Thermoelectric materials and heat exchangers for power generation - A review

Around 60-70% of the fuel energy in an internal combustion engine is lost as waste heat through engine exhaust and coolant. Hence, waste heat recovery techniques can be used to increase the efficiency of the engine. Thermoelectric systems are widely used for converting heat energy to electric energy. A considerable attention of researchers has been drawn by the thermoelectric generator, for the waste heat recovery from engine exhaust. The thermoelectric generator is one of the promising green energy source and the most desirable option to recover useful energy from engine exhaust. A high-efficiency heat exchanger, which is an integral part of the thermoelectric generator, is necessary to increase the amount of heat energy extracted from engine exhaust at the cost of acceptable pressure drop. The present work is a summary of thermoelectric materials, and heat exchanger studies on heat transfer rate, thermal uniformity, and pressure drop. The heat exchangers with different internal structures enhance heat transfer rate and thermal uniformity, which increase the power output and the conversion efficiency of the thermoelectric generator. The presence of flow-impeding inserts/ internal structures results in an adverse increase in pressure drop and has a negative effect on the performance of waste heat source.