NaBH4/H2O2(Air) Fuel Cell Technology Technical Presentation

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NaBH4/H2O2(Air) Fuel Cell TechnologyTechnical
Presentation
CONTACT Richard Dell at 919.870.9494
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NaBH4/H2O2 Fuel Cells

• UIUC/NPL have developed a novel all liquid fuel
  cell with sodium borohydride (NaBH4) as the fuel
  and hydrogen peroxide (H2O2) or air as the
  oxidizer
• This borohydride fuel cell design has been
  thoroughly tested and optimized to ensure rapid
  commercialization

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Reactions

• Anode Reaction
• NaBH4 2H2O ? NaBO2 8H 8e- (-0.45 V)
• Cathode Reaction
• H2O2 2e- ? 2OH- (1.78 V)
• or, O2 2H 2e- ? 2OH- (1.78 V)
• Overall Reaction
• NaBH4 2H2O 4H2O2 ? NaBO2 8H2O (2.23 V)

The only waste products are water and sodium
metaborate, which can be recycled to produce new
sodium borohydride either at a central plant
(currently feasible) or in the fuel cell itself
(currently in development).
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NPLs Cell Achieves Leading Power Densities
Theoretical Power Density Current State of the Art Power Density
UIUC/NPLs NaBH4/H2O2 Cell 2580 W-hr/kg 1000 W-hr/kg
An optimized version of our small test cell
generated 36-W at 60ºC, representing one of the
highest power density reported to date for a
small fuel cell working at sub-100?C.
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NaBH4/H2O2 Fuel Cells

• Other distinct advantages of sodium
  borohydride/hydrogen peroxide (NaBH4/H2O2) fuel
  cells
• The fuel is environmentally safe and non
  flammable.
• The liquid fuel minimizes cooling issues, in
  comparison to H2/O2 systems
• The theoretical potential of NaBH4/H2O2 fuel
  cells is 2.23 V, compared to 1.23 V for H2/O2
  fuel cells, so fewer cells are needed to
  construct a stack of reasonable voltage.

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A 500-W NaBH4/H2O2 Stack Shows That Our Record
Power Densities are Scalable.

• The completed 500-W stack
• The active area per cell was 144 cm2 and 15 cells
  were employed to provide a total stack active
  area of 2160 cm2.

• The deconstructed 10-W test cell
• Flow rate of approximately 200 cm3/min
• Minimal pressure drop even with parallel flow due
  to low flow rate
• Temperature rise of approximately 15C
• Cell runs at 50 efficiency at highest rated load

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UIUC/NPL NaBH4/H2O2 FCs Demonstrate Excellent
Performance
The V-I characteristics of various fuel cells, at
room temperature, ambient pressure operation.
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NaBH4/H2O2 Storage Safer and More Efficient Than
Hydrogen Storage

• NaBH4/H2O2 much less volatile than H2/O2 or
  gasoline.
• No need for heavy structural tanks to store
  pressurized gasses.
• No need to cryogenically store the liquid fuels.
• NaBH4/H2O2 much less toxic to humans than
  gasoline

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Direct NaBH4 Fuel Cells Can Also Use Oxygen From
Air as an Oxidizer

• Using oxygen (air) as the oxidizer decreases fuel
  weight, since H2O2 would not need to be carried
• The slight loss in power density is more than
  made up for by the mass of oxidizer that does not
  need to be carried
• This approach can work for terrestrial
  applications where size/weight is at a premium

Automobiles, manned and unmanned aircraft, ships,
and auxiliary power units are all ideally suited
to an NaBH4/air fuel cell
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Progress in NaBH4 Production and Recycling Will
Lower Costs

• NaBH4 currently costs 50-60 per kg, yielding an
  TOTAL energy cost of 0.66 per kW-hr
• Much of the cost of NaBH4 is in electrolyzing Na
  from NaCl
• Millennium Cell (Eatontown, NJ) is working on a
  process to reduce the cost of NaBH4 by extracting
  Na from the NaOH that is produced during NaBH4
  production and recycling the NaBO2 product of the
  fuel cell
• NPL is working on an electrolytic process
• Under laboratory conditions, NaBH4 has been
  produced for 0.07 per kilogram, which in a
  NaBH4/H2O2 fuel cell, would yield an energy cost
  under 0.3 per kW-hr, comparable to the cost of
  gasoline

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500-W Stack Demonstrates Scale Up to Higher
Power Output
 
V-I and P-I performance of the 500-W NaBH4/H2O2
FC.
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In Addition to Our Current Regenerative Cell Long
Term Approaches Are Under Study

1. Novel chemistries can be used to create a timed
   release fuel cell. This design, termed the STID
   design, is in testing now and has shown great
   promise for satellite and load leveling
   applications.
2. The fuel cell waste product, NaBO2, can be
   drained from the fuel cell and chemically
   recycled at a dedicated recycling station. This
   approach is best suited for automotive and some
   stationary applications.
3. NaBO2 can be converted in situ in a unitized
   regenerative cell. Some progress has been made
   on this design and work is continuing.

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STID Unitized Regenerative Cell

• The STID design uses novel catalysts and a new
  chemical pathway to achieve regeneration
• Currently, the only unitized hydrogen based
  liquid regenerative cell in development.
• Roundtrip efficiencies of 75 with cycle life of
  gt10000 have been demonstrated.
• A complete NaBH4 regenerative fuel cell system
  would mitigate the need to consider borohydride
  fuel economics

Current state-of-the-art 16-W regenerative test
cell.
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STID Performance Characteristics
Energy Density Power Density (Peak) Power Density (Nominal) Cycle Life
Prototype 110 W-hr/kg 400 W/kg 110 W/kg gt10000
In 5 Months 200 W-hr/kg 800 W/kg 220 W/kg gt10000

• Because the cell uses a permeable membrane, it
  will self discharge after a certain amount of
  time (15 hrs)
• Because of this discharge/recharge cycle, the
  cell is ideal for periodic applications such as
  satellite power and load leveling

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1-kW UPS System

• Compact design providing 1 hr runtime.
• Easily expandable with auxiliary tanks for
  extended operation.
• Meets or exceeds typical commercial UPS system
  requirements.
• 3.5x more space efficient than typical battery
  UPS

Schematic of proposed UPS system.
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1-kW UPS System Startup
System Startup Fast fuel cell start-up time
minimizes battery size to 5.9 W-hr.

• Cell power and required battery power during
  system startup are sized to maintain a system
  output of 1000 W
• 20 second fuel cell startup time
• The battery kicks in after power failure to
  provide immediate power until the fuel cell can
  reach full power
• Modest battery requirements for startup due to
  fast fuel cell startup
• Power 1250 W
• Energy 5.9 W-hr

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20-W Laptop Power Unit

• NaBH4/H202 Micro Cell
• 20 W
• 500 W-hr
• 2.2 lbs

• In comparison Micro Direct Methanol Fuel Cell
• 20 W
• 500 W-hr
• 3.5 7 lbs

Schematic of proposed laptop power unit.
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Space Applications

• Astronauts have been using fuel cells for power
  on spacecraft since the 1960s.
• Looking forward, one of the most challenging
  issues in space applications is increasing the
  energy density of fuel cells.
• NaBH4/H2O2 fuel cells achieve that desired
  increase in energy density.
• Low storage mass overhead of NaBH4/H2O2 fuel
  cells very important for cost savings in space
  launches.
• First application planned is for an AF satellite.

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Regenerative Designs Allow Solar Energy Storage

• The periodic recharge/discharge cycle of the STID
  design makes it ideal for low earth orbit
  applications
• Regenerative cells provide for solar energy
  storage
• This design can also be used for lunar/Martian
  rover designs, with the recharge cycle tuned to
  the availability of solar energy

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Direct NaBH4/Air Fuel Cells for Automobiles
Approach DOE 2015 Targets

• Power density of 2200 W/L
• Specific power of 2000 W/kg
• 75 fuel cell efficiency
• System cost 20/kWe
• Durability, transient response time, cold startup
  time, and temperature survivability conditions
  can currently all be met, unlike gaseous H2
  systems.

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Direct NaBH4/Air Fuel Cells Can Be Used For Many
Other Types of Mobile Uses

• Any vehicle that currently supplies electrical
  demand through batteries can be fitted with an
  all liquid fuel cell for better power and energy
  densities

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Liquid Fuel Cells are Ideal for Man Portable
Operations

• Small liquid fuel cells can provide greater power
  densities than batteries
• This equals less weight necessary for power
  equipment
• The fuel cell can be easily scaled to the power
  needs of the mission

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Regenerative Fuel Cells For Load Leveling
Applications

• The STID regenerative design can be scaled to
  provide load leveling for utilities
• The power density and cost compare favorably with
  other flow battery designs
• The periodic discharge recharge cycle makes the
  STID design ideal for this application.

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Regenerative Fuel Cells for Renewable Energy
Storage

• The STID design can store energy when wind and
  solar energy are plentiful and ensure a
  continuous supply of electricity when these
  sources are not in operation.
• The STID design allows for easier storage than
  electrolytic hydrogen production

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In Summary, NaBH4 FCs Are Proceeding Rapidly To
Commercialization

• The NaBH4/H2O2 FC achieves a max efficiency gt
  75, at gt 1.0 W/cm2, under ambient pressure and
  temperature.
• Optimized catalysts give a high conversion
  efficiency and negligible gas production,
  allowing sealed units.
• Simple system design for liquid fuel, plus
  innovative manufacturing processes, open
  applications Ws to kWs.
• The unitized regenerative cell opens up added
  portable applications.
• Near Term Laptop and UPS units provide compact
  designs with long run-times.
• Also, air independent applications, e.g.
  satellite power are close at hand.
• Long Term Automobiles and spacecraft will
  benefit from Direct NaBH4 fuel cells.