Comparing the recovery performance of different thermoelectric generator modules in an exhaust system of a diesel engine both experimentally and theoretically

In this study, a thermoelectric recovery system was designed to convert the exhaust waste heat of an internal combustion diesel engine directly to electric power and the performance was measured at different engine speeds in the unloaded state. The performances of two different thermoelectric generators were compared in a system designed using four modules. Maximum 0.92 W power was obtained for four modules at 3500 r/min, at an area of 0.0016 m(2). Internal resistance of modules has increased according to the engine speed. The highest internal resistance obtained during the experiments is 11.69 omega at engine speed of 3500 r/min. The characteristics of the overall thermoelectric generator performance is coherent with the analysis model. In the current graph according to engine speed, the maximum absolute error is calculated for modules TEG 12-8 and TEG1-199 as 0.010 and 0.044, respectively (at experimented 3500 r/min). To charge the battery under maximum power point conditions, 133 thermoelectric modules were required (TEG1-199). Maximum power transfer is obtained when the load resistor is connected in parallel at 10 omega. It is seen that modular structure thermoelectric generators are more important alternative than Rankine cycle system in terms of waste heat recovery, despite thermoelectric system has low efficiency.