Investigation on the Heat-to-Power Generation Efficiency of Thermoelectric Generators (TEGs) by Harvesting Waste Heat from a Combustion Engine for Energy Storage

The present work explores a novel method of waste heat recovery (WHR) from the internal combustion (IC) engine and power generation using heat from hot exhaust gas (HEG) and thermoelectric generator (TEG). This system uses TEGs of aluminium oxide (Al2O3), bismuth telluride (Bi2Te3), lead telluride (PbTe3), and silicon germanium (SiGe) for the investigation of WHR and power generation. The experiments were conducted using a 5.9 kW diesel engine as a source of heat and a heat exchanger (HE) with fins. The parameters such as variation in temperature, rate of heat recovery, rate of power generation, and conversion efficiency of TEGs were analyzed by varying the load on the engine from 0% to 100% with steps of 25% and different zones of the heat exchanger, namely, zone 1, zone 2, zone 3, and zone 4. During the experiment, it was observed that zone 2 gives a high-temperature difference compared to zone 1, zone 3, and zone 4. TEG of bismuth telluride (Bi2Te3) increases the heat recovery rate overall compared to Al2O3, PbTe3, and SiGe throughout the load spectrum and operating conditions concerning different zones. The maximum power generation by TEGs of Al2O3, Bi2Te3, PbTe3, and SiGe was found to be 6.35 W, 7.18 W, 6.41 W, and 5.93 W at zone 2 while the engine was operated at 75% of load, respectively. Bi2Te3 gives the highest conversion efficiency compared to other TEGs irrespective of the working zones. The thermal energy-to-electrical energy conversion efficiency was maximum of about 7.8% given by the TEG of Bi2Te3 at zone 2 while the engine was operated at 75% of the load.