wird ein Linienraster für den Tiefdruck entwickelt. Das patentierte und verifizierte Designkonzept des Linienrasters ermöglicht es, trotz Tinten mit geringem Feststoffgehalt hohe Trockenschichtdicken zu erzeugen. Aufgrund des verwendeten Tiefdruckrasters sind Optimierungsschritte an der Fertigungsanlage notwendig, um eine hohe Schichtqualität zu erreichen. Schließlich werden kontinuierlich und industrienah Katalysatorschichten gefertigt, die als Membran-Elektroden-Einheit in einer Polymer-Elektrolyt-Membran-Brennstoffzelle erfolgreich eingesetzt werden. / This work presents an industrial close manufacturing process of active electrodes for Polymer Electrolyte Fuel Cells utilizing an adapted gravure printing process. To meet the requirements of the electrodes regarding the layer thickness (weight) and quality a novel line screen with maximized dipping volume for gravure printing was developed and investigated. A design rule for this kind of screens was realized and verified by a successful manufacturing of electrodes with different dried layer thicknesses. Due to the rough structure and the high dipping volumes of these line screens an adaption and optimization of the machinery and the whole process was necessary to achieve high quality electrodes. Finally, it is shown that it is possible to manufacture continuiously in an industrial close roll-to-roll process platinum loaded electrodes, working successful as cathode in a Membran-Electrode-Assembly.

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