DYNAMIC BEHAVIORAL

MODEL OF A PEM FUEL CELL

- Alexis Kwasinski

EE394J-10 Distributed Generation Technologies

Final Presentation

Introduction

•Goals:

- Develop a Dynamic Behavioral Model of

a PEM Fuel cell.

•Characteristics

- Model studies the response of the fuel cell when the electrical load changes.

- Model represents the result of the physical process rather than the process itself.

- Simulations are an inexpensive and insightful tool to study complex systems.

Introduction

• Literature review:

[1] “Fuel Cell Technology Handbook,” ed. By G. Hoogers, CRC Press LLC, Boca raton , Florida, 2003.

[2] J.C. Amphlet, R. F. Mann, B. A. Peppley, P. R. Roberge, and A. Rodrigues, “A practical PEM fuel cell model for simulating vehicle power sources,” in Proc. Of Tenth Annual Battery Conference on Applications and Advances, pp. 221-226, jan. 1995.

[5] J. T. Pukrushpan, H. Peng and A. G. Stefanopoulou, “Simulation and analysis of transient fuel cell system performance based on a dynamic reactant flow model,” in Proc. 2002 ASME International Mechanical Engineering Congress and Exposition, pp. 1- 12, Nov 2002.

[7] P. Famouri, and R. S. Gemmen, “Electrochemical circuit model of a PEM fuel cell,” in Proc. 2003 IEEE Power Engineering Society General Meeting, vol. 3, pp. 13-17, July 2003.

Physical Model - Equations

Ec = Er – vact – vohm – vconc

2 2

3 5 11.229 0.85 10 ( 298.15) 4.3085 10 ln( ) ln( )

2r H a O cE T T p p

0

0.069logact

iv

i

ohm ohmv iR

3

2max

c

conc

iv i c

i

0

0.069( ) logact

iR i

i i

3

2max

( )c

conc

iR i c

i

2

2 2( )

2H a

H a H a outa

dp RT iQ U A

dt V F

2

2 2( )

4O c

O c O c outc

dp RT iQ U A

dt V F

2

2 2

H hinH h outH h

h

dp RTQ Q

dt V

2

2 2

O hinO h outO h

h

dp RTQ Q

dt V

2cc c mc c c

dT J T K

dt

2pp p mp p p

dT J T K

dt

Q Ar

Physical Model

Behavioral Model - Equations

FACT: The time constants of the pump and compressor, are much larger than the time constant of the cathode and anode.

-Only system’s dynamic equations:

2

2 0

1H aH a

dpp p

dt

2

2 0

1O cO c

dpp p

dt

τ is the pump and compressor time constant ~ 1 sec.

Behavioral Model

Simulation Results

Fuel Cell Current

Fuel Cell Output Voltage

Output Power

Simulation: Sudden load increase (2x). Objective V = constant

Conclusion

•A simple dynamic behavioral model was developed.

•The model agrees with known fuel cell behavior.

•A sudden load increase leads to:-Current increases with a time constant of 1 sec.-Voltage has a sudden drop to 50% value.-Power has a sudden drop and then increases with

a time constant of 1 sec.

•The described behavior indicate potential problems in automotive and stationary applications. Solution: use batteries.