Optimal Power Factor Research Articles

Flexible film and thermoelectric device of single-walled carbon nanotube@conductive metal-organic framework composite

Conducting metal-organic frameworks (MOFs) hold a great potential for many electronic applications because of their unique chemical and physical properties. Thermoelectric (TE) conversation based on conductive MOFs is the cutting-edge frontiers and remains great challenges, such as low electrical conductivity, rigidity, and difficulty to process. Here, a free-standing flexible film of the composite, where covalent bond grafting exists between single-walled carbon nanotubes (SWCNTs) and porous MOF (SWCNT@Ni-1,2,5,6,9,10-triphenylenehexathiol (THT)), is prepared by a convenient vacuum filtration method. The as-fabricated SWCNT@Ni-THT composite films exhibit good flexibility and p-type TE characteristics. An optimized power factor and a maximum figure of merit are ∼98.1 μW m-1/K2 and ∼0.037, respectively, for the composite film with 4 wt% SWCNT loading at 300 K. Furthermore, a flexible TE device connected by four rectangular films in series can generate an open-circuit voltage (VOC) of ∼10.02 μV and the maximum power (Pmax) of ∼1.59 μW at a temperature difference of 60 K. This work provides a novel way to prepare high-performance flexible films of MOF-based TE composites and demonstrates their potential applications in wearable electronics.

Analyses of charging power and performance in electric vehicles using Fuzzy Type-II approach

Nowadays, there is a need for charging electric vehicles (EVs) wirelessly, since it provides a more convenient, reliable, and safer charging option for the EV customers. A wireless charging system using a double-sided LCC compensation topology is proven to be highly efficient. In this paper, considering the importance of wireless charging of electric vehicles, using a circuit equivalent to the wireless power Transfer (WPT) system, the behavior of electric vehicles in the power grid only in technical analysis is investigated. Accordingly, two different scenarios have been used in modeling and simulation. In the first scenario, the charge of electric vehicles was controlled using an [Formula: see text] controller to stabilize the charging frequency. The model predictive control (MPC) controller was used to identify the optimum power factor for electric vehicles and determine the optimal power values and efficiency. In the second scenario, a two-way AC-DC converter was designed using a Fuzzy type-II controller under uncertainty to provide precise control over the vehicle charge exchange in terms of voltage, current, and stage of control (SOC). So, type-II fuzzy controller is used to control the process of charging and discharging vehicles. The results show that the final efficiency is 0.98, and the power will be 1480 W.

Accurate in situ measurements of thermoelectric transport properties at high pressure and high temperature.

Regulating electron structure and electron-phonon coupling by means of pressure and temperature is an effective way to optimize thermoelectric properties. However, in situ testing of thermoelectric transport performance under pressure and temperature is hindered by technical constraints that obscure the intrinsic effects of pressure and temperature on thermoelectric properties. In the present study, a new reliable assembly was developed for testing the in situ thermoelectric transport performance of materials at high pressure and high temperature (HPHT). This reduces the influence of thermal effects on the test results and improves the success rate of in situ experiments at HPHT. The Seebeck coefficient and electrical resistivity of α-Cu2Se were measured under HPHT, and the former was found to increase with increasing pressure and temperature; for the latter, although an increase in the pressure acted to lower the electrical resistivity, an increase in the temperature acted to increase it. On increasing pressure from 0.8 to 3GPa at 333K, the optimal power factor of α-Cu2Se was increased by ∼76% from 2.36 × 10-4-4.15 × 10-4Wm-1K-2, and the higher pressure meant that α-Cu2Se had its maximum power factor at lower temperature. The present work is particularly important for understanding the thermoelectric mechanism under HPHT.

Thermoelectric power factor of MnSb2X4 (X = S, Se) spinel chalcogenides – A DFT study

Recently, spinel chalcogenides have been found to be promising class of materials in thermoelectric power generation. In this line, the complete understanding about electronic and thermoelectric properties of MnSb2S4 and MnSb2Se4 is crucial. With the help of first-principles calculations, its interesting characteristics are explored, including bonding nature, ground state magnetic ordering, mechanical stability, etc. A systematic study on these materials revealed their antiferromagnetic and semiconducting behaviour. The Seebeck coefficient as a function of carrier concentration has its maximum at 600 and 681 μV K−1 (T = 300 K) for hole doped MnSb2S4 and MnSb2Se4 respectively. Besides the coupled behaviour of Seebeck coefficient and electrical conductivity, an optimal power factor of 1.82 and 0.96 mW m−1 K−2 is attained at 300 K for MnSb2S4 and MnSb2Se4 respectively. This study suggests that both the spinels can be potential p-type thermoelectric materials for near room temperature power generation applications and enables the path for their experimental investigations.

Power loss minimization and voltage profile improvement of radial and mesh distribution network using sine cosine optimization based DG allocation

Due to the increasing population and emerging technologies, energy requirements are increasing progressively. Distributed generation (DG) is an excellent option to handle the increased power demand. A well optimized DG can help to reduce power losses, CO2 emission and improve voltage profiles. This paper uses sine cosine algorithm to find the optimal location and best size ofDG with power loss minimization as its objective function. It presents the comparison of power loss reduction and voltage profile enhancement due to allocation of DGoperating at 0.85, 0.95 power factor lag andthe optimal power factor that has been obtained by sine cosineoptimization. IEEE 15, 69 bus radial and 33, 69 bus weakly meshed systems with five tie lines are used for power loss analysis. Annual energy saving due to allocating DG with different power factors have been analyzed. All the results are simulated in MATLAB 2021a.

Thermoelectric properties of Sm-doped BiCuSeO oxyselenides fabricated by two-step reactive sintering

Among layered oxygen-containing compounds, BiCuSeO is one of the most promising candidates for thermoelectric applications due to its intrinsically low thermal conductivity and good thermal stability. However, the rather poor electrical conductivity of pristine BiCuSeO hinders its potential. Further enhancement of the thermoelectric performance by single doping at Bi site is limited mainly due to dramatic decrease of carrier mobility. Thus, new strategies, such as dual doping or doping with variable-valence elements seem to be promising. Along with that, the development of a fast and scalable synthesis route is essential for the industrial-scale fabrication of thermoelectric materials. Hence, in this paper, Bi 1– x Sm x CuSeO samples (0 ≤ x ≤ 0.08) have been synthesized with a simple and scalable reactive sintering process. For comparison, Bi 1– x Sm x CuSeO oxyselenides were also obtained by the conventional solid-state route. Our results highlight that, Sm for Bi substitution increases the electrical conductivity by 1.5–2 times and decreases the Seebeck coefficient by ~1.4 times at 873 K for both series. Overall, considering the increase of lattice thermal conductivity upon doping and not optimized power factor, the figure of merit z T is reducing upon doping. • Sm-doped BiCuSeO oxyselenides fabricated by reactive sintering. • Sm doping leads to an increase of σ from 39 Ω –1 cm –1 to ~55 Ω –1 cm –1 at 873 K. • Quality factor is reduced upon Sm doping due to increase in κ and decrease of μ w .

Dual Post‐Treatments Boost Thermoelectric Performance of PEDOT:PSS Films and Their Devices

AbstractOwing to intrinsically high electrical conductivity and low thermoelectric conductivity, poly(3,4‐ethylenedioxithiophene):poly(styrenesulfonate) (PEDOT:PSS) shows promising thermoelectric properties. However, its relatively low power factor limits the practical applications of PEDOT:PSS. Here, unique dual post‐treatments by sodium sulfite (Na2SO3) and formamide (CH3NO) to boost the thermoelectric performance of flexible PEDOT:PSS films with an optimized power factor of 74.09 µW m–1 K–2 are used. Comprehensive characterizations confirm that CH3NO reduces the excessive insulating PSS and thereby increases the electrical conductivity, while Na2SO3 lowers the reduction of the doping level of PEDOT, leading to an increased Seebeck coefficient. Furthermore, the rationally post‐treated PEDOT:PSS films are assembled into a flexible thermoelectric device that exhibits an open‐circuit voltage of 2.8 mV using the heat from the human arm and an output power density of 2.56 µW cm–2 by a temperature difference of 25 K, indicating great potential for practical applications on sustainably charging low‐grade wearable electronics.

Combining chemical doping and thermal annealing to optimize the thermoelectric performance of the poly(3-hexylthiophene)

Significant improvements to the thermoelectric (TE) property of doped conjugated polymeric materials have been widely investigated in recent years, and chemical doping is considered as a key to maximize the thermoelectric performance of conjugated polymers by increasing their electrical conductivity. However, chemical doping with the ability to increase the carrier concentration will reduce the order of the films, which cannot guarantee the high electrical conductivity, thus it is crucial to keep good charge transport pathways. Herein, chemical doping and thermal annealing are combined to optimize the thermoelectric property of poly(3-hexylthiophene) (P3HT). First, the doping efficiency of three dopants on P3HT was systematically investigated, among which, the film doped with FeCl3 exhibits the highest thermoelectric performance. Subsequently, thermal annealing treatment method is further applied to construct carrier pathways via improving the crystallinity orientation of the FeCl3 doped films. As a result, the electrical conductivity reaches 201.1 S cm−1, which increase by 42% in comparison with unannealed film (141.1 S cm−1). The optimized power factor of FeCl3 doped P3HT film is 1.72 times that of unannealed doped film and 13.0 times that of unannealed P3HT film doped by F4TCNQ. The results of this investigation demonstrate that combining chemical doping and thermal annealing is a feasible strategy to improve the thermoelectric performance of the conjugated polymer.

A novel artificial hummingbird algorithm for integrating renewable based biomass distributed generators in radial distribution systems

Improving the performance of the electric distribution network is essential to meet the needs of the customer and guarantee the service continuity. Installing generators with small sizes known as distributed generators (DGs) can contribute to enhance the network operation by mitigating the network loss and improving the voltage profile. Integrating these generators in inappropriate places can cause serious consequences to the network operation. Therefore, this paper proposes a novel metaheuristic approach of artificial hummingbirdalgorithm (AHA) to identify the best locations and sizes of biomass-based DGs in radial distribution network. The proposed approach has enriched exploration and exploitation phases that enhancing its search capability and avoiding stuck in local optima. The network active power loss and the voltage deviation are selected as the targets to be minimized. Moreover, a new version of AHA is programmed to solve multi-objective problem with the purpose of mitigating both targets. The analysis is conducted on three radial distribution networks of IEEE 33-bus, IEEE 69-bus, and IEEE 119-bus. Three scenarios are implemented in each network, the first one is minimizing the active power loss, the second one is mitigating the voltage deviation, and the last one is multi-objective problem. Also, biomass-based DGs with unity, fixed, and optimal power factors are analyzed. Excessive comparison to fractal search algorithm, particle swarm optimizer, genetic algorithm, the whale optimization algorithm, sperm swarm optimization, tunicate swarm algorithm, pathfinder algorithm, seagull optimization algorithm, and sine cosine algorithm, multi-objective water cycle algorithm, multi-objective grey wolf optimizer, and multi-objective sparrow search algorithm is conducted. Moreover, statistical tests of Wilcoxon, Friedman, ANOVA, and Kruskal Wallis are performed to assess the performance of the proposed approach. The gotten results confirmed the preference and competence of the proposed approach in integrating the biomass-based DGs in radial distribution networks.

Vapor phase polymerization of Ag QD-embedded PEDOT film with enhanced thermoelectric and antibacterial properties

Nonferric oxidant precursors have the unique advantage of directly polymerizing poly(3,4-ethylenedioxythiophene) (PEDOT)-inorganic composites. However, due to limited solubility and unmatched oxidation potentials, most oxidants only produce powders or porous materials. To obtain high-quality films with improved homogeneity and controllable particle sizes, the oxidants should be adaptable to high-standard PEDOT film fabrication techniques such as vapor phase polymerization (VPP). In this work, we discovered for the first time a nonferric metal salt suitable for the VPP process. With the addition of an Fe(III) salt to stabilize the reaction and adjust the oxidant ratio, micron-thick antibacterial S-PEDOT-Ag quantum dot (QD) composite films with tunable Ag wt% can be synthesized in one facile step. With a low Ag loading of ~0.2 wt%, the film exhibited an optimized power factor of 63.1 μW/mK2, which is among the highest values thus far reported for PEDOT-metal composites. Increase of the Ag(I) concentration in the precursor to a certain level may lead to minor decomposition of the polymer followed by the formation of Ag2S particles.

Sandwiched Graphene/Bi2Te3/Graphene Thermoelectric Film with Exceptional Figure of Merit for Flexibility

AbstractFlexible thermoelectrics (TEs) that fit curved human skin well, could harvest energy from skin, and thus have been considered as a promising portable power source for wearable electronics. Bi2Te3, the most popular room‐temperature TE material, is still challenging to be applied in flexible devices due to its rigid nature. Although many Bi2Te3‐based films have been reported to be flexible when made thin enough, the thermal and electrical loads across them are rather small with severe limitation on the maximum power output. This work realizes a thick Bi2Te3‐based TE film with a “graphene/Bi2Te3/graphene” sandwiched structure, which demonstrates an unprecedentedly high figure of merit for flexibility among all Bi2Te3‐based films ever reported, due to the outstanding intrinsic flexibility of graphene and a small slippage barrier. Meanwhile, graphene acts as express conducting channels as well as carrier donors, resulting in an increased electrical conductivity. The numerous graphene/Bi2Te3 heterointerfaces induce energy filtering effect, leading to an enhanced Seebeck coefficient, and thus an optimized power factor is achieved. This work offers a cost‐effective avenue to make highly flexible TE films for power supply of wearable electronics by intercalating TE nanoplates into 2‐dimensional nanosheets.

Optimal Power Allocation and Cooperative Relaying under Fuzzy Inference System (FIS) Based Downlink PD-NOMA

Optimal power allocation (PA) is a decisive part of the power domain non-orthogonal multiple access (PD-NOMA) technique. In PD-NOMA, users are served at the same time and using the same frequency band, but at differing power levels. In this paper, the optimization problem for PA is formulated with distance (d), signal-to-noise ratio (SNR), and foliage depth (df) constraints. A fuzzy inference system (FIS) addresses the optimization problem by allocating the optimal power factors (power levels) to each user in the vicinity of a 5G base-station (gNodeB). The proposed system incorporates a cooperative relaying technique at the near-user to assist the far-user facing signal degradation and greater path losses. A realistic 5G micro-cell is analyzed for downlink PD-NOMA where superposition coding (SC) is used at the transmitter side, a successive interference cancellation (SIC) scheme at the near-user, and a maximum ratio combining (MRC) technique at the far-user’s receiver, respectively. For both simple PD-NOMA and cooperative relaying PD-NOMA, the presented technique’s bit-error-rate (BER) performance is evaluated against various SNR values, and it is concluded that cooperative PD-NOMA outperforms simple PD-NOMA. By combining the presented FIS system with cooperation relaying, the proposed FIS method guarantees user fairness in PD-NOMA systems while also significantly improving performance.

Prediction of a high-ZT and strong anisotropic thermoelectric material: Monolayer InClSe

In this work, thermoelectric (TE) properties of monolayer InClSe are investigated by using the first-principles calculations combined with Boltzmann transport theory, which is a novel member of FeOCl-type 2D materials . We find that the electronic and thermal transport parameters along x and y axis are quite different, resulting in a strong anisotropic thermoelectric performance of monolayer InClSe, which provides a possibility to design anisotropic thermoelectric device. For n-type doping, monolayer InClSe has high electrical conductivity along x-axis. Detailed calculations reveal that the high electrical conductivity is originate from the long electron relaxation time and high connectivity of electron conduction channels. The high electrical conductivity and satisfactory Seebeck coefficient result in the excellent power factor ( PF ) for monolayer InClSe . For n-type doping, the optimal PF along x-axis can reach 47.8 mW m −1 K −2 at 700 K, which is much higher than most typical thermoelectric materials . Combining excellent PF and suppressed lattice thermal conductivity , the n-type doping monolayer InClSe has high ZT values in wide temperature range (300 K–700 K) along x-axis and the maximal ZT value reaches 2.82 at 700 K. Our results demonstrate that monolayer InClSe is a promising thermoelectric candidate for energy harvesting in moderate-temperature range. The calculated figure of merit ZT of n-type monolayer InClSe at three different temperature 300 K, 500 K, and 700 K, respectively. • We demonstrate that monolayer InClSe is a promising anisotropic thermoelectric candidate. • For n-type doping, ultra-high electrical conductivity along x-axis reaches 1.82 × 10 5 S/m (300 K) at carrier concentration 1 × 10 12 cm −2 . • For n-type doping, the optimal PF along x-axis can reach 47.8 mW m −1 K −2 at 700 K, and the maximal ZT value is 2.82.

Synergistically optimizing carrier and phonon transport properties in n-type PbTe through I doping and SnSe alloying

PbTe is a promising thermoelectric material, but the properties in n-type PbTe need further improvement to match its advanced p-type material. In this work, the thermoelectric performance in n-type PbTe is synergistically enhanced with iodine (I) doping and SnSe alloying. The experiments show that I element is a good donor dopant to tune the carrier density and SnSe alloying can effectively balance the triple-relations between carrier mobility, carrier effective mass, and lattice thermal conductivity. Thus, high carrier mobility of ∼755 cm2V−1s−1 results in an optimum power factor (PF) of ∼27.0 μWcm−1K−2 in PbTe–2%SnSe at 573 K. Microstructure observation reveals the dispersively embedded Sn-rich nanoprecipitates in PbTe–2%SnSe, which largely suppresses lattice thermal conductivity at room temperature, from ∼3.41 Wm−1K−1 in PbTe to ∼1.01 Wm−1K−1 in PbTe–2%SnSe. Combined the optimized PF and decreased thermal conductivity, the peak ZT value of ∼1.5 can be obtained at 773 K in PbTe–2%SnSe. The obtained high thermoelectric performance in our work is comparable with other advanced n-type PbTe thermoelectrics and has great application potential.

Promoting thermoelectric performance of two-dimensional benzodithiophene-based conjugated polymer/single-walled carbon nanotube composites by polar side chain engineering

Single-walled carbon nanotube (SWCNT) based polymer composites have been developed as potent thermoelectric (TE) materials. Unfortunately, the effect of polymers' structure on the composite's TE performance remains unclear. In addition, the research on the backbone of polymers in the SWCNT based composites is limited to the one-dimensional conjugated ones, and the distinct influence of linear and macrocyclic polar side chains on TE performances remains unexplored. Herein, two kinds of benzodithiophene(BDT)-based two-dimensional (2D) conjugated polymers decorated with linear tetraethylene glycol (P(BDTP)) and macrocyclic crown ether (P(BDTC)), respectively, were designed and synthesized, and their effect on the TE performance of SWCNTs was systematically studied. The results indicated 2D BDT-based backbone exhibited strong binding ability to SWCNTs due to the expanded 2D conjugated structure. P(BDTC) displayed stronger π-π intermolecular interactions with SWCNTs than P(BDTP) due to the annular crown ester on the side chain, which were verified by fluorescence, Raman, X-ray photoelectron and scanning electron microscopy results. At the mass ratios of 1:2, P(BDTC)/SWCNT composites gained an optimized power factor of 137.7 ± 7.9 μW m−1 K−2, achieving 181% enhancement than P(BDTP)/SWCNT composites (75.1 ± 1.6 μW m−1 K−2). Consequently, P(BDTC)/SWCNT composites-based generator exhibited the maximum actual output power of 327.9 nW at the temperature difference of around 70 K, which is 1.31 times higher than that of P(BDTP)/SWCNT-based generator (247.5 nW). Hence, incorporating macrocyclic polar side groups in conjugated polymers provides a promising structural modification strategy for organic counterparts in polymer/SWCNT composites.

Enhancement of the Thermoelectric Performance of n-Type Naphthalene Diimide-Based Conjugated Polymer by Engineering of Side Alkyl Chains

Developing n-type doped semiconducting polymers with high thermoelectric (TE) performance still remains challenging. In this paper, we show a new strategy to enhance the TE performance of n-doped naphthalene diimide (NDI)-based conjugated donor–acceptor (D-A) polymer by introducing one linear alkyl chain for each NDI unit. Film of the PNDI2T-1, in which each NDI unit is attached with one linear and one branching alkyl chains, exhibits higher electrical conductivity and a greater power factor (PF) than those of PNDI2T-2 with the same conjugated backbone and two branching side chains, after doping with either (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine (N-DMBI) or decahydro-3a,6a,9a-triazaphenalene (TAM) under the same conditions. The optimal PF values of the doped films of PNDI2T-1 with N-DMBI and TAM can reach 1.6 and 3.5 μW m–1K–2, respectively, which are among the highest reported TE performances for NDI-based semiconducting polymers after n-doping. The higher TE performance of the doped films of PNDI2T-1 is attributed to the enhancement of charge mobility and improvement of doping degree after side-chain modification. These results provide a new molecular design rationale for the future development of high-performance n-type thermoelectric semiconducting polymers.

Enhanced Thermoelectric Properties of Cu2SnSe3-Based Materials with Ag2Se Addition.

In this work, (Ag, In)-co-doped Cu2SnSe3-based compounds are prepared using a self-propagating high-temperature synthesis process. Ag2Se and as-synthesized (Ag, In)-co-doped Cu2SnSe3-based powders are mixed in a proportion according to the formula of Cu1.85Ag0.15Sn0.91In0.09Se3/x Ag2Se (x = 0, 3, 4, and 5%), which is followed by a subsequent plasma-activated sintering (PAS) to obtain consolidated composite bulks. A sandwich experiment is designed to reveal the evolution of the microstructure and phase composition of the composite samples during the PAS process. We investigate the reaction mechanism between Ag2Se and Cu2SnSe3-based matrix as well as the influence of Ag2Se on the phase composition, microstructure, and thermoelectric transport properties of the composites. Ag2Se addition is proven to be effective to improve Ag solubility in the Cu1.85Ag0.15Sn0.91In0.09Se3 matrix and introduce a CuSe secondary phase and an Ag-rich phase at grain boundaries. The electrical conductivity of Cu1.85Ag0.15Sn0.91In0.09Se3/x Ag2Se (x = 0, 3, 4, and 5%) composites decreases while the Seebeck coefficient increases with increasing Ag2Se addition, resulting in an optimized power factor. Moreover, benefiting from the collective phonon scattering at various defects induced by Ag2Se addition, the composite samples exhibit significantly suppressed lattice thermal conductivity, which reaches as low as 0.11 W m-1 K-1 at 700 K for the x = 5% sample. A peak figure-of-merit (ZT) of 1.26 at 750 K and an average ZT of 0.75 at 300-800 K are obtained for Cu1.85Ag0.15Sn0.91In0.09Se3/5% Ag2Se. This work provides an efficient way to improve average ZT values of Cu2SnSe3-based compounds for promising power generation at intermediate temperatures.

Optimal Allocation of Renewable Distributed Generations Using Heuristic Methods to Minimize Annual Energy Losses and Voltage Deviation Index

In this paper, two metaheuristic methods, genetic algorithm and particle swarm optimization, are proposed to determine the optimal locations, sizes, and power factors of single and double distributed generation units. In line with the 2050 carbon neutral goal, the aim was to integrate renewable distributed energy sources such as photovoltaic panels and wind turbines into the distribution system with a high penetration level. In contrast to most studies based on constant loads and dispatchable generations, an application considering the seasonal uncertainties of generation and consumption was performed to minimize the annual energy losses and voltage deviations of the distribution network. In addition, dispatchable, controllable and fuel-based conventional resources were allocated to compare the contributions of renewable resources. These seasonal case studies with various constraints were applied to IEEE 33-bus radial distribution network. To verify the feasibility and robustness of the proposed algorithms, case studies for peak loads were created and compared with the literature studies. While all distributed generation sources were operated at both unity and optimum power factor in all case studies, zero power factor and leading power factor scenarios were examined for a peak load only. Photovoltaic applications without energy storage technologies have not been efficient because of the uneven daily distribution of solar irradiance, especially insufficient irradiation in the evening and excessive irradiation at noon. However, wind energy applications are more reliable and feasible, because the wind speed distribution is relatively more uniform than that of solar irradiation, both seasonally and daily. In all cases, operating distributed generation sources at the optimal power factor provided better results than those operating at unity power factor. Consequently, wind turbines operating at optimal power factors have been found to contribute better than photovoltaic systems, and are almost as good as conventional sources with controllable power output. While both proposed algorithms yielded better results than those in the literature, particle swarm optimization was better than genetic algorithm in terms of providing the best solution, faster convergence, and shorter running time.

Novel Real Valued Improved Coral-Reef Optimization Algorithm for Optimal Integration of Classified Distributed Generators

In recent times, Distributed Generation (DG) penetration, especially, through Renewable Energy Sources (RES) has been growing immensely due to marginal carbon footprints. Furthermore, they make system more reliable by minimizing the voltage deviation of the distribution network. Nevertheless, to exploit the DGs in the best manner, they need to be sited and rated optimally. Diverse solutions exist for the problem mainly classified as: analytical approaches, classical non-linear optimization algorithms and meta-heuristic methods. With the objective of minimizing power loss, this manuscript proposes a novel hybrid meta-heuristics approach: Particle Swarm Optimization-Coral Reef Optimization (PSO-CRO) for identifying an optimum positioning and rating of Type-1, Type-2 & Type-3 DGs (at 0.82 optimal power factor) in IEEE 33, 69 & 118 bus Radial Distributed System (RDS). Furthermore, the results from the proposed hypothesis are compared with its prevalent peers, namely, PSO, CRO, Gravitational Search Algorithm (GSA), PSO-GSA and PSO-Grey Wolf Optimization (PSO-GWO) etc. The results of the proposed algorithm are also compared with the results of GAMS/CONOPT commercial solver. The simulation results prove the robustness, higher efficacy and faster convergence of the proposed method when applied to larger distribution systems.

The effects of alkaline-earth-metal-element doping on the thermoelectric properties of β-Zn4Sb3

The effects of alkaline-earth metal elements Ca, Sr, and Ba on the electronic structure and thermoelectric properties of β-Zn4Sb3 were investigated by performing self-consistent ab initio electronic structure calculations within density functional theory and solving the Boltzmann transport equations within the relaxation time approximation. The results demonstrate that these alkaline-earth metal elements with s orbitals could introduce giant sharp resonant peaks in the electronic density of states (DOS) near the host valence band maximum in energy. And these deliberately engineered DOS peaks result in a sharp increase of the room-temperature Seebeck coefficient of β-Zn4Sb3 by a factor of nearly 8/9/19, respectively. Additionally, with the simultaneous increase of conductivity and decline of carrier thermal conductivity upon Ca/Sr/Ba doping, potentially, at least, 10/4/2-fold increase in optimizing power factor, and 14/12/8-fold increase in thermoelectric figure of merit of β-Zn4Sb3 at room temperature are achieved. And their corresponding optimal Fermi levels are all located near the host valence band maximum.