Life cycle assessment shows that retrofitting coal-fired power plants with fuel cells will substantially reduce greenhouse gas emissions

1 - Proton exchange membrane fuel cells

This review discusses the history, fundamentals, and applications of different fuel cell technologies, including proton exchange membrane fuel cells (PEMFCs), direct methanol fuel cells, solid oxide fuel cells (SOFCs), phosphoric acid fuel cells (PAFCs), alkaline fuel cells (AFCs), and molten carbonate fuel cells (MCFCs). Recent advances in fuel cell technologies have led to potential applications in aerospace, transportation, and portable and stationary power generation due to high efficiency and low emissions. Fuel cell types are also compared based on efficiency, operating temperature, lifetime, energy/power density, and cost. It was noticed that PEMFCs have the highest mass power density, reaching 1,000 W/kg compared to less than 100 W/kg for SOFCs, which makes them suitable for portable applications such as aircraft. PEMFCs and AFCs are suitable for low‐temperature applications and are highly efficient. SOFCs and MCFCs are better for high‐temperature operations. SOFCs are robust and suitable for high‐power demands, while MCFCs are advantageous for high‐power output. Hydrogen fuel cells promise to decarbonize transportation and aviation sectors with the advantages of lower weight, compactness, and quick startup times. However, challenges remain around renewable hydrogen production/infrastructure and aircraft integration, besides hydrogen storage, water management inside fuel cells, and operational robustness under varying pressures. Generally, for all fuel cell types, more focus should be given to enhancing the stability and efficiency of fuel cell materials and reducing their cost.

Preface. Symbols. Acronyms and Abbreviations. PART I: INTRODUCTION. Introduction. Chapter 1: The Working Principle of a Fuel Cell. 1.1 Thermodynamic Aspects. 1.2 Schematic Layout of Fuel Cell Units. 1.3 Types of Fuel Cells. 1.4 Layout of a Real Fuel Cell: The Hydrogen-Oxygen Fuel Cell with Liquid Electrolyte. 1.5 Basic Parameters o Fuel Cells. Chapter 2: The Long History o Fuel Cells. 2.1 The Period Prior t 1894. 2.2 The Period from 1894 to 1960. 2.3 The Period from 1960 to the 1990s. 2.4 The Period after the 1990s. PART II: MAJOR TYPES OF FUEL CELLS. Chapter 3: Proton-Exchange Membrane Fuel Cells (PEMFC). 3.1 History of the PEMFC. 3.2 Standard PEMFC Version from the 1990s. 3.3 Special Features of PEMFC Operation. 3.4 Platinum Catalyst Poisoning By Traces of CO in the Hydrogen. 3.5 Commercial Activities in Relation to PEMFC. 3.6 Future Development of PEMFC. 3.7 Elevated-Temperature PEMFC (ET-PEMFC). Chapter 4: Direct Liquid Fuel Cells. Part A: Direct Methanol Fuel Cells. 4.1 Methanol as Fuel for Fuel Cells. 4.2 Current-Producing Reaction and Thermodynamic Parameters. 4.3 Anodic Oxidation of Methanol. 4.4 Milestones in DMFC Development. 4.5 Membrane Penetration by Methanol (Methanol Crossover). 4.6 Varieties of DMFCs. 4.7 Special Operating Features of DMFCs. 4.8 Practical Models of DMFCs and their Features. 4.9 Problems To Be Solved In Future DMFCs. Part B: Direct Liquid Fuel Cells. 4.10 The Problem of Replacing Methanol. 4.11 Fuel Cells Using Organic Liquids as Fuels. 4.12 Fuel Cells Using Inorganic Liquids as Fuels. Chapter 5: Phosphoric Acid Fuel Cells. 5.1 Early Work on Phosphoric Acid Fuel Cells. 5.2 Special Features of Aqueous Phosphoric Acid Solutions. 5.3 Construction of PAFCs. 5.4 Commercial Production of PAFCs. 5.5 Development of Large Stationary Power Plants. 5.6 The Future for PAFCs. 5.7 Importance of PAFCs for Fuel Cell Development. Chapter 6: Alkaline Fuel Cells. 6.1 Hydrogen-Oxygen AFCs. 6.2 Alkaline Hydrazine Fuel Cells. 6.3 Anion-Exchange (Hydroxyl Ion Conducting) Membranes. 6.4 Methanol Fuel Cells with Anion-Exchange Membranes. 6.5 Methanol Fuel Cell with an Invariant Alkaline Electrolyte. Chapter 7: Molten Carbonate Fuel Cells. 7.1 Special Features of High-Temperature Fuel Cells. 7.2 Structure of Hydrogen-Oxygen MCFCs. 7.3 MCFCs with Internal Fuel Reforming. 7.4 Development of MCFC Work. 7.5 The Lifetime of MCFCs. Chapter 8: Solid-Oxide Fuel Cells. 8.1 Schematic Design of Conventional SOFCs. 8.2 Tubular SOFCs. 8.3 Planar SOFCs. 8.4 Monolithic SOFCs. 8.5 Varieties of SOFCs. 8.6 Utilization of Natural Fuels in SOFCs. 8.7 Interim-Temperature SOFCs. 8.8 Low-Temperature SOFCs. 8.9 Factors Influencing the Lifetime of SOFCs. Chapter 9: Other Types of Fuel Cells. 9.1. Redox Flow Cells. 9.2 Biological Fuel Cells. 9.3 Semi-Fuel Cells. 9.4 Direct Carbon Fuel Cells. Chapter 10: Fuel Cells and Electrolysis Processes. 10.1 Water Electrolysis. 10.2 Chlor-Alkali Electrolysis. 10.3 Electrochemical Synthesis Reactions. PART III: INHERENT SCIENTIFIC AND ENGINEERING PROBLEMS. Chapter 11: Fuel Management. 11.1 Reforming of Natural Fuel. 11.2 Production of Hydrogen For Autonomous Power Plants. 11.3 Purification of Technical Hydrogen. 11.4 Hydrogen Transport and Storage. Chapter 12: Electrocatalysis. 12.1 Fundamentals of Electrocatalysis. 12.2 Putting Platinum Catalysts on the Electrodes. 12.3 Supports For Platinum Catalysts. 12.4 Platinum Alloys and Composites as Catalysts for Anodes. 12.5 Non Platinum Catalysts for Fuel Cell Anodes. 12.6 Electrocatalysis of the Oxygen Reduction Reaction. 12.7 The Stability of Electrocatalysts. Chapter 13: Membranes. 13.1 Fuel-Cell-Related Membrane Problems. 13.2 Work to Overcome Degradation of Nafion Membranes. 13.3 Modification of Nafion(r) Membranes. 13.4 Membranes Made From Polymers Without Fluorine. 13.5 Membranes Made from Other Materials. 13.6 Matrix-Type Membranes. 13 7 Membranes with Hydroxyl Ion Conduction . Chapter 14: Small Fuel Cells for Portable Devices. 14.1 Special Operating Features of Mini-Fuel Cells. 14.2 Flat Miniature-Fuel Batteries. 14.3 Silicon-Based Mini-Fuel Cells. 14.4 PCB-Based Mini-Fuel Cells. 14.5 Mini-Solid Oxide Fuel Cells. 14.6 The Problem of Air-Breathing Cathodes. 14.7 Prototypes of Power Units with Mini-Fuel Cells. 14.8 Concluding Remarks. Chapter 15: Mathematical Modeling of Fuel Cells (Felix N. Buchi). 15.1 Zero-Dimensional Models. 15.2 One-Dimensional Models. 15.3 Two Dimensional Models. 15.4 Three Dimensional Models. 15.5 Concluding Remarks . PART IV: COMMERCIALIZATION OF FUEL CELLS. Chapter 16: Applications. 16.1 Large Stationary Power Plants. 16.2 Small Stationary Power Units. 16.3 Fuel Cells for Transport Applications. 16.4 Portables. 16.5 Military Applications. Chapter 17: Fuel Cell Work In Various Countries. 17.1 Driving Forces for Fuel-Cell Work. 17.2 Fuel Cells and the Hydrogen Economy. 17.3 Activities in North America. 17.4 Activities in Europe. 17.5 Activities in Other Countries. 17.6 The Volume of Published Fuel-Cell Work. 17.7 Legislation and Standardization in the Field of Fuel Cells. Chapter 18: Outlook. 18.1 Periods of Alternating Hope and Disappointment Forever? 18.2 Some Misconceptions (Klaus Muller). 18.3 Ideal Fuel Cells. 18.4 Projected Future of Fuel Cells. General Bibliography. Author Index. Subject Index.

Fuel cells provide a sustainable and efficient power generation option, serving as an alternative to traditional energy systems dependent on fossil fuels. This research presents a detailed evaluation of prominent fuel cell technologies, including Polymer Electrolyte Membrane Fuel Cells (PEMFCs), Solid Oxide Fuel Cells (SOFCs), Alkaline Fuel Cells (AFCs), Phosphoric Acid Fuel Cells (PAFCs), Molten Carbonate Fuel Cells (MCFCs), Direct Methanol Fuel Cells (DMFCs), High-Temperature PEMFCs (HT-PEMFCs), and Direct Carbon Fuel Cells (DCFCs), for electricity generation using clean hydrogen as the primary fuel source. The evaluation focuses on key performance indicators such as efficiency, operating temperature, power density, fuel flexibility, and material requirements. The analysis reveals that PEMFCs exhibit superior overall performance, largely due to their efficient operation at lower temperatures, compact structure, and rapid startup, making them highly suitable for mobile and portable energy applications. While SOFCs offer excellent fuel flexibility and are well-suited for large-scale stationary applications, their high operating temperatures present material and longevity challenges. AFCs and PAFCs demonstrate moderate efficiencies and operational stability but are limited by CO₂ sensitivity and lower power densities. MCFCs and DCFCs deliver high efficiencies and carbon capture capabilities, yet their high-temperature operation results in material degradation. DMFCs, although compact and compatible with methanol, face performance limitations such as methanol crossover. Since different technologies excel in specific applications, PEMFCs are considered most suitable for large-scale integration into hydrogen-powered energy systems due to their well-balanced combination of performance, efficiency, and deployment potential.

Fuel cell technology is considered one of the most important solutions for clean energy, characterized by its high efficiency, minimal pollution, and adaptability across various sectors such as transportation, stationary energy, and portable electronics. Over the past two decades, significant progress has been made in materials science, system design, and cost optimization, enhancing the feasibility of commercialization. This paper follows the development of various types of fuel cells, including Proton Exchange Membrane Fuel Cells (PEMFC), Solid Oxide Fuel Cells (SOFC), Direct Methanol Fuel Cells (DMFC), Phosphoric Acid Fuel Cells (PAFC), Molten Carbonate Fuel Cells (MCFC), and Alkaline Fuel Cells (AFC), highlighting key innovations and market launches. The review emphasizes significant technical challenges, particularly concerning durability, catalyst degradation, and hydrogen infrastructure systems. Additionally, it outlines the existing state of fuel cell technology and proposes a strategy for integrating fuel cells into global low-carbon energy systems. From a decarbonization perspective, incorporating fuel cells into energy systems is crucial, as they not only provide high efficiency but also operate without emitting harmful pollutants. The article reviews advancements in fuel cell technology from 2020 to 2024, comparing performance metrics with market applications and obstacles to market entry. Assessments of over 80 peer-reviewed studies indicate that PEMFCs are achieving 0.85 A/cm² at 0.6V, while SOFCs are reaching 60% electrical efficiency in combined heat and power (CHP) applications. Currently, most deployments, comprising 62% of market share, are in the transportation sector; however, significant challenges remain in material stability and hydrogen infrastructure. Progress in fuel cell technology hinges on the integration of anion-exchange membranes, platinum-group-metal-free catalysts, and advanced manufacturing capabilities.

Fuel cells have a wide range of potential applications in various fields such as stationary power generation, transportation, and portable electronic devices, thanks to their high energy conversion efficiencies, environmentally friendly structures, and simple design features. This study takes a comprehensive approach to fuel cell technologies, starting with the fundamental operating principles and historical development process of fuel cells. Different systems, such as alkaline fuel cells (AFC), phosphoric acid fuel cells (PAFC), solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC), proton exchange membrane fuel cells (PEMFC), and direct methanol fuel cells (DMFC), are examined and compared in detail in terms of their operating principles, advantages, limitations, and application areas. Furthermore, the theoretical performance limits of fuel cells and the losses observed in the systems are analyzed, and improvement strategies to reduce these losses are dis-cussed. Special emphasis is placed on PEMFC technology due to its high potential in automotive and portable energy sys-tems. In this context, the structural components of PEMFCs, types of proton exchange membranes, and the main character-istics expected from these membranes are comprehensively addressed. To better understand proton transfer processes, pro-ton transfer mechanisms such as Grotthuss, vehicle, and surface mechanisms are also explained in detail. In conclusion, this review aims to establish a conceptual bridge between the fundamental principles of fuel cell technologies and the current challenges and advances in PEMFC membrane development research.

Fuel cell power systems are considered attractive for a wide rangeof stationary power generation applications including residential, com-mercial, and industrial distributed generation, as well as large utilitypower plants. The current interest in fuel cell systems stems from theirpotential for high efficiency (lower heating value (LHV) efficiencies of35-70 percent, depending on technology and system capacity). In addi-tion, fuel-cell technology has demonstrated very low (truly negligible)emission levels and has noise characteristics similar to air-conditioningsystems (i.e., mostly air-moving equipment). Routine maintenance offuel cells has the potential for being minimal even in low-capacity sys-tems because there are no heavily loaded mechanical subsystems re-quired (unless compressors are required for pressurized operation).Four primary fuel cell technologies are being developed for station-ary applications.• Polymer Electrolyte Membrane Fuel Cell (PEMFC);• Phosphoric Acid Fuel Cell (PAFC);• Molten Carbonate Fuel Cell (MCFC); and• Solid Oxide Fuel Cell (SOFC).The past two decades have seen impressive advancements in thescience and technology of these fuel-cell power systems. Excellent dis-cussions of the science and technology of all the major types of fuel cells,recent developments and remaining technical challenges can be found in references [1-2].We address the end-user economics of fuel cell systems for station-ary applications using planar, 5-kW anode-supported SOFC technologyas an example. Planar SOFC is receiving a great deal of attention as partof both government—the Solid State Energy Conversion Alliance (SECA)program—and industry initiatives. The increasing interest in planarSOFC is the result, in large part, to technology developments (anode-supported thin-film electrolyte designs) in which the total ohmic resis-tance of the stack is significantly reduced allowing for lower-temperatureoperation (650 °C-800°C rather than 1000 °C) than was previously thecase.We also discuss the important cost elements that determine the costof electricity from fuel cell power systems including factory, material,installation, and operating and maintenance (O&M) costs. We assess theimpact of success in ongoing R&D programs on the cost of electricity.

Fuel cells are devices that convert the chemical energy of a fuel directly into electrical energy and heat. This article begins by describing the operating principles of fuel cells, their construction, and the main problems currently limiting their commercial success. The thermodynamics of fuel cell systems is discussed, and also the effect of parameters such as pressure and temperature on cell voltage. Their use in conjunction with gas turbines is also addressed, and it is shown that this is a particularly advantageious way of operating. An overview of the main sources of losses in fuel cells is given. Several different types of fuel cell are explained. This article divides them into six categories: the proton exchange membrane fuel cell (PEMFC), the direct methanol fuel cell (PEMFC), the alkaline fuel cell (AFC), the phosphoric acid fuel cell (PAFC), the molten carbonate fuel cell (MCFC), and finally the solid oxide fuel cell (SOFC). In all cases except one it is the electrolyte that distinguishes the different types. The special features, advantages, disadvantages, operating temperature, electrode and electrolyte construction, typical applications and fuels used are described for each of these six types of fuel cell.

Energy is the basis of economic development, there is no modern civilization without the development of the energy industry. Humans have been conducting efforts to improve the high efficiency use of energy resources. There has been a number of revolutionary changes in the way to use energy during the history, from the original steam engine to internal combustion engines. Fuel cells are energy devices which transfer chemical energy stored in the fuel and oxidant directly into electrical energy. When fuel cells are continuously supplied fuel and oxidant, electricity can be made constantly. According to the different electrolytes, fuel cells can be divided into several types, such as alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), solid oxide fuel cell (SOFC), and proton exchange membrane fuel cell (PEMFC), etc.

Fuel cells are not a new technology, but they are gaining in popularity and are being intensively developed. The article presents and characterizes various types of fuel cells that are currently of interest to research and development centers dealing with environmental protection issues. These include: alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), solid oxide fuel cell (SOFC), molten carbonate fuel cell (MCFC), proton exchange membrane fuel cell (PEMFC), including direct methanol fuel cell (DMFC). The operating parameters of the previously mentioned fuel cells were compared. The principle of operation of a fuel cell was described. The growing interest in devices using hydrogen as a fuel also results from the development of Power to Gas technology (P2G). Furthermore, the article presents the potential directions of development and use of fuel cells in various fields and sectors of the economy. Fuel cells can be used in transport. The characteristic of motor vehicles fleet by fuel type in usage in the European Union was presented. The technical specification of commercially available passenger cars using fuel cells with proton exchange membrane was presented. The possibility of using fuel cells in public transport (buses, trains) was discussed. The possibilities of operation of fuel cells in combined heat and power systems (CHP) were presented. Usage of fuel cell technology in large cogeneration units and micro systems was considered. One of the presented cogeneration systems is a combination of fuel cells with a gas turbine. Another possibility of using fuel cells is energy storage systems (EES). Interesting way of using fuel cells can also be Power to Power systems, which were briefly characterized.

This chapter is focused on the properties of a direct energy conversion in fuel cells. Here a free energy of a chemical reaction is converted directly into electrical energy. Basic thermodynamics of that reaction is given, and relation of energy and reversible potential, Er, of the cell carrying out chemical reaction. The main properties of energy conversion resulting from its direct feature include the highest conversion efficiency. Possible fuels are discussed, and with H2 as a fuel, the reaction product is H2O. The possibility that fuel cells will be the major source of clean energy, particularly important for automotive application, is analyzed, considering hydrogen, ethanol, and methanol fuels. An overview of the properties of low temperature fuel cells is given. These include: Low-temperature fuel cells are the Proton Exchange Membrane or Polymer Electrolyte Membrane Fuel Cell (PEMFC), Alkaline Fuel Cell (AFC), the Direct Methanol Fuel Cell (DMFC), Direct Ethanol Fuel Cell (DMFC), and the Phosphoric Acid Fuel Cell (PAFC). The high-temperature fuel cells operate at temperatures approx. 600–1000 °C, and two different types have been developed: Molten Carbonate Fuel Cell (MCFC) and the Solid Oxide Fuel Cell (SOFC). Typical polarization curves for anode and cathode and the cell, i.e., anode and cathode potentials and cell voltage as a function of current density, are given. The cell losses under current flow are identified.

Chapter 2 - Fuel Cells and the Challenges Ahead

A fuel cell operates like a battery but does not need to be recharged, and continuously produces power when supplied with fuel and oxidant. Fuel cells’ efficiencies are not limited by the Carnot cycle of a heat engine, and the magnitudes of pollutant output from fuel cells are lower than from conventional technologies. Recently, fuel cells have high efficiencies, low noise and pollutant output, modular construction to suit load, and excellent load-following capability, promising to improve the power generation industry with a shift from central power stations and long transmission lines to disperse power generation at user sites. Fuel cells can be classified into several different types according to the type of electrolyte used: (1) proton exchange membrane fuel cell (PEMFC) [1], (2) phosphoric acid fuel cell (PAFC) [2], (3) alkaline fuel cell (AFC), (4) molten carbonate fuel cell (MCFC) [3,4] and (5) solid oxide fuel cell (SOFC). Table 15.1 lists the common fuel cell types and their respective operating temperatures, efficiencies, and electrolytes.

The fuel cell industry, which has experienced continued increases in sales, is an emerging clean energy industry with the potential for significant growth in the stationary, portable, and transportation sectors. Fuel cells produce electricity in a highly efficient electrochemical process from a variety of fuels with low to zero emissions. This report describes data compiled in 2008 on trends in the fuel cell industry for 2007 with some comparison to two previous years. The report begins with a discussion of worldwide trends in units shipped and financing for the fuel cell industry for 2007. It continues by focusing on the North American and U.S. markets. After providing this industry-wide overview, the report identifies trends for each of the major fuel cell applications -- stationary power, portable power, and transportation -- including data on the range of fuel cell technologies -- polymer electrolyte membrane fuel cell (PEMFC), solid oxide fuel cell (SOFC), alkaline fuel cell (AFC), molten carbonate fuel cell (MCFC), phosphoric acid fuel cell (PAFC), and direct-methanol fuel cell (DMFC) -- used for these applications.

Chapter 1 - 1. Introduction