150W Portable Direct Methanol Fuel Cell Power Supply/Battery Charger

150W Portable Direct Methanol Fuel Cell Power Supply/Battery Charger

Lawrence J. GestautCecelia Cropley

Giner Electrochemical Systems, LLCNewton, MA

2005 Joint Service Power ExpoTampa, FL - May 4, 2005

Why Fuel Cells?Why Fuel Cells?

Fuel cells … can offer quiet operation, a lower heat signature, fuel efficiency, … supporting communications, surveillance and other electronic equipment.

- Fuel Cell Today, April 20, 2005

Battery LogisticsBattery Logistics“Marines reported they were down to less than a 2-day supply” of primary batteries during OIF combat operations.

“CECOM officials said they were developing newer, lighter-weight rechargeable batteries…to reduce dependence on disposable batteries.”

US GAO “Actions Needed to Improve the Availability of Critical Items during Current and Future Operations”, April 2005, pps. 90,95

Battery LimitationsBattery Limitations

Portable power is critical, but

–Batteries can not provide increasing energy demands

–Primary batteries are a logistic and cost concern

–Secondary batteries require a portable and reliable charger

What is a Direct Methanol Fuel Cell?What is a Direct Methanol Fuel Cell?

CH3OH + H2O → CO2 + 6H+ + 6e-

3/2 O2 + 6H+ + 6e- → 3H2O

CH3OH + 3/2 O2 → CO2 + 2H2O

No compressed hydrogen– No reformer

ApplicationsApplications

•Small systems

– 20 W battery replacements

•Mid systems

– 150 to 500 W generators/chargers

•Large systems

– 2 to 5 kW diesel generator replacements

Types of DMFC Small SystemsTypes of DMFC Small Systems

• Natural air convection

• Passive water management

• Passive cooling

• Low current density

• >30% methanol possible

• Generally planar cells

Small SystemSmall System

Toshiba 12W/20W peak

Photo from Fuel Cell Today

Types of DMFC Mid & Large Systems

Types of DMFC Mid & Large Systems

• Discrete components

• Forced air

• Active water management

• Active cooling

• Moderate current density

• Dilute methanol water mix

Types of DMFCLarge Stacks & SystemsTypes of DMFCLarge Stacks & Systems

800 W System

1.5 kW Stack

GES Approach to DMFC GES Approach to DMFC

• Bipolar stack, operating at high power density

• Neat methanol fuel, on-board dilution• Operate at 60-70°C• Near-atmospheric air supplied by blower

M

MeOHReturn

CathodeOut

Air In

Drain

Air/WaterSeparator

M

M

M

Condenser

MeOHCooler

M

SumpPump

MeOH+H 2OMixing Tank

MeOHTank

AirPump

Air/WaterSeparator

MeOH Inlet

DMFC Stack

AnolytePump

DMFC SchematicDMFC SchematicDMFC SchematicDMFC Schematic

Direct Methanol Fuel Cell (DMFC)Direct Methanol Fuel Cell (DMFC)

• 6.8 kg

• 10 liters

DMFC OperationDMFC Operation

•Transportable

•Rapid start

•Load following

•Low thermal signature

DMFC RefuelingDMFC Refueling

• Liquid fuel• Refuelable “on-the-fly”

Advantages of DMFCAdvantages of DMFCAdvantages of DMFCAdvantages of DMFC

• High system energy density

• Safe and easy transport

• Long membrane lifetime

• Reactant humidification is not required

Fuel Comparison1500 W-hr (includes tank)

Fuel Comparison1500 W-hr (includes tank)

Neat

CH3OH

2000 psig cylinder

Metal hydride canister

Volume 1.5 liters 8.8 liters 4.5 liters

Weight 1.25 kg 13.2 kg

(80 g H2)

6.8 kg

Refillable by User?

YES NO NO

Disadvantages of DMFCDisadvantages of DMFC

• Lower cell voltage and lower current density

– Larger stack, but light and compact

• Fuel efficiency

– Currently ~17%,

– Forecast ~25%

Fuel Cell Performance ComparisonFuel Cell Performance Comparison

0 50 100 150 200 250 3000

100

200

300

400

500

600

700

800

900

1000

Current Density (mA/cm²)

Term

inal

Vol

tage

(mV)

MeOH/Air (60°C)

MeOH/Air Commercial Target (60°C)

H /Air (80°C)2

Numbers and total weigtht of Li/SO2 batteries needed to generate the same electric energy equivalent to a DMFC system at

120W rate (9A discharge). Li/SO2 battery: 1.027Kg, 176Wh. The data were obtained by Gainer 120W DMFC system.

0

10

20

30

40

50

60

70

0 20 40 60 80 100 120

Time (Hr)

Wei

ght (

Kg)

0

10

20

30

40

50

60

70

80

90

100

Num

ber o

f Li/S

O2

bate

ries

Weight of all fuel,water and DMFCWeight of allbatteriesNumber of BatteryNeededWeight of fuel

I = 9A

Primary Batteries ComparisonPrimary Batteries Comparison

GES 150 W DMFCGES 150 W DMFC

•6.8 kg•10 liter•3 hours operation with stored fuel

•Rapid start•Excellent load following

Future DevelopmentFuture Development

Reduce stack weight and volume by > 25%

– Increase power density

• Improve catalysis and structures

• Improve mass transfer

• Reduce methanol crossover

– Improved Stack Design

• Lighter/thinner end and bipolar plates

•Improve reliability, durability and ruggedness

•Store and operate over military temperature range

•Reduce thermal and acoustic signatures•Decrease unit size and weight

Systems Engineering IssuesSystems Engineering Issues

ConclusionsConclusions

•150W DMFC provides >60% weight reduction compared to primary batteries for 72-hour missions

•DMFCs have many advantages including ease of fueling

•DMFC could be fielded in the near term

AcknowledgementsAcknowledgements•DARPA

•Army Research Laboratory

•Jet Propulsion Laboratory

•Parker Hannifin