Experimental Study of a Hydrogen Fuel Cell

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Transcript Experimental Study of a Hydrogen Fuel Cell

Xu Yang, Linfeng Zhang
Renewable Energy Research Laboratory
Department of Electrical Engineering
University of Bridgeport, Bridgeport, CT, 06604
INTRODUCTION
Electrolyzer is a promising device in
hydrogen generating technology, and fuel cell
has been deemed to be highly efficient and
environmentally benign technology for
energy conversion. Therefore, finding out the
characteristics of the hydrogen energy system
is very important for the renewable energy
investigation. For this purpose, we
established a fuel cell system to gather the
important data and compare the experimental
result with theoretical values. We focused on
the impedance spectrum and V-I curve
analysis of PEM fuel cell . Through this
study, we found that there is no significant
different between the simulation and
experimental result.
EXPERIMENTAL SETUP
There are two experiments: one is for the V-I
curve measurement and the other one is for
electrochemical spectrum test.
All the experiments are based on a PEM fuel
cell system as shown in fig.1. The
electrolyzer splits water into hydrogen and
oxygen which are supplied to fuel cell to
generate electricity.
In the fig.2 and fig.3, DC-power supply is the
power source of electrolyzer; multimeter is
used to monitor the Voltage curve while the
external load is changed. The Hp LCZ meter
is used to record the impedance spectrum
Figure 6 Voltage transient curve
while the frequency is changed.
In fig.6, it is obvious that there is a significant
voltage drop and transient at 1400s even
though the load is not changed. This
phenomenon is caused by the ohmic loss
which is in direct proportion to current.
Figure 4 The model of fuel cell
A LabVIEW program is developed to
simulate a PEM fuel cell according to the
model shown in fig.4. Therefore, the voltage
can be calculated with different temperature,
gas pressure and current.
RESULTS & DISCUSSION
Figure 1 A fuel cell system
Figure 2 The setup for V-I curve
measurement
Figure 3 The setup for impedance spectrum
testing
Figure 7 Impedance spectrum
From fig.7, the impedance with a symmetric
oxygen supply is higher than that with a
symmetric hydrogen supply. It indicates that
the cell impedance is determined by the
cathode impedance within a specific
frequency range, In fact, besides the cathode
and anode impedance, the membrane has a
big impact on the PEM fuel cell impedance
while in the high frequency range. This
Figure 5 V-I curve
phenomenon was not observed in above
For the experiment result, open circuit experiment due to the restrictions of the
voltages(OCV) are 0.944V. Experiment was experimental setup.
performed at room temperature and the
pressure of the reaction gas was 1 atm.
ACKNOWLEDGE
Simulation result was obtained through the
The present study was supported by the
o
LabVIEW program at 70F and 1 atm.
Department of Energy through grant no.
From fig.5, there is a significant difference
DEOE0000427
between the V-I curves with different oxygen
concentration. Therefore, the higher oxygen
concentration the more electricity which CONCLUSION
PEM fuel cell can generate. Compare the This work has presented a modeling of a
simulation result and the pure oxygen curve, proton exchange membrane fuel cell.
the difference of OCV is 0.2V. This Impedance spectrum and V-I curves are
difference is because that in the simulation completely discussed. Through study of this
model, we did not consider about internal work, it is very useful for building a PEM fuel
current which definitely affect on OCV while cell modeling to perform researches in the
at low temperature. The abrupt change of hydrogen energy investigation. However, this
pure oxygen slope at 0.2A is caused by work just based on elementary design, to
overvoltage which as a result of water make it preciseness, much more experiment
and works would be needed.
diffusion.