Investigation of waste heat recovery for automobile application based on a thermoelectric module

The article presents a brief discussion about issues of energy harvesting of waste heat generated during the operation of the SI (spark ignition) internal combustion engine (ICE). The available methods of implementation and the problems associated with them were presented. In recent years, there has been an increase in the significance of successful researches on new types of thermoelectric modules. Despite relatively low efficiency of the thermoelectric modules, a systematic growth in their interest is observed. Their application seems to be reasonable because of many advantages - mainly the simplicity. The paper contains the literature review in the subject of interest. For the purpose of this work, a test rig was designed and manufactured. The test rig consists of a single thermoelectric module and makes it possible to work in variety of operating conditions for different values of the exhaust gas flow rate and temperature. It is equipped with an automatic, servo controlled, movable element, which control direction of the exhaust gas flow and as a result changes the heat flux transferred via the thermoelectric module. This solution allows achieving the maximum power of the thermoelectric module in a wide range of ICE operating conditions and also allows adjusting operating parameters to actual working conditions of the whole system. The problems encountered during the construction of the test rig and the proposed solutions of practical implementation were described. Experimental research was conducted on a small size automobile petrol engine. The influence of electrical parameters at the output on the whole system was analysed. The results suggest that the actual thermoelectric module parameters, especially the thermal conductivity, vary from declared by the producer. Maximum achieved electric power output reached about 10 W from a single thermoelectric module (57 mm x 54 mm), which is nearly half of the declared value.