NaBH4/H2O2(Air) Fuel Cell Technology

Technical Presentation

CONTACT – Richard Dell at 919.870.9494

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

Reactions

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).

• 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)

NPL’s Cell Achieves Leading Power Densities

Theoretical Power Density

Current State of the Art Power

Density

UIUC/NPL’s NaBH4/H2O2

Cell2580 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-100C.

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.

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 15°C•Cell runs at 50% efficiency at highest rated load

UIUC/NPL NaBH4/H2O2 FCs Demonstrate Excellent PerformancePerformance Comparison of Various Fuel Cells

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Current Density (A/cm 2)

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NaBH4/H2O2 Fuel Cell

H2/H2O2 Fuel Cell

Alkaline H2/O2 Fuel Cell

PEM H2/O2 Fuel Cell

The V-I characteristics of various fuel cells, at room temperature, ambient pressure operation.

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

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

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

NaBH4 plant Fuel CellNaBH4

NaOH

NaBO2

Performance of NPL 500W NaBH4/H2O2 Fuel Cell

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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.

In Addition to Our Current Regenerative Cell Long Term Approaches Are Under Study

I. 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.

II. 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.

III. NaBO2 can be converted in situ in a unitized regenerative cell. Some progress has been made on this design and work is continuing.

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 >10000 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.

STID Performance Characteristics

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

Energy Density

Power Density (Peak)

Power Density (Nominal)

Cycle Life

Prototype 110 W-hr/kg 400 W/kg 110 W/kg >10000

In 5 Months 200 W-hr/kg 800 W/kg 220 W/kg >10000

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.

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 timeThe 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

20-W Laptop Power Unit

• In comparison: Micro Direct Methanol Fuel Cell20 W500 W-hr3.5 – 7 lbs

• NaBH4/H202 Micro Cell

20 W500 W-hr2.2 lbs

Schematic of proposed laptop power unit.

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.

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

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.

Parameter ValueMass of liquid fuel 100 kgSize of liquid fuel tank 20 galParasitic Mass 20 kgTotal Fuel System Mass 120 kgEnergy Density of Fuel System 2.2 kWh/kgVehicle Power Consumption 20 kWVehicle Speed 75 mphVehicle Range 500 mi

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

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

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.

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

In Summary, NaBH4 FCs Are Proceeding Rapidly

To Commercialization The NaBH4/H2O2 FC achieves a max efficiency > 75%, at

> 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.