Bi2Te3基可穿戴温差发电器件的制备及性能

利用人体体温发电的热电器件因其结构简单、可靠性高,有望为可穿戴电子产品等低功耗设备提供免维护、长期稳定的能源。以高性能无机块体热电材料和低热导环氧树脂/玻璃微珠复合粘结剂作为原料,采用切割粘结法和磁控溅射/电化学镀铜技术,制备了热电臂高度不同的48对温差发电器件。由于该技术不需使用陶瓷覆铜板,在给定的器件厚度条件下,可提高热电臂高度。性能表征结果显示,在实际穿戴条件下,随热电臂高度的增加,器件的输出功率密度持续增加。在相当于一级风的空气对流条件下或正常行走状态下,热电臂高度为3.14mm的器件输出功率密度超过40μW/cm²。     

面向LNG汽车的发动机排气与低温燃料温差发电器研究

为实现液化天然气（LNG）汽车的节能,提出了利用温差发电器（TEG）回收发动机排气（EG）的废热和低温燃料的冷能。指出了基于冷源所在的低温区,以及EG与LNG之间的大温差这两个特点,TEG的热电转换效率会高于常规。基于对小型LNG汽车中典型燃料系统的分析,设计了进行能量回收的两种系统流程,计算了其中各状态点的参数、及各换热器中布置温差发电器后的热电转换效率,得到了系统总的回收功率。结果表明,汽化器系统的回收功率大于自复温系统;在两种系统中,合理选取多种材料相较于仅用单种材料,TEG的回收功率更大。     

Integration of dye-sensitized solar cells, thermoelectric modules and electrical storage loop system to constitute a novel photothermoelectric generator

This study self-develops a novel type of photothermoelectric power generation modules. Dye-sensitized solar cells (DSSCs) serve as the photoelectric conversion system and a copper (Cu) heat-transfer nanofilm coating on both sides of the thermoelectric generator (TEG) acts as a thermoelectric conversion system. Thus module assembly absorbs light and generates electricity by DSSCs, and also recycles waste heat and generates power by the TEG. In addition, a set of pulsating heat pipes (PHP) filled with Cu nanofluid is placed on the cooling side to increase cooling effects and enhance the power generation efficiency. Results show that when the heat source of thermoelectric modules reaches 90 degrees C, TEG power output is increased by 85.7%. Besides, after thermoelectric modules are heated by additional heat source at 80 degrees C, the electrical energy generated by them can let a NiMH cell (1.25 V) be sufficiently charged in about 30 minutes. When photothermoelectric modules is illumined by simulated light, the temperature difference of two sides of TEG can reach 7 degrees C and the thermoelectric conversion efficiency is 2.17%. Furthermore, the power output of the thermoelectric modules is 11.48 mW/cm2, enhancing 1.4 % compared to merely using DSSCs module.     

Thermoelectric textile devices with thin films of nanocellulose and copper iodide

Owing to the rapid development of wearable electronics and smart textiles, demands for flexible and wearable thermoelectric (TE) devices, which can generate electricity in a ubiquitous, unintermittent and noiseless way for on-body applications are growing rapidly. Due to the inherent flexibility and wearability features, textile-based thermoelectric generators (TEGs) possess significant potential for biomedical and consumer health and safety applications. In this study, using commercial cotton fabric, we created efficient thermoelectric (TE) textile that, unlike analogs, is based on thin-film composite of biocompatible semiconductor copper iodide (CuI) and biodegradable polymer nanocellulose (NC_p) obtained by processing a widespread plant common reed. The CuI films with average thickness 10 µm were deposited via low-temperature aqueous cheap, facile, and scalable fabrication technique Successive Ionic Layer Adsorption and Reaction (SILAR). The NC_p sublayer made it possible to fabricate thin-film ohmic contacts through vacuum deposition of chromium on the nanostructured CuI film in the TE textile. The topping of CuI film with NC_p layer improved durability and wear resistance of the wearable thermoelectric module fabricated with this TE textile. The developed TE module has shown output power density 44 µW/cm² at temperature gradient 50 K that is among the best currently known results for solid miniature flexible and fabric-based TEGs.

     

Miniaturized planar Si-nanowire micro-thermoelectric generator using exuded thermal field for power generation

For harvesting energy from waste heat, the power generation densities and fabrication costs of thermoelectric generators (TEGs) are considered more important than their conversion efficiency because waste heat energy is essentially obtained free of charge. In this study, we propose a miniaturized planar Si-nanowire micro-thermoelectric generator (SiNW-μTEG) architecture, which could be simply fabricated using the complementary metal–oxide–semiconductor–compatible process. Compared with the conventional nanowire μTEGs, this SiNW-μTEG features the use of an exuded thermal field for power generation. Thus, there is no need to etch away the substrate to form suspended SiNWs, which leads to a low fabrication cost and well-protected SiNWs. We experimentally demonstrate that the power generation density of the SiNW-μTEGs was enhanced by four orders of magnitude when the SiNWs were shortened from 280 to 8 μm. Furthermore, we reduced the parasitic thermal resistance, which becomes significant in the shortened SiNW-μTEGs, by optimizing the fabrication process of AlN films as a thermally conductive layer. As a result, the power generation density of the SiNW-μTEGs was enhanced by an order of magnitude for reactive sputtering as compared to non-reactive sputtering process. A power density of 27.9 nW/cm² has been achieved. By measuring the thermal conductivities of the two AlN films, we found that the reduction in the parasitic thermal resistance was caused by an increase in the thermal conductivity of the AlN film and a decrease in the thermal boundary resistance.     

Performance improvement of a transcritical CO2 refrigeration cycle using two-stage thermoelectric modules in sub-cooler and gas cooler

A novel integration of a trans-critical CO₂ refrigeration cycle with thermoelectric modules in the gas cooler and sub-cooler is presented, wherein a two-stage thermoelectric generator (TEG) produces power from the waste heat of gas cooler, which is a considerable amount of required power in two-stage thermoelectric cooler (TEC) to sub-cool the refrigerant before expansion device. Mathematical simulation of TEG and TEC as well as energy and exergy based thermodynamic analysis of the proposed system is performed, and the effects of some important parameters on the system performance are investigated. A comparison is carried out between the proposed system and the simple CO₂ refrigeration cycle, indicating that the proposed configuration improves the coefficient of performance (COP) about 19%. Also, it is observed that the TEC and TEG have better performance in a two-stage configuration. The parametric study reveals that the new configuration decreases the cycle operation pressure at maximum COP and exergetic efficiency.     

Pushing thermoelectric generators toward energy harvesting from the human body: Challenges and strategies

Advances in miniaturized portable electronics and progress on novel enabling technologies, consequently accompanied by power consumption downgraded from the scale of milliwatts (mW) to microwatts (μW), have inevitably facilitate the development of an emerging discipline-wearable human energy conversion systems. Served as a passive human energy harvester which can directly convert heat into electricity in long-term operations without the user’s intervention, wearable thermoelectric generators (WTEG) have sparked considerable research interest for next-generation power supply. In comparison to the longstanding research history of thermoelectrics, their wearables are still in infancy of extensive growth over the last decade. Although, historically, the main challenge behind the conventional thermoelectric generator (TEG) is the improvement of dimensionless figure-of-merit (zT), wearable applications usually impose additional restrictions that can be more pivotal than zT value. Diversified targeted strategies therefore have been proposed to push TEG toward wearable application. Here, we review the evolutionary roadmap of the wearable thermoelectric generators in the past decade, it could be concluded that the trend in WTEG is to move toward stretchable three-dimension (3D)-structure with rational thermal design at the moment. The basic concept targeting WTEG, which highly differs from that of the traditional TEG, is introduced at first. And then, aiming to provide detailed design guidelines for WTEG, we begin with carefully discussing the key issues for TEG toward wearable application. Finally, the specific strategies targeted WTEG that is classified into thermal design regarding extrinsic temperature difference (ΔT_ext), parasitic and TEG thermal resistance, mechanical design with emphasis on optimizing deformability at materials/device level beyond flexibility toward stretchability, as well as architecture design from two-dimension (2D) to 3D feature are comprehensively summarized, respectively. With these understandings, perspectives for the future development of WTEG are outlined. This review emphasizes issues and provides additional insight in advanced strategies for pushing TEG toward wearable application. The key issues clarified and the design roadmap summarized here arise from the goal of providing ideas for the concurrent optimization of the future WTEG, as well as realistically promoting the TEG toward wearable application.     

Autonomous Sensor System With Power Harvesting for Telemetric Temperature Measurements of Pipes

In this paper, an autonomous sensor system, with low-power electronics for radio-frequency (RF) communication, incorporating a thermoelectric energy-harvesting module for unattended operation is presented. A target application is proposed for temperature measurement of walled-in pipes. When the autonomous sensor is placed on the heat source, a thermoelectric module harvests energy, powering the autonomous sensor. In this condition, no external power source is necessary, the temperature measurement is performed, and the data are saved into a nonvolatile memory. When the external readout unit is active, the electromagnetic field is used to power the autonomous sensor system and to communicate the data. An experimental setup has been arranged and characterized by measuring the temperature along the pipe, the voltage that can be generated by thermoelectric generators, and the influence of different materials on RF communication. The temperature data of the heat source, which are collected by the autonomous sensor, are compared with that of a reference thermistor. The measurement results show good agreement between the two measured temperature data sets. The experimental data demonstrate that the autonomous system works correctly for a temperature gradient that is higher than 9degC, within a readout distance of a few centimeters. The presented autonomous sensor system can be effectively used for measurements into a close environment in which a temperature difference is present.     

Design,Performance, and Application of Thermoelectric Nanogenerators

Thermal energy harvesting from the ambient environment through thermoelectric nanogenerators (TEGs) is an ideal way to realize self‐powered operation of electronics, and even relieve the energy crisis and environmental degradation. As one of the most significant energy‐related technologies, TEGs have exhibited excellent thermoelectric performance and played an increasingly important role in harvesting and converting heat into electric energy, gradually becoming one of the hot research fields. Here, the development of TEGs including materials optimization, structural designs, and potential applications, even the opportunities, challenges, and the future development direction, is analyzed and summarized. Materials optimization and structural designs of flexibility for potential applications in wearable electronics are systematically discussed. With the development of flexible and wearable electronic equipment, flexible TEGs show increasingly great application prospects in artificial intelligence, self‐powered sensing systems, and other fields in the future.     

Preparation and characterization of the Ag2Se flexible films tuned by PVP for wearable thermoelectric generator

In recent years, the demand for wearable devices has promoted the research of flexible thermoelectric generators. Herein, this work reports a facile method to prepare the flexible Ag₂Se/polyvinyl pyrrolidone (PVP) composite films. The Ag₂Se nanorods are synthesized by the template method and then mixed with PVP solution to form the composite film optimized by the content of Ag₂Se. The maximum power factor of the film is 16.18?µW m^?1 K^?2 at 320?K, and the thermoelectric generator (TEG) has an output voltage and power of 5.49?mV and 55.57 nW at a temperature difference of 40?K, respectively. Moreover, the Ag₂Se/PVP film has good flexibility and can withstand multiple bending, the electrical conductivity reaching 89.8% and 76?% at 500 and 1000, respectively. PVP has an excellent protective capabilities effect so that the TE performance can remain stable in 40?days, and then the electrical conductivity only drops to 89?% of the initial value at 50?days. This work provides an effective method for preparing wearable thermoelectric devices, which can be extended to other composite materials.

     

Fabrication and characterization of thermoelectric thick film prepared from p-type bismuth telluride nanopowders

In this study, bismuth telluride (Bi2Te3)-based nanopowders with particle size ranging from 100 to 300 nm are prepared by high-energy ball milling. Then, the prepared nanopowders are homogeneously mixed with organic binders to form a paste; this paste is used as the raw material to prepare thick-film thermoelectric modules. The thick film prepared by screen printing followed by hot pressing of p-type pastes show reproducible thermoelectric properties, exhibiting an electrical resistivity of 2.0 m Omega cm and a Seebeck coefficient of 298 muVK-1. The prepared p-type Bi2Te3 thick film has a high power factor because its Seebeck coefficient is significantly higher than that of Bi2Te3 based-bulk materials. These results indicate that a thick film prepared from bismuth telluride nanopowders has potential for use as high-performance thermoelectric modules in practical applications such as power generation and cooling system in electronic devices.     

Flexible Thermoelectric Materials and Generators: Challenges and Innovations

The urgent need for ecofriendly, stable, long‐lifetime power sources is driving the booming market for miniaturized and integrated electronics, including wearable and medical implantable devices. Flexible thermoelectric materials and devices are receiving increasing attention, due to their capability to convert heat into electricity directly by conformably attaching them onto heat sources. Polymer‐based flexible thermoelectric materials are particularly fascinating because of their intrinsic flexibility, affordability, and low toxicity. There are other promising alternatives including inorganic‐based flexible thermoelectrics that have high energy‐conversion efficiency, large power output, and stability at relatively high temperature. Herein, the state‐of‐the‐art in the development of flexible thermoelectric materials and devices is summarized, including exploring the fundamentals behind the performance of flexible thermoelectric materials and devices by relating materials chemistry and physics to properties. By taking insights from carrier and phonon transport, the limitations of high‐performance flexible thermoelectric materials and the underlying mechanisms associated with each optimization strategy are highlighted. Finally, the remaining challenges in flexible thermoelectric materials are discussed in conclusion, and suggestions and a framework to guide future development are provided, which may pave the way for a bright future for flexible thermoelectric devices in the energy market.     

Conflict between internal combustion engine and thermoelectric generator during waste heat recovery in cars

It is shown that an internal combustion engine and a thermoelectric generator (TEG) arranged on the exhaust pipe of this engine come into the conflict of thermal machines that is related to using the same energy resource. The conflict grows with increasing useful electric power W _e of the TEG, which leads to the limitation of both the maximum TEG output power (W _e^max) and the possibility of waste heat recovery in cars.     

Graded carrier concentration materials for thermoelectric coolers

We have optimized the compositions of p-and n-type graded thermoelectric materials based on solid solutions between bismuth and antimony chalcogenides with high thermoelectric efficiency in the temperature range 100–400 K. Czochralski-grown graded single crystals have been used to fabricate graded legs 2.5 mm in height and 1.4 × 1.4 mm² in cross-sectional area for different stages of thermoelectric coolers. Pilot thermoelectric modules have been fabricated using homogeneous and graded legs, and the maximum temperature difference across the modules has been measured from 100 to 300 K. The efficiency of the modules with graded legs is shown to exceed that of the modules with homogeneous legs, especially at low temperatures.     

两段式结构赝三元材料热电模块的研究

在实验研究单段式结构赝三元材料的热电模块基础上,利用现有半导体致冷器生产工艺,依据热电材料的温度特性和冷热端工作温度,采用不同电阻率的赝三元材料,设计制作了两段式结构的热电模块．研究表明,当冷、热端工作温差为80K时,其输出功率和发电效率均比单段式结构的热电模块提高80％左右．     

Optimization of the thermoelectric figure of merit in the conducting polymer poly(3,4-ethylenedioxythiophene)

Thermoelectric generators (TEGs) transform a heat flow into electricity. Thermoelectric materials are being investigated for electricity production from waste heat (co-generation) and natural heat sources. For temperatures below 200 °C, the best commercially available inorganic semiconductors are bismuth telluride (Bi(2)Te(3))-based alloys, which possess a figure of merit ZT close to one. Most of the recently discovered thermoelectric materials with ZT>2 exhibit one common property, namely their low lattice thermal conductivities. Nevertheless, a high ZT value is not enough to create a viable technology platform for energy harvesting. To generate electricity from large volumes of warm fluids, heat exchangers must be functionalized with TEGs. This requires thermoelectric materials that are readily synthesized, air stable, environmentally friendly and solution processable to create patterns on large areas. Here we show that conducting polymers might be capable of meeting these demands. The accurate control of the oxidation level in poly(3,4-ethylenedioxythiophene) (PEDOT) combined with its low intrinsic thermal conductivity (λ=0.37 W m(-1) K(-1)) yields a ZT=0.25 at room temperature that approaches the values required for efficient devices.     

柔性热电发电器的关键工艺及其展望

热电发电器是固态能量收集器,以可靠和可再生的方式将热能转换成电能。过去几年的研究表明,人体的热量可以很好地被柔性热电发电器转换为电能并加以利用。与用于可穿戴设备的其他传统发电器相比,柔性热电发电器可利用低品位的热能发电且环境友好。柔性热电发电器将有可能为任何无线传感器节点提供足够的能量(通常功率要求小于毫瓦级)。本文综述了热电发电器的概况,重点介绍了制造柔性热电发电器的关键工艺,讨论了热电发电器的基本原理、效率、应用以及存在的一些问题。     

Thermoresistive and thermoelectric properties of coplanar cellulose-MWCNTs buckypaper

Thermoresistive sensors are based on the change in electrical resistance with temperature variation, are easily read, and have a simple design but require external power for their operation. Thermoelectric devices (TDs) based on the Seebeck effect directly convert heat into electrical power without any moving parts, generating voltages from the temperature difference established between the ends of a solid-state material. In recent years, several thermoresistors and TDs have been manufactured with conductive films based on carbon nanotubes (CNTs), i.e., with buckypaper (BP), because they provide lightweight, flexible, and sensitive devices. Nevertheless, the electrical resistance and thermoelectric properties of CNTs are affected when they are randomly assembled to form a BP. Then, this study investigated the thermoresistive and thermoelectric properties of a coplanar BP with an active area of 1.0 cm². Morphological characterization was performed by scanning electron microscopy and showed bundles of multiwalled CNTs agglomerated on the surface but also impregnated into cellulose fibers. BP-based thermoresistive sensor had a maximum sensitivity of ??10.05% at 322 K. Moreover, the thermoelectric configuration presented a maximum thermovoltage and thermoelectric power of ??1.2 mV and ??0.09 mV/K, respectively. These results suggest that this coplanar BP can be easily applied in thermal sensors and thermoelectric device concepts.

     

Thermoelectric cooling of microelectronic circuits and waste heat electrical power generation in a desktop personal computer

Thermoelectric cooling and micro-power generation from waste heat within a standard desktop computer has been demonstrated. A thermoelectric test system has been designed and constructed, with typical test results presented for thermoelectric cooling and micro-power generation when the computer is executing a number of different applications. A thermoelectric module, operating as a heat pump, can lower the operating temperature of the computer's microprocessor and graphics processor to temperatures below ambient conditions. A small amount of electrical power, typically in the micro-watt or milli-watt range, can be generated by a thermoelectric module attached to the outside of the computer's standard heat sink assembly, when a secondary heat sink is attached to the other side of the thermoelectric module. Maximum electrical power can be generated by the thermoelectric module when a water cooled heat sink is used as the secondary heat sink, as this produces the greatest temperature difference between both sides of the module.     

Multilayered carbon nanotube/polymer composite based thermoelectric fabrics

Thermoelectrics are materials capable of the solid-state conversion between thermal and electrical energy. Carbon nanotube/polymer composite thin films are known to exhibit thermoelectric effects, however, have a low figure of merit (ZT) of 0.02. In this work, we demonstrate individual composite films of multiwalled carbon nanotubes (MWNT)/polyvinylidene fluoride (PVDF) that are layered into multiple element modules that resemble a felt fabric. The thermoelectric voltage generated by these fabrics is the sum of contributions from each layer, resulting in increased power output. Since these fabrics have the potential to be cheaper, lighter, and more easily processed than the commonly used thermoelectric bismuth telluride, the overall performance of the fabric shows promise as a realistic alternative in a number of applications such as portable lightweight electronics.