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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.