Hydrogen Storage via Sodium Borohydride Current Status, Barriers, and R&D Roadmap Ying Wu Presented at GCEP – Stanford University April 14-15, 2003 Millennium Cell Inc. One Industrial Way West, Eatontown, NJ 07724 OutlineOutline 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 2 ChoiceChoice ofof ChemicalChemical HydridesHydrides Comparison of Chemical Hydrides 20.0 %H by weight %H in stoich. mixture w/ water 15.0 10.0 wt% H Stored 5.0 0.0 LiBH4 LiH NaBH4 LiAlH4 AlH3 MgH2 NaAlH4 CaH2 NaH ) 2 0 -40 -80 -120 -160 kJ/mol H2 -200 Heat of Hydrolysis Rxn (kJ/Mole H 3 HydrogenHydrogen GenerationGeneration fromfrom SodiumSodium BorohydrideBorohydride (Hydrogen(Hydrogen onon Demand™Demand™ Process)Process) NaBH4 + 2 H2O à 4 H2 + NaBO2 (aq) + ~300 kJ cat An energy-dense Proprietary Pure humidified Borate can Exothermic water-based fuel catalyst induces H2 delivered to be recycled reaction (i.e., 30 wt% NaBH4 rapid H2 engine or into NaBH4 requires no holds 6.7 wt% H2) production fuel cell heat input 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) 4 GroupsGroups InvestigatingInvestigating BorohydrideBorohydride andand RelatedRelated SystemsSystems • 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 5 VolumetricVolumetric StorageStorage EfficiencyEfficiency Volume of SBH Fuel Solution Required To Store Varying Amounts of Hydrogen 120 Storage of 1 kg H2 Volumetric storage efficiency of 110 Storage of 3 kg H2 30 wt% fuel = ~63 g H2/L 100 Storage of 5 kg H2 For comparison: Storage of 7 kg H2 90 Storage of 9 kg H2 Liquid H = ~71 g H /L 80 2 2 70 5,000 psi compressed = ~23 g H2/L 60 50 10,000 psi compressed = ~39 g H /L 40 2 For a practical system, Volume of Solution (Gallons) 30 Balance of Plant is key 20 10 0 10% 15% 20% 25% 30% 35% 40% SBH concentration (wt%) 6 GravimetricGravimetric StorageStorage EfficiencyEfficiency ofof SBH,SBH, withwith BOPBOP Calculated Hydrogen Storage Efficiency, 90% Fuel Utilization 26 Max theoretical H2 stored (100% util) (wt%) 24 10% BOP (weight) Max theoretical 22 20% BOP (weight) 30% BOP (weight) 20 40% BOP (weight) 18 10% BOP wt 16 20% BOP wt 14 30% BOP wt 12 40% BOP wt (wt%) 10 8 6 gravimetric storage density 2 4 H 2 0 0 10 20 30 40 50 60 70 80 90 100 110 120 Stored SBH fuel concentration (wt%) SBH has intrinsically high storage density for H, which can yield 7 practical hydrogen generation systems with proper engineering PracticalPractical HydrogenHydrogen onon DemandDemandTMTM SchematicSchematic Water from Fuel Cell Gas/Liquid Fuel Hydrogen on DemandTM Separator Pump Catalyst Chamber Fuel tank: H2 NaBH4 solution H2 Discharged borate fuel area: NaBO2 NaBO2 H2O Hydrogen + Steam Coolant Loop Fuel Pure Humidified H2 Heat Cell Exchanger Oxygen from Air 8 HydrogenHydrogen onon DemandDemand™™ ApplicationsApplications PrototypePrototype BackupBackup PowerPower SystemSystem -- 1.21.2 kWkW hydrogenhydrogen generationgeneration systemsystem 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 9 CommercialCommercial VehicleVehicle DemonstrationsDemonstrations l Chrysler Town and Country Natrium® l Peugeot-Citroën H2O Vehicle l Fuel cell (Ballard Power Systems) l Fuel cell (Hpower) electric hybrid electric hybrid minivan vehicle, fire rescue vehicle concept car l Debut at EVAA – Dec 2001, on tour l Debut at Paris Auto Show – Oct 2002 most of 2002 l FC is ~5 kW range extender l FC is ~60 kW primary power plant l Estimated 300 mile range for system 10 VolumetricVolumetric EfficiencyEfficiency ofof HydrogenHydrogen StorageStorage andand GenerationGeneration IncreasedIncreased PackagingPackaging FlexibilityFlexibility SBH Fuel/Borate Tank Electric Drive Motor Hydrogen on Demand™ H2 Generator DC/DC Ballard Fuel Cell Engine Lithium Ion Converter Battery Pack Top View 3 cylinders @ 5000 psi 11 TransportationTransportation // Stationary:Stationary: ProjectedProjected TargetTarget GravimetricGravimetric ProjectionProjection (50(50--7575 kW,kW, 7.57.5 kgkg storedstored HH22 )) Projection: Gravimetric Storage Density 100 20.0 90 Stored Conc 18.0 80 System wt% 16.0 75 wt% SBH fuel 70 14.0 Need for FC water! 60 12.0 50 10.0 8.4 wt% H2 40 8.0 Next generation prototype + 50% FC Water 30 6.0 Pre-Natrium SBH Stored Concentration (wt%) 20 4.0 System H2 Storage Fraction (wt %) 10 2.0 Natrium 0 0.0 1999 2001 2003 2005 2007 2009 2011 Year 12 CurrentCurrent StatusStatus ofof HH22 StorageStorage TechnologiesTechnologies Current Current Hydrogen Storage Volumetric Gravimetric + of Storage – of Storage Technology Storage Density Storage Density Technology Technology (g H2/L) (wt %) 5000 psi ~12.5 g H2/L ~ 2.7 wt% Known Technology H2 under (350 bar)* = 1.5 MJ/L pressure, g H2/L, Infrastructure, H2 not humidified 10000 psi ~24.2 g H2/L ~ 3.3 wt% Known Technology H2 under (700 bar)* = 2.9 MJ/L pressure, g H2/L, Infrastructure, H2 not humidified Liquid* ~37.0 g H2/L ~ 5.0 wt% Known Technology Boil Off, = 4.4 MJ/L Infrastructure Solid Metal Hydrides ? ? ? Hydrogen on ~> 22 g H2/L > 4.0 wt% H2 is not under Regeneration, Demand™ NaBH 4 = > 2.5 MJ/L pressure, system Fuel Handling Chemical Hydride design, Strategy Infrastructure *Taken from: GM Website, specifications of Hywire and HydroGen3 Vehicles: http://media.gm.com/about_gm/vehicle_tech/fuel_cell/monaco/hydrogen/index.htm http://media.gm.com/about_gm/vehicle_tech/fuel_cell/hywire/index.html 13 HydrogenHydrogen StorageStorage TargetsTargets HOD (NaBH4) Current SysWt% >4.0 Advanced HOD (NaBH4) SysWt% 6.2-8.4 Taken from: Brenstoffzellen - Fahrzeuge von GM/Opel – Technik und Markteinfuehrung, Dr. G. Arnold, Jan 22-23, 2003 14 IncreaseIncrease thethe GravimetricGravimetric andand VolumetricVolumetric EnergyEnergy DensityDensity l Two main approaches: Directly increasing the fuel concentration: Physical characteristics issues Chemistry issues (e.g., max concentration in catalyst bed) Improving system design: Recycle H2-stream condensate Recycle fuel cell water Higher 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 Þ A number of these issues are already being addressed at MCEL 15 FuelFuel CostCost ReductionReduction 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 Applications l 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. 16 CanCan BB22HH66 bebe betterbetter thanthan NaHNaH asas anan IntermediateIntermediate ?? Existing Process Proposed Process 1666 kJ/mol NaBH4 Na NaH (B(OCH3)3) 3310 kJ/mol NaBH4 365 kJ/mol (accounting for cell Energy NaBH efficiency) 4 49 kJ/mol B H 2 6 ? (Na2CO3 ) NaBH4 B(OR)3 NaCl NaBO2 Reaction Steps • Production of Na is < 50% energy efficient • Utilize alternative intermediate B2H6. • Further energy losses to convert Na to NaBH4 • Need appropriate energy input to efficiently produce B2H6. 17 WeWe areare currentlycurrently investigatinginvestigating bothboth electrochemicalelectrochemical andand chemicalchemical pathwayspathways Electrochemical Pathway Thermochemical Pathway l More efficient electrochemical l Conversion of B(OR)3 to B2H6 synthesis of Na l Studied BCl3 to B2H6 as a model reaction l Direct electrochemical conversion of system borate to borohydride l Reaction yield is key. l Molten salts and/or ionic liquids as reaction medium Anode Inert Gas Cathode and Inlet and Outlet Hydrogen Gas Process Schematic Sparger Thermocouple ROH Glass Jar NaBO2 A B(OR)3 B B2H6 H2 Melt Na2CO3 C NaBH4 CO2 Heating Mantle 18 InfrastructureInfrastructure -- TransportationTransportation Fueling/RecyclingFueling/Recycling StrategyStrategy l Supply and Demand Current production process is geared towards specialty chemical applications of sodium borohydride, and is expensive and inefficient.