ORC on tour: Integrated design of dynamic ORC processes and working fluids for waste-heat recovery from heavy-duty vehicles

Abstract

Organic Rankine Cycles (ORC) convert low temperature heat into power. To maximize conversion efficiency, both ORC process and working fluid have to be tailored to the specific application. Common solution approaches for the resulting integrated design of ORC process and working fluid are limited to steady-state applications. However, for applications in dynamic settings, steady-state design approaches can lead to suboptimal solutions due to the neglect of the dynamic behavior. In this work, we present an approach for the integrated design of ORC process and working fluid considering the dynamics. The approach is based on the Continuous-Molecular Targeting–Computer-aided Molecular Design (CoMT-CAMD) framework. Herein, the physically based Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) is used as thermodynamic model. To capture the ORC behavior under dynamic conditions, dynamic models for the ORC equipment are integrated into the process model. The result is an optimal control problem (OCP) yielding an optimal working fluid and the corresponding optimal process control for a given dynamic input. This so-called dynamic CoMT-CAMD approach is applied to an ORC for waste-heat recovery on a heavy-duty vehicle. Whereas steady-state design approaches fail, the presented approach identifies the optimal working fluid and the corresponding optimal control of the ORC process. © 2019 Elsevier B.V.