Direct fuel cells

Leo, A.J., Ghezel-Ayagh, H., and Sanderson, R., Ultra High Efficiency Hybrid Direct Fuel Cell/Turbine Power Plant, ASME 2000-GT-0552, October-November 1999... 

The PAFC is, however, suitable for stationary power generation, but faces several direct fuel cell competitors. One is the molten carbonate fuel cell (MCFC), which operates at "650°C and uses an electrolyte made from molten potassium and lithium carbonate salts. Fligh-teinperature operation is ideal for stationary applications because the waste heat can enable co-generation it also allows fossil fuels to be reformed directly within the cells, and this reduces system size and complexity. Systems providing up to 2 MW have been demonstrated. 

Direct food additives, 12 29, 34 categories of, 22 30 function of, 22 30 Direct formed polyimides, 20 284 Direct fuel cells, 22 221 Direct-gap semiconductors, 14 837 ... 

In the European Union, ethanol is consumed in Spain, France, Sweden and Germany, especially after conversion into ETBE (ethyl tert-butyl ether), except in Sweden, but its use is increasing in all the other countries. New uses of bioethanol, e.g., in ethanol-direct fuel cells or as raw material for other chemicals, will further expand bioethanol use and production. Table 9.1 summarizes bioethanol production in different countries by 2004 [1], Owing to political decisions (EU directive setting at 5.75% the proportion of biofuels in fuels) and incentive taxation... 

In early 2000, FCE s Direct Fuel Cell (DFC) went into a joint public/private development with NETL. This system uses internal conversion of the natural-gas fuel to hydrogen, as opposed to an external unit. This reduces costs and creates efficient use of excess heat. The DFC system has already passed 8600 hours and a one-year milestone at FCE s headquarters. 

The European Direct Fuel Cell Consortium carries out the largest European program for the commercialization of MCFC. They are developing an innovative direct fuel cell process which is internally reformed and operates on humidified hydrocarbon fuels. They have successfully tested a 292 cell, 155 kW stack (60% of maximum power). 

Direct Fuel Cell Bielefeld, Germany Continuing 11/199 9 4,300+ 500+ 250 225 45 90... 

Bert, P., Bianchini, C., Giambastiani, G., Miller, H., Santiccioli, S., Tampucci, A. and Vizza, E. (2006) Direct fuel cells comprising a nitrogen compounds and... 

The ceramic properties of EU2O3 were investigated by Curtis and Tharp [305]. The electric conductivities of rare earth oxides including EU2O3 between 600—1300° C were reported [675]. The selective oxidation of Ci to C5 olefins and Ci to C5 alcohols by direct fuel cells employing noble metal anodes and aqueous H2SO4 electrolytes was found to be enhanced [676] by small additions of soluble salts of Ce, Eu and Yb. 

However, in the direct fuel cell, methane is used directly. 

Without considering batteries and other chemical storage devices, there are effectively six types of primary or direct fuel cell technologies currently being developed alkaline fuel cells (AFC), polymer electrolyte fuel... 

The MTU MCFC provides catalysed 600 °C anode reform capability, with flat anode temperature distribution. In contrast the 1000 °C SOFC encounters difficulties with anode reform, in which excessive reaction rates lead to unacceptable, thermally stressed, local anode cool zones. The title direct fuel cell (DFC) is used, to highlight the absence of a separate combustion-heated 800 °C reformer and its pre-reformer. The balance of plant flow sheet is shown in Figure 5.3. 

Fuel cells, due to their higher efficiency in the conversion of chemical into electrical energy vhth respect to thermo-mechanical cycles, are another major area of R D that has emerged in the last decade. Their effective use, ho vever, still requires an intense effort to develop ne v materials and catalysts. Many relevant contributions from catalysis (increase in efficiency of the chemical to electrical energy conversion and the stability of operations, reduce costs of electrocatalysts) are necessary to make a step for vard in the application of fuel cells out of niche areas. This objective also requires the development of efficient fuel cells fuelled directly vith non-toxic liquid chemicals (ethanol, in particular, but also other chemicals such as ethylene glycol are possible). Together vith improvement in other fuel cell components (membranes, in particular), ethanol direct fuel cells require the development of ne v more active and stable electrocatalysts. 

Another interesting development in natural gas fueled fuel cell area is the Direct Fuel Cell developed by Energy Research Corporation (ERC Danbury, CT). This is a carbonate fuel cell which could use directly either natural gas or coal gas without the necessity of external supply (usually by steam reforming of hydrocarbon fuel) of hydrogen. Since the galvanic combustion of methane is essentially a zero entropy process, the maximum theoretical efficiency could be 100%. A carbonate fuel cell was chosen because ... 

Rechargeable direct fuel cells using organic hydrides... 

Some rechargeable direct fuel cells using organic hydrides will be available in the near future to miniaturize the fuel cells for mobile phones and laptop computers, cordless domestic electrical appliances, nursing robots and even cars. These could work for many hours and be recharged using off-peak household electricity and sustainable wind /solar power. 

PANI-NTs synthesized by a template method on commercial carbon cloth have been used as the catalyst support for Pt particles for the electro-oxidation of methanol [501]. The Pt-incorporated PANl-NT electrode exhibited excellent catalytic activity and stabUity compared to 20 wt% Pt supported on VulcanXC 72R carbon and Pt supported on a conventional PANI electrode. The electrode fabrication used in this investigation is particularly attractive to adopt in solid polymer electrolyte-based fuel cells, which arc usually operated under methanol or hydrogen. The higher thermal stabUity of y-Mn02 nanoparticles-coated PANI-NFs on carbon electrodes and their activity in formic acid oxidation pomits the realization of Pt-free anodes for formic acid fuel cells [260]. The exceUent electrocatalytic activity of Pd/ PANI-NFs film has recently been confirmed in the electro-oxidation reactions of formic acid in acidic media, and ethanol/methanol in alkaline medium, making it a potential candidate for direct fuel cells in both acidic and alkaline media [502]. 

The electrical performance figures of active direct methanol fuel cells are much higher than those of passive ones. Yet owing to the need to use many auxiliary pieces of equipment, such as pumps, valves, and controllers, power plants with active direct fuel cells are much more complex and, in a number of cases, are less reliable in their operation. Also, part of the electrical energy generated by them is getting used in the auxiliary equipment. 

The generated potential via exergonic reactions in direct fuel cells is partly used to promote electrode reactions (kinetic overpotential), while in indirect fuel cells, the fuel is first processed into simpler fuels (to reduce the kinetic overpotential) via conventional catalytic reactors, or CMRs, in which temperature is used as the key operating parameter to accomplish the desired kinetics and equilibrium conversions. Among the direct fuel cells, e.g., PEMFCs use hydrogen, direct methanol fuel cell (DMFC) uses methanol, while the SOFC can operate directly on natoral gas (Figiue 15.3). However, in indirect fuel cells, a complex fuel must be suitably reformed into simpler molecules such as H2 and CO before it can be used in a fuel ceU. 

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