Thermoeconomic analysis of a combined supercritical CO2 reheating under different configurations of Organic Rankine cycle ORC as a bottoming cycle

Guillermo Valencia Ochoa; Jorge Duarte Forero; Jhan Piero Rojas

doi:10.1016/j.heliyon.2022.e12230

Thermoeconomic analysis of a combined supercritical CO₂ reheating under different configurations of Organic Rankine cycle ORC as a bottoming cycle

Heliyon. 2022 Dec 14;8(12):e12230. doi: 10.1016/j.heliyon.2022.e12230. eCollection 2022 Dec.

Authors

Guillermo Valencia Ochoa¹, Jorge Duarte Forero¹, Jhan Piero Rojas²

Affiliations

¹ Engineering Faculty, Mechanical Engineering Department, Universidad del Atlántico, Carrera 30 Número 8-49, Puerto Colombia, Barranquilla 080007, Colombia.
² Engineering Faculty, Civil Engineering Department, Universidad Francisco de Paula Santander, Avenida gran Colombia, No. 12E-96, Cucuta 540003, Colombia.

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 ( $n_{t}$ ), and the evaporation pressure ( $P_{e v a p}$ ) on the economic indicators such as the Levelized Cost of Energy (LCOE), the Payback Period (PBP), the Specific Investment Cost (SIC), and net work ( ${\dot{W}}_{n e t}$ ) was studied. Besides, the effect of these parameters on the exergo-economic indicator $r_{k}$ and the relative cost difference $r_{k}$ 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.

Keywords: Energetic efficiency; Multi-objective optimization; Organic Rankine cycle; Supercritical dioxide carbon Brayton cycle; Thermo-economic indicator.