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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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Study of elektrode materials based on manganese dioxide
Kos, Lukáš ; Dvořák, Petr (referee) ; Novák, Vítězslav (advisor)
This work deals with the production and use of catalytic materials in fuel cells. The basic focus of work is the production of samples of catalytic materials based on manganese dioxide-enriched mixtures of different dopants. Samples subsequently made to measure, compare with other samples and determine whether the samples are enriched with dopants better than samples without dopant. According to information received, then determine whether they are suitable for use in fuel cells.
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Low Temperature Fuel Cells H2-O2 with Anionic and Bipolar Membrane
Barath, Peter ; Sedlaříková, Marie (advisor)
The doctoral thesis deals with investigation of the catalysts and ionexchanege membranes for fuel cells H2-O2. The work contains the basic principles of chemical reactions, thermodynamic aspects and kinetic properties in PEM fuel cells.Ion-exchagers based on fluorinated polymer sulfonic acids known as NAFION are used in most cases. These compounds are very expensive. Also a strong corrosive attribute requires platinum as a catalysator. These facts make the membrane fuel cells fully non-competetive with e.g. internal combustion engine in spite of all ecological advantages of this electrical power source. The subject of doctoral thesis is research and development of compounds for the composite electrode materials base on NiOx, Ni-Pd and Raney Ni suitable as catalysts a nd alkaline or bipolar ionexchange membranes for electrochemical fuel cells.
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Hydrogen production from renewable energy source
Lakva, Petr ; Baláš, Marek (referee) ; Jícha, Jaroslav (advisor)
Hydrogen, as a form of storage for the excess energy from renewable sources, is a technically and economically viable option. However, the technology is not mature enough to compete with the other renewable energy possibilities. In this thesis, a study based on coupling two 330 kW wind-turbines with an NELP. 40 electrolyzer this connection should improve the utilization of wind power. In this thesis are two options of energy utilization. The energy produced by the wind-turbine is stored in the form, of hydrogen and is then delivered for consumption at variable power through a fuel cell, second option is use of produced hydrogen as alternative fuel for cars. This study is a general introduction for the wind energy system with hydrogen storage. Future studies should be more complex and detailed in order to understand and model the system with greater accuracy and to increase the possibility for the utilization of wind energy to generate hydrogen. This would enhance wind power competitiveness and sustain the continuously changing world energy demands.
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Measurement module based on electrochemical impedance spectroscopy intended for hydrogen fuel cell research
Přecechtěl, Vít ; Pazdera, Ivo (referee) ; Procházka, Petr (advisor)
This thesis deals with diagnostic fuel-cell parameters using electrochemical impedance spectroscopy. The document begins with brief explanation of fuel-cell operation and its basic principles. Thesis continues with description of fuel-cell voltage generation and influence of charge dual-layer on impedance. After that electrochemical impedance spectroscopy, signals used for perturbation and evaluation of impedance spectrum using Bode a Nyquist plot is described. Next part explains measurement of impedance spectrum using potentiostat in combination with lock-in amplifier or frequency response analyzer. Practical part of thesis is dedicated to electric circuit design of EIS module and software designed for automatic measurement of impedance spectrum. Last part shows results of EIS module testing.
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Optimalization of MEA structure for low temperature fuel cells
Chladil, Ladislav ; Novák, Vítězslav (referee) ; Barath, Peter (advisor)
This master’s thesis focuses on optimization of electrode configuration in combination with a polymer membrane (MEA - Membrane Electrode Assembly) in terms of material and technology. The main goal was to create a functional measurement of MEA structures with three different types of carbon materials. The theoretical part focuses on the physical and chemical properties of low-temperature fuel cells with polymer membrane. The experimental section describes the manufacture of catalytic materials with different types of carbon and various contents platinum. Produced by electrode materials were investigated by cyclic voltammetry. The next step was to manufacture MEA structures and characteristics of VA measurement using a digitally controlled load in the experimental fuel cell Quintech.
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Alternative energy sources
Stránský, Jaroslav ; Moskalík, Jiří (referee) ; Škvařil, Jan (advisor)
In this work, I tried to summarize the current state of world energy resources that we use to convert into electrical energy. There is solved the question of compensation running short supplies of fossil fuels and reduce discharge of greenhouse gasses. I´m looking for suitable compensation in department of alternative energy sources, among which I included the power of the Sun, water, wind, geothermal energy, using heat pumps, combustion energy, nuclear energy, fuel cells and hydrogen use. About anyone of replacing sources you learn about its history, advantages and disadvantages, the principle of function energy transform devices, and compare the potential that is available in the CR and in the world.
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