Problems with Fuel Cells

In PEM fuel cells, fed with neat hydrogen on the anode side, water fluxes in the membrane play a crucial role for the overall water balance of the cell. For the following considerations of this problem it will be supposed that the essential ex situ membrane properties are known. Based on this knowledge the membrane performance in the fuel cell will be studied. Effects of membrane properties and externally controlled conditions will be rationalized. This kind of understanding of structure versus function provides diagnostic tools to check the suitability of membranes for... 

Fuel flexibility and new infrastructures in fuels are three-way issues between the auto industry, the energy providers, and the federal government. Dealing with this three-way interface will be a problem, especially since each institution is used to having its own way. Fortunately, there is an institution like the California Fuel Cell Partnership, which is not just localized to California but is the world s fuel cell partnership. It is the only institution in the world that involves major public sector players, the major energy providers, and the major auto companies of the world. This is the only forum where they can all interact and struggle with the fuel cell problem. 

For the fuel cell power plants, the economic and lifetime related issues hinder the acceptance of fuel cell technologies. Such problems were not associated with fuel cells but with auxiliary fuel cell units such as thermal management, reactant storage, and water mans emenL Therefore, the auxiliary units of fuel cell systems should be further developed to address these issues. 

Other publications have mentioned an air-breathing fuel ceU in their titles (e.g., Jaouen et al., 2005), but it must be pointed out that on the whole, the important problem of fuel cell operation with a passive air snpply from the ambient atmosphere and a passive elimination of reaction prodncts and heat has not been investigated sufficiently. 

Many impurities other than those discussed here may also affect both the anode and the cathode reactions in fuel cells. Gaseous impurities are known to be the most serious factors (see also chapters Air Impurities and Performance and Durability of PEM Fuel Cells Operating with Reformate ) at the fuel cell anode and the cathode. In this chapter, those impurities were excluded from discussion, and only the impacts of cationic and organic substances (that may occur as water-soluble species) on the ORR were considered, but the results indicated that these contaminants were equally serious problems for fuel cell degradation. 

The overall efficiency of fuel cells increases with size because problems of heat loss or of gas pumping can be dealt with properly only if the size of the fuel battery is above a certain minimum of a few kilowatts. Above this output there is little increase in efficiency as the size is increased the efficiency of steam turbine power plants increases with size up to about 500 megawatts. This consideration alone implies that fuel cells will be best used for small scale operations, such as supplying electricity in remote areas or powering vehicles, such as delivery vans or locomotives. They will also be used where the advantages of fuel cells, the quiet operation, reliability and absence of pollution, will be more important than efficiency. 

In principle, therefore. SOFC technology is both simpler, more flexible and more efficient than other fuel cell types, with potentially significant cost benefits. However, there are several major problems associated with internal reforming in SOFCs, which can lead to deactivation and a loss in cell performance, and in some cases materials failure, and hence result in poor cell durability. A particular... 

A signihcant problem in tire combination of solid electrolytes with oxide electrodes arises from the difference in thermal expansion coefficients of the materials, leading to rupture of tire electrode/electrolyte interface when the fuel cell is, inevitably, subject to temperature cycles. Insufficient experimental data are available for most of tire elecuolytes and the perovskites as a function of temperature and oxygen partial pressure, which determines the stoichiometty of the perovskites, to make a quantitative assessment at the present time, and mostly decisions must be made from direct experiment. However, Steele (loc. cit.) observes that tire electrode Lao.eSro.rCoo.aFeo.sOs-j functions well in combination widr a ceria-gadolinia electrolyte since botlr have closely similar thermal expansion coefficients. 

Fuel cells, which rely on electrochemical generation of electric power, could be used for nonpolluting sources of power for motor vehicles. Since fuel cells are not heat engines, they offer the potential for extremely low emissions with a higher thermal effidency than internal combustion engines. Their lack of adoption by mobile systems has been due to their cost, large size, weight, lack of operational flexibility, and poor transient response. It has been stated that these problems could keep fuel cells from the mass-produced automobile market until after the year 2010 (5). 

The most promising fuel cell for transportation purposes was initially developed in the 1960s and is called the proton-exchange membrane fuel cell (PEMFC). Compared with the PAFC, it has much greater power density state-of-the-art PEMFC stacks can produce in excess of 1 kWA. It is also potentially less expensive and, because it uses a thin solid polymer electrolyte sheet, it has relatively few sealing and corrosion issues and no problems associated tvith electrolyte dilution by the product water. 

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