Influence of the Proportion of the Working Fluid Renewal on Semi-closed Oxy-Fuel sCO₂ Power Cycles Efficiency Indicators

The article explores four principal configurations of a semi-closed sCO₂ power cycle with zero emissions. A comparison n is made of the thermodynamic and environmental-energy indicators of sCO₂ cycles both among themselves and among widely used thermal power plants: gas turbine units, steam power plants, and combined cycle power plants. The novelty of the work lies in the analysis of the influence of the proportion of the working fluid renewal during oxy-fuel combustion in the combustion chamber on the efficiency indicators. The proportion of the working fluid renewal is one of the characteristic features of sCO₂ power cycles and is for the first time identified as an independent factor for analysis. Using calculation methods based on classical equations of material and heat balances, the thermodynamic efficiency of sCO₂ cycles, specific fuel consumption for electricity production, energy consumption for own needs, and carbon dioxide emissions are determined. It was determined that the proportion of the working fluid renewal of 2.7–5.5% has a direct impact on all efficiency indicators, since it affects the material and heat balance of the regenerative system. It was revealed that sCO₂ power cycles have a gross efficiency of 65–73%, surpassing all traditional power units with CCS, but in terms of net efficiency, they are inferior to advanced combined cycle plants. However, sCO₂ power plants have energy consumption for auxiliary systems of 29.5–35%. The results can be used to determine the most preferable option for the development of fossil fuel energy technologies with CO₂ capture under decarbonization conditions.