combined cycle gas and steam turbine power plants third editio pdf

Why has the combination gas turbine/steam turbine power plant, unlike other combined-cycle power plants, managed to find wide acceptance? Two main reasons can be given:
• It is made up of components that have already proven
themselves in power plants with a single cycle. Development costs are therefore low.
• Air is a relatively non-problematic and inexpensive
medium that can be used in modern gas turbines at an elevated temperature level (above 1000 °C). That provides the optimum prerequisites for a good “topping cycle.” The steam process uses water, which is likewise inexpensive and widely available, but better suited for the medium and low temperature ranges. The waste heat from a modern gas turbine has a temperature level advantageous for a good steam process.

It therefore is quite reasonable to use the steam process for the “bottoming cycle.” That such combination gas turbine/steam turbine power plants were not more widely used even earlier
has clearly been due to the historical development of the gas turbine. Only in recent years have gas turbines attained inlet temperatures that make it possible to design a very highefficiency cycle. Today, however, the installed power capacity of combined-cycle gas turbine/steam turbine power plants worldwide world totals more than 30,000 MW.