1. Iron-Air Cell and Battery Studies
B. G. Demczyk
Westinghouse Science & Technology Center
Collaborators:
C. T Liu, W. A. Bryant, E. S. Buzzelli,
P. L. Ulerich and R. E. Grimble
2. - Low cost, readily available materials
- $90./kWh
- 10¢/mile
- Minimal environmental hazards
- reaction product (Fe electrode) contained in cell
- minimal electrolyte required
(air electrodes part of containment)
- Performance as good or better than alternative advanced
systems
- > 0.02 HP/lb. power to weight ratio
- > 100 miles vehicle cruising range
(near-term (80% DOD), 1900 lb. vehicle)
- Near ambient temperature (< 40º C) operation
→ Limitation is cycle life of bifunctional air electrode ←
Advantages of Iron-Air System
4. Electrode Performance
S.O.A.+ Near Adv.
Term Tech.
Iron Electrode :
Utilization* (A-hr./gm) 0.4 0.5 0.6
Discharge (mV)**
@ 50 mA/cm2 -930 -950 -950
@200 mA/cm2 -870*** -850 -950
Charge Voltage (mV)
@ 25 mA/cm2 -1050 -1050 -1030
Charge Efficiency 0.9 > .95 > .95
Cycle Life >200 50 1000
Air Electrode :
Weight (g/cm2) 0.2 0.18 0.15
Ag Content (mg/cm2) <1 <1 <1
Discharge (mV)*
@ 25 mA/cm2 -100 -060 0
@100 mA/cm2 -200 -150 -100
Charge Voltage (mV)**
@ 12.5 mA/cm2 +500 +480 +440
Cycle Life 300 500 1000
*At C/4 rate; ** vs. Hg/HgO reference; *** @200 mA/cm2
+ refers to current performance levels
5. Characteristics of 400 cm2 cells
Performance
Near Adv.
Term Tech.
Cell Voltage* (V) 0.89 0.95
Cell Capacity (A-hr.) 80 80
Power Density(W/kg)
Sustained* 37 40
Acceleration** 171 200
Energy Density(W-hr./kg) 150 180
Energy Efficiency 0.5 0.6
Cycle Life 500 1000
*@25 mA/cm2, each air (C/4);
** @150 mA/cm2, (3C/2);
*** to 80% depth of discharge
Weight (g)
Near Adv.
Term Tech.
Iron Electrode (0.4 g/cm2) 160 130
Air Electrode 144 120
Electrolyte (@ 1.27 g/cc) 60 60
Cell Casing 70 70
Current Collector* 40 40
Total 474 420
* external of electrodes
N.B. :Performance levels are that observed in 100 cm2 cells.
6. Five Cell Module Characteristics*
Near Adv.
Term Tech.
Weight (kg) 2700 2100
Electrolyte-Gas Manifold(g) 170 130
Interconnectors (g) 50 50
Total Module Weight (g) 2920 2280
Total Module Volume (L) 2.12 1.65
Energy Content (Wh) 322 375
Energy Density (Wh/kg) 110 164
Power** (W) 260 415
Power Density* (W/kg) 90 180
Volume Energy Density (kWh/L) 0.13 0.23
Energy Efficiency >0.5 0.6
•400 AH capacity, 40 kWH energy content
•@ 4H discharge rate
**@150 mA/cm2
N. B. Near-term utilized in mission analysis
Each module has O2 supply and electrolyte circulation
systems.
7. Battery (120 Module*) Parameters
20% wt. and
Near Adv.
Term Tech.
Weight (kg) 310 273
Auxiliary Subsystems (kg) 30 25
Casing &Interconnectors (kg) 30 25
Total Battery Weight (kg) 370 325
Total Battery Volume (L) 280 200
Energy Content (kWh) 42.2 45
Energy Density (Wh/kg) 114 139
Power** (kW)
@500 A 40 45
@600 A 45 50
Power Density* (W/kg)
@500 A 108 138
@600 A 132 154
Volume Energy Density (kWh/L) 0.15 0.225
Energy Efficiency >0.5 0.6
* 120 modules (five 400cm2 cells in parallel) connected in
series @ 100V
**@150 mA/cm2
20% weight and 10% volume allowance
For air supply and electrolyte circulation
subsystems (powered by battery, casing and
Interconnectors.
8. Fe-Air Battery In a Nutshell
- Fe-air cell: 2-400cm2 air electrodes & 1 central Fe electrode
- air electrodes retain electrolyte as casing material
- Sponge powder iron electrode
- 25 w/o KOH w/15g/l LiOH electrolyte
- Carbon-based Ag-catalyzed bifunctional air electrode
Module = 5-400cm2 cells in parallel
- each w/O2 supply & electrolyte circulation
Battery = 120 modules in series (100V)
- 20% wt. & 10% volume penalty for air supply and electrolyte
circulation subsystems (powered by battery), casing & interconnectors
- 140 (120) Wh/kg, energy (power) density
- Near-term: cruising range (80% DOD) > 100 mi. & PWR .02
HP/lb. for 1900 lb. vehicle (25 & 150 mA/cm2 cruise and acceleration)
→ This is as good or better than alternative advanced systems ←
9. Comparison with Current Technology*
Pb-Gel NiMH Na-NaCl2 Li-Ion Fe-Air
Energy Density (Wh/kg) 20–50 40–80 100–120 110 114-139
Power Density (W/kg) 80–100 <200–1300 110–150 500 108-154
Life cycles 700–800 2000 >600 >2000 1000
Operation T (C) -10 to 40 -20 to 60 >300 -20 to 6 40-50
Selling price ($/kWh) 50–150 200 200 300–1000 90
Notes: Mature Fast Requires Needs thermal
Technology charging heating/cooling management system
possible system
* Data taken fron reference 9, except, Fe-Air, which is adapted from reference 2.
10. Mission Analysis Modeling
Constraints
- Battery recharge in 10 hours or less
- - 40 to 60 ◦C operating T
- $90./KWh cost
- Maintenance limited to periodic water makeup
- Driveline component (DC motor, controller, 3 sp. transmission)
efficiencies independent of power rating & equivalent for
any operating point (motoring or regenerating).
- -Fe-air cell performance levels at near term & advanced
technology baselines
- 0.49 Wh/gFe constant regenerative braking energy density
- 20% weight & 10% volume penalty for auxiliary systems
((pumps, radiators), battery case and interconnections.
- 50% SAE 227(A)-D cycle & 50% 90 km/hr. cruise
- Two or five passenger vehicle
- Limited or intermediate performance levels
11. Analysis Methodology
↑
AC or DC
↑
1,2,3 speed
or CVT
Specify vehicle PMR and
range @ 80% DOD over a
driving cycle:
Program sets differential
and iterates drivetrain
component
(battery, controller, motor,
transmission ) until total
vehicle weight is + 10% of
prior run
12. Cell Electrical Characteristics
Cell Polarization Curve
Cell Energy vs. Power
Data used by program to determine
battery capacity consumed by
vehicle each second of driving
cycle.↓
↑ ≈ (0 + gradual increase)/2
13. Cell Modelling- Electrical
V = Vo exp(-ai) Pb = V i Aa
Eb = (F V e) WFe e = i/ [ i + b exp(Mi)]
Aa = battery anode area (~peak power), ( m2); a, b, F, M =empirical constants;
Eb = cell energy content (Wh); e = empirical function; i = current density (A/m2);
Pb= cell output power (W); V = cell output voltage (V); Vo = maximum cell output voltage (V);
WFe = mass of iron in cell (total energy content), (kgFe).
N.B. e represents the effective specific energy density/Σ (effective specific energy density/ + cell losses
(~ exp. ↑ w/i)).
Energy densities include 10% penalty for auxiliary system (pumps, radiators) usage.
Regenerative braking modeled as constant 0.49 Wh/gFe (not ~ charge rate)
to account for over potential inefficiencies.
N. B.: e ~ energy efficiency= specific energy/S(specific energy + losses) ~ e exp(i)
at low I, energy density is ≈ constant
effective energy density is used to compute battery capacity consumed by vehicle each second.
14. Battery Simulation in a Nutshell
- two of 4 Fe-air vehicles 2P (commuter vehicle), 5P (family/carpool)
- 1 of 8 drive trains (DC motor & 3 sp. Transmission)
- specify PMR & range (to 80% DOD) over driving mission
- (50% SAE (A)-D urban cycle, 50% constant velocity cruising)
- range (80% DOD); accel. = peak power @ trans/Vmass (curb + 136 kg)
- based on 100 w/kg & 110WH/kg SOA projections.
- $90./kWh
- program sets differential & integrates drivetrain components
(DC motor, controller & transmission)
- components not proportional to power ratings & equivalent @ all
operating points (motoring or regenerating)
=> get battery, motor, controller & transmission sized for a given Fe-air
cell characteristics
driven over cycle each second => resize until D , 10kg between runs
overnight (8 hr.) recharge permitted (ICE equivalent excluded)
15. Cell Modelling- Mass & Volume
Wb = K1 WFe + K2 Aa
Vb = K3 WFe + K4 Aa
Wb = total battery mass (Kg)
Vb = total battery volume (l)
K1 = ratio of Wb to iron mass (kg/kgFe) = 1.75*; K2 = ratio of Wb to anode area (kg/m2) = 8.75*
K3 = ratio of Vb to iron mass (l/kg(Fe)) = 1.375*; K4 = ratio of Vb to anode area (l/m2) = 6.87*
- Half the battery weight and volume attributed to the iron content and half to the anode area
- K1, K2, K3 and K4 based on 40 kW (120 modules in series, each with five 400cm2 cells in parallel).
- 10% volume and 20%weight penalty for auxiliary subsystems.
16. Drive Cycle
←Used here
solve each second=> get avg. transmission power
=> energy utilized (Fe consumption (~ inverse mileage)) computed & S over cycle
To overcome rolling friction, areal drag & accel. of vehicle mass)
PRL = [0.2777*a*v + 0.038*v*t + 0.0278*G*v + 4.73 x 10-5 **v2 +
3.78 x 10-7*v3]*Wv + 1.315 x 10-2 *C*a*v3
a = acceleration (m/s2); A = vehicle frontal area (m2)
C =aerodynamic drag coefficient; G = grade (%)
V = vehicle velocity (km/h); Wv = vehicle total mass (kg)
a = A exp (-t*B);
V = (A/B) [1-exp(-t*B)]
B = 0.05 s-1,; A = 4.78 k/hr.-
sec
← a = - 0.447m/s2
a = - 1.1365m/s2 →
← a = 0.718m/s2
17. Vehicle Mission Analysis
Notes:
Near Term (Advanced Technology) levels;+ @80% depth of discharge; ++ power measured at input of transmission;
mass = curb mass + 136 test mass; * for 50% highway (90 km/h) & 50% SAE J227(A)-D cycle; ** no regenerative braking
capability; DC motor-controller, 3 speed transmission; cost of battery:$13./kg
Batt. Vehicle Total Fe Cons.*
Vol. (Dm3) Area (m2) Wt. (kg) Wt.(kg) (Wt.(kg) (g/km)
137 1.75 178 462 640 311
(102) (1.44) (132) (454) (586) (198)
220 3.47 285 988 1273 486
(161) (2.78) (207) (926) (1133) (294)
224 2.76 291 507 798 293
235 2.86 305 521 826 327
(155) (2.09) (200) (471) (671) (174)
382 5.36 495 1054 1549 486
399 5.47 518 1063 1581 551
(260) (4.09) (337) (978) (1315) (277)
Performance Vehicle Range+ PWR++
Level Type (km) (W/kg)
Limited 2P 120 26
(2P) (120) (26)
5P 120 26
(5P) (120) (26)
Intermediate 2P 240 33
2P** 240 33
(2P) (240) (33)
5P 240 33
5P** 240 33
(5P) (240) (33)
Requirements↓ Results↓
Vehicle Performance Curb Maximum Frontal
Type Level Mass (kg) Payload (kg) Area (m2)
2P Limited 427 181 1.67
2P Intermediate 460 181 1.67
5P Limited 931 408 2.14
5P Intermediate 987 408 2.14
Vehicle Specifications↑
18. Vehicle Design-5 Passenger*
Fe Consumption vs. Power/mass
Vehicle Mass vs. Power/mass Vehicle Mass vs. Range
Fe Consumption vs. Range
* PMR 26 kg; Range w/50-50 highway driving; DC motor; 3 speed transmission
19. Thermal Management Modeling
Motivation:
-Some chemical energy is converted to thermal energy
sensible heat (air stream) & latent heat (entrained water vapor).
-This must be removed to maintain a cell temperature between
40 and 60 C.
-It is necessary to recover some of this energy to avoid excessive
cooling under some ambient conditions.
Assumptions:
-Cooling via airstream alone (stoichiometric ratio 10)
-Airstream leaves battery at electrolyte temperature
- 10 kW battery output power level
-Heat losses through ducting and battery ignored
Input-Output Parameters:
Input Output (along flow train)
-T (operating and ambient) -P, T, mass flow rates,
-Heat Exchanger ∆T -energy additions
20. Thermal Management System
Thermal Management Arrangement-
(Air-electrolyte heat exchange).
Without Heat Exchanger-
(Metered quantity of air exhausted upstream of dehumidifier).
Heat Exchanger (HX).
Humidifier/Dehumidifier
22. System Analyses Summary
. Proposed 40 kWh battery ($90./kWh)
- fulfills 120 km (2P and 5P) and 240 km (2P) missions
- satisfies 240 km (5P) mission with 30% mass and
volume scale-up.
. Regenerative braking capability makes possible a 5% battery
and 3% total vehicle weight reduction.
. Thermal management (40-60C) attainable, using only input air
as coolant.
. Parasitic energy requirements within estimates.
. System weight and volume can be reduced significantly
with space efficient design configuration
23. Battery Systems Analysis
Results:
- Primary Wb & Vb depends: primarily on vehicle loading;
secondarily on range & PMR
- Battery area depends equally on both
- Loading capacity dependent parameters vary most (D battery area)
- Regenerative braking enables 5% battery & 3% vehicle weight reduction
Restores a portion of the consumed iron
- Near-term and (adv. tech). Fe-air battery satisfies all except 5P
intermediate mission, which requires 33% vol. (3%wt.) & 36%(30%)
scale-up @40./kWh
Overall Summary:
- 40kWh battery ($90./kWh) sufficient for 2 &5P 120 km and 2p 240 km
(5P w/scale-up).
24. References
1). B. G. Demczyk and R. E. Grimble, “Thermal Analysis of the Iron-Air Battery System, 178th
Electrochemical Society Fall Meeting Abstracts 1980, Abstract 120.
2).B. G. Demczyk, W. A. Bryant, C. T. Liu and E. S. Buzzelli, “Performance and Structural
Characteristics of the Iron-Air Battery System”, 15th Intersociety Energy Conversion
Engineering Conference Proceedings, 1980, Abstract 809290.
3).B. G. Demczyk, P. L. Ulerich and E. S. Buzzelli, “Iron-Air Battery Vehicle Mission Analysis”, 16th
Intersociety Energy Conversion Engineering Conference Proceedings, 1981, Abstract
818323.
4). E. S. Buzzelli, L. B. Berk. B. G. Demczyk. A. Gibney. C. T. Liu, and D. Zuckerbrod, Iron-Air
Battery Development Program, Interim Report 1981 (U.S. Department of Energy
Contract No. 7335709).
5). E. S. Buzzelli, B. G. Demczyk. A. Gibney. C. T. Liu, P. L. Ulerich and R. E. Grimble, Iron-Air
Battery Development Program, Final Report 1981 (U.S. Department of Energy
Contract No. 7335709).
25. References
6). E. S. Buzzelli, B. G. Demczyk. A. Gibney. C. T. Liu, D. Zuckerbrod, P. L. Ulerich and R. E.
Grimble, Iron-Air Battery Development Program, Final Report 1983 (U.S. Department
of Energy Contract No. 7335709).
7).P. L. Ulerich, B. G. Demczyk and E. S. Buzzelli, “Iron-Air Battery-in-Vehicle Mission Analysis of
the Iron-Air System” , Westinghouse R&D Center Report 81-9J22-EVMOT-P1, 1981.
8). E. S. Buzzelli, B. G. Demczyk. A. Gibney. C. T. Liu, and R. E. Grimble, P. L. Ulerich Iron-Air
Battery Development Program, Summary Report 1980, Westinghouse R&D Center
Report 81-9E62-MOBET-R1, 1981.(U.S. Department of Energy Contract No.
7335709).
9). Peter Hofmann (2010): Hybridfahrzeuge – ein alternatives Antriebskonzept für die Zukunft,
Wien 2010.
26. Acknowledgements
Air Electrode Fabrication:
P. Gongaware, R. Egidio, I. Rittko
Air Electrode and Fe-Air Cell Testing:
G. Leap
This work was supported by
a U.S. Department of Energy contract EY-76-C-02-2949,*000
