Optimization of the Number of Thermoelectric Modules in a Thermoelectric Generator for a Specific Engine Drive Cycle

Two identical commercial Thermo-Electric Modules (TEMs) were assembled on a plate type heat exchanger to form a Thermoelectric Generator (TEG) unit in this study. This unit was tested on the Exhaust Gas Recirculation (EGR) flow path of a test engine. The data collected from the test was used to develop and validate a steady state, zero dimensional numerical model of the TEG. Using this model and the EGR path flow conditions from a 30% torque Non-Road Transient Cycle (NRTC) engine test, an optimization of the number of TEM units in this TEG device was conducted. The reduction in fuel consumption during the transient test cycle was estimated based on the engine instantaneous Brake Specific Fuel Consumption (BSFC). The perfect conversion of TEG recovered electrical energy to engine shaft mechanical energy was assumed. Simulations were performed for a single TEG unit (i.e. 2 TEMs) to up to 50 TEG units (i.e. 100 TEMs). These TEG units were assumed to be connected mechanically and thermally in series. The simulation results showed that the reduction in fuel consumption with the increase in the number of TEG units was nonlinear and there was a limit to the fuel consumption reduction that could be achieved on the NRTC test case. The maximum fuel saving for this cycle was observed to be less than 3%. A TEG device consisting of 14 TEG units (28 TEMs) was found to recover up to 80% of the thermal energy in the EGR flow-path of the test engine.