Supercritical CO2 power systems offer significant power density advantages along with high efficiencies, compared to traditional Rankine or Brayton cycles. Of the several viable configurations, the recompression cycle has higher efficiency compared to the simple recuperated cycle for source temperatures above 500°C. It also provides a good trade-off between efficiency and plant complexity. This paper explores the dependence of critical operational parameters on source and sink-temperature, which is then used as a means to generate guidelines for developing recompression sCO2 power plants. The maximum source temperature in the analysis is restricted to 565°C to take advantage of the existing materials and technologies associated with industrial steam turbines. However, the methodology described herein is applicable for any other source temperature range.
An important source of thermal efficiency degradation in power plants is attributable to heat exchangers. Analysis presented in this work directly relates the optimum operational parameters of the recompression cycle to the operation of the low temperature recuperator. Thermodynamic analysis confirms that a recompression fraction of 0.25 and pressure ratio of 2.5 is as an optimum design point for the recompression cycle. The penalty in efficiency and power while operating the plant in off-design conditions for a fixed recompression fraction and pressure ratio is highlighted.