Title Page
Abstract (Korean)
Abstract
Contents
Nomenclature 22
Chapter 1. Introduction 34
1.1. Hydrogen based electrochemical system 34
1.2. Polymer Electrolyte Membrane Fuel cells 35
1.2.1. PEMFC under malfunctions: A Literature Review 37
1.3. H₂ Br₂ Redox Flow batteries 40
1.3.1. Performance and transport mechanisms in H₂ /Br₂ RFBs: A Literature Survey 42
1.3.2. Performance improvement and safety challenge solutions for handling toxic Bromine/Bromide solutions: A Literature survey 46
1.4. Motivation and objective of dissertation 50
Chapter 2. Modeling Methodology 54
2.1. PEMFC model 56
2.1.1. Model Assumptions 57
2.1.2. Electrochemical thermodynamics (Macro-scale model) 57
2.1.3. Micro-scale CL model 64
2.1.4. Gas crossover model 67
2.2. H₂/Br₂ RFB model 69
2.2.1. Model Assumptions 69
2.2.2. Electrochemical thermodynamics 70
2.2.3. Bromine/bromide crossover model 74
2.2.4. Kinetic model for the bromate-bromide reaction 75
2.2.5. Water uptake of PFSA membranes equilibrated with Br₂/HBr Electrolyte 77
Chapter 3. Analyzing the characteristics of temperature rise and coolant flow rate control during malfunction of PEM fuel cell 80
3.1. Introduction 80
3.2. Model implementation and boundary conditions 82
3.3. Results and Discussion 86
3.4. Conclusion 101
Chapter 4. Water transport and its impact on the performance of hydrogen bromine redox flow batteries 103
4.1. Introduction 103
4.2. Model implementation and boundary conditions 105
4.3. Results and Discussion 108
4.4. Conclusion 121
Chapter 5. Performance enhancement of hydrogen/bromine flow batteries using bromate-based electrolyte 122
5.1. Introduction 122
5.2. Model implementation and boundary conditions 123
5.3. Results and Discussion 128
5.4. Conclusion 138
Chapter 6. Conclusion and Future Works 139
Conclusion 139
Future works 143
Bibliography 144
Table 1. PEMFC model 58
Table 2. [제목없음] 71
Table 3. Kinetic, transport, and physiochemical properties of PEMFC. 83
Table 4. Cell geometry and operating conditions of PEMFC. 86
Table 5. Malfunction simulation cases and their effects on cell voltage, Vcell and coolant flow rate, φ cool at 0.3 A cm⁻² operating condition.[이미지참조] 88
Table 6. Energy balance summary under different malfunction cases in PEMFC. 98
Table 7. Physio-chemical, kinetics, and transport properties. 106
Table 8. Cell geometry and boundary conditions of H2/Br2 RFB. 107
Table 9. Kinetic parameters, transport, and physiochemical properties for an H₂/Br₂/BrO₃⁻ RFB model. 124
Table 10. Cell geometry and operating conditions of H₂/Br₂ RFB. 126
Figure 1. Schematic representation of a PEM fuel cell 36
Figure 2. Schematic of H₂/Br₂ Redox Flow Battery system operation 41
Figure 3. Illustration of the multiscale computational domains and simulation processes, including the microscale CL model. 56
Figure 4. Illustration of the microscale model for oxygen transport through the ionomer and liquid films on a spherical agglomerate in the cathode CL, showing... 64
Figure 5. Effects of current density on (a) coolant flow rate and (b) MEA temperature rise (△Te)[이미지참조] 89
Figure 6. Effects of malfunctions on (a) coolant flow rate, (b) MEA temperature rise (△Te), and (c) coolant flow rate and cell voltage relationship.[이미지참조] 91
Figure 7. The effect of coolant flow rate on cell voltage. 92
Figure 8. Local current density, MEA maximum temperature, and coolant temperature distributions along cell flow direction for (a) Ref. case, (b) Case 1... 94
Figure 9. Hydrogen and oxygen distributions on (a) anode and (b) cathode sides 97
Figure 10. Effect of different malfunction conditions on cell voltages and individual voltage components. 100
Figure 11. Computational domain and mesh configuration of a single straight channel H₂/Br₂ RFB cell. 108
Figure 12. Comparison of simulation results (lines) and experimental data (symbols) measured by Tucker et. al., [84]: (a) Polarization curves and (b)... 110
Figure 13. Liquid saturation, s, in hydrogen CL at different current densities: (a) charge and (b) discharge. SOC=97% (0.9M Br₂/1.0M HBr). 112
Figure 14. HBr concentration in hydrogen CL at different current densities during (a) charge and (b) discharge at 97% SOC (0.9M Br₂/1.0M HBr). 114
Figure 15. (a) Polarization behaviors and HBr concentration in hydrogen CL by single-phase and two-phase models during (b) charge and (c) discharge at... 115
Figure 16. Comparison of single-phase and two-phase model prediction for the HBr accumulation and its distribution pattern. 118
Figure 17. Overpotential breakdown of the single-phase and two-phase simulations at various current densities (SOC 97%) during (a) charge mode... 120
Figure 18. Schematic of an H₂/Br₂/BrO₃⁻ RFB system. 125
Figure 19. Computation domain and mesh configuration of an H₂/Br₂/BrO₃⁻ RFB cell. 128
Figure 20. Comparison of discharge voltage evolution curves calculated by the model (line) and experimental data (symbols) measured by Cho and Razaulla... 129
Figure 21. Changes in the concentrations of Br₂, Br⁻ and BrO₃⁻ during discharge at different rates: (a) 1C and (b) 2C. 131
Figure 22. Overpotential breakdown of voltage curves at (a) 1C discharge rate and (b) 2C discharge rate. 132
Figure 23. Concentration contours of Br2 and Br-at the interface between the electrode and the membrane for two cases: (a) without BrO3-chemical reaction... 133
Figure 24. Overpotentials with and without BrO₃⁻ at 1.0 A/cm² and ξb=2.5. The catholyte has 900 mol/m³ of Br₂ and 0.1 mol/m³ of Br⁻ at the inlet. The case with...[이미지참조] 134
Figure 25. Comparison for (a) Br₂ concentration, (b) Br⁻ concentration, with and without bromate chemical reaction at the discharge current density of 1.0 A/cm².... 135
Figure 26. Comparison for discharge voltage evolution curves with and without bromate chemical reaction at the discharge current density of 1.0... 136