Abstract
Supercritical Brayton cycles have been considered as one of the technologies that present high thermal efficiencies in a wide range of energy conversion systems. Also, these systems can even increase their efficiency by incorporating a suitable bottoming cycle. In this article, a combined supercritical Brayton cycle with an Organic Rankine cycle (ORC) was analyzed. The influence of key system parameters such as the Brayton circuit high-pressure (Phigh), the turbine-1 inlet temperature (TIT), the turbine-1 efficiency ( ntnt<math> <msub><mrow><mi>n</mi></mrow> <mrow><mi>t</mi></mrow> </msub> </math> ), and the evaporation pressure ( PevapPevap<math> <msub><mrow><mi>P</mi></mrow> <mrow><mi>e</mi> <mi>v</mi> <mi>a</mi> <mi>p</mi></mrow> </msub> </math> ) on the economic indicators such as the Levelized Cost of Energy (LCOE), the Payback Period (PBP), the Specific Investment Cost (SIC), and net work ( ˙WnetW˙net<math> <msub> <mrow> <mover><mrow><mi>W</mi></mrow> <mrow><mo>˙</mo></mrow> </mover> </mrow> <mrow><mi>n</mi> <mi>e</mi> <mi>t</mi></mrow> </msub> </math> ) was studied. Besides, the effect of these parameters on the exergo-economic indicator rkrk<math> <msub><mrow><mi>r</mi></mrow> <mrow><mi>k</mi></mrow> </msub> </math> and the relative cost difference rkrk<math> <msub><mrow><mi>r</mi></mrow> <mrow><mi>k</mi></mrow> </msub> </math> were studied. Finally, a thermo-economic optimization of the proposed configurations was carried out. The study revealed that the turbine-1 inlet temperature (TIT) was the variable with the most significant effect on the economic and energy indicators of the configurations analyzed. The increase in the turbine temperature up to 850 °C caused a rise of 63.8% for both configurations. Also, the results revealed that the Brayton/SORC configuration presented the best economic performance compared to the Brayton/RORC system. The thermo-economic optimization revealed that temperatures above 800 °C and pressures between 25-30 MPa increase system performance. In addition, the Brayton/SORC configuration has a comparative reduced levelized energy costs and low payback periods, which makes it more attractive.