Locomotives turbine-powered electric

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. 

Increased problems of deposit formation and corrosion are encountered in industrial gas turbines such as those used in electric power generation and locomotives. Here, residual fuel oil must be used for economic reasons. Ash may deposit and tend to choke the gas turbine, thereby reducing volumetric efficiency. Moreover, vanadium and sodium, two common ash components, cause severe corrosion of super alloys at the high temperatures prevailing in gas turbines. Sulfur content is also significant, because the metal sulfates that form are much lower in melting point than the corresponding oxides and thereby contribute to deposit formation (17). 

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