Techno-economic investigations of supercritical CO2-based partial heating cycle as bottoming system of a small gas turbine

Supercritical CO2 (sCO2) cycles represent an innovative technology especially if applied for waste heat recovery from gas turbines. This work investigates the performance of the partial heating sCO2 cycle as the bottoming cycle of a 5 MW-class gas turbine. Particular attention is paid to the selection of both minimum CO2 pressure and temperature and use of the non-dimensional criterion named Acceleration Margin to Condensation is made to prevent the formation of liquid CO2 droplets at the inlet of the compressor. Moreover, in order to avoid heavily loaded turbomachinery, considerations about the machine Mach numbers result in possible limits for the maximum cycle pressure. Single-stage radial turbomachines are selected and their efficiency calculated according to Aungier's correlations by taking actual size and running conditions into account. Focusing on the net electric power produced by the bottoming cycle and on the corresponding specific cost, a number of investigations has been carried out. After setting a limit for the compressor Mach number, around 1600 kW can be recovered by the sCO2 bottoming cycle, though a techno-economic optimization would guide towards an optimum point with slightly more than 1500 kW of power output and a specific cost for the technology of around 2000 $/kW.