Selecting dry cooling system for supercritical carbon dioxide Brayton cycle: Thermoeconomic analysis

Abstract

In this work, the thermoeconomic performance of the direct and indirect dry cooling systems for supercritical CO2 (sCO2) Brayton cycle are compared. The design and off-design performance of both cycles are analyzed, and the optimization methods of dry cooling systems under off-design conditions are proposed. A nominal 20 MW recompression sCO2 power cycle operates at the ambient temperature of 298 K and the turbine inlet temperature of 873 K is used for the case study. The results show that under design conditions, the net power generation of the direct dry cooling sCO2 power cycle is about 562 kW lower than that of the indirect dry cooling sCO2 power cycle. Based on the annual power generation in three different locations, the levelized cost of electricity (LCOE) is selected as the economic indicator for the economic comparison of the cooling system. LCOE of the direct cooling system is 34.8 ¢/MWh lower in places where the ambient temperature is low and has large fluctuation. By contrast, LCOE of the indirect cooling system is 25.4 ¢/MWh lower in places where the ambient temperature is mild and the variation of the ambient temperature is small. The results of this paper indicated that both thermal performance and the climatic condition of the location of the power cycle need to be considered for the selection of the dry cooling system for the sCO2 power cycle. This work could provide deeper insight into the design and control of the dry cooling systems for the sCO2 power cycle.