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

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.