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

14

16

18

20

22

24

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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 wu@millenniumcell.com