Multi-objective optimization of low-temperature waste-heat ORC power generation systems

Owing to the limitations of single-objective optimization on existing organic Rankine cycle (ORC) power generation system, a multi-objective optimization design was conducted for the low-temperature waste-heat ORC power generation system from the point of view of thermodynamic and economic aspects, by taking maximum exergy efficiency and minimum investment of system as the objective functions, selecting 5 key thermal parameters as the decision variables, such as turbine inlet temperature, turbine inlet pressure, pinch temperature difference, approach temperature difference and condenser temperature difference, etc., optimizing the ORC power generation system with working fluids R123, R245fa and isobutane using non-dominated sorting genetic algorithm (NSGA-II), and subsequently Pareto optimal solutions were obtained, from which the optimum design solution with optimal combinations of system thermal parameters was selected with the aid of an ideal point. Results show that under the given waste heat conditions, R245fa is the optimal working fluid in consideration of both the thermodynamic performance and the economic efficiency. The optimum solution shows an optimal exergy efficiency of 10.37% and a minimum investment of 4558400 Yuan.