Development of Hydrogen Storage Systems using Sodium Alanate

134 Pages·2011·5.44 MB·English

HZG RepoRt 2011-1 // ISSN 2191-7833
Development of Hydrogen Storage
Systems using Sodium Alanate
(Vom Promotionsausschuss der Technischen Universität Hamburg-Harburg im Jahr 2010 als Dissertation angenommene Arbeit)
G. A. Lozano Martinez

HZG REPORT 2011-1
Development of Hydrogen Storage
Systems using Sodium Alanate
(Vom Promotionsausschuss der Technischen Universität Hamburg-Harburg im Jahr 2010 als Dissertation angenommene Arbeit)
G. A. Lozano Martinez
(Institut für Werkstoffforschung)
Helmholtz-Zentrum Geesthacht
Zentrum für Material- und Küstenforschung GmbH | Geesthacht | 2011
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ISSN 2191-7833
Helmholtz-Zentrum Geesthacht
Zentrum für Material- und Küstenforschung GmbH
Max-Planck-Straße 1
21502 Geesthacht
www.hzg.de
HZG REPORT 2011-1
Development of Hydrogen Storage Systems using Sodium Alanate
(Vom Promotionsausschuss der Technischen Universität Hamburg-Harburg im Jahr 2010 als Dissertation angenommene Arbeit)
Gustavo Adolfo Lozano Martinez
132 pages with 68 fi gures and 16 tables
Abstract
Hydrogen storage systems based on sodium alanate are studied, modelled, and optimised, on the basis of both
experimental and theoretical approaches. The experimental hydrogen sorption behaviour (kinetics, heat transfer
and cycling) of small cells up to kg-scale storage tanks is compared and analysed. In particular, the effect of the
size of the system, powder compaction, and addition of expanded graphite on the sorption behaviour is investigated
and characterized. In order to implement simulations and further evaluations, empirical kinetic models for both
hydrogen absorption and desorption of sodium alanate material are developed. The hydrogen sorption process in
a storage tank is modelled on the basis of the developed kinetic equations, hydrogen transport equations and heat
transfer equations. A numerical simulation is developed and validated with the experimental results previously
obtained in this work. Optimisation towards the gravimetric hydrogen storage capacity of a tubular storage tank
based on sodium alanate is defi ned and performed by means of the numerical simulation and the experimental
results of this work.
Entwicklung von Natriumalanat-basierten Wasserstoffspeichertanks
Zusammenfassung
Durch experimentelle und theoretische Methoden wurden Natriumalanat-Wasserstoffspeichertanks untersucht,
modelliert und optimiert. Das experimentelle Sorptionsverhalten (Kinetik, Wärmeübertragung, Zyklierung) von
kleinen Zellen bis hin zu Speichertanks im kg-Maßstab ist verglichen and analysiert worden. Hierbei wurde
insbesondere der Einfl uss der Größe des Systems, der Materialkompaktierung, und des Zusatzes von expandiertem
Graphit auf das Sorptionsverhalten erforscht und charakterisiert. Zu weiteren Evaluierungen und Simulationen
wurden empirische kinetische Modelle sowohl für Absorption als auch Desorption für den Fall von Natriumalanat
als Speichermaterial entwickelt. Der Wasserstoffsorptionsprozess in Speichertanks wurde mit Hilfe der entwickelten
kinetischen Gleichungen, Wasserstofftransport- und Wärmeübertragungsgleichungen modelliert. Eine numerische
Simulation wurde entwickelt, und durch die gefundenen experimentellen Ergebnisse dieser Arbeit validiert.
Mit Hilfe der erzielten Ergebnisse und der Simulation wurde das Design eines auf Natriumalanat basierenden
Wasserstoffspeichertanks in Bezug auf die gravimetrische Kapazität optimiert.
Manuscript received / Manuskripteingang in TFP: 19. Januar 2011

Acknowledgements
To all Professors, tutors and teachers, to my colleagues, my friends and all of my family, who both
directly and indirectly inspired, shared and encouraged my desire to work in this doctoral thesis, to all
and every one of you my grateful acknowledgement and sincere thanks.
I want to express my thanks to Prof. Rüdiger Bormann for his guidance and advice, for the
constructive periodic discussions, from which I learned how to develop a deeper phenomenological
perspective and how to separate objective observations from subjective points of view.
Especially I want to express my deep gratitude to Dr. Martin Dornheim for his friendly and direct
supervision and his support during all my PhD work at the Department of Nanotechnology at the
GKSS Research Centre (today Helmholtz-Zentrum Geesthacht). I want to thank him for believing in
my ideas, my work and my character. Thanks for promoting that pleasant work atmosphere in the
department, which has achieved amazing results as it will continue for sure.
I would like to thank as well Prof. Thomas Klassen not only for his role as reviewer and evaluator of
my thesis but also for his former work and energy invested in the development of the department of
Nanotechnology, encouraging the research from new scientists in the field of hydrogen technology.
For all the help and collaboration during my work on modelling and simulation I would like to give a
special acknowledgement to Prof. Georg Fieg, Prof. Jobst Hapke, Dr. Chakkrit Na Ranong and all the
staff of the Institute of Process and Plant Engineering at the Hamburg University of Technology. I
appreciate very much the collaboration of Dr. Na Ranong, the long discussion times and his invaluable
feedback and friendly advice.
Many of the results of my research would not have been possible without the collaboration of the
students from the Helmut Schmidt University: Stefan Walcker-Mayer, Stephan Dorn and Daniel
Meyer, and from the DAAD Rise Program: Daniel Martin-Alarcon, Simon Thompson and Craig
Holvey. I appreciate the financial support of the European Community in the frame of the Integrated
Project “NESSHY—Novel Efficient Solid Storage for Hydrogen” and of the Helmholtz Initiative
“FuncHy—Functional Materials for Mobile Hydrogen Storage”.
At the department of Nanotechnology I was lucky to work under a constant motivating and friendly
atmosphere, which made every day a very nice experience. My thanks to all current and former
outstanding colleagues: Ulrike Bösenberg (my phenomenal office mate), Dr. José Bellosta von Colbe
(for his nice support and suggestions), Oliver Metz, Claudio Pistidda, Julian Jepsen, Christian
Bonatto-Minella, Anna Arendarska, Dr. Rapee Gosalawit, Dr. Ivan Saldan, Dr. Klaus Taube, Dr.
Karina Suárez, Christian Horstmann, Dr. Michael Störmer, Dr. Gagik Barkhordarian, Julian Puszkiel,
Fahim Karimi, Sabine Schrader, Liane Bellosta von Colbe and Prof. Michael Dahms. I am very
thankful to Dr. Nico Eigen for the initial supervision and introduction to the topic of complex hydrides
during the early stage of my thesis.
I thank my parents, Gustavo and Julia, for their commitment in my education and the freedom I
enjoyed in having independent ideas. I thank also my brother and sister, Gabriel y Cristina, for their
constant patience and moral support in my life.
This dissertation is dedicated above all to my lovely wife Gabriela, who is and was my inspiration and
strength during all this time, who changed my life for good and whom I owe the successful and
peaceful development, writing and finish of this thesis. Muchas gracias Gaby.

Geesthacht, December 2010
Contents
1 INTRODUCTION.......................................................................................................................................1
1.1 HYDROGEN AS SOLAR ENERGY CARRIER...............................................................................................1
1.2 HYDROGEN STORAGE: METAL HYDRIDES AS HIGH DENSITY ALTERNATIVE...........................................2
1.3 SCOPE AND STRUCTURE OF THE PRESENT WORK...................................................................................5
1.4 MODEL SYSTEM: SODIUM ALANATE......................................................................................................7
2 EXPERIMENTAL METHODS.................................................................................................................9
2.1 MATERIAL PREPARATION......................................................................................................................9
2.2 SORPTION KINETICS............................................................................................................................10
2.3 HYDROGEN TANK STATION.................................................................................................................11
3 EXPERIMENTAL SORPTIONS: KINETICS AND HEAT TRANSFER...........................................17
3.1 EFFECTS OF HEAT TRANSFER ON THE SORPTION KINETICS...................................................................17
3.1.1 Absorption in cells of different sizes.............................................................................................17
3.1.2 Absorptions in the thermocell.......................................................................................................18
3.1.3 Estimation of effective thermal conductivity................................................................................18
3.1.4 Addition of expanded graphite......................................................................................................20
3.1.5 Discussion.....................................................................................................................................21
3.2 EMPIRICAL KINETIC MODEL OF SODIUM ALANATE REACTING MATERIAL: HYDROGEN ABSORPTION....30
3.2.1 Kinetic equations...........................................................................................................................31
3.2.2 Experimental approach..................................................................................................................34
3.2.3 Isobaric and isothermal conditions during measurements.............................................................35
3.2.4 Hydrogen absorption of NaH+Al to form Na AlH : S S ...................................................37
3 6 I II
3.2.5 Hydrogen absorption of Na AlH +Al to form NaAlH : S S ............................................38
3 6 4 II III
3.2.6 Discussion.....................................................................................................................................40
3.2.6.1 Hydrogen absorption of NaH+Al to form NaAlH: S S .......................................................40
3 6 I II
3.2.6.2 Hydrogen absorption of Na AlH+Al to form NaAlH: S S ................................................42
3 6 4 II III
3.2.6.3 Empirical kinetic model and validation...............................................................................................43
3.3 EMPIRICAL KINETIC MODEL OF SODIUM ALANATE REACTING MATERIAL: HYDROGEN DESORPTION....46
3.3.1 Kinetic equations...........................................................................................................................47
3.3.2 Experimental approach..................................................................................................................47
v
3.3.3 Hydrogen desorption of NaAlH forming Na AlH +Al: S S ...........................................48
4 3 6 III II
3.3.4 Hydrogen desorption of Na AlH forming NaH+Al: S S ..................................................49
3 6 II I
3.3.5 Discussion.....................................................................................................................................51
3.3.5.1 Hydrogen desorption of NaAlH forming Na AlH+2Al: S S .............................................51
4 3 6 III II
3.3.5.2 Hydrogen desorption of Na AlH forming NaH+Al: S S ......................................................54
3 6 II I
3.3.5.3 Kinetic model and validation...............................................................................................................57
3.4 SCALED-UP SORPTIONS.......................................................................................................................58
3.4.1 Hydrogenation of Hydralloy C5....................................................................................................59
3.4.2 Hydrogenation of sodium alanate material....................................................................................61
3.4.3 Addition of expanded graphite......................................................................................................63
3.4.4 Discussion.....................................................................................................................................63
4 MODELLING AND SIMULATION: HYDROGEN SORPTION IN PRACTICAL SYSTEMS
BASED ON METAL HYDRIDES.....................................................................................................................69
4.1 MODEL EQUATIONS OF A HYDRIDE BED AND ANALYSIS OF SORPTION RATE LIMITING SUB-PROCESS..69
4.1.1 Hydrogen transport........................................................................................................................69
4.1.2 Chemical reaction..........................................................................................................................70
4.1.3 Heat transfer..................................................................................................................................71
4.1.4 Sorption-rate limiting sub-process in a hydride bed......................................................................71
4.2 FINITE ELEMENT SIMULATION OF THE HYDROGEN SORPTION OF SODIUM ALANATE MATERIAL...........76
4.2.1 Procedure of the simulation...........................................................................................................77
4.2.2 Intrinsic kinetics: absorption model..............................................................................................79
4.2.3 Intrinsic kinetics: desorption model..............................................................................................81
4.2.4 Simulation predictions...................................................................................................................82
4.2.5 Discussion.....................................................................................................................................85
5 OPTIMISED HYDROGEN STORAGE SYSTEMS WITH SODIUM ALANATE MATERIAL.....87
5.1 OPTIMISING VOLUMETRIC HYDROGEN DENSITY BY COMPACTION.......................................................87
5.1.1 Compacts manufacture..................................................................................................................88
5.1.2 Sorption kinetics............................................................................................................................89
5.1.3 Apparent density through cycling.................................................................................................90
5.1.4 Discussion.....................................................................................................................................91
5.2 OPTIMISATION OF TUBULAR STORAGE TANKS BASED ON SODIUM ALANATE MATERIAL......................93
5.2.1 Definition of the tubular tank optimisation...................................................................................94
5.2.1.1 Calculation of the tank wall thickness.................................................................................................95
5.2.1.2 Physical and transport properties of the hydride bed...........................................................................95
5.2.2 Results...........................................................................................................................................97
5.2.3 Discussion.....................................................................................................................................98
vi