Search Results (825)

Semiconducting single-walled carbon nanotubes (SWCNTs) are significantly attractive for thermoelectric generators (TEGs), which convert thermal energy into electricity via the Seebeck effect. This is because the characteristics of semiconducting SWCNTs are perfectly suited for TEGs as self-contained power sources for sensors on the Internet of Things (IoT). However, the thermoelectric performances of the SWCNTs should be further improved by using the power sources. The ideal SWCNTs have a high electrical conductivity and Seebeck coefficient while having a low thermal conductivity, but it is challenging to balance everything. In this study, to improve the thermoelectric performance, we combined two types of SWCNTs: one with a high electrical conductivity (Tuball 01RW03, OCSiAl) and the other with a high Seebeck coefficient and low thermal conductivity (ZEONANO SG101, ZEON). The SWCNT inks were prepared by mixing two types of SWCNTs using ultrasonic dispersion while varying the mixing ratios, and p-type SWCNT films were prepared using vacuum filtration. The highest dimensionless figure-of-merit of 1.1 × 10⁻³ was exhibited at approximately 300 K when the SWCNT film contained the SWCNT 75% of SWCNT (ZEONANO SG101) and 25% of SWCNT (Tuball 01RW03). This simple process will contribute to the prevalent use of SWCNT-TEG as a power source for IoT sensors. Full article

This systematic review outlines the application of thermoelectric generators (TEGs) as energy sources in CubeSats. While CubeSats currently rely on solar cells with efficiencies between 16.8% and 32.2%, their performance diminishes with increased distance from the Sun. TEGs, although used in radioisotope thermoelectric generators (RTGs) for satellites, remain underutilized in CubeSats. A literature review revealed 33 relevant articles, with 21.2% employing simulation software to evaluate thermal behavior. Among 34 patents, only one mentioned micro-TEGs, with most focusing on structural improvements. Patent activity peaked between 2016 and 2020, emphasizing structural and thermal optimization, but no patents addressed TEGs as energy sources for CubeSats, highlighting a significant research gap. TEGs present a viable solution for harnessing residual heat in CubeSats. Full article

This study analyzes the influence of the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) on the Mars Environmental Dynamics Analyzer (MEDA) station located on board the Perseverance rover (Mars 2020). A novel visualization methodology was developed using a hydrodynamic towing tank and 3D-printed models created through additive manufacturing. This experimental approach, not previously applied in this context, proved to be a cost-effective alternative for studying thermal interactions while providing accurate preliminary insights into the behavior of thermal plumes under Martian-like conditions. Key factors such as the extremely low Reynolds number, an increasing temperature of the model, and atmospheric properties similar to those in Mars were incorporated. The findings suggest that the MMRTG’s thermal plume may significantly influence MEDA’s performance due to the plume’s height and its interaction with the surrounding environment. Full article

Radio photonic technologies have emerged as a promising solution for addressing microwave frequency synthesis challenges in current and future communication and sensing systems. One particularly effective approach is the optoelectronic oscillator (OEO), a simple and cost-effective electro-optical system. The OEO can generate microwave signals with low phase noise and high oscillation frequencies, often outperforming traditional electrical methods. However, a notable disadvantage of the OEO compared to conventional signal generation methods is its significant frequency tuning step. This paper presents a novel approach for continuously controlling the output frequency of an optoelectronic oscillator (OEO) based on integrated photonics. This is achieved by tuning an integrated optical delay line within a feedback loop. The analytical model developed in this study calculates the OEO’s output frequency while accounting for nonlinear errors, enabling the consideration of various control schemes. Specifically, this study examines delay lines based on the Mach–Zehnder interferometer and microring resonators, which can be controlled by either the thermo-optic or electro-optic effect. To evaluate the model, we conducted numerical simulations using Ansys Lumerical software. The OEO that utilized an MRR-based electro-optical delay line demonstrated a tuning sensitivity of 174.5 MHz/V. The calculated frequency tuning sensitivity was as low as 6.98 kHz when utilizing the precision digital-to-analog converter with a minimum output voltage step of 40 μV. The proposed approach to controlling the frequency of the OEO can be implemented using discrete optical components; however, this approach restricts the minimum frequency tuning sensitivity. It provides an additional degree of freedom for frequency tuning within the OEO’s operating range, which is ultimately limited by the amplitude-frequency characteristic of the notch filter. Thus, the proposed approach opens up new opportunities for increasing the accuracy and flexibility in generating microwave signals, which can be significant for various communications and radio engineering applications. Full article

Since circuit-based solutions for increasing the efficiency of Class AB audio amplifiers have reached their peak, this article presents a non-circuit-based approach for the same purpose. The output transistors of this class of amplifiers dissipate a significant amount of thermal energy, resulting in relatively low amplifier efficiency and requiring the transistors to be mounted on large heatsinks. This study was conducted with the aim of capturing the waste heat energy dissipated by the output transistors and converting it into electrical energy using thermoelectric generators (TEGs), which can then be used to increase the efficiency of the amplifier system. In addition to improving efficiency, this study aims to determine the extent to which heatsinks with smaller dimensions can be used in combination with the amplifier through the use of TEGs, potentially leading to a wider commercial application of Class AB audio amplifiers. The experimental results show that the thermoelectric conversion efficiency of TEGs reached 1.097% in the best case, indicating a potential increase of 0.275% in the overall efficiency of the amplifier system. These results show that the low thermoelectric efficiency of TEGs is a limiting factor that prevents a breakthrough in improving the efficiency of the power amplifier system with the proposed non-circuit-based approach. Full article

Direct harvesting of abundant solar thermal energy within organic phase-change materials (PCMs) has emerged as a promising way to overcome the intermittency of renewable solar energy and pursue high-efficiency heating-related applications. Organic PCMs, however, generally suffer from several common shortcomings including melting-induced leakage, poor solar absorption, and low thermal conductivity. Compounding organic PCMs with single-component carbon materials faces the difficulty in achieving optimized comprehensive performance enhancement. Herein, this work reports the employment of hybrid expanded graphite (EG) and carbon nanotubes (CNTs) to simultaneously realize leakage-proofness, high solar absorptance, high thermal conductivity, and large latent heat storage capacity. The PCM composites were prepared by directly mixing commercial high-temperature paraffin (HPA) powders, EG, and CNTs, followed by subsequent mechanical compression molding. The HPA-EG composites loaded with 20 wt% of EG could effectively suppress melting-induced leakage. After further compounding with 1 wt% of CNTs, the form-stable HPA-EG20-CNT1 composites achieved an axial and in-plane thermal conductivity of 4.15 W/m K and 18.22 W/m K, and a melting enthalpy of 165.4 J/g, respectively. Through increasing the loading of CNTs to 10 wt% in the top thin layer, we further prepared double-layer HPA-EG-CNT composites, which have a high surface solar absorptance of 92.9% for the direct conversion of concentrated solar illumination into storable latent heat. The charged composites could be combined with a thermoelectric generator to release the stored latent heat and generate electricity, which could power up small electric devices such as light-emitting diodes. This work demonstrates the potential for employing hybrid fillers to optimize the thermophysical properties and solar thermal harvesting performances of organic PCMs. Full article

This paper introduces a novel thermoelectric generator (TEG)-powered Industrial Internet of Things (IIoT) device that addresses key limitations in the detection of steam leaks in industrial steam pipelines, particularly in steam traps. Existing solutions often rely on battery-powered or wired sensors, which are limited by high maintenance costs, short lifespans, or significant infrastructure investments. The proposed device operates without batteries, using waste heat to provide continuous power, and leverages LoRaWAN for long-range wireless communication, minimizing reliance on costly internal infrastructure. Additionally, the device integrates temperature differential (ΔT) and ultrasonic sensors with edge computing capabilities to enhance real-time leak detection and reduce dependency on cloud computing. By enabling precise, low-maintenance monitoring of steam systems in energy-intensive industries (e.g., petrochemical, pharmaceutical), this technology can significantly reduce energy losses, operational costs, and greenhouse gas emissions. Initial testing demonstrates the device’s ability to detect leaks accurately under varying industrial conditions, offering a robust, scalable solution for Industry 4.0 applications. Full article

Perovskites are currently becoming common in the field of optoelectronics, owing to their promising properties such as electrical, optical, thermoelectric, and electronic. Although mechanical and thermal properties also play a crucial part in the functioning of the optoelectronic devices, they have scarcely been explored. The present work performed an ab initio study of the mechanical and thermal properties of the cubic EuAlO₃ and GdAlO₃ perovskites for the first time using density functional theory. Quantum Espresso and Themo_pw codes were utilized by employing the generalized gradient approximation. Although the results showed that both materials have good mechanical and thermal properties that are ideal for the above–mentioned applications, EuAlO₃ possessed better structural and thermal stability, bulk modulus, Poisson ratio, thermal expansion coefficient, and thermal stress; while GdAlO₃ possessed better Young’s modulus and shear modulus. Moreover, the mechanical properties of the two materials turned out to be much better than those of the common materials for optoelectronic applications, while their thermal properties were comparable to that of sapphire glass. Since this study was computational, an experimental verification of the computed properties of the two materials needs to be carried out before they can be commercialized. Full article

The aircraft smart skin (ASS) with structural health monitoring capabilities is a promising technology. It enables the real-time acquisition of the aircraft’s structural health status and service environment, thereby improving the performance of the aircraft and ensuring the safety of its operation, which in turn reduces maintenance costs. In this paper, a miniaturized and ultra-low-power wireless multi-parameter monitoring system (WMPMS) for ASS is developed, which is capable of monitoring multiple parameters of an aircraft, including random impact events, vibration, temperature, humidity, and air pressure. The system adopts an all-digital monitoring method and a low-power operating mechanism, and it is integrated into a low-power hardware design. In addition, considering the airborne resources limitations, an energy self-supply module based on a thermoelectric generator (TEG) is developed to continuously power the system during flight. Based on the above design, the system has a size of only 45 mm × 50 mm × 30 mm and an average power consumption of just 7.59 mW. Through experimental validation, the system has excellent performance in multi-parameter monitoring and operating power consumption, and it can realize the self-supply of energy. Full article

In this paper, a new approach is proposed to improve the performance of the LNG regasification process in a geothermal-transcritical CO₂–LNG cycle by using thermoelectric generators. Energy and exergy analyses were applied to the proposed system and the plant’s performance is compared with the conventional CO₂–LNG cycle. To achieve the optimal solution for the system, a multi-objective optimization technique based on a genetic algorithm is used. This study’s findings revealed that in the conventional CO₂–LNG cycle, the highest exergy destruction occurs in the preheater. However, integrating a thermoelectric generator allows a portion of this destroyed exergy to be converted into power. The proposed system demonstrated 2% less exergy destruction compared to the conventional system. Moreover, the TEG contributes additional power, increasing the net output power of the system by 24%. This improvement ultimately enhances the overall exergy efficiency of the system. The analysis also concluded that, although a lower LNG mass flow rate reduces the system’s net power output, it improves the exergy efficiency. Overall, the proposed system exhibits an 8.37% higher exergy efficiency and a 24.22% greater net output power compared to the conventional CO₂–LNG cycle. Full article

As the need to monitor agriculture parameters intensifies, the development of new sensor nodes for data collection is crucial. These sensor types naturally require power for operation, but conventional battery-based power solutions have certain limitations. This study investigates the potential of harnessing the natural temperature gradient between soil and air to power wireless sensor nodes deployed in environments such as agricultural areas or remote off-grid locations where the use of batteries as a power source is impractical. We evaluated existing devices that exploit similar energy sources and applied the results to develop a state-of-the-art device for extensive testing over a 12-month period. Our main objective was to precisely measure the temperature on a thermoelectric generator (TEG) (a Peltier cell, in particular) and assess the device’s energy yield. The device harvested 7852.2 J of electrical energy during the testing period. The experiment highlights the viability of using environmental temperature differences to power wireless sensor nodes in off-grid and battery-constrained applications. The results indicate significant potential for the device as a sustainable energy solution in agricultural monitoring scenarios. Full article

A large amount of energy can accumulate and be stored during underground coal fires. As thermal energy cannot be easily removed using the traditional technologies of fire prevention and extinguishment, there is a potential benefit to collecting and utilizing thermal energy from coal fires and converting it to electrical energy. Thus, this work proposes a thermoelectric generator as a solution to convert thermal energy from coal fires to electrical energy. To improve the thermal energy conversion efficiency, an experimental test system was established using a thermosyphon, an electric heating module, a cooling circulation module, a thermoelectric module, and a data acquisition module. Under the condition of ensuring the same input heat and cooling boundary conditions, the influence of three factors, namely the cooling method, the connection method, and the coverage rate of thermoelectric devices, on the performance of the coal fire waste heat conversion system was studied. The results show that, compared with air cooling, water cooling provides a greater temperature difference for the thermoelectric module, and the maximum temperature difference can reach 65.90 °C. Series connection between thermoelectric devices will generate a higher open-circuit voltage and output voltage. The maximum horizontal open-circuit voltage value can reach 3.34 V, and the maximum output voltage is 2.61 V. Compared with the coverage rates of thermoelectric devices of 15.0% and 30.0%, the output power under the coverage rate of 22.5% is the largest at 0.35 W, and its thermoelectric conversion efficiency is also the largest at 0.35%. The optimal combination of thermoelectric modules obtained from the research results can provide ideas for the application of in situ coal fire prevention and control. Full article

This research focuses on analyzing the aerodynamic characteristics of residual air currents generated by vehicle movement and evaluating their feasibility for energy generation, then designing a vertical axis wind turbine. The parameters assessed include the characteristic velocity profile, the average and maximum velocities, disturbance lifetimes, as well as the frequency and probability of recurrence of these disturbances. Using the data, projections are made on the electrical energy amount that can be produced by a wind turbine operating under such wind conditions. Measurements were taken at four locations: three within Mexico City (CDMX) and one on the outskirts. The measurement station, consisting of a 2.35 m vertical tower equipped with eight vertically aligned thermos-resistive anemometers, is installed on medians less than 0.50 m from moving vehicles. The data from within CDMX show maximum wind velocities ranging from 6 to 8 m/s at ground level, while measurements on the outskirts record velocities of up to 19.5 m/s. A probabilistic analysis reveals that usable air currents could be present 58% of the time. Based on electrical production calculations, it is estimated that harnessing this residual energy could power approximately 4500 homes, considering the national cost per kWh and the average electricity consumption of a four-person household. Full article

Bi₂Te₃-based alloys are representatively commercialized thermoelectric materials for refrigeration and power generation. Refrigeration mainly utilizes thermoelectric properties near room temperature, while the power generation temperature is relatively high. However, it is difficult for bismuth telluride to maintain good thermoelectric properties throughout the entire temperature range of 300–500 K. Herein, a series of Bi_xSb_2−xTe₃ alloys with different Bi contents were prepared by a simple preparation method and systematically investigated, and their best application temperature range was found. The Bi content can modulate carrier concentration and band gap, and the maximum dimensionless figure of merit (ZT) value of Bi_xSb_2−xTe₃ can be achieved in the corresponding application temperature range. The maximum ZT of Bi_0.3Sb_1.7Te₃ with a Bi content equal to 0.3 reaches 1.14 at 400 K, and the average ZT is 1.06 in the range of 300–500 K, which is suitable for both power generation and refrigeration. Therefore, power generation technologies with higher application temperatures should be selected from Bi_xSb_2−xTe₃ materials with Bi content less than 0.3, and refrigeration technologies with lower application temperatures should be selected with Bi content greater than 0.3. This work provides experimental guidance for finding the composition of Bi₂Te₃-based alloys in scientific research and practical applications. Full article

This study developed a novel 3D-printable poly(vinylidene fluoride) (PVDF)-based nanocomposite incorporating 6 wt% graphene nanoplatelets (GNPs) with programmable characteristics for resistive heating applications. The results highlighted the significant effect of a controlled printing direction (longitudinal, diagonal, and transverse) on the electrical, thermal, Joule heating, and thermo-resistive properties of the printed structures. The 6 wt% GNP/PVDF nanocomposite exhibited a high electrical conductivity of 112 S·m⁻¹ when printed in a longitudinal direction, which decreased significantly in other directions. The Joule heating tests confirmed the material’s efficiency in resistive heating, with the maximum temperature reaching up to 65 °C under an applied low voltage of 2 V at a raster angle of printing of 0°, while the heating T_max decreased stepwise with 10 °C at the 45° and the 90° printing directions. The repeatability of the Joule heating performance was verified through multiple heating and cooling cycles, demonstrating consistent maximum temperatures across several tests. The effect of sample thickness, controlled by the number of printed layers, was investigated, and the results underscore the advantages of programmable 3D printing orientation in thin layers for enhanced thermal stability, tailored electrical conductivity, and efficient Joule heating capabilities of 6 wt% GNP/PVDF composites, positioning them as promising candidates for next-generation 3D-printed electronic devices and self-heating applications. Full article