Optimization and thermodynamic performance analysis of a power generation system based on geothermal flash and dual-pressure evaporation organic Rankine cycles using zeotropic mixtures

Organic Rankine cycle is a power generation system for the widespread use of the medium to low-enthalpy thermal energy. Using the dual-pressure evaporation cycle and zeotropic mixtures are important approaches to increase the efficiency of an organic Rankine cycle system. This work proposes a thermodynamic analysis and optimization of a flash-binary geothermal cycle for power generation aims where the binary cycle used is a dual-pressure organic Rankine cycle in which different mixtures of zeotropic fluids are used as the working fluid. Integration of dual-pressure ORC and zeotropic mixtures presents the remarkable capability to combine their superiority and further enhance the system performance considerably. The superiority of the proposed system, which combines the advantages of zeotropic mixtures with DORC positive aspects, is revealed through the energy and exergy analysis. Also, the particle swarm optimizer (PSO) is employed to optimize the net output power as the objective function. The results reveal some precious facts; for instance, the overall thermal and exergy efficiencies are obtained 18.23% and 62.37%, respectively for the base case. However, the optimized results demonstrate that the Pentane (0.539)/Cis-2-butene (0.461) and Pentane (0.527)/Trans-2-butene (0.473) combinations hold the maximum energetic efficiency of 18.43% and 18.41%, respectively. The net output powers for these combinations are 5983.19 kW and 6011.17kW, respectively. Also, a comparative analysis of the presented system with those from literature illustrates that the presented power generation system generates more power and shows higher energetic and exergetic efficiency. (C) 2019 Elsevier Ltd. All rights reserved.