Performance analysis and optimization of a combined system based on recompression transcritical CO₂ power cycle and transcritical ejector refrigeration cycle for waste heat recovery of gas turbine

A novel combined system is proposed for waste heat recovery of gas turbine (GT), in which the exhaust gas is sequentially employed to drive a recompression transcritical CO₂ power cycle (RTCPC) and a transcritical ejector refrigeration cycle (TERC) with CO₂‑based mixture. The cooling output from the TERC serves to condense the CO₂ in the RTCPC, mitigating the condensation challenge in warm regions. Detailed models covering thermodynamics, economics, and environment are formulated to conduct performance assessment and comparative study. Then the analysis of the crucial cycle parameters is conducted to identify their effects on system performance. Thereafter, the three-objective optimization is implemented, targeting the maximization of net power output and the minimizations of unit net power cost and associated CO₂ emission per net power. The results reveal that the proposed combined system outperforms the recompression supercritical CO₂ Brayton cycle (RSCBC) by delivering a 55.2 % gain in net power output, a 22.9 % saving in unit net power cost, and a 43.8 % cut in CO₂ emissions per net power. According to the three‑objective optimization, the optimal trade‑off yields a net power output of 2249.97 kW, a unit net power cost of 0.0495$/kWh, and associated CO₂ emission per net power of 0.3741kg_CO2/kWh. The present study provides contributions to waste heat recovery from gas turbine and can be extended to other flue gases with similar temperature levels.