Modeling and Simulation of a Thermoelectric Generator Using Bismuth Telluride for Waste Heat Recovery in Automotive Diesel Engines

Abstract

Waste heat recovery, using thermoelectric power technology, is a promising approach to reduce fuel consumption and CO2 emissions on passenger cars. However, possible application requires optimizing heat exchangers and defining adequate thermoelectric materials to improve efficiency. A dynamic model has been developed to investigate the application of a thermoelectric generator (TEG) for waste heat recovery in an automotive engine exhaust. The converted electrical energy is used to charge a 12 V battery. The model evaluates the amount of recovered energy over a prescribed drive-cycle. It also evaluates the effect of system integration on the TEG performances, such as fuel consumption, temperatures downstream of the TEG and the relative counter pressure. Experiments are done on both a thermoelectric module (TEM) test rig and a diesel engine test rig equipped with a TEG prototype. Simulations of steady operating points show good agreement with experimental data. The results show a maximum power of 42 W generated by the TEG, with a maximum power of 1.5 W per module (corresponding to TEM hot side temperature of 671 K and TEM cold side temperature of 354 K). At the end of the duty cycle, the energy recovered by the vehicle battery is around 27 kJ (7.5 Wh). The engine counter pressure exceeds 30 mbar when the mass flow rate is higher than 36 g s−1. The simulation results of temperatures, pressures, and output power show that the model can be used as a basis to develop a TEG with high performance that ensure safety operation of the engine and the after treatment system.