Title: ORNL H2 Storage Workshop
1An Overview of Chemical HydridesORNL Hydrogen
Storage WorkshopMay 7-8, 2003
- Brian D. James
- Directed Technologies Inc.
- 3601 Wilson Blvd., Suite 650
- Arlington, VA 22201
- (703) 243-3383
- Brian_James_at_DirectedTechnologies.com
2Presentation Outline
- Overview
- Technical Targets for FCVs
- Challenges
- Science Chemistry
- What are Chemical Hydrides?
- Some Examples
- Conclusions
3Short List of Desirable Attributes
- Weight High System H2 Mass Fraction (10)
- Volume High Volumetric Density
- Cost Low Cost H2 (1.50/kg)
- Low Operating Temperature
- Pure H2 evolution (no diluents/FC poisons)
- Safe Storage/Handling/Non-Pyrophoric
- Liquid (for ease of metering handling)
- Complete, vigorous reaction (but not explosive)
- Easily handled waste products
4Hydrogen Production Pathways
Fuel Cell
Pure H2 (including water vapor)
Reformate (H2 Diluent Gases)
Carbon Storage
Chemical Hydrides
Metal Hydrides
Compr. Gas
ATR
POX/ CPOX
SMR
Thermal Decomposition
(Ammonia)
Hydrocarbon (Diesel,gasoline,propane, methanol,
ethanol)
Thermal Decomposition
Water Reaction
5What defines a Chemical Hydride?
- For our purposes, a chemical hydride is any
compound which reacts with water to evolve
hydrogen - A few examples
- Millenium Cell Sodium Borohydride
- Powerball
- Iron Reduction
- Aluminum Reduction
- But there are actually many possibilities
6Chemical Hydride Options
7Chemical Hydride Options, continued
8Chemical Hydride Options, continued
9Chemical Hydride Options, continued
10Millennium Cells Sodium Borohydride
The Hydrogen On Demand System
- NaBH4 fuel is a room temperature, 1 atm liquid
- Waste product is a warm solution
- Resulting H2 is pure and at 100 relative
humidity
On-board Reaction
NaBH4 2 H2O ? NaBO2
4 H2 300kJ
30 NaBH4 solution water, stabilized with 1-3
NaOH
Proprietary catalyst achieves instantaneous
hydrogen production
Borax waste product stays dissolved in water
Pure humidified H2 delivered to Fuel Cell
Exothermic Reaction Energy
11Millennium Cells Sodium Borohydride
On-board Components
H2 Gas
Hydrogen On Demand Catalyst System
Borohydride in Water
Pump
Borax In Water
Heat Rejection
Off-board Borax Regeneration
Chrysler Natrium Fuel Cell Vehicle, 2001, 300
mile range
12Millennium Cell Key Elements- OnBoard (From
Patent No. 6,534,033)
- pH7, typically pH 12
- 5-30 w.w. water solution of sodium borohydride
(but also considering lithium borohydride,
potassium borohydride, ammonium borohydride,
tetramethyl ammonium borohydride, and mixtures
thereof) - Stabilizing agent typically 1-3 sodium
hydroxide (but also considering lithium
hydroxide, potassium hydroxide, sodium sulfide,
thiourea, carbon disulfide, sodium zincate,
sodium gallate, and mixtures thereof) - Transition metal catalyst typically Ru/Ni (but
also considering iron, cobalt, copper, manganese,
rhodium, rhenium, platinum, palladium, chromium,
silver, osmium, iridium, borides thereof alloys
thereof, and mixtures thereof)
13Millennium Cell Key Elements- OffBoard (From
Patent No. 6,524,542 )
3 NaBO2 6 C 6 H2O ? 3 NaBH4 6 CO2
Net Reaction
4NaBO2 4CO2 2H2O ? 4NaHC 2B2O3 -126
BTU (-133 kJ) 4NaHCO3 ? 2Na2O 4CO2 2H2O
2254 BTU (2378 kJ) 12HBr ? 6H2
6Br2 2476 BTU (2612 kJ) 2B2O3 6C
6Br2 ? 4BBr3 6CO 2285 BTU (2411
kJ) 6CO 6H2O ? 6H2 6CO2
-571 BTU (-602 kJ) 4BBr3
12H2 ? 2B2H6 12HBr 1746 BTU
(1842 kJ) 2Na2O 2B2H6 ? 3NaBH4
NaBO2 -2730 BTU (-2880 kJ)
3NaBO2 6C 6H2O ? 3NaBH4 6CO2
8761 BTU (9243 kJ)
Millennium Cell claims 53-65 recycle
efficiency (H2 LHV/energy input)
14Millennium Cells Sodium Borohydride
Advantages
Problems
- On-board
- Needs wt/vol optimization
- Requires exotherm management
- Requires waste
- management/flushing
- Off-board
- Have not demonstrated economical
- recycling method
- H2 cost is not competitive
- Liquid storage is safe, low pressure
- Relatively long shelf life (yr half-life)
- Potentially compact system
- Waste product is harmless
All engineering issues, not science problems
Fundamental chemistry issues to resolve/demo
Development Level
On-board moderately well-developed Off-Board
Poor/Fair Most Developed of all chemical hydride
systems
15Power Balls Sodium Hydride
- Dry NaH powder in plastic balls
- Pneumatic splitter opens balls and drops into
liquid water - Maintains 120-150 psi H2 in tank
On-board Reaction NaH (solid) H2O (liquid)
-- NaOH (liquid) H2 (gas) Off-board Recycle
2NaOH CH4 O2 ? 2NaH CO2 2H2O
Catalyst
Temperature 350C demonstrated, potentially
100-200C
Based on 1999 Energetics Report (DiPietro)
16Power Balls Sodium Hydride
Problems
Advantages
- Moderately Heavy System
- Unproven(?) recycling feasibility
- and economics
- High H2 cost
- Exothermic reaction requires heat
- removal
- Compact system
- Onboard system low cost
- Particularly good in early days of FCV
- introduction when FCV are geographically
- dispersed
Development Level
- References
- www.PowerBall.net
- US Patent 5,817,157
- US Patent 5,728,464
On-board moderate/well Off-Board Poor/Fair
17Iron Oxidation
- Proposed by H-Power in early 1990s
- Recent experiments by Kiyoshi Otsuka of the Tokyo
Institute of Technology
Onboard Reaction 3Fe 4 H2O -- Fe3O4
4H2 Offboard Recycle 4(H2 or CO) Fe3O4 -- 3
Fe 4 (H2O or CO2)
Catalyst aluminum, gallium, chromium or
molybdenum catalyst on magnetite
Temperature 350C demonstrated, potentially
100-200C
Based on H-Power calculations.
18Iron Oxidation
Problems
(Potential) Advantages
- Inherently heavy system (fatal)
- Only feasible if FC waste heat is
- sufficient for reaction
- Awkward (at best) refueling
- Iron is cheap
- 0.50-1.00/kg H2 (based on H-Power
- estimates)
Development Level
On-board Poor/Low Off-Board Poor/Low
19Aluminum
- Proposed by Global Hydrofuels based on work of
Asok Chaklader (Univ. of BC) - Mechanical mixture of Al metal and
Al-oxide(s)/Hydroxide(s) - Oxides suppress Al passivation and allow 40-70
reaction in 4
On-board Reaction 2Al 6 H2O -- 2Al(OH)3
3H2 Off-board Recycle similar to Hall Process
(conv. Electrolytic Al ore process)
- Pelletized Reactants
- Al metal (99 pure, 80 micron particle size)
- Calcined boehmite (AlOOH)
- 50/50 Al/boehmite wt fraction
- Water must be carried
- 10C to 90C Operating Temperature
- 28 expected Energy Efficiency
- (13.2 KWh/kg Al reprocessing electricity
required) - 6/kg _at_ 0.05/kWh
20Aluminum
Problems
Advantages
- Inherently heavy system
- Low Recycle Energy Efficiency
- High H2 cost
- Water must be carried
- Awkward (at best) refueling
- Reactants Products non-hazardous
- Near neutral pH
- References
- www.globalhydrofuel.com
- www.hydrogenvcc.com
- US Patent 6,440,385
- (August 2002 Hydrogen generation
- from water split reaction)
Development Level
On-board Low/Lab only Off-Board Low but similar
to commercial process
21Conclusions
- Considerable Chemical Hydride activity in last
5 years - Some Ventures have led to mechanically
successful - in-vehicle demos
- But Commercialization has not yet been prove
- Need both On-Board System
commercialization - AND
- Off-Board Recycling commercialization
- Must compete against the leading contender for
onboard - storage
- Compressed H2 (at 5-10 kpsi)
- 5-8 H2 by weight
- early/small stations)