Fuel saving potential analysis of bifunctional vehicular waste heat recovery system using thermoelectric generator and organic Rankine cycle

Organic Rankine cycle (ORC) and thermoelectric generator (TEG) have both been identified as reliable waste heat recovery (WHR) technologies, although they are different in energy conversion efficiency, volume size and operating temperatures. The combined thermoelectric generator and organic Rankine cycle (TEG-ORC) system enables TEG and ORC to be complementary. In this study, a novel TEG-ORC system is proposed in a light-duty vehicle application. Regarding the space limitations in vehicles, the proposed system effectively uses existing components in the car to reduce the overall size. In addition, the TEG-ORC is a bifunctional system, which not only works for exhaust energy recovery, but also acts as a heating device for fast engine oil warm-up. The fuel saving potential of the TEG-ORC system is assessed against that of the baseline, standalone TEG and standalone ORC systems. The results show that TEG-ORC system effectively reduces the engine oil warm-up time and system hysteresis time of WHR. A significant increase of fuel saving potential is obtained when TEG and ORC are combined, which is not achievable by a single TEG or a single ORC. This seems a breakthrough for waste heat recovery in vehicle applications since the proposed TEG-ORC system is compact and has an acceptable fuel saving performance.