TOWARDS THE OPTIMAL OPERATION OF AN ORGANIC RANKINE CYCLE UNIT BY MEANS OF MODEL PREDICTIVE CONTROL

asme-orc2015 Tracking Number 122

In this paper the optimal operation of an Organic Rankine Cycle (ORC) unit is investigated both in terms of energy production and safety conditions. Simulations on a validated dynamic model of a real regenerative ORC unit, are used to illustrate the existence of an optimal evaporating temperature which maximizes energy production for some given heat source conditions. This idea is further extended using a perturbation based Extremum Seeking (ES) algorithm to find online the optimal evaporating temperature. Regarding safety conditions we propose the use of the Extended Prediction Self-Adaptive Control (EPSAC) approach to constrained Model Predictive Control (MPC). Since it uses input/output models for prediction, it avoids the need of state estimators, making of it a suitable tool for industrial applications. The performance of the proposed control strategy is compared to PID-like schemes. Results show that EPSAC-MPC is a more effective control strategy as it allows a safer and more efficient operation of the ORC unit, as it can handle constraints in a natural way, operating close to the boundary conditions where power generation is maximized.