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PhD Thesis - Energy Systems Research Unit - University of Strathclyde

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Is PL < Min ?<br />

No<br />

Is PL = 0 ?<br />

No<br />

Is PL = PC1 ?<br />

No<br />

Is PL = PC2 ?<br />

No<br />

Is PL = PC3 ?<br />

No<br />

Is PL = 100 % ?<br />

No<br />

Is PL < PC1 ?<br />

No<br />

Is PC1 < PL < PC2 ?<br />

No<br />

Is PC2 < PL < PC3 ?<br />

No<br />

PC3 < PL < PC4<br />

Yes<br />

Yes<br />

Yes<br />

Yes<br />

Yes<br />

Yes<br />

Yes<br />

Yes<br />

Yes<br />

SFC = 0<br />

PL = 0<br />

Power = 0<br />

SFC = 0<br />

SFC = SFC1<br />

SFC = SFC2<br />

SFC = SFC3<br />

SFC = SFC4<br />

133<br />

SFC = Specific Fuel Consumption (liquid fuels)<br />

SFC = Mechanical Efficiency (gaseos fuels)<br />

PC1 = 25 % or other input percentage<br />

PC2 = 50 % or other input percentage<br />

PC3 = 75 % or other input percentage<br />

SFC1 = SFC at PC1<br />

SFC2 = SFC at PC2<br />

SFC3 = SFC at PC3<br />

SFC4 = SFC at 100 %<br />

SFC = ((PC1 - PL) / PC1)) x (SFC1 - SFC2) + SFC1<br />

SFC = ((PL - PC1) / (PC2 - PC1)) x (SFC2 - SFC1) + SFC1<br />

SFC = ((PL - PC2) / (PC3 - PC2)) x (SFC3 - SFC2) + SFC2<br />

SFC = ((PL - PC3) / (PC4 - PC3)) x (SFC4 - SFC3) + SFC3<br />

Figure 5.9 Specific Fuel Consumption or Efficiency Determination<br />

As engines may be started and stopped at different times as demand increases<br />

and decreases, it is necessary to be able to see graphs showing the loading <strong>of</strong> all<br />

engines in order to assess the way in which they require to be used. As these<br />

graphs overlap, it is also necessary to state how many engines have been used to<br />

satisfy the peak demand. Figure 5.10 shows the output <strong>of</strong> a biodiesel run<br />

generator set, where three engines are required to meet the electricity demand.<br />

Two engines are running constantly at varying load, following the electricity<br />

demand, and a third is needed to help supply the peak demand between 0900<br />

and 1700 hours.

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