Dynamic Load and Temperature Behavior of a PEFC-Hybrid-System

[+] Author and Article Information
C. Graf, K. A. Friedrich

German Aerospace Center e. V., Institute of Technical Thermodynamics, 70569 Stuttgart, Germany

A. Vath, N. Nicoloso

TU Darmstadt, Institute of Electrical Power Systems, 64283 Darmstadt, Germany

J. Fuel Cell Sci. Technol 3(4), 403-409 (Apr 05, 2006) (7 pages) doi:10.1115/1.2349520 History: Received November 30, 2005; Revised April 05, 2006

A dynamic model of a polymer electrolyte fuel cell hybrid system has been developed within MATLAB -SIMULINK . Components are modeled using electrochemical and mass transport as well as heat transfer equations. The implemented equations describe the steady-state as well as the dynamic operation of the system with sufficient accuracy, although considerable simplifications have been made for the stack and the peripheral components to keep model complexity and computing time low. Emphasis is given to the operation limits of the PEFC system, notably the conditions for trouble-free operation at different loads and high or low ambient temperature. The potential of the simulation as system optimization tool and efficient operation guide are demonstrated. Model validation was accomplished by experiments on a homemade 150W portable system including a Ni-MH accumulator for 300W peak power output.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 7

Dynamic temperature characteristics of stack and metal hydride cartridges at an ambient air temperature of 20∘C and varying current

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Figure 14

Varying fuel cell system efficiency with current and constant hybrid system efficiency as fuel cell is only operating in this set up in a range between 35% and 45%

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Figure 15

(a) Temperature of stack and cartridge for dynamic current at 40∘C without compressor control. (b) Temperature for system with compressor control. (c) Temperature for hybrid system with compressor control at 20% higher current.

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Figure 1

Model of H2 PEFC hybrid system including auxiliary components

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Figure 2

Modeled layers in terms of PEFC

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Figure 3

Characteristic of a 9AhNiMH accumulator; (a) Discharging (b) charging

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Figure 4

Air supply as a function of compressor voltage and pre set pressure

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Figure 5

Experimental system configuration with temperature measurement positions in the set-up used for model validation

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Figure 6

Dynamic behavior of PEFC voltage for given current steps

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Figure 10

Comparison of stack and accumulator voltage for different currents

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Figure 11

Transient characteristic of fuel cell system current in dependency of load current for a hybrid system. In charging state fuel cell current is higher than load current.

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Figure 12

Accumulator state of charge for varying load current. Positive sign during charging mode and negative while discharging.

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Figure 13

Accumulator voltage, fuel cell system, and load current of PEFC hybrid system

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Figure 8

Efficiency of fuel cell stack for fixed compressor supply voltages and optimized curve for correlation of stack current with supply voltage of compressor

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Figure 9

Correlation of load current with supply voltage for compressor



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