Exhaust Heat Recovery Using Thermoelectric Generators: A Review

Abstract

With the major concern to increase the efficiency of internal combustion (IC) engines, various technologies and innovations have been implemented to improvise efficiency and reduction of emissions. Since 60–70% of the energy produced during combustion is rejected as heat through exhaust and coolant channels, it is important to recover that waste heat. Numerous technologies have been invented and applied to the diesel engine unit to harness the waste heat. One such is the use of solid-state device thermoelectric generator (TEG). In the late 1980s, many automobile manufacturers implemented automotive exhaust thermoelectric generators (AETEGs) in their respective vehicles, and since then, the work on AETEGs has picked at gradual pace. Advantages of using TEG are its noise-free operation, low failure rate and lack of moving components. However, it is not a very popular solution due to the low energy conversion efficiency (~6–8%) of thermoelectric modules and the incompetence to produce high power at low-temperature gradient. Engineers and researchers are basically working for improving the conversion efficiency of TEG modules by developing and doping semiconductors and optimization of the AETEG system to utilize and recover maximum heat available from the exhaust line by designing efficient heat exchanger systems, thus trying to improve its feasibility. This chapter covers the wide spectrum of feasibility of application of TEG modules in diesel engines with possible ways to utilize the generated power.