10 research outputs found
GAS CIRCUIT SYSTEM FOR HEAT TRANSPORT
No full textDie Erfindung betrifft ein Gaskreislaufsystem (1) für den Transport von Wärme von einer Hochtemperaturquelle (5) zu einem Wärmeverbraucher (7), aufweisend ein Rohrsystem (2), durch das ein gasförmiges Wärmeaustauschmedium strömt, wobei ein Teil des Rohrsystems (2) als an die Hochtemperaturquelle (5) angeschlossener Wärmetauscher (4) ausgebildet ist, in dem Wärme aus der Hochtemperaturquelle (5) in das Wärmeaustauschmedium übertragen wird, und wobei ein Teil des Rohrsystems (2) als Wärmesenke (6), in der die auf das Wärmeaustauschmedium übertragene Wärme auf einen Wärmeverbraucher (7) übertragbar ist, oder als Wärmeverbraucher ausgebildet ist. In dem Rohrsystem (2) sind ein oder mehrere nach dem Coandä-Effekt und/oder dem Venturi-Effekt arbeitende Gasströmungsverstärker (8) vorgesehen, die mit unter Druck stehendem Impulsgas gespeist sind, um das Wärmeaustauschmedium in dem Rohrsystem (2) in einer Strömungsrichtung (3) anzutreiben
Scale-up of milling in a 100 liter device for processing of FeTiMn alloy for hydrogen storage applications: procedure and characterization
No full textIn this work, the mechanical milling of a FeTiMn alloy for hydrogen storage purposes was performed in an industrial milling device. The TiFe hydride is interesting from the technological standpoint because of the abundance and the low cost of its constituent elements Ti and Fe, as well as its high volumetric hydrogen capacity. However, TiFe is difficult to activate, usually requiring a thermal treatment above 400 °C. A TiFeMn alloy milled for just 10 min in a 100 L industrial milling device showed excellent hydrogen storage properties without any thermal treatment. The as-milled TiFeMn alloy did not need any activation procedure and showed fast kinetic behavior and good cycling stability. Microstructural and morphological characterization of the as-received and as-milled TiFeMn alloys revealed that the material presents reduced particle and crystallite sizes, even after such short time of milling. The refined microstructure of the as-milled TiFeMn is deemed to account for the improved hydrogen absorption-desorption properties
Modeling the kinetic behavior of the Li-RHC system for energy-hydrogen storage: (I) absorption
Get PDFThe Lithium–Boron Reactive Hydride Composite System (Li-RHC) (2 LiH + MgB2/2 LiBH4 + MgH2) is a high-temperature hydrogen storage material suitable for energy storage applications. Herein, a comprehensive gas-solid kinetic model for hydrogenation is developed. Based on thermodynamic measurements under absorption conditions, the system's enthalpy ΔH and entropy ΔS are determined to amount to −34 ± 2 kJ∙mol H2−1 and −70 ± 3 J∙K−1∙mol H2−1, respectively. Based on the thermodynamic behavior assessment, the kinetic measurements' conditions are set in the range between 325 °C and 412 °C, as well as between 15 bar and 50 bar. The kinetic analysis shows that the hydrogenation rate-limiting-step is related to a one-dimensional interface-controlled reaction with a driving-force-corrected apparent activation energy of 146 ± 3 kJ∙mol H2−1. Applying the kinetic model, the dependence of the reaction rate constant as a function of pressure and temperature is calculated, allowing the design of optimized hydrogen/energy storage vessels via finite element method (FEM) simulations
Engineering Solutions in Scale-up and Tank Design for Metal Hydrides
No full textA holistic approach is required for the development of materials and systems for hydrogen storage, embracing all the different steps involved in a successful advance of the technology.
The several engineering solutions presented in this work try to address the technical challenges in synthesis and application of solid-state hydrogen storage materials, mainly metal hydride based compounds.
Moving from the synthesis of samples in lab-scale to the production of industrial sized batches a novel process development is required, including safety approaches (for hazardous powders), and methods to prevent the contamination of sensitive chemicals. The reduction of overall costs has to be addressed as well, considering new sources for raw materials and more cost-efficient catalysts.
The properties of the material itself influence the performances of the hydride in a pilot storage tank, but the characteristics of the system itself are crucial to investigate the reaction limiting steps and overcome hindrances. For this, critical experiments using test tanks are needed, learning how to avoid issues as material segregation or temperature gradients, and optimizing the design in the aspects of geometry, hull material, and test station facilities.
The following step is a useful integration of the hydrogen storage system into real applications, with other components like fuel cells or hydrogen generators: these challenging scenarios provide insights to design new experiments and allow stimulating demonstrations
Fundamental Material Properties of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage: (II) Kinetic Properties
No full textReaction kinetic behaviour and cycling stability of the 2LiBH4–MgH2 reactive hydride composite (Li-RHC) are experimentally determined and analysed as a basis for the design and development of hydrogen storage tanks. In addition to the determination and discussion about the properties; different measurement methods are applied and compared. The activation energies for both hydrogenation and dehydrogenation are determined by the Kissinger method and via the fitting of solid-state reaction kinetic models to isothermal volumetric measurements. Furthermore, the hydrogen absorption–desorption cycling stability is assessed by titration measurements. Finally, the kinetic behaviour and the reversible hydrogen storage capacity of the Li-RHC are discusse
Effect of the process parameters on the energy transfer during the synthesis of the 2LiBH4-MgH2 reactive hydride composite for hydrogen storage
No full textSeveral different milling parameters (additive content, rotation velocity, ball-to-powder ratio, degree of filling, and time) affect the hydrogen absorption and desorption properties of a reactive hydride composite (RHC). In this paper, these effects were thoroughly tested and analyzed. The milling process investigated in such detail was performed on the 2LiH-MgB2 system doped with TiCl3. Applying an upgraded empirical model, the transfer of energy to the material during the milling process was determined. In this way, it is possible to compare the obtained experimental results with those from processes at different scales. In addition, the different milling parameters were evaluated independently according to their individual effect on the transferred energy. Their influence on the reaction kinetics and hydrogen capacity was discussed and the results were correlated to characteristics like particle and crystallite size, specific surface area, presence of nucleation sites and contaminants. Finally, an optimal value for the transferred energy was determined, above which the powder characteristics do not change and therefore the RHC system properties do not further improve
Development of a Modular Room Temperature Hydride Storage System for vehicular applications
No full textThe subject of this paper concerns the development of a vehicular hydrogen tank system, using a commercial interstitial metal hydride as storage material. The design of the tank was intended to feed a fuel cell in a light prototype vehicle, and the chosen hydride material, Hydralloy C5 by GfE, was expected to be able to absorb and desorb hydrogen in a range of pressure suitable for this purpose. A systematic analysis of the material in laboratory scale allows an extrapolation of the thermodynamic and reaction kinetics data. The following development of the modular tank was done according to the requirements of the prototype vehicle propulsion system and led to promising intermediate results. The modular approach granted flexibility in the design, allowing both to reach carefully the design goals and to learn the limiting factors in the sorption process. Proper heat management and suitable equipment remain key factors in order to achieve the best performances
Fundamental Material Properties of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage: (I) Thermodynamic and Heat Transfer Properties
No full textThermodynamic and heat transfer properties of the 2LiBH4-MgH2 composite (Li-RHC) system are experimentally determined and studied as a basis for the design and development of hydrogen storage tanks. Besides the determination and discussion of the properties, different measurement methods are applied and compared to each other. Regarding thermodynamics, reaction enthalpy and entropy are determined by pressure-concentration-isotherms and coupled manometric-calorimetric measurements. For thermal diffusivity calculation, the specific heat capacity is measured by high-pressure differential scanning calorimetry and the effective thermal conductivity is determined by the transient plane source technique and in situ thermocell. Based on the results obtained from the thermodynamics and the assessment of the heat transfer properties, the reaction mechanism of the Li-RHC and the issues related to the scale-up for larger hydrogen storage systems are discussed in detail
Magnesium based materials for hydrogen based energy storage: Past, present and future
Get PDFMagnesium hydride owns the largest share of publications on solid materials for hydrogen storage. The “Magnesium group” of international experts contributing to IEA Task 32 “Hydrogen Based Energy Storage” recently published two review papers presenting the activities of the group focused on magnesium hydride based materials and on Mg based compounds for hydrogen and energy storage. This review article not only overviews the latest activities on both fundamental aspects of Mg-based hydrides and their applications, but also presents a historic overview on the topic and outlines projected future developments. Particular attention is paid to the theoretical and experimental studies of Mg-H system at extreme pressures, kinetics and thermodynamics of the systems based on MgH2, nanostructuring, new Mg-based compounds and novel composites, and catalysis in the Mg based H storage systems. Finally, thermal energy storage and upscaled H storage systems accommodating MgH2 are presented
