Thermoelectric System Research Articles

Ultrafast Response and Threshold Adjustable Intelligent Thermoelectric Systems for Next-Generation Self-Powered Remote IoT Fire Warning

HighlightsThe flexible single-walled carbon nanotube/titanium carbide composite films exhibit excellent thermoelectric (TE), high-temperature stable and flame-retardant properties.The assembled TE device achieves an ultrafast fire warning response time of ~ 0.1 s with a threshold voltage of 1 mV.The fire warning device demonstrates exceptional repeatability and long-term stability.The designed intelligent system is promising for next-generation self-powered remote IoT fire warning applications.

Flexible Thermoelectric Wearable Architecture for Wireless Continuous Physiological Monitoring.

Continuous monitoring of physiological signals from the human body is critical in health monitoring, disease diagnosis, and therapeutics. Despite the needs, the existing wearable medical devices rely on either bulky wired systems or battery-powered devices needing frequent recharging. Here, we introduce a wearable, self-powered, thermoelectric flexible system architecture for wireless portable monitoring of physiological signals without recharging batteries. This system harvests an exceptionally high open circuit voltage of 175-180 mV from the human body, powering the wireless wearable bioelectronics to detect electrophysiological signals on the skin continuously. The thermoelectric system shows long-term stability in performance for 7 days with stable power management. Integrating screen printing, laser micromachining, and soft packaging technologies enables a multilayered, soft, wearable device to be mounted on any body part. The demonstration of the self-sustainable wearable system for detecting electromyograms and electrocardiograms captures the potential of the platform technology to offer various opportunities for continuous monitoring of biosignals, remote health monitoring, and automated disease diagnosis.

Harnessing solar power: Innovations in nanofluid-cooled segmented thermoelectric generators for exergy, economic, environmental, and thermo-mechanical excellence

Addressing the imperative need for advancements in thermoelectric generation, this study pioneers an analysis of nanofluid-cooled solar segmented thermoelectric generators with non-uniform cross-sections. Insights into thermal management, structural integrity, and economic efficiency in thermoelectric systems are provided, employing a numerical model that accurately represents thermoelectric effects by accounting for temperature dependencies of semiconductor materials. Through research, exploration of diverse coolant strategies, including TiO2, Fe3O4, Al2O3, and graphene, offers key insights into their impact on cooling dynamics. Findings demonstrate that graphene nanofluid, operating at a flow velocity of 2 m/s, outperforms others, achieving optimal power generation of 221.77 mW and an exergy efficiency of 8.99 %. Additionally, at a concentrated irradiance of 595 kWm−2, graphene leads in environmental benefits, with the highest CO2 savings of 0.38 kgyr−1, and demonstrates economic advantages with a cost-effective dollar per mW value of 3.79×10−6 $mW−1. Furthermore, the study verifies the structural integrity of these systems, with graphene achieving an optimal von Mises stress of 1.35 GPa at a semiconductor height of 0.2 mm. These advancements contribute to environmentally friendly and high-performance generators for sustainable energy solutions, paving the way for future innovations in thermoelectric technology.

Golden ratio of the r+/r- for the structure-selectivity in the thermoelectric BaZn2-xCdxSb2 system

A total of five Zintl phase compounds in the solid-solution BaZn2-xCdxSb2 (0.10(2) ≤ x ≤ 2) system have been successfully synthesized by the molten Pb-flux method. Both powder X-ray and single-crystal X-ray diffraction analyses proved that the title compounds displayed the phase transition between the BaCu2S2-type phase (space group Pnma, Z = 4) and the CaAl2Si2-type phase (space group P3¯m1, Z = 1) depending on the Zn/Cd mixed ratio. Furthermore, this kind of structure selectivity was dictated by the radius ratio criterion between the cationic and the anionic elements (r+/r–): three Zn-rich compounds with the r+/r– > 1 (BaZn1.90(1)Cd0.10Sb2, BaZn1.75(2)Cd0.25Sb2, and BaZn1.62(2)Cd0.38Sb2) preferred to adopt the BaCu2S2-type phase, while two Cd-rich compounds with the r+/r– ≤ 1 (BaZn0.16(2)Cd1.84Sb2 and BaCd2Sb2) preferred to crystallize in the trigonal CaAl2Si2-type phase. A series of TB-LMTO calculations using the two hypothetical models: BaZn1.5Cd0.5Sb2 and BaZn0.5Cd1.5Sb2, proved that a resonance peak in the density of states of BaZn1.5Cd0.5Sb2 implied the enhanced Seebeck coefficient of the three Zn-rich compounds, and the reduction of band gap observed in a band structure of BaZn0.5Cd1.5Sb2 influenced the electrical conductivity of the Cd-rich BaZn0.16(2)Cd1.84Sb2. Temperature-dependent thermoelectric property measurements showed the maximum ZT of 0.54 for the quaternary BaZn1.62(2)Cd0.38Sb2, which should mainly be attributed to the reduced κtot due to the Zn and Cd disordering in the anionic frameworks.

Thermoelectric-Powered Remote Sensor for Frost Detection

This article proposes the use of a thermoelectric system as an energy-harvesting device for use in industrial refrigeration units. The energy generated by the device in this study can be used for remote, low-power applications, such as frost detection sensors. The accumulation of frost on the surfaces of evaporators causes inefficiency in the operation of refrigeration units by reducing the heat exchange rate. To revert this condition, the evaporator must be defrosted periodically. The proposed energy-autonomous sensors can be localized in key places to minimize not only the number of defrosting operations but also their duration. These sensors can transmit data wirelessly so that the control systems can better determine the ideal time to perform defrosting operations. This device eliminates the need for complex cable routing in long systems, where these components are often located far apart or in hard-to-reach places. The outcomes of this research not only offer solutions to a prevailing issue in refrigeration units but also aid in formulating strategies for optimally placing ice formation detection sensors. Additionally, these findings may boost overall refrigeration efficiency while cutting down on installation and maintenance costs.

Bi2Te3-based flexible thermoelectrics

Bi2Te3-based materials stand out as the top-performing material for thermoelectric applications at room temperature. However, its inherent rigidity has posed challenges for widespread usage in flexible thermoelectric conversion systems. Recent endeavors have focused on achieving Bi2Te3-based flexible films through bulk thinning, physical/chemical deposition, paste casting, as well as the template method. These efforts have led to a surge in research publications. This review aims to offer a comprehensive update on the synthesis approaches, microstructures, thermoelectric performances/flexibility, and the underlying mechanisms. Future research should focus on investigating innovative deposition techniques, exploring new composite phases/templates, refining fabrication parameters, and among others, to enhance the thermoelectric performances as well as flexibility.

Investigating the power and efficiency of the 3D model of the concentrated photovoltaic thermoelectric hybrid system and estimating the power consumption of the water pump for cooling

Solar energy is one of the most useful types of renewable energy. Solar cells are being used to convert solar energy into electricity. By focusing the radiation on the cells, more energy is radiated in a smaller area of the cell which is called concentrated photovoltaic (CPV). Due to the concentration of radiation, the temperature of the cell rises which can be converted into electricity through thermoelectric generators (TEG). The present study is a hybrid system of solar cell, thermoelectric generator, and heat exchanger (CPV-TEG). By this survey being created, it was revealed that the combined power produced by the CPV-TEG reaches its maximum value at concentration ratio of 40. This increase continues with the increase in fluid flow rate. however, according to the power consumption of the pump, it was observed that in all types of heat exchangers, an increase in flow rate of more than 8 liters per hour reduces the output power of the system. The replacement of the secondary heat exchanger with the primary one illustrated that the increase of the channels in the exchanger, despite the increase in the power consumption of the pump, causes a very small increase in the output power and efficiency of the system. Moreover, replacing the tertiary heat exchanger instead of the secondary exchanger showed that changing the direction of fluid output increases the power consumption of the pump in high flow rates.

Advancing sustainable cooling: Performance analysis of a solar-driven thermoelectric refrigeration system for eco-friendly solutions

The solar-powered thermoelectric refrigerator (SPTR) is an innovative approach that uses solar energy to cool spaces. Its effectiveness relies on solar insolation rates and an intelligent dual-axis solar tracking system (STS) that maximizes solar energy capture. Performance analysis of SPTR with the fixed panel solar system (WST) and dual-axis STS by keeping the SPTR at a standard ambient temperature of 25 °C was carried out under local climate conditions. The experimental test setup includes a thermoelectric refrigerator (TER), thermoelectric module (TEM), solar panels, and STS. The experimental findings showed that the coefficient of performance (COP) of SPTR depends on the solar irradiance, the system's input power, the surface temperature of the solar panels, and the cooling rate. The maximum and minimum values of COPs were 1.19 and 0.27 for directly coupled SPTR with a WST and 2.07 and 0.39 for STS, respectively. Compared with the stand-still solar system, a COP enhancement of 44–75 % is achieved. The results also show that the cooling load is a function of the refrigerated space, and the products are to be cooled, which is affected by the thermoelectric properties of the TEM. The cooling rate is recorded at its maximum when the system is operated using an STS on a clear sunny day with a maximum solar insolation rate. The SPTR has proven to be environmentally friendly, the best alternative to conventional cooling systems, and sustainable due to the independence of traditional energy resources.

Thermoelectric system investigation with the combination of solar concentration, greenhouse and radiative cooling for all-day power generation

Thermoelectric generator (TEG) can utilize solar heating to generate electricity without any fossil fuel consumption. However, conventional solar driven TEG fails to achieve high efficiency power generation for 24-h, due to the losing of solar concentration at the hot end and additional cooling capability at the cold end. Therefore, a novel TEG system with the combination of solar concentration, greenhouse and radiative cooling is proposed. With the aim to significantly increase the temperature of hot end, a dish-type concentrator is introduced to concentrate solar radiation and a greenhouse seals up heat. Radiative cooling panel is used to decrease the temperature of cold end, which can realize temperature differences of TEG at night. The eight-day outdoor experimental test indicates that the thermoelectric system achieves a maximum temperature difference of 47.5 °C and a voltage output of 1293.8 mV. The system attains the average power outputs of 3.6 W/m2 on sunny and 0.16 W/m2 on cloudy. Moreover, even at the nights of high humidity and low temperature, the system also achieves a maximum power output of 0.08 W/m2, which can enable continuous power generation throughout the day. This innovative TEG system presents a viable strategy for powering small-scale devices in remote areas.

Experimental insights into thermoelectric freezer systems: Feasibility and efficiency

This study presents an experimental investigation into the operational performance of a thermoelectric (TE) freezer system. A freezer unit is composed of two-stage thermoelectric modules, an aluminum plate fin heat exchanger sink with fans positioned either on top or directing airflow through the center, and a cooling block incorporating circulating icy water for heat dissipation. Three distinct configurations, featuring varying numbers of freezer units and fan arrangements, underwent testing using a 300-liter freezer prototype under typical room conditions, specifically at 21 °C. The findings illustrate that the minimum temperature inside the freezer cabinet can achieve −16.0 °C across all configurations. Moreover, the cooling capacity can reach up to 74.7 W, with the thermoelectric coefficient of performance (COP) achieving a maximum of 0.45, while the system COP ranges from 0.23 to 0.28. The minimum TE power consumption and TE system power consumption are recorded at 138.8 W and 174.4 W, respectively, suggesting feasibility for practical residential freezer applications. This investigation sets the stage for the development of TE freezers integrated with ice thermal storage applications.

Thermal, Energy and Exergy Analysis of Thermoelectric Generator System for Waste Heat Recovery Applications

Thermal, Energy and Exergy Analysis of Thermoelectric Generator System for Waste Heat Recovery Applications

Development and Experimental Validation of a Two-stage Thermoelectric Heat Pump Computational Model for Heating Applications

The utilisation of thermoelectric technology as a heat pump in heating applications necessitates comprehensive investigation. The scalable nature of thermoelectric technology enables its operation at elevated temperatures without the requirement of refrigerants. In this work, an accurate computational model that can simulate one- and two-stage thermoelectric heat pumps is developed. This model uses the electric-thermal analogy and the finite difference method, including the thermoelectric effects, temperature dependent properties, thermal contact resistances and all heat exchangers, even the intermediate heat exchanger in the case of a two-stage configuration. Moreover, the model has been experimentally validated by built and tested prototypes, being the first time that a two-stage thermoelectric heat pump model is experimentally validated.The discrepancy between the simulated and experimental results is below the ± 10 % for COP, ± 8 % for generated heat and temperature lift in the airflow, and less than the ± 6 % for consumed power. Additonally, the model simulates real tendencies under different operating conditions, proving the reliability of the developed thermoelectric heat pump model.Finally, the model is used to optimise a thermoelectric system combining one- and two-stage thermoelectric heat pumps, and hybridising them with electric resistances. An airflow of 16.5 m3/h is heated from 25 °C to 160 °C, achieving a maximum COPtot of 1.21. Lastly, the importance of considering the thermal resistances of the heat exchangers is computationally modelled and demonstrated. Not taking them into account would overestimate the performance of the TEHP system by more than the 7 %.

Effect of substrate temperature and electrolyte composition on the fabrication of through-hole porous AAO membrane with SF-MDC

Fabrication of novel nanostructure materials on various metal substrates receives large attensions for numerous industrial applications. In this research, the influence of substrate temperature and electrolyte composition on pore parameters and oxide film thickness of anodic porous alumina (AAO) were studied. A 3D-printed solution-flow type microdroplet cell (SF-MDC) was used for the fabrication of AAO membranes in aluminum substrate. Alumina lines were formed at a constant applied voltage. The temperature of the substrate was controlled with a thermoelectric Peltier device system in the range of 10 °C to 60 °C. The surface and cross-section morphology of the anodic oxide lines were observed using a scanning electron microscope (SEM). The result showed that the pore diameter and interpore distance of the anodized lines increased as the substrate temperature increased. A highly ordered with hexagonal pore arrangement and lowest film thickness were obtained at the highest substrate temperature of 60 °C. The porous AAO membrane film thickness formed in the oxalic acid electrolyte increased from 32.2 μm to 52.5 μm as the anodizing substrate temperature reached 30 °C and then declined to 12.8 μm with increasing temperature to 60 °C. A through-hole porous AAO membranes were successfully fabricated at constant applied voltage and room temperature in oxalic and phosphoric acid without chemical etching.

Expression of Concern for article entitled “Cooling a plate lithium-ion battery using a thermoelectric system and evaluating the geometrical impact on the performance of heatsink connected to the system”

Expression of Concern for article entitled “Cooling a plate lithium-ion battery using a thermoelectric system and evaluating the geometrical impact on the performance of heatsink connected to the system”

IoT-driven monitoring and controlling to improve performance of thermoelectric air conditioning system

Thermoelectric module-based air conditioners (TEM-AC) are scalable, reliable, and have the potential to replace conventional air conditioners. However, the coefficient of performance (COP) of TEM-AC is still relatively low. Improving the COP requires a combination of temperature control, voltage control, heat recovery, airflow control, and material selection. The present study focuses on enhancing COP of the TEM-AC for building space cooling. To control and monitor the parameters of the TEM-AC, a low-cost, IoT-enabled monitoring and controlling system (MCS) is developed. The MCS helps in TEM-AC system designing as it can apply different current pulses to improve cooling capacity and control the temperature difference between both surfaces. MCS also measure all the required parameters of the TEM-AC to calculate the COP of the system and helps in reducing the calculation time for each experiment. Using a developed technique and TEM-AC design, a performance comparison of eight experimental cases has been done. Experiments have been performed in normal and control modes with different heat sinks and airflow of TEM-AC. The TEM-AC system is installed over a 16-inch × 12-inch enclosed space with a TEC-12706 module. The study indicates the COP of the system is enhanced by controlling the cold side temperature and air flow rate. For this study, maximum COP is achieved around 0.44 with control operation. The developed IoT-based monitoring and controlling system offers a promising solution for improving the performance of thermoelectric modules in building space conditioning applications.

Influence of Sputtering Power on the Properties of Magnetron Sputtered Tin Selenide Films.

The ecofriendly tin selenide (SnSe) is expected to find multiple applications in optoelectronic, photovoltaic, and thermoelectric systems. This work is focused on the thermoelectric properties of thin films. SnSe single crystals exhibit excellent thermoelectric properties, but it is not so in the case of polycrystalline bulk materials. The investigations were motivated by the fact that nanostructuring may lead to an improvement in thermoelectric efficiency, which is evaluated through a dimensionless figure of merit, ZT = S2 σ T/λ, where S is the Seebeck coefficient (V/K), σ is the electrical conductivity (S/m), λ is the thermal conductivity (W/mK), and T is the absolute temperature (K). The main objective of this work was to obtain SnSe films via magnetron sputtering of a single target. Instead of common radiofrequency (RF) magnetron sputtering with a high voltage alternating current (AC) power source, a modified direct current (DC) power supply was employed. This technique in the classical version is not suitable for sputtering targets with relatively low thermal and electrical conductivity, such as SnSe. The proposed solution enabled stable sputtering of this target without detrimental cracking and arcing and resulted in high-quality polycrystalline SnSe films with unprecedented high values of ZT equal to 0.5 at a relatively low temperature of 530 K. All parameters included in ZT were measured in one setup, i.e., Linseis Thin Film Analyzer (TFA). The SnSe films were deposited at sputtering powers of 120, 140, and 170 W. They had the same orthorhombic structure, as determined by X-ray diffraction (XRD), but the thickness and microstructure examined by scanning electron microscopy (SEM) were dependent on the sputtering power. It was demonstrated that thermoelectric efficiency improved with increasing sputtering power and stable values were attained after two heating-cooling cycles. This research additionally provides further insights into the DC sputtering process and opens up new possibilities for magnetron sputtering technology.

A Series Compensated Buck-Boost Converter-Based Thermoelectric Energy Harvesting System with Sliding Mode Controller

A thermoelectric generator (TEG) is a semiconductor-based device that can exhibit a flow of electric current through the external circuit if the sides of the TEG are subjected to a temperature difference caused by a heat source. The terminal voltage and the TEG’s internal resistance are altered depending on the temperature difference. Therefore, a suitable power electronic converter with a maximum power point tracking (MPPT) feature is required to harvest maximum power from the TEG and store the harvested energy in a battery-based energy storage system. This paper investigates a novel energy harvesting methodology from TEG using a series compensated buck-boost converter (SCBBC). MPPT has also been implemented using a sliding mode controller (SMC). A mathematical model of a TEG source has been developed in MATLAB-Simulink and tested with generic boost converter (GBC) and SCBBC for their dynamic performances during battery charging. The efficiency of conversion is found to be higher for SCBBC, at 97.87%. An experimental prototype has been developed with SCBBC and tested for two configurations, viz high voltage and low current configuration. The former configuration exhibits an efficiency of 86.3%, while the latter has an efficiency of 83%. The results indicate that SCBBC, along with SMC, opens up new efficient prospects for harvesting waste heat energy using TEGs.

Performance evaluation on a novel split thermoelectric system driven by solar energy for electric vehicle seats

This paper proposed a novel split thermoelectric system coupled with a photovoltaic panel for electric vehicle seats. The system separates the hot and cold ends of the thermoelectric device over a long distance with the flexible intermediate conductor, which solves the problem of poor heat dissipation at the hot end resulted from the integration of traditional TEC with the vehicle seats and improves the cooling and heating performance. A three-dimensional heat transfer model was established by COMSOL software to study the temperature field and the comprehensive performance. The results demonstrate that the system can maintain the seat temperatures in 27–30 °C in summer and 18–25 °C in winter, and there exists an optimum input power to maximize the COP. In addition, the seat temperature can be reduced from 60 °C to 31 °C in just 20 min under maximum heating load. The system performance is closely linked to the structure of the middle conductors, heat dissipation, solar radiation intensity, and ambient temperature. In winter, the power consumption of the system is reduced by about 84 % compared to the positive temperature coefficient thermistor with the COP being increased by 5.17. The contribution of the photovoltaic panel based on the studied conditions can save about 215.26 kWh of energy per year, and increase the driving distance of electric vehicles by approximately 1435 km.

Evaluation of the high-robustness nuclear power cycle against lunar surface environmental threat

Heat sinks exposed to the lunar surface environment cause fluctuations in the energy cycle due to variations in lunar thermal conditions, leading to non-design operations of the energy system. Such suboptimal operations decrease energy efficiency and shorten the lifespan of system components. This paper introduces an innovative design for a highly robust lunar nuclear power cycle that mitigates environmental threats on the lunar surface. A reverse closed Brayton cycle increases the waste heat discharge temperature. Higher waste heat temperatures allow the heat sink panels to have greater heat radiation per unit area, countering the negative disturbances from lunar environmental changes on the energy system. Under the dual threats of lunar dust toxicity and intense solar radiation, the output reduction of this robust nuclear cycle is only 0.96% that of traditional nuclear power cycles with the same thermoelectric parameters. Moreover, even under severe environmental threats, the power quality of this robust nuclear cycle remains 10.8 times better than that of conventional designs with the same nighttime output design baseline. In conclusion, employing a reverse Brayton cycle to increase waste heat emission temperature effectively enhances the robustness of the nuclear power cycle. This paper proposes a new nuclear thermoelectric system framework to withstand threats from the lunar surface environment.

Tuning band gaps in lead chalcogenides under pressure: implications for infrared detection applications

This study employs first-principle calculations within density functional theory (DFT) to explore the structural, electronic, optical, and thermoelectric properties of lead chalcogenides (PbS, PbSe, and PbTe). The investigation focuses on their potential application as infrared photodetectors, leveraging their narrow-band gap semiconductor characteristics. The influence of pressure on the band gap and various electronic, optical, and thermoelectric properties is thoroughly analyzed. The calculated band gap values for PbS, PbSe, and PbTe are determined to be 0.29 eV, 0.18 eV, and 0.18 eV, respectively, aligning well with experimental data. Notably, the study reveals non-linear changes in band gap values under pressure, with phase transitions observed at specific pressure thresholds in PbS and PbSe, but not in PbTe. Under varying pressure conditions, the optical peaks shift towards lower energy levels with increased intensity. The static dielectric constant of PbS, PbSe, and PbTe exhibits distinct variations within pressure ranges of 0–8 GPa. Transport coefficients (S, σ, ke) are calculated using semi-classical Boltzmann theory across different temperatures and pressures, indicating that heavier compounds exhibit higher electrical and thermal conductivity values. At 300 K, the maximum ZT values are determined to be 0.85, 0.8, and 0.52 for PbS, PbSe, and PbTe, respectively. The study suggests enhanced thermoelectric properties of these structures at lower temperatures, particularly highlighting PbS and PbSe as promising candidates for thermoelectric applications below 500 K. Exploring the impact of pressure on the thermoelectric parameters of lead chalcogenides reveals interesting trends, with PbTe demonstrating higher thermoelectric efficiency under increased pressure compared to PbS and PbSe. These findings provide valuable insights into the potential applications and performance of lead chalcogenides in IR detection and thermoelectric systems.