Portable fuel cells components

With regard to low temperature fuel cells (PEM), efforts must be guided to materials development (catalysts, electrodes, electrolytes, plates, seals, etc), fuel cells components development and its manufacturing methods, fuel cells prototypes development, systems based in fuel cells for transport, stationary and portable applications, and fuel processors. 

The first edition of this book was published in December 2008. This second edition is updated with information published after this date up to October 2011. Two chapters of the first edition were rewritten Chapter 15 (modeling of fuel cells) and Chapter 14—now Chapter 17 (small fuel cells for portable devices). In this edition three new chapters of high current interest are also included Chapter 14 (structural and wetting properties of fuel cell components). Chapter 16 (experimental methods for fuel cell stacks), and Chapter 18 (nonconventional design principles for fuel cells). 

Because of the modular nature of fuel cells, they are attractive for use in small portable units, ranging in size from 5 W or smaller to 100 W power levels. Examples of uses include the Ballard fuel cell, demonstrating 20 hour operation of a portable power unit (32), and an IFC military backpack. There has also been technology transfer from fuel cell system components. The best example is a joint IFC and Praxair, Inc., venture to develop a unit that converts natural gas to 99.999% pure hydrogen based on using fuel cell reformer technology and pressure swing adsorption process. 

Because of its lower temperature and special polymer electrolyte membrane, the proton exchange membrane fuel cell (PEMFC) is well-suited for transportation, portable, and micro fuel cell applications. But the performance of these fuel cells critically depends on the materials used for the various cell components. Durability, water management, and reducing catalyst poisoning are important factors when selecting PEMFC materials. 

Apart from hydrocarbons and gasoline, other possible fuels include hydrazine, ammonia, and methanol, to mention just a few. Fuel cells powered by direct conversion of liquid methanol have promise as a possible alternative to batteries for portable electronic devices (cf. below). These considerations already indicate that fuel cells are not stand-alone devices, but need many supporting accessories, which consume current produced by the cell and thus lower the overall electrical efficiencies. The schematic of the major components of a so-called fuel cell system is shown in Figure 22. Fuel cell systems require sophisticated control systems to provide accurate metering of the fuel and air and to exhaust the reaction products. Important operational factors include stoichiometry of the reactants, pressure balance across the separator membrane, and freedom from impurities that shorten life (i.e., poison the catalysts). Depending on the application, a power-conditioning unit may be added to convert the direct current from the fuel cell into alternating current. 

PEM fuel cells - continue work on components (electrolyte, electrodes, bipolar plates), systems (modelling and design) and phenomenology (thermohydraulics). Study and development of micro-cells for portable applications. 

HFC R D work across the spectrum of fuel cell types and auxiliary components. Focus on PEM and large-scale MCFC and SOFC, and on micro DMFCs for portable applications. 

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