Modelling And Experimental Study On Output Characterictcs Of Fuel Cell

Energy demand and environmental pollution have become the two major problems to which societies are seeking immediate remedies. Two products, Proton Exchange Membrane Fuel Cell (PEMFC) and Vanadium Redox Flow Battery (VRB), are possible solutions to the aforementioned problems as both devices are environmentally friendly and possess high energy conversion efficiency. However, the performances of both PEMFC and VRB are nonlinear and subjected to coupling and hysteresis effects, thus hindering large scale commercialization of the two products. It is therefore necessary to focus research work on the characteristics of the output from the PEMFC and VRB in order to maximize the performances, so as to improve commercialization of these products for the betterment of societies.The thesis first introduces the structure and characteristics of PEMFC and extends in-depth analysis to the output of PEMFC based on electro-chemical thermodynamics as well as electrode kinetics. Next, the influence of heat and water balance management on the performance of the PEMFC is discussed. Subsequently, the working principles and characteristics of VRB is analyzed.Modeling and simulation of the PEMFC and VRB are crucial to further analyze and optimize the performances and apply corresponding control strategies. Based on PEMFC mechanisms, models of electrical output, thermodynamics and gas distribution are built for the dynamic behavior of a PEMFC single cell. Thereupon, such dynamic behavior of the PEMFC under condition of varying electrical load is simulated through Matlab/Simulink. Similar simulations are performed on single cell VRB based on models of open circuit voltage, Ohmic internal resistance as well as over-voltage. The simulations for VRB are intended to simulate stability characteristics of the single cell under different electrolyte flow rates.Problem of over-consumption by pump energy in driving electrolyte movements exist in current VRB systems. This thesis hence proposes the solution of controlling VRB electrolyte flow in pulsating operation. Under different pulse cycle and electrolyte flow rates, the VRB is subsequently charged and discharged under constant current mode. Based on analysis on charging and discharging curves of the VRB, pump energy consumption, single cell energy efficiency as well as predicted system efficiency, the aforementioned control strategy has increased system level efficiency of the VRB.Finally, the thesis analyzes the influence of multiple channel air-cooling strategy on heat dissipation effect of an laboratory made open cathode PEMFC. The experiment set up uses 3D printed parts assemblies, designed with SolidWorks, to allow air flow from multiple channels of different opening lengths. Analysis on the performance of the PEMFC is then carried out under varying fan voltages. Results have shown that multiple channel air cooling has increased the uniformity of air flow through the PEMFC and to a certain extent, increased the working efficiency of the PEMFC.The concluding part summarized the works of the thesis, pointed out the shortcomings and suggested areas for improvement and further researches.