High Power Factor Research Articles

Wide-temperature-range thermoelectric n-type Mg3(Sb,Bi)2 with high average and peak zT values

Mg3(Sb,Bi)2 is a promising thermoelectric material suited for electronic cooling, but there is still room to optimize its low-temperature performance. This work realizes >200% enhancement in room-temperature zT by incorporating metallic inclusions (Nb or Ta) into the Mg3(Sb,Bi)2-based matrix. The electrical conductivity is boosted in the range of 300–450 K, whereas the corresponding Seebeck coefficients remain unchanged, leading to an exceptionally high room-temperature power factor >30 μW cm−1 K−2; such an unusual effect originates mainly from the modified interfacial barriers. The reduced interfacial barriers are conducive to carrier transport at low and high temperatures. Furthermore, benefiting from the reduced lattice thermal conductivity, a record-high average zT > 1.5 and a maximum zT of 2.04 at 798 K are achieved, resulting in a high thermoelectric conversion efficiency of 15%. This work demonstrates an efficient nanocomposite strategy to enhance the wide-temperature-range thermoelectric performance of n-type Mg3(Sb,Bi)2, broadening their potential for practical applications.

A Novel Integrated Electronic Lighting Driver Circuit for Supplying an LED Projection Lamp with High Power Factor and Soft Switching Characteristics

The traditional light source of projection lamps adopts a halogen lamp, which has the advantages of high brightness, but its luminous efficiency is not good and consumes energy. A light-emitting diode (LED) has the characteristics of high luminous efficiency and energy savings and can be used as a new light source for projection lamps. The conventional two-stage electronic lighting driver circuit for supplying an LED projection lamp is composed of an AC-DC converter with power factor correction (PFC) as the first stage and a DC-DC converter for providing rated lamp voltage and current as the second stage. The conventional LED projection lamp driver circuit has more circuit components, a higher cost and limited efficiency. Therefore, this paper proposes a novel electronic lighting driver circuit for supplying an LED projection lamp with PFC function, which integrates a modified stacked dual boost converter and a half-bridge LLC resonant converter into a single-stage power-conversion circuit. The inductor inside the modified stacked boost converter is designed to operate at discontinuous conduction mode (DCM) for the driver circuit achieving PFC. Wide bandgap semiconductor devices silicon carbide (SiC)-based Schottky diodes are utilized to reduce power diode losses, and soft switching is implemented in the proposed LED projector lamp driver circuit to reduce the switching losses of the power switches and thus improve circuit efficiency. This paper has completed a single-stage prototype driver circuit for an LED projection lamp with PFC function, and the prototype circuit has a high power factor (PF > 0.98), low input current total-harmonic-distortion (THD < 6%) and high efficiency (>89%) in the case of an AC input power supply with an RMS value of 110 volts, and both power switches have the characteristics of soft switching.

PI Controller Based Bridgeless Isolated Cuk Converter for Electric Vehicle Battery

This work proposes a cruise control idea based on a proportionate and integral (PI) direct torque control applied to an electric vehicle’s (EV) propulsion system. This study designs and develops a bridgeless isolated Cuk converter-based electric vehicle (EV) battery charger with a high power factor and enhanced efficiency. The study also goes into simulation, control design, and simulation, which results in a numerically emulator made up of detailed models of the key parts: transmission structure, inductive motor, electricity systems, system of control, and car dynamics. The simulation was created in MATLAB/Simulink and will enable for the assessment of an EV’s energy usage in various configurations. The simulation results demonstrate the effectiveness of the planned control.

Large Mobility Enables Higher Thermoelectric Cooling and Power Generation Performance in n-type AgPb18+xSbTe20 Crystals.

The room-temperature thermoelectric performance of materials underpins their thermoelectric cooling ability. Carrier mobility plays a significant role in the electronic transport property of materials, especially near room temperature, which can be optimized by proper composition control and growing crystals. Here, we grow Pb-compensated AgPb18+xSbTe20 crystals using a vertical Bridgman method. A large weighted mobility of ∼410 cm2 V-1 s-1 is achieved in the AgPb18.4SbTe20 crystal, which is almost 4 times higher than that of the polycrystalline counterpart due to the elimination of grain boundaries and Ag-rich dislocations verified by atom probe tomography, highlighting the significant benefit of growing crystals for low-temperature thermoelectrics. Due to the largely promoted weighted mobility, we achieve a high power factor of ∼37.8 μW cm-1 K-2 and a large figure of merit ZT of ∼0.6 in AgPb18.4SbTe20 crystal at 303 K. We further designed a 7-pair thermoelectric module using this n-type crystal and a commercial p-type (Bi, Sb)2Te3-based material. As a result, a high cooling temperature difference (ΔT) of ∼42.7 K and a power generation efficiency of ∼3.7% are achieved, revealing promising thermoelectric applications for PbTe-based materials near room temperature.

Medium-entropy (Sr1/3Ba1/3Ca1/3)TiO3 perovskite oxide for thermoelectric applications

A novel ternary medium-entropy perovskite oxide, (Sr1/3Ba1/3Ca1/3)TiO3, is reported for thermoelectric applications; it was synthesized via solid-state reaction and graphite burial sintering. The formation and stability of the single-phase structure were evaluated using thermodynamic calculations and the Goldschmidt’s tolerance factor. The material was found to have a single-phase cubic perovskite structure with a homogeneous distribution of all elements. The medium entropy generates moderate carrier mobility, while the band flattening yields high Seebeck coefficient, resulting in a high power factor of 378.8 μW·m−1·K−2 at 773 K. The enhanced multi-phonon scattering derived from the medium entropy, oxygen vacancies, and porous structure significantly reduced the lattice thermal conductivity, with a lowest value of 1.90 W·m−1·K−1 at 773 K. As a result, a ZTmax of 0.13 was attained at 773 K, which outperforms that of high-entropy SrTiO3-based oxides. This work provides a new direction to obtain high-performance thermoelectric materials through medium-entropy composition design.

Optimum design and research of switched reluctance motor for electric vehicle based on Motor-Cad

With the development of the economy and the deepening of the energy crisis, electric vehicle has now become the hotspot of the global automotive industry. Therefore, as the key part of electric vehicle, the design and research of drive motor has become the focus of attention of engineers and technicians. Because of its simple structure, easy maintenance, high output power, high output torque, wide speed range, and high efficiency, the switched reluctance motor (SRM) has been one of the first choice of electric vehicle driving motors. According to the performance requirements of electric vehicle driving motors, a 3-phase 24/16 pole with rated power of 30 kW switched reluctance motor (SRM) for electric vehicle has been designed in this paper by using Motor-Cad which can be used to optimize the parameters of motor to make the overall structure of the motor more reasonable. In order to reduce the torque ripple of switched reluctance motor, appropriate stator polar arc and rotor polar arc design are used in the motor. To realize the speed control of switched reluctance motor in a wide range, PWM control mode is adopted in this paper, which has fast motor response speed, high power factor and excellent dynamic and static performance. The simulation results show that the performance indexes of the switched reluctance motor meet the design requirements completely.

A New Hybrid Concentrated-Winding Concept With Improved Power Factor for Permanent Magnet Vernier Machine

This paper investigates a high power-factor permanent magnet vernier machine (PMVM) equipped with low-coupling hybrid concentrated-winding (CW). The proposed hybrid-CW, carrying both star- and delta-winding sets, exhibits a good filtering property to both sub- and super-order harmonics. Through the meticulous design of the short coil pitch, the ratio of inductance to magnet flux linkage is decreased, leading to a great improvement in power factor. The proposed low-coupling winding design contributes to further power factor improvement by reducing the inductance while retaining the magnet flux linkage. It is revealed that the mutual coupling between different coils of single phase and that between different windings of three phases are suppressed significantly in the hybrid-CW, thus leading to high power factor and potentially high fault tolerance. Finite element results show that the proposed hybrid-CW PMVM exhibits a significantly improved power factor up to 0.96 from 0.83 and 0.75, as compared with two counterpart PMVMs with open-slot and split-tooth structures, respectively. Benefiting from the magnetic gearing effect, the proposed PMVM has a promising active torque density of 40 Nm/L. Taking end-winding volume into consideration, the proposed PMVM exhibits an actual torque density of 21.98 Nm/L, which is 22.52% and 52.43% higher than the investigated open-slot and split-tooth counterpart PMVMs. Finally, a prototype is fabricated and tested to validate the high-power-factor and high-torque-density features of the proposed hybrid-CW PMVM.

A Cost Effective High Power Factor General Purpose Battery Charger for Electric Two-Wheelers and Three Wheelers

A Cost Effective High Power Factor General Purpose Battery Charger for Electric Two-Wheelers and Three Wheelers

Solution‐Doped Donor–Acceptor Copolymers Based on Diketopyrrolopyrrole and 3, 3′‐Bis (2‐(2‐(2‐Methoxyethoxy) Ethoxy) ethoxy)‐2, 2′‐Bithiophene Exhibiting Outstanding Thermoelectric Power Factors with p‐Dopants

AbstractThe design of polymeric semiconductors exhibiting high electrical conductivity (σ) and thermoelectric power factor (PF) will be vital for flexible large‐area electronics. In this work, four polymers based on diketopyrrolopyrrole (DPP), 2,3‐dihydrothieno[3,4‐b][1,4]dioxine (EDOT), thieno[3,2‐b]thiophene (TT), and 3, 3′‐bis (2‐(2‐(2‐methoxyethoxy) ethoxy) ethoxy)‐2, 2′‐bithiophene (MEET) are investigated as side‐chains, with the MEET polymers newly synthesized for this study. These polymers are systematically doped with tetrafluorotetracyanoquinodimethane ( F4TCNQ), CF3SO3H, and the synthesized dopant Cp(CN)3‐(COOMe)3, differing in geometry and electron affinity. The DPP‐EDOT‐based polymer containing MEET as side‐chains exhibits the highest conductivity (σ) ≈700 S cm−1 in this series with the acidic dopant (CF3SO3H). This polymer also shows the lowest oxidation potential by cyclic voltammetry (CV), the strongest intermolecular interactions evidenced by differential scanning calorimetry (DSC), and has the most oxygen‐based functionality for possible hydrogen bonding and ionic screening. Other polymers exhibit high σ ≈300–500 S cm−1 and power factor up to 300 µW m−1 K−2. The mechanism of conductivity is predominantly electronic, as validated by time‐dependent conductance studies and transient thermo voltage monitoring over time, including for those doped with the acid. These materials maintain significant thermal stability and air stability over ≈6 weeks. Density functional theory calculations reveal molecular geometries and inform about frontier energy levels. Raman spectroscopy, in conjunction with scanning electron microscopy (SEM‐EDS) and x‐ray diffraction, provides insight into the solid‐state microstructure and degree of phase separation of the doped polymer films. Infrared spectroscopy enables this study to further quantify the degree of charge transfer from polymer to dopant.

A Hybrid Quasi-Single-Stage AC-DC Converter with Low Twice-Line-Frequency Output Voltage Ripple

Power factor correction (PFC) converters have been frequently employed in various switching power supply devices to reduce input current harmonics. However, the PFC converter suffers from an obvious twice-line-frequency output voltage ripple due to the instantaneous power imbalance between constant output power and variable input power. Suppression of twice-line-frequency ripple usually can be realized by the post-stage DC-DC converter of the two-stage cascade PFC converter; however, the two-stage cascade PFC structure is challenging to realize high efficiency since the energy is transferred twice. To achieve high power factor, high efficiency, and low twice-line-frequency ripple, a hybrid quasi-single-stage (QSS) AC-DC converter is presented in this paper, which consists of a dual output hybrid Boost/Flyback PFC converter and a Buck ripple compensation circuit (RCC). The fundamental principles of the proposed converter and the critical conditions of operation mode transition are discussed in the paper. To confirm that the twice-line-frequency ripple is effectively suppressed, the small signal model of Buck RCC is built and analyzed. Moreover, the main characteristics, including operation mode transition angle, input current, power factor, and switching frequency of the proposed hybrid QSS AC-DC converter, are analyzed. By building a 120 W experimental prototype to validate the feasibility of the proposed hybrid QSS AC-DC converter, the experimental results show that the proposed converter can realize PFC function with high efficiency and extremely low twice-line-frequency output voltage ripple.

Excellent thermoelectric transport performance in semiconducting hhk-silicene

Unlike graphene-like silicene, a recently reported hybrid honeycomb-kagome (hhk) silicene is a semiconductor instead of a gapless Dirac-cone, which has great potential applications in semiconducting devices. Here, using first-principles calculations combined with Boltzmann transport equation, we find that hhk-silicene has high Seebeck coefficient and power factor as arising from the moderate band-gap and low effective mass. Meanwhile, compared to graphene-like silicene, the soften acoustic branches and enhanced anharmonicity lead to the extremely low lattice thermal conductivity, i.e., 0.68 W mK−1 at 300 K. Calculated thermoelectric figure of merit reaches 1.98 at 300 K, which is a recorded value among two-dimensional materials, indicating the potential of hhk-silicene as a thermoelectric material.

Realizing excellent thermoelectric performance in Ag-doped Cu2SnSe3-ZnSe solid solution by symmetry modification and stacking promotion

Ternary Cu2SnSe3 exhibits an inherent low symmetry and an unfavorable Seebeck coefficient. By strategic alloying with the highly symmetrical ZnSe, the transformation of a monoclinic structure into a tetragonal one was realized, yielding a higher band degeneracy in the electronic band. Therefore, the highest power factor in Cu2SnSe3-ZnSe solid solution reached 7.39 μW cm−1 K−2 at 773 K. Accompanied by this, the energy barrier for slip initiation during the stacking formation decreased, enabling a higher possibility of stacking faults and twins and a low lattice thermal conductivity as 0.79 W m−1 K−1 at 773 K for (Cu2SnSe3)0.6(ZnSe)0.4. Based on ZnSe alloying, the weaker covalent AgSe bonds are introduced to reduce the phonon velocities and facilitate mass fluctuation by Ag-substitution for Cu, resulting in a very low lattice thermal conductivity as 0.49 W m−1 K−1 at 773 K for (Ag0.2Cu1.8SnSe3)0.6(ZnSe)0.4. Eventually, an excellent ZT of 0.98 was achieved at 773 K for (Ag0.2Cu1.8SnSe3)0.6(ZnSe)0.4 through a progressive optimization on thermoelectric properties. Our work underscored the pivotal role of enhancing structural symmetry, increasing stacking nucleation probability and weakening covalent bonds in realizing excellent thermoelectric performance.

Filtering low‐energy carriers to enhance thermoelectric performance of Cd‐doped SnSe via incorporation of MXene sheets

AbstractSnSe‐based materials have attracted widespread attention in thermoelectrics due to their outstanding thermoelectric performance. However, the pristine and unmodified polycrystalline SnSe reveals poor electrical properties. Doping and constructing nanostructured composite architectures to produce energy filtering effect proved to be an effective method to strengthen thermoelectric performance. In this study, Ti3C2/Sn0.98Cd0.02Se composites are successfully fabricated by the solvothermal method combined with the electrostatic self‐assembly method and spark plasma sintering. The phase interface introduced by incorporating Ti3C2 into Sn0.98Cd0.02Se can effectively filter low‐energy carriers due to its generation of energy barriers, thereby the Seebeck coefficient of x wt% Ti3C2/Sn0.98Cd0.02Se x = (0.05, 0.5, 1) samples is better than that of the pristine Sn0.98Cd0.02Se over the whole temperature range. Meanwhile, high conductivity was also obtained in 1 wt% Ti3C2/Sn0.98Cd0.02Se sample so that the high power factor of 3.31 μWcm−1K−2 was acquired at 773 K. Ultimately, a peak ZT value of 0.41 was obtained at 773 K, compared with pristine Sn0.98Cd0.02Se, and the thermoelectric performance improved by 24%. This study offers an available approach to efficiently enhance the thermoelectric properties of polycrystalline SnSe‐based materials.

Janus breathing-Kagome lattice Nb3TeX7 (X = Cl, Br and I) with low thermal conductivity and high thermoelectric figure of merit

Kagome lattices have attracted much attention because of their potential in superconductivity and topological applications. In this work, we proposed three two-dimensional Janus breathing-Kagome lattices, Nb3TeCl7, Nb3TeBr7 and Nb3TeI7, and further investigated their stability, electronic and thermoelectric (TE) transport performance. We illustrated that the three materials all possess high stability, and low cleavage energy of 0.21–0.22 J/m2. Besides, they exhibit common features of Kagome lattices, such as fat bands and van Hove singularities near band-edges, which lead to high Seebeck coefficient (0.37–0.57 mV/K) and TE power factor of (2.79 − 3.71 mW/K2m). Further, owing to their asymmetric Janus structures, the strong coupling between acoustic and optical phonons, as well as low frequency for lying-phonons, the three lattices also possess low lattice thermal conductivity of 1.06–2.76 W/mK. Ultimately, they deliver promising TE figure of merit of {0.28, 0.39, 0.43} at 300 K, and increase further to {1.09, 1.39, 1.40} at 700 K, demonstrating breathing-Kagome lattice Nb3TeX7 are suitable candidates in TE application.

Constructing of amorphous/PbSe/amorphous multiple quantum wells with record high thermoelectric properties

Quantum well (QW) is one of the proposals to improve the thermoelectric properties. However, previous studies have shown that the large electron and phonon tunneling across the layers in semiconductor-based QWs and oxide-based QWs, respectively, are the two main challenges that need to be addressed. In this work, PbSe/amorphous-SrTiO3 (α-STO) supperlattices with a multiple quantum-well (MQW) structure can overcome both limitations. We demonstrate that the PbSe/α-STO MQW shows a high power factor of ∼ 24.5 μW cm−1K−2 at room temperature due to the strong quantum confine effect. In addition, the amorphous-SrTiO3 layer can engender intrinsically low thermal conductivity (0.27± 0.05 W m−1 K−1). The maximum estimated zT value is 2.7 for PbSe/α-STO MQW at room temperature, which is more than 1800 % higher than that of pure PbSe films (zT = 0.15).

Enhanced thermoelectric performance of iso-valent Al substituted Bi2S3via carrier tuning and multiscale phonon scattering

Bismuth sulphide is one of the promising thermoelectric material due to its low thermal conductivity, less toxicity, and abundance in nature. This work analyzed an Al-substituted Bi2S3 compounds for mid-temperature thermoelectric applications prepared by hydrothermal route. The combination of stacking faults and point defects significantly improved the phonon scattering, resulting in decreased thermal conductivity in (x = 0.10) Al substituted sample with the value of 0.498 Wm−1K−1 at 623 K. Also, it simultaneously contributes to the enhancement in carrier concentration of −2.15 × 1019 cm−3, resulting the increased electrical conductivity of 10,142 Sm-1 at 563 K. Further, x = 0.025 Al substitution in Bi2-xAlxS3 leads to a high power factor of 338 Wm−1K-2 and a low phonon thermal conductivity of 0.578 μWm−1K−1, leading to a maximum zT of 0.30 at 623 K.

Enhanced thermoelectric figure-of-merit in ‘defective’ half-Heusler Nb0.8CoSb

The half Heusler alloys are potential mid-to-high temperature range thermoelectrics due to their high power factor, solid structural stability and high mechanical strength. However, the high lattice thermal conductivity inherent to these materials reduces the zT, rendering them less useful for practical applications. The ‘defective’ half-Heuslers provide an attractive alternative to mitigate these issues. In these materials, the intrinsic lattice defects present in the form of vacancies lower the lattice thermal conductivity substantially. Here, we study the effect of excess Nb and Sn doping in the defective half Heuslers Nb0.8+δCoSb1−xSnx. We show that Sn doping allows for: (i) optimizing the carrier concentration with a much finer control than if only δ is increased, and (ii) incorporation of a higher concentration of Nb in the structure. A combination of optimized carrier concentration and synergistic changes in the band structure, including the appearance of a new flat band near 50 meV above the Fermi energy due to excess Nb, suppresses the bipolarity and enhances the thermopower further at high temperatures as the average band effective mass of the carriers increases. We, therefore, obtain a high zT exceeding 1 at 1100 K for Nb0.85CoSb0.95Sn0.05. This value is ≈ 15% higher than the highest zT previously reported.

Average current mode controller for bridgeless PFC SEPIC converter with second-order model reduction operated in continuous conduction mode.

This paper proposes an average current mode controller (ACMC) for a single-phase bridgeless power factor correction (PFC) circuit using a single ended primary inductor converter (SEPIC) via second-order model reduction. The superiority of the proposed controller is PFC accomplished at power up to 350 W with high efficiency via the second-order model reduction. The design and implementation of ACMC on the converter operated with continuous conduction mode (CCM) is explained in detail. ACMC forces input current to follow sinusoidal current reference at different power levels and sustain high power factor (PF). The proposed controller is designed based on the theoretical analysis operation of the circuit. For verification, MATLAB/Simulink simulations are carried out and validation through an experiment test rig for 110-220 Vrms input, 100 Vdc/ 350 W output prototype at 20 kHz switching frequency. It is proven that the proposed controller strategy accomplishes high PF, high efficiency and conformity with the simulation.

Enhanced Thermoelectric Properties of Sb2Te3 Thin Films by In Doping

Flexible Sb2Te3-based thermoelectric (TE) materials are promising candidates for fabricating energy devices that power wearable electronics and sensors. Enhancing the TE properties of Sb2Te3 thin films represents a significant scientific investigation. In this work, a thermal diffusion method is applied to prepare the In-doped Sb2Te3 thin film. In doping can lead to a high Seebeck coefficient of ~137.04 μV K−1 as well as moderate electrical conductivity. As a result, the high power factor of ~18.22 μW cm−1 K−2 at 303 K is achieved. Moreover, In doping could reduce the thermal conductivity owing to the increase in phonon scattering. Finally, the high ZT values of ~0.47 at room temperature (303 K) and ~0.6 at 453 K are obtained. This indicates that In doping is a highly promising and effective approach to improving the TE performance of Sb2Te3 thin films.

Clathrate structure of YB3C3 for high-performance thermoelectrics with superior mechanical properties

Exploring high-performance thermoelectric materials with improved mechanical properties is important for broadening the application scope and the assembly requirement of stable devices. This work presents an effective strategy to discover hard thermoelectric material by inserting foreign atoms in the rigid covalent framework. We demonstrate this in boron-carbon clathrate VII structure, showing a promising candidate for highly efficient thermoelectric energy conversion, especially with Y atom filled in the cage, with a peak zT of 0.73 at 1,000 K. The ab initio calculations indicate that YB3C3 system has low lattice thermal conductivity of 4.5 W/(m·K) at 1,000 K due to the strong rattling of encaged Y atom. The strongly covalent framework provides highly degenerate band structures consisting of heavy and light electron pockets, which can maintain high carrier mobility arising from small effective mass and thus large group velocity. Consequently, high power factor can be achieved in YB3C3 for both electron and hole doping. In addition, it exhibits well mechanical properties and a Vickers hardness of 23.7 GPa because of the strong covalent boron-carbon framework. This work provides a novel avenue for the search of high-performance thermoelectric materials with excellent mechanical properties, based on boron-carbon clathrate structure.