1 hydrogen storage useful refs: see
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Hydrogen Storage Useful refs:See http://people.bath.ac.uk/cestjm/Shared/DTC/ch50182-Mays-Day2/
Energy White Paper
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Why Hydrogen for Energy?2H2 + O2 = 2H2O + Energy
Three Major Attractions(1) Clean combustion of a non-toxic fuel
(2) Delivered energy / mass is very high
(energy gain / electron best of all the chemical elements)
(3) Offers greatest potential for “Sustainable Energy Future”
FUEL CONTENTS OF POLLUTING MATTER IN FUMES (Kg/Kg of fuel)
Formula
CO2
SO2
NOx
Dust and Unburned
Matter
H2O
Pb(C2H5)4
C 1.893 0.012 0.008 0.1 0.633 0 CH4 2.75 0.03 0.0075 0 2.154 0
C8H17 3.09 0.010 0.0115 0.85 1.254 0.001 H2 0 0 0.016 0 7 0
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• Economic recyclable/rechargeable vessels
• Near ambient temperature pressure operation
• High hydrogen storage capacity/small volume
• Fast recharge and discharge kinetics
• Impact Safety
• Tolerant to trace poisoning
Hydrogen Storage Systems for Mobile Applications
• On a weight basis H2 has nearly three times the
energy content of gasoline. – 120 MJ/kg vs. 44 MJ/kg (LHV)
• On a volume basis the situation is reversed. – 3 MJ/L (5000 psi), 8 MJ/L (LH2) vs. 32 MJ/L
• Physical storage of hydrogen is bulky.• Capacity of reversible chemical storage at useful T, P is low.• Other challenging issues include energy efficiency, cost, and safety.
Storing enough hydrogen on vehicles to achieve greater than 300 miles driving range is difficult.
On-Board Hydrogen Storage Challenge
JoAnn Milliken, US DOE Status Report, 22 Oct 2002
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0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
100
20.4 K
87 kg m-3 [Silvera, Rev Mod Phys 52 (1980) 393]
critical point
solid
normal boiling point
real gasideal gas
real gas
de
nsi
ty / k
g m
-3
pressure / MPa
triple point
77 K
298 K
ideal gas
liqu
id d
ensi
ties
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
100
20.4 K
87 kg m-3 [Silvera, Rev Mod Phys 52 (1980) 393]
critical point
solid
normal boiling point
real gasideal gas
real gas
de
nsi
ty / k
g m
-3
pressure / MPa
triple point
77 K
298 K
ideal gas
liqu
id d
ensi
ties
0 10 20 30 40 50 60 70 80 90 1000
10
20
30
40
50
60
70
80
90
100
20.4 K
87 kg m-3 [Silvera, Rev Mod Phys 52 (1980) 393]
critical point
solid
normal boiling point
real gasideal gas
real gas
de
nsi
ty / k
g m
-3
pressure / MPa
triple point
77 K
298 K
ideal gas
liqu
id d
ensi
ties
Leachman’s EOS for Normal HydrogenLeachman, et al. J Phys Chem Ref Data 38 (2009) 721
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Cryogenic Storage of Hydrogen
Spherical designs best S/V
3% / day boil off (@ 20 K)
Insulation bulky
40% liquefaction penalty
High pressure options
Liq H2
Liq N2
Steel/Aluminium
Low emmittance multilayers
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Compression Storage of Hydrogen
Composite H2 Cylinder – 12 wt%
Conformable geometricsHigher wt% via increased pressureHeating on filling
H2 : 350 bar
Glass/Carbon fibreAluminium/Thermoplastic
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Advanced Materials for Hydrogen-Storage: 3 Strategic Challenges
I. Storage Capacity ≥ 6.5 wt%II. Reversibility of thermal absorption / desorption
cycles (at an accessible temperature)III. Low cost, low toxicity, low risk of explosion, etc.
(Source: www.doe.gov)
There is, as yet, no material known to meet simultaneously all of these requirements
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Volume of 4 kg of hydrogen compacted in different ways, with size relative to the size of a car.
Mg2NiH4 LaNi5H6 H2 (liquid) H2 (200 bar)
Schlapbach and Züttel, Nature, 15 Nov 2001
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Carbon
15Reversibly stored amount of hydrogen on various carbon materials versus the specific surface area of the samples.
Louis Schlapbach & Andreas Züttel, Nature 414, 15 Nov 2001
= nanotube samples (best-fit line indicated)
= other nanostructured carbon samples
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Magnesium-based Storage Materials
Problems associated with magnesium:
• Stability of the MgH2.
• Surface oxidation of magnesium based powders.
• Slow diffusion of hydrogen through MgH2.
Possible Solutions:
• Milling to develop a nanocrystalline material.
• Introduction of catalysts to dissociate hydrogen by co-milling or by developing multilayers.
• Alloying with other metals such as Ni, Al etc….
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Conclusions
Mobile
• Carbon Nanotubes - Less than 0.5 wt% uptake at RT. Adsorption related to surface area.- There may be a means of creating high hydrogen storage capacity CNT, but despite a large global effort, it remains elusive and lacking independent verification.
• Milled Magnesium + Alloys - Continuing to optimise milling conditions / PGM additions, in an effort to produce a practical on-board auto hydrogen store.- Operating Temperature still a problem
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• Low-cost storage material
• Able to scale up storage solution to large-scale?
• Relatively high hydrogen storage capacity
• Reasonably fast recharge and discharge kinetics
• Tolerant to trace poisoning
• Long-term cycling
Hydrogen Storage Systems for Stationary Applications
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zeolite A zeolites X and Y zeolite RHO.
The corners on each framework represent Si or Al and these are linked by oxygen bridges represented by the lines on the frameworks
Zeolite Framework Structures
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Zeolite A – Si-Al network.
Zeolite Preparation
• Hydrothermal Procedure
• Ion exchange using metal nitrate
• Characterisation•XRD
•SEM with EDX
•BET surface area (N2 at 77K)
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H2 uptake (wt.%)Material -196ºC RT 270ºCNaA 1.54 0.28 0.30CdA 1.14 0.25 0.30MgA 1.19 - -NaCsRHO 0.00 0.18 0.20CdRHO 0.08 0.19 0.25LiX 2.15 - -NaX 1.79 - 0.25CdX 1.42 - -MgX 1.61 - 0.28CuX - - 0.25NaY 1.81 - -CdY 1.47 - -MgY 1.74 - -
Hydrogen uptake in Zeolites
-196°C
-196°C
15bar H2
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Wt% Hydrogen plotted against BET surface area for activated carbon and zeolites samples.
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Conclusions
Stationary
Activated CarbonSignificant amounts of hydrogen can be stored reversibly (up to 4wt%) at 77 K and 15 bar.
Zeolites- Up to 2wt% at 77 K and 15 bar.- Hydrogen storage capacity of certain zeolites can be increased by manipulation of the zeolite exchangeable cations, e.g. Zeolite RHO
Unfortunately, at room temperature storage properties are below 1wt%, for both activated carbon and zeolites.
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THE STORAGE OF HYDROGEN IN SOLIDS
• Carbon: A deeper understanding of the unique interaction between H2 (H) and carbon;
– nature of physi-, vs chemi-sorption, in nanostructured carbon– the role of dangling bonds.
• Light Hydrides: A deeper understanding of the thermodynamics and kinetics of decomposition / absorption reactions and (intermediate) processes;
– metallicity, chemical reactivity and electronic states,– innovation in the synthesis and stabilisation (handling) of hydrides.
• Nanostructured Porous Solids: The tailoring of pore geometry, and (interior) chemical reactivity for hydrogen activation, storage and release;
– the interaction between H2 (H) and porous solids.