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"Electric Generators"
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Flexible, Highly Thermally Conductive and Electrically Insulating Phase Change Materials for Advanced Thermal Management of 5G Base Stations and Thermoelectric Generators
HighlightsA core–sheath structured phase change nanocomposite (PCN) with aligned and overlapping interconnected BNNS networks were successfully fabricated.The PCN has an ultrahigh in-plane thermal conductivity (28.3 W m−1 K−1), excellent flexibility and high phase change enthalpy (101 J g−1).The PCN exhibits intensively potential applications in the thermal management of 5G base stations and thermoelectric generators.Thermal management has become a crucial problem for high-power-density equipment and devices. Phase change materials (PCMs) have great prospects in thermal management applications because of their large capacity of heat storage and isothermal behavior during phase transition. However, low intrinsic thermal conductivity, ease of leakage, and lack of flexibility severely limit their applications. Solving one of these problems often comes at the expense of other performance of the PCMs. In this work, we report core–sheath structured phase change nanocomposites (PCNs) with an aligned and interconnected boron nitride nanosheet network by combining coaxial electrospinning, electrostatic spraying, and hot-pressing. The advanced PCN films exhibit an ultrahigh thermal conductivity of 28.3 W m−1 K−1 at a low BNNS loading (i.e., 32 wt%), which thereby endows the PCNs with high enthalpy (> 101 J g−1), outstanding ductility (> 40%) and improved fire retardancy. Therefore, our core–sheath strategies successfully balance the trade-off between thermal conductivity, flexibility, and phase change enthalpy of PCMs. Further, the PCNs provide powerful cooling solutions on 5G base station chips and thermoelectric generators, displaying promising thermal management applications on high-power-density equipment and thermoelectric conversion devices.
Journal Article
Harness High-Temperature Thermal Energy via Elastic Thermoelectric Aerogels
HighlightsA thermoelectric aerogel of highly elastic, flame-retardant and high-temperature-resistant PEDOT:PSS/SWCNT composite is fabricated.The assembled thermoelectric generator generates a maximum output power of 400 μW at a temperature difference of 300 K.The self-powered wearable sensing glove can achieve wide-range temperature detection, complex hand motion recognition and high-temperature warning.The intelligent fire warning system enables highly sensitive and repeatable monitoring and alarm capabilities for high-temperature fire sources.Despite notable progress in thermoelectric (TE) materials and devices, developing TE aerogels with high-temperature resistance, superior TE performance and excellent elasticity to enable self-powered high-temperature monitoring/warning in industrial and wearable applications remains a great challenge. Herein, a highly elastic, flame-retardant and high-temperature-resistant TE aerogel, made of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/single-walled carbon nanotube (PEDOT:PSS/SWCNT) composites, has been fabricated, displaying attractive compression-induced power factor enhancement. The as-fabricated sensors with the aerogel can achieve accurately pressure stimuli detection and wide temperature range monitoring. Subsequently, a flexible TE generator is assembled, consisting of 25 aerogels connected in series, capable of delivering a maximum output power of 400 μW when subjected to a temperature difference of 300 K. This demonstrates its outstanding high-temperature heat harvesting capability and promising application prospects for real-time temperature monitoring on industrial high-temperature pipelines. Moreover, the designed self-powered wearable sensing glove can realize precise wide-range temperature detection, high-temperature warning and accurate recognition of human hand gestures. The aerogel-based intelligent wearable sensing system developed for firefighters demonstrates the desired self-powered and highly sensitive high-temperature fire warning capability. Benefitting from these desirable properties, the elastic and high-temperature-resistant aerogels present various promising applications including self-powered high-temperature monitoring, industrial overheat warning, waste heat energy recycling and even wearable healthcare.
Journal Article
Protection of Electromechanical Energy Converters in Distributed Generation Systems against Emergency Modes: Analysis of Protection Methods
The reliability of electromechanical energy converters is a key point for power supply systems with distributed generation, especially for remotely located ones. In this paper, the existing and advanced methods of protecting converters against emergency modes, including voltage unbalance, are analyzed. The physical principles underlying these methods and their application in various fields, including power engineering and control systems, are considered. Special attention is paid to factors causing voltage unbalance and its effect on equipment. The advantages and disadvantages of techniques for reactive power compensation, as well as methods for improving the efficiency of active and hybrid filters, are considered. Recommendations are given for optimizing protection systems used in distributed generation sources with regard to the interdisciplinary context and possible applications in related fields.
Journal Article
Thermal–electrical–structural performances of hot heat exchanger with different internal fins of thermoelectric generator for low power generation application
In this study, an electro-thermo-structural coupled numerical analysis is conducted to evaluate the thermal, electrical, and structural performances of a thermoelectric generator system. The hot heat exchangers with six different internal fin structures are compared in terms of temperature distribution, pressure drop, net power output, overall efficiency, and stress using the coupled numerical approach. Experiments are conducted on the heat exchanger with straight fins to validate the accuracy and reliability of the proposed coupled analysis. The hot gas outlet temperature, coolant outlet temperature, power output, and stress predicted using the coupled approach are validated within errors of 1.5, 6, 3, and 5.45%, respectively. Among the proposed heat exchanger designs, the heat exchanger with inclined fins and that with the combination of inclined and perpendicular fins exhibit higher net power outputs and overall efficiencies. The heat exchanger with the inclined fins and that with the combined fins exhibit overall efficiencies of 1.81 and 1.88% and net power outputs higher by 29 and 35%, respectively, than those of the heat exchanger with straight fins at the hot gas temperature of 600 °C. At the hot gas temperature 600 °C, the maximum stresses induced in the heat exchanger with the inclined fins and that with the combined fins are approximately 25.87 and 26.53 MPa, respectively, which are lower than the maximum allowable stress of 70 MPa.
Journal Article
Investigation of nanofluid cooling influence on energy performance of photovoltaic-thermoelectric module
The finned heat sink was equipped with a confined jet to create an effective way for cooling of photovoltaic (PV) system in current work. In the bottom of PV layers, a thermoelectric generator (TEG) has been utilized to produce more electrical power. To create a temperature difference, the heat sink has been located in the bottom of TEG. The fluid is mixture of water with hybrid nanomaterial (TiO
2
–CuO). For simulating, finite volume approach has been chosen and code has been verified based on previous publication. Influences of inlet velocity (
V
in
), radiation intensity (“
I
”) and inlet temperature (
T
in
) on electrical (
η
PV
) and thermal (
η
th
) efficiencies have been scrutinized. With increase in “
I
”, the values of
η
PV
and η
th
reduces about 5.94% and 14.3% while the amount of η
TEG
for “
I
” = 4200 W m
−2
is 3.47 times greater than that of “
I
” = 1200 W m
−2
. Greater value of
T
in
leads to lower values of
η
TEG
,
η
PV
and
η
th
around 28.2%, 2.5% and 13.72%. The amount of
η
th
and
η
TEG
intensifies about 1.13% and 2.76% with rise of
V
in
, respectively. Also, the increment effect of
V
in
on
η
PV
reduces around 24.8% in the existence of fins.
Journal Article
Photovoltaic–thermal (PV/T) technology: a comprehensive review on applications and its advancement
Over the most recent couple of decades, tremendous consideration is drawn towards photovoltaic–thermal systems because of their advantages over the solar thermal and PV applications. This paper intends to show different electrical and thermal aspects of photovoltaic–thermal systems and the researches in absorber design modification, development, and applications. From the previous review articles, it has been concluded that the heat energy exhausted from the PV module can be further utilized in different ways and helps in achieving better efficiency. Furthermore, the types of photovoltaic–thermal systems such as air collector, water collector, and combi system, coupling with heat pump and their application to buildings are also stated. This paper also discussed certain design aspects like modifications in the flow channel by adding fins, thin metallic sheets, roll-bond absorber, and porous media and the effect of these modifications on the hybrid system’s efficiency. Furthermore, the use of the latest technologies such as nanofluids, thermoelectric generators, and phase-change materials improves the overall system performance. The role of soft-computing techniques is forecasting the impact of various parameters on the photovoltaic–thermal system is also discussed.
Journal Article
Moisture-Electric–Moisture-Sensitive Heterostructure Triggered Proton Hopping for Quality-Enhancing Moist-Electric Generator
HighlightsAn efficient moist-electric generator with ultra-fast electric response to moisture is achieved by triggering Grotthuss protons hopping in the moisture-electric–moisture-sensitive heterostructure.The moist-electric generator produces a quick response (0.435 s), an unprecedented ultra-fast response rate of 972.4 mV s−1 to alternating moisture stimulation and stable output for 8 h.An obstructive sleep apnea hypoventilation syndrome diagnostic system based on a moist-electric generator was developed to monitor hypopnea and apnea in real time and successfully diagnose them with early warning.Moisture-enabled electricity (ME) is a method of converting the potential energy of water in the external environment into electrical energy through the interaction of functional materials with water molecules and can be directly applied to energy harvesting and signal expression. However, ME can be unreliable in numerous applications due to its sluggish response to moisture, thus sacrificing the value of fast energy harvesting and highly accurate information representation. Here, by constructing a moisture-electric–moisture-sensitive (ME-MS) heterostructure, we develop an efficient ME generator with ultra-fast electric response to moisture achieved by triggering Grotthuss protons hopping in the sensitized ZnO, which modulates the heterostructure built-in interfacial potential, enables quick response (0.435 s), an unprecedented ultra-fast response rate of 972.4 mV s−1, and a durable electrical signal output for 8 h without any attenuation. Our research provides an efficient way to generate electricity and important insight for a deeper understanding of the mechanisms of moisture-generated carrier migration in ME generator, which has a more comprehensive working scene and can serve as a typical model for human health monitoring and smart medical electronics design.
Journal Article
Increase in the efficiency of electricity production with a thermoelectric generator (TEG)
Currently used TEG modules have low efficiency of about 5%. The energy generated by the TEG module depends on the temperature difference between the module surfaces. Heat exchange between the heat source and the module surface takes place through the contact between two rough solid surfaces. This creates contact resistance. It can be reduced by using a substance filling the empty spaces between the contact surfaces and applying pressure. During the tests, the efficiency of electricity generation with a thermoelectric generator was measured (TEG) at various pressure forces. The tests were carried out at a pressure force of 250 N, 500 N, 750 N and 1000 N. The selected values of pressure do not exceed the limit value arising from the thermoelectric generator (TEG) design. A copper element constituting the heat source was heated in a furnace. Next, it was pressed at an adequate force to the generator, which was placed on a water cooler. The impact of conductive materials placed between the faces of the heat source and the TEG on the generation of electricity was examined. At low forces, the use of a thermal pad as an intermediary substance does not result in improved heat transfer in the heat source—TEG generator system. Better filling of voids is provided by thermally conductive paste due to its properties.
Journal Article
Stretchable and Flexible Painted Thermoelectric Generators on Japanese Paper Using Inks Dispersed with P- and N-Type Single-Walled Carbon Nanotubes
As power sources for Internet-of-Things sensors, thermoelectric generators must exhibit compactness, flexibility, and low manufacturing costs. Stretchable and flexible painted thermoelectric generators were fabricated on Japanese paper using inks with dispersed p- and n-type single-walled carbon nanotubes (SWCNTs). The p- and n-type SWCNT inks were dispersed using the anionic surfactant of sodium dodecylbenzene sulfonate and the cationic surfactant of dimethyldioctadecylammonium chloride, respectively. The bundle diameters of the p- and n-type SWCNT layers painted on Japanese paper differed significantly; however, the crystallinities of both types of layers were almost the same. The thermoelectric properties of both types of layers exhibited mostly the same values at 30 °C; however, the properties, particularly the electrical conductivity, of the n-type layer increased linearly, and of the p-type layer decreased as the temperature increased. The p- and n-type SWCNT inks were used to paint striped patterns on Japanese paper. By folding at the boundaries of the patterns, painted generators can shrink and expand, even on curved surfaces. The painted generator (length: 145 mm, height: 13 mm) exhibited an output voltage of 10.4 mV and a maximum power of 0.21 μW with a temperature difference of 64 K at 120 °C on the hot side.
Journal Article