Thermodynamic and technoeconomic optimization of Organic Rankine Cycle systems

The optimization of an organic Rankine cycle is a challenging task that cannot be tackled without the aid of numerical tools for plant simulation and optimization. The large availability of various working fluids, the possibility of adopting several plant layouts, and the need to consider many thermodynamic, technological, and economical aspects lead to a challenging design optimization problem. This chapter describes the most important steps in optimizing the design of organic Rankine cycles. First, general criteria for selecting the best working fluid and the best cycle configuration for a set of the most relevant applications are thoroughly discussed. Moreover, useful guidelines are provided for the definition of the design optimization problem, its objective function, the decision variables, and the constraints. Then, the available simulation and optimization approaches and algorithms are critically reviewed with respect to their suitability for the optimization of power cycles. Finally, three test cases are presented to highlight the importance of optimization in the development of efficient and profitable organic Rankine cycles for geothermal heat sources, biomass-fired boilers, and waste heat recovery.