R. K. Ahluwalia, X. Wang, E. Doss, R. Kumar 2005 USDOE ... · R. K. Ahluwalia, X. Wang, E. Doss, R. Kumar 2005 USDOE Hydrogen, Fuel Cells & Infrastructure Technologies Program Review

A U.S. Department of EnergyOffice of Science LaboratoryOperated by The University of Chicago

Argonne National Laboratory

Office of ScienceU.S. Department of Energy

Fuel Cell Systems AnalysisFuel Cell Systems AnalysisR. K. Ahluwalia, X. Wang, E. Doss, R. Kumar

2005 USDOE Hydrogen, Fuel Cells & Infrastructure Technologies Program Review

Crystal City, VAMay 23-25, 2005

This presentation does not contain any proprietary or confidential information

Project ID# FC35

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Pioneering Science andTechnology

Hydrogen, Fuel Cells & Infrastructure Technologies Program

OverviewOverviewTimeline

• Start date: Oct 2003• End date: Open• Percent complete: 30%

BarriersA. Compressors/ExpandersC. Fuel Cell Power System

BenchmarkingD. Heat UtilizationH. Start-up TimeR. Thermal and Water Mgmt

Budget• Total funding: $400K

- DOE share: 100%• FY04 funding: $400K• FY05 funding: $400K

Partners• Honeywell CEM+TWM projects• IEA Annexes 17 and 20• FreedomCAR fuel cell tech team• HTM working group

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ObjectivesObjectives

Develop a validated system model and use it to assess design-point, part-load and dynamic performance of automotive fuel cell systems.• Support DOE in setting R&D goals and research directions• Establish metrics for gauging progress of R&D plans

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ApproachApproach

Develop, document & make available versatile system design and analysis tool.• GCtool: Stand-alone code on PC platform• GCtool_ENG: Coupled to PSAT (MATLAB/SIMULINK)

Validate the models against data obtained in laboratory and at Argonne’s Fuel Cell Test Facility.

Apply models to issues of current interest.• Work with FreedomCAR Technical Teams. • Work with DOE contractors as requested by DOE.

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Membrane Humidifier ModelMembrane Humidifier ModelCounterflow shell and tube configuration (Perma Pure)• Mass transfer determined from gradient of membrane

water content (λ) and diffusivity D(λ,T)• Coupled heat and mass transfer

Dry Air Inlet

Wet Air Outlet

Dry Exhaust Outlet

Wet Exhaust

Inlet

0

20

40

60

80

100

120

0 0.2 0.4 0.6 0.8 1x/L

Rel

ativ

e H

umid

ity

30

40

50

60

70

80

90

Tem

pera

ture

, o C

RH, Wet

RH, Dry

Temperature, Wet

Temperature, Dry

WetDry

Air Flow rate: 8. g/sPressure: 2.5 atmO 2 Utilization: 50%Dry Air Inlet Temp: 45 °C Wet Air Inlet Temp: 80 °CWet Air RH: 100%

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Membrane Humidifier Model Validation Membrane Humidifier Model Validation (Data from Honeywell / Perma Pure)(Data from Honeywell / Perma Pure)

Mass transfer decreases above 50°C inlet dry air temperature

50

55

60

65

70

75

80

25 30 35 40 45 50 55 60 65 70

Dry Air Inlet Temperature, o C

Dew

Poi

nt T

empe

ratu

re o

f Hum

idifi

ed A

ir, o C

Dry Air: 5.7 g/s,2.0 atm

Dry Air: 8 g/s, 2.5 atm

Dry Air: 1.7 g/s, 1.3 atm

Dry Air Wet AirTemperature oC 25 - 70 80Relative Humidity % Dry 100Pressure atm 1.3 - 2.5 1.3 - 2.3Air Flow Rate (Dry) g/s 1.7 - 8 1.5 - 7.2

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Pressurized FCS with Membrane HumidifierPressurized FCS with Membrane Humidifier

• Demister between stack and humidifier not required• Compressor discharge cooled with low-T stack coolant or air• Possible to maintain stack at 80oC at all loads• 60-85% outlet RH @ 25-50% ambient RH

Electric Motor

Hydrogen

PEFCStack

Exhaust

Humidified Air

Air

Membrane Humidifier

Radiator

Air Cooler70°C

55°C

Electric Motor

Hydrogen

PEFCStack

Exhaust

Humidified Air

Air

Membrane Humidifier

Radiator

Air Cooler70°C

55°C50

60

70

80

90

100

0.0 0.2 0.4 0.6 0.8 1.0Relative Mass Flow Rate

Hum

idifi

ed A

ir R

H,%

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40

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60

70

80

Hum

idifi

ed A

ir Te

mpe

ratu

re ,

o C

Ambient RH: 50% Pressurized System: 2.5 atmStack Temperatutre: 80 °CAmbient Temperature: 40°COxygen Utilization: 50%Membrane Area: 2.85 m 2

Ambient RH: 25%

Inlet from Air Cooler

Outlet to Cathode

Pressurized FCS with Enthalpy Wheel HumidifierPressurized FCS with Enthalpy Wheel Humidifier

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Model developed in FY04, validated with Honeywell/Emprise data• EW model used in FY05 to support TWM Honeywell program• Evaluated EW for high-temperature membranes at 120oC

Demister

Electric Motor

Hydrogen

PEFCStack

Air Exhaust

Humidified Air

Coolant

Enthalpy Wheel

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With EW in HTMWith EW in HTM--FCS, cathode air at 120FCS, cathode air at 120ooC can be C can be humidified to 10humidified to 10--30% RH at 2.5 atm and <15% RH at 1 atm30% RH at 2.5 atm and <15% RH at 1 atm

0

5

10

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45

50

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Relative Mass Flow Rate

Rel

ativ

e H

umid

ity, %

47 °C

27 °C

-20 °C

0 °C

Cathode Inlet RH

Cathode Outlet RH

Pressurized System: 2.5 atmStack Temperatutre: 120 °COxygen Utilization: 50%Enthalpy Wheel: Φ5.6" ×6"GHSV: 704,000 h -1

0

5

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0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Relative Mass Flow Rate

Rel

ativ

e H

umid

ity, %

47 °C

27 °C

-20 °C

Cathode Inlet RH

Cathode Outlet RH

Ambient Pressure SystemStack Temperatutre: 120 °COxygen Utilization: 50%Enthalpy Wheel: Φ5.6" ×6"GHSV: 704,000 h -1

% Flow % RH In % RH ηMT (%) % RH In % RH ηMT (%)

100 9-17 27-34 25-45 6-9 15-16 35-4510 31-34 33-35 80-85 33 36 80-85

100 20-30 35-42 40-60 10-13 17-19 50-6010 35 38 80-85 37 40 80-85

Pressuized System Ambient Pressure System

EW Space Velocity = 700,000/h

EW Space Velocity = 350,000/h

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SelfSelf--Start of PEFC Stacks from SubStart of PEFC Stacks from Sub--Freezing Freezing TemperaturesTemperatures

Reactions with species transport in five-layer MEA Formation and melting of iceEffect of ice on ECSA & transport

Capillary transport of water in GDL & porous catalystsT distribution in bipolar plate, flow channels and MEA

2-D Dynamic Simulation Model

Simulation under conditions for which self-start is possible at -20oCP = 1 atm, Vcell = 0.4 V, SGice = 0.5, 50-µm membrane

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 50 100 150 200Distance from Gas Channel, µm

Ice

Vol

ume

Frac

tion

Cell Voltage: 0.4V

5 s

10 s

15 s

18 s

CGDL CCL

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0


Cell Voltage: 0.4V

22 s

19 s

18 s

CGDL CCL

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Simulation Result: Liquid Water FormationSimulation Result: Liquid Water FormationSimulation under conditions for which self-start is possible • Ice and liquid water coexist between 18 and 22 s• Liquid water volume decreases for t > 20 s• May need to humidify air because stack heats up to

70oC at 55 s

0.00

0.02

0.04

0.06

0.08

0.10


Liqu

id W

ater

Vol

ume

Frac

tion

Cell Voltage: 0.4V

18 s

19 s

20 s

0.00

0.02

0.04

0.06

0.08

0.10


Cell Voltage: 0.4V

20 s

22 s35 - 40 s

45 s

50 s

55 s

25 s

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Simulation results are sensitive to the assumed Simulation results are sensitive to the assumed bulk density of icebulk density of ice

• P = 1 atm, Vcell = 0.6 V, 50-µm membrane, Ti = -20oC • At SG = 0.2, cathode is completely covered with ice and

stack temperature equilibrates below the melting point.• Self start is possible for SG > 0.5.

0

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0 10 20 30 40 50 60Time, s

Ave

rage

Cur

rent

Den

sity

, A/c

m2

P = 1 atm Cell Voltage = 0.6 VMembrane Thickness = 50 µm

0.5

0.2

Specific Gravity of Ice = 0 .8

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Simulated Effects of Membrane Thickness and Simulated Effects of Membrane Thickness and PressurePressure

• More rapid build-up of ice on cathode catalyst in a pressurized stack

• Lower current density at pressure and with thicker membranes because of larger Ohmic overpotential across membrane

0

0.1

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0 10 20 30 40 50 60Time, s

Ave

rage

Cur

rent

Den

sity

, A/c

m2

P = 1 atmSpecific gravity of ice = 0.5Cell Voltage = 0.6 V

Membrane Thickness: 100 µm

50 µm

0

0.1

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0 10 20 30 40 50 60Time, s

Ave

rage

Cur

rent

Den

sity

, A/c

m2

Specific gravity of ice = 0.5Cell Voltage = 0.6 VMembrane Thickness = 50 µm

P = 2.5 atm

1 atm

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Self start is generally easier at lower cell voltages• Self start is not possible at 0.8 V• Self start is possible at 0.6 V but there is an intermediate

period (25-30 s) over which the power decreases.• Start up is robust at 0.4 V.

0

0.3

0.6

0.9

1.2

0 10 20 30 40 50 60Time, s

Ave

rage

Cur

rent

Den

sity

, A/c

m2

Cell Voltage: 0.4 V

0.6 V

0.8 V

P = 1 atmSpecific Gravity of Ice = 0.5Membrane Thickness = 50 µm

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Simulated Effect of Stack Heating• Start-up from -20oC is more robust and faster if the

bipolar plate can be electrically heated.

0

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0 10 20 30 40 50 60Time, s

Ave

rage

Cur

rent

Den

sity

, A/c

m2

P = 1 atmSpecific Gravity of Ice = 0.5Cell Voltage = 0.6 VMembrane Thickness = 50 µm

No heating

725 W/m 2

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Alternate Methods of StartAlternate Methods of Start--up from Subfreezing up from Subfreezing TemperaturesTemperatures

Start-up Time: Time to place the FCS in a state where itis capable of producing 90% of rated power on demand.Start-up Energy Consumption: Additional fuel energyconsumed on FUDS w.r.t FCS at normal operating T.Alternate methods evaluated1. Internal oxidation of hydrogen on MEA catalyst

- Constrained by flammability limits2. External combustion of hydrogen

- Ineffective: 5.6 MJ of fuel energy needed to transfer 1.4 MJ needed to heat the stack to 0oC from -20oC

3. Insulated coolant tank with electrical heating4. Insulated stack with electrical heating

- Maintain stack at threshold temperature- Self-start stack at threshold T: < 10 s, 1 MJ of fuel energy

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Stack Heating to Threshold Temperature Stack Heating to Threshold Temperature Insulated Stack with Electrical HeatingInsulated Stack with Electrical Heating

• 1” insulation, 0.05 W/m.K• Stack cools from 80oC to

0oC in 13-25 h• A 40-kW hybrid battery

maintains stack at 0oC for 6-24 h

Ambient Cool-Down Heat LossTemperature Time to 0oC at 0oC

-10oC 25 h 20 W-20oC 19 h 40 W-40oC 13 h 80 W

• Periodically operate FCS for ~4 minat 25% powerRecharge the battery (480 W.h)Excess power (60%) to electrical heatersHeat the stack from 0 to 80oC5.3 MJ/day fuel energy consumption at -20oC ambient

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Completed study on fuel economy of hybrid loadCompleted study on fuel economy of hybrid load--following fuel cell vehiclesfollowing fuel cell vehicles

Issues addressed in the study • How much gain in fuel economy can we expect if FCEVs

are hybridized with energy storage systems?• How does the gain compare with ICE hybrids?• How is the gain affected by North American, European

and Japanese drive cycles?

ReviewersReviewers’’ CommentsComments

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Generally favorable reviews with recommendations to• Redirect away from fuel processing options• Study effect of sub-zero oC startup and operation• Place more emphasis on model development• Keep engaged in thermal and water management• Maintain close communications with fuel cell tech team

FY05 work scope consistent with above recommendations• Focusing on direct hydrogen fuel cell systems• Working on start-up from sub-freezing temperatures• Developing models for enthalpy wheels, membranehumidifiers, ice formation……..

• Working with Honeywell and TIAX• Member of fuel cell tech team

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Proposed Future WorkProposed Future Work

• Continue work on freeze-start of fuel cell systems• Continue collaboration with Honeywell on thermal and

water management system• Continue to support DOE/FreedomCAR development

efforts• Participate in validation effort • Explore CHP applications of FCS• Support HFCIT program on system analysis

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Publications and PresentationsPublications and PresentationsJournal PublicationsR. K. Ahluwalia, X. Wang, and A. Rousseau, “Fuel Economy of Hybrid Fuel Cell Vehicles,” Journal of Power Sources, (in print), 2005.R. K. Ahluwalia and X. Wang, “Direct Hydrogen Fuel Cell Systems for Hybrid Vehicles,” Journal of Power Sources, 139, 152-164, 2005. R. K. Ahluwalia, X. Wang A. Rousseau and R. Kumar, “Fuel Economy of Hydrogen Fuel Cell Vehicles,” Journal of Power Sources, 130, 192-201, 2004.

ConferencesR. K. Ahluwalia, X. Wang, and A. Rousseau, “Fuel Economy of Fuel Cell Hybrid Vehicles,” 2004 Fuel Cell Seminar, San Antonio, TX, November 1-5, 2004.R. K. Ahluwalia, X. Wang, R. Kumar, “Fuel Cell Systems for Hybrid vehicles,” 2004 International PEM Fuel Cell Conference, Hsinchu, Taiwan, October 14-15, 2004.R. K. Ahluwalia and X. Wang , “Performance of Hybrid Fuel Cell Vehicles,” Annex XX Meeting, Stuttgart, Germany, September 28, 2004.R. K. Ahluwalia and X. Wang, “Systems Level Perspective on Humidification in Direct Hydrogen Fuel Cell Systems with a High-Temperature Membrane,” USDOE High Temperature Membrane Working Group Meeting, Philadelphia, PA, May 27, 2004.

PresentationsR. K. Ahluwalia and X. Wang, “Startup of PEFC Stacks From Sub-Freezing Temperatures,” DOE Workshop on Fuel Cell Operations at Sub-Freezing Temperatures, Phoenix, AZ, February 1-2, 2005.R. K. Ahluwalia and X. Wang, “Fuel Cell Systems for Hybrid Vehicles,” DaimlerChrysler Research and Technology, Ulm, Germany, September 27, 2004.

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Hydrogen SafetyHydrogen Safety

• This is an analytical and computer modeling project. There are no hydrogen safety issues involved.

The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

Documents

R. K. Ahluwalia, X. Wang, E. Doss, R. Kumar 2005 USDOE ... · R. K. Ahluwalia, X. Wang, E. Doss, R. Kumar 2005 USDOE Hydrogen, Fuel Cells & Infrastructure Technologies Program Review