Multi-criteria selection and thermo-economic optimization of Organic Rankine Cycle system for a marine application

Abstract

The purpose of this work is to investigate the possibility of exploiting the low-temperature thermal energy released from marine propulsion engines by an Organic Rankine Cycle system (ORCs) and determine an optimal design of such a system for a particular engine as an example. At first, taking into consideration thermodynamic properties of several fluids and regulations applicable in the marine environment, proper organic Rankine fluids are selected for further consideration. Alternative system configurations with different fluids are assessed with a multi-criteria approach based on performance indexes. The system with the highest value of the Composite Performance Indicator is further studied. The optimal synthesis, design and operation is determined with maximization of the Net Present Value as the objective function. The optimization problem is solved with a combination of a Genetic Algorithm and a Sequential Quadratic Programming Algorithm. Furthermore, a sensitivity analysis is performed with respect to important parameters. It is interesting to note how the optimal synthesis (configuration) of the system changes automatically with changing operation profile of the propulsion engine. The presentation closes with suggestions for further work.