Economic comparison between sCO2 power cycle and water-steam Rankine cycle for coal-fired power generation system

Abstract

The supercritical carbon dioxide (sCO2) coal-fired power generation system has received great attention, but its economic characteristic is not well understood. Here, we present an economic comparison when using the sCO2 power cycle and the water-steam Rankine cycle. The triple-compression sCO2 cycle is adopted, incorporating overlap energy utilization over entire flue gas temperature range, intercooling and double reheating techniques. The heat-resistant steel materials of boiler are carefully selected to ensure its safe operation. The cost models of sCO2 boiler and recuperator are paid more attention. We show that the sCO2 power system attains the net power generation efficiency of 49.01%, which is higher than 48.12% for the advanced water-steam Rankine cycle system. Compared with water-steam system, the cost of sCO2 turbine decreases by 30.0%, but the cost of sCO2 recuperator seems to be one magnitude larger than that of USC heater, the cost of sCO2 boiler increase by 36.3%. Hence, the whole sCO2 power system increases the specific cost by 29.0%. Over an entire 30 years lifetime of the power plant, the levelized cost of electricity (LCOE) is 60.56 $/MWh for sCO2 power system, which decreases by 1.32% compared to water-steam system. Therefore, we declare that even though the fabrication cost increases, the sCO2 power system is preferable to the water-steam system. The specific cost of the sCO2 power system can be further decreased by optimization of the recuperator, which is a key component in the system.