Current Possibilities of Thermoelectric Technology Relative to Fuel Economy

To practically apply thermoelectric technology in commercial use, improved performance in thermoelectric materials are said to be necessary in general. However, there is no frame of reference that illustrates how far away from optimal performance a material may be, nor is there any information indicating outstanding issues or possible applicable approaches that could improve system performance other than improvement in performance of thermoelectric. Application of thermoelectric in automobiles should require special design philosophy compared to general applications, but there is not enough information pointing out these special requirements. To determine essential elements in thermoelectric technology to be used specifically for automobile heat recovery applications, we have evaluated the effect of a thermoelectric system on fuel economy adopting commercially available thermoelectric materials and typical industrial techniques using a 2.0-liter midsize gasoline vehicle as a study case. From our investigation, only very modest improvements in fuel economy were ascertained under various drive cycles, LA4, SC03, HWY, and US06. Essential elements of the thermoelectric heat recovery system that were identified included improvements to the performance of the thermoelectric materials at working temperatures, heat exchanger, and joint technique of elements to build module, along with realization that effort will be needed to obtain higher exhaust temperature without reducing efficiency of engine. In addition, from an application point of view, significant differences in CO₂ emissions were found between the different types of vehicles investigated.