Fuel cell conversion

In catalysis, adsorbed CO may retard some reactions such as olefin hydrogenation, fuel cell conversion, and enantioselective hydrogenation. For instance, Lercher and coworkers observed the deactivation of Pt/Si02 in the liquid-phase hydrogenation of crotonaldehyde, and ascribed this deactivation to the decomposition of crotonaldehyde on platinum surface to adsorbed CO [138]. Blaser and coworkers found that the addition of a small amount of formic acid decreases the rate of liquid-phase hydrogenation of ethyl pyruvate on cinchonidine-modified Pt/Al203 catalyst, which they explained as the decomposition of formic acid on the catalyst to adsorbed CO. Interestingly, the addition of acetic acid does not decrease the reaction rate, but whether acetic acid decomposes on the catalyst as formic acid does was not mentioned [139]. 

It follows that this scheme—which would lead to a steady-state, high-technology economy without planetary warming or pollution—depends centrally upon electrochemical technology (water electrolysis, fuel cell conversion). If a clean, safe nuclear source were developed that could compete economically with cheap photovoltaics6,... 

For fuel cell conversion of hydrogen, the industrial progress is such that meaningful life-cycle studies can start to be made on a fairly detailed basis. A concrete example of this will be given. 

Finally, for the hydrogen fuel cell car, the solar radiation to wind conversion-efficiency is taken as 100% (following arguments of Sorensen, 1996c), the wind turbine efficiency as 35%, the electrolysis efficiency as 80%, the fuel cell conversion efficiency as 55% and the rest as for methanol. The overall accumulated efficiencies are 1.4 x 10 for the methanol route and 0.054 for the wind-hydrogen route. 

On the other hand, for liquid hydrogen, the overall efficiency from the fuel cell conversion is e = 16%-47% with a total power of electricity between 9 and 19 kWh. 

In the following, SOFC materials are detailed in view of the state of the art and the lowering of their operation temperatures at high fuel cell conversion efficiencies ... 

Figure 2.14 Fuel cell conversion of methane into electric power [418] [420], Exergy changes at ideal conditions, 250°C. By the indirect route, 4H2 represents an exergy of 1.13, but at the expense of the exergy of CH4 used as feed + fuel (0.32). Reproduced with the permission of Taylor Francis.

Direct Methane Conversion, Methanol Fuel Cell, and Chemical Recycling of Carbon Dioxide... 

M. A. DeLuchi, E. D. Laison, and R. H. WiUiams, Hjdrogen andMethanol Production and Use in Fuel Cell andintemal Combustion Engine Vehicles—-A preliminary Assessment, Vol. 12, Solid Fuel Conversion for the Transportation Sector, ASME, Fuels and Combustion Technologies Division, New York, 1991, pp. 55-70. 

Other Specialty Chemicals. In fuel-ceU technology, nickel oxide cathodes have been demonstrated for the conversion of synthesis gas and the generation of electricity (199) (see Fuel cells). Nickel salts have been proposed as additions to water-flood tertiary cmde-oil recovery systems (see Petroleum, ENHANCED oil recovery). The salt forms nickel sulfide, which is an oxidation catalyst for H2S, and provides corrosion protection for downweU equipment. Sulfur-containing nickel complexes have been used to limit the oxidative deterioration of solvent-refined mineral oils (200). 

Fuel Cell Catalysts. Euel cells (qv) are electrochemical devices that convert the chemical energy of a fuel direcdy into electrical and thermal energy. The fuel cell, an environmentally clean method of power generation (qv), is more efficient than most other energy conversion systems. The main by-product is pure water. 

Michael Krumpelt, Ph.D., Manager, Fuel Cell Technology, Argonne National Laboratory Member, American Institute of Chemical Engineers, American Chemical Society, Electrochemical Society (Section 27, Energy Resources, Conversion, and Utilization)... 

Fuel Cell Efficiency The theoretical energy conversion efficiency of a fuel cell ° is given by the ratio of the free energy (Gibbs function) of the cell reaction at the cell s operating temperature AG to the enthalpv of reaction at the standara state AH°, both quantities being based on a mole of fuel ... 

Typical polarization curves for alkaline fuel cells are shown in Fig, 27-63, It is apparent that the all aline fuel cell can operate at about 0,9 and 5()() rnA/cnr current density. This corresponds to an energy conversion efficiency of about 60 percent IIII, The space shuttle orbiter powder module consists of three separate units, each measuring 0,35 by 0,38 by I rn (14 by 15 by 40 in), weighing 119 kg (262 lb), and generating 15 kW of powder. The powder density is about 100 W/L and the specific powder, 100 W/kg,... 

Ginley, D.S. el al. (eds.) (1998) in Materials for Electroehemical Storage and Energy Conversion // - Batteries, Capacitors and Fuel Cells, MRS Symp. Proe., vol. 496, (Warrendale, PA). 

A fuel cell is equivalent to a generator it converts a fuel s chemical energy directly into electricity. The main difference between these energy conversion devices is that the fuel cell acccomplishes this directly, "without the two additional intermediate steps, heat release and mechanical motion. 

Fuel cell is an ambiguous term because, although the conversion occurs inside a fuel cell, these cells need to be stacked together, in a fuel cell stack, to produce useful output. In addition, various ancillai y devices are required to operate the stack properly, and these components make up the rest of the fuel cell system. In this article, fuel cell will be taken to mean fuel cell system (i.e., a complete standalone device that generates net power). 

Electrical management, or power conditioning, of fuel cell output is often essential because the fuel cell voltage is always dc and may not be at a suitable level. For stationai y applications, an inverter is needed for conversion to ac, while in cases where dc voltage is acceptable, a dc-dc converter maybe needed to adjust to the load voltage. In electric vehicles, for example, a combination of dc-dc conversion followed by inversion may be necessary to interface the fuel cell stack to a, 100 V ac motor. 

Fuel cells can run on fuels other than hydrogen. In the direct methanol fuel cell (DMFC), a dilute methanol solution ( 3%) is fed directly into the anode, and a multistep process causes the liberation of protons and electrons together with conversion to water and carbon dioxide. Because no fuel processor is required, the system is conceptually vei"y attractive. However, the multistep process is understandably less rapid than the simpler hydrogen reaction, and this causes the direct methanol fuel cell stack to produce less power and to need more catalyst. 

Ahmed, S. (1997). Partial Oxidation Reformer Development for Fuel Cell Vehicles. Proceedings of the. 12nd Intersociety Energy Conversion Engineering Conference. Paper 97081 (August). 

Fuel Cells The Next Step in Chemical- to Electrical-Energy Conversion ... 

Fuel cells have attracted considerable interest because of their potential for efficient conversion of the energy (AG) from a chemical reaction to electrical energy (AE). This efficiency is achieved by directly converting chemical energy to electricity. Conventional systems burn fuel in an engine and convert the resulting mechanical output to electrical power. Potential applications include stationary multi-megawatt power plants, battery replacements for personal electronics, and even fuel-cell-powered unmanned autonomous vehicles (UAVs). 

Conversely, the use of elevated temperatures will be most advantageous when the current is determined by the rate of a preceding chemical reaction or when the electron transfer occurs via an indirect route involving a rate-determining chemical process. An example of the latter is the oxidation of amines at a nickel anode where the limiting current shows marked temperature dependence (Fleischmann et al., 1972a). The complete anodic oxidation of organic compounds to carbon dioxide is favoured by an increase in temperature and much fuel cell research has been carried out at temperatures up to 700°C. 

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