COMSOL Multiphysics application in modeling PEMFC transients

Transcription

1 2010 Comsol Conference Presented at the COMSOL Conference 2010 China COMSOL Multiphysics application in modeling PEMFC transients Li Xiaojin (Associate Professor) Dalian Institute of Chemical Physics, Chinese Academy of Science Shanghai 26th, October,

2 Main content Principle of PEMFC and transient characteristics Study on PEMFC transient characteristics Develop the PEMFC transient model Air stoichiometry change on PEMFC transient Water transport on PEMFC transient Modeling high temperature PEMFC Conclusion 2

3 Principle of PEMFC & application Advantages High efficiency Environment friendly High power density Fast startup PEMFC Anode: H 2 2H + + 2e - Cathode: 1/2 O 2 + 2H + +2e - H 2 O 3

4 Bottleneck of FC technology Commercialization System stability & reliability Transient characteristics System cost Environment adaptability 4

5 Water transport in FC FC water transport principle Experiment observation 5

6 Model assumptions 1. The gravity effect is neglected ; 2. The gas mixture is an incompressible ideal gas; 3. The flow in the gas channel is laminar; 4. The diffusion layer, catalyst layer and membrane are isotropic and homogeneous, and the membrane is impermeable to gas species; 5. The contact resistance between any two parts in the fuel cell is neglected; 6. The dissolved reactive gas in electrolyte phase of catalyst layer is neglected; 7. It is considered that water exits in the gas phase at the electrodes as well as in the liquid phase within the membrane. In channels, existence of liquid water is in a small volume fraction and in finely dispersed droplets so that it dose not affect the gas flow. 6

7 Main content Principle of PEMFC and transient characteristics Study on PEMFC transient characteristics Develop the PEMFC transient model Air stoichiometry change on PEMFC transient Water transport on PEMFC transient Modeling high temperature PEMFC Conclusion 7

8 Procedures Assumptions Geometry Parameters Governing Equation Boundary Conditions Solver COMSOL Multiphysics Result Analysis Postprocess 8

9 Model equations Continuity: Momentum: Species: Water in membrane: Energy: Electron: Proton: 1 2 u Sm eff D C u C S i v g i i S eff e e e S uu p S u ni d ( Dwcw) 0 F cpu T ( k ft ) S T eff m m m 9

10 Source term for model equations 10

11 Model geometry & mesh y x Model geometry:1anode flow channel, 2anode gas diffusion layer, 3anode catalyst layer, 4membrane, 5 Cathode catalyst layer, 6 Cathode gas diffusion layer, 7 Cathode flow channel Comsol Multiphysics

12 Main content Principle of PEMFC and transient characteristics Study on PEMFC transient characteristics Develop the PEMFC transient model Air stoichiometry change on PEMFC transient Water transport on PEMFC transient Modeling high temperature PEMFC Conclusion 12

13 PEMFC transient model Mass conservation t u Sm Momentum conservation Model geometry:1anode flow channel, 2anode gas diffusion layer, 3membrane, 4Cathode gas diffusion layer, 5 Cathode flow channel 1 u 1 t uu p S u Species conservation c t k eff uc k Dk ck Sk Cell potential: Vcell Eact ohm conc 13

14 Model validation stoichiometry 1.3 to 2.5 model stoichiometry 1.3 to 2.5 experiment Voltage/V Time/s Comparison between model and experimental cell voltage evolution Q. Shen, M. Hou, et. al J. Power Sources. 2008, 179:

15 Air stoichiometry change on PEMFC transient 阴极计量比的变化速率 Cathode stoichiometry A1 stoichiometry A2 stoichiometry A3(base case) stoichiometry averge current density time, s Averge current density, A/m 2 Cell Potential, V V time, s 0.65V 0.64V A1 A2 A3 Qu Shuguo, Li Xiaojin, etc., J Power Sources 185 (2008),

16 Reactant starvation under different conditions A1 A2 A3 16

17 Main content Principle of PEMFC and transient characteristics Study on PEMFC transient characteristics Develop the PEMFC transient model Air stoichiometry change on PEMFC transient Water transport on PEMFC transient Modeling high temperature PEMFC Conclusion 17

18 Experiment study on water dynamic transport Aim:Study water transport in fuel cell under different humidity on cell potential and as model validation Conditions: Current:step from 0.05 to 空气入口 开关阀 稳压阀 针型调节阀 流量计 压力表 罐空气增湿 压力表 罐氢气增湿 流量计 稳压阀 氢气入口 开关阀 针型调节阀 2.5A Air flow:parabolic pattern ml/min Hydrogen flow:fixed Humidity:100% 62% 流量计 空气出口 分水器 5cm 2 燃料电池 电子负载 程序控制 工作站 分水器 流量计 氢气出口 18

19 Average current density & cathode inlet velocity change 19

20 Experiment results For same relative humidity, the lower the change rate, the greater the cell potential undershoots. For different relative humidity, the magnitude of cell potential undershoots increased as the relative humidity decreased The steady state cell potential also decreased as the relative humidity was decreasing 20

21 Model geometry Model geometry:1anode flow channel, 2anode gas diffusion layer, 3membrane, 4Cathode gas diffusion layer, 5 Cathode flow channel Continuity Momentum Species Water in membrane Electrons Protons 1 u 1 t t t u g g g m eff eff C D C u C S i i v g i i cw ndi m ( Dw cw) 0 t F S uu p S u eff e e e S S eff m m m Comsol Multiphysics 3.5 求解 21

22 Model validation 22

23 Water content change at membrane/electrode interface RH=100% water content at membrane/electrode interface RH=62%water content at membrane/electrode interface Qu Shuguo, Li Xiaojin, etc.,j Power Sources 195 (2010),

24 Main content Principle of PEMFC and transient characteristics Study on PEMFC transient characteristics Develop the PEMFC transient model Air stoichiometry change on PEMFC transient Water transport on PEMFC transient Modeling high temperature PEMFC Conclusion 24

25 2-D nonisothermal HT-PEMFC model Continuity: u Sm Momentum: Species: 1 2 uu p S u eff D C u C S i v g i i 3 5 Water in membrane: ni d ( Dwcw) 0 F y x Model geometry:1anode flow channel, 2anode gas diffusion layer, 3anode catalyst layer, 4membrane, 5 Cathode catalyst layer, 6 Cathode gas diffusion layer, 7 Cathode flow channel Energy: Electron: Proton: cpu T ( k ft ) S T S eff e e e S eff m m m 25

26 Species distribution in HT-PEMFC 26

27 Temperature distribution in HT-PEMFC 27

28 Potential distribution in electrode and membrane Cathode electrode potential Anode electrode potential Membrane potential 28

29 Main content Principle of PEMFC and transient characteristics Study on PEMFC transient characteristics Develop the PEMFC transient model Air stoichiometry change on PEMFC transient Water transport on PEMFC transient Modeling high temperature PEMFC Conclusion 29

30 Conclusion Modeled fuel cell transient characteristics using COMSOL Multiphysics and the model result validated by experiment; Carried out fuel cell dynamic simulation using Comsol and closer to real operation conditions; Studied the effect of reactant transport and membrane water transport on the PEMFC cell potential under transient air flow and load change using COMSOL Multiphysics; Modeled the high temperature PEMFC based on Nafion/SiO2 composite membrane using COMSOL Multiphysics. 30

31 Thank You! 31