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Electrical characterisation (V-I and P-I curves) of the thermoelectric device GM250-449-10-12 by European Thermodynamics Ltd.
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It is well known that for a thermoelectric generator (TEG) in thermal steady-state with constant temperature difference across it the maximum power point is found at half of the open-circuit voltage (or half of the short-circuit current). However, the effective thermal resistance of the TEG changes depending on the current drawn by the load in acco...
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... and subtle device response to vari- able load current. The internal resistance (R int ) is the inverse slope of the V-I line obtained from this electrical characterisation, and its absolute value is dependent on the average temperature at which the TEG is operating. When the TEG is operated to the left of the maximum power point as shown in Fig. 1, reduced current flows through the TEG and the effective thermal conductivity of the TEG (which depends also on the current flow, due to the parasitic Peltier effect) decreases. Under this condition the thermal energy conducted via the TEG is less than that at the maximum power point and hence a lower thermal load is imposed on the ...
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... is advantageous in most circumstances since it leads to increased thermal efficiency of the system. When the TEG is operated to the right of the maximum power point the thermal conductivity increases and the thermal energy conducted via the TEG is greater than that which flows at the maximum power point. Operation in the region to the right on Fig. 1 leads to a reduced thermal efficiency of the system. For the module data (product code: GM250-449-10-12 by European Thermodynamics Ltd.) shown in Fig. 1, the maximum power is approximately 13.2 W with a corresponding output voltage of 16.5 V (being half of the open-cir- cuit voltage of 33 ...
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... power point the thermal conductivity increases and the thermal energy conducted via the TEG is greater than that which flows at the maximum power point. Operation in the region to the right on Fig. 1 leads to a reduced thermal efficiency of the system. For the module data (product code: GM250-449-10-12 by European Thermodynamics Ltd.) shown in Fig. 1, the maximum power is approximately 13.2 W with a corresponding output voltage of 16.5 V (being half of the open-cir- cuit voltage of 33 ...
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... a new voltage is applied the current changes accordingly and so does the temperature difference. A new V OC is established and V load must be updated again. The pro- gram is considered to have achieved convergence when the differ- ence between V load and V OC =2 is less than 1 mV. This V OC is marked by a magenta circle on the primary y-axis of Fig. 2 (7.14 V), while the open-circuit voltage related to the maximum power point is marked by a black circle (7.39 V). As a result of this analysis the load chosen (I HV ¼ 1:86 A) is greater than I MP ¼ 1:58 A, leading to a smaller DT ¼ 149:6 C and a power produced of 6.62 W, which is 2.9% smaller than P MP ¼ 6:82 ...
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Thermoelectric Generators (TEGs) are devices for direct conversion of heat into electrical power and bear a great potential for applications in energy scavenging and green energy harvesting. Given a heat source, the conversion efficiency depends on the available temperature difference, and must be maximized for optimal operation of the TEG. In this...
Citations
... Considering the temperature-dependent thermoelectric properties, the scholars found that the maximum power generation occurs when the area of the n-pellet is smaller than that of the p-pellet. Montecucco et al [8] analysed how the number, size, and clearance space of pellets influence the output power of a TEG module under constant heat flux conditions. They calculated the optimum pellet packing factor and length values under different thermal input powers. ...
... As the temperature of heat source T 1 increased from 330 K to 350 K and to 370 K, V oc increased from 0.97 V to 1.59 V and to 2.27 V, and P max increased from 0.16 W to 0.41 W and to 0.80 W. Due to the temperature dependence of the electrical resistivity, as the average temperature of the TEG module increased with T 1 , R in increased from 1.48 Ω to 1.55 Ω and to 1.62 Ω. A previous study by A Montecucco et al [8] indicated that when there are no changes in temperature difference due to the Peltier effect and Joule heating, the maximum power point can be located at half the value of the short-circuit current. In our measurement results, P max indeed occurred at approximately the half value of the short-circuit current, thus confirming that the thermal drift caused by the Peltier effect was negligible. ...
Reducing surface roughness and using thermal interface materials (TIMs) at the interfaces between a thermoelectric generator (TEG), heat source, and heat sink are effective strategies for decreasing the thermal contact resistance (TCR) and enhancing the TEG performance. To evaluate the influences of parameters such as the surface roughness, the thermal conductivity of TIM and loading pressure, we conducted experiments to measure the open-circuit voltage and output power of the TEG under various installation conditions. We also analysed the changes in TCR and temperature difference across the TEG module. The experimental findings were validated with numerical simulations using COMSOL Multiphysics under specific conditions. Our results revealed that reducing surface roughness and using TIM could substantially reduce the TCR, increase the temperature difference across the TEG, and increase the output power from the TEG. In our experiments, we used a temperature controller, cartridge heaters and thermocouples to regulate and record the temperatures of the heat source and heat sink. When maintaining a temperature difference of 53 K between the heat source and heat sink, and loading pressure set at 0.2 MPa, without using TIM, as the surface roughness decreased from 2.2 μm to 0.37 μm and to 0.03 μm, leading to a reduction in the TCR from 0.22 K/W to 0.17 K/W and to 0.13 K/W. Simultaneously, the open-circuit voltage increased from 1.32 V to 1.65 V and to 1.86 V, and the maximum output power increased from 0.26 W to 0.44 W and to 0.58 W. Additionally, when the surface roughness was 0.37 μm, after using TIM with thermal conductivity of 1 W/m-K, 2 W/m-K, and 5 W/m-K, the open-circuit voltage reached 1.44 V, 1.74 V and 1.94 V, respectively, and the maximum power reached 0.31 W, 0.51W and 0.65 W, respectively.
... Thermoelectric generators (TEG) can collect heat energy from the environment, so that the energy acquisition is no longer limited to the movement of the human body. The performance of flexible thermoelectric generator (f-TEG) largely depends on the density and geometric dimensions of the thermoelectric legs, structural design, and heat sink [7][8][9]. ...
Electronic skin has received widespread attention in the industry due to its conformal contact with human tissues and organs, improving interaction capabilities, and obtaining physical and chemical signals in the environment and human body. Electronic skin includes many sensors and electronic devices, which is difficult to produce and store energy by itself, and the use of external energy supply is cumbersome and unstable. Therefore, it is challenging to meet the energy needs of the electronic skin. Consequently, energy harvesting methods and the latest developments for electronic skin are reviewed. First, the performance and development trends of triboelectric nanogenerators, which generate electricity through mechanical energy and can be used as a self-driving sensor to electrical skin, are discussed. Then, the thermoelectric performance and future development of thermoelectric generators (TEGs), which use flexible thermoelectric materials and tiny temperature differences to generate electricity, are summarized. In addition, the basic challenges and latest efforts of flexible perovskite cell (F-PSC) made of perovskite materials with easy preparation, modification, and high efficiency are studied. This review provides an overview of the energy supply of electronic skin and its performance improvement and structural exploration.
... The energy is sufficient to power a vast range of intelligent wearable electronics if the 1% dissipated heat from human body can be harvested by using WTEGs. The energy conversion performance of WTEGs is not only depended on the figure of merit of thermoelectric materials [9,10], but also on their structural parameters including geometrical configuration of thermoelectric legs [11][12][13][14], percentage of filler material [15,16], imposed electric resistance [17][18][19], structure of heat sink [20][21][22], mounting position (e.g. arm, wrist, chest or forehead) [23][24][25], contact thermal resistance between skin and WTEG [14,15,26] and physiological characters of human skin (e.g. ...
... Now, the temperature fields inside the skin and WTEG are completely carried out by Eqs. (11) and (23), then the current can be calculated by Eq. (7) based on the iterative approach. The iteration will be terminated when the error value of current between two successive iterations is less than 0.1%, that is |1 − I(i − 1) /I(i)| < 0.1% (where i is the iterations). ...
A thermodynamic model for skin and wearable thermoelectric generators (WTEGs) system is developed based on dual-phase-lag (DPL) bioheat transfer. Human skin is regarded as a multi-layer structure consisted of subcutis, dermis and epidermis. Analytical solutions for temperature profile inside skin-WTEG system and energy conversion performance of WTEGs are obtained. Numerical results show that very small deviations for power output of WTEGs are caused by using the room-temperature physical properties of Bi2Te3-based thermoelectric semiconductors. However, the effect of heat convection by blood perfusion inside skin tissue should be considered to estimate energy conversion performance of WTEGs accurately. The influence of the contact thermal resistance between the skin and WTEG can be neglected when the thermal conductance ratio of the skin-WTEG interface to the flexible substrate is larger than 0.1. It takes more than 10 min to attain the steady-state again when a thermal perturbation is applied to the skin-WTEG system. The classic Fourier bioheat transfer model may also provide acceptable accuracy for the energy conversion analysis of WTEG compared with the non-Fourier bioheat transfer model if the response time exceeds 1 min. This paper provides a useful theoretical model for designing WTEG devices.
... The maximum power output (P max ) is generated when the external load resistance is equal to the TEG internal resistance. Therefore, the maximum power point of the TEG under a steady temperature difference occurs at half of the open-circuit voltage [33], and can be calculated using ...
In this study, a fluid–thermal–electrical multiphysics numerical model was developed for the thermal and electrical analyses of a heat sink-based thermoelectric generator (TEG) in a waste heat recovery system used for casting a bronze ingot mold. Moreover, the model was validated based on experimental data. Heat sinks were installed on the hot side of the TEG module to recover the waste heat from the flue gas generated in the casting process. The numerical results of the thermal and electrical characteristics of a plate fin (PF)-based TEG showed good agreement with the experimental findings. Numerical simulations of heat sinks with three different fin structures—PF, cylinder pin fin (CPF), and rectangular pin fin (RPF)—were conducted. The simulated system pressure drop, hot- and cold-side temperature difference in the TEG module, TEG power output, and TEG efficiency were compared for the differently designed fin structures. The results showed that for the same fin area, the CPF heat sink-based TEG system achieved a lower pressure drop, higher power output, and higher efficiency than the other two designs. This was particularly true when the velocity of the flue gas and the fin height exceed 5 m/s and 28.6 mm, respectively. Therefore, for low and high flue gas velocities, PF and CPF heat sinks are recommended as the best choices, respectively.
... This is to be noticed that maximum power output (P max ) is generated when the external load resistance is equal to the TEG internal resistance, therefore the maximum power point of a TEG under the steady temperature difference lies at half of the open-circuit voltage [26], and can be calculated using Eq. (15). ...
This study presents a numerical investigation of the performance evaluation of a waste heat recovery (WHR) system from a bronze ingot casting mold via a thermoelectric generator (TEG). A rectangular plate fin heat sink is installed at the hot side of the TEG to recover the waste heat from the casting mold while the flow direction of the flue gas is found to be normal to the fin base. A multi-physics numerical model, which couples the governing equations of fluid, thermal and electrical models are presented and solved by using ANSYS 19.2 software. The numerical results for the thermal characteristics of TEG and its power output show good agreement with the experimental results. The study has been performed to analyze the effect of different fin parameters such as fin height (Hf = 12.6–52.6 mm) and fin number (Nf = 15 to 21), and flue gas parameters such as inlet velocity (Vin = 0.5–7 m/s) and inlet temperature (Tin = 550–650 °C) on the performance of the TEG system during WHR. Results indicate that TEG module power increases with the increase in fin height, fin number, inlet flue gas velocity, and temperature. The maximum net power output and maximum net efficiency are found to be 18.83W and 2.33% at inlet flow velocities of 5 m/s and 3 m/s, respectively. In addition, significant radiation has been observed through the numerical investigation. The fraction of radiation effect ranged from 5.01% to 24.15% in the test conditions.
... In fact, after the current is drawn from the TEG, the temperature difference decreases exponentially to the steady-state value. Because the thermal time constant of a typical TEG system is long, this thermal transition may take several seconds to complete at least 90% [99]. Considering this situation, an algorithm is proposed that searches for MPP between 50% and 60% of the instantaneous open circuit voltage [100]. ...
One of the green technologies that can be used to increase energy efficiency by recovering a part of waste heat as electrical energy is thermoelectric generators (TEG) by using the Seebeck phenomenon. Conventional and modern maximum power point tracking (MPPT) methods used to deliver maximum power from energy sources. Conventional MPPT algorithms have disabilities such as a delay in reaching the maximum power point (MPP), certain oscillations around the MPP, being stuck at local MPP (LMPP), and not being able to find global MPP (GMPP). In order to overcome the drawbacks of conventional MPPT methods, methods using metaheuristic MPPT algorithms have come to the fore in recent years. However, the issue of determining the appropriate method among the increasing number and complexity of MPPT methods causes confusion. The aim of this study is to review more than sixty-two MPPT methods that have been used in TEGs in the last six years and have the potential to be adapted for TEGs and provide a reference for researchers. Eventually, this review will be a resource that introduces the next generation MPPT methods, presents MPPT methods with the potential to be adapted to TEGs, and will be a good reference for future studies.
... Thermoelectric conversion is also known as temperature differential power generation. A typical temperature differential power generation device consists of multiple Π-type thermoelectric units connected in electrical series and thermal parallel, where the Π-type thermoelectric unit consists of ntype and p-type electric couple arms connected to the hot and cold end electrodes [4] , as shown in Figure 4. [4] According to the Seebeck effect [5] , when there is a temperature difference ΔT between the two ends of a thermoelectric device, an electric potential V is generated： (10) A current is then generated in the circuit： ( 1 1 ) This gives the electrical power as： (12) Where: S np is the total Seebeck coefficient of the n-and p-type thermocouple arm thermoelectric material. R is the internal resistance of the thermoelectric device. ...
A new microwave energy reception method is proposed for the wireless energy transmission needs of lunar rovers combined with the lunar environment, i.e. collecting thermal energy through microwave absorbing materials, and then converting thermal energy into direct current by using temperature difference power generation devices. The article analyses the two conversion processes, microwave-thermal and thermal-DC, separately. Under the approximate condition that the temperature at both ends of the absorbing material is regarded as equal, the two conversion processes are linked by energy conservation, which theoretically leads to the temperature and total efficiency of the system at steady state. The temperature and total efficiency of the system are initially obtained by numerical simulation with respect to the thickness of the absorbing material, the receiving area and the input power density by selecting the parameters of the carbon and iron composite material at 10 GHz. The results show that there is an optimum thickness of absorbing material for a certain input power density and receiving area, which results in the highest system efficiency. The larger the receiving area and input power density in a certain range, the higher the efficiency, but beyond a certain range the system efficiency shows a decreasing trend. Also the theory and the actual will produce a large deviation when temperature is high. The article concludes that this energy receiving method has great potential for application in the space environment based on the excellent wave absorbing materials and thermoelectric components but further research is needed.
... Where int k is the thermal conductance given as (Montecucco, Siviter, and Knox 2015); (Dalola et al. 2009) . ...
A novel technique for waste heat recovery in solar thermal power generation is investigated through experimentation and systematically presented. Power generation using Thermoelectric Generator (TEG) is a promising technique in waste heat recovery application. In this topology, TEG array is directly attached to the back of the solar Photovoltaic panel (model AP-AM15) to receive the transmitted heat at the back of the PV panel as waste heat. More so, a circulating water-heat sink is attached to the TEG cold side to improve the temperature gradient. Base on Seebeck effect, the TEG directly converts the temperature difference into electricity. The experimental result shows that efficiency between the range of 2.1% and 4.7% for the conventional cooling system while the output power approximately ranges between 0.05W and 0.47W, the circulating water-heat sink technique has efficiency ranging between 2.9% and 10.3% with output power between the range of 0.10W and 2.2W. The daily average increase in efficiency was found to be 263.76%. This shows that the daily average power is improved by a factor of 2.6376 with the water circulating water-heat sink technique. This is an indication of waste heat recovery from the solar thermal power generation.
... Above literatures focus on performance of TEG affected by heat transfer, there are also several other reports concerning the backward effect of generated current. This generated current could induce an additional heat flow based on conventional Peltier effect, decreasing the effective temperature difference of TEG [32,33]. Such Peltier effect would simultaneously reduce the Seebeck voltage and output power, weakening the Seebeck effect [34]. ...
Thermoelectric generator (TEG) has been proved as a promising technology for directly converting heat into electricity based on Seebeck effect. On the contrary, this electricity can trigger a solid-state cooling based on conventional Peltier effect. However, these two effects induce a coupling between heat and electric flux, especially for the quantitative relationship still remaining a mystery. Here, we show experimental evidence and theoretical calculation for the coupling by monitoring transient response of fluid temperature and output power. The experimental maximum heat flow in open circuit is 1162 W at cold fluid flow rate V̇c = 0.3 m³/h and fluid temperature difference ΔTf = 70 °C, enhanced by 13% owing to heat compensation from intrinsic coupling in closed-loop circuit. Meanwhile, the measured maximum output power of TEG is 18.2 W, and subsequently decreases to 15.4 W due to the objective existence of coupling. This double-edged sword in coupling vigorously inspires the potential applications in heat-dissipation situation such as spacecraft, electronic components, photovoltaic, refrigerator and etc. Present findings open a novel avenue for manipulating heat-electricity conversion in practical engineering.
... A research study [21] used a simulation tool for thermoelectric generators based on steady-state equations and experimental evidence to investigate the efficiency of TEGs with continuous heat through them, and to find the optimal geometric configuration, leading to better performance and lowest material expense. The authors also introduced the electrical characterisation of TEGs for constant-heat and explored the relationship between the maximal power point and the open-circuit voltage, the maximum strength of TEGs with legs of various sizes and numbers and packing factors for different heights. ...
In this work, computational modelling and performance assessment of several different types of variable thermoelectric legs have been performed under steady-state conditions and the results reviewed. The study conducted has covered geometries, not previously analysed in the literature, such as Cone-leg and Diamond-leg, based on the corresponding thermoelectric generator leg shape structure. According to the findings, it has been demonstrated that the inclusion of a variable cross-section can have an impact on the efficiency of a thermoelectric generator. It has been concluded that the Diamond configuration generated a slightly larger voltage difference than the conventional Rectangular geometry. In addition, for two cases, Rectangular and Diamond configurations, the voltage generated by a TEG module consisting of 128 pairs of legs was analysed. As thermal stress analysis is an important factor in the selection of TEG leg geometries, it was observed based on simulations that the newly implemented Diamond-leg geometry encountered lower thermal stresses than the traditional Rectangular model, while the Cone-shape may fail structurally before the other TEG models. The proposed methodology, taking into account the results of the simulation carried out, provides guidance for the development of thermoelectric modules with different forms of variable leg geometry.
