Side Of Thermoelectric Generator Research Articles

Liquid metal-enhanced thermoelectric generator for high-temperature thermal harvesting

It is a challenge to achieve high output power of the thermoelectric generator (TEG) for high-temperature waste heat recovery due to the working fluids with low thermal conductivity (such as air) or low tolerance of temperature (water or oil). In this paper, the gallium-based liquid metal (LM) with a high boiling point (>1000 ℃) and thermal conductivity (>20 W/mK) are introduced to significantly enhance heat charging and discharging at the hot/cold sides of TEG. We also developed an electromagnetic induction pumping method for the effective LM-driven flow at high temperatures. A three-dimensional coupling multi-parameter optimization simulation model of LM-based TEG was developed to reveal the internal heat transfer and power generation mechanism for clarifying the impact factors of the performance. The results have shown that the power generation capacity can be effectively improved by increasing the inlet temperature (Thot-in). It is worth noting that the temperature difference (ΔT) of the TEG module is severely limited by the thermal resistance (Rcapacity) of the LM heat capacity, such as, when the flow rate of 2 L/min, the Rcapacity accounts for 90.6 % (0.020 ℃/W). It is easier to achieve a larger open circuit voltage by increasing the height of the thermoelectric leg, but the Pmax is constantly weakened. Compared with Xceltherm 600 and Solar salt, LM heat transfer fluid has more obvious advantages in enhancing the power generation performance of the system. The LM-based TEG experiment platform was established to study heat transfer and power generation characteristics. The results have demonstrated that good consistency was proved by comparing experimental and numerical data. And the Pmax of the LM-based TEG system is 0.16 W/cm2 at ΔT of 136 ℃. LM-based TEG can open new perspectives for broad applications in high-temperature waste heat recovery.

Impact of heat guide structure on the power generation performance of integrated cavity-free micro thermoelectric generators

The performance of a cavity-free micro thermoelectric generator (TEG) consisting of Si nanowires (Si-NWs) is investigated in this research. In the cavity free structure, one side of TEG is heated by a structure of a metal overlayer, called the Heat Guide (HG), to supply heat selectively to specific microregions within the device. Thus, heat energy flows in the perpendicular direction, which forms steep a temperature gradient in the NWs. However, the performance can be varied by varying the thickness of the HG. In this work, the impact of the HG structure of an integrated TEG upon the power generation performance was experimentally demonstrated. Higher metal HG thickness and thick interlayer dielectric (ILD) thickness show higher power generation performance with the integrated device.

Integration of thermal insulation and thermoelectric conversion embedded with phase change materials

The thermoelectric effect can convert waste heat into electricity. The present work presents an integrated system of Thermoelectric Generators (TEG) and Phase Change Materials (PCMs) for thermal insulation of high-speed vehicles, where high heat fluxes of large fluctuations make thermal protection and energy harvest challenging. A single-stage thermoelectric generator is prepared with phase-change materials embedded to absorb and convert excessive heat. The performance is evaluated experimentally and numerically, between which a reasonable agreement is observed. The maximum temperature at the outside surface is reduced by 200 K, and the temperature curves are flattered. Furthermore, two-stage and two-segment integrated systems are numerically evaluated, generating a data set of thermoelectric performance. An artificial neural network is developed for prediction and a genetic algorithm is employed for optimization. The maximum specific power can be improved to 570 W/m2 in the two-segment system, while the temperature variation at the hot side of TEG in the two-stage system can be reduced to 230 K. Finally, a discussion on the effects of PCMs parameters is performed. Overall, the present work not only demonstrates the feasibility of such an integrated system but also illustrates the whole procedure of the predictions and optimizations. This could inspire more development for advanced integrated systems for thermal management.

Experimental and numerical investigation on a radiative cooling driving thermoelectric generator system

Thermoelectric (TE) technology and radiative sky cooling (RSC) technology have proven to be a promising and green way to harvest energy from the environment. Combining RSC technology with Thermoelectric generator (TEG) device for passive power generation at night is meaningful and remains a challenge. Here, a radiative sky cooling driving thermoelectric generator (RSC-TE) system integrated by a doped modified TiO2/PMMA radiative cooling film, a commercial TEG, and an aluminum heat sink is developed, with a simple structure, low cost and high efficiency. The thermal-electrical performance of the RSC-TE system was evaluated through a consecutive nighttime experiment. Experimental results show that the temperature of the cold side of the TEG in contact with the radiative cooler is 2.7–4.2 °C lower than the ambient temperature, and the temperature difference between the hot and cold sides of TEG is 2.3–3.2 °C. The temperature difference at 00:00 can reach 2.5 °C, which corresponds to an open circuit voltage of 87 mV. Furthermore, a 3D model has been established by COMSOL software to investigate the effects of different environmental parameters and component-related parameters on system performance, which has guiding significance for the improvement and optimization of the experimental setup. This study can provide a new thinking and some practical guidelines for the design and application of the RSC-TE system.

A comprehensive investigation of PCM based annular thermoelectric generator for energy recovery: Energy conversion characteristics and performance evaluation

Annular thermoelectric generators (ATEG) are increasingly attracting attention and are pivotal in thermal energy recovery due to their unique characteristics, which can be perfectly adapted to cylindrical heat sources. Considering the efficient thermal management and power generation of thermoelectric generator (TEG), phase change material (PCM) can be integrated with the cold side of TEG as a favourable cooling medium to meet its functional requirements. However, previous studies have focused on the intrinsic connection between flat-plat TEG and PCM, while the impact of PCM on ATEG has not been systematically explored. In the present study, an annular thermoelectric generator with PCM (ATEG-PCM) under a pulsed heat source is proposed, and its dynamic characteristics and energy distribution are evaluated. The effects of PCM parameters such as height, latent heat and melting temperature are comprehensively explored from multi-index, including PCM temperature, liquid fraction, temperature difference, output power, energy and exergy efficiencies. Furthermore, a comparative investigation of ATEG-PCM, PCM-ATEG where PCM is applied on the hot side, and ATEG without PCM is further carried out to clarify the coupled mechanism of PCM on thermal management and power generation enhancement of ATEG. The results indicate that the energy efficiency of ATEG-PCM has saturated at PCM height of 10 mm to 12 mm, while the exergy efficiency merely slightly increases. Especially, the PCM melting temperature merely affects the time at which PCM initiates to change from solid state to liquid state, without affecting the total energy efficiency of ATEG-PCM. Furthermore, the comparison analysis determines that ATEG-PCM deserves more attention, judging by thermal management and power generation. This work not only contributes to the understanding of the coupling mechanisms between PCM and ATEG but also provides a research direction for energy recovery in PCM based ATEG hybrid system.

Design and investigation of the solar-thermoelectric energy harvesting system at asphalt pavements road

Renewable energy is the generation of power from natural resources that plays an essential part in our society and economy as it helps reduce emissions for more sustainable future. Therefore, this project aims to analyse two energy harvesting technology, photovoltaic (PV) panels and thermoelectric generators (TEG), in terms of charging and voltage generated from waste heat in a road environment. H-shape heat sinks passive cooling element at subterranean level was implemented to achieve a maximum temperature difference of 15°C for TEG. The top plate, the hot side of TEG, can obtain a maximum of 53°C with a cold side of TEG only increased to 4°C from its initial temperature. Three TEGs connected in series able to charge 5F supercapacitors within 3.5 h, while 3V rated PV solar panel, acquired 15 min to charge the supercapacitor fully. Integrated PV and TEG were evaluated regarding the connection configuration of both energy harvesters into a single system. Series connection of the integrated system takes 29 min to fully charged the supercapacitor where all the results are saved into a microSD card and easily read in Excel. This project provides new insight into the charging performance of the two combinations of energy harvesting technology.

Comprehensive research on a simple and efficient radiative cooling driving thermoelectric generator system for nighttime passive power generation

Radiative cooling (RC) technology has broad application prospects because it does not require any energy input, which has drawn much attention from researchers. Thermoelectric generators (TEGs) can convert the temperature gradient directly into electrical energy without negatively affecting the environment. It is feasible and meaningful to combine RC device with TEGs to realize passive power generation. In the present study, we have developed a radiative cooling driving thermoelectric generator (RC-TE) system that is simple in structure and easy to manufacture. A continuous nighttime experiment was performed to evaluate the thermal and electrical performance of the RC-TE system by using a self-made device. Experimental results indicate that the temperature of the TEG cold side in contact with the radiative cooler can be at most 7.8 °C lower than the ambient temperature. The maximum temperature difference between the hot and cold sides of TEG can reach 2.7 °C, which corresponds to an open circuit voltage of 73 mV. Furthermore, an analytical all-parameter model considering the thermal resistance of all components has been established to investigate the effects of different parameters (wind velocity, ambient temperature, relative humidity, load resistance, area ratio, structure parameter of TEG leg, and number of TEG leg pairs) on system performance. This study has guiding significance for the improvement and optimization of experimental devices, and can provide a new thinking and some practical guidelines for the design and application of the RC-TE system.

Performance improvement of thermoelectric generator by drooping the cool side temperature with thermacool 0.3M coating

The hot side of Thermoelectric generator (TEG) receives heat from the heat source. Meanwhile, the output power and voltage depend on the temperature gradient between the hot and cold junction. Drooping the cold side temperature of TEG can increase the temperature gradient between its junction and subsequently the performance of the device. The conventional heatsinks used for heat dissipation and temperature drooping are at least twice as bulky as TEGs. Hence as an alternative, this work proposes coating of acrylic polyurethane-based heat reflective coating (Thermacool 0.3M) of 120 μm on cold side of TEG for drooping cold side temperature. To evaluate the performance of proposed system TEG (SP1848-27145) is tested in controlled temperature environment, Initially with heat sink model and later with thermacool 0.3M coating. A mathematical model has also derived for validation. The retardation in temperature of both model's cold side from 90 °C with respect to time are recorded. It is observed that after 4-minute of natural convection cooling the thermacool 0.3M coated model cool side temperature is 34 °C compared with 39 °C cool side heat sink attached model. There is a significant improvement in power, efficiency and figure of merit parameters of 0.18W, 3.8% and 0.04 respectively.

High-Efficiency Photo-Thermo-Electric System with Waste Heat Utilization and Energy Storage.

In a photo-thermo-electric system, solar energy is first converted into heat and then into electrical energy, which has attracted much attention. However, the heat of the cold side of a thermoelectric generator (TEG) is generally removed by an air-cooling or water-cooling technology without being fully utilized, resulting in a low solar energy utilization efficiency. Here, we designed an integrated system composed of a photo-thermo-electric conversion part and a waste energy collection part. In this system, one carbon foam (CF) doped with PPy and PEG is used as a layer for photothermal conversion and energy storage, and the other CF─where one side was hydrophobically modified─is used for the storage of cooling water and the recovery of waste heat. The two CF layers contact the hot and cold sides of TEG, respectively. With the system, solar energy can be converted into heat and then electricity for TEG. On the other hand, waste heat can be utilized for seawater desalination by the process of water evaporation. In addition, the integrated system can work sustainably under intermittent light conditions. With the recovery of waste heat, the solar energy utilization efficiency in this system is greatly increased to as much as 86%.

Theoretical analysis of liquefied natural gas cold energy recovery using thermoelectric generators

This paper presents a complex thermo-electric analysis of liquefied natural gas (LNG) cold energy recovery system using thermoelectric generators (TEG). The modeling uses the concept of effective thermal conductivity. In addition, it includes not only heat transfer and electric phenomena in TEG module but also all other secondary heat transfer processes: boiling of liquefied natural gas, conduction through walls, thermal contacts at both side of TEG and convection at the water side. Analysis is firstly made for commercial TEGs which are designed for operation at different temperatures. Next part of the analysis aims to optimize the geometry of TEG to temperature specific for liquefied natural gas. It is shown that the optimization of TEGs geometry for LNG conditions can lead to 50% increase of electric power generation. Moreover, for assumed filling factor of between 0.4 to 0.6, the length of TEG module should be between 0.4 mm to 0.7 mm. The conducted analysis provides important information on the possibility of recovering the cold energy of LNG using TEG modules.

Assessment of the integration of Three-Way Catalytic converter and Thermoelectric Generator

Thermoelectric Generator (TEG) in automobiles is a promising way to recover the exhaust heat, and can effectively increase energy utilization. The integration of a Three-Way Catalytic converter (TWC) and TEG can improve the performance by using the heat generated during catalytic operation but still has poor compatibility. Therefore, it is essential that how to improve the compatibility between TWC and TEG. This paper proposed a new method of the coupled carrier of the TWC to enhance the catalytic efficiency and increase the output of TEG. The new TEG was tested under steady and transient conditions. The results showed that the temperature uniformity of TEG is improved. The maximum output power of TEG is increased when TWC with the coupled carrier is working stably. The new TEG with coupled TWC carrier has the highest conversion efficiency for CO, NO, and H2 gases. Under the steady and transient conditions, reaction energy is transferred to the hot side of TEG and the performance of the one-sixth TEG output power can be increased to 306.2W by using the appropriate coupled carrier. Theoretically, this research provides the basis for further study.

Using high-frequency ultrasonic and thermoelectric generators to enhance the performance of a photovoltaic module

In this study, 1.7 MHz ultrasonic and thermoelectric generators (TEGs) are used to cool down a photovoltaic (PV) module and improve its performance. The PV module is placed on a rectangular enclosure equipped with five ultrasonic piezoelectrics, which produce cold vapor of water inside the enclosure. The hot side of TEGs is attached to the rear surface of the PV module and their left side is cooled using water cold steam generated by ultrasonic piezoelectrics. The outcomes revealed that when the cooling system is not used, Ts,ave increases to about 62.81 °C in the steady-state condition, while by using just the TEGs and just ultrasonic (H = 1.5 cm), the Ts,ave is reached 55.4 °C and 52.3 °C, respectively. The hybrid cooling system of TEGs and ultrasonic reduced the Ts,ave to 48.1 °C and increased its output power by 25.7%. By using the proposed cooling system, considering the impact of H on the temperature uniformity of the PV module represents that H = 0.75 cm is an efficient value to achieve high power output. In addition, the electrical efficiency of the PV module at the more efficient condition boosts from 8.61% to 12.46% compared to the non-cooling system.

Theoretical and Experimental Investigation about the Influence of Peltier Effect on the Temperature Loss and Performance Loss of Thermoelectric Generator

Thermoelectric generator (TEG) has great potential in low‐grade waste heat recovery and there is some research on the influence of the Peltier effect on it. However, most of them only consider the total performance changes, such as the variation of power and efficiency due to the Peltier effect, and ignore the impact of the Peltier effect on the temperature of TEGs, which is the core reason of performance changes. To investigate how the Peltier effect affects the temperature loss at the two sides of TEGs, respectively, an experimental setup is built and an analytical model is derived. The result shows that the temperature loss at the cold side is less than that of the hot side. The power loss has a linear relation with the product of the temperature difference and temperature loss. The maximum loss of power, energy efficiency, and exergy efficiency occurs at a particular load range. Within that range, power, energy efficiency, and exergy efficiency reach the maximum, respectively. According to the results, the suggestion of thermal resistance optimization for TEGs is provided.

Experimental study on the influence of Peltier effect and heat transfer boundary condition on the performance of thermoelectric generator

ABSTRACT Thermoelectric generator (TEG) has great potential in waste heat recovery which can convert heat into electricity based on the Seebeck effect, while the Peltier effect is negative and inevitable during the energy conversion process. The heat transfer boundary condition and Peltier effect influence the temperature difference which is the main factor determining the power generation performance of TEG. In this paper, to figure out how the heat transfer boundary condition and Peltier effect influenced the power generation performance of TEG, an experiment system was established. In the experiment, the initial hot side temperature of TEG was controlled by a heater, the cold side was cooled by water which belongs to the convective heat transfer boundary. The temperature variation of the hot and cold side of TEG caused by the Peltier effect under different initial hot side temperatures was analyzed firstly. Then, the temperature, internal heat flow, and power generation performance of TEG under different cooling conditions were investigated. The results showed that the Peltier effect reduced the actual temperature difference and resulted in the difference between the experimental and theoretical power generation performance. In addition, the enhancement of cold side heat transfer boundary conditions could raise the actual temperature difference and thus enhance TEG’s power generation performance. Besides, when the Peltier effect and heat transfer boundary conditions were both considered, the enhancement of the cold side heat transfer boundary condition can reduce temperature loss and thus the relative power generation performance loss caused by the Peltier effect. When the load resistance is 0.1 and the water flow rate increases from 0.1 to 7 , the relative power loss decreases from 29.01% to 20.20%, and the relative efficiency loss decreases from 20.49% to 13.60%. The findings of this work may provide a reference for the study of the heat transfer process of TEG.

Experimental investigation on combined thermal energy storage and thermoelectric system by using foam/PCM composite

This study reported an experimental investigation of thermal and thermoelectric performances of integrated energy storage/release/harvesting system that utilized PCM-based metal foam composite for enhanced latent-heat energy storage and employed thermoelectric generator (TEG) for energy harvest. The TEG was sandwiched between the foam/PCM hybrid material and a coolant tank, functioned as the hot and cold side of TEG. PCM was used to storage the latent heat, manipulate and stabilize TEG’s hot-side temperature and the metal foam was employed to enhance the thermal conductivity and accelerate the heat dissipation. Results showed that compared with pure PCM, that insertion of metal foam in PCM reduced the surface temperature of heat source, accelerated the process of melting/solidification of PCM, increased and unified the hot-side temperature of TEG, and therefore augmented thermoelectric energy. However, beneficial from the highest latent heat release, the case of pure PCM provided the most thermoelectric energy during solidification. Furthermore, the foam/PCM composite with lower porosity offered the best thermal control and highest thermoelectric energy harvest due to its highest thermal conductivity. The composite with lower melting point owned better thermal control for the heat source than that with higher melting point did, but at the expanse of less thermoelectric energy harvest.

Experimental investigation on the influence of phase change material on the output performance of thermoelectric generator

Thermoelectric generators (TEGs) can convert heat into electricity directly. However, the thermal boundary conditions are intermittent and high temperature in most TEG systems. Therefore, thermal management of TEG systems is of great significance. It is an efficient technology to use phase change material (PCM) for thermal management of the TEG systems. PCM is applied to hot side of TEG in this study, and the phase change material-thermoelectric generation (PCM-TEG) system is set up. For the purpose of exploring the effect of the PCM on the output performance of TEG, the common TEG system is established to compare with PCM-TEG system. Furthermore, the effect of the heat transfer characteristics of PCM on TEG output performance is investigated and discussed in detail under different pulse transient thermal boundary conditions. Experimental results show that PCM can reduce the temperature fluctuation to protect TEG and extend the temperature difference operation time. The PCM of solid state, solid-liquid coexistence state and liquid state have different effects on reducing the temperature fluctuation. Besides, the PCM-TEG system cannot provide the peak output power provided by the common TEG system, but it is still beneficial to provide a stable output power.

Waste heat recycling of high-power lighting through chips on thermoelectric generator

A waste heat is inevitably generated in high-power lighting due to the limited efficiency of light-emitting diode (LED) chips and the non-radiative transition of phosphors. In this work, we proposed an integrated module of LED chips on thermoelectric generator (TEG) for the waste heat recycling of high-power lighting. The multi-chips were directly bonded on the hot side of TEG for heat conduction. The chip powers and temperature distribution of chips-on-TEG were investigated under different chip currents, and their output voltage, current, and power were measured. When the chip current increases from 0.4 to 1.4 A, the heat power increases from 1.7 to 9.2 W, resulting in a high temperature gradient of 219 °C for the TE elements at the chip current of 1.4 A. This enough heat energy converts to an electric power with an output voltage of 1.23 V. In addition, a low-power indicating lamp was driven by the electricity from three chips-on-TEGs without additional power consumption. Our work opens a good idea to recover the normally wasted heat from high-power lighting, which could be extended for the heat energy harvesting in many power devices.

Comparison analysis of two different concentrated photovoltaic/thermal-TEG hybrid systems

To explore the novel structure and optimize the performance of the photovoltaic/thermal (PV/T) system, the linear Fresnel concentrating PV/T (LFPV/T) systems plus thermoelectric generator (TEG) with and without gravity-driven heat pipe (GHP) are investigated in this paper. GHP is an efficient heat transfer device, which could collect heat accumulated on PV to the hot side of TEG. TEG can convert heat into electrical energy with a temperature gradient. In this case, the GHP-LFPV/T-TEG system is proposed. However, the increased heat flux may rise the PV temperature and decrease the output of PV cells, so the water type LFPV/T-TEG system without GHP is introduced. This research focuses on the numerical study of the two systems and the comparative analysis of the performance is completed. The results show that the existence of GHP improved the thermal and comprehensive performance of the system and the output of TEG. After running for 7 h, the thermal efficiency and the comprehensive efficiency of the GHP-LFPV/T-TEG system were 10.23% and 2.55% respectively higher compared to those of the LFPV/T-TEG system, while the electrical efficiency and exergy efficiency were 2.91% and 1.56% lower under 800 W/m2 solar irradiation, 18 ℃ ambient temperature, and 15 ℃ initial water temperature. The TEG output of the GHP-LFPV/T-TEG system and the LFPV/T-TEG system was 13.64 kW and 6.41 kW respectively. Moreover, the influence of solar irradiation, concentration ratios, and TEG modules was also discussed.

Performance of Thermoelectric Power-Generation System for Sufficient Recovery and Reuse of Heat Accumulated at Cold Side of TEG with Water-Cooling Energy Exchange Circuit

Aiming to reduce thermal energy loss at the cold side of a thermoelectric generator (TEG) module during thermoelectric conversion, a thermoelectric energy conversion system for heat recovery with a water-cooling energy exchange circuit was devised. The water-cooling energy exchange circuit realized sufficient recovery and reuse of heat accumulated at the cold side of the TEG, reduced the danger of heat accumulation, improved the stability and output capacity of thermoelectric conversion, and provided a low-cost and high-yield energy conversion strategy in energy conversion and utilization. Through the control variable method to adjust the heat generation of the heat source in the thermoelectric conversion, critical parameters (e.g., inner resistance of the TEG, temperatures of thermoelectric modules, temperature differences, output current, voltage, power, and efficiency of thermoelectric conversion) were analyzed and discussed. After using the control variable method to change the ratio of load resistance and internal resistance, the impacts of the ratio of load resistance to inner resistance of the TEG on the entire energy conversion process were elaborated. The results showed that the maximum value of output reached 397.47 mV with a current of 105.56 mA, power of 41.96 mW, and energy conversion efficiency of 1.16%. The power density of the TEG module is 26.225 W/m2. The stability and practicality of the system with a water-cooling energy exchange circuit were demonstrated, providing an effective strategy for the recovery and utilization of heat energy loss in the thermoelectric conversion process.

Nanofibrous electrocatalyst including nanofibrous continuous network of graphitic nanofibers having embedded catalytically active metal moieties

Present study demonstrates a waste heat recovery from the proton exchange membrane fuel cell (PEMFC) using thermally coupled thermoelectric generator (TEG) and metal hydride (MH) cylinder. In TEG system, cooling of cold side is very crucial that significantly affects its power output. Therefore, a strategy is proposed in which PEMFC, TEG and MH are thermally coupled for efficient waste heat recovery from the PEMFC. A mathematical model is developed for the theoretical prediction of the dynamic performance of the proposed system. The proposed strategy is compared with different cases of cold side cooling of TEG such as: 1. natural cooling 2. fan cooling. An experimental study is performed with1 kW PEMFC and 5000 L MH cylinder. An air duct is designed to extract the heat loss from the PEMFC which is utilized at the hot side of TEG while cold side is mounted on MH cylinder. Results show that PEMFC heat loss increases with increase in the operationg load, therefore TEG power output also increases. Maximum temperature difference ≈3.2 °C is achieved between hot and cold sides of TEG. It is observed that TEG modules coupled with MH can be an efficient strategy for waste heat recovery from the PEMFC.