Search Results (219)

Interest in germanium electronic devices is experiencing a comeback thanks to their suitability for a wide range of new applications, like CMOS transistors, quantum technology or infrared photonics. Among these applications, Ge-based thermophotovoltaic converters could become the backbone of thermo-electrical batteries. However, these devices are still far from the efficiency threshold needed for industrial deployment, with surface recombination as the main limiting factor for the material. In this work, we discuss the main passivation techniques developed for germanium photovoltaic and thermophotovoltaic devices, summarizing their main advantages and disadvantages. The analysis reveals that surface recombination velocities as low as 2.7 cm/s and 1.3 cm/s have already been reported for p-type and n-type germanium, respectively, although improving surface recombination velocities below 100 cm/s would result in marginal efficiency gains. Therefore, the main challenge for the material is not reducing this parameter further but developing robust and reliable processes for integrating the current techniques into functional devices. Full article

This study focuses on electrical stimulation for composting. Using the PSALSAR method, a comprehensive systematic review analysis identified 22 relevant articles. The examined studies fall into four main systems: electric field-assisted aerobic composting (EAAC), electrolytic oxygen aerobic composting (EOAC), microbial fuel cells (MFCs), and thermoelectric generators (TEGs). Apart from the main systems highlighted above, bioelectrochemically assisted anaerobic composting (AnC_{BE, III}) is discussed as an underexplored system with the potential to improve the efficiency of anaerobic degradation. Each system is described in terms of key materials, composter design, operating conditions, temperature evolution, compost maturity, microbial community, and environmental outcomes. EAAC and EOAC systems accelerate organic matter decomposition by improving oxygen distribution and microbial activity, whereas MFC and TEG systems have dual functioning due to the energy generated alongside waste degradation. These innovative systems not only significantly improve composting efficiency by speeding up organic matter breakdown and increasing oxygen supply but also support sustainable waste management by reducing greenhouse gas emissions and generating bioelectricity or heat. Together, these systems overcome the drawbacks of conventional composting systems and promote future environmental sustainability solutions. Full article

Cryosurgery employs extremely low temperatures to destroy abnormal or cancerous tissue. Conventional systems use cryogenic fluids like liquid nitrogen or argon, which pose challenges in handling, cost, and precise temperature control. This study explores thermoelectric (TE) cooling using the Peltier effect as an efficient alternative. A numerical optimization of multi-stage TE coolers using bismuth telluride (Bi₂Te₃) is performed through finite element analysis in COMSOL Multiphysics. Results show that the optimized multi-stage TE system achieves a minimum temperature of −70 °C, a 90 K temperature difference, and 4.0 W cooling power—outperforming single-stage (SS) systems with a maximum ΔT of 73.27 K. The study also investigates the effects of material properties, current density, and geometry on performance. An optimized multi-stage (MS) configuration improves cooling efficiency by 22.8%, demonstrating the potential of TE devices as compact, energy-efficient, and precise solutions for cryosurgical applications. Future work will explore advanced nanomaterials and hybrid systems to further improve performance in biomedical cooling. Full article

Na₀.₈₉Co_0.90Me_0.10O₂ (Me = Cr, Ni, Mo, W, Pb, and Bi) ceramic samples were prepared using a solid-state reaction method, and their crystal structure, microstructure, and electrical, thermal, and thermoelectric properties were investigated. The effect of the nature of the doping metal (Me = Cr, Ni, Mo, W, and Bi) on the structure and properties of layered sodium cobaltite Na_0.89CoO₂ was analyzed. The largest Seebeck coefficient (616 μV/K at 1073 K) and figure-of-merit (1.74 at 1073 K) values among the samples studied were demonstrated by the Na_0.89Co_0.9Bi_0.1O₂ solid solution, which was also characterized by the lowest value of the dimensionless relative self-compatibility factor of about 8% within the 673–873 K temperature range. The obtained results demonstrate that doping of layered sodium cobaltite by transition and heavy metal oxides improves its microstructure and thermoelectric properties, which shows the prospectiveness of the used doping strategy for the development of new thermoelectric oxides with enhanced thermoelectric characteristics. It was also shown that samples with a higher sodium content (Na:Co = 0.89:1) possessed higher chemical and thermal stability than those with a lower sodium content (Na:Co = 0.55:1), which makes them more suitable for practical applications. Full article

In this study, the effects of different heat sink designs on the cold side of the modules in a thermoelectric generator (TEG) system placed between the compressor and the intercooler of a turbocharged tractor on the system performance were numerically analyzed. In the current literature, heat sinks used in TEG modules generally consist of plate fins. In this study, by using perforated and slotted fins, the thermal boundary layer behaviors were changed and there was an attempt to increase the heat transfer from the cold surface compared to plate fins. Thus, the performance of the TEG system was also increased. When looking at the literature, it is seen that there are studies which aim to increase the performance of TEG modules by changing the dimensions of p and n type semiconductors. However, there is no study aiming to increase the performance of TEG modules by making changes on the plate fins of the heat sinks used in these modules and thus increasing the heat transfer amount. In this respect, this study offers important results for the literature. According to the numerical analysis results, the total TEG output power, output voltage, and thermal efficiency obtained for S0.5H15 were 6.2%, about 3%, and about 5% higher than those for PF, respectively. In addition, the pressure drop values obtained for different heat sinks, except for aluminum foam, were approximately close to each other. In cases with TEG systems where different heat sinks were used, the intercooler inlet air temperatures decreased by approximately 3.4–3.5% compared to the case without the TEG system. This indicates that the use of TEG will positively affect the improvement in engine efficiency. Full article

This study synthesized Al₂CoCrFeNi high-entropy alloy (HEA) using spark plasma sintering (SPS) followed by annealing treatment. The effects of heat treatment on the microstructure, mechanical properties, wear resistance, and thermoelectric properties were systematically investigated. The annealed alloy exhibited a microhardness increase from 538.5 HV to 550.9 HV and a significant improvement in ultimate compressive strength from 1540.74 MPa to 2563.67 MPa, attributed to grain homogenization and reduced dislocation density. Wear resistance tests revealed a decrease in wear rate from 7.15 × 10⁻⁵ mm³/(N·m) to 4.74 × 10⁻⁵ mm³/(N·m), with wear morphology analysis confirming enhanced resistance to plastic deformation. Thermoelectric characterization demonstrated that thermal diffusivity increased from 2.98 mm²/s to 3.11 mm²/s at room temperature, while the absolute Seebeck coefficient reached 8.0 μV/K at 200 °C, indicating improved electron transport efficiency due to lattice ordering. This combination of high hardness, high thermal conductivity, and excellent wear resistance presents unique application value in extreme tribological fields involving thermal management and simultaneous surface wear resistance and heat dissipation. Full article

Thermoelectric generator (TEG) has emerged as a critical technology for automotive exhaust energy recovery, yet there is still a lack of reviews analyzing automotive TEG structure design and optimization methods simultaneously. Therefore, this review consolidates structure design and methods for improving thermoelectric conversion efficiency, focusing on three core components: thermoelectric module (TEM), heat exchanger (HEX), and heat sink (HSK). For TEM, research and development efforts have primarily centered on material innovation and structural optimization, with segmented, non-segmented, and multi-stage configurations emerging as the three primary structural types. HEX development spans external geometries, including plate, polygonal, and annular designs, and internal enhancements such as fin, heat pipe, metal foam, and baffle to augment heat transfer. HSK leverages active, passive, or hybrid cooling systems, with water-cooling designs prevalent in automotive TEG for cold-side thermal management. Optimization methods encompass theoretical analysis, numerical simulation, experimental testing, and hybrid methods, with strategies devised to balance computational efficiency and accuracy based on system complexity and resource availability. This review provides a systematic framework to guide the design and optimization of automotive TEG. Full article

The global scarcity of freshwater, particularly in arid regions, has intensified interest in sustainable desalination technologies. Among these, solar still (SS) systems stand out for their low operational costs and environmental compatibility. This review presents a comprehensive analysis of recent advancements in solar still technologies, with a particular emphasis on innovative materials, thermal management strategies, and hybrid systems aimed at improving water productivity and cost-efficiency. Key technologies such as phase change materials (PCMs) and thermoelectric modules (TEMs) are examined in detail, showing up to 140% and 6.7-fold improvements in productivity, respectively, in select configurations. The review also synthesizes results from various studies using a comparative lens, highlighting combinations such as double-glazed glass with fins and TEMs (5.7-fold increase) and CuO–water nanofluids coupled with TEMs and vibration (5.3-fold increase). Cost analyses reveal that some configurations achieve water production at as low as 0.011 USD/L under real-world conditions in Rajshahi, Bangladesh, using an integrated system with an external condenser and solar collector. Unlike general reviews, this work systematically compares performance metrics, cost-effectiveness, and design innovations across multiple studies to provide a clearer perspective on technology viability. Future directions suggest the integration of hybrid approaches using PCM, TEM, nanotechnology, and advanced geometries to overcome current limitations and further advance solar desalination efficiency. Full article

Thermoelectric module (TEM)-based coolers are gaining traction as compact, portable refrigeration solutions for storing medicine, beverages, and food. However, their adoption has been limited by relatively low cooling power and efficiency. This study demonstrates the importance of heat transfer in enhancing the coefficient of performance (COP) of TEMs through optimizing their boundary conditions. Among the three boundary conditions evaluated, the most effective involved integrating heat pipes (HPs) with a cooling fan on both sides of the TEM. This configuration significantly improved thermal management, enabling the system to achieve a COP of 0.53, with a cooling rate of 26.26 W and a cold-side temperature of 278.5 K. The enhanced heat extraction from the hot side, reaching 61.94 W, reduced the hot-side temperature to 305.6 K and decreased the overall thermal resistance, confirming the critical role of active heat dissipation. Moreover, placing a cooling fan on the HPs is crucial for facilitating efficient heat transfer from the hot side with a lower thermal resistance, as confirmed via thermal resistance analysis. Furthermore, a prototype refrigerator based on the TEM with HPs was built and tested indoors and outdoors with a COP of 0.45, a cooling rate of 21.97 W, and a cold-side temperature of 271.0 K. This study shows that the COP of TEMs can be increased by applying HPs to reduce the total thermal resistance of the TEM sides. Further optimization of TEM-based refrigerators holds promise for improving their performance in sustainable, small-scale cooling applications. Full article

We incorporated a Peltier cooling system into vests for personal comfort and applications in various workplaces. We tested the Peltier cooling vest using temperature sensors and evaluated the vest’s performance. The developed Peltier cooling vest included thermoelectric cooler modules to improve cooling efficiency and comfort by using water’s heat transfer and thermal conductivity. Through testing and subjective assessments, the effectiveness of the wearable cooling system and its potential for widespread adoption were validated. Furthermore, an intelligent control algorithm was developed to maintain target temperatures. The built-in temperature sensor enabled temperature stability in the set temperature range. The average cooling response time of the Peltier cooling vest was 9.42 min. In a lower temperature range of 16 to 24 °C, the vest maintained a stable temperature. A correlation between temperature and power consumption was observed. To improve the performance, built-in Bluetooth and a graphic user interface need to be integrated. Then, the Peltier cooling vest and its technology can be used in medical and industrial settings. Full article

Thermoelectric materials are functional materials that directly convert thermal energy into electrical energy or vice versa, and due to their inherent properties, they hold significant potential in the field of energy conversion. In this review, we examine several fundamental strategies aimed at enhancing the conversion efficiency, classification, preparation methods, and applications of thermoelectric materials. First, we introduce an important parameter for evaluating the performance of thermoelectric materials, the dimensionless quality factor ZT, and present the theory of electroacoustic transport in thermoelectric materials, which provides the foundation for enhancing the performance of thermoelectric materials. Second, strategies for optimizing electroacoustic transport properties, carrier concentration, energy band engineering, phonon engineering, and entropy engineering are summarized, emphasizing that energy band engineering presents numerous possibilities for enhancing thermoelectric material performance by tuning the carrier effective mass, energy band convergence, and energy band resonance. By analyzing the importance of various optimization strategies, it is concluded that co-optimization is the primary method for improving the performance of thermoelectric materials in the future. In addition, an overview of the currently available thermoelectric materials is provided, including two categories, classical thermoelectric materials and novel thermoelectric materials, along with a highlight of two thermoelectric material preparation techniques. Finally, the principles of thermoelectric technology are illustrated, its applications in various fields are discussed, problems in the current research are analyzed, and future trends are outlined. Overall, this paper provides a comprehensive summary of optimization strategies, material classifications, and applications, offering valuable references and insights for the researchers in this field, with the aim of further advancing the development of thermoelectric material science. Full article

The carbon footprint associated with human activity, particularly from energy-intensive industries such as iron and steel, aluminium, cement, oil and gas, and petrochemicals, contributes significantly to global warming. These industries face unique challenges in achieving Industry 4.0 goals due to the widespread adoption of industrial Internet of Things (IIoT) technologies, which require reliable and efficient power solutions. Conventional wireless devices powered by lithium batteries have limitations, including a reduced lifespan in high-temperature environments, incompatibility with explosive atmospheres, and high maintenance costs. This paper proposes a novel approach to address these challenges by leveraging residual heat to power IIoT devices, eliminating the need for batteries and enabling autonomous operation. Based on the Seebeck effect, thermoelectric energy harvesters transduce waste heat from industrial surfaces, such as pipes or chimneys, into sufficient electrical energy to power IoT nodes for applications like the condition monitoring and predictive maintenance of rotating machinery. The methodology presented standardises the modelling and simulation of Waste Heat Recovery Systems (IoT-WHRSs), demonstrating their feasibility through statistical analysis of IoT-WHRS architectures. Furthermore, this technology has been successfully implemented in a petroleum refinery, where it benefits from the NB-IoT standard for long-range, robust, and secure communications, ensuring reliable data transmission in harsh industrial environments. The results highlight the potential of this solution to reduce costs, improve safety, and enhance efficiency in demanding industrial applications, making it a valuable tool for the energy transition. Full article

Energy harvesting in the automotive sector is a rapidly growing field aimed at improving vehicle efficiency and sustainability by recovering wasted energy. Various technologies have been developed to convert mechanical, thermal, and environmental energy into electrical power, reducing dependency on traditional energy sources. This manuscript provides a comprehensive review of energy harvesting applications/methodologies, aiming to trace the research lines and future developments. This work identifies the main categories of harvesting solutions, namely mechanical, thermal, and hybrid/environmental solar–wind systems; each section includes a detailed review of the technical and scientific state of the art and a comparative analysis with detailed tables, allowing the state of the art to be mapped for identification of the strengths of each solution, as well as the challenges and future developments needed to enhance the technological level. These improvements focus on energy conversion efficiency, material innovation, vehicle integration, energy savings, and environmental sustainability. The mechanical harvesting section focuses on energy recovery from vehicle vibrations, with emphasis on regenerative suspensions and piezoelectric-based solutions. Specifically, solutions applied to suspensions with electric generators can achieve power outputs of around 1 kW, while piezoelectric-based suspension systems can generate up to tens of watts. The thermal harvesting section, instead, explores methods for converting waste heat from an internal combustion engine (ICE) into electrical power, including thermoelectric generators (TEGs) and organic Rankine cycle systems (ORC). Notably, ICEs with TEGs can recover above 1 kW of power, while ICE-based ORC systems can generate tens of watts. On the other hand, TEGs integrated into braking systems can harvest a few watts of power. Then, hybrid solutions are discussed, focusing on integrated mechanical and thermal energy recovery systems, as well as solar and wind energy harvesting. Hybrid solutions can achieve power outputs above 1 kW, with the main contribution from TEGs (≈1 kW), compared to piezoelectric systems (hundreds of W). Lastly, a section on commercial solutions highlights how current scientific research meets the automotive sector’s needs, providing significant insights for future development. For these reasons, the research results aim to be guidelines for a better understanding of where future studies should focus to improve the technological level and efficiency of energy harvesting solutions in the automotive sector. Full article

This study investigates the size effect on the Seebeck coefficient (SC) in cement composites incorporating silicon carbide (SiC). Two specimen shapes, cubic (50 × 50 × 50 mm³) and beam (40 × 40 × 160 mm³), were analyzed with varying SiC substitution ratios (0%, 50%, and 100%) for fine aggregates. Thermal and electrical conductivities were measured to assess their influence on the SC. The results showed that a higher SiC content increased porosity, which reduced mechanical strength but significantly improved thermal and electrical conductivities. Thermal conductivity increased from 1.88 W/mK (0% substitution) to 11.89 W/mK (100% substitution), while electrical conductivity showed an improvement from 0.0056 S/m to 0.065 S/m. Cubic specimens exhibited higher SC values compared to beam specimens, with a maximum SC of 1374 μV/K at 100% SiC substitution, attributed to shorter thermal diffusion distances. The findings suggest that optimizing member size and SiC content can significantly improve the thermoelectric performance of cement composites, potentially enhancing energy efficiency in construction applications. Full article

This study proposes a vertically stacked thermoelectric generator (TEG) design to enhance output power per unit volume. While the proposed TEG achieved improved conversion efficiency, the high inertia of the exhaust gas leads to significant flow maldistribution across the channels, causing uneven thermal conditions on the TEM surfaces and reducing overall efficiency. To enhance waste heat recovery by improving flow uniformity in the exhaust gas channels, a perforated plate with porosity ranging from 0.15 to 0.75 was inserted. A multi-physics numerical model was developed to simulate the thermoelectric energy conversion phenomena, enabling for the accurate evaluation of both module- and system-wise performance. The insertion of the perforated plate with 0.45 porosity provided the most uniform flow distribution with only a 5% flow rate difference between the exhaust gas channels. This resulted in a system-level output power of 167.1 W, which is ~7% higher than the case without the perforated plate, along with electrical efficiency of 91.1% and conversion efficiency of 3.41%. Moreover, enhanced flow uniformity led to an improved volumetric power density of 20.8 kW/m³. When accounting for pumping losses, the perforated plate with 0.6 porosity maximized net output power, demonstrating how optimized flow distribution significantly enhances energy harvesting performance. Full article