The gas turbine as a cogeneration

THE GAS TURBINE AS A COGENERATION (COMBINED HEAT AND POWER) PLANT 

In Fig. 9.2a, the work output from the unfired plant is shown to be equal to unity and the heat supply F q = 4.0. Further, it is assumed that the useful heat supplied is (2u)cg = 2.25 and the unu.sed non-useful heat is (2nu)cg = 0-75. An important parameter of this CHP plant is the ratio of useful heat supplied to the work output, = (2u)cg cg = 2.25. 

For a plant with a fired heat boiler, as in Fig. 9.2b, both the work output Wcg ind the main heat supply = F are assumed to be unaltered at 1.0 and 4.0, respectively, but supplementary fuel energy is supplied to the WHB, Fj = 1.5F = 6.0. The useful heat supplied is then assumed to increase to 7.2 and the non-u.seful heat rejected to be 1.8. Thus the parameter A changes to 7.2. 

For a site with a fixed power demand throughout the year, the unfired plant illustrated in Fig. 9.2a is suitable for summer operation when the heat load is light. 

It could then be supplementarily fired in the winter when the heat load is heavier, as in Fig. 9.2b. 

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Chapter 9. The gas turbine as a cogeneration (combined heat and power) plant... 

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