Thermodynamic optimization and comparative economic analysis of four organic Rankine cycle configurations with a zeotropic mixture

The current paper aims to compare the four fundamental Organic Rankine Cycle (ORC) structures with a zeotropic mixture of Pentane and Hexane, utilized as the working fluid. The studied variants of ORCS include simple single and dual-pressure ORCs alongside their recuperative configurations. Each configuration is optimized in different mole fractions to obtain the parameters that generate the highest power. The energy and exergy efficiencies are then calculated and compared besides a detailed view of the exergy destructions of each component. Next, the Levelized Cost of electricity is calculated for each mole fraction to carry out the thermoeconomic analysis. The optimum mole fractions of each structure are then obtained to conduct a techno-economic analysis to elaborate more on the superiority of cycles than each other, considering both economic and thermodynamic results. According to the results, the recuperative dual-pressure ORC is the most efficient and has the most generated power (2038 kW), while the other's performances decline regarding their complexity level. Its performance is found to be more than 16% better than the simple ORC structure which proves a significant improvement. In addition, using a zeotropic mixture can boost the cycle performance and reduce the exergy destructions. Moreover, it is revealed that the dual-pressure ORC is not an economically acceptable option due to its relatively lower net present value, 4.29 M$, while the recuperative structures result in a NPV of 4.53 M$ after the 20-year lifetime. Finally, by conducting a sensitivity analysis, it is concluded that either of the recuperative configurations can be of more desire depending on the power demand and electricity price.