Small-Scale ORC Energy Recovery System for Wasted Heat: Thermodynamic Feasibility Analysis and Preliminary Expander Design

The paper analyses the thermodynamic feasibility of an innovative Organic Rankine Cycle (ORC) recovery system. Among the many applications of this device, particular interest covers the application as bottoming systems for the exploitation of wasted heat from the exhaust gases of an ordinary ICE.The vehicle thermal source can be either a typical diesel engine (1400 cc) or a small gas turbine set (15-30 kW). The sensible heat recovered from the exhaust gases feeds the energy recovery system that can produce sufficient extra power to sustain the conditioning system and other auxiliaries. The concept is suitable for all types of thermally propelled vehicles, but it is studied here for automotive applications.The characteristics of the organic cycle-based recovery system are discussed, and a preliminary design of the main component, such as expander is presented. The main challenge are the imposed size and weight limitations that require a particular design. A possible system layout is analysed and the requirements for a prototypal application are investigated.