Thermoelectric Heat Research Articles

Performance of a BAPVT modules coupled TEHR unit fresh air system based on micro heat pipe array

Energy consumption for heating and cooling fresh air has become a major component of building energy consumption, and there is a growing focus on highly-efficient and energy-conserving fresh-air treatment technology. This paper presents a new fresh-air system based on a high-efficiency heat transfer element, the micro heat pipe array (MHPA). It consists of a novel air-cooled building attached to a photovoltaic/thermal module (MHPA-BAPVT) and a thermoelectric heat recovery unit (MHPA-TEHR). The system uses solar energy, photovoltaic power generation, and waste heat for fresh air preheating. A series of fresh-air systems were designed, constructed, tested, and analyzed. The results reveal that on sunny winter days, the temperature of fresh air flowing through MHPA-BAPVT modules can increase by 22.15 °C. The average thermal and electric efficiency of the MHPA-BAPVT modules was 12.16% and 7.10%, respectively, and MHPA-TEHR could exceed the upper limit of passive heat recovery technology, which could generate 1.25 kW of heat per 1 kW of input electric power. The maximum ratio of total heating power to the total power consumption of the fresh-air system reached 14.94. During a typical day in the winter season, solar preheating exceeded the fresh air heat requirement by 24.34%, and the excess heat provided 292.92 MJ for building heating demand. Comparing the electric heating fresh-air unit with conventional heat recovery, the former achieved nearly zero energy consumption during the winter season. During the transitional season, the system could provide 711.82 MJ of solar energy, which improved the indoor temperature. Finally, using the experimental data and meteorological parameters of Zibo, the annual heat and electricity benefits and reduced carbon dioxide emissions of the fresh-air system were calculated. The fresh-air system in this study can fully utilize solar energy for heat collection and power generation to reduce building energy consumption and can be applied widely.

Inverse current induced thermoelectric conversion in a parallel-coupled double quantum dot system

We investigate the thermoelectric transport and conversion of a parallel-coupled double quantum dot system, which consisting of two capacitively coupled quantum dots in the Coulomb-blockade regime. We found that the system exhibits an unconventional thermoelectric conversion process induced by the inverse current effect, which is attributed to the increased Coulombic interaction between quantum dots, resulting in strong asymmetry in the system. We study the transport properties of steady-state particle current and heat current, and analyze the influence of Coulomb interaction on the thermodynamic characteristics of unconventional thermoelectric heat engines and refrigerators.

Highly thermal conductive Boron Nitride/Polyrotaxane encapsulated PEG-based phase change materials

In this work, we tried to overcome the typical limitations of phase change materials (PCMs), namely, leakage and low thermal conductivity. To realize the leakage proof PCM, a polyrotaxane (PLR) was selected as a support material to encapsulate Polyethylene glycol (PEG) 1 k. Subsequently, different contents of Boron Nitride (BN) were blended to enhance the thermal conductivity of PLR/PEG matrix. The PCMs created in this work achieves a high thermal performance with enthalpy values (91.2–123.5 J/g) and high flexibility and shows a great shape stability and no leakage and shape change during its phase transition. Due to the action of BN as a multifunctional filler, the PCMs also experienced an increase of 186.7% to 806.7% in thermal conductivity values, and enhanced flame retardancy (with decrease of 16.6% for pHRR and 25.5% for THR). These improvements solve the main problems of organic PCMs thus making PLR-PEG-BN based materials a good candidate to be used as thermal energy storage material in industrial applications. For the exact application cases, it showed obvious Peak Shaving and Valley Filling for thermoelectric generator and heat regulation for the smart phone.

An analytical model for wearable thermoelectric generators harvesting body heat: An opportunistic approach

Wearable thermoelectric generators (WTEGs) have the potential to transform body heat into electrical energy, thereby establishing a sustainable power reservoir for wearable electronics and offering a promising alternative to traditional chemical batteries. This paper presents an opportunistic analytical model that investigates the energy conversion performance of a human skin-WTEG system. The model incorporates a one-dimensional bioheat transport equation to account for metabolic heat generation within skin tissue and heat exchange resulting from the blood perfusion, while a comprehensive three-dimensional analysis of the WTEG captures convective heat dissipation occurring between the WTEG and ambient surroundings. Analytical solutions for the temperature profile and power density of WTEGs are obtained, along with an approximate closed-form expression for the matched load resistance. The results demonstrate the significant impact of blood perfusion and convective heat dissipation on the WTEG performance. The optimal fill factor and height of thermoelectric couples for maximum power output are also determined. This model will assist in predicting and optimizing the performance of WTEG devices in practical applications.

Flexible Wet-Spun PEDOT:PSS Microfibers Integrating Thermal-Sensing and Joule Heating Functions for Smart Textiles.

Multifunctional fiber materials play a key role in the field of smart textiles. Temperature sensing and active thermal management are two important functions of smart fabrics, but few studies have combined both functions in a single fiber material. In this work, we demonstrate a temperature-sensing and in situ heating functionalized conductive polymer microfiber by exploiting its high electrical conductivity and thermoelectric properties. The conductive polymer microfibers were prepared by wet-spinning the PEDOT:PSS aqueous dispersion with ionic liquid additives, which was used to enhance the electrical and mechanical properties of the final microfibers. The thermoelectric properties of these microfibers were further studied. Due to their excellent flexibility and mechanical properties, these fibers can be easily integrated into commercial fabrics for the manufacture of smart textiles through knitting. We further demonstrated a smart glove with integrated temperature-sensing and in situ heating functions, and further explored thermoelectric fiber-based temperature-sensing array fabric. These works combine the thermoelectric properties and heating function of conductive polymer fibers, providing new insights that enable further development of high-performance, multifunctional wearable smart textiles.

Performance of a photovoltaic-thermoelectric generator panel in combination with various solar tracking systems

Photovoltaic cells have been widely used to harvest solar energy resources. However, their efficiency still needs to be improved as they are rarely designed to consider the sun's heat and movement. No literature has been reported on the performance of the combined photovoltaic and thermoelectric generators with different solar tracking systems. In this study, we investigated the performance of photovoltaic and combined photovoltaic-thermoelectric generator systems installed on three panels consisting of fixed, 1-axis, and 2-axis solar trackers. Light-dependent resistors were mounted on the panels to receive solar radiation. A microcontroller receives the signal and drives the motor on the vertical and horizontal axis to follow the sun's movement according to its azimuth and altitude angle. Thermocouples were used to record the temperature of the photovoltaic and thermoelectric generator surfaces. The experiment was conducted in Magetan City, East Java, Indonesia, from 05:00 to 18:00 Western Indonesia Time. The result shows that the solar tracker can drive the panel's axis to follow the sun's motion after receiving the resistance signal from the monitored azimuth and altitude angles. The observed solar radiation using the fixed, 1-axis, and 2-axis panels is 5.639, 6.858, and 7.523 kWh/m2/d, respectively. Installing the thermoelectric generator and heat sink reduces all panels' photovoltaic temperature by 3%. The maximum power of the photovoltaic-thermoelectric generator system on the fixed, 1-axis, and 2-axis panels increases by 0.77 W, 1.19 W, and 1.65 W, respectively, which comes from the photovoltaic power by 84% and the thermoelectric generator power by 16%. The maximum efficiency of the photovoltaic-thermoelectric generator system on the fixed, 1-axis, and 2-axis panels is 10.57%, 12.53%, and 13.99%, respectively, which increases at approximately 3% from the standalone photovoltaic efficiency. The present study's result improves the photovoltaic system's design by incorporating a thermal conversion and solar tracker.

Modeling and thermodynamic optimization of a solar-driven two-stage multi-element thermoelectric generator

In this article, a finite-time thermodynamic model of solar-driven two-stage multi-element thermoelectric generator is developed. Considering external heat transfers, radiation loss of collector, Joule heat and Fourier heat leakage, analytical formulas for heat balance equations, power and efficiency are derived. Working temperatures of thermoelectric device are obtained by solving four equations simultaneously, and basic performance of the system is explored. Performance optimization is executed by adjusting electrical current, thermoelectric element distribution and heat exchanger inventory distribution. The optimal allocations for different total thermoelectric element numbers are given by the enumeration method. Influences of various factors on maximal power and efficiency are analyzed, and the upper bounds of power and efficiency are given. Results show that an optimal collector temperature exists to achieve optimal performance for this solar power device. Power and efficiency show the same variation trend, and the efficiency is maximal when power reaches its maximum. The system performance is optimal when external heat transfers and inner structure parameters are optimal. At this time, the corresponding junction temperatures reach their optimal values, the total thermal conductance should be divided in a half to two heat exchangers, and the corresponding thermoelectric element is allocated nearly half to upper generator.

Dynamic behaviour of automobile thermoelectric waste heat recovery under different driving cycles

Different types of vehicles often run in different driving cycles, resulting in different dynamic behaviours of the automobile thermoelectric generator. The dynamic performance of a simplified automobile thermoelectric generator under different driving cycles, including HWFET, NEDC, WLTP, and CLTC, is evaluated to guide the application of automobile thermoelectric waste heat recovery by a hybrid transient CFD-TE model. The model is experimentally validated with an average output error of 10.92%, mainly caused by the instrument error. The findings indicate that the response of the dynamic output power of the automobile thermoelectric generator exhibits smoother fluctuations compared to the exhaust temperature, and also displays hysteresis in its response, while the dynamic conversion efficiency experiences sharp fluctuations. The behaviour of the automobile thermoelectric generator in dynamic situations is not entirely proportional to the vehicle speed but is instead dependent on changes in vehicle speed, more specifically, the change of exhaust heat. By comparing the steady and dynamic results, it is found that the steady-state model overestimates the output power but may underestimate the conversion efficiency. The automobile thermoelectric generator is more suitable for vehicles with frequent speed changes, such as passenger cars on urban and suburban roads, to enhance the dynamic output performance.

Optical mode localization sensing based on fiber-coupled ring resonators.

Mode localization is widely used in coupled micro-electro-mechanical system (MEMS) resonators for ultra-sensitive sensing. Here, for the first time to the best of our knowledge, we experimentally demonstrate the phenomenon of optical mode localization in fiber-coupled ring resonators. For an optical system, resonant mode splitting happens when multiple resonators are coupled. Localized external perturbation applied to the system will cause uneven energy distributions of the split modes to the coupled rings, this phenomenon is called the optical mode localization. In this paper, two fiber-ring resonators are coupled. The perturbation is generated by two thermoelectric heaters. We define the normalized amplitude difference between the two split modes as: (T M1-T M2)/T M1×100%. It is found that this value can be varied from 2.5% to 22.5% when the temperature are changed by the value from 0K to 8.5K. This brings a ∼ 2.4%/K variation rate, which is three orders of magnitude greater than the variation rate of the frequency over temperature changes of the resonator due to thermal perturbation. The measured data reach good agreement with theoretical results, which demonstrates the feasibility of optical mode localization as a new sensing mechanism for ultra-sensitive fiber temperature sensing.

Economic and thermal analysis of a tubular thermoelectric power generator equipped with a novel fin-pin-porous based heat exchanger; comparative case study with conventional smooth channel

Wasted hot exhaust gas in thermodynamic engineering systems is always a potential source of power generation via different techniques. Passing the hot gas through the inner area of a tubular thermoelectric module can directly convert the hot gas into electricity. In this research, it is shown how the performance of tubular thermoelectric heat recovery is significantly boosted using a novel fin-pin-porous based heat exchanger. Generally, the results show that the proposed integrated structure can enhance the output power of the recovery system up to 45%–110% compared to the conventional smooth channel-based tubular thermoelectric generator. A comparative case study is carried out between the new proposed system and conventional smooth structure from different viewpoints including power generation, conversion efficiency, pumping power and economic cost.

Evaluation of the energy efficiency of an active thermoelectric façade

Innovative sustainable and decentralised energy systems have the potential to contribute significantly to energy saving and carbon emission reduction in the building sector. This article discusses the evaluation of such a novel decentralised heating and cooling system based on small thermoelectric heat pumps called Peltier elements, focusing on its energy efficiency. Experimental studies on the performance of a prototype façade system in outdoor conditions were performed. Based on the results of these experimental studies, thermal simulations were performed using the thermal building simulation program TRNSYS. Combining the results of the outdoor evaluations with those of the building simulations, the energy performance of the developed façade system could be evaluated. It was found that the demand for electrical energy was about 10% higher than that for heating energy, showing that the designed façade system cannot be operated with sufficient efficiency and therefore is not a sustainable alternative to commercially available systems at the current state of the art.

Utilization of Heat from Geothermal Well Pipes as Electricity for Road Lighting Based on The Internet of Things

PT. Pertamina Geothermal Energy Area Lumut Balai has a very extreme work location with various contours, safety factors and lack of access to electricity for street lighting are things that need attention given the importance of street lighting in the company's operations. Street lighting is an important element that supports the comfort and safety of road users in their activities at night. The research objective is to design an IoT (Internet Of Things) system that can monitor the utilization of pipe heat into electrical energy for street lighting and provide street lighting needs around geothermal well pipes. In this study used thermoelectric as a tool to generate electrical energy from available heat. The IoT system is used to read data parameters as a tool to display temperature, voltage and current values on the LCD (Liquid Crystal Display) and the Thingspeak website. The temperature value is read by the MAX6675 thermocouple sensor while the INA219 sensor is used to read the voltage and current values. The focus of this research is to heat the thermoelectric so that it can produce electrical energy to turn on the lights as lighting and can monitor parameter data directly. The highest thermoelectric electrical energy output is at a temperature of 75.1˚C. Where at this temperature a voltage of 2.32 V is generated and a current of 0.03 A. The lamp will turn on if the thermoelectric heat is fulfilled. The light turns on when the environment is dark and the light turns off when the environment is bright

Thermoelectric Joule heating in crack problems in nano-sized structures

Crack problems in nano-sized elastic structures under the Joule heating are analyzed by the finite element method (FEM). The variational principle is applied for derivation of coupled electrothermomechanical governing equations. The temperature field is described by classical Fourier′s law and it is not influenced by mechanical field. Transient heat conduction is considered since it is the slowest process among all other coupled fields here. Quasi-static conditions are considered for mechanical and electrical fields. Due to higher derivatives in governing equations the conventional FEM cannot be applied. Therefore, the mixed FEM with the C0 continuous interpolation for displacements and strains is developed. The influence of the material characteristic length on variation of crack opening displacements in finite nano-sized structures under an electric current load is investigated.

Local Heating through the Application of a Thermoelectric Heat Pump for Prenursery Pigs

Mathematical formulation of the animal thermal status has been developed, with the account of two convenience conditions and heat balance, for the floor-mounted heating panel for prenursery pigs. The borders of the heat flux variation range for the floor-mounted heating panel have been determined corresponding to the animal-friendly conditions for prenursery pigs of various age groups. The block diagram of the energy-saving floor-mounted heating panel, comprising the thermoelectric assembly operating in the heat pump mode, has been designed. The method has been described and the corresponding calculations have been made for the basic thermal parameters of the floor-mounted local heating installation, for prenursery pigs, with the application of a thermoelectric heat pump. The experimental installation sample of 116 W thermal capacity (for the heat transfer coefficient from 0.9 W·m−2·K−1 to 1.0 W·m−2·K−1 and floor temperature in the range of 5 °C to 6 °C) has been developed and manufactured for local heating for prenursery pigs managed in gestation crates. Laboratory tests of the experimental sample of the floor-mounted heating panel have demonstrated high energy efficiency of the heating installation under development. The energy-saving effect (approx. 15% compared to the series-produced equipment designed for local heating of young stock) of the developed installation was achieved owing to the partial heat recuperation of the exhaust ventilating air.

Modelling and Simulation Study of a Segmented Converging Thermoelectric Heat Exchanger for Power Generation Efficiency Improvement

Modelling and Simulation Study of a Segmented Converging Thermoelectric Heat Exchanger for Power Generation Efficiency Improvement

Investigations on thermoelectric characteristic of heat pipe thermoelectric generator waste heat utilization device in nuclear power system

This paper proposes a waste heat utilization method for new type reactor by Heat Pipe - Thermoelectric Generator (HP-TEG) to utilize the waste heat of lower divertor in fusion device and stirling generator in heat pipe space reactor. The feasibility of the HPTEG waste heat utilization device is verified by its principle prototype. Firstly, the numerical simulations of the single heat pipe and principle prototype were carried out to provide a numerical optimization scheme for the design of the principle prototype. The simulation results show that the heat transfer efficiency of the copper–water heat pipe is about 93%, while the overall heat transfer efficiency of the principle prototype is about 85%. Based on the simulation results, the thermal stress concentration areas were found, mainly concentrated in the thermal insulation short of the heat pipe. During the construction of the principle prototype, stainless steel sleeves were installed outside the insulation section of the heat pipe to limit the thermal expansion caused by the thermal stress concentration. Besides the principle prototype of HPTEG assembled in new type reactor was built, and its thermoelectric characteristics were studied, the results verified the feasibility of using waste heat. The test results show that the principle prototype starts smoothly, and the heat pipe has suitable isothermal properties (△T < 15 ℃). Due to the heat pipe's high heat transfer efficiency, the heat pipe obtained from the experiment is 91%–96%. The principle prototype has good heat transfer efficiency, which is 81.94%–93.25%. The maximum total electric power output of TEG is 16.37 W, in which the corresponding current is 0.52A, and the power generation efficiency is up to 1.49%. This paper verifies the feasibility of HPTEG to utilize the waste heat of lower divertor in fusion device and stirling generator in heat pipe space reactor, which provides a reference for the utilization of reactor residual heat.

Enhanced Performance of Combined Photovoltaic–Thermoelectric Generator and Heat Sink Panels with a Dual-Axis Tracking System

The photovoltaic panel has become the most promising alternative technology for energy demand. Solar trackers have been used to improve the efficiency of a photovoltaic panel to maximize the sun’s exposure. In high temperatures, however, the photovoltaic efficiency is significantly reduced. This study observes photovoltaic/thermoelectric generator performance driven by a dual-axis solar tracking system. A photovoltaic/thermoelectric generator panel was built and equipped with angle and radiation sensors. A microcontroller processes the sensor signal and drives the motor to follow the sun’s movement in two-axis directions. Thermocouples are mounted on the photovoltaic and thermoelectric generator surfaces to monitor the temperature. The result shows that the temperature of the photovoltaic/thermoelectric generator is lower than that of the photovoltaic one. However, a contradiction occurred in the output power. The efficiency of the combined photovoltaic/thermoelectric generator was 13.99%, which is higher than the photovoltaic panel at 10.64% and the thermoelectric generator at 0.2%. The lower temperature in the photovoltaic/thermoelectric generator is responsible for increasing its performance. Although the thermoelectric generator contributes modest efficiency, its role in reducing the temperature is essential. Analyses of some cooling techniques for photovoltaic panels prove that the combined thermoelectric generator and heat sink improves photovoltaic performance with simplified technology.

Infrared Image Pre-Processing and IR/RGB Registration with FPGA Implementation

Infrared imaging sensors are frequently used in thermal signature detection applications in industrial, automotive, military and many other areas. However, advanced infrared detectors are generally associated with high costs and complexity. Infrared detectors usually necessitate a thermoelectric heater–cooler for temperature stabilization and various computationally complex preprocessing algorithms for fixed pattern noise (FPN) correction. In this paper, we leverage the benefits of uncooled focal plane arrays and describe a complete digital circuit design for Field Programmable Gate Array (FPGA)-based infrared image acquisition and pre-processing. The proposed design comprises temperature compensation, non-uniformity correction, defective pixel correction cores, spatial image transformation and registration with RGB images. When implemented on Xilinx Ultrascale+ FPGA, the system achieves a throughput of 30 frames per second using the Fraunhofer IMS Digital 17 μm QVGA-IRFPA with a microbolometer array size of 320 × 240 pixels and an RGB camera with a 1024 × 720 resolution. The maximum ratio of the standard deviation to the mean of 0.35% was achieved after FPN correction.

A thermodynamic model of integrated liquid-to-liquid thermoelectric heat pump systems

Thermoelectric (TE) heat pumps (TEHPs) are advantageous for heating and cooling in various applications because of their modularity and simple design. A TEHP system includes the TE modules with p- and n-type materials bonded to substrates, plus heat exchangers, thermal interfaces to the heat exchangers, and heat transfer fluids. Although modeling an individual TE module has been extensively studied, limited studies have reported performance at the larger system-level. Furthermore, no prior study has addressed the impact of temperature-dependent TE material properties (e.g., electric resistivity, thermal conductivity, and Seebeck coefficient) on overall heat-pump-system-level performance. This work presents a mathematical model for TEHP system performance based on Goldsmid's approach for TE material performance, “effective” TE material properties, Gnielinski's correlation for convective heat transfer, and thermal balance theory for a heat exchange network. This combined approach provides an accurate model of the liquid-to-liquid TEHP system. Three different approaches—one empirical, one based on the manufacturer's specifications, and one drawn from the literature—were then used to determine values for TE material properties. The first two methods treated properties as constants, while the last approach treated properties as surface-temperature-based functions. Finally, experimental TEHP data was used to validate the models, all with relative absolute deviations of approximately 10% when predicting heating capacity and 10%–25% when forecasting cooling capacity up to a 30 K surface temperature lift. The results demonstrated that, at the TEHP system level, the TE material properties could be treated as constants, avoiding solver iterations and reducing the performance uncertainty by up to 95%.

Performance of a thermoelectric heat pump with recirculation and regenerative heat recovery

In this paper, the thermoelectric heat pump performance is enhanced by air recirculation and regenerative energy recovery. Compared to conventional vapor-compressed heat pumps, TEHP is more stable, safer, and flexible in arrangement, but is relatively less efficient. Therefore, the use of air recirculation combined with regenerative heat recovery is dedicated to increasing the efficiency of the heat pump and recovering some of the energy, thus reducing energy consumption. Experimental results show that the COP of the air recirculation TEHP is as high as about 3.7. At 1 m/s air velocity, the COP with recirculation is 51–73% higher than without recirculation. In the system experiments for heat exchanger test applications, the percentage of regenerative heat recovery was up to 12%. The combination of regenerative heat recovery and air recirculation further improved the energy efficiency of the heat exchanger test system to a maximum energy efficiency ratio of 2.85. The energy-saving measures of TEHP with recirculation and regenerative heat recovery resulted in better energy savings than the conventional heat exchanger test device with resistance heating. It is of great reference significance in fields of thermoelectric technology applications.