Transcript What is a Direct Methanol Fuel Cell?

150W Portable Direct
Methanol Fuel Cell
Power Supply/Battery Charger
Lawrence J. Gestaut
Cecelia Cropley
Giner Electrochemical Systems, LLC
Newton, MA
2005 Joint Service Power Expo
Tampa, FL - May 4, 2005
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 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 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?
CH3OH + H2O → CO2 + 6H+ + 6e3/2 O2 + 6H+ + 6e- → 3H2O
CH3OH + 3/2 O2 → CO2 + 2H2O
No compressed hydrogen– No reformer
Applications
•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 Systems
• Natural air convection
• Passive water management
• Passive cooling
• Low current density
• >30% methanol possible
• Generally planar cells
Small System
Toshiba
12W/20W peak
Photo from Fuel Cell Today
Types of DMFC
Mid & Large Systems
• Discrete components
• Forced air
• Active water management
• Active cooling
• Moderate current density
• Dilute methanol water mix
Types of DMFC
Large Stacks & Systems
800 W System
1.5 kW Stack
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
DMFC Schematic
Air/Water
Separator
Condenser
M
Air
Pump
DMFC Stack
Air In
Cathode
Out
Air/Water
Separ ator
M
Sump
Pump
MeOH
Tank
MeOH Inlet
MeOH
Cooler
M
MeOH+H 2O
Mixing Tank
M
MeOH
Return
Anolyte
Pump
M
Drain
Direct Methanol
Fuel Cell (DMFC)
• 6.8 kg
• 10 liters
DMFC Operation
•Transportable
•Rapid start
•Load following
•Low thermal
signature
DMFC Refueling
• Liquid fuel
• Refuelable
“on-the-fly”
Advantages of DMFC
• High system energy density
• Safe and easy transport
• Long membrane lifetime
• Reactant humidification is not required
Fuel Comparison
1500 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
YES
NO
NO
Refillable by
User?
Disadvantages of DMFC
• Lower cell voltage and lower current
density
– Larger stack, but light and compact
• Fuel efficiency
– Currently ~17%,
– Forecast ~25%
Fuel Cell Performance
Comparison
1000
Terminal Voltage (mV)
900
800
700
600
500
MeOH/Air (60°C)
400
MeOH/Air Commercial Target (60°C)
300
H2 /Air (80°C)
200
100
0
0
50
100
150
200
Current Density (mA/cm²)
250
300
Primary Batteries
Comparison
70
100
60
Weight (Kg)
50
40
I = 9A
90
80
70
60
50
30
40
30
20
20
10
10
0
0
0
20
40
60
80
100
120
Time (Hr)
Numbers and total weigtht of Li/SO 2 batteries needed to generate the same electric energy equivalent to a DMFC system at
120W rate (9A discharge). Li/SO 2 battery: 1.027Kg, 176Wh. The data were obtained by Gainer 120W DMFC system.
Number of Li/SO 2
bateries
Weight of all fuel,
water and DMFC
Weight of all
batteries
Number of Battery
Needed
Weight of fuel
GES 150 W DMFC
•6.8 kg
•10 liter
•3 hours operation
with stored fuel
•Rapid start
•Excellent load
following
Future 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
Systems Engineering
Issues
•Improve reliability, durability and
ruggedness
•Store and operate over military
temperature range
•Reduce thermal and acoustic signatures
•Decrease unit size and weight
Conclusions
•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
Acknowledgements
•DARPA
•Army Research Laboratory
•Jet Propulsion Laboratory
•Parker Hannifin