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Accumulation of energy in "heat batteries"
Janečka, Filip ; Kudela, Libor (referee) ; Pospíšil, Jiří (advisor)
Thermal energy storage is an important alternative to other, more common methods of energy storage, such as electrochemical batteries, as most of the energy used in homes is in the form of heat. The use of thermal energy storage therefore skips the step where electricity is converted into heat, which can increase the efficiency of the whole process and reduce energy costs. In this paper, five important thermal energy storage methods are described and evaluated with respect to their use by an individual in a single family home as well as for use in high energy demand applications (central heating, power generation, etc.). The five heat storage methods are: ground storage, sand storage, PCM (phase change material) storage, thermochemical storage and hydrogen storage. Emphasis is placed on highlighting the advantages and disadvantages of each type of thermal storage reservoir, showing pilot implementations and comparing them with each other. Furthermore, an evaluation of the seasonal storage capability of the different thermal storage systems is made, which shows that the only storage guaranteed to be capable of almost unlimited storage time is the thermochemical storage system. Also in this work, a water heat storage tank for a single-family house is proposed, which was chosen because of its good scalability, proven functionality and relatively simple design.
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Storage of hydrogen produced by electrolysis in a metal hydride
Hamřík, Lukáš ; Libich, Jiří (referee) ; Novák, Vítězslav (advisor)
In the theoretical part, this thesis focuses on the possibilities of producing hydrogen from renewable and non-renewable sources, mentioning their advantages and disadvantages. The work describes the properties and basic principles of several types of electrolysis technologies. Technological options for hydrogen storage in the gaseous, liquid and solid phases are listed, in particular with a focus on hydrogen storage in metal hydride storage sites. In practical part, the hydrogen system that was the subject of the measurement is described. Block diagrams and a description of the realisation of control and measurement system engagement are provided, and the method of reading and writing data using LabVIEW is described. The resulting measured temperature and pressure dependencies of the metal hydride storage, their comparison with theoretical knowledge, as well as the two possible modes in which the assembled hydrogen system can be operated are described below.
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Fuel cell with metal hydride hydrogen storage
Bruzl, David ; Libich, Jiří (referee) ; Novák, Vítězslav (advisor)
The bachelor thesis deals with hydrogen fuel cells and hydrogen storage. It describes the history of fuel cell development, the principle of their function and their individual types, with a focus on low-temperature fuel cells, especially the PEMFC type. Hydrogen storage methods are also described, with a focus on metal hydride storage. The design and assembly of the H-200 fuel cell system is described, its basic characteristics are measured and its differences from the manufacturer's characteristics are discussed. The discharge behavior of the HS-760 metal hydride storage system is also included. This behavior is measured by a program that was developed in the Labview environment. The thesis contains a description of this program. The program and the measured data are in the electronic appendices. One chapter of the thesis is also devoted to the operating modes of the whole system.
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PHASE COMPOSITION OF CHOSEN Mg-BASED MATERIALS DURING HYDROGEN SORPTION
Čermák, Jiří ; Král, Lubomír ; Roupcová, Pavla
Phase transformation during hydrogen sorption was investigated in ten chosen magnesium-based hydrogen storage (HS) materials. Chemical composition of the materials consisted of Mg, as a principal hydrogen-binding element, additive X and amorphous carbon (CB), as an anti-sticking component. In order to assess the effect of X itself upon the structure, values of concentration of both X and CB were fixed to about 12 wt. %. The influence of X = Mg2Si, Mg2Ge, Mg17Al12, Mg5Ga2, NaCl, LiCl, NaF, LiF and two combinations Ni+Mg17Al12 and Ni+Mg2Si upon the changes in phase composition was tested. Phase content in HS materials was observed (i) after the intensive ball milling (BM), (ii) after the BM followed by hydrogen charging at 623 K and (iii) after the BM and one hydrogen charging/discharging cycle (C/D) at temperature 623 K. The study was carried out by SEM and XRD. It was found that, the C/D is approximately structurally reversible for X = Mg2Ge, Mg17Al12, NaF and LiF. However, additives X = Mg17Al12 and NaF decompose already during the BM. In alloys with combination of Ni with Mg17Al12, new phases NimAln are formed. Phase composition changed during C/D for X = Mg2Si Mg5Ga2 and Ni+Mg2Si due to equilibration of phases composition. Observed structure changes of HS materials with chloride ionic additives NaCl and LiCl are, most likely caused by the relatively strong affinity between Mg and Cl. Hydrogen storage capacity of all studied alloys was 6.0 +/- 0.3 wt. % H-2.
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The hydrogen bus
Kopecký, Petr ; Březina, Michal (referee) ; Štětina, Josef (advisor)
This bachelor's thesis deals with the topic of hydrogen buses, their concept, properties, practical application and economics of operation. It also discusses safety and hydrogen infrastructure, in particular hydrogen production, storage and use, while mentioning future options. Various technical solutions are evaluated with regard to the specifics of buses. It thus offers a general overview of the topic of hydrogen buses and related infrastructure.
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HYDROGEN SORPTION IN ORDERED Mg-In ALLOYS
Čermák, Jiří ; Král, Lubomír ; Roupcová, Pavla
Hydrogen storage (HS) performance of three Mg- x In- y CB alloys (CB - amorphous carbon, x = 55, 64, 73 y =\n10 wt%) was studied. Indium concentration covered an area of ordered β structures. Alloys were prepared by\nball-milling in hydrogen atmosphere. Kinetic curves and PCT isotherms were measured in the temperature\ninterval from 200 °C to 325 °C. X-ray diffraction spectroscopy (XRD) was used for structure investigation. Alloy\nwith x = 73 wt% In ( β ’’ structure) showed reversible amorphization during temperature cycling between about\n100 °C and 350 °C. Hydrogen sorption experiments were done by the Sieverts method under the hydrogen\ngas pressure ranging from 0.1 MPa to 2.5 MPa. It was found that hydrogen sorption capacity varied between\n0.47 and 1.1 wt% H 2 . Hydride formation enthalpy ∆H calculated from desorption PCT experiments was\nsignificantly lower than ∆H , known for pure Mg. This invoked an idea that atomic order of Mg-based HS\nmaterials might decrease the high thermodynamic stability of hydride phase.
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HYDROGEN STORAGE PROPERTIES OF GRAPHENE OXIDE MATERIALS PREPARED BY DIFFERENT WAYS
Král, Lubomír ; Čermák, Jiří ; Bytesnikova, Z.
Graphene-based materials show unique properties. These single layered materials consist of 2D structure of carbon atoms, belong to the strongest known materials, that are very mechanically flexible, optically transparent and that are excellent electrical and thermal conductors. Recently, several studies on these types of materials have highlighted the potential of this material for hydrogen storage (HS) and raised new hopes for the development of an effective solid-state HS media. In the present paper, the structure and HS properties of graphene oxide (GO) and chemically reduced graphene oxide (rGO) produced by different procedures were studied. Hydrogen sorption characteristics of GO and rGO were measured using the Sieverts-type gas sorption analyzer PCT-Pro Setaram Instrumentation. The study of HS was carried out at temperature range from 198 K to 423 K under hydrogen pressure from 1x10(-4) to 4 MPa. \n\nFor the HS point of view, the advantage of GO or rGO compared to graphene, is the presence of multiple chemical groups that can be used for introducing modifiers and their superior spreading on the materials surface. The suitably functionalized GO or rGO materials could potentially exhibit outstanding HS properties.
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HYDROGEN STORAGE PROPERTIES OF GRAPHENE OXIDE MATERIALS PREPARED BY DIFFERENT WAYS
Král, Lubomír ; Čermák, Jiří ; Bytesnikova, Z.
Graphene-based materials show unique properties. These single layered materials consist of 2D structure of carbon atoms, belong to the strongest known materials, that are very mechanically flexible, optically transparent and that are excellent electrical and thermal conductors. Recently, several studies on these types of materials have highlighted the potential of this material for hydrogen storage (HS) and raised new hopes for the development of an effective solid-state HS media. In the present paper, the structure and HS properties of graphene oxide (GO) and chemically reduced graphene oxide (rGO) produced by different procedures were studied. Hydrogen sorption characteristics of GO and rGO were measured using the Sieverts-type gas sorption analyzer PCT-Pro Setaram Instrumentation. The study of HS was carried out at temperature range from 198 K to 423 K under hydrogen pressure from 1x10(-4) to 4 MPa.
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INFLUENCE OF GRAPHITE UPON THE KINETICS OF HYDROGEN SORPTION IN Mg@Mg17Al12
Čermák, Jiří ; Král, Lubomír ; Roupcová, Pavla
Influence of graphite addition to the ball-milling charge composed of Mg splinters and Mg17Al12 particles upon the hydrogen sorption was investigated at sorption temperature 623 K. Measurements were carried out by Sieverts method. Graphite facilitates the ball-milling: It prevents re-agglomeration of crushed particles into large secondary particles. It also suppresses sticking the milled material to the balls and walls of the milling jar. It was found that an increase of carbon concentration up to a certain limit c(L) lying between 14 and 23 wt. % C, carbon increases both the absorption and the desorption rates and hydrogen storage capacity. Above c(L), carbon causes a considerable decrease in HS capacity, which spoils the application potential of Mg@Mg17Al12/C. Crystallite size of the material under study, obtained by XRD, is in the order of tens of nm.
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ESTIMATION OF EQUILIBRIUM HYDROGEN PRESSURE - A NEW METHOD
Čermák, Jiří ; Král, Lubomír
A new method is proposed to estimation of hydrogen pressure in equilibrium with hydride phase in a hydrogen\nstorage material. It is applicable both for hydrogen absorption and desorption in cases where the hydride phase\nis formed by nucleation and growth mechanism. The proposed method saves considerably the experimental\ntime replacing the conventional time consuming measurement of pressure-composition isotherms, the so\ncalled PCT curves. The proposed evaluation procedure is illustrated using hydrogen chemi-sorption at\ntemperatures 623 K, 573 K and 523 K in chosen hydrogen storage alloys Mg-Si-C, Mg-Li-C and Mg-Na-C.
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