A thermoelectric generator in exhaust systems of spark-ignition and compression-ignition engines. A comparison with an electric turbo-generator

Approximately a third of the fuel energy in internal combustion engines is wasted through the exhaust gas. Thermoelectric generators have been employed in automotive engines to recover energy from the exhaust system. The purpose of this work is to broaden the knowledge of thermoelectric generators and help designers to evaluate of their implementation in light-duty vehicles. Several works have tested a thermoelectric generator in spark-ignition engines and others in compression-ignition engines. This work provides results from the same thermoelectric generator prototype in a spark-ignition and in a compression-ignition engine to study the actual difference in thermoelectric energy recovery potential of both sorts of engine. Thermoelectric generators are also compared with a promising turbine-based waste energy recovery technology (electric turbo-generators). Full-load curves are swept to study the performance of the thermoelectric generator under limit conditions. The effect of by-passing the thermoelectric generator to limit the pressure drops produced at full-load conditions is also analysed. A validated three-dimensional Computational Fluid Dynamics model of a thermoelectric generator built and tested supports the study.