Hydrogen Storage via Sodium BorohydrideCurrent Status, Barriers, and R&D Roadmap
Ying Wu
Presented atGCEP – Stanford University
April 14-15, 2003
Millennium Cell Inc.One Industrial Way West, Eatontown, NJ 07724
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l Introduction: hydrogen storage via sodium borohydride
l Current Status: portable and vehicular applications
l Barriers to commercialization
l Research issues and on-going efforts
l Summary
l Introduction: hydrogen storage via sodium borohydride
l Current Status: portable and vehicular applications
l Barriers to commercialization
l Research issues and on-going efforts
l Summary
OutlineOutline
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- 2 0 0
- 1 6 0
- 1 2 0
- 8 0
- 4 0
0
Hea
t of
Hyd
roly
sis
Rxn
(kJ
/Mol
e H
2)
k J / m o l H 2
Compar ison o f Chemica l Hydr ides
0.0
5.0
10.0
15.0
20.0
L iBH4 L iH N a B H 4 L iA lH4 A lH3 M g H 2 NaA lH4 C a H 2 N a H
wt%
H S
tore
d
% H b y w e i g h t
%H in s to ich . m ix tu re w / wa te r
Choice of Chemical HydridesChoice of Chemical Hydrides
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An energy-dense water-based fuel
(i.e., 30 wt% NaBH4holds 6.7 wt% H2)
Borate can be recycled into NaBH4
Proprietary catalyst induces
rapid H2production
NaBH4 + 2 H2O à 4 H2 + NaBO2 (aq) + ~300 kJ
Pure humidified H2 delivered to
engine or fuel cell
Exothermic reaction
requires no heat input
cat
Hydrogen Generation from Sodium Borohydride(Hydrogen on Demand™ Process)Hydrogen Generation from Sodium Borohydride(Hydrogen on Demand™ Process)
Hydrogen is generated in a controllable, heat-releasing reaction
Fuel is a room-temperature, non-flammable liquid under no pressure
No side reactions or volatile by-products.
Generated H2 is high purity (no CO, S) and humidified (heat generates some water vapour)
Hydrogen is generated in a controllable, heat-releasing reaction
Fuel is a room-temperature, non-flammable liquid under no pressure
No side reactions or volatile by-products.
Generated H2 is high purity (no CO, S) and humidified (heat generates some water vapour)
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Groups Investigating Borohydride and Related SystemsGroups Investigating Borohydride and Related Systems
• Millennium Cell – Hydrogen on DemandTM Systems and SBH Synthesis; Partners: U. S. Borax, Air Products and Chemicals
• Manhattan Scientifics/R.G. Hockaday – Portable SBH systems
• Hydrogenics – System integrator, HyPORTTM power generator using SBH as source of H2
• Prof. S. Suda (MERIT/KUCEL) – Hydrogen generation method, and SBH synthesis from MgH2.
• Toyota Motor Company – Japanese patents on H2 generation from SBH, methods for SBH synthesis.
• Dr. Peter Kong, INEEL – Nuclear energy assisted synthesis of SBH, recently acquired funding
• Prof. M. A. Matthews , Univ. South Carolina – SBH hydrogen generation systems (steam hydrolysis)
• Prof. A. Zuttel, Univ Fribourg, Switzerland – LiBH4, thermo-decomposition
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Volumetric storage efficiency of 30 wt% fuel = ~63 g H2/L
For comparison:
Liquid H2 = ~71 g H2/L
5,000 psi compressed =~23 g H2/L
10,000 psi compressed =~39 g H2/L
For a practical system, Balance of Plant is key
Volumetric storage efficiency of 30 wt% fuel = ~63 g H2/L
For comparison:
Liquid H2 = ~71 g H2/L
5,000 psi compressed =~23 g H2/L
10,000 psi compressed =~39 g H2/L
For a practical system, Balance of Plant is key
Volumetric Storage EfficiencyVolumetric Storage Efficiency
Volume of SBH Fuel Solution Required To Store Varying Amounts of Hydrogen
0
10
20
30
40
50
60
70
80
90
100
110
120
10% 15% 20% 25% 30% 35% 40%
SBH concentration (wt%)
Vo
lum
e o
f So
luti
on
(Gal
lon
s)
Storage of 1 kg H2Storage of 3 kg H2
Storage of 5 kg H2
Storage of 7 kg H2Storage of 9 kg H2
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Gravimetric Storage Efficiency of SBH, with BOPGravimetric Storage Efficiency of SBH, with BOP
Calculated Hydrogen Storage Efficiency, 90% Fuel Utilization
0
2
4
6
8
10
12
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0 10 20 30 40 50 60 70 80 90 100 110 120Stored SBH fuel concentration (wt%)
H2
gra
vim
etri
c st
ora
ge
den
sity
(w
t%)
Max theoretical H2 stored (100% util) (wt%)
10% BOP (weight)
20% BOP (weight)
30% BOP (weight)
40% BOP (weight)
40% BOP wt
Max theoretical
30% BOP wt
20% BOP wt
10% BOP wt
SBH has intrinsically high storage density for H, which can yield practical hydrogen generation systems with proper engineering
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Practical Hydrogen on DemandTM SchematicPractical Hydrogen on DemandTM Schematic
Fuel tank: NaBH4solution
Discharged fuel area: NaBO2
Fuel Pump
Hydrogen on DemandTM
Catalyst Chamber H2
borate
Gas/Liquid Separator
Hydrogen + Steam
Coolant Loop
Heat Exchanger
Fuel Cell
Pure Humidified H2
Oxygen from Air
Water from Fuel Cell
NaBO2
H2O
H2
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l Systems typically run at < 40 psig system pressure, rated at 18 SLM hydrogen, capable of max flows of up to ~45 SLM (~3 kWe)
l One-button operation – works as a “black box” hydrogen source that looks like a low pressure hydrogen cylinder
Hydrogen on Demand™ ApplicationsPrototype Backup Power System - 1.2 kW hydrogen generation system
Hydrogen on Demand™ ApplicationsPrototype Backup Power System - 1.2 kW hydrogen generation system
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l Chrysler Town and Country Natrium®
l Fuel cell (Ballard Power Systems) electric hybrid minivan
l Debut at EVAA – Dec 2001, on tour most of 2002
l FC is ~60 kW primary power plant
l Estimated 300 mile range for system
l Chrysler Town and Country Natrium®
l Fuel cell (Ballard Power Systems) electric hybrid minivan
l Debut at EVAA – Dec 2001, on tour most of 2002
l FC is ~60 kW primary power plant
l Estimated 300 mile range for system
Commercial Vehicle DemonstrationsCommercial Vehicle Demonstrations
l Peugeot-Citroën H2O Vehicle
l Fuel cell (Hpower) electric hybrid vehicle, fire rescue vehicle concept car
l Debut at Paris Auto Show – Oct 2002
l FC is ~5 kW range extender
l Peugeot-Citroën H2O Vehicle
l Fuel cell (Hpower) electric hybrid vehicle, fire rescue vehicle concept car
l Debut at Paris Auto Show – Oct 2002
l FC is ~5 kW range extender
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Top View
Volumetric Efficiency of Hydrogen Storage and GenerationIncreased Packaging FlexibilityVolumetric Efficiency of Hydrogen Storage and GenerationIncreased Packaging Flexibility
3 cylinders @ 5000 psi
SBH Fuel/Borate Tank
Hydrogen on Demand™ H2 Generator
Ballard Fuel Cell Engine
DC/DC ConverterLithium Ion
Battery Pack
Electric Drive Motor
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Transportation / Stationary: Projected TargetGravimetric Projection (50-75 kW, 7.5 kg stored H2 )Transportation / Stationary: Projected TargetGravimetric Projection (50-75 kW, 7.5 kg stored H2 )
Projection: Gravimetric Storage Density
0
10
20
30
40
50
60
70
80
90
100
1999 2001 2003 2005 2007 2009 2011
Year
SB
H S
tore
d C
once
ntra
tion
(wt%
)
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
Sys
tem
H2
Sto
rage
Fra
ctio
n (w
t %)
Stored Conc
System wt%
Need for FC water!
Pre-Natrium
Natrium
+ 50% FC Water
8.4 wt% H2
75 wt% SBH fuel
Next generation prototype
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???Solid Metal Hydrides
Regeneration, Fuel Handling Strategy
H2 is not under pressure, system design, Infrastructure
> 4.0 wt%~> 22 g H2/L= > 2.5 MJ/L
Hydrogen on Demand™ NaBH4Chemical Hydride
Boil Off, Infrastructure
Known Technology~ 5.0 wt%~37.0 g H2/L= 4.4 MJ/L
Liquid*
H2 under pressure, g H2/L, Infrastructure, H2not humidified
Known Technology~ 3.3 wt%~24.2 g H2/L= 2.9 MJ/L
10000 psi(700 bar)*
H2 under pressure, g H2/L, Infrastructure, H2 not humidified
Known Technology~ 2.7 wt%~12.5 g H2/L= 1.5 MJ/L
5000 psi(350 bar)*
– of Storage Technology
+ of Storage Technology
Current Gravimetric
Storage Density (wt %)
Current Volumetric
Storage Density (g H2/L)
Hydrogen Storage Technology
*Taken from: GM Website, specifications of Hywire and HydroGen3 Vehicles: http://media.gm.com/about_gm/vehicle_tech/fuel_cell/monaco/hydrogen/index.htmhttp://media.gm.com/about_gm/vehicle_tech/fuel_cell/hywire/index.html
Current Status of H2 Storage TechnologiesCurrent Status of H2 Storage Technologies
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Hydrogen Storage TargetsHydrogen Storage Targets
Taken from: Brenstoffzellen - Fahrzeuge von GM/Opel –Technik und Markteinfuehrung, Dr. G. Arnold, Jan 22-23, 2003
HOD (NaBH4) Current SysWt% >4.0
Advanced HOD (NaBH4) SysWt% 6.2-8.4
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l Two main approaches:Directly increasing the fuel concentration:
Physical characteristics issuesChemistry issues (e.g., max concentration in catalyst bed)
Improving system design:Recycle H2-stream condensateRecycle fuel cell waterHigher concentration è higher volumetric and gravimetric H2 storage
l Fuel properties and fuel chemistry are important across a range of high concentration fuels
Physical properties
Stability, solubility, viscosity
Freezing points
⇒ A number of these issues are already being addressed at MCEL
Increase the Gravimetric and Volumetric Energy DensityIncrease the Gravimetric and Volumetric Energy Density
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Fuel Cost ReductionFuel Cost Reduction
Why is NaBH4 costly to produce?l Need 4 electrons, stored in 4 B-H bonds, used to reduce H2O and form H2
l Need to combine 3 different elements + electrons + energy
Na + B + H + electrons + energy (substantial entropic and enthalpic barriers)
l The complexity of the system leads to a stepwise process for SBH production.
l The NaBH4 price will always be driven by the price of primary energy
l Energy efficiency is key; any process has to be optimized to minimize wasted energy.
Particular Challenge for Transportation Applicationsl Convert a multi-component, high energy, high purity specialty chemical into an
everyday commodity fuel l Difficult to compete with the current cost of gasoline, but could compare
favorably with other hydrogen storage technologies.
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Can B2H6 be better than NaH as an Intermediate ?Can B2H6 be better than NaH as an Intermediate ?
N a B H4
NaH(B(OCH3)3)
N a
NaC l
B 2H 6
(Na2C O3 )
B(OR)3
En
erg
y
Existing Process Proposed Process
Reaction Steps
NaBO 2
3310 kJ /mol NaBH4(accounting for cell
efficiency)
365 kJ/mol N a B H 4
?49 kJ/mol
1666 kJ/mol NaBH4
N a B H4
NaH(B(OCH3)3)
N a
NaC l
B 2H 6
(Na2C O3 )
B(OR)3
En
erg
yE
ner
gy
Existing ProcessExisting Process Proposed ProcessProposed Process
Reaction Steps
NaBO 2
3310 kJ /mol NaBH4(accounting for cell
efficiency)
365 kJ/mol N a B H 4
?49 kJ/mol
1666 kJ/mol NaBH4
• Production of Na is < 50% energy efficient• Further energy losses to convert Na to NaBH4
• Utilize alternative intermediate B2H6.• Need appropriate energy input to
efficiently produce B2H6.
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We are currently investigating both electrochemical and chemical pathwaysWe are currently investigating both electrochemical and chemical pathways
Electrochemical Pathwayl More efficient electrochemical
synthesis of Nal Direct electrochemical conversion of
borate to borohydridel Molten salts and/or ionic liquids as
reaction medium
Thermochemical Pathwayl Conversion of B(OR)3 to B2H6
l Studied BCl3 to B2H6 as a model reaction system
l Reaction yield is key.
Process Schematic
NaBO2 B2H6
NaBH4CNa2CO3
B(OR)3A B
CO2
ROH
H2
H e a t i n g M a n t l e
A n o d e
C a t h o d e a n dH y d r o g e n G a s
S p a r g e r
I n e r t G a sI n l e t a n d O u t l e t
T h e r m o c o u p l e
G l a s s J a r
M e l t
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Infrastructure - Transportation Fueling/Recycling StrategyInfrastructure - Transportation Fueling/Recycling Strategy
l Supply and Demand
Current production process is geared towards specialty chemical applications of sodium borohydride, and is expensive and inefficient.
Markets such as backup power are less sensitive to fuel price; incremental process improvements can go a long way
l Infrastructure envisioned, such that borates will be recycled into borohydride at centralized facilities
l Chemistry research is targeting an improved synthesis and regeneration process that will allow SBH to become a commodity chemical. This is necessary in order to access markets such as transportation.
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l SBH has high intrinsic gravimetric and volumetric hydrogen storage density, which can yield practical hydrogen generation systems with proper engineering.
l Hydrogen on Demand™ technology has been successfully demonstrated over a wide range of hydrogen delivery flow rates and pressures.
l Studies are being carried out to integrate thermal and water management between the SBH fuel sub-system and the FC sub-system
l Progress is being made to improve current SBH synthesis technology aimed at reducing manufacturing cost.
l The path is defined, but there is certainly more work ahead of us !Continued improvements in regeneration technologySystems design and engineering to access higher energy densities
SummarySummary
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Research OpportunitiesResearch Opportunities
• Hydrogen Delivery System
• Intelligent controls for the fuel system.
• Increase gravimetric and volumetric storage density
• Advanced catalyst development and novel catalyst bed development
• Solve the SBH cost reduction and recycling issue • Basic research in boron chemistry
• Chemical engineering and chemical process development
• Develop fueling infrastructure
• Integrate renewable energy sources and/or non carbon-based energy sources
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Thank YouThank You
Questions, comments, and further discussions,
Please contact [email protected]