Limitations of Commercializing Fuel Cell Technologies

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.

Fuel Cells. Fuel cells are electrochemical devices that convert the chemical energy of a fuel directly into electrical and thermal energy. In a typical fuel cell, gaseous fuels are fed continuously to the anode (negative electrode) compartment, and an oxidant, eg, oxygen or air, is fed continuously to the cathode (positive electrode) compartment. The electrochemical reactions take place at the electrodes to produce an electric (direct) current. The fuel cell theoretically has the capability of producing electrical energy for as long as the fuel and oxidant are fed to the electrodes. In reality, degradation or malfunction of components limits the practical operating life of fuel cells. Besides the direct production of electricity, heat is also produced in fuel cells. This heat can be effectively utilized for the generation of additional electricity or for other purposes, depending on the temperature. A practical consideration for fuel cells is compatibility with the available fuels and oxidants. One of the main attractive features of fuel cell systems is the expected high fuel‐to‐electricity efficiency. This efficiency, which runs from 40–60% based on the lower heating value (LHV) of the fuel, is higher than that of almost all other energy conversion systems. The two primary impediments to the widespread use of fuel cells are high initial cost and short operational lifetime. A variety of fuel cells has been developed for terrestrial and space applications. Fuel cells are usually classified according to the type of electrolyte used in the cells as polymer electrolyte fuel cell (PEFC), alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), and solid oxide fuel cell (SOFC). Fuel cells operating on pure H 2 and O 2 provide a useful power source in remote areas such as in space or under the sea where system weight and volume are important parameters. On the other hand, fuel cell power plants operating on fossil fuels and air offer the potential for environmentally acceptable, highly efficient, and low cost power generation. The minimum technical requirements for fuel cells for four different types of applications, ie, for buildings, industry, transportation, and utilities are given. From the standpoint of commercialization of fuel cell technologies, there are two challenges: initial cost and reliable life. Several activities, would strongly boost the prospects for fuel cell technology and include the development of (1) an active electrocatalyst for the direct electrochemical oxidation of methanol; (2) improved electrocatalysts for oxygen reduction; and (3) a more CO‐tolerant electrocatalyst for hydrogen.

Review: 375 refs.

Many types of fuel cell generation systems are applied for new and renewable energy area. Among them the most suitable fuel cell types for the system capacity from few hundred kW to MW level are the phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC) and solid oxide fuel cell (SOFC). In this paper, the fundamentals, characteristics and applications of each types of fuel cell were analyzed and introduce. Also, the technical trends of fuel cell generation was introduced.

Energy storage and conversion is a very important link between the steps of energy production and energy consumption. Traditional fossil fuels are a natural and unsustainable energy storage medium with limited reserves and notorious pollution problems, therefore demanding a better choice to store and utilize the green and renewable energies in the future. Energy and environmental problems require a clean and efficient way of using the fuels. Fuel cell functions to efficiently convert oxidant and chemical energy accumulated in the fuel directly into DC electric, with the by-products of heat and water. Fuel cells, which are known as effective electrochemical converters, and electricity generation technology has gained attention due to the need for clean energy, the limitation of fossil fuel resources and the capability of a fuel cell to generate electricity without involving any moving mechanical part. The fuel cell technologies that received high interest for commercialization are polymer electrolyte membrane fuel cells (PEMFCs), solid oxide fuel cells (SOFCs), and direct methanol fuel cells (DMFCs). The optimum efficiency for the fuel cell is not bound by the principle of Carnot cycle compared to other traditional power machines that are generally based on thermal cycles such as gas turbines, steam turbines and internal combustion engines. However, the fuel cell applications have been restrained by the high cost needed to commercialize them. Researchers currently focus on the discovery of different materials and manufacturing methods to enhance fuel cell performance and simplify components of fuel cells. Fuel cell systems’ designs are utilized to reduce the costs of the membrane and improve cell efficiency, durability and reliability, allowing them to compete with the traditional combustion engine. In this review, we primarily analyze recent developments in fuel cells technologies and up-to-date modeling for PEMFCs, SOFCs and DMFCs.

The primary focus is on the development of commercial Phosphoric Acid Fuel Cell (PAFC) powerplant systems because the PAFC, which has undergone extensive development, is currently the closest fuel cell system to commercialization. Shorter discussions are included on the high temperature fuel cell systems which are not as mature in their development, such as the Molten Carbonate Fuel Cell (MCFC) and the Solid Oxide Fuel Cell (SOFC). The alkaline and the Solid Polymer Electrolyte (SPE) fuel cell systems, are also included, but their discussions are limited to their prospects for commercial development. Currently, although the alkaline fuel cell continues to be used for important space applications there are no commercial development programs of significant size in the USA and only small efforts outside. The market place for fuel cells and the status of fuel cell programs in the USA receive extensive treatment. The fuel cell efforts outside the USA, especially the large Japanese programs, are also discussed.

Review and techno-economic assessment of fuel cell technologies with CO2 capture

The sections in this article areIntroductionWorking Principles of Fuel CellsCell and Stack ConstructionAlkaline Fuel Cells (AFCs)Proton Exchange Membrane Fuel Cell (PEMFC)AHydrogen Proton Exchange Membrane Fuel CellBDirect Methanol Fuel Cell (DMFC)Phosphoric Acid Fuel Cell (PAFC)Molten Carbonate Fuel Cell (MCFC)Solid Oxide Fuel Cell (SOFC)Fuels for Fuel CellsThermodynamics and Kinetics of Fuel CellsLow‐Temperature Fuel Cells with Gaseous ReactantsElectro‐Oxidation of PureH2AFundamentalH2Oxidation and Evolution KineticsBVoltage Losses Due toH2Oxidation Kinetics in Low‐Temperature Fuel CellsAnodicH2Oxidation in the Presence ofCOContaminationAPractical Aspects of Fuel Cell Operation withCO‐ContaminatedH2BCOTolerance Mechanisms onPtAlloysCNew Research Directions for ImprovedCO‐Tolerant Anode CatalystsOxygen Reduction ReactionAOxygen Reduction Kinetics and Kinetic Losses inH2/Air Fuel CellsBQuantification of a Catalyst'sORRActivity inPEMFCsCORRActivity inPAFCsorH3PO4/PBI‐Based MembranesFCsDORRActivity inPEMFCsCompared with DiluteHClO4EPtParticle Size Effect on theORRActivityFORRMechanismGPtAlloys and OtherORRCatalystsCatalyst and Catalyst‐Induced Degradation MechanismsADissolution of Cathode Catalyst ConstituentsBCarbon Support CorrosionCImpact of ContaminantsDH2O2andOHRadical‐InducedPFSADegradationFuel Cells for Direct Oxidation of Liquid FuelsDirect Methanol Fuel CellsAState‐of‐the‐ArtDMFCPerformance LimitationsBAnode Catalyst Performance LimitationsCDMFCPerformance Limit with CurrentPtRuCatalystsDMethanol Electro‐Oxidation MechanismEPtRuCatalyst Modifications and Alternative CatalystsFMethanol‐Tolerant CathodesDirect Ethanol Fuel CellsDirect Formic Acid Fuel CellsFuel Cell ApplicationsGeneralTransportation ApplicationsStationary ApplicationPortable ApplicationsFinal CommentsAcknowledgments

The mission of the fuel cell systems program of the Department of Energy, Office of Fossil Energy, in partnership with its customers and stakeholders, is to foster the creation of a new domestic fuel cell industry. This industry should be capable of commercialization of new, improved fuel cell power generation systems and thereby provide significant economic and environmental benefits. This program is aligned with the Department of Energy`s core mission (business line) of energy resources. The Department of Energy (DOE), Office of Fossil Energy, is participating with the private sector in sponsoring the development of molten carbonate fuel cell (MCFC) and solid oxide fuel cell (SOFC) technologies for application in the utility, commercial and industrial sectors. Phosphoric acid fuel cell (PAFC) development was sponsored by the Office of Fossil Energy in previous years and is now being commercialized by the private sector. This document describes the fuel cell activities of the DOE Office of Fossil Energy.

Innovative solid carbonate-ceria composite electrolyte fuel cells

The concept of hybrids combining fuel cell and gas turbine systems is without question neoteric, and probably is less than eight years old. However, this concept is in a sense a logical development derived from the many early systems that embodied the key features of rotating machinery to compress air. It was the introduction of high temperature fuel cells such as the solid oxide fuel cell (SOFC) that allowed the concept of hybrid gas turbine fuel cell systems to take root. The SOFC with an operating temperature circa 1000° C matched well with small industrial gas turbines that had firing temperatures on the same order. The recognition that the SOFC could be substituted for the gas turbine combustor was the first step into the realm of fuel cell topping systems. Fuel cells in general were recognized as having higher efficiencies at elevated pressures. Thus the hybrid topping system where the gas turbine pressurized the fuel cell and the fuel cell supplied the hot gases for expansion over the turbine promised to provide a high level of synergy between the two systems. Bottoming systems using the exhaust of a gas turbine as the working fluid of a fuel cell such as the molten carbonate fuel cell (MCFC) have been identified and are potential future power generation hybrid systems. The MCFC is especially well suited to the bottoming role because of the need to have carbon dioxide present in the inlet air stream. The carbon dioxide in the gas turbine exhaust allows the high temperature blower, normally used to recirculate and inject exhaust products into the inlet air, to be eliminated. Hybrid systems have the potential of achieving fossil fuel to electricity conversion efficiencies on the order of 70% and higher. The costs of hybrid systems in dollars per kilowatt are generally higher than say an advanced gas turbine that is available today but not by much. The net energy output over the life of a hybrid topping system is similar to that of a recuperated gas turbine but possibly lower than a high-efficiency simple-cycle machine, depending on the efficiency of the hybrid. Methodologies to aid in the selection of the hybrid system for future development have to be developed and used consistently. Life cycle analyses (LFA) provide a framework for such selection processes. In particular the concept of net energy output provides a mechanism to assign relative worth to competing concepts.

The fuel-cycle energy use and greenhouse gas (GHG) emissions associated with the application of fuel cells to distributed power generation were evaluated and compared with the combustion technologies of microturbines and internal combustion engines, as well as the various technologies associated with grid-electricity generation in the United States and California. The results were primarily impacted by the net electrical efficiency of the power generation technologies and the type of employed fuels. The energy use and GHG emissions associated with the electric power generation represented the majority of the total energy use of the fuel cycle and emissions for all generation pathways. Fuel cell technologies exhibited lower GHG emissions than those associated with the U.S. grid electricity and other combustion technologies. The higher-efficiency fuel cells, such as the solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC), exhibited lower energy requirements than those for combustion generators. The dependence of all natural-gas-based technologies on petroleum oil was lower than that of internal combustion engines using petroleum fuels. Most fuel cell technologies approaching or exceeding the DOE target efficiency of 40% offered significant reduction in energy use and GHG emissions.

The high costs of fuel cell stacks are often prohibitive for research applications. Instead, researchers tend to either perform tests on individual cells under emulated load conditions, or they use model-based emulated fuel cell stacks to test realistic loads. This paper presents an alternative technique that allows the simultaneous investigation of both cell and hardware. In this technique, an amplifier takes as input the voltage of a reference fuel cell and reproduces the “scaled-up” voltage that would be provided by a stack of similar cells. The output terminals of this simulated stack can be connected to realistic loads, which are series connected with the reference cell to maintain a one-to-one correspondence of cell and load currents. This technique allows the simultaneous investigation of stack/load interactions, stack electrochemical performance characteristics, and stack durability under load. The amplifier electronics are independent of the fuel cell allowing its use with all fuel cell types, e.g., solid oxide fuel cells (SOFCs) or proton exchange membrane fuel cells. We demonstrate the emulator using a single planar SOFC and under several real loads. The data collected reveal good steady-state and dynamic accuracy, and the observed electrical interactions highlight the utility of the emulator in cell and hardware-in-the-loop testing. Ultimately, this technique provides fuel cell system researchers and developers a low-cost, easily implemented tool for rapid assessment of novel fuel cell technologies under real-world loading conditions.

Innovative solid carbonate–ceria composite electrolyte fuel cells

10 - Novel fuel cells and materials