Textile-Based Thermoelectric Generators and Their Applications

With the rapid development of Internet of Things and miniaturized electronics, the demand for wearable power sources with high reliability and long duty cycle promotes the exploration of wearable thermoelectric generators(TEGs). In particular, textile-based TEGs that can perpetually convert the ubiquitous temperature gradient between human body and ambience into electrical energy have attracted intensive attention to date.These lightweight and three-dimensional deformable TEGs comprised of fibers, filaments, yarns, or fabrics offer unique merits as wearable power source in comparison with conventional TEGs. In this review, we systematically summarize the state-of-the-art strategies for textile-based TEGs, including the structure design, fabrication, device performance, and application. Existing critical issues and future research emphasis are also discussed.

Solar-and/or Radiative Cooling-Driven Thermoelectric Generators:A Critical Review

Thermoelectric generators(TEGs)play a critical role in collecting renewable energy fromthe sun and deep space to generate clean electricity.With their environmentally friendly,reliable,and noise-free operation,TEGs offer diverse applications,including areas with limited power infrastructure,microelectronic devices,and wearable technology.The review thoroughly analyses TEG system configurations,performance,and applications driven by solar and/or radiative cooling,covering non-concentrating,concentrating,radiative cooling-driven,and dual-mode TEGs.Materials for solar absorbers and radiative coolers,simulation techniques,energy storage management,and thermal management strategies are explored.The integration of TEGs with combined heat and power systems is identified as a promising application.Additionally,TEGs hold potential as charging sources for electronic devices.This comprehensive review provides valuable insights into this energy collection approach,facilitating improved efficiency,reduced costs,and expanded applications.It also highlights current limitations and knowledge gaps,emphasizing the importance of further research and development in unlocking the full potential of TEGs for a sustainable and efficient energy future.

Recovery of Solid Oxide Fuel CellWaste Heat by Thermoelectric Generators and AlkaliMetal Thermoelectric Converters

A Solid Oxide Fuel Cell(SOFC)is an electrochemical device that converts the chemical energy of a substance into electrical energy through an oxidation-reduction mechanism.The electrochemical reaction of a solid oxide fuel cell(SOFC)generates heat,and this heat can be recovered and put to use in a waste heat recovery system.In addition to preheating the fuel and oxidant,producing steam for industrial use,and heating and cooling enclosed rooms,this waste heat can be used for many more productive uses.The large waste heat produced by SOFCs is a worry that must be managed if they are to be adopted as a viable option in the power generation business.In light of these findings,a novel approach to SOFC waste heat recovery is proposed.The SOFC is combined with a“Thermoelectric Generator and an Alkali Metal Thermoelectric Converter(TG-AMTC)”to transform the excess heat generated by both the SOFC and the TG-AMTC.The proposed TG-AMTC is evaluated using a number of performance indicators including power density,operating temperature,heat recovery rate,exergetic efficiency,energy efficiency,and recovery time.The experimental results state that TG-AMTC has provided an exergetic efficiency,energetic efficiency,and recovery time of 97%,98%,and 23%,respectively.The study proves that the proposed TG-AMTC for SOFC is an efficient method of recovering waste heat.

The Method of Thermoelectric Energy Generations Based on the Axial and Radial Flux Electromagnetic Inductions*

The traditional thermoelectric energy conversion techniques are explained in detail in terms of the axial flux electromagnetic (AFE) and the radial flux electromagnetic (RFE) inductions, and applications to heat engines for the energy-harvesting technologies are discussed. The idea is induced by the analysis of thermomechanical dynamics (TMD) for a nonequilibrium irreversible thermodynamic system of heat engines (a drinking bird, a low temperature Stirling engine), resulting in thermoelectric energy generation different from conventional heat engines. The mechanism of thermoelectric energy conversion can be categorized as the axial flux generator (AFG) and the radial flux generator (RFG). The axial flux generator is helpful for low mechanoelectric energy conversion and activations of waste heat from macroscopic energy generators, such as wind, geothermal, thermal, nuclear power plants and heat-dissipation lines, and the device contributes to solving environmental problems to maintain clean and sustainable energy as one of the energy harvesting technologies.

Water-resistant organic thermoelectric generator with >10μW output

Flexible p–n thermoelectric generator(TEG)technology has rapidly advanced with power enhancement and size reduction.To achieve a stable power supply and highly efficient energy conversion,absolute chemical stability of n-type materials is essential to ensuring large temperature differences between device terminals and ambient stability.With the aim of improving the long-term stability of the n-type operation of carbon nanotubes(CNTs)in air and water,this study uses cationic surfactants,such as octylene-1,8-bis(dimethyldodecylammonium bromide)(12-8-12),a gemini surfactant,to stabilize the nanotubes in a coating,which retains the n-doped state for more than 28 days after exposure to air and water in experiments.TEGs with 10 p-n units of 12-8-12/CNT(n-type)and sodium dodecylbenzene sulfonate/CNT(p-type)layers are manufactured,and their water stability is evaluated.The initial maximum output of 16.1μW(75 K temperature difference)is retained after water immersion for 40 days without using a sealant to prevent TEG module degradation.The excellent stability of these CNT-based TEGs makes them suitable for underwater applications,such as battery-free health monitoring and information gathering systems,and facilitates the development of soft electronics.

Waste Heat Recovery from a Drier Receiver of an A/C Unit Using Thermoelectric Generators

Thermoelectric generators(TEGs)are considered promising devices for waste heat recovery from various systems.The Seebeck effect can be utilized to generate power using the residual heat emitted by the filter dryer receiver(FDR)of an air conditioning(A/C)system,which would otherwise go to waste.The study aims to build a set of thermoelectric generators(TEG)to collect the waste heat of the FDR and generate low-power electricity.A novel electrical circuit with two transformers is designed and fabricated to produce a more stable voltage for operation and charging.The thermoelectric generator(TEGs)was installed on the FDR of the A/C unit.The test showed that climate conditions have a significant impact on the output power generated from the system.The results showed that the peak voltage recorded in the current study is 5.2 V per day(wet,cold,and wind weather)with an output power of 0.2 W.These values are acceptable for powering the load and charging a single battery with 3.5 V as the voltage increases battery 0.1 V/20 min charge.A case study of operating the emergency signs in a building was considered.The current heat recovery system is deemed to be easily installed and can be connected to a network of TEGs to produce more power.

The Application of Thermomechanical Dynamics (TMD) to Thermoelectric Energy Generation by Employing a Low Temperature Stirling Engine

A thermoelectric generation Stirling engine (TEG-Stirling engine) is discussed by employing a low temperature Stirling engine and the dissipative equation of motion derived from the method of thermomechanical dynamics (TMD). The results and mechanism of axial flux electromagnetic induction (AF-EMI) are applied to a low temperature Stirling engine, resulting in a TEG-Stirling engine. The method of TMD produced thermodynamically consistent and time-dependent physical quantities for the first time, such as internal energy ℰ(t), thermodynamic work Wth(t), the total entropy (heat dissipation) Qd(t)and measure or temperature of a nonequilibrium state T˜(t). The TMD analysis produced a lightweight mechanical system of TEG-Stirling engine which derives electric power from waste heat of temperature (40˚CT100˚C) by a thermoelectric conversion method. An optimal low rotational speed about 30θ′(t)/(2π)60(rpm) is found, applicable to devices for sustainable, clean energy technologies. The stability of a thermal state and angular rotations of TEG-Stirling engine are specifically shown by employing properties of nonequilibrium temperature T˜(t), which is also applied to study optimal fuel-injection and combustion timings of heat engines.

Thermoelectric generators and their applications:Progress,challenges,and future prospects

Our community currently deals with issues such as rising electricity costs,pollution,and global warming.Scientists work to improve energy harvesting-based power generators in order to reduce their impacts.The Seebeck effect has been used to illustrate the capacity of thermoelectric generators(TEGs)to directly convert thermal energy to electrical energy.They are also ecologically beneficial since they do not include chemical products,function quietly because they lack mechanical structures and/or moving components,and may be built using different fabrication technologies such as three-dimentional(3D)printing,silicon technology,and screen printing,etc.TEGs are also position-independent and have a long operational lifetime.TEGs can be integrated into bulk and flexible devices.This review gives further investigation of TEGs,beginning with a full discussion of their operating principle,kinds,materials utilized,figure of merit,and improvement approaches,which include various thermoelectric material arrangements and utilised technologies.This paper also discusses the use of TEGs in a variety of disciplines such as automobile and biomedical.

Powering a Low Power Wireless Sensor in a Harsh Industrial Environment: Energy Recovery with a Thermoelectric Generator and Storage on Supercapacitors

Wireless sensor networks are widely used for monitoring in remote areas. They mainly consist of wireless sensor nodes, which are usually powered by batteries with limited capacity, but are expected to last for long periods of time. To overcome these limitations and achieve perpetual autonomy, an energy harvesting technique using a thermoelectric generator (TEG) coupled with storage on supercapacitors is proposed. The originality of the work lies in the presentation of a maintenance-free, robust, and tested solution, well adapted to a harsh industrial context with a permanent temperature gradient. The harvesting part, which is attached to the hot spot in a few seconds using magnets, can withstand temperatures of 200°C. The storage unit, which contains the electronics and supercapacitors, operates at temperatures of up to 80°C. More specifically, this article describes the final design of a 3.3 V 60 mA battery-free power supply. An analysis of the thermal potential and the electrical power that can be recovered is presented, followed by the design of the main electronic stages: energy recovery using a BQ25504, storage on supercapacitors and finally shaping the output voltage with a boost (TPS610995) followed by an LDO (TPS71533).

Thermoelectric Stirling Engine (TEG-Stirling Engine) Based on the Analysis of Thermomechanical Dynamics (TMD)

The thermoelectric energy conversion technique by employing the Disk-Magnet Electromagnetic Induction (DM-EMI) is examined in detail, and possible applications to heat engines as one of the energy-harvesting technologies are discussed. The idea is induced by the analysis of thermomechanical dynamics (TMD) for a nonequilibrium irreversible thermodynamic system of heat engines, such as a drinking bird and a low temperature Stirling engine, resulting in thermoelectric energy generation different from conventional heat engines. The current thermoelectric energy conversion with DM-EMI can be applied to wide ranges of machines and temperature differences. The mechanism of DM-EMI energy converter is categorized as the axial flux generator (AFG), which is the reason why the technology is applicable to sensitive thermoelectric conversions. On the other hand, almost all the conventional turbines use the radius flux generator to extract huge electric power, which uses the radial flux generator (RFG). The axial flux generator is helpful for a low mechanoelectric energy conversion and activations of waste heat from macroscopic energy generators such as wind, geothermal, thermal, nuclear power plants and heat-dissipation lines. The technique of DM-EMI will contribute to solving environmental problems to maintain clean and sustainable energy as one of the energy harvesting technologies.

Optimal Control of a Thermoelectric Generator Attached with a Latent Heat Accumulator

Generally MPPT control (maximum power point tracking) is adopted to control of a thermoelectric generator. However, in the case of generation by use of a heat accumulator MPPT control cannot obtain maximum whole electrical output during the operation period. This is because the amount of heat stored in a heat accumulator is limited and easy to be exhausted rapidly by MPPT. Therefore MEPT (Maximum Efficiency Point Tracking) control should be developed to obtain maximum power from limited heat stored in the heat accumulator. When thermoelectric generator is used for waste heat recovery, conversion efficiency is quite difficult to be measured. This is due to time delay between the change of temperature profile in the thermoelectric generator and the change of heat medium temperature. Decrease of output current is desired to enlarge output because decrease of current decreases Peltier heat and improves efficiency of heat recovery. The experimental results indicate that current fluctuated by MPPT control causes loss of power output. We proposed the optimal control in which current is 10% smaller than one of MPPT control and evaluated it experimentally. We call this control scheme MEPT control. In this evaluation 500 W class thermoelectric generator, latent heat accumulator and the test facilities included 30 kW electric heater are utilized. Experimental result shows MEPT control exceeds MPPT in total electricity recovered from heat accumulator.

Smart Thermoelectric Earth-Air Generator Safety System

In this study,the soil-air generator of the thermoelectric safety system working with soil heat was investigated.For this,a special electronic safety device was made and the output parameters of the device were investigated.In order to investigate the operation of the thermoelectric“earth-air”generator safety system in real nature conditions,temperatures at the soil depth and soil surface equal to the length of the generator in four different regions of Ankara in four seasons were measured and modeled.Afterwards,physical parameters such as power P(W),voltage U(V)and current I(A)produced by the generator according toΔT were examined by using all this scientific information with a special test setup.According to the results obtained,it has been determined that the Intelligent thermoelectric earth-air generator safety system(ATES)has the feature of notifying the security units in case of area violation by generating its own electricity with the help of the heat in the soil without the need for any electrical cable.In addition,the environmentally friendly ATES system is an innovative product and it has been seen that it will be used in various fields,especially in military applications.

A Thermoelectric Generator Manufacture Research Based on Oscillating-Flow Heat Pipe Technology

Oscillating heat pipe is a new type of heat transfer. It not only has simple structure, non-pollution and low maintenance cost, but also has high heat transfer efficiency. Semiconductor thermoelectric generation technology is also an environmental technology. This article combines these two kinds of technology. By means of this generate electricity way, we make a set of system and the related experiment. Then we do some research on the feasibility of this system.

Impacts of thermal and electric contact resistance on the material design in segmented thermoelectric generators

Segmented thermoelectric generators(STEGs)can exhibit present superior performance than those of the conventional thermoelectric generators.Thermal and electrical contact resistances exist between the thermoelectric material interfaces in each thermoelectric leg.This may significantly hinder performance improvement.In this study,a five-layer STEG with three pairs of thermoelectric(TE)materials was investigated considering the thermal and electrical contact resistances on the material contact surface.The STEG performance under different contact resistances with various combinations of TE materials were analyzed.The relationship between the material sequence and performance indicators under different contact resistances is established by machine learning.Based on the genetic algorithm,for each contact resistance combination,the optimal material sequences were identified by maximizing the electric power and energy conversion efficiency.To reveal the underlying mechanism that determines the heat-to-electrical performance,the total electrical resistance,output voltage,ZT value,and temperature distribution under each optimized scenario were analyzed.The STEG can augment the heat-to-electricity performance only at small contact resistances.A large contact resistance significantly reduces the performance.At an electrical contact resistance of RE=10^(-3) K⋅m^(2)⋅W^(-1) and thermal contact resistance of RT=10-8Ω⋅m^(2),the maximum electric power was reduced to 5.71 mW(90.86 mW without considering the contact resistance).And the maximum energy conversion efficiency is lowered to 2.54%(12.59%without considering the contact resistance).

Electricity Generation from Heatwaves

We chose a definition of heatwaves (HWs) that has ~4-year recurrence frequency at world hot spots. We first examined the 1940-2022 HWs climatology and trends in lifespan, severity, spatial extent, and recurrence frequency. HWs are becoming more frequent and more severe for extratropical mid- and low-latitudes. To euphemize HWs, we here propose a novel clean energy-tapping concept that utilizes the available nano-technology, micro-meteorology knowledge of temperature distribution within/without buildings, and radiative properties of earth atmosphere. The key points for a practical electricity generation scheme from HWs are defogging, insulation, and minimizing the absorption of infrared downward radiation at the cold legs of the thermoelectric generators. One sample realization is presented which, through relay with existing photovoltaic devices, provides all-day electricity supply sufficient for providing air conditioning requirement for a residence (~2000-watt throughput). The provision of power to air conditioning systems, usually imposes a significant stress on traditional city power grids during heatwaves.

Experimental Research on Tank Exhaust's Thermal Restraint Based on Thermoelectric Generation Theory

Aimed at the high temperature of tank's exhaust, the principle of applying thermoelectric generation technology to tank thermal restraint was analyzed. Its application experiments were conducted to test the exhaust temperature under different rotating speeds, The experiment results show that the thermoelectric generator can output sufficient electric energy to drive fans; the external surface temperature of radiator is reduced by over 65.0% compared with exhaust surface due to the combination effect of thermoelectric conversion, fan cooling and heat radiation; the exhaust surface temperature rise caused by increase of the engine's rotating speed results in the increases of the temperature difference of the thermoelectric generator's cold and hot sides, the fan's driving voltage and heat convection, thus, the effect of fan's cooling is more obvious than that of the temperature rise caused by exhaust.

Further Stabilization and Power Density Improvement of Stack-Type Thermoelectric Power Generating Module with Biphasic Medium by Using Various Flexible Metals as Electrodes

In order to realize further stability of a stack-type thermoelectric power generating module (i.e. no electrical connections inside), flexible materials of metal springs and/or rods having restoring forces were installed between lower-temperature-sides of thermoelectric elements. These flexible materials were expected to play three important roles of interpolating different thermal expansions of the module components, enlarging heat removal area and penetration of any media through themselves. Then, a low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) was also applied for a high-speed direct heat removal via its phase change from the lower-temperature-sides of the thermoelectric elements in the proposing stack-type thermoelectric power generating module. No electrical disconnections inside the module were confirmed for more than 9 years of use, indicating further module stability. The power generating density was improved to about 120 mW·m-2 with SUS304 springs having 0.7 mm diameter. Increasing power generating density can be expected in terms of suitable selection of flexible metal with high Vickers hardness, cavities control on the spring surface, more vigorous multiphase flow with adding powders to the medium and optimization of the module configurations according to numerical simulations.

Improving the performance of a thermoelectric power system using a flat-plate heat pipe

A gravitational flat-plate heat pipe is designed and fabricated in this paper to serve as a heat spreader to diffuse the local heat source to the hot side of the thermoelectric power module.Based on this, an experimental test for the thermoelectric power generation system is conducted to study the influences of the heat spreader on the temperature uniformity and power generation performance when exposing to a local heat source.In addition,the effects of the heating power, inclination angle, and local heat source size on the power generation performance of the thermoelectric power module using a flat-plate heat pipe as a heat spreader are examined and compared with that using a metal plate.The results indicate that the gravitational flat-plate heat pipe has considerable advantages over the metal plate in the temperature uniformity.The superiority of temperature uniformity in the improvement of power generation performance for the thermoelectric power system using a heat pipe is demonstrated.Particularly, the heat pipe shows good adaptability to placement mode and the local heat source size, which is beneficial to the application in the thermoelectric power generation.

The Disk-Magnet Electromagnetic Induction Applied to Thermoelectric Energy Conversions

The thermoelectric energy conversion technique by employing the Disk-Magnet Electromagnetic Induction (DM-EMI) and improved DM-EMIs is shown, and possible applications to heat engines as one of the energy harvesting technologies are also discussed. The idea is induced by integrating irreversible thermodynamical mechanism of a water drinking bird with that of a Stirling engine, resulting in thermoelectric energy generation different from conventional heat engines. The current thermoelectric energy conversion with DM-EMI can be applied to wide ranges of temperature differences. The mechanism of DM-EMI energy converter is examined in terms of axial flux magnetic lines and categorized as the axial flux generator. It is useful for practical applications to macroscopic heat engines such as wind, geothermal, thermal and nuclear power turbines and heat-dissipation lines, for supporting thermoelectric energy conversions. The technique of DM-EMI will contribute to environmental problems to maintain clean and susceptible energy as one of the energy harvesting technologies.

Mechanical properties of thermoelectric generators

To satisfy the requirements of practical applications,thermoelectric generators should be highly efficient and mechanically robust.Recently,progress in designing high-performance thermoelectric generators has been made.However,the mechanical properties of thermoelectric generators are still unsatisfactory.In this review,studies on the mechanical properties of thermoelectric generators are summarized.The me-chanical properties of bulk thermoelectric generators will be first discussed.In this section,the mechan-ical properties of thermoelectric materials and the strategies for improving their mechanical properties are emphasized.Since the device’s failure usually occurs at the interface between the thermoelectric ma-terials and electrode,the joint strength of electrodes and thermoelectric materials will be overviewed.After that,the mechanical properties of the inorganic thin-film thermoelectric devices will be discussed.Since the figure of merit for the flexibility of thermoelectric materials depends on the film thickness,elastic modulus,and yield strength,the synthesis methods of thin-film thermoelectric materials will be reviewed.Finally,this review will be concluded with a discussion on flexible organic thermoelectric de-vices and flexible devices using bulk legs.