Design and development of a test rig for the performance evaluation of automotive exhaust thermoelectric generator

In an automotive engine, around 40% of the heat produced by fuel combustion is wasted through exhaust gas. Conversion of part of this heat into electricity by a thermoelectric generator has the potential to improve the vehicle fuel efficiency. Developing an automotive exhaust thermoelectric generator (AETEG) for such conversion involves many challenges. The performance evaluation of the generator at the system level is one among them. The present work describes the design and development of a test rig for the evaluation of various characteristics of an AETEG. The test rig simulates the typical thermo-physical conditions of the engine of a light-duty vehicle using hot air. The temperature and the mass flow rate of the hot air entering the AETEG can be varied independently. The instruments provided in the system can measure the pressure drop, voltage-current and power-current characteristics of the AETEG under various inlet hot air conditions. An AETEG designed and assembled containing 40 modules each of 5 W capacity is tested for its performance in this test rig. Under the highest inlet temperature of 385°C and mass flow rate of 255 kg/h tested, the AETEG showed less than 1 kPa pressure drop with maximum open circuit voltage of 157 V and power of 27 W. The test rig could successfully map the temperature non-uniformity in the hot side heat exchanger and its effect on power output from each module. The overall efficiency of AETEG is only 0.4% mainly due to poor efficiency of the hot side heat exchanger.