The use of gas turbine for heat and power production is widespread. Usually, the temperature of the gas exhausted from a gas turbine is greater than that required from the thermal utilities. Therefore, it may results convenient, before gas cooling, to produce additional work expanding the high temperature flue gas below the ambient pressure. Subsequently, a compressor will discharge to the ambient the cooled gas.
In the present paper, a thermodynamic analysis of a gas turbine working with the discharge pressure below ambient pressure (BAGT) is carried out considering different cogenerative applications. It resulted that the BAGT is especially convenient for low thermal utility temperature that strongly increases the gas turbine electric efficiency.
Moreover, in order to obtain high electric performance also with high thermal utility temperature, the employment of an additional heat exchanger (BAGT + cooler) has been taken into account.