An exergy composite curves approach for the design of optimum multi-pressure organic Rankine cycle processes

This work adopts the ECCs (exergy composite curves) approach to explore the potential for ORC (organic Rankine cycle) process improvements. The method is used to explore different ORC configurations supported by a mathematical model representing a generic multi-pressure ORC cascade and developed based on the principles of the ECCs method. The model facilitates interconnectivity at different temperature and pressure levels, also considering two types of turbines, namely an expansion and an induction turbine. It is employed to investigate the performance of two major ORC configurations, namely one considering independent pressure loops with an expansion turbine and the other considering pressure loops contacted through induction turbines. These configurations are updated with new features within an iterative procedure supporting the systematic identification of the optimum number of pressure loops together with several operating optimization parameters. The optimization is performed using an inclusive objective function, while the obtained results indicate ORC systems of high performance.