1 Julien Ramousse, Kodjo Agbossou, Yves Dubé and Pélopé Adzakpa Hydrogen Research Institute (IRH), Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, Québec, G9A 5H7, Canada NHA Annual Hydrogen Conference March 30 – April 3, 2008 Sacramento, United States Florent Brèque, PEM Fuel Cell optimal humidification relating to operating conditions

2 1) Presentation Issues IRH research project Presented work objectives 2) PEMFC model Mass transport Numerical model 3) Results & discussion Optimal inlet relative humidities Discussion on humidification strategies OutlineOutline

3 Outline Presentation Results IRH project Assumption Optimal RH Strategies Fuel cell control issue Air compressor Fuel Cell H2 tank Water pump H2 pump How to choose the operating parameters for the maximum system efficiency ??? Electricity production Electricity consumption Depend on operating parameters Conclusion Presented work Model Numerical Mass transport

4 Modeling (understanding, control tool) Control strategy (optimization of the FC system) Integration on the grid (islanding issues) IRH research project Results Assumption Optimal RH Strategies Outline Conclusion IRH: Institut de Recherche sur l’hydrogène PEM Fuel Cell Modeling and Control for Distributed Power Systems Presentation IRH project Presented work Hydrogen Research Institute Model Numerical Mass transport

5 No water in the membrane Lower membrane conductivity Liquid water in the GDL Prevent gas transport Water is needed in the cell: Excess water is harmful: Drying Flooding How to reach the best internal cell humidification ??? Water management issue Results Assumption Optimal RH Strategies Outline Membrane GDL Gas channel Water production (function of the load) GDL Gas channel AnodeCathode Conclusion Presentation IRH project Presented work Model Numerical Mass transport Inlet anode humidification Inlet cathode humidification

6 Determination in steady state of the optimum inlet cathode relative humidity for any load and for different configurations: Comparison of the different humidification strategies Objectives of the presented work Presentation Results Presented work Assumption Optimal RH Strategies Outline Conclusion IRH project Dead-end or flow-through mode With or without anode humidification Inlet anode humidification Membrane GDL Gas channel GDL Gas channel AnodeCathode Inlet cathode humidification Dead-end or flow- through mode Model Numerical Mass transport

7 Pseudo 2D T constant ΔPan/cat = 0 Liquid water in the membrane and vapor in the electrodes Membrane GDL Anode Cathode Gas Channel GDL Gas Channel Dead-end or flow- through mode x z Presentation Results Assumption Optimal RH Strategies Outline Mass transport model Conclusion Presented work IRH project Model Numerical Mass transport Dynamic

8 GDL Gas Channel x z Presentation Results Assumption Optimal RH Strategies Outline Gas channel model Convection Bulk motion Mass balance Pressure drop Flux in x direction Dead end mode Conclusion Presented work IRH project Model Numerical Mass transport Convection Bulk motion

9 Presentation Results Assumption Optimal RH Strategies Outline GDL model Diffusion Bulk motion Continuity equation Flux in x direction GDL Gas Channel x z Membrane Diffusion Bulk motion Conclusion Presented work IRH project Model Numerical Mass transport

10 Presentation Results Assumption Optimal RH Strategies Outline Membrane model Diffusion Continuity equation Flux in x direction Membrane GDL x z Diffusion Electro-osmotic GDL Conclusion Presented work IRH project Model Numerical Mass transport

11 Module GDL Module Canal Module Potentiel Module GDL Module Canal Anode Cathode Module Membrane Presentation Model Results Numerical Assumption Optimal RH Strategies Outline Mass transport Numerical model Module X Coded in C Transfer variables Fuel cell model in Simulink (Schematic) Conclusion Presented work IRH project

12 Gas Channel Water production Liquid water Local current density z direction (along gas channel) Under-humidified Over-humidified Well-humidified 3 humidification cases: Presentation Results Assumption Optimal RH Strategies Outline The optimal internal humidification Liquid water appearance at the center of the cell along channel direction optimal internal cell humidification Cathode inlet z (compromise between drying at the inlet and flooding at the outlet) Conclusion Presented work IRH project Model Numerical Mass transport

13 Whatever the load, an optimal exists Drying Flooding Presentation Results Assumption Optimal RH Strategies Outline Optimal inlet RH (dead-end mode) Anode humidification has little influence SR O2 = 2 T = 60°C P tot = kPa No anode humidification required Important results for control Conclusion Presented work IRH project Model Numerical Mass transport

14 N diff N osmo N tot Presentation Results Assumption Optimal RH Strategies Outline Optimal inlet RH (dead-end mode) Why the anode inlet humidification has little influence in dead-end mode ? N 1 atm & 60°C Conclusion Presented work Negligible effects of the anode inlet humidification Steady state IRH project Model Numerical Mass transport CathodeAnode Water content in the cell Cell thickness

15 Presentation Results Assumption Optimal RH Strategies Outline Optimal inlet RH (flow-through mode) SR O2 & SR H2 = 2 T = 60°C P tot = kPa Drying Flooding Whatever the load, an optimal exists More anode humidification influence Conclusion Presented work IRH project Model Numerical Mass transport

16 4 optimum strategies : Presentation Results Assumption Optimal RH Strategies Outline Discussion on humidification strategies Water content in the membrane x-coordinate ) H2 flow-through mode & 2) H2 dead-end mode & 4) H2 flow-through mode & 3) H2 dead-end mode & SR O2 = 2; SR H2 = 0 or 2 T = 60°C; P tot = kPa Conclusion Presented work IRH project Model Numerical Mass transport Very close profiles (thin membrane) Same performances Use the simplest case 3

17 Presentation Results Assumption Optimal RH Strategies ConclusionConclusion Conclusion Outline A dynamic pseudo 2D model of a PEMFC has been developed The optimal inlet cathode relative humidity has been computed for different cases (with or without anode humidification and dead-end or flow-through H2 mode) Results show that an humidification strategy without humidifying the anode in a H2 dead-end configuration can be used with almost the same performances than a case with anode humidification Better humidification mechanisms understanding has been obtained Presented work IRH project Model Numerical Mass transport The different cases have been compared

18 Presentation Results Assumption Optimal RH Strategies Future work & Control approach Conclusion Outline Modeling of liquid water transport in the electrodes and modeling of the auxiliaries Computing of the PEMFC system efficiency for any given load and operating parameters Effect of liquid water on the cell voltage Effect of auxiliaries energy consumption on the output net power Off-line establishment of the optimal operating parameters Development of an on-line control algorithm to transient regimes between optimal cases Optimal real-time control Better efficiencies of the FCS Control box for commercial uses Experimental validation!!! Presented work IRH project Model Numerical Mass transport

19 Presentation Results Assumption Optimal RH Strategies AcknowledgementsAcknowledgements Conclusion Outline This work has been supported by: –Hydro-Québec –Natural Resources Canada –Natural Sciences and Engineering Research Council of Canada. We also acknowledge the advices of Michel Dostie from the LTE Hydro-Québec and of Jean Hamelin from the HRI. Presented work IRH project Model Numerical Mass transport