Performance Analysis of High-Efficiency Supercritical CO2 Power Cycles Using Recompression

Abstract

System simulation, parametric analysis, and exergy analysis were performed to identify the advantages and drawbacks of recompression in the direct-fired supercritical carbon dioxide (sCO2) power cycle. In a parametric investigation, the recompression ratio, turbine inlet temperature (TIT), and pressure ratio were changed, and the obtained values for the efficiency of the power cycle were compared. The TIT was varied between 600 °C and 1600 °C, revealing that recompression is highly effective for lower TIT values but is less effected at higher TIT values. For TITs above 1400 °C, the recompression cycle obtains almost no increase in efficiency. Different optimal recompression ratios were obtained for the different pressure ratios between the high- and low-pressure sides. Exergy analysis reveals that exergy destruction occurs primarily in the oxy-fuel combustor due to a chemical reaction and mixing of the high recirculation fluid. Higher TIT decreases the exergy destruction of the oxy-fuel combustor, but increases the exergy destruction in the lower temperature recuperator, and is not always favorable for obtaining efficiency improvements.