Thermoelectric Cells Research Articles

On the flow patterns and thermal behaviour of hybrid nanofluid flow inside a microchannel in presence of radiative solar energy

Solar radiative energy represents an important source of renewable energy. Of late, hybrid colloidal nanodispersion as an elevated heat transport agent acquires immense interest among researchers rather than unitary nanoliquids. The aim of this investigation was to quantify the flow patterns and heat transfer behaviour of hybrid nanoliquids in presence of nonlinear solar radiation for various solar thermal apparatus. Alumina–copper nanoingredients with water as host fluid are considered. The leading PDEs of our system are turned into ODEs by using prevalent similarity transformation. After that those ODEs have been solved by RK-4-based shooting method. Subsequently, the influences of relevant parameters on the heat transfer of fluid have been talked over on behalf of graphical and tabular approach. Extracted results are verified with experimental plus simulated data. Results communicate that solar radiation fosters heat transport in suction. Hybrid solution exhibits impressive increment in heat transport for suction. Though injection reduces the effect, the decay rate is slower for hybrid nanocomposite. Flipping nature of velocity is perceived for Reynolds number, rotational parameter, and nanoparticle concentration except the variations of suction/injection parameter. We believe that this comprehensive investigation will have potential applications in solar thermal power fabrication, solar ponds, solar thermo electric cells, etc.

Role of Heat Expansion with a Series of Ionic Liquids: The Case for Isochoric Thermoelectric Generators and Minimal Steric Repulsion

The role of convection in liquid thermoelectric cells may be difficult to predict because the inter- and intra-molecular interactions are not currently incorporated into thermodynamic models. Here, we study the thermoelectric response of a series of five anhydrous 1-methyl-3-alkylimidazolium halide ionic liquids with varied chain length and counterion in a high-aspect-ratio, horizontal-temperature-gradient geometry, where convection is minimal. While a canonical, constant-volume thermodynamic model indicates that greater disparity and longer aliphatic groups should exhibit larger Seebeck coefficients, we instead measure the opposite: Longer aliphatic chains correlate with lower densities and greater heat expansion, stronger intermolecular associations, stronger steric repulsion, and lower Seebeck coefficients. As evidence of the critical role of thermal expansion, we measure that the Seebeck effect is nonlinear: Values of −2.8 mV/K with a 10 K temperature difference and −1.8 mV/K with a 50 K difference are measured with ether ion. Our results indicate that steric repulsion and heat expansion are important considerations in ionic liquid design; with large temperature differences, the Seebeck coefficient correlates negatively with heat expansion. Our results suggest that Seebeck values may improve if thermal expansion and steric forces are limited in a pressurized, isochoric, convection-free design.

The waste heat recovery for power generation from automotive exhaust using thermoelectric cell (TEC)

The internal combustion process to move the vehicles had indirectly releasing waste heat into the environment which contributed to global warming. Thermal-electric Cell (TEC) is a device that able to convert thermal energy to electrical energy cleanly. The TECs system work when it is sandwiched between the hot and cold side. The objective of this study is to investigate the possibility of tapping a waste heat using thermoelectric cell (TEC) from car exhaust. The experiment had been carried out in stagnation condition in the laboratory using 1500 cc petrol engine DOHC (4G91). Four TECs (SP1848-27145) were connected in series on the top of exhaust muffler. The experiments were run in two type of cooling methods using air flow from standing fan and the flowing cold water. The maximum voltage of 2.42V was produced when temperature difference, DT reached 83°C. The LED bulbs were connected to TEC and light up when the voltage of 1.60V is obtained. The results have proved that the temperature difference between two sides is the dominant effect to determine the TEC performance. The generated power could be utilized to power an auxiliary application in the vehicle itself.

Innovative semitransparent photo-thermoelectric cells based on bismuth antimony telluride alloy

This research compromises of an innovative investigation based on semitransparent vertical cylinder-shaped thermoelectric cells (TEC’s). The temperature gradient was generated by light illumination. Cells with antimony doped bismuth telluride (Bi2Te3) were fabricated and its electric parameters were measured with different modifications to obtain the optimum design for maximum power efficiency. The thermoelectric material was filled in the semi-transparent plastic cylindrical tube with external and internal diameters and length of 6 mm, 5 mm and 20 mm. The open circuit voltage (VOC) and short circuit current (ISC) dependences with respect to averaged temperature and gradient of temperature were measured. These variations of temperature were controlled by varying the intensity of light. The fabricated semitransparent thermoelectric cells have 25% transparency. The investigation of thermoelectric properties of p-Bi2Te3 showed that increasing the average temperature from 34 to 60 °C, the increment in the current and voltage of the thermoelectric cells is 4.45 and 3.3 times. However, after modifications increased the current 10.1 and 8.9 times in case of water reservoir as a coolant, 16.5 and 14 times with large metallic top electrode, 19.3 and 19.5 times when all modifications added together, respectively. Overall optimum results were obtained with the least number of glasses, maximum load pressure, larger metallic electrode receiver, water reservoir as a coolant to get most temperature gradient. Potentially the semitransparent thermoelectric cells can be built and used to fabricate special windows which produce, electric power, allow to illuminate inside house directly by solar light without conversion to the energy and to heat water.

Detailed Model of a Thermoelectric Generator Performance

Abstract The paper deals with mathematical modeling of heat transfer phenomena occurring in a system containing thermoelectric elements. The main focus was on creating a useful computational tool for designing, validating, testing, controlling, and regulating the energy harvesting system with a thermoelectric cell. The model widely described in the literature, assuming a constant temperature level on both sides of the cell, has been modified to take into account the thermal resistance of heat exchangers that are inseparable parts of nearly every device of this kind. The results and conclusions from the solutions of equations forming a formalized record of the proposed method, the assumed approach to modeling, used physical phenomena and sensitivity analysis of the impact of the tested parameters on the system operation was presented. The calculations were made for the data of a selected thermoelectric generating cell available on the market.

The potential of thermoelectric energy harvesting in vehicles equipped with ICE

The paper deals with an issue of waste heat recovery in a selected configuration of an internal combustion engine. A possibility of using thermoelectric cells (currently available on the market) for production of electricity with heat extracted from the exhaust gas was considered. The calculations were made using specialized software. Features and design assumptions of the heat recovery system were presented and their influence on parameters of the entire system was investigated (efficiency of the internal combustion engine, power, etc.). An assessment of the applicability of the energy recovery system based on thermoelectric effects and characteristic of the proposed configuration was performed. Some issues that require further research have been highlighted.

SPICE Model Identification Technique of a Cheap Thermoelectric Cell Applied to DC/DC Design with MPPT Algorithm for Low-Cost, Low-Power Energy Harvesting

In this work, an identification technique of a simple, measurements-based SPICE (Simulation Program with Integrated Circuit Emphasis) model is presented for small low-cost Peltier cells used in thermoelectric generator (TEG) mode for low-temperature differences. The collection of electric energy from thermal sources is an alternative solution of great interests to the problem of energy supply for low-power portable devices. However, materials with thermoelectric characteristics specifically designed for this purpose are generally expensive and therefore often not usable for low cost and low power applications. For these reasons, in this paper, we studied the possibility of exploiting small Peltier cells in TEG mode and a method to maximize the efficiency of these objects in energy conversion and storage since they are economical, easy to use, and available with different characteristics on the market. The identification of an accurate model is a key aspect for the design of the DC/DC converter, in order to guarantee maximum efficiency. For this purpose, the SPICE model has been validated and used in a design example of a DC/DC converter with maximum power point tracking (MPPT) algorithm with fractional open-circuit voltage. The results showed that it is possible to obtain a maximum power of 309 µW with a Peltier cell 2 × 2 cm at a ΔT of 16 °C and the designed SPICE DC/DC converter performance proved the improvement and optimization value given by the TEG model identification.

Peltier Heats of LiFePO4 electrodes from a Thermoelectric Cell

Temperature is known to affect ageing and performance of lithium ion batteries [1]. We need to improve the understanding of the heat sources in the electrode compartments in order to accurately model internal temperature profiles. Reports of reversible heat effects local to electrode surfaces in lithium-ion batteries are therefore important, but are scarce in literature [2]. The reversible heat production at a battery electrode interface is investigated in this experimental work, measuring the Peltier heat of the electrode LiFePO4 electrode. The Peltier heat at an electrode can be found by measuring the change in electric potential across the cell with two identical electrodes when a temperature difference is applied [3]. We present the Seebeck coefficient and Peltier heat of a symmetric pouch cell consisting of two commercial LiFePO4 electrodes and a 1M LiPF6 and Ethylene Carbonate (EC) /Diethyl Carbonate (DEC) (50:50 w%) electrolyte-soaked separator. The electrodes have been thermostatted to the wanted temperatures T and T+ ΔT, respectively. Al (s,T) | LiFePO4 (s,T) | EC, DEC, LiPF6 | LiFePO4 (s,T + ΔT) | Al (s,T+ ΔT) We show that the thermoelectric effect is time-dependent due to a build up of concentration gradients within the cell, and the establishment of not only one, but two Soret equilibria. The initial Seebeck coefficient gives the Peltier heat of one electrode for a homogeneous electrolyte in a battery [4]. We derive equations that will describe the approach of the cell to steady state, and use this to estimate the initial value. The consequences of the Peltier heat of LiFePO4 for battery discharging and charging will be discussed. Acknowledgment The authors are grateful to the Research Council of Norway through its Centres of Excellence funding scheme, project number 262644, PoreLab. We acknowledge ENERSENSE for financial support. The group of authors also acknowledge the Research Council of Norway (RCN) project no. 228739, for funding through the project "Life and Safety for Li-ion batteries in Maritime conditions (SafeLiLife)".

Solar cell and thermoelectric hybrid generators

This research presents the study of the production of hybrid systems co-generating electricity of solar cells and thermoelectric heat loss from solar cells to thermoelectric. The system used in the experiment consists of a 10 watt solar panel, size 350 mm × 250 mm × 25 mm, supported by metal plates for heat and installed with a thermoelectric 10 thermoelectric solar cell module installed, will install the thermal side of the thermoelectric under the panel solar cell. The cold side is cooled by the heatsink. The built system will experiment in open space. Notify all day the heat that is lost under the solar cell and supported by metal plates is used to generate electricity with thermoelectric. Which can convert the heat energy into DC power according to the phenomena of according to the seebeck effect. From the results of the experiment, it was found that the average heating temperature was 59.42 degrees celcius. The average cold temperature is 37.37 degrees celcius at 12:30 PM. The maximum temperature difference is 24 degrees celcius. The voltage is 0.98 mV DC. The current is 224.65 mA. The average power output from the solar cell is 5.36 W and The average power output from thermoelectric is 220.16 mW.

Thermoelectric Intensifier of Heat Transfer between Two Moving Media with Different Temperatures

A patented thermoelectric intensifier of heat transfer between two moving media with different temperatures is investigated. Its design envisages the use of fan units in order to increase the heat-transfer intensity between media. A mathematical model of the device is developed based on solution of the heat balance equation for media flows in transport zones under conditions of forward flow. The calculated data are presented in the form of a dependence of the temperature change of moving media along the intensifier for different values of the heat-transfer coefficient between the thermoelectric cell junctions and the air medium in the device gap. It is established that, the larger the temperature difference between the inlet media, the sharper the dependence of the thermopile limit on the heat-transfer coefficient.

Flexible thermoelectric cells fabricated by rubbing-in technology with rubber-carbon nanotubes/graphene composites

In this research, CNT and graphene-rubber composites based thermoelectric cells were fabricated by using the rubbing-in technology. However, the comparative analysis of both elastic thermoelectric cells was also carried out. The carbon nanotubes and graphene composites with rubber were used as an active layer of thermoelectric cells. The films were deposited over rubber substrate (length 7 mm and width 5 mm) and pressure of (7–12) g/cm2. The electric dependence of the cells i.e., voltage (open-circuited), current (short-circuited), resistance and Seebeck coefficient with respect to averaged temperature (with gradient = 10 °C) was measured in the temperature interval of 30 °C–55 °C. The CNT/Graphene-rubber composite based active layer properties were investigated and results showed that with an increment in average temperature, there is an increase in current and voltage as well. In case of short circuit current, the increase in CNT-rubber and graphene-rubber composites was 1.82 and 4.5 times while an increase in open circuit voltage was 1.75 and 6.5 times, respectively. It was also found, that the graphene-rubber composites cells had a higher thermoelectric coefficient as compared to CNT-rubber thermoelectric cells. These cells can be potentially utilized as flexible and vibrations free thermoelectric sensors for measurement of the gradient of temperature and elastic thermoelectric modules for low power applications.

Solar Distillation Thermoelectric Power Generation

In this paper, a phase change material (PCM) heat storage and thermoelectric cells were integrated into a solar still. This project aim is to store the available solar heat using the PCM for generating power and increasing freshwater production. An experimental test rig of the solar still was designed, built and tested. The solar still consists of a single slope basin container with a PCM storage located at the bottom. The thermoelectric cells were installed beneath the PCM storage. The natural convection cooling method was used to cool the thermoelectric cells. The study showed that the solar still thermoelectric power generation (SSTEG) was able to produce 9.6 ml/m2 of fresh water and at the same time generated peak open circuit voltage of 44mV. The study is hopefully could provide a simple and cheap solar still system that can solve the water and electricity problem in rural areas.

Cryogenic Thermoelectric Cooler for Operating Temperatures below 90 K

The possibility of fabricating thermoelectric coolers for operating temperatures below 90 K is considered. It is impossible to use the standard thermoelectric-cell scheme consisting of two semiconductor legs of n-type and p-type conductivity connected into an in-series electrical circuit for these temperatures. There is only one effective n-type thermoelectric material based on Bi–Sb solid solutions for the region of cryogenic temperatures. For this case, thermoelectric cells with a thermoelectric n-type leg and passive leg based on a high-temperature superconductor (HTSC) are investigated. The design of a thermoelectric cooler (module) consisting of thermoelectric n-type legs (extruded Bi0.91Sb0.09 crystals) and passive HTSC-based legs (YBa2Cu3O7 –x) is proposed. A magnetic field is used to increase the thermoelectric figure of merit ZT of the module. The maximal temperature drop between the hot and cold sides ΔT > 13.5 K and maximal cooling capacity Qc > 0.36 W are attained for the cryogenic module at a hot side temperature of Th = 80 K, current consumption of I = 6.4 A, and voltage of U = 0.10 V.

Harvesting Low-Grade Heat via Thermal-Induced Electric Double Layer Redistribution of Nanoporous Graphene Films.

In this work, a closed thermoelectric cell based on a nanoporous graphene electrode is developed to convert low-grade thermal energy to electric energy. The thermoelectric cell consists of two nanoporous graphene electrodes in contact with the hot and cold ends, respectively, encapsulated in a KCl electrolyte, and the energy is harvested from the redistribution of the electric double layer (EDL) of the graphene electrodes under different temperatures. Because of the large specific surface and conductivity of nanoporous graphene electrodes, the electric voltage is 168.91 mV with the hot-end temperature of 61 °C and cold-end temperature of 26 °C, corresponding to the thermoelectric coefficient of 4.54 mV·°C-1, which is much larger than that of the conventional thermoelectric generator. The specific power output achieves 1.38 mW·g-1 and is also significantly larger than the previous EDL-based thermoelectric generator. System performance with the concentration of the KCl electrolyte is examined. The proposed thermoelectric cell can harvest low-grade waste heat from the ambient environment, which may have potential applications in energy supply, wireless powered devices, outdoor survival, and so forth.

Development of pressure-sensitive thermo-electric cell using graphene and n-Bi2Te3

This letter proposes an easy yet cost-effective process of a very sensitive thermo-electric pressure sensor based on Seebeck effect. For this purpose, two conductive substrates and pristine nanomaterial powder are used. This thermo-electric pressure sensor can be used for measurement of pressure in industry and medicine and in instrumentation as well. Materials that are used for the fabrication of the thermo-electric pressure sensors are economical and are easily available in the commercial market. The materials used are pristine nanopowder of n-type bismuth telluride (n-Bi2Te3), nanopowder of graphene, and flexible ITO substrates as conductive substrates.

Energy harvesting optimization for built-in power replacement of electronic multisensory architecture

In this work, we present a novel multisensory electronic architecture that can work with very low voltage requirements thus enabling power management directly from harvesting-based low-voltage sources. The harvesting system here proposed relays on thermoelectric generator cells useful for furnishing additional power to an electronic system made of a home-made sensory glove, an inertial measuring unit, and an electromyography device, aimed at providing full measures of the arm-hand dexterities. The thermoelectric generator cells are optimized to work as an array configuration up to 10 cells series-connected and the energy conversion is managed with a commercial DC/DC with MPPT algorithm.Experimental results demonstrate that the harvester can provide a maximum open-circuit voltage of 600 mV and a maximum power level of 9.9 mW for a standard human body temperature of 37 °C and a room temperature of 22 °C. Moreover, the system is able to fully charge an 800 mA/h, single-cell Li-Po battery within 35 h, showing a 30% efficiency loss. Since all the electronics in the multisensory architecture can run with voltages as low as the 3.7 V Li-Po battery, the harvesting system can be suitable to feed the device with an ad-hoc, high-efficiency boost conversion, thus replacing the USB-oriented built-in supply and recharge.

Effecting the thermoelectric properties of p-MnSi1.75 and n-Mg1.98Ag0.02Si module on power generation

Higher manganese silicide (p-MnSi1.75) and silver doped magnesium silicide (n-Mg1.98Ag0.02Si) were synthesized by hot press method in Ar atmosphere. Thermoelectric properties of p-MnSi1.75 and n-Mg1.98Ag0.02Si at temperature ranges of 300–473 K in air were measured. The thermoelectric elements size of 2 × 2 × 3 mm3 were compacted on top and bottom with Ag powder by hot press method to ensure a good connection with the electrode. Cu plate of 0.3 mm thick was used for electrode of the thermoelectric cell (1 pair) and module (30 pairs) because of its high conductivity. Alumina substrate size of 50 × 50 × 1 mm3 with good thermal conductivity was used. The dimensionless figure of merit (ZT) of MnSi1.75 and Mg1.98Ag0.02Si show a high value of 0.23 and 0.02 at 473 K, respectively. The highest power output of 1 pair and 30 pairs show a value of 19.71 μW and 4.69 mW at different temperature of 140 K.

Thermoelectric Power of Ion Exchange Membrane Cells Relevant to Reverse Electrodialysis Plants

A thermoelectric cell is designed and experiments are carried out in order to measure Seebeck coefficients of ion exchange membranes at different constant concentrations of NaCl in water. The purpose of the investigation is to explore how a temperature gradient may be applied to increase the efficiency of saline power plants, in particular, of the process of reverse electrodialysis (RED). To evaluate measurements and RED applications, we derive an expression for the thermoelectric potential for a cell with a single membrane and for a RED unit cell. The Seebeck coefficient is interpreted in terms of the Peltier heat of the cell, and further expressed in terms of transported entropies. We find the Seebeck coefficient of the cell, after correcting for temperature polarization, by gradually increasing the membrane thickness. The contribution to the Seebeck coefficient from the membrane varied between 1.41 and 0.98 mV/K in FUMASEP FKS-PET-75 cation exchange membranes, and between 0.56 and 0.48 mV/K in FUMASEP FAD-PET-75 anion exchange membranes. The precision in the results is 1%, for NaCl concentrations between 0.03 and 0.60 mol/kg. Measurements on the RED unit cell with water samples taken from realistic fresh- and salt-water sources confirmed that a temperature difference has a significant effect, increasing the emf by 1.3% per kelvin of temperature difference.

Thermoelectric Cell Produced from AA1100 Aluminium Alloy Coating on Metakaolin by Friction Surfacing Process

The objective of this article was to demonstrate the alternative method to produce the metal electrode on ceramic substrate. AA1100 aluminium alloy was thin-coated on alumina substrate by friction surfacing using a CNC milling machine. The properties of the coating layer were presented. After that, the coated ceramic substrate was connected to a thermoelectric material and used as thermoelectric electrode of the thermoelectric cell. Voltage, differential temperature and electrical current were measured. Power and efficiency of the thermoelectric cell were calculated. The maximum temperature at hot side of the thermoelectric cell was 171.48 °C. At this temperature, the voltage was 0.00027 mV and the power was 0.000655 W. Efficiency of the fabricated thermoelectric cell was 4.715 x 10-7.

Performance and economic limits of passively cooled hybrid thermoelectric generator-concentrator photovoltaic modules

Concentrator photovoltaic technology has doubled the efficiency of conventional non-concentrating photovoltaic systems. However, still ≈60% of the incident energy is dissipated as heat, and costs of concentrator photovoltaics need to be lowered for these systems to be competitive. One promising way for taking advantage of the heat generated in the solar cells is the hybridization with thermoelectric generators. The feasibility of hybrid concentrator photovoltaic-thermoelectric modules has been shown in recently published work for enhancing the efficiency and lowering the cost, with special emphasis on actively cooled designs. However, if feasible, the use of simple and reliable passive cooling would accelerate the development of new hybrid prototypes. The performance and cost reduction limits achievable with passively cooled designs have not yet been studied in detail. In this paper, an electric/thermal/economic model of concentrator photovoltaic-thermoelectric module is developed. As the main novelty, the model allows the thermoelectric generator area to be adjusted. Some optimisation problems are formulated and solved to evaluate the efficiency improvement and cost reduction of the hybrid system in comparison to a typical 800x light concentration factor and 36.4% efficiency concentrator photovoltaic-only module. The analysis showed that optimising the thermoelectric generator area is essential for the cell operating temperature limits not to be exceeded, and that conventional passive cooling is enough for achieving efficiency gains and cost reduction considering a state-of-the-art highly efficient 3 mm × 3 mm triple junction solar cell. With advanced thermoelectric materials and cell temperature of 100 °C, a maximum efficiency of 39.2% for the hybrid system can be achieved at 800x concentration factor by using low thermal resistance heat sinks, and a maximum cost reduction of 46.0% can be achieved at the maximum analysed concentration factor (1900x) by using moderate thermal resistance heat sinks. A trade-off between enhancing the efficiency and lowering the cost was observed. The sensitivity analysis on the thermoelectric parameters showed that parameters other than thermoelectric generator area and ZT figure-of-merit barely influence the results. The existing experimental concentrator photovoltaic-thermoelectric prototypes are far from the efficiency and cost benefits predicted in this paper. Thus, the study can help in the development of future prototypes.