• Energy Research

Thermoelectric generators (TEGs) often use plate-fin heat sinks as cold side heat exchangers under forced convection. The available net electrical power obtained from these TEGs corresponds to that generated (Seebeck effect) minus that consumed (cooling fan). Generation and self-consumption have different trends as a function of the air flow speed, so a maximum of the net electrical power is expected when varying the cooling flow rate. Here, a semi-analytical model was developed to predict the maximum net electrical power of a single TEG module with a plate-fin heat sink with non-bypassed forced convection. The model was successfully validated with experimental data. It was applied to determine the heat sink design (fin thickness and fin-to-fin distance) that optimized the net electrical power for given values of hot source temperature, TEG properties, and duct cross-section. Numerical results indicated that the optimal dimensions of the plate-fin heat sink depended, among others, on the TEG effective properties. For a given TEG, the net output power was less sensitive to changes in fin thickness than in fin spacing. The optimal heat sink designs predicted by the model for the cases studied had fin thicknesses of 0.32 and 0.44 mm with fin-to-fin distances of 1 mm. This work was partially funded by the University of Girona under grant MPCUdG2016-4 Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier

Thermoelectric generators (TEGs) often use plate-fin heat sinks as cold side heat exchangers under forced convection. The available net electrical power obtained from these TEGs corresponds to that generated (Seebeck effect) minus that consumed (cooling fan). Generation and self-consumption have different trends as a function of the air flow speed, so a maximum of the net electrical power is expected when varying the cooling flow rate. Here, a semi-analytical model was developed to predict the maximum net electrical power of a single TEG module with a plate-fin heat sink with non-bypassed forced convection. The model was successfully validated with experimental data. It was applied to determine the heat sink design (fin thickness and fin-to-fin distance) that optimized the net electrical power for given values of hot source temperature, TEG properties, and duct cross-section. Numerical results indicated that the optimal dimensions of the plate-fin heat sink depended, among others, on the TEG effective properties. For a given TEG, the net output power was less sensitive to changes in fin thickness than in fin spacing. The optimal heat sink designs predicted by the model for the cases studied had fin thicknesses of 0.32 and 0.44 mm with fin-to-fin distances of 1 mm. This work was partially funded by the University of Girona under grant MPCUdG2016-4 Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier

Abstract The need to reduce both energy consumption and greenhouse gas emissions has boosted the interest in using thermoelectric generators (TEGs) as waste heat energy harvesters. High-power TEGs are usually formed by an array of commercial thermoelectric modules (TEMs). Recent studies have analyzed the effects of using different types of electrical connections between TEMs in TEGs to produce electric power, but the effects of using different thermal configurations between TEMs have not been fully examined. Here, both electrical and thermal effects have been investigated using a numerical model developed with GT-SUITE software, which has been validated with laboratory data. TEGs with a number of TEMs between 1 and 100 distributed in different patterns along the exhaust pipe have been simulated under three engine regimes. For a given TEM geometrical pattern and engine regime, results prove the existence of an optimum number of TEMs, beyond which the total extracted power decreases. A mixed spatial distribution of TEMs generates more power than either the pure series or the pure parallel topologies. Finally, a methodology is proposed to choose an appropriate pattern of TEMs for a TEG installed in a system with variable regimes. This method is applied to a mid-size automotive diesel engine.

Abstract The need to reduce both energy consumption and greenhouse gas emissions has boosted the interest in using thermoelectric generators (TEGs) as waste heat energy harvesters. High-power TEGs are usually formed by an array of commercial thermoelectric modules (TEMs). Recent studies have analyzed the effects of using different types of electrical connections between TEMs in TEGs to produce electric power, but the effects of using different thermal configurations between TEMs have not been fully examined. Here, both electrical and thermal effects have been investigated using a numerical model developed with GT-SUITE software, which has been validated with laboratory data. TEGs with a number of TEMs between 1 and 100 distributed in different patterns along the exhaust pipe have been simulated under three engine regimes. For a given TEM geometrical pattern and engine regime, results prove the existence of an optimum number of TEMs, beyond which the total extracted power decreases. A mixed spatial distribution of TEMs generates more power than either the pure series or the pure parallel topologies. Finally, a methodology is proposed to choose an appropriate pattern of TEMs for a TEG installed in a system with variable regimes. This method is applied to a mid-size automotive diesel engine.

The need for more sustainable mobility promoted research into the use of waste heat to reduce emissions and fuel consumption. As such, thermoelectric generation is a promising technique thanks to its robustness and simplicity. Automotive thermoelectric generators (ATEGs) are installed in the tailpipe and convert heat directly into electricity. Previous works on ATEGs mainly focused on extracting the maximum amount of electrical power. However, the back pressure caused by the ATEG heavily influences fuel consumption. Here, an ATEG numerical model was first validated with experimental data and then applied to investigate the effects that modifying the main ATEG design parameters had on both fuel economy and output power. The cooling flow rate and the geometrical dimensions of the heat exchanger on the hot side and the cold side of the ATEG were varied. The design that produced the maximum output power differed from that which maximized fuel economy. Back pressure was the most limiting factor in attaining fuel savings. Back pressure values lower than 5 mbar led to a < 0.2% increase in fuel consumption. In the ATEG design analyzed here, the generation of electrical output power reduced fuel consumption by a maximum of 0.5%.

The need for more sustainable mobility promoted research into the use of waste heat to reduce emissions and fuel consumption. As such, thermoelectric generation is a promising technique thanks to its robustness and simplicity. Automotive thermoelectric generators (ATEGs) are installed in the tailpipe and convert heat directly into electricity. Previous works on ATEGs mainly focused on extracting the maximum amount of electrical power. However, the back pressure caused by the ATEG heavily influences fuel consumption. Here, an ATEG numerical model was first validated with experimental data and then applied to investigate the effects that modifying the main ATEG design parameters had on both fuel economy and output power. The cooling flow rate and the geometrical dimensions of the heat exchanger on the hot side and the cold side of the ATEG were varied. The design that produced the maximum output power differed from that which maximized fuel economy. Back pressure was the most limiting factor in attaining fuel savings. Back pressure values lower than 5 mbar led to a < 0.2% increase in fuel consumption. In the ATEG design analyzed here, the generation of electrical output power reduced fuel consumption by a maximum of 0.5%.

Solar thermoelectric generators (STEGs) are a promising technology to harvest energy for off-grid applications. A wide variety of STEG designs have been proposed with the aim of providing non-intermittent electrical generation. Here, we designed and tested a STEG 0.5 m long formed by nine commercial thermoelectric generator modules and located at ground level. Data were used to validate a numerical model that was employed to simulate a one-year cycle. Results confirmed the very high variability of energy generation during daylight time due to weather conditions. By contrast, energy generation during night was almost independent of atmospheric conditions. Annual variations of nighttime energy generation followed the trend of the daily averaged soil temperature at the bottom of the device. Nighttime electrical energy generation was 5.4 times smaller than the diurnal one in yearly averaged values. Mean energy generation values per day were 587 J d−1 (daylight time) and 110 J d−1 (nighttime). Total annual energy generation was 255 kJ. Mean electrical output power values during daylight and nighttime were 13.4 mW and 2.5 mW, respectively. Annual mean output power was 7.9 mW with a peak value of 79.8 mW.