Hydrogen Generation via Hydrolysis of Metal Hydrides...Hydrolysis Reactor Recuperation of Water...
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Alkaline battery 5 ct / Wh Li-SOCl 2 battery 60 ct / Wh NaH (η = 0.45) 16 ct / Wh Diesel (η = 0.15) 0.1 ct / Wh Methanol (η = 0.40) 0.05 ct / Wh MgH 2 (η = 0.45) 12 ct / Wh LiH (η = 0.45) 11 ct / Wh Electric energy density Wh / kg Wh / ℓ 0 1000 2000 3000 4000 191 760 1259 1890 2240 2295 3800 478 1220 1450 1572 1774 2607 2371 HYDROGEN GENERATION VIA HYDROLYSIS OF METAL HYDRIDES 1 Metal hydride powders and surface activation through ball milling 2 Lab-scale testing of different catalysts 3 Electric energy densities and costs of various storage materials Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM Branch Lab Dresden Winterbergstrasse 28 01277 Dresden | Germany Contact Dr. rer. nat. Lars Röntzsch Phone: +49 351 2537 411 E-mail: Lars.Roentzsch @ifam-dd.fraunhofer.de Dr. rer. nat. Marcus Tegel Phone: +49 351 2537 413 E-mail: Marcus.Tegel @ifam-dd.fraunhofer.de Fax: +49 351 2537 399 www.h2materials.de www.ifam-dd.fraunhofer.de 2 3 Hydrolysis of Metal Hydrides Hydrogen is an environmentally friendly energy carrier with a very high gravi- metric energy density. Its chemical energy can be readily converted to electrical energy by means of fuel cells. However, direct storage of pressurized H 2 is difficult as it involves expensive, heavy and bulky tanks as well as safety fittings, which goes far beyond the requirements for many portable applications. In low power applications especially, diffusion losses limit the direct storage of hydrogen. Metal hydrides as lightweight, compact, non-volatile, safe and reasonably priced compounds overcome these issues. In combination with water they can thus serve as energy sources similar to conven- tional or special batteries (e.g. Li-SOCl 2 ) but with a gravimetric and volumetric energy density at least one order of magnitude higher. Applications • backup / emergency power supplies • standalone radiocommunication • beacons • sensors • probes Properties of Lightweight Metal Hydrides • NaH - gravimetric H 2 density of 8.4 % *) - electric energy density 1259 Wh/kg *) - very fast hydrolysis kinetics • MgH 2 - gravimetric H 2 density 15.3 % *) - electric energy density 2295 Wh/kg *) - slow hydrolysis kinetics • LiH - gravimetric H 2 density 25.4 % *) - electric energy density 3800 Wh/kg *) - fast hydrolysis kinetics *) under the assumption that H 2 O is recuperated / available in excess 2 1 FRAUNHOFER INSTITUTE FOR MANUFACTURING TECHNOLOGY AND ADVANCED MATERIALS IFAM, BRANCH LAB DRESDEN
Transcript of Hydrogen Generation via Hydrolysis of Metal Hydrides...Hydrolysis Reactor Recuperation of Water...
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Alkalinebattery
5 ct / Wh
Li-SOCl2battery
60 ct / Wh
NaH(η = 0.45)16 ct / Wh
Diesel(η = 0.15)
0.1 ct / Wh
Methanol(η = 0.40)
0.05 ct / Wh
MgH2(η = 0.45)12 ct / Wh
LiH(η = 0.45)11 ct / Wh
Electric energy density
Wh / kg Wh / ℓ
0
1000
2000
3000
4000
191
760
1259
1890
2240 2295
3800
478
12201450
15721774
2607
2371
HYDROGEN GENERATION VIA HYDROLYSIS OF METAL HYDRIDES
1 Metal hydride powders and surface
activation through ball milling
2 Lab-scale testing of different catalysts
3 Electric energy densities and costs of
various storage materials
FraunhoferInstitutefor
ManufacturingTechnology
andAdvancedMaterialsIFAM
BranchLabDresden
Winterbergstrasse 28
01277 Dresden | Germany
Contact
Dr. rer. nat. Lars Röntzsch
Phone: +49 351 2537 411
E-mail: Lars.Roentzsch
@ifam-dd.fraunhofer.de
Dr. rer. nat. Marcus Tegel
Phone: +49 351 2537 413
E-mail: Marcus.Tegel
@ifam-dd.fraunhofer.de
Fax: +49 351 2537 399
www.h2materials.de
www.ifam-dd.fraunhofer.de
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HydrolysisofMetal
Hydrides
Hydrogen is an environmentally friendly
energy carrier with a very high gravi-
metric energy density. Its chemical energy
can be readily converted to electrical
energy by means of fuel cells. However,
direct storage of pressurized H2 is difficult
as it involves expensive, heavy and bulky
tanks as well as safety fittings, which
goes far beyond the requirements for
many portable applications. In low power
applications especially, diffusion losses
limit the direct storage of hydrogen.
Metal hydrides as lightweight, compact,
non-volatile, safe and reasonably priced
compounds overcome these issues. In
combination with water they can thus
serve as energy sources similar to conven-
tional or special batteries (e.g. Li-SOCl2)
but with a gravimetric and volumetric
energy density at least one order of
magnitude higher.
Applications
• backup / emergency power supplies
• standalone radiocommunication
• beacons
• sensors
• probes
PropertiesofLightweight
MetalHydrides
• NaH
- gravimetric H2 density of 8.4 %*)
- electric energy density 1259 Wh/kg*)
- very fast hydrolysis kinetics
• MgH2 - gravimetric H2 density 15.3 %
*)
- electric energy density 2295 Wh/kg*)
- slow hydrolysis kinetics
• LiH
- gravimetric H2 density 25.4 %*)
- electric energy density 3800 Wh/kg*)
- fast hydrolysis kinetics
*) under the assumption that H2O is
recuperated / available in excess
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F R AUNHO F E R I N S T I T U T E F O R MANU FA C T U R I N G T E C HNO LOGY
A ND A D VAN C E D MAT E R I A L S I FAM , B R AN CH L A B D R E S D E N
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Fig. 1 Time-dependent hydrogen generation for mixtures of commercially available MgH2 and activated MgH2 with various solid catalysts
1
4 Crystal structures and
proportions of different
metal hydrides
5 Outline of a hydrolysis reactor
in combination with a fuel cell
HydrolysisReactions
MeH + H2O H2 + MeOH
In hydrolysis reactions both the total
amount of released hydrogen and the
reaction kinetics strongly depend on a
number of factors:
- type of hydride
- active surface area
- pH
- presence of buffers
- salinity of water
- water temperature
Beyond that the reaction is catalyzed by the
addition of certain Lewis acids. Therefore,
an optimization of hydrolysis reactions
is feasible for a wide range of different
applications.
FraunhoferR&DServices
• Development of storage materials with
regard to specific requirements, e.g.
- suitable kinetics
- high energy density
- environment-related aspects
• Development of materials processing
technologies
• Specialized water treatment (e.g.
for sea water applications)
• Construction, test and evaluation of
metal hydride cartridges suitable for
hydrolysis
• Safety and reliability tests
• System development and testing
• System integration with fuel cells
• Software development
Metal Hydride Pellets
Water
Hydrolysis Reactor
Recuperation of Water
Exhaust (H2O)
Air (O2)
e−
H+
H2
Fuel Cell4 5
0 15 30 45 60
Time (min)
Hyd
roge
n co
nver
sion
(%)
75 90 105
Hydride mixture
MgH2 + Lewis acid III
MgH2 + Lewis acid II
MgH2 + Lewis acid I
MgH2 + Brønsted acid
MgH2
120
0
20
40
60
80
100
All measurements were perfor-med with de-ionized water at pH[t0] = 4.5; T[t0] = 20 °Cand a weight ratio of 1:100.
