Multi-scale Modeling and Optimization of PEM Fuel Cells

Inhaltsverzeichnis (Table of Contents)

• Abstract
• Chapter 1: Introduction to PEM Fuel Cells
• Chapter 2: Direct Methanol Fuel Cell (DMFC) Modeling and Optimization
• Model Development and Parameter Identification
• Sensitivity Analysis and Optimal Feed Concentration
• Dynamic Optimization and Constant Feeding Strategy
• Chapter 3: Hydrogen PEM Fuel Cell (H2 PEMFC) Modeling and Optimization
• One-Dimensional Model and Transport Phenomena
• CO Poisoning Effect and Fuel Utilization
• O2 Bleeding and Optimization
• Chapter 4: Macro-Scale Modeling of H2 PEMFC Power Generation System
• System Simulation and Optimization
• Case Study and Heat Integration
• Chapter 5: Micro-Scale Modeling of PEM Transport Phenomena
• Monte Carlo Simulation and Polymer Structure
• Molecular Dynamics Simulation and Proton Diffusion
• Water Uptake and Material Design
• Acknowledgments

Zielsetzung und Themenschwerpunkte (Objectives and Key Themes)

This dissertation aims to develop multi-scale models for Polymer Electrolyte Membrane Fuel Cells (PEMFCs), encompassing direct methanol fuel cells (DMFCs) and hydrogen PEMFCs (H2 PEMFCs), and to optimize their performance. The research integrates modeling across micro, meso, and macro scales to achieve enhanced efficiency and profitability. * Multi-scale modeling of DMFCs and H2 PEMFCs * Optimization of fuel cell performance through parameter tuning and operational strategies * Analysis of CO poisoning effects in H2 PEMFCs and mitigation strategies * Macro-scale system optimization of H2 PEMFC power generation systems, including heat integration * Micro-scale investigation of PEM transport phenomena using molecular simulations

Zusammenfassung der Kapitel (Chapter Summaries)

Chapter 2: Direct Methanol Fuel Cell (DMFC) Modeling and Optimization: This chapter presents a DMFC model incorporating electrode kinetics and methanol crossover. Key parameters are identified, and a relationship between methanol feed concentration and power density is established. Sensitivity analysis reveals an optimal feed concentration maximizing power density at a given current density. Dynamic optimization of the system further refines the optimal feed strategy for consistent high power output under specified conditions. The significance lies in the ability to optimize DMFC performance by manipulating feed concentration and incorporating dynamic control strategies. Chapter 3: Hydrogen PEM Fuel Cell (H2 PEMFC) Modeling and Optimization: A one-dimensional model is used to analyze transport phenomena in the anode backing and catalyst layer of an H2 PEMFC, while a standard curve describes the cathode response. The model focuses on the "CO poisoning" effect at the anode and the impact of hydrogen dilution. A detailed kinetic model quantifies voltage losses due to CO, revealing a significant amplification of these losses with diluted hydrogen feeds, particularly under high fuel utilization. The incorporation of O2 bleeding into the model, coupled with optimization, identifies optimal O2 concentrations to maximize current density at given cell voltages, even with 100 ppm CO. This chapter demonstrates a comprehensive approach to understanding and mitigating CO poisoning, a significant challenge in H2 PEMFC technology. Chapter 4: Macro-Scale Modeling of H2 PEMFC Power Generation System: This chapter models a complete H2 PEMFC power generation system including fuel reforming, the fuel cell stack, and post-combustion. The integrated model is optimized to maximize energy and system efficiency, and system profit. A case study focusing on H2 production examines the influence of CH4 and H2O inlet flow rates and temperature on system performance. The inclusion of heat integration strategies results in a significant increase in efficiency (6.7%) and profitability (29.2%), highlighting the importance of optimal process design for fuel cell-based power generation. This model offers a practical strategy for integrating fuel cells into larger energy systems. Chapter 5: Micro-Scale Modeling of PEM Transport Phenomena: This chapter employs molecular modeling techniques to investigate PEM transport at a microscopic level. Monte Carlo simulations characterize the Nafion polymer structure, while molecular dynamics simulations link this structure to proton diffusion within the PEM. The impact of water uptake on proton transfer is also explored, providing insights for the design of improved PEM materials. This micro-scale analysis provides a fundamental understanding of the processes determining PEM performance, guiding the development of next-generation materials.

Schlüsselwörter (Keywords)

PEM Fuel Cells, DMFC, H2 PEMFC, Multi-scale Modeling, Optimization, CO Poisoning, Fuel Utilization, Heat Integration, Methanol Crossover, Proton Diffusion, Molecular Simulation, System Efficiency, Power Density, Electrode Kinetics.

Häufig gestellte Fragen

What is the main focus of this language preview concerning PEM Fuel Cells?

This language preview provides a comprehensive overview of a dissertation focusing on multi-scale modeling and optimization of Polymer Electrolyte Membrane Fuel Cells (PEMFCs), including both direct methanol fuel cells (DMFCs) and hydrogen PEMFCs (H2 PEMFCs). It includes the table of contents, objectives, key themes, chapter summaries, and keywords of the dissertation.

What are the key themes explored in the dissertation?

The key themes include multi-scale modeling of DMFCs and H2 PEMFCs, optimization of fuel cell performance through parameter tuning and operational strategies, analysis of CO poisoning effects in H2 PEMFCs and mitigation strategies, macro-scale system optimization of H2 PEMFC power generation systems (including heat integration), and micro-scale investigation of PEM transport phenomena using molecular simulations.

Can you summarize the content of Chapter 2 regarding DMFC Modeling and Optimization?

Chapter 2 presents a DMFC model incorporating electrode kinetics and methanol crossover. It identifies key parameters and establishes a relationship between methanol feed concentration and power density. Sensitivity analysis determines an optimal feed concentration for maximizing power density. Dynamic optimization refines the feed strategy for high power output under specific conditions.

What is the focus of Chapter 3 regarding Hydrogen PEM Fuel Cell Modeling and Optimization?

Chapter 3 utilizes a one-dimensional model to analyze transport phenomena in the anode of an H2 PEMFC, specifically focusing on the "CO poisoning" effect and the impact of hydrogen dilution. It quantifies voltage losses due to CO and explores O2 bleeding as a mitigation strategy to maximize current density, even with CO present.

What does Chapter 4 cover concerning Macro-Scale Modeling of an H2 PEMFC Power Generation System?

Chapter 4 models a complete H2 PEMFC power generation system, including fuel reforming, the fuel cell stack, and post-combustion. The integrated model is optimized to maximize energy efficiency, system efficiency and system profit. A case study examining H2 production demonstrates the impact of CH4 and H2O inlet flow rates and temperature. It also showcases the benefits of heat integration in increasing efficiency and profitability.

What is the focus of Chapter 5 regarding Micro-Scale Modeling of PEM Transport Phenomena?

Chapter 5 employs molecular modeling techniques to investigate PEM transport at a microscopic level. Monte Carlo simulations characterize the Nafion polymer structure, while molecular dynamics simulations link this structure to proton diffusion within the PEM. The impact of water uptake on proton transfer is also explored, providing insights for the design of improved PEM materials.

What are some of the keywords associated with this research?

The keywords include PEM Fuel Cells, DMFC, H2 PEMFC, Multi-scale Modeling, Optimization, CO Poisoning, Fuel Utilization, Heat Integration, Methanol Crossover, Proton Diffusion, Molecular Simulation, System Efficiency, Power Density, and Electrode Kinetics.