Electrical generation work/heat ratio

Figure 9. Net revenue generated as a function of work/ heat ratio for various market prices of electricity a hot water supply temperature of 250°F> and a fuel cost of 2 per million Btu.

The calculated values of exergy ratios for various primary and secondary sources are shown in Table 1. It 1s to be noted that all the fossil fuel sources are inherently of very high quality. The value of aE greater than unity for coal stems from the fact that a reversible oxidation of carbon at ambient temperature has a negative TQ S and results in production of more work than the enthalpy of combustion, with an associated absorption of heat from the environment. In spite of these high values of < r, when fossil fuels are combusted, say for electrical generation, the maximum temperature is limited not by thermodynamic considerations but by materials constraints. The effective < under this limitation is restricted to values below 0.65. t... 

The gas turbine is operated at a compression ratio that maximizes the work produced per weight of air, as explained in the first reference. Your turbine is equivalent or similar to the W501G turbine described in the second reference. Its electrical power output is 230 MW, which fixes the size of your combined cycle. You are to configure a set of steam generators and steam turbines that provides the economic-optimum amount of electric power from the heat in the exhaust from the free turbine. 

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