Prediction of the fuel economy potential for a skutterudite thermoelectric generator in light-duty vehicle applications

Thermoelectric generators (TEGs) have the characteristics of low maintenance, silent operation, stability, and compactness, which make them outstanding devices for waste heat recovery in light-duty vehicles. Significant strides have been made in the high temperature (300-800 degrees C) thermoelectric materials and recent work is beginning to translate those material improvements into TEG performance. Recently developed modules that incorporate new, competitive formulations of skutterudite form the basis for this study. Vehicular TEGs have not had real commercial applications yet and faced commercialization challenges. Simply estimating the fuel saving potential from the TEG output is not sufficient and due consideration must also be given to the system integration effects. Thus, a new approach for predicting the fuel saving potential of a vehicular TEG while also considering integration effects is developed in this paper. The prediction is based on a recently developed high temperature skutterudite thermoelectric modules [1]. Based on this method, the benefit of a skutterudite TEG is investigated by balancing the benefits with the added complexity of a TEG and improvement measures are explored. Based on two scenarios of the TEG integrated in different positions of a conventional light-duty vehicle, a semi-empirical model is developed, which includes a quasi-static vehicle model, a dynamic exhaust model, a dynamic coolant model, and a dynamic TEG model. Four integration effects: the additional mass, the power consumption of an electric circulation pump, the effect of exhaust back-pressure and the energy loss in the DC-DC converter, are studied in the semi-empirical model. The evaluation results show the TEG installation position has a significant influence on the fuel saving potential due to the higher quality of the exhaust gas. Placing the TEG closer to the exhaust manifold can increase fuel saving potential by 50%. The four integration effects taken together cause a 25% reduction of fuel saving potential. The energy loss in DC-DC convector and added weight are the main contributors to this reduction. An optimised design for the TEG installation operating under an optimised control strategy delivers a fuel consumption reduction of 4% over the constant-speed 120 km/h driving cycle.