Dynamics and Control of Membrane Hydration in a PEMFC

Transcription

1 Dynamics and Control of Membrane Hydration in a PMFC Syed K. Ahmed Donald J. Chmielewski Department of Chemical and Biological ngineering Presented at the American Control Conference: June 009

2 Outline PMFC Model Mat. & nergy Balances and lectrochemistry Membrane Model Controller Analysis Power/Temperature Control Manipulation of Hydration Profile

3 Dynamic Model of PMFC Cooling Air In Anode In (H, H O) Solid Material H H O Insulator Current Collector O N Jacket xhaust Cathode In (air) Parameters based on 1 kw scale. Humidified hydrogen feed Anode xhaust H O Cathode xhaust Air cooling is assumed. Gas Diffusion Layers (GDLs) Catalyst Layers Polymer Membrane cell

4 Dynamic Model of PMFC Material Balances nergy Balances dc H an an H in an H H mem in V F C, F C r A dt dc ( an) HO in an an an an an H O in an H O H O mem ( ) ( ) ( ) V F C, F C J A dt F C F C r J A in ( an) an an ( H H O ) mem dc O ca ca O in ca O O mem in V F C, F C r A dt dc ( ca) HO in ca ca) ( ca) ca ca H O in ca H O JH O ( ) ( V F C, F C dt F C F C r J A in ( ca) ca ca O H O mem A mem dt ca in in UA Vca Fca Tca Fca Tca ( Tsol Tca ) dt C p dt an in in UA Van FanTan FanTan ( Tsol Tan ) dt C p dt jac in in UA V jac FjacTjac FjacTjac ( Tsol Tjac ) dt C p dt Cp Vsol UA ( Tca Tsol ) sol ca dt UA ( T T ) UA ( T T ) Q A sol jac jac sol an an sol gen mem ca an jac

5 lectrochemical Model cell ner act ohm mt ner o 1 RT F RT F sol sol act ln j / j o j o o ( ( ca) C / o O C O ) PH P ln PH j o 1/ O O ohm mt IR tmem j 1 RT 1 F K sol ln j F K L mt D ( ca) GDL j mt L t j C L GDL ( ca) O j

6 Outline PMFC Model Mat. & nergy Balances and lectrochemistry Membrane Model Controller Analysis Feedback Control Feedback/Feed-forward Control

7 Water Transport in the Membrane LCTRO-OSMOTIC DRAG DIFFUSION

8 Hydration Model for MA C ( mem) J HO Jdiff Jdrag D z ( mem) HO j F Anode Solid Material Current Collector In Cathode (H, H O) H Air in O H + H + C ( mem) H O t D e C z ( mem) H O Anode xhaust H O H + H + H + H + H + H + N H O Cathode xhaust Boundary Conditions MA D D e e C z C ( mem) H O ( mem) H O z j F j F J J ( an) H O ( ca) H O 0 r H O 0 at at z 0 z m

9 Concentration Profiles ( mem C ) ( ) H O m ( an) C HO ˆ ( mem ) C o ( mem) C H O 0 ( ca) ˆ ( mem) C C HO m ( mem C ) ( z) HO Anode Gas GDL Membrane GDL Cathode Gas δ a δ m δ c

10 Water Content Profiles cell ner act ohm mt A/cm λ=ho/so A/cm A/cm Length Across PM (cm) Ohmic Loss: ohm j t mem dz ( z 0 ) Ionic Conductivity: ( ( z)) = (z)

11 Water Content Profiles Dynamic Simulation A/cm A/cm λ=ho/so A/cm Length Across PM (cm)

12 Outline PMFC Model Mat. & nergy Balances and lectrochemistry Membrane Model Controller Analysis Power/Temperature Control Manipulation of Hydration Profile

13 Power/Temperature Control Temperature Control Loop P e (sp) Power Controller F c o cell P e,, F a o j PMFC T sol (sp) + - PI F jac T sol

14 Power/Temperature Control 0.5 Power Density (watts/cm ) P e P e (sp) Time (seconds)

15 Power/Temperature Control

16 Power/Temperature Control! Water Content (0) ( mem /) ( mem ) Time (seconds)

17 Power/Temperature Control Power Density (watts/cm ) P e P e (sp) Time (seconds)

18 Power/Temperature Control

19 Power/Temperature Control! Water Content (0) ( mem /) ( mem ) Time (seconds)

20 Outline PMFC Model Mat. & nergy Balances and lectrochemistry Membrane Model Controller Analysis Power/Temperature Control Manipulation of Hydration Profile

21 Manipulation of Hydration Profile Ideal Profile Zero Slope Just Below λ=14! Water Content (0) ( mem /) ( mem ) Time (seconds)

22 Manipulation of Hydration Profile ( mem), sp C HO P e (sp) T sol (sp) Power/ Temp Controller + - G c c a Fo, Fo cell, F jac P e, j T sol u PMFC ( mem) C HO m! Water Content (0) ( mem /) ( mem ) Time (seconds)

23 Anode Bubbler Temperature 8 Upper Plot, 86 o C to 90 o C, Lower Plot, 86 o C to 8 o C! Water Content! Water Content

24 Cathode Bubbler Temperature Upper Plot, 40 o C to 50 o C, Lower Plot, 40 o C to 30 o C! Water Content! Water Content

25 Solid Temperature Set-Point 8 Upper Plot, 80 o C to 70 o C, Lower Plot, 80 o C to 90 o C! Water Content! Water Content

26 Combined Approach 14 Inc. Anode Bubbler Temperature Results: Flatten Slope Dec. Solid Setpoint Temperature Prevents Flooding - Water Content

27 Conclusions and Future Work Portion of the Puzzle Measurements Channel Complications Validations

28 Acknowledgements Argonne National Laboratory Department of Chemical & Biological ngineering, IIT