Techno-economic analysis of cascaded supercritical carbon dioxide combined cycles for exhaust heat recovery of typical gas turbines

Abstract

Gas turbine combined cycle is widely used to achieve power balance in grids with uncertain renewable energy sources. To further enhance the rapid load-change capability of combined cycle plants, supercritical carbon dioxide (CO2) has been considered an alternative working fluid for the bottoming cycle. This paper presents a techno-economic investigation of a cascaded supercritical carbon dioxide cycle for typical gas turbines. This cascaded supercritical carbon dioxide cycle consists of a supercritical CO2 cycle and a transcritical CO2 cycle. A solving procedure is originally proposed to compare and optimize the combined cycles in eight gas turbines, whose power output and exhaust temperature ranges were 1.24–113.95 MW and 583–896 K, respectively. The results show that the cascaded supercritical CO2 combined cycle is thermodynamically favorable for small-scale gas turbines with high exhaust temperatures. The variations in the levelized cost of electricity indicate that the combined cycle with a small-scale gas turbine is more sensitive to the operation conditions of the bottoming supercritical CO2 cycle. Regarding the QD128 gas turbine (11.50 MW and 760 K) combined cycle, its multi-objective optimization results show that the optimal solution for techno-economic performance corresponds to a levelized cost of electricity of 0.0420 $/kWh and a net power of 19.701 MW. These findings also suggest that the cascaded supercritical CO2 combined cycle is a viable option for large-scale gas turbines.