Thermoelectric Microgenerators Research Articles

A hybrid energy harvesting approach for transmission lines based on triboelectric nanogenerator and micro thermoelectric generator

To effectively detect faults in transmission lines, monitoring the operating status of these lines is imperative. However, providing power to monitoring devices for transmission line status presents a significant challenge. In this research, a hybrid energy harvesting approach based on micro thermoelectric generator (MTEG) and triboelectric nanogenerator (TENG) is proposed, and a theoretical model for MTEG-TENG hybrid energy harvesting is established. This study develops an integrated energy harvesting prototype, which incorporates oscillating-TENG (O-TENGs), MTEGs, and a power management control unit. This prototype not only harvests energy from the vibrations of transmission lines but also converts the lines thermal energy into electricity. The Experiment results show that the maximum open-circuit voltages of O-TENG and MTEG reach 80.3 V and 1.094 V, respectively. Compared to a single MTEG energy harvesting device, the prototype of the MTEG-TENG hybrid energy harvesting device demonstrates a 5.36% improvement in energy harvesting and battery charging performance. Consequently, this approach achieves self-powered monitoring with excellent stability and lower manufacturing costs. It provides an efficient and durable power approach for transmission line status monitoring devices.

Self‐Powered Vibration Frequency Monitoring Device for the Grid Based on Triboelectric Nanogenerator and Micro Thermoelectric Generator

AbstractThe galloping of transmission lines (GTLs) has a significant impact on the development of smart grids. However, traditional vibration frequency monitoring devices for transmission lines suffer from issues such as low measurement accuracy, high environmental requirements, and the inability to achieve self‐powering. A self‐powered vibration frequency monitoring method is proposed based on frequency‐sensing triboelectric nanogenerator (F‐TENG) and micro thermoelectric generators (MTEG). Models for vibration frequency sensing based on F‐TENG and energy capture based on MTEG are established. A flexible self‐powered sensing prototype, integrating F‐TENG, MTEG, and a Signal processing and Energy harvesting Circuit (SEC), is fabricated. Additionally, an innovative solvothermal method for the preparation of MTEG materials is presented, resulting in Bi2Te3‐based thermoelectric materials with significantly high thermoelectric conversion performance. Experimental results demonstrate that within the range of 0.1–5.1 Hz, F‐TENG can precisely perceive the frequency of GTLs, with a maximum error of 1.274%. MTEG achieves a maximal open‐circuit voltage of 3.282 V. Finally, the SEC unit is designed to couple the outputs of F‐TENG and MTEG for frequency calculation and wireless transmission to a microcontroller. This device provides an efficient solution for monitoring the frequency of GTLs and offers robust support for the stability of the smart grid.

Planar Thermoelectric Microgenerators in Application to Power RFID Tags.

This paper presents an innovative approach to the integration of thermoelectric microgenerators (μTEGs) based on thick-film thermopiles of planar constantan-silver (CuNi-Ag) and calcium cobaltite oxide-silver (Ca3Co4O9-Ag) thick-film thermopiles with radio frequency identification (RFID) technology. The goal was to consider using the TEG for an active or semi-passive RFID tag. The proposed implementation would allow the communication distance to be increased or even operated without changing batteries. This article discusses the principles of planar thermoelectric microgenerators (μTEGs), focusing on their ability to convert the temperature difference into electrical energy. The concept of integration with active or semi-passive tags is presented, as well as the results of energy efficiency tests, considering various environmental conditions. On the basis of the measurements, the parameters of thermopiles consisting of more thermocouples were simulated to provide the required voltage and power for cooperation with RFID tags. The conclusions of the research indicate promising prospects for the integration of planar thermoelectric microgenerators with RFID technology, opening the way to more sustainable and efficient monitoring and identification systems. Our work provides the theoretical basis and practical experimental data for the further development and implementation of this innovative technology.

Overall numerical simulation of chemical-thermal-electric conversion for an all-in-one thermoelectric generator based on micro scale combustion

Micro combustion-based power systems have garnered significant attention owing to their high energy density and portability. This work presents a numerical simulation process for an integrated thermoelectric generator based on micro-combustion, which can track the chemical-thermal-electro energy conversion. The combustion performance, thermal characteristics and energy conversion for the micro-thermoelectric generator (MTEG) system are investigated. A range of equivalence ratios and Reynolds numbers (Re) is examined to provide a detailed analysis. With the increment of equivalence ratio (φ), both the energy output and the open-circuit voltage of the system significantly increase. At high φ, the voltage and energy output exhibit a growth tendency when the Re number increases. Conversely, at low φ, the voltage and energy output decrease at higher Re number. The maximum voltage of 0.264 V is achieved when φ = 1.0 and Re = 1500, while the system delivers an energy output of 1.87 W.

Self-Powered Temperature Electronic Skin Based on Island-Bridge Structure and Bi-Te Micro-Thermoelectric Generator for Distributed Mini-Region Sensing.

Thermoelectric (TE) effect based temperature sensor can accurately convert temperature signal into voltage without external power supply, which have great application prospects in self-powered temperature electronic skin (STES). But the fabrication of stretchable and distributed STES still remains a challenge. Here, a novel STES design strategy is proposed by combining flexible island-bridge structure with BiTe-based micro-thermoelectric generator (µ-TEG). Furthermore, a 4×4 vertical temperature sensor array with good stretchability and distributed sensing property has been fabricated for the first time. The interfacial chemical bonds located between the rigid islands (µ-TEG) and the flexible substrate (polydimethylsiloxane, PDMS) endow the STES with excellent stretchability, and its sensing performance remains unchanged under 30% strain (the maximum strain of human skin). Moreover, the STES sensing unit possesses high sensitivity (729 µV K-1 ), rapid response time (0.157 s), and high spatial resolution (2.75×2.75 mm2 ). As a proof of concept, this work demonstrates the application of the STES in the detection of mini-region heat sources in various scenarios including noncontact spatial temperature responsing, intelligent robotic thermosensing, and wearable temperature sensing. Such an inspiring design strategy is expected to provide guidance for the design and fabrication of wearable self-powered temperature sensors.

Composite energy acquisition of thermal and kinetic energy from cetaceans based on micro thermoelectric generator and triboelectric nanogenerator

Mobile marine environment sensor plays an essential role in the area of assessment of marine environments. However, the power supply duration of the mobile devices is facing significant challenges that need to be addressed. In this study, a self-powered systemformarine environmental sensors basedoncetaceans (SMES) is developed using a micro thermoelectric generator (MTEG) and a triboelectric nanogenerator (TENG). The SMES is designed for the mobile marine environment monitoring device with cetaceans as the carrier. The system can convert the thermal and kinetic energy of cetaceans into electrical energy and store it in a battery. A theoretical model is established using the correlation involving the frequency and amplitude of cetaceans and the output voltage of MTEG. The influence of the dynamic and kinematic characteristics of cetaceans on the performance of MTEG and TENG is studied. The UOC,max of Fishtailing-TENG is 5.85 V and the UOC,max of MTEG is 1.821 V. Therefore, the system enables the marine environment monitoring device to obtain accurate and valuable scientific data on the marine environment in a wider range of marine areas.

High Thermoelectric Performance of Non-Stoichiometric and Oriented GeTe Thin Films.

The increasing demand for micro-thermoelectric coolers and generators promotes the research on thermoelectric (TE) thin films. As a promising medium-temperature TE material, GeTe has attracted wide attention recently. However, the thermoelectric performance of thin-film GeTe remains inferior. Herein, oriented GeTe films with excessive Ge are obtained by magnetron co-sputtering technique, which can not only reduce the carrier concentration but also increase the carrier mobility, maintaining the high electrical conductivity of GeTe. Furthermore, higher structural symmetry and grain boundary scattering enhance the Seebeck coefficient of oriented GeTe films. As a result, the power factor (PF) value can reach as high as 2848 µW m-1 K-2 at room temperature and increase to 5263 µW m-1 K-2 at 600 K. Furthermore, a TE device with the Ge-rich GeTe thin film is fabricated and the maximum output power density (power per unit area) reaches 0.3W cm-2 at ΔT = 250 K. This work demonstrates that the stoichiometry and orientation modulations are effective strategies to improve the thermoelectric performance of GeTe thin films.

A Novel Thermal Tactile Sensor Based on Micro Thermoelectric Generator for Underwater Flow Direction Perception

Underwater vehicles can operate independently in the exploitation of marine resources. However, water flow disturbance is one of the challenges underwater vehicles must face. The underwater flow direction sensing method is a feasible way to overcome the challenges but faces difficulties such as integrating the existing sensors with underwater vehicles and high-cost maintenance fees. In this research, an underwater flow direction sensing method based on the thermal tactility of the micro thermoelectric generator (MTEG) is proposed, with the theoretical model established. To verify the model, a flow direction sensing prototype is fabricated to carry out experiments under three typical working conditions. The three typical flow direction conditions are: condition No. 1, in which the flow direction is parallel to the x-axis; condition No. 2, in which the flow direction is at an angle of 45° to the x-axis; and condition No. 3, which is a variable flow direction condition based on condition No. 1 and condition No. 2. According to the experimental data, the variations and orders of the prototype output voltages under three conditions fit the theoretical model, which means the prototype can identify the flow direction of three conditions. Besides, experimental data show that in the flow velocity range of 0~5 m/s and the flow direction variation range of 0~90°, the prototype can accurately identify the flow direction in 0~2 s. The first time utilizing MTEG on underwater flow direction perception, the underwater flow direction sensing method proposed in this research is cheaper and easier to be applied on the underwater vehicles than traditional underwater flow direction sensing methods, which means it has great application prospects in underwater vehicles. Besides, the MTEG can utilize the waste heat of the underwater vehicle battery as the energy source to achieve self-powered work, which greatly enhances its practical value.

Optimal Design of Wearable Micro Thermoelectric Generator Working in a Height-Confined Space

With the increasing development of self-powered wearable electronic devices, there is a growing interest in thermoelectric generators (TEGs). To achieve more comprehensive and reliable functionality of wearable devices, improving the power generation performance of thermoelectric devices will be the key. It has been shown that integrating a heat sink at the cold end of the TEG increases the effective temperature difference and, thus, maximizes the power output of the thermoelectric device. However, the space left for the power supply is often limited. How to optimize the integrated system of micro-thermoelectric generators and heat sinks in a height-confined space has become the key. In this study, we have established a corresponding model using a numerical calculation method, systematically studied the influence of TEG geometric size on the number of fins and fin height, and determined the optimal number of fins for the highest equivalent convective heat transfer coefficient corresponding to different fin heights. We also conducted the co-design of TEG and fin topological structure to study the effects of the ratio of leg height to fin height (l/H), the width of legs (w), and the number of thermoelectric leg pairs (N) on the maximum output power density per unit area (Pm1) and the maximum output power density per unit mass (Pm2) of the device. When N = 16, w = 0.3 mm, l/H = 2.5 (that is, l = 3.57 mm, H = 1.43 mm), and Pm1 reaches the maximum value of 30.5 μW/cm2; When N = 2, l/H = 0.25 and w = 0.3 mm, and Pm2 reaches a maximum value of 5.12 mW/g. The measured values of the open-circuit voltages of fabricated micro-TEGs with different thermoelectric leg heights (l = 0.49 mm, l = 1.38 mm, and l = 1.88 mm) are basically consistent with the simulated values. When N = 2, l = 0.49 mm, H = 3.74 mm, and w = 0.85 mm, and Pm2 reaches 0.44 mW/g. The results provide insights into the optimal design of wearable micro thermoelectric generator working in a height-confined space and highlight the importance of co-designing TEGs and fin topological structures for optimizing their performance.

Superior Thermoelectric Performance of SiGe Nanowires Epitaxially Integrated into Thermal Micro-Harvesters.

Semiconductor nanowires have demonstrated fascinating properties with applications in a wide range of fields, including energy and information technologies. Particularly, increasing attention has focused on SiGe nanowires for applications in a thermoelectric generation. In this work, a bottom-up vapour-liquid-solid chemical vapour Deposition methodology is employed to integrate heavily boron-doped SiGe nanowires on thermoelectric generators. Thermoelectrical properties -, i.e., electrical and thermal conductivities and Seebeck coefficient - of grown nanowires are fully characterized at temperatures ranging from 300 to 600 K, allowing the complete determination of the Figure-of-merit, zT, with obtained values of 0.4 at 600 K for optimally doped nanowires. A correlation between doping level, thermoelectric performance, and elemental distribution is established employing advanced elemental mapping (synchrotron-based nano-X-ray fluorescence). Moreover, the operation of p-doped SiGe NWs integrated into silicon micromachined thermoelectrical generators is shown over standalone and series- and parallel-connected arrays. Maximum open circuit voltage of 13.8mV and power output as high as 15.6 µW cm-2 are reached in series and parallel configurations, respectively, operating upon thermal gradients generated with hot sources at 200 °C and air flows of 1.5 m s-1 . These results pave the way for direct application of SiGe nanowire-based micro-thermoelectric generators in the field of the Internet of Things.

Investigation of CH4 and porous media addition on thermal and working performance in premixed H2/air combustion for micro thermophotovoltaic

Primary obstacles to the development of micro-thermoelectric generators are the gigantic heat loss ratio and flame instability. Premixed H2/air combustion in the micro-planar combustor with porous media (PM) and CH4 blended is experimentally and numerically conducted to boost the generator working performance. Effects of porosities, PM length and CH4 blending on combustion characteristics and thermal performance are detailedly studied at various operating conditions. Results indicate that flame stability is enhanced in PM, and the burner radiation temperature is also significantly boosted because of heat recirculation and heat transmission from flame. PM porosity ε = 0.9 balances the effects of solid skeleton on flame propagation and thermal improvement, which is conducive to flame stabilization. The coupling of PM setting and 25 % CH4 blending strongly improves the combustor thermal performance via altering the flame location and enhancing heat transmission. It also ameliorates the uniformity of radiation wall. Moreover, prolonging porous matrix has a positive effect on the improvement of thermal performance under a high chemical energy input. Particularly, combustor #C-Ls13 obtains an electrical output of 2.5 W and a system efficiency of 2.1 % at 25 %CH4-75 %H2 fueled combustion.

Unlocking microwatt power: enhanced performance of Fe–V–Al thin films in thermoelectric microgenerators

Microwatt power output obtained in thermoelectric microgenerators based on cost-effective and non-toxic Fe–V–Al thin films deposited by a DC magnetron co-sputtering process.

Metal-based folded-thermopile for 2.5D micro-thermoelectric generators

Metal-based folded-thermopile for 2.5D micro-thermoelectric generators

Underwater hybrid energy harvesting based on TENG-MTEG for self-powered marine mammal condition monitoring system

To effectively protect endangered marine mammals, one needs to collect and monitor their biological data and living environment information. This is however a great challenge for the endurance of marine mammal condition monitoring devices. The present study is to propose a self-powered marine mammal condition monitoring system, based on the hybrid energy harvesting mode of triboelectric nanogenerator (TENG) and micro thermoelectric generator (MTEG), to address the challenge. This system not only can obtain energy from the movement of marine mammals but also harvest energy from the temperature difference between the body surface and the ambient. The system fittingly integrates oscillating-TENG (O-TENG), MTEG, and power management unit. Note that O-TENG and MTEG can produce the maximal open circuit voltages of 5.85 V and 1.821 V, respectively. The TENG + MTEG hybrid energy harvesting device can improve the energy collection and battery charging performance by 4.93% compared with the MTEG single energy acquisition device. Hence, it can prolong the service life of the device, achieve an excellent stability, and is easy to manufacture. Eventually, the system can provide an effective and long-term endurance strategy for the condition monitoring device of endangered marine mammals.

Design and Application of a New Self-Powered Sensing Device Based on MTEG and FTENG

In recent years, the increasing demand for the establishment of smart ocean systems has promoted the exploration of self-powered sensing devices. However, a traditional battery has the disadvantages of limited energy storage and frequent replacement. These disadvantages make it difficult to power electronic equipment for a long time, which has become a major obstacle to constructing smart ocean systems. To meet these challenges, a new self-powered sensing device based on a microthermoelectric generator (MTEG) and flag-type triboelectric nanogenerator (FTENG) is proposed. The prototype is a hybrid energy-harvesting system. Through this prototype, solar and wind energy can be harvested simultaneously, and it can be employed to continuously power environmental sensors. In addition, the performance of the prototype was tested. Under the condition of a hot end at 70°C and a wind speed of 10 m/s, the prototype can charge the supercapacitor to 5.5 V in 10 min. Additionally, the prototype can sense and transmit wind speed and direction data. This research provides a new way for the establishment of smart ocean systems.

Fabrication and simulation study for vertical micro-TEGs based on printed circuit board manufacturing processes

The development of fabrication procedures for micro-thermoelectric generators (µTEGs) based on low-cost fabrication technologies, appropriate for mass production is discussed and demonstrated in this study. Simulations were carried out, two manufacturing processes were tested, and device performance is compared to simulation results for vertical µTEGs. The substrate for this device is a printed circuit board, and the thermoelectric materials are self-developed Bi0.5Sb1.5Te3 (p-type) and Bi2Te2.7Se0.3 (n-type) pastes. A square µTEG (15 mm × 15 mm × 500 µm) with eight thermocouples (TCs) was fabricated. The characterization of the fabricated 8-TC-µTEG was carried out and a power output of 1.23 µW was obtained for the fabricated 8-TC-µTEG. The measurement results of this 8-TC-µTEG closely match simulation results as well. Moreover, a novel vertical electrical contact resistance measurement setup is designed and implemented into the final evaluation of µTEG production to have a more accurate assessment. The simulation study is also applied for the designed electrical contact resistance measurement setup. As a result, the contact resistivity of Bi2Te3/Cu was calculated as 5.65 × 10−4 Ωcm2.

Process Considerations for selective doping of poly-Si thin films with spin-on dopants and nickel silicide formation for planar thermoelectric devices

The formation of highly doped p-type (boron-doped) and n-type (phosphorus-doped) poly-Si thin films with spin-on dopants on the same wafer poses unique challenges. This work evaluates the pros and cons of different approaches to dopant diffusion, residue removal, and diffusion mask selection when working with spin-on dopants. The experiments have been carried out to optimize the formation of highly doped poly-Si thin films that will form the active layers of a micro-thermoelectric generator (μ-TEG). Building upon previous work on residue removal methods, we report that the residue formation is also dependent on the oxide-silicon surface with a PECVD oxide-Si interface not requiring a post-dopant diffusion nitric acid treatment to achieve a hydrophobic surface. Furthermore, comparing the direct dispense and proximity diffusion methods verifies the existing reports of enhanced diffusion in the latter case. Besides, we observe that doping first with Boron is more conducive than doping first with phosphorus to reduce sheet resistance. We also optimize the contact formation with Ti/Ni thin films and report the mean contact resistivity. Notably, contact annealing precludes the nitric acid treatment requirement even if the surface is hydrophilic after removing dopant residue. Additionally, the sequence of silicidation is observed to be dependent on the doping of the underlying areas.

Micro-heat sink based on silicon nanowires formed by metal-assisted chemical etching for heat dissipation enhancement to improve performance of micro-thermoelectric generator

This work demonstrates the micro-heat sink based on silicon nanowires formed by metal-assisted chemical etching (MACE) for heat dissipation enhancement to improve the performance of the micro-thermoelectric generator (µ-TEG). The heat dissipation through the micro-heat sink is enhanced by increasing the surface-to-volume ratio, which can be achieved by combining deep reactive ion etching (RIE) and MACE. Silicon nanowires with a diameter of 100 nm and a height of 9 µm are successfully formed in both horizontal and vertical surface directions. The micro-heat sink effectiveness is 8.3 times better than that of without employing the micro-heat sink. In addition, the performance of the µ-TEG has been significantly enhanced by utilizing the micro-heat sink. The maximum output power of the µ-TEG with and without the micro-heat sink are 93 µW and 18.5 µW, respectively, under the same evaluation conditions. The findings in this work may be useful not only for the µ-TEG, but also other applications such as micro-supercapacitors, micro-sensors, chemical analysis, and biological processes, which require a large surface-to-volume ratio.

Iso efficiency in nanostructured thermoelectric materials

A study is carried out for the efficiency of segmented thermoelectric microgenerators (μSTEGs). The study includes a) n-type and p-type double or triple segmentation and b) geometry shape factor of the thermoelements. The temperature-dependent thermoelectric properties of nanostructured materials are determined from experimental data. In addition, the impact of internal resistance, as a function of the thermoelement-geometric shape factor, on the efficiency surfaces of the μSTEGs is studied based on non-equilibrium thermodynamics. Results show that the efficiency surfaces of different μSTEGs intersect under different working conditions. The curve formed by the intersection points of the efficiency surfaces of the two thermoelectric systems is called the iso-efficiency curve. Thus, segmented thermoelectric systems with different efficiencies can reach a common efficiency for a given segmentation and geometric shape form of their thermoelements under different working conditions. The common efficiency that reaches (corresponds to) these thermoelectric systems is called Iso efficiency. The iso efficiency is reached due to the n-type and p-type material segmentation and geometric shape, which affect each thermoelement’s internal resistance. Furthermore, the efficiency of a μSTEG system can be improved due to the combination of effects such as the relationship between load resistance and internal resistance when it is affected by the geometric shape, temperature difference, and segmentation. Our results allow determinate the new iso efficiency parameters with a good selection of the thermodynamic, electrical, and geometric parameters and establish guidance for other materials engineering investigations, to improve the efficiency of μSTEGs.

Influence of Thermoelectric Properties and Parasitic Effects on the Electrical Power of Thermoelectric Micro-Generators

Heat recovery systems based on thermoelectric micro-generators (µ-TEGs) can play a significant role in the development of wireless, energetically autonomous electronics. However, to date, the power density recovered for low temperature differences using µ-TEGs is limited to a few micro-watts or less, which is still insufficient to power a wide-range of wireless devices. To develop more efficient µ-TEGs, material, device and system requirements must be considered simultaneously. In this study, an innovative design of an in-plane µ-TEG integrating bismuth telluride forming sinusoidal-shaped trenches is reported. Using 3D numerical modelling, the influence of boundary conditions, parasitic effects (electrical and thermal contact resistances), and transport properties of thermoelectric materials on the output power of these µ-TEGs are investigated in detail for a small temperature difference of 5 K between the hot and cold sources. Compared to wavy-shaped trenches, this novel shape enables enhancing the output power. The results show that either the thermal conductivity or the Seebeck coefficient of the active n- and p-type semiconductors is the key parameter that should be minimized or maximized, depending on the magnitude of the parasitic effects.