Cold Side Of Thermoelectric Generator Research Articles

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.

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%.

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.

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.

Dynamic modeling and experimental analysis of waste heat recovery from the proton exchange membrane fuel cell using thermoelectric generator

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.

Model development and performance evaluation of thermoelectric generator with radiative cooling heat sink

Thermoelectric generator has been widely used to recover power from various heat sources. But limited attention has been paid to heat exchange from the cold side of thermoelectric generator. In this work, a novel thermoelectric generator with radiative cooling heat sink (TEG-RCHS) is developed to investigate the power generation performance with convective cooling and radiative cooling. The corresponding mathematical model is developed to investigate the impact factors on the performance of the TEG-RCHS module and the results indicate that wind speed and heater temperature have the positive impact, while atmospheric humidity and ambient temperature play the negative role on the power generation. Additionally, radiative cooler with spherical cap can help the TEG-RCHS module increase the heat exchange area, thus the module can achieve the higher power generation than the thermoelectric generator with aluminum heat sink (TEG-AHS) module and simultaneously have little impact on the actual application. During the operation modeling, the total power generation of the developed TEG-RCHS module is about 32% higher than that of the TEG-AHS module in arid Lanzhou, China. Additionally, convective cooling, ambient radiative cooling and sky radiative cooling account for the similar proportions, indicating thegreat importance of ambient radiative cooling and sky radiative cooling. Our developed TEG-RCHS module has great application potential, especially in electronic equipment, due to higher power generation performance and smaller footprint.

Enhanced thermal performance of a thermoelectric generator with phase change materials

Abstract In this article, a computational study of the thermal management of thermoelectric generator (TEG) with phase change materials (PCM) is made. The test model has been developed and studied using COMSOL Multiphysics. The thermal management of thermoelectric generator is studied using the heat sink encapsulating with the phase change materials through variations in the heat input and the quantity of PCM. The results showed the considerable reduction and constant maintenance with PCM for the cold side temperature of TEG. There was enhancement in output voltage due to an increase in the temperature difference between the hot and cold sides of TEG during the phase change period. The efficiency of TEG is enhanced due to improvement in voltage of TEG. The improvements in efficiency of TEG are found to be 36.7%, 33.8%, 30% for the heat inputs of 0.1 W, 0.15 W and 0.2 W respectively when the PCM height is 3 mm. From the computational results, it is confirmed that the PCM plays vital role for the enhancement in thermal performance of TEG.

Experimental Study of Thermoelectric Conversion Efficiency and Cold Side Thermal Management

Thermoelectric generator (TEG) while offering the advantage of operational reliability are constrained by limited efficiencies. This paper, which is from an undergraduate research project, focusses on the contribution of cold side thermal management of commercially available thermoelectric generators towards the thermal to electrical conversion efficiency for a range of hot side temperatures. Electric heating elements are used to vary the heat flux to the TEG while conventional active and passive methods employing air and water as a medium are used for dissipating heat from the cold side of TEGs. Both thermal and electrical performance parameters of the TEGs are recorded for various ambient conditions in an indoor facility corresponding to naturally occurring wind conditions. At the end, the utility and effectiveness of the cooling methods are quantified for the range of operating temperatures.

Energy management for thermoelectric generators based on maximum power point and load power tracking

Thermoelectric generators (TEGs) can be widely applied to directly convert thermal energy into electricity. Herein, we propose an energy management system for TEGs to achieve efficient energy storage and use. Specifically, we consider both the generally unstable power generation given the variable temperature difference between the hot and cold sides of TEGs and the variable load that requires the inclusion of a storage unit consisting of a battery and supercapacitor for improving the system performance. The supercapacitor mitigates energy fluctuations and reduces transients in the bus voltage, and the battery acts as a backup energy source, storing energy and delivering electricity when the load power demand is high. In addition, we propose a novel threshold control strategy based on the bus voltage intervals for the energy management system that incorporates maximum power point tracking (MPPT) and load power tracking (LPT) to maintain energy balance among the system units. MPPT aims to provide an efficient collection of thermal energy, and LPT based on fuzzy logic is used to maintain a stable bus voltage when the DC load power demand is low. The experimental results verify that the proposed LPT approach regulates the evaluated variations in DC load power with an average error of 3.5% and that the energy management properly operates under variable load power and battery state of charge.

Solar driven concentrated photovoltaic-thermoelectric hybrid system: Numerical analysis and optimization

In this study, a theoretical model of a concentrated photovoltaic-thermoelectric hybrid system has been developed based on first and second laws of thermodynamics and analysed in MATALB. A numerical method has been exploited to determine the temperatures of photovoltaic module (PV) and hot and cold side of thermoelectric generator (TEG) by iteratively solving the energy balance equations. The proposed study takes into account the effects of hot and cold side thermal resistances, thermoelectric properties, fill factor, geometry of thermoelectric module, load resistance and electrical current on the performance of the hybrid system. The results show that the optimum value of ratio of TEG load resistance to TEG internal resistance, m for maximum power output and efficiency of thermoelectric module is higher than unity. The concentration ratio should also be optimized to achieve maximum PV power output. For the fixed leg length of 5 mm and CG value of 1 kW/m2, the optimum m corresponding to maximum power output and maximum efficiency of the hybrid system is 0.5. The maximum power output and efficiency of the hybrid system increase by 5% as compared to the corresponding values of concentrated PV system. Moreover, at higher concentration ratios, the contribution of thermoelectric power to the power output of hybrid system is higher. Further, for other parameters fixed, the optimum value of CG for maximum power output of the hybrid system is 5.5 kW/m2 and it is 14% higher than the corresponding power output of CPV system alone. This improvement in the performance of hybrid system is added by the thermoelectric generator module. The results of this analysis incorporating the electrical and thermal contact resistances of thermoelectric device, may be helpful to envisage the design of a real photovoltaic-thermoelectric hybrid system.

Modeling and fabricating a prototype of a thermoelectric generator system of heat energy recovery from hot exhaust gases and evaluating the effects of important system parameters

The heat lost through smokestacks has an adequate energy recovery capacity. A new and effective method of recovering this energy is the use of thermoelectric generators, which directly convert thermal energy to electricity. Some of the advantages of thermoelectric generators include their environmental friendliness and also their lack of moving or rotating parts, which makes them operate without noise and extends their service life. This paper deals with the general modeling of a thermoelectric generator system, including the modeling of the cooling system for the cold side of thermoelectric generator, system of heat transfer from smokestack to the hot side of thermoelectric generator and also the modeling of the thermoelectric modules themselves. In continuation, for validating the obtained equations, an experimental prototype of this thermoelectric generator is fabricated and the empirical results including the nominal voltage, current and power of the manufactured system are compared with the theoretical results. This comparison shows the validity of the presented modeling and the good agreement between the theoretical and practical results, especially at low temperatures. Based on the calculations, the highest error was 4.6 percent for a temperature difference of lower than 100 °C. Additionally, for the same temperature difference, the highest theoretical and practical output powers for this module were 3.4 W and 2.8 W, respectively. Considering the matching of these results, the effects of some important parameters on the output power of the considered thermoelectric generator are also investigated, and the significant influence of the thermal conduction coefficient of thermoelectric modules is demonstrated.

Analysis of the use of thermoelectric generator and heat pipe for waste heat utilization

Waste heat recovery is one way to reduce the use of fossil fuels, one of them is by using thermoelectric generator to convert waste heat into Thermoelectric Generator (TEGs) is a module that can convert heat into electrical power directly, using Seebeck effect and Peltier effect as its working principle, so it can increase efficiency of energy consumption by utilizing waste heat from an instrument that generate waste heat. The focus of this research is to find the output voltage of TEG by utilizing the temperature difference on the cold side and the heat side of the TEGs. The heat side of the module will be given heat from the heater as a simulation of the heat from hot water, and on the cold side heat pipes will be used to remove the heat on the cold side of TEGs. The result, output voltage that generated by using 4 module TEGs that arranged to Thermal Series - Series Circuit and using 2 heat pipes is 2.1-volt, and then it is possible to use for phone charger.

Design and Fabrication of Wearable Thermoelectric Generator Device for Heat Harvesting

This letter presents a novel wearable thermoelectric generator (TEG) device for powering electronics by harvesting human body heat. The structural design of the TEG device consists of 12 thermoelectric modules, which are connected by copper strips electrically in series and thermally in parallel. A flexible printed circuit board with special hollows’ design is utilized as the bottom electrodes and substrate to enhance the flexibility of the device. The fabrication procedure to make this TEG device is then described. The hot- and cold-sides of TEG are soldered by a thin layer of Sn96.5Ag3Cu0.5 and Sn42Bi58, respectively. Therefore, the developed TEG device features both high flexibility and excellent performance for heat harvesting. Experimental characterization results demonstrated that the TEG device can achieve 23 μ W power and 4.75 μ W/cm2 power density at a temperature difference of 35 K. After wearing on human wrist, this TEG device can generate an open-circuit voltage of 10.5 mV, and the ability of using this TEG for powering a light emitting diode has been demonstrated. Results indicated that the developed wearable TEG device could be used for powering of wearable electronics and/or sensors.

Finite Element Analysis of Thermoelectric Generator with Aluminum Plate for Waste Heat Recovery Application

Thermoelectric generator (TEG) is the solid state device that converts the thermal gradient into electrical energy. TEG is widely used as the renewable energy source especially for the electronic equipment that operates with the small amount of electrical power. In the present analysis, the finite element analysis (FEA) using ANSYS is conducted on a model of the TEG attached with the aluminium, Al plate on the hot side of the TEG. This simple construction of TEG model was built in order to be used in the waste heat recovery application. It was shown that the changes of the width and thickness of the Al plate increased the temperature gradient between hot and cold sides of TEG. This directly increase the voltage produced by the TEG based on the Seeback effect. The increase of the thermal gradient due to the increment of thickness and width of Al plate might be because of the increase of thermal resistance of Al plate. Based on statistical analysis using full factorial of design of experiment, Al thickness play a major role in changing the performance of proposed TEG compared to that of Al width. This finding provides a valuable data in design process to build a good TEG attached with Al plate for the waste heat recovery application.

Co-generation of heat and power in a thermoelectric system equipped with Fresnel lens collectors using active and passive cooling techniques

A Fresnel lens collector was incorporated in a thermoelectric solar system for combined heat and power (CHP) generation. Two passive (heat pipe thermo-siphon) and active (pumped circulation) cooling systems were used for transferring heat from the cold side of thermoelectric generators to a thermal energy storage. Experimental results from the solar thermoelectric (STE) CHP system equipped with passive cooling showed that the maximum output power of the thermo-siphon from the thermoelectric generators (TEGs) was 70 W/m2. This system also generated 3.8 kW/m2 thermal power in a clear September day from 10:30 to 15:30. The thermal efficiency of the thermo-siphon configuration was 18.05% and its total efficiency (electrical and thermal efficiency) was 18.39%. Additionally, experimental results of the STE CHP system equipped with active cooling were indicative of 33.15% thermal efficiency and 33.88% total efficiency at a flow rate of 700 ml/min. The maximum generated power and stored thermal energy of the system were 143 W/m2 and 6.5 kW/m2, respectively.

Experimental and computational study on thermoelectric generators using thermosyphons with phase change as heat exchangers

An important issue in thermoelectric generators is the thermal design of the heat exchangers since it can improve their performance by increasing the heat absorbed or dissipated by the thermoelectric modules. Due to its several advantages, compared to conventional dissipation systems, a thermosyphon heat exchanger with phase change is proposed to be placed on the cold side of thermoelectric generators. Some of these advantages are: high heat-transfer rates; absence of moving parts and lack of auxiliary consumption (because fans or pumps are not required); and the fact that these systems are wickless. A computational model is developed to design and predict the behaviour of this heat exchangers. Furthermore, a prototype has been built and tested in order to demonstrate its performance and validate the computational model. The model predicts the thermal resistance of the heat exchanger with a relative error in the interval [−8.09;7.83] in the 95% of the cases. Finally, the use of thermosyphons with phase change in thermoelectric generators has been studied in a waste-heat recovery application, stating that including them on the cold side of the generators improves the net thermoelectric production by 36% compared to that obtained with finned dissipators under forced convection.