This paper presents energy and exergy analyses of a closed-cycle gas turbine using transcritical CO2
(T-CO2). The gas turbine (GT) system is developed in order to decrease the temperature of the
exhaust gas at 567 oC in Gaziantep Municipal Solid Waste (MSW) Power Plant and also produce
additional power from the plant. In this designed model, whole cycle is composed of a closed-cycle
GT using supercritical CO2 (S-CO2), an organic Rankine cycle and a closed-cycle GT using T-CO2. The
isentropic efficiencies of turbine and compressor, and the effectiveness of heat exchangers of the
closed-cycle gas turbine using T-CO2 are assumed as 0.95, 0.90 and 0.85, respectively. The minimum
and maximum operating pressures are utilized as 6.916 MPa and 13 MPa, respectively in this
combined cycle. In addition to this, in order to maintain the transcritical state, the minimum
temperature of the cycle is limited to 28.15 oC. According to the thermodynamic analyses, the
highest and the lowest exergy destructions are found to be 467.56 kW for gas turbine heat
exchanger and 7.91 kW for the compressor, respectively. Exergetic efficiencies of the turbine and
compressor are evaluated as 95.72 % and 91.03 %, respectively. Exergetic efficiencies of the turbine
and the precooler are found to be the maximum and minimum among subcomponents of closedcycle
gas turbine using T-CO2. The total power production of the cycle, the energetic and exergetic
efficiencies of the combined system are found to be 206.39 kW, 10.61 % and 30.03 %, respectively.
The reason of low energetic efficiency can be explained with low inlet temperature of heat source
and high effectiveness of gas turbine heat exchanger.