Inlet air temperature increase results in a considerable reduction in GTCC power output. Present design of inlet air cooling system usually applied static method, which considered a constant depression of inlet air temperature, an approximate estimate of runtime, output power increase and fuel consumption variation per temperature depression, etc. However, to a crumb, at least another two problems should be studied. One is GTCC performance variation with inlet air temperature, since the kilowatt increment per centigrade is not a constant; the other is off design performance of inlet air cooling system, since the inlet air temperature depression through the cooling system varies with the actual operation conditions, such as ambient air temperature and cooling water temperature, etc. This paper presents an economic evaluation with numerical integration method on GTCC inlet air cooling with absorption chiller. For a typical GTCC composed of series E gas turbine and combined components, their non-dimensional performance curves are fitted with regression equations. Associating with these equations, the inlet air temperature characteristics of GTCC are simulated; and the fitted analytical expressions for GTCC inlet air temperature characteristics are also presented. The simulation method of off design performance of a typical absorption chiller is described. For a typical GTCC with inlet air cooling in south China area, integrated with the everyday typical weather data, GTCC everyday average output power and fuel consumption, output power increment and GTCC fuel consumption increment are simulated. The simulation results show that, for every 1°C depression in inlet air temperature, the GTCC output power increases 0.5%, while heat rate varies slightly and trends towards a rise at the inlet air temperature of about 15°C. Research on inlet air cooling scheme (Scheme 10°C, cooling the ambient air temperature from ambient temperature 30°C to 10°C) shows that, Scheme 10°C yields annual average 16°C of inlet air temperature depression. Economic evaluation based on numerical integration indicates that, in the case of Scheme 10°C, annual output power increases by 8.27%, fuel consumption rate increases by 1.03%; payback period approximately amounts to 2.0 years when power price is 12 cent/(kW.h) and fuel cost is $265/t.

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