In this paper, the structure and control tasks are briefly summarized for ORC (Organic Rankine Cycle) based WHECSs (waste heat energy conversion systems). A control-oriented physical model is established for WHECSs. The energy conversion efficiency of ORC systems is investigated. A constrained model predictive controller is then presented to control WHECSs. Simulation results show that the exhaust gas can be utilized. In addition, the constrained predictive controller can achieve satisfactory performance for set-point tracking and disturbance rejection. (C) 2014 Elsevier Ltd. All rights reserved.