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Thermodynamic modelling of hydrogen fuel cells
Nováček, Marek ; Pavelka, Michal (advisor) ; Němec, Tomáš (referee)
In this thesis, proton exchange membrane fuel cells are studied. At the beginning, the ideas underlying their function are exposed and some possibilities of usage are pre- sented. Thereafter, we aim to describe the processes inside the fuel cells with the aid of thermodynamics and in agreement with constitutive relations that have been obtained experimentally. Namely, we are interested in the fluxes of water and protons inside the membrane, where they are acted upon by thermodynamic forces, and the electrochemical reactions at the electrodes, which can be described by the Butler-Volmer equations. Also do we study the efficiency of the fuel cell by evaluating the production of entropy due to the diverse processes that take place in the fuel cell. It is the goal of the computational part of this thesis to propose a zero-dimensional model and compare it with the results provided in the supervisor's doctoral thesis. 1
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Technologies for use hydrogen from Energiepark Mainz
Florian, Tibor ; Šnajdárek, Ladislav (referee) ; Škorpík, Jiří (advisor)
The goal of this bachelor’s thesis is the description of hydrogen, its production methods, subsequent use and comparison by selected criteria. In the beginning of the thesis, hydrogen is described as an element. The following chapter briefly deals with its history in energy industry and the most commonly used production technologies. The emphasis is on a Power-to-Gas facility, Energiepark Mainz. In the end, hydrogen is compared as a fuel in the automotive industry.
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Thermodynamic analysis of processes in Hydrogen fuel cells.
Pavelka, Michal
Non-equilibrium thermodynamics, which serves as a framework for formulating evolution equations of macroscopic and mesoscopic systems, is briefly reviewed and further developed in this work. For example, the relation between the General Equation for the Nonequilibrium Reversible- Irreversible Coupling (GENERIC) and (ir)reversibility is elucidated, and Onsager-Casimir reciprocal relations are shown to be an implication of GENERIC. Non-equilibrium thermodynamics is then applied to describe fuel cells and related devices, and theoretical conclusions are compared to experimental data. Moreover, a generalization of standard exergy analysis is developed bringing a new method for revealing a map of useful work losses in electricity producing devices. This method requires a non-equilibrium thermodynamic model, and so the general theory of non- equilibrium thermodynamics and optimization of real power generating devices stand side by side.
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Optimization of operation of renewable electric energy sources based on fuel cells, accumulators and FV panels for small powers.
Holeček, Martin ; Maršík, František (advisor) ; Beran, Zdeněk (referee)
The first part of the research is motivated to provide citations deeper to the literature of optimal control principles that could be linked to the system optimization problem, discuss these principles and various ways to apply them. Then we describe one fuel cell, accumulator and photovoltaic standalone system along with the most used equations from the literature. Next, we formulate the problem of optimal control for this system to optimize the system financial cost in the best case and we process to describe and discuss the numerical optimal control algorithm - multiple shooting - that will be used to solve the problem, that was not used in literature so far in conjunction with the problem. The codes and numerical simulations are also provided. Powered by TCPDF (www.tcpdf.org)
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Physical analysis of the main processes in the solid oxide fuel cells and their mathematical description
Vágner, Petr ; Maršík, František (advisor) ; Souček, Ondřej (referee)
Solid oxide fuel cells (SOFC) are mainly used as large stationary elec- tricity sources, therefore an every little improvement in their performance leads to considerable savings. In order to understand the fundamentals of the SOFC operation, we have developed a new model describing the main physical processes. The thermodynamical model of SOFC, developed in this thesis, concerns the gas transport, the transport of the charged particles in- cluding the thermoelectric effect and the electrochemical reactions. Linear irreversible thermodynamics is the key modelling framework, in which the dusty gas model and the Butler-Volmer equations are used. A new relation between the electrochemical affinity and the overpotential is introduced into the Butler-Volmer equation. A weakly formulated statinonary system en- dowed with boundary conditions is solved with the finite element method in one dimensional approximation. 1
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Thermodynamic analysis of processes in Hydrogen fuel cells.
Pavelka, Michal ; Maršík, František (advisor) ; Grmela, Miroslav (referee) ; Sciacovelli, Adriano (referee)
Non-equilibrium thermodynamics, which serves as a framework for formulating evolution equations of macroscopic and mesoscopic systems, is briefly reviewed and further developed in this work. For example, the relation between the General Equation for the Nonequilibrium Reversible- Irreversible Coupling (GENERIC) and (ir)reversibility is elucidated, and Onsager-Casimir reciprocal relations are shown to be an implication of GENERIC. Non-equilibrium thermodynamics is then applied to describe fuel cells and related devices, and theoretical conclusions are compared to experimental data. Moreover, a generalization of standard exergy analysis is developed bringing a new method for revealing a map of useful work losses in electricity producing devices. This method requires a non-equilibrium thermodynamic model, and so the general theory of non- equilibrium thermodynamics and optimization of real power generating devices stand side by side.
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Design of the autonomous snow groomer
Vespalec, Arnošt ; Surman, Martin (referee) ; Škaroupka, David (advisor)
The subject of this master’s thesis is the design of an autonomous snow groomer intended for the treatment of well-geodetically mapped slopes of ski resorts. Designed design uses an innovative approach to detecting the thickness of a snow cover by an electromagnetic sensor system. The work identifies and presents the concept of solving specific problems of autonomous operation in ski areas, in the form of a design vision. This concept is presented and verified using a parametric model.
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Termodynamická analýza procesů v palivových článcích s pevnými oxidy
Vágner, Petr ; Maršík, František (advisor) ; Némec, Tomáš (referee)
The fuel cells are the technology of the future. Although their discovery dates back to the 19th century the nature of how they work hasnt been adequately explained so far. This thesis focuses on description of solid oxides fuel cells (SOFC) for which ion conductive electrolyte and high operating temperature are distinctive. The mathematical model of SOFC developed in this thesis is formulated in terms of the mixture theory. The model development was constrained and simplified by isothermality, time-stationery and 1D approximation. The model equations characterize gas and ion transport and electric current flow in the fuel cell. Eventually comparison of the thesis model equations with the SOEC (solid oxides electrolysis cell) model developed at the Institute of Chemical Technology in Prague showed that both approaches lead to a similar conclusion. This thesis can be used as a basis for an experimental verification of the mixture theory. 1
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Termodynamická analýza procesů v polymerní elektrolytické membráně palivového článku
Pavelka, Michal ; Maršík, František (advisor) ; Málek, Josef (referee)
Thermodynamic analysis of processes in electrolytic fuel cell membrane Michal Pavelka April 12, 2012 Abstract Hydrogen fuel cells1 may become a key technology of 21st century, and it is important to be able to describe their behavior, therefore. In this work we focus on hydrogen fuel cells with a polymer-electrolyte membrane. For the membrane we adopt an existing model2 . We for- mulate the model in the framework of the mixture theory which we develop similarly as has been done in the classical textbook of Mazur and de Groot3 . However, refining the concept of potential energy of a material point, we introduce new terms called internal potential ener- gies which enable us to describe macroscopic consequences of internal forces between water and polymer in the membrane and to describe the influence of gradient of surface tension of water in the membrane. We solve the model in 1D approximation. Consequently, we calculate the influence processes in the membrane have on efficiency of the fuel cell. 1 see for example Larminie, J. and A. Dicks. Fuel Cell Systems Explained. 2nd edition. John Wiley & Sons Ltd., 2003. ISBN 0-470-84857-X. 2 Weber, A. Z. and J. Newman. Transport in Polymer-Electrolyte Membranes I, II, III. J. Electrochem. Soc., 150 (7), A1008-A1015, 2003; 151 (2), A1311-A1325, 2004.; 151 (2), A1326-A1339,...
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Effect of compaction pressure to the electrochemical properties of the electrodes for Li-S accumulators
Jaššo, Kamil ; Tichý, Jiří (referee) ; Kazda, Tomáš (advisor)
The purpose of this diploma thesis is to describe the impact of compaction pressure on the electrochemical parameters of lithium-sulfur batteries. Theoretical part of this thesis contains briefly described terminology and general issues of batteries and their division. Every kind of battery is provided with a closer description of a specific battery type. A separate chapter is dedicated to lithium cells, mainly lithium-ion batteries. Considering various composition of lithium-ion batteries, this chapter deeply analyzes mostly used active materials of electrodes, used electrolytes and separators. Considering that the electrochemical principle of Li-S and Li-O batteries is different to Li-ion batteries, these accumulators of new generation are included in individual subhead. In the experimental part of this thesis are described methods used to measure electrochemical parameters of Li-S batteries. Next chapter contains description of preparing individual electrodes and their composition. Rest of the experimental part of my thesis is dedicated to the description of individual experiments and achieved results.
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