Thermoelectric generators (TEGs) make use of the Seebeck effect in semiconductors for the direct conversion of heat to electrical energy. The possible use of a device consisting of numerous TEG modules for waste heat recovery from an internal combustion (IC) engine could considerably help worldwide efforts towards energy saving. However, commercially available TEGs operate at temperatures much lower than the actual operating temperature range in the exhaust pipe of an automobile, which could cause structural failure of the thermoelectric elements. Furthermore, continuous thermal cycling could lead to reduced efficiency and lifetime of the TEG. In this work we investigate the long-term performance and stability of a commercially available TEG under temperature and power cycling. The module was subjected to sequential hotside heating (at 200°C) and cooling for long times (3000 h) in order to measure changes in the TEG's performance. A reduction in Seebeck coefficient and an increase in resistivity were observed. Alternating-current (AC) impedance measurements and scanning electron microscope (SEM) observations were performed on the module, and results are presented and discussed.

Thermoelectric elements convert a part of thermal power into electrical, developing the Seebeck effect. A number of thermoelectric elements can be connected electrically in parallel and/or in series shaping a thermoelectric generator (TEG) device. The generator efficiency, η, is determined by comparing the amount of electricity produced (PTEG) to the total amount of heat induced (QH). The possible use of such a device for the recovery of wasted heat can considerably help the world effort for energy savings and the reduction of greenhouse gases.A measuring system and a modeling approach which takes into account the thermal contact resistances have been developed, allowing the characterization of TEG devices under various loads and temperature gradients and thus, the evaluation of material properties. The model was applied on investigating the expected gained power and efficiency, at different places of the exhaust pipe of an intermediate size car with the use of conventional thermoelectric elements. Furthermore, the reliability of a TEG module was examined and the repercussion on fuel consumption is discussed.

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In this work, thermoelectric device was made, using a commercially available ThermoElectric Generator (TEG), in order to measure the gained power and efficiency for longterm performance. The module was subjected to sequential hot side heating at 200 o C (392 0 F), and cooling for 6000 cycles, in order to measure the TEG's power and EMF change. A 14% increase in the TEG's material resistance was found, as well as a 5% reduction in the Seebeck coefficient. After the experiment, the module was disassembled and thermoelectric p-and nlegs were examined using IR spectroscopy.