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In this study, green hydrogen production by utilizing diesel engine exhaust gas waste heat in steam and organic Rankine with internal heat exchanger with two thermoelectric generators and proton exchange membrane electrolyzer combined system under different load conditions is investigated. Thermo-economic, enviro-economic and exergo-environmental analyses of the maximum hydrogen production point determined for different waste heat conditions are carried out. Total and specific investment cost and levelized cost of hydrogen determined under different loads are compared. Simple and dynamic payback period, profit ratio of investment and net present value of the combined system at different selling prices of hydrogen are determined and their feasibility is analyzed. Carbon reduction and carbon credit gain amount due to green hydrogen produced in line with zero emission targets are compared under different waste heat conditions. Exergetic sustainability index of the system were determined within the scope of exergo-environmental analysis. In terms of economic and environmental performance, a hydrogen cost of 2.04 $/kg was obtained under 100% load and a carbon saving of 7211 $ was achieved depending on the hydrogen produced. Dynamic payback period and net present value were found to be 4.467 years and 404,696 $, respectively, if the hydrogen selling price was 5 $/kg under 100% load. It is found that a 50% load reduction leads to an increase in dynamic payback period and levelized cost of hydrogen by 18.6% and 13.72%, respectively, and a decrease in net present value and profit ratio of investment by 54.39% and 12.39%, respectively. On the other hand, since the exergy destruction decreases with the decrease in the load, exergo-environmental index is found to decrease by 2.03%. • 7211 $ carbon recovery was obtained. • Dynamic payback period between 1.942 and 9.578 years was determined. • The maximum net present value reached 1,123,000 $. • Combined hydrogen production system is unfeasible if the hydrogen price is 2 $/kg. • Within the scope of sustainability, exergo-environmental indices were examined. [ABSTRACT FROM AUTHOR]

Today, energy harvesting has developed into a technique from which various aspects are still hidden. By extracting energies from the environment and even the human body, and converting them into electrical energy, we can supply power to low‐consumption electronic devices. Energy harvesting works by inhibiting small amounts of ambient energies; otherwise, it is wasted in other forms such as heat, vibration, and light. In this paper, we aim to eliminate or minimize the dependence of portable electronic devices to the batteries, which have limited life times, service costs, handling, and environmental problems. This is accomplished via incorporating the hybrid energy‐harvesting techniques and designed to power (bio)medical devices in order to measure vital signs. In this circuit, by simultaneously harvesting RF, light, thermal, and solar (natural and artificial) energies, we were able to increase the reliability of continuous supply of electrical energy in energy‐harvesting systems by generating and storing maximum power from the environment. Supercapacitors are used as the energy storage elements so that there is no energy waste, and each system is constantly storing the electrical energy with the aid of a diode block. In addition, with the help of supercapacitors, this device is able to transmit a maximum of 420 mW to the load and the total efficiency is equal to 74%. [ABSTRACT FROM AUTHOR]

For a photovoltaic module coupled with thermoelectric generator, a unique wavy cooling channel is proposed, and its performance is numerically assessed by using three-dimensional computations. The cooling channel uses nanofluid of alumina–water with various shaped nanoparticles (spherical, cylindrical and brick). Numerical simulations are performed for a range of parameters for the corrugation amplitude ( 0 ≤ Amp ≤ 0.1 ), wave frequency ( 2 ≤ Nf ≤ 16 ), nanoparticle loading quantity ( 0 ≤ SVF ≤ 0.03 ), and nanoparticle shape (spherical, brick, and cylindrical). We analyze the photovoltaic module's average temperature and temperature uniformity for a variety of parameter variations. When nanofluid and greater channel corrugation amplitudes are utilized, the average panel surface temperature is decreased more. A wavy shape of the cooling channel at the maximum corrugation amplitude yields a cell temperature reduction of 1.88 o C, while frequency has little impact on average cell temperature and its uniformity. The best-performing particles are those with cylindrical shapes, and the drop-in average photovoltaic temperature with solid volume fraction is essentially linear. As utilizing cylindrical-shaped particles, the average temperature of corrugated cooling channels decreases by around 1.9 o C as compared to flat cooling channels with base fluid at the greatest solid volume fraction. As compared to un-cooled photovoltaic, cell temperature drops by around 43.2 o C when employing thermoelectric generator. However, temperature drop value of 59.8 o C can be obtained by using thermoelectric generator and nano-enhanced wavy cooling channel utilizing cylindrical-shaped nanoparticles. An hybrid computational strategy for the fully coupled system of photovoltaic with cooling system is provided, which reduces the computational time by a factor of 75. [ABSTRACT FROM AUTHOR]

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 TiO 2 , Fe 3 O 4 , Al 2 O 3 , 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 CO 2 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. • Graphene nanofluid yields 221.77 mW power and 8.99 % exergy efficiency at 2 m/s. • At 595 kWm−2, graphene saves highest CO 2 of 0.38 kgyr−1. • Optimal von Mises stress of 1.35 GPa at 0.2 mm leg height • Minimized cost of electric power is 3.79×10−6 $mW−1. • Non-uniform TEGs assessed for sustainable, efficient energy practices. [ABSTRACT FROM AUTHOR]

Silver selenide (Ag2Se) flexible films are promising near‐room‐temperature thermoelectric candidates for low‐grade heat harvesting. However, existing Ag2Se films are generally attached on substrates, which impedes further flexibility improvement of the films and constrains the scenarios of applications. Here a cost‐effective and scalable strategy is presented, which combines screen printing and annealing, for synthesizing freestanding Ag2Se inorganic films with different densities of pores. High‐density pores and thin thickness endow the films with high flexibility, while films with low‐density pores obtain higher power factor. Furthermore, by utilizing the porous microstructure, a composite structure consisting of a Ag2Se conductive network and an organic polydimethylsiloxane (PDMS) skeleton is fabricated, which further improves films’ stability under bending and torsion. Finally, a flexible thermoelectric generator comprising five Ag2Se/PDMS legs and encapsulated PDMS outputs a voltage of 20.2 mV and a maximum power of 810 nW (the corresponding power density is 5.4 W m−2) at a temperature difference of 30 K, verifying potential application at near room temperature. This work offers a useful paradigm for fabricating substrate‐free Ag2Se porous films with high flexibility for near‐room‐temperature thermoelectric applications. [ABSTRACT FROM AUTHOR]

The issue of energy supply for wireless sensors is becoming increasingly severe with the advancement of the Fourth Industrial Revolution. Thus, this paper proposed a thermoelectric self−powered wireless sensor that can harvest industrial waste heat for self−powered operations. The results show that this self−powered wireless sensor can operate stably under the data transmission cycle of 39.38 s when the heat source temperature is 70 °C. Only 19.57% of electricity generated by a thermoelectric power generation system (TPGS) is available for use. Before this, the power consumption of this wireless sensor had been accurately measured, which is 326 mW in 0.08 s active mode and 5.45 μW in dormant mode. Then, the verified simulation model was established and used to investigate the generation performance of the TPGS under the Dirichlet, Neumann, and Robin boundary conditions. The minimum demand for a heat source is cleared for various data transmission cycles of wireless sensors. Low−temperature industrial waste heat is enough to drive the wireless sensor with a data transmission cycle of 30 s. Subsequently, the economic benefit of the thermoelectric self−powered system was also analyzed. The cost of one thermoelectric self−powered system is EUR 9.1, only 42% of the high−performance battery cost. Finally, the SEPIC converter model was established to conduct MPPT optimization for the TEG module and the output power can increase by up to approximately 47%. This thermoelectric self−powered wireless sensor can accelerate the process of achieving energy independence for wireless sensors and promote the Fourth Industrial Revolution. [ABSTRACT FROM AUTHOR]

A thermoelectric generator (TEG) module converts heat directly into electrical energy. Waste heat from a process is a viable heat source for TEG modules to support the energy sustainability agenda. A module was designed to recover low-temperature waste heat from a 1 kW fuel cell stack used in a mini hydrogen vehicle. The module was constructed using a single TEG cell that receives heat directly on its surface from the waste heat stream, coupled with a heat pipe connected to a finned heat sink to effectively cool the cold junction of the TEG cell. This research presents a comparison of the module characteristics when it is operated under direct impinging jet flow and swirl flow waste heat streams at 60°C, while the cold junction of the cell is cooled under stationary vehicle conditions (natural convection cooling) and cruising conditions (forced convection cooling) at an air speed of 5 m/s. Results indicate that the swirling effect increases the maximum power point (MPP) by 60%. The introduction of swirl to the heating stream is a viable approach to significantly enhance the recovery of low-grade waste heat using TEG. However, the MPP shows a greater increase of 70 to 80% due to the forced cooling effect, indicating that cold junction cooling has a more significant influence on the MPP compared to the swirl effect. [ABSTRACT FROM AUTHOR]

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.

This study optimizes the main parameters of the cold‐side heat exchanger (CHE) longitudinal fin, including fin quantity (Nf), fin thickness (Tf), and fin height (Hf), to enhance the performance of motorcycle exhaust thermoelectric generator units (TGUs) utilizing the computational fluid dynamics approach. The investigation shows that these parameters significantly affect the dissipation area of the CHE heat and the outside air velocity distribution in fin gaps, resulting in the fluctuation of TGU output power. The output power increases with respect to Hf; nevertheless, it first increases as Nf and Tf increase but decreases dramatically when Nf or Tf becomes too large. Besides, Hf significantly affects output power, and its impact is almost independent of Tf and Nf, and vice versa; meanwhile, Tf and Nf have a strong relation. This study proposes two Hf of 40 and 60 mm along with the optimal Tf of 1 mm and Nf of 29, providing significantly high output power, low weight, and compact size for TGU. This work contributes insight into the effect of CHE parameters on the TGU performance, and it is a crucial case study for selecting suitable heat sink parameters for TGU, considering practical requirements and conditions. [ABSTRACT FROM AUTHOR]

Thermoelectric generators (TEGs) harness temperature differences to produce electricity and hold promise for diverse industrial applications. However, their limited conversion efficiency casts doubt on their role in achieving energy independence. This study introduces an advanced technique that exploits temperature gradients in water pipes, utilizing supplementary TEGs to augment power generation. This method maintains a stable temperature gradient for TEG operation. Additionally, TEG power output can be efficiently modulated via flow control. In the feasibility evaluation for residential settings, the temperature fluctuations across each system unit were analyzed. In the active system, the chosen sites for TEG integration were units equipped to manage heat transfer using working fluids. The inlet and outlet temperatures were calculated for photovoltaic-thermal (PVT) systems, ground heat exchangers (GHEs), and heat storage tanks (HSTs). The electricity produced by the TEGs was benchmarked against their conversion efficiency, zT. The results indicated that the TEGs yielded 10.95 kWh of electricity when systematically implemented in each unit. To realize a zero-energy building, an area of 64.5 m2 per unit is necessitated for TEG deployment, given a zT value of 1.

Screen printing technology is employed to prepare poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/double‐walled carbon nanotubes (DWCNT) films as active p‐type material for flexible thermoelectric generators (TEGs). Performance of the PEDOT:PSS/CNT composites have been optimized by changing the formulation inks to make them suitable for screen printing, by varying the CNT concentrations and by treating the printed polymeric films in ethylene glycol (EG). The purpose of this work is finding the processing conditions that optimize conductivity, Seebeck coefficient, and the power factor of the fully printed material. From experimental data, the composite with 10% by weight of DWCNT chemically treated in EG maximizes conductivity, Seebeck coefficient, and power factor of the material. [ABSTRACT FROM AUTHOR]

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In internal combustion engines, approximately 40% of the thermal power obtained from fuel burning is thrown out to the environment from the exhaust system. Implementations of waste heat recovery systems with thermoelectrical generator over exhaust system have become widespread as it is the waste heat resource with the highest temperature in a vehicle. During literature research, experiments related to waste heat recovery under real road conditions are very few and no study on estimation of system performance by machine learning algorithms has been found; therefore, Toyota Corolla has designed an air-cooled waste heat recovery system using 3 thermoelectrical generators for the exhaust system of the automobile. During the road tests, temperature and electric power generation values obtained as per gear, vehicle speed and engine speed have been recorded. In the study, a dataset consisting of 10 attributes was created with each record as a result of the path test. Using this dataset, Random Forest, Support Vector Machine (SVM) and Naive Bayes machine learning algorithms estimated the electrical power to be generated from the thermoelectric generator recovery system. In the study, 7 electric power classification estimates were made. In the estimation process, 76% of the dataset was used for training and 24% was used for testing. In terms of estimation success; an estimation success of 96.6% has been achieved by Random Forest method; 94.6% by Support Vector Machine (SVM) method; and 76.7% by Naive Bayes method. The results show that prospective electricity generation estimation can be achieved with high level of accuracy. [ABSTRACT FROM AUTHOR]

A promising solution for challenges in thermal energy storage (TES) and its management is the use of phase change materials (PCMs). The ionic liquids (ILs) offer a unique properties that make them proper candidates for a number of energy related applications. The IL based PCMs are an important category of novel materials that significantly contribute to the efficient use and conservation of solar energy and wasted heat. This work presents a new family of ionic liquids (ILs) 2-hydroxyethylammonium, bis (2-hydroxyethyl) ammonium, and tris (2-hydroxyethyl) ammonium laurate as PCMs for the first time operating in the temperature range of 50–150 °C, and offer a safe and inexpensive capacity. The latent heat of fusion values were 147.13, 131.95 and 113.54 kJ·kg−1 for the [HEA]Lau, [DHEA]Lau and [THEA]Lau, respectively. Also, the thermal stability was obtained to be 99% for the [HEA]Lau. Finally, the thermal-to-electric energy conversion is performed using a homemade electronic data gathering and processing instrument with a PCMs (synthesized ILs) container cell and a commercial thermoelectric generator (TEG) device to record the real-time generated electric energy. The recorded output voltage (open circuit case) of TEG device versus time was measured that demonstrated that after turning off the thermal energy source, the proposed system provides the electric energy for a while (more than 2 h). [ABSTRACT FROM AUTHOR]

A waste heat recovery system with thermoelectric generation was constructed to convert waste heat into electrical energy for powering light emitting diodes (LED) car lamps and enhancing the efficient utilization of low-grade energy. The response characteristics of the waste heat recovery system during different stages of energy conversion and LED car lamp operation were examined with the constant temperature heating furnace to replicate the heat source. The variations in light output characteristics of LED car lamps independently driven by energy storage components were investigated in practical scenarios. The results show that the energy storage component can efficiently store and recover electric energy from waste heat, operate an LED car lamp independently and mitigate voltage fluctuations resulting from temperature changes. The energy density of lithium batteries is high with storing substantial electric energy. The fast cold start speeds can be realized with extended lighting duration when the LED car lamps are drived independently, but the charging time is longer. The cold start speeds of supercapacitors are sluggish with rapid charging and discharging rates, which is helpful to alleviate the driving voltage fluctuation of LED car lamp when the waste heat recovery system is activated briefly. [ABSTRACT FROM AUTHOR]

Wearable thermoelectric generators have great potential to provide power for smart electronic wearable devices and miniature sensors by harnessing the temperature difference between the human body and the environment. However, the Thomson effect, the Joule effect, and heat conduction can cause a decrease in the temperature difference across the thermoelectric generator during operation. In this paper, phase change materials (PCMs) were employed as the heat sink for the thermoelectric generator, and the COMSOL software 6.1 was utilized to simulate and optimize the power generation processes within the heat sink. The results indicated that with a PCM height of 40 mm, phase transition temperature of 293 K, latent heat of 200 kJ/kg, phase transition temperature interval of 5 K, thermal conductivity of 50 W/(m·K), isobaric heat capacity of 2000 J/(Kg·K), density of 1000 kg/m3, and convective heat transfer coefficient of 10 W/(m·K), the device can maintain a temperature difference of 18–10 K for 1930 s when the thermoelectric leg height is 1.6 mm, and 3760 s when the thermoelectric leg height is 2.7 mm. These results demonstrate the correlation between the device's output performance and the dimensions and performance parameters of the PCM heat sink, thereby validating the feasibility of employing the PCM heat sink and the necessity for systematic investigations. [ABSTRACT FROM AUTHOR]

Currently, a significant number of automobiles are equipped with internal combustion engines. In urban areas, a significant number of transportation methods have detrimental environmental effects through the release of pollutants resulting from the combustion of fossil fuels. In addition to the emission of toxic pollutants, internal combustion engines experience significant energy losses through exhaust emissions. Advanced technological applications have the potential to recover of a portion of the waste heat from exhaust ducts. Evaluations conducted by scholars across several disciplines highlight diverse perspectives on the recycling of thermal energy from exhaust gases as a means of mitigating pollution sources. However, this review focuses on the utilization of thermoelectric generators for harvesting a fraction of the aforementioned dissipated energy. The energy harvesting system is comprised of three components: the heat exchanger, which serves as the heat source; the cooler, which functions as the heat sink; and the thermoelectric generators, which act as the heat engine sandwiched between the heat exchanger and the cooler. This review examines the diverse exterior designs of heat exchangers and coolers and categorizes them accordingly. Additionally, it identifies the optimal installation locations for harvesting systems and explores the impact of design variations, choice of metals for manufacturing, and internal topography on the generation of electrical power. The primary findings of this review emphasize the significance of prioritizing the design of heat exchangers over coolers. This is because the uniformity of the temperature distribution within the heat exchanger plays a crucial role in governing the overall performance. Moreover, the installation of the system on petrol engines was seen as more cost-effective in comparison to its installation on diesel engines, primarily due to the higher magnitude of energy emitted from the exhaust gases of the former as opposed to the latter. To the best of the author's knowledge, this review classification has never been performed before. This can be considered a brief path map and a starting point for future work by researchers and investigators in designing heat exchangers and coolers and choosing the locations of TEG system installations. Then profitable investment from the data that has been prepared and summarized. [ABSTRACT FROM AUTHOR]

AbstractDespite the recognized fact that power transformers (PT) are highly efficient technology, part of their electrical energy is counted as heat losses. Therefore, the cooling system is a critical factor in the life span and performance of the PTs, and hence the adopted thermal energy design can be strongly effective. This study revolves around the innovative development of a novel generation of fixed ventilation fans for PTs, achieved through Computational Fluid Dynamics (CFD) simulations and practical experiments. The proposed CFD model was developed adopting ANSYS FLUENT 19.2. The proposed CFD model was verified by comparing the numerical and experimental results of the cooling air temperature and velocity. A standard k-ε model was used to simulate the airflow of the investigated cooling system numerically. A thermal analysis of a four-sided power transformer was performed, and an analysis of the optimum position to install the cooling fan on the radiator was presented. The most effective number of used fans was also determined. The main results showed that two fans were found to be the best performance among the tested candidate alternatives. The two cooling fans’ size, material, and cover shape were also studied and added to the proposed model. Besides, the utilization of a thermoelectric generator was considered in this study in order to recycle some of the lost heat into output power. An experimental prototype mimicking the actual cooling system for the power transformer was designed and fabricated. Results showed that the selected material has achieved a high Calculated Factor of Safety (FoS) equal to 237, indicating that the utilization of the designed parts is of high safety. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The International Maritime Organization has set targets for reducing greenhouse gas emissions from ships. Thus, it is imperative to investigate novel technologies that have the potential to achieve these targets and reduce emissions in the short and long term. Waste heat recovery (WHR) technology, which generates electricity from engine waste energy, is a promising solution. This research examines the integration of a thermoelectric generator and organic Rankine cycle as a combined WHR system onboard a passenger ship. The purpose of the paper is to analyze the TEG–ORC system parametrically and from a techno-economic perspective. The results showed that the optimum design scenario is achieved by integrating the recuperative ORC system (rcORC) with the TEG system, this integration produces 1569 kW as net output power (19% more than the original TEG–ORC system) at an evaporation pressure of 55 bar. The exergy efficiency of the system is enhanced from 43.2 to 48.6% by the addition of the recuperator. Also, the efficiency of the power system (engine + TEG–rcORC system) is 53.2% (+ 6.1% over the efficiency of the standalone engine). The integration of the TEG–rcORC system with the main engine provides the ship with an energy efficiency existing index (EEXI) of 22.47 g-CO2 ton−1 nm−1, this value is lower than the required EEXI by 11%. From an economical point of view, the levelized power cost of the TEG–rcORC system is 280.2 € kW−1, and the annual saving in expenses is 1.05 M€ with a discounted payback time of 3.9 years. [ABSTRACT FROM AUTHOR]

Biomass combustors provide space heating by converting chemical energy in woody biomass into low-temperature thermal energy. Thermoelectric generators (TEGs) can generate electricity from the heat flux without significantly reducing heating performance. However, most current TEGs are small (40 mm × 40 mm), requiring many TEG elements to generate useful power from a biomass combustion-based space heater. This work compares the electrical generation potential of an array of small TEGs with a larger (80 mm × 120 mm) TEG in a vertical configuration representative of a residential heating appliance. An experimental facility was developed for various representative cold-side ducts and controllable hot-side temperature and cooling airflows, and the Taguchi method was used to evaluate the impacts of temperature, airspeed, and ducting configurations. The results indicate that temperature and airspeed significantly influence TEG power, while ducting configurations have an insignificant influence. The large TEG achieved more consistent temperatures but produced lower power than an array of smaller TEGs with the same total area. The study emphasizes optimizing TEG design and operating conditions to enhance electricity generation efficiency in space heating combustors. [ABSTRACT FROM AUTHOR]

[Display omitted] Outdoor radiative cooling is a passive method of cooling a surface that faces the sky. During the past decade, numbers of successful demonstrations of daytime radiative coolers have been reported. Because a daytime radiative cooler can be radiatively cooled both during the day and at night, it is always cooled and a temperature difference against the surroundings is generated. This temperature difference can be used to generate thermoelectric power throughout the day by placing a daytime radiative cooler on a thermoelectric module. However, such a device cannot harvest solar heat because sunlight is reflected by the daytime radiative cooler. In this study, a thermoelectric device that simultaneously harvests both radiative cooling and solar heating is presented. The essential component is a vertically placed thermoelectric module made of transparent thermoelectric thin films which allows radiatively cooled and solar heated surfaces to be co-planar. The outdoor and indoor measurements confirm that the device can harvest both radiative cooling and solar heating simultaneously during the day without offsetting each other, and can harvest radiative cooling at night. The co-planar design is an efficient method for simultaneously harvesting solar heating and radiative cooling, which could facilitate efficient energy harvesting and can be applied to a standalone power supply for off-grid sensor modules. [ABSTRACT FROM AUTHOR]

This study presents an optimized design for segmented variable area leg thermoelectric modules using finite element methods and Bayesian regularized neural networks. We explored the impact of geometry and thermal parameters on module performance using ANSYS software, identifying optimal parameters for power output and efficiency. Key findings revealed the higher influence of geometric parameters and confirmed the advantages of segmented thermoelectric generators for high-temperature applications like concentrated solar systems. With this optimization, power output and efficiency of the module increased by 875% and 165%, respectively, under 25 Suns. To refine the optimization process, a Bayesian regularized neural network was utilized, proving effective in predicting module performance with a low mean squared error and high coefficient of determination. This research provides important insights into high-performance thermoelectric modules for sustainable energy applications, demonstrating the significant role of advanced computational methods in energy solutions. [ABSTRACT FROM AUTHOR]

Maximizing the power delivered by a thermoelectric generator (TEG) (with an internal resistance RTE) can be achieved by optimizing its design taking into account the external load (with a resistance of RL). In the present work, the evolution of the thermoelectric (TE) properties of the materials along the leg was considered. By considering a fixed heat rate on the hot side, the powers delivered by various TEGs were assessed by varying the length of the legs. After that, analytical approach was detailed based on the mathematical formulas governing the thermal and electrical transports. This approach revealed that the ratio m = RL/RTE is between the most commonly claimed values (1 and (1 + zT)1/2). Our variable properties model reveals that the optimal design requires lower cost than that considered by equaling RTE and RL (m = 1). This finding turns out to be more and more valid for materials which present a linear variation of temperature with position. [ABSTRACT FROM AUTHOR]

People dissipate energy constantly, from their heartbeat to their footsteps. However, scientists are developing a technique for capturing power from human beings and converting it electricity that can power electronic medical devices or other devices that need low voltage. Energy harvesting and bioelectronics researchers are currently exploring this form of energy recycling. Mechanical, chemical, and thermal energy are the three primary forms of energy in the human body. This paper focuses on thermal energy sources only, showing that the energy harvested from a person's head can be used to power a headlamp. A total of seven thermoelectric generators (TEGs) were used, each comprising thirty-five thermocouples. An output voltage of 1.5 volts was obtained from the TEG systems. In addition, an electrical circuit was designed to convert the obtained TEG voltage into another voltage suitable for the headlamp model. [ABSTRACT FROM AUTHOR]

In current research, there are excessive assumptions and simplifications in the mathematical models developed for thermoelectric generators. In this study, a comprehensive mathematical model was developed based on a plate-type thermoelectric generator divided into multiple thermoelectric units. The model takes into account temperature-dependent thermoelectric material parameters and fluid flow. The model was validated, and a maximum error of 6.4% was determined. Moreover, the model was compared and analyzed with a numerical model, with a maximum discrepancy of 7.2%. The model revealed the factors and their degree of influence on the performance of the thermoelectric generator unit. In addition, differences in temperature distribution, output power, and conversion efficiency between multiple thermoelectric units were clearly studied. This study can guide modeling and some optimization measures to improve the overall performance of thermoelectric generators. [ABSTRACT FROM AUTHOR]

Harvesting environmental energy sources is crucial for achieving renewable energy generation and net-zero emissions. However, ensuring uninterrupted electricity generation from environmental energy sources remains challenging. In this study, we present a simple, compact, and expandable all-day vertical passive thermoelectric generator (V-TEG) with a double-sided reflective structure that simultaneously harnesses solar and space cold energy. Outdoor experimental measurements, combined with finite element simulation analysis, revealed that the optimal angles of the solar reflector relative to the TEG range from 30° to 50°. Additionally, the TEG placed in the north–south orientation was found to enhance its daytime performance. The use of low-cost black paint combined with the solar reflector achieved equivalent spectral selectivity, effectively minimizing the infrared heat loss of the hot end of the TEG. During a 48-h outdoor test, the V-TEG achieved an average daytime power of 112.00 mW/m2 and a peak of 363.42 mW/m2. Comparative experiments demonstrated that the V-TEG outperformed horizontally placed TEG during the daytime. Furthermore, scaling the system by connecting three TEGs in series significantly increased the daily power output. This compact V- TEG system offers a promising solution for long-term power generation in low-power sensors and off-grid communities, supporting renewable energy and carbon neutrality goals.

Thermoelectric generators (TEGs) integrated with solar energy and radiative cooling offer a promising approach for generating power. Concentrated solar energy enhances generation by increasing the solar flux density. However, the relationship between thermoelectric generation and concentration ratio remains not well understood. In this study, the finite element method is employed to investigate the temperature difference across TEGs and the change in generation performance with varying concentration ratios. The results show that due to the mismatch among cooling, heating, and parasitic heat conduction powers, the optimal power generation does not occur at the maximum concentration ratio. As the concentration ratio increases, the temperature difference across the single TEG and its output power initially increase and then decrease. To further improve the power generation performance at high concentration ratios, this study introduces TEG stacking strategy to enhance waste heat recovery by increasing thermal resistance. Outdoor experiments with self-made solar absorptive coating and radiative cooling coating validate this approach, achieving a temperature difference of 64.17 °C and a power density of 135.57 W m−2 by stacking three TEGs, outperforming a single TEG by over three times. This study offers a potential method to continuously power remote off-grid communities and low-power devices.

Photovoltaic-Thermoelectric Generator (PV-TEG) system has emerged as a promising approach to significantly enhance the efficiency of conventional PV cells. However, optimizing the performance of these hybrid systems presents a formidable challenge due to their complex structure and multitude of design parameters. This study tackles such challenge by developing a machine learning based Artificial Neural Network (ANN) model which comprises two sub-ANN models that can work independently for PV and TEG modules or in combination through a cyclic approach for the hybrid PV-TEG system. The model demonstrates remarkable versatility, allowing control over various parameters such as PV coating, device geometry, and environmental conditions. Compared to COMSOL simulations, the ANN model achieves over 97.6 % accuracy with a 6000-fold increase in simulation speed, enabling extensive parameter sweeps and insightful system analysis. Within 18 min, the model conducted a real-time simulation using 8712 weather data entries from Singapore in 2022 and predicted that the hybrid PV-TEG system would generate a total power of 265 kWh/m2, 6.4 % more than that of the standalone PV system with an average system temperature reduction of 7 K. The model's rapid processing capabilities and high accuracy are particularly beneficial for large-scale simulations and practical applications in renewable energy technology.

Efforts to enhance the performance of thermoelectric generators (TEGs) in engine waste heat recovery have primarily focused on directly increasing energy conversion efficiency. Heat leakage can occur in many parts of a TEG. It is needed to develop a model to help researchers study this phenomenon and propose measures to reduce heat leakage. To address this gap, this study establishes and validates a computational fluid dynamic (CFD) and finite element (FE) coupled model based on a TEG prototype and its engine test bench. Unlike other models, this approach captures the intricate dynamics of heat propagation from the TEG via air gaps, encompassing conduction, convection, and radiation. Comprehensive analysis reveals that heat leakage accounts for approximately 11% of TEG power output loss. Ignoring the impact of heat leakage can lead to an overestimation of TEG power output. Key areas of heat leakage are identified, and numerical factors influencing this phenomenon are explored. Vertical TEG placement and optimal spacing between thermoelectric modules emerge as effective strategies for mitigating the impact of heat leakage on power output. Leveraging these insights, strategic thermoelectric module placement, vertical TEG orientation, and the application of thermal insulation materials to the heat exchanger are proposed as measures to enhance TEG power output by approximately 5%. The experimental and numerical results underscore the feasibility of optimizing TEGs from the perspective of heat leakage, a crucial aspect previously overlooked. These findings provide valuable insights for future TEG optimization endeavors, highlighting the importance of addressing heat leakage to maximize TEG performance.

In this present investigation, the performance of thermoelectric generators (TEGs) was determined for the TEGs made of lead telluride (PbTe3), bismuth telluride (Bi2Te3), silicon germanium (SiGe), and aluminum oxide (Al2O3). In response to variations in the heat input rate and water flow rate, the electric power generated by the TEG was recorded and studied for the aforementioned TEG materials. During the investigation, the water flow rate to the TEG's cold side was chosen to be 0.5 lpm to 2 lpm in the step of 0.5 lpm, and the thermal energy input rate to the hot side was set at 30 W–120 W in the step of 30 W. Among all the TEGs Bi2Te3 was superior in terms of power generation potential in comparison to other TEGs in all the test conditions. The investigation also reveals that all TEGs appear to have a high-power generation when the cooling water flow rate was 2 lpm and the heat input rate was 120 W. At a water flow rate of 2 lpm for the case of Bi2Te3, the power generation potential was elevated by about 20.3 %, 14.4 %, and 6.5 % in comparison to Al2O3, PbTe3, and SiGe respectively.

Promoting the efficiency of internal-combustion engine has great benefits, including low fuel-consumption rate and environmental friendliness. Flue gas waste heat thermoelectric generator (TEG) is such a promising solution owning to its solid-state energy conversion and structural simplicity. In this work, a novel heat collection enhancing strategy is first proposed to improve the uniformity of hot-end temperature distribution, which greatly augments the power generation performance under limited pressure drops. A flue gas waste heat TEG unit with 24 TE modules is able to generate an electric power of 103 W under the pressure drop of 375 Pa. The corresponding heat collection, TE, and overall efficiencies of the TEG unit are 36.53 %, 4.30 %, and 1.58 %, respectively. Several important parameters, including flue gas inlet temperature, cooling intensity, cooling mode, and TEG unit arrangement are explored in detail. A demonstration application of an 8-unit waste heat TEG is installed in an 800-ton inland waterway vessel on China's Grand Canal, and the waterway vessel is put into service for over three months. The generated electric power varies between 23.3 W and 463 W, and the average electric power is 177.6 W during the trip.

This letter presents a touch‐driven self‐powered sensing system utilizing a high‐performance thermoelectric generator (TEG). The TEG, employing assembly technology with a high‐performance electrodeposited thermoelectric material, is fabricated. This device is accompanied by an investigation into the associated electronic circuits, facilitating a realistic demonstration. Upon tactile interaction with one side of the TEG, the system efficiently harvests energy, accumulating 15.36 mJ in a storage capacitor. Energy consumption, inclusive sensors and Bluetooth Low Energy (BLE) communication, is evaluated at 0.75 mJ/cycle, with a 2 s interval time. Notably, the sensing system demonstrates sustained operation as long as touch interactions persist, showcasing its potential for continuous, self‐powered functionality. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Objective. The article discusses energy-saving thermoelectric generators for autonomous power supply of the cooling apparatus of heat-generating electronic components.Method. Methods of modeling heat exchange processes in the operation of thermoelectric generators based on the Seebeck effect are applied. The heated and cooled zones of the generator are topologically spaced to reduce parasitic conductive transport. The semiconductor branches are manufactured using thin-film technology to reduce parasitic Joule heat emissions. The materials of the junctions and electrodes are selected taking into account the energy of the electrons.Result. Energy saving of processes has increased in thermoelectric generators by reducing parasitic Joule heat generation, reducing parasitic conductive transfer and additional energy generation from metal electrodes.Conclusion. The conducted studies allow us to conclude that in order to increase the energy saving of thermoelectric generators for autonomous power supply of the cooling apparatus of the heat-generating electronic components, it is necessary to topologically separate the heated and cooled zones of the generator into different levels in space, and to manufacture semiconductor branches using thin-film technology and additionally cool the generator junctions with ventilation, and additionally recover energy from the heat-generating components on the heated junctions.

Abstract The advent of digital technology has revolutionized the way we keep track of time. Digital watches have become an essential part of our daily lives and provide us with accurate and reliable time measurement. However, battery reliability is a long-standing issue in the digital watch industry. Batteries require frequent replacement and are a major source of waste. To solve this problem, a digital watch that runs on a lithium-polymer battery that is recharged by a voltage generated by a thermoelectric generator (TEG) placed on the hand. The proposed model uses TEG1-19913 that generates power in the range of 11.5 W to 14.5 W with hot end basking at 250 °C and a cold end between 30 °C and 50 °C. The TEG voltage is used to charge the lithium polymer battery, eliminating the need for conventional charging methods. The watch is designed to be compact and lightweight, so it can be worn comfortably for extended periods of time. The TEG is integrated into the watch strap and ensures that it is constantly in contact with the skin. The lithium-polymer battery used in the watch is a high-performance rechargeable battery that has high energy density and long life. In summary, the proposed digital watch is an innovative ecological solution to the problems associated with traditional battery-powered watches. The compact and light design of the watch combined with the energy-efficient display makes it a convenient and efficient timekeeping device.

This paper deals with incorporating thermoelectric generators into wood-fired stove to enhance energy efficiency and explore sustainable heating solutions. Wood-fired stoves are essential solutions for heating and cooking, but their conventional design poses environmental impact and efficiency challenges. By utilizing thermoelectric generators to capture waste heat, this research aims to elevate the overall performance of wood-fired stoves, reduce emissions, and optimize energy conversion. Through comprehensive experimental data and analysis, the study sheds light on the potential of thermoelectric generator integration, even in manually operated wood-fired stoves. The research stages outlined in the paper focus on selecting the most favorable conditions for thermoelectric generator installation, revealing that thermoelectric generators' highest power generation efficacy reached around 42% in a stove without an accumulation layer and slightly exceeded 30% in a stove with an accumulation layer.

Thermoelectric (TE) structures based on energy harvesting technology have played a vital role in wide‐reaching applications. In this study, a composite structure consisting of a glass fabric covered with a nanocomposite membrane (polyacrylonitrile [PAN]/carbon nanotube [CNT]/copper oxide nanoparticle [CuO]) was prepared to provide thermoelectric conversion. The performance of the TE composite structure was evaluated by analyzing the mechanical properties, thermoelectric properties, and the ability of the structure to power small electronic equipment. The results showed that the nanocomposite membrane was effective in improving the electrical properties, whereas the glass fabric could significantly suppress the thermal conductivity. The results suggest that the glass fabric covered with nanocomposite fibers containing nanofillers (15 wt% CNT & 15 wt% CuO) has a high potential to enhance the resistance against external force by 56% on average, compared to the uncovered glass fabric. Besides the power factor of the TE composite structure can reach up to 19.61 μW m−1 K−2, which can power an output voltage of 3.2 V at a temperature difference from 20 to 80°C. [ABSTRACT FROM AUTHOR]

In this study, a neural network and a multi-objective genetic algorithm were used to optimize the geometric parameters of segmented thermoelectric generators (TEGs) with trapezoidal legs, including the cold end width of thermoelectric (TE) legs (Wc), the ratios of cold-segmented length to the total lengths of the n- and p-legs (Sn,c and Sp,c), and the width ratios of the TE legs between the hot end and the cold end of the n- and p-legs (Kn and Kp). First, a neural network with high prediction accuracy was trained based on 5000 sets of parameters and the corresponding output power values of the TEGs obtained from finite element simulations. Then, based on the trained neural network, the multi-objective genetic algorithm was applied to optimize the geometric parameters of the segmented TEGs with the objectives of maximizing the output power (P) and minimizing the semiconductor volume (V). The optimal geometric parameters for different semiconductor volumes were obtained, and their variations were analyzed. The results indicated that the optimal Sn,c, Sp,c, Kn, and Kp remained almost unchanged when V increased from 52.8 to 216.2 mm3 for different semiconductor volumes. This work provides practical guidance for the design of segmented TEGs with trapezoidal legs. [ABSTRACT FROM AUTHOR]

Bismuth telluride-based materials are well known for their excellent thermoelectric (TE) properties within the near-room temperature range. However, the poor thermoelectric performance of their n-type counterparts has posed a major hindrance to the application of bismuth telluride-based thermoelectric generator (TEG). In this study, a dual optimization approach was implemented. Specifically, 2D ceramic nano-sized hexagonal boron nitride (h-BN) was introduced into n-type Bi 2 Te 2.7 Se 0.3 (BTS) to enhance its performance, aligning it with p-type materials. It is indicated that ceramic h-BN decoration leads to the emergence of a high density of dislocations, which boosts the phonon scattering and reduces lattice thermal conductivity significantly. Meanwhile, a high carrier mobility is maintained to ensure an improved power factor. With the addition of moderate ceramic h-BN, the composite material achieved a ZT value of 1.1 at 400 K. The geometric configuration of TEG was optimized using finite element methods to strike the optimal balance between output power (P o u t ) and efficiency (η). Based on the structure optimization results, the predicted P o u t and η increased by 48 % and 36 %, respectively. The fabricated TEG demonstrated to achieve an efficiency of 6.4 %. This work allows the evolution from bismuth telluride-based prototype to a functional TEG advanced in room-temperature heat recovery. [ABSTRACT FROM AUTHOR]

Harvesting ambient temperature is attractive for different purposes. In this paper, a pioneer study on thermoelectric power generation using natural diurnal temperature difference between ambient and indoor space through glazed windows (TEGW) is investigated experimentally. To this end, a small south facing window with 5 mm green tinted glass, 0.45 m wide and 1.05 m high located in a room of 25.74 m³ volume located at the first floor of a residential house in Nonthaburi province (Thailand) was used. Three thermoelectric (TE) modules (MT2-1, 6-127) 40×40 mm were installed at the inner side of the glass window at three positions near the top, middle and bottom. Tests were conducted with close and open curtain and air and non-air-conditioned spaces. Measured data demonstrated that the proposed concept is feasible as an electrical current could be generated: The hotter the day, the higher is the temperature difference between the hot and cold sides of TE modules and the higher the amount of current generated. When air conditioning is used, the temperature difference between the sides of TE modules increased and higher electrical voltage is generated varying between 0.5-1.9 mV compared to 0.1-0.6 mV without air conditioning. Closing curtain did affect the generated electrical voltage significantly as it reduced the cooling of the inner side of TE modules due to reduced air circulation especially at the middle and top of window. Due to its simplicity, the proposed concept offers new perspectives for thermoelectric power generation development and its application in residences and buildings. [ABSTRACT FROM AUTHOR]

In the present work, a novel photovoltaic-thermal-thermoelectric generator (PVT-TEG) based solar dryer has been developed, and its drying performance is experimentally investigated and compared with open sun drying (OSD). The reason for incorporating the PVT-TEG system in the solar dryer is to improve the system's utility in practical drying applications by augmenting electrical power generation with the combination of PV and TEG along with extracting thermal energy for drying, thereby improving the overall system efficiency. Grapes drying has been performed to analyze the drying process and thermal and electrical performance of the system. The moisture content level after the experiment is evaluated as 1.71 (d.b.) from an initial value of 4.00 (d.b.) in PVT-TEG solar drying compared with 2.51 (d.b.) in OSD. The findings of the drying performance are determined as 17.81% for drying efficiency, 1.10 kWh/kg for specific energy consumption, and 0.68 kg/kWh for specific moisture extraction rate. The energy efficiencies obtained for the experiment are PV panel efficiency of 14.07%, TEG efficiency of 11.64%, PVT efficiency of 72.36%, and thermal efficiency of 48.50%. When compared to the open literature, the utility of the present novel dryer is found in terms of its enhanced drying and energy performances. [ABSTRACT FROM AUTHOR]

This study investigates the application of thermoelectric power generation devices in conjunction with cold chain logistics transport vehicles, focusing on their efficiency and performance. Our experimental results highlight the impact of thermoelectric module characteristics, such as thermal conductivity and the filling thickness of copper foam, on the energy utilization efficiency of the system. The specific experimental setup involved a simulated logistics cold chain transport vehicle exhaust waste heat recovery thermoelectric power generation system, consisting of a high-temperature exhaust heat exchanger channel and two side cooling water tanks. Thermoelectric modules (TEMs) were installed between the heat exchanger and the water tanks to use the temperature difference and convert heat energy into electrical energy. The analysis demonstrates that using high-performance thermoelectric modules with a lower thermal conductivity results in better utilization of the temperature difference for power generation. Additionally, the insertion of porous metal copper foam within the heat exchanger channel enhances convective heat transfer, leading to an improved performance. Furthermore, the study examines the concepts of exergy and entropy generation, providing insights into the system energy conversion processes and efficiency. Overall, this research offers valuable insights for optimizing the design and operation of thermoelectric generators in cold chain logistics transport vehicles to enhance energy utilization and sustainability. [ABSTRACT FROM AUTHOR]

This study evaluates the potential of a twin-screw compressor as a heat source to harness thermal energy. Thermoelectric generators are a feasible solution for microenergy harvesting from waste heat based on the Seebeck effect. Thermographic infrared images of the compressor were used to assess potential installation spots. The physical mounting of the thermoelectric modules must consider certain hindering aspects. At first, the compressor skid is subject to standards and authorizations for its components, leaving only a couple of spots for screw-mounted module installations. Another inconvenience is the bonds in any thermoelectric material causing them not to withstand lateral mechanical stress in other directions except the c-axis perpendicular to the layers. Therefore, vibration measurements have to be performed beforehand. Numerical simulations were conducted, relying on the acquired thermoelectric modules as well as on the temperature and vibration data measured on the compressor. The thermoelectric generators studied are part of a multisource piezoelectric and thermoelectric energy harvesting system under research and development. [ABSTRACT FROM AUTHOR]

Thermoelectric generators (TEGs) are widely employed in microscale applications to generate power from waste-heat energy emitted by nonrenewable energy sources. The energy extracted from TEG is dependent on the temperature gradient across the hot- and cold-ends along with the electrical load applied. Therefore, a maximum power point tracking (MPPT) control is strongly preferred to constantly track the optimal point of TEG under diverse operational conditions. In this study, a new MPPT-based metaheuristic optimizer so-called Honey badger algorithm (HBA) is implemented to maximize the energy efficiency of TEG systems. The proposed technique seeks to optimize the dynamic response and eradicate oscillations near MPP. Various dynamic operating conditions are used to investigate the reliability of the optimized HBA-based MPPT method. The obtained results are compared with other energy harvesting approaches including incremental conductance (INC), hybrid gray wolf optimizer-sine cosine algorithm (HGWOSCA), and marine predators algorithm (MPA). The major findings verify that the employed optimized HBA method achieved highest power tracking efficiency more than 99 % with smallest tracking time up to 120 ms and maintaining a steady-state output at the different studied scenarios. [ABSTRACT FROM AUTHOR]

A cylindrical thermoelectric power generator for high-temperature flue gas was designed, and a distributor was installed to enhance heat transfer by affecting the jet on the hot side. The influence of the different distributor diameters and jet hole diameters on the temperature distribution of the hot and cold sides of the thermoelectric module was studied. The corresponding temperature field, velocity field, and exhaust pressure drop of the device were also obtained. The results indicated that the temperature difference between the hot and cold ends of the thermoelectric module was increased, and the uniformity of the temperature distribution was improved with the increasing diameter of the distributor and the decreasing diameter of the jet hole. The performance of the thermoelectric power generator was further improved by the jet hole with a gradient diameter. The number and distance between jet holes were sensitive to pressure drop. [ABSTRACT FROM AUTHOR]