Modeling and simulation of small-scale Organic Rankine Cycle

The Organic Rankine Cycle (ORC) heat engine constitutes a very promising technology to recover waste heat (for instance from industry or from internal combustion engines) but also to exploit renewable energy sources (such as solar, biomass or geothermal energy). This seminar will emphasize how modeling and simulation tools could be used during the design stage of an ORC system in order to best define the architecture of the system as well as its control strategies. The first part of the seminar will focus on the steady-state modeling of ORC systems. Models of different types of expansion machines (scroll, piston, etc.) will be presented. The simulation model of the entire system will be built by associating the models of its different components. Calibration and validation of the proposed models, based on experimental data collected on different prototypes of small-scale ORC systems, will be discussed. Finally, it will be shown how the overall model can be used to size the components and to define the optimal operating conditions of the system. The second part of the seminar will present a dynamic simulation model of an ORC system built in Modelica language. First, the choice of latter language will be discussed. Then, the dynamic modeling of the heat exchangers, based on a finite volume approach, will be presented. The overall model will be finally used to investigate different control strategies (PID and Model Predictive Control) applied to a waste heat recovery ORC system.