Suitable Power Research Articles

Ultrasound-assisted fast encapsulation of metal microparticles in SiO2 via an interface-confined sol-gel method

Although the traditional Stoˇber process-based methods are widely used for encapsulation of metal nanoparticles in SiO2, these time-consuming methods are not effective for coating metal microparticles with a uniform SiO2 layer of desired thickness. Herein, an ultrasound-assisted, interface-confined sol–gel method is proposed for fast encapsulation of metal microparticles in SiO2, and the encapsulation of Sn microparticles is chosen as an example to illustrate its feasibility. The proposed method involves covering metal microparticles with liquid films that contain water, alcohol, surfactant (Span-80) and catalyst (NH4F) and then ultrasonically dispersing these particles into cyclohexane, where tetraethylorthosilicate (TEOS) is added. To ensure the hydrolysis-condensation reactions of TEOS occurring at the particle-cyclohexane interface so that the formed SiO2 is coated on the particles, the microparticles should be well dispersed into cyclohexane with the liquid films being not broken away from their surfaces. It is found that the assistance of probe sonication and the addition of surfactant are crucial to achievement of a good dispersion of metal microparticles in cyclohexane. And using high-viscosity alcohol (namely glycerol), controlling the volume ratio of water to alcohol and the amount of water, and choosing a suitable ultrasonic power are essential for preventing the formation of free SiO2 (namely SiO2 that is not coated on the particles), which is a result that the liquid films escape from the particle surfaces under ultrasonic cavitation. Our results have also revealed that the thickness of SiO2 layer can be adjusted by changing the reaction time or the total amount of water. In particular, the thickness of SiO2 layer can be easily raised by simply repeating the encapsulation procedure. Compared with the traditional Stoˇber process-based methods, the proposed method is time-saving (reaction time: about 30 min vs. more than 12 h) and extremely effective for coating microparticles with a continuous, uniform SiO2 layer of desired thickness.

Paper-based lactate biofuel cell array with high power output

Printable wearable lactate biosensors have attracted significant attention, and printable lactate biofuel cells have gained popularity as suitable power supplies for these sensors. However, realizing an appropriate power supply for the practical application of these sensors as wearable devices, it is necessary to improve the output of lactate biofuel cells. In this study, we fabricated a lactate biofuel cell that employed paper substrate using screen printing. The proposed paper-based biofuel cell (PBFC) features a novel electrode design that affords an open circuit voltage of approximately 3.4 V when using an array with six cells in series. Furthermore, a 6 × 6 array of the lactate biofuel cell, i.e., an array comprising six cells in series and six cells in parallel, yielded a power output of 4.3 mW. To the best of our knowledge, this output of the proposed design is higher than those of previously reported lactate biofuel cells. Arrays of the proposed cell were capable of driving a Bluetooth low-energy device for wireless transmission, without requiring a booster circuit. A commercially available activity meter could be driven for 1.5 h using artificial sweat to fuel a 6 × 6 array of the PBFCs.

Methodology for bondwire lifetime evaluation of multifunctional PV inverter during harmonic current compensation

Multifunctional photovoltaic (PV) inverters have been described as a suitable power quality solution in modern power systems based on distributed generation. The basic idea is to use the PV inverter to perform ancillary services, such as harmonic current compensation (HCC). Nevertheless, this extra functionality may affect the lifetime consumption of the PV inverter. Indeed, only few works in literature discuss this topic, since the lifetime evaluation procedure during HCC is not straightforward. In addition, the traditional methodology currently available in the literature cannot be easily extended to HCC operation. Therefore, this work proposes a new lifetime prediction methodology which considers the effects of both fundamental and harmonic currents injected by the PV inverter. The proposed methodology can take into account all the additional power cycling due to any harmonic current combination. Furthermore, the lifetime evaluation is carried out considering the mission profiles of solar irradiance, ambient temperature, harmonic current amplitude and phase angle. The obtained results indicate that HCC increases the number of temperature cycles and may significantly affect the PV inverter lifetime. When the ratio between the harmonic and fundamental current amplitudes increases, the PV inverter lifetime consumption also increases. In addition, a strong dependence between lifetime consumption and the harmonic phase angle is observed for low order harmonics, such as 3rd and 5th harmonics.

Analysis of power conversion technology options for a self-powered furnace

A self-powered furnace is defined as one that imports no electricity: a power cycle integrated into the furnace generates all the electrical power needed, and the heat rejected by the power cycle contributes to space heating. This paper presents criteria for selection of suitable power generation technology for such a furnace. A weighting system was presented to assign weight to each criterion based on its importance to the success of a self-powered furnace implementation. Power generation candidates were reviewed and scored based on the selection criteria. The top five candidates were analyzed to quantitatively compare the additional heat exchange requirements they impose on a baseline furnace. Air-cooled internal combustion engines and microturbine generators had negligible impact on the heat exchange requirement compared to a baseline furnace. Liquid-cooled internal combustion engines increased the heat exchange requirement by a factor of 1.5. Thermoelectric generators and thermophotovoltaic increased the heat exchange requirement by a factor of roughly 2.5. Organic Rankine cycle increased the heat exchange requirement by a factor of 5.

Droop Method Development for Microgrids Control Considering Higher Order Sliding Mode Control Approach and Feeder Impedance Variation

Due to the growing power demands in microgrids (MGs), the necessity for parallel production achieved from distributed generations (DGs) to supply the load required by customers has been increased. Since the DGs have to procure the demand in parallel mode, they are faced with several technical and economic challenges, such as preventing DGs overloading and not losing network stability considering feeder impedance variation. This paper presents a method that upgrades the droop controller based on sliding mode approach, so that DGs are able to prepare a suitable reactive power sharing without error even in more complex MGs. In the proposed strategy, the third-order sliding mode controller significantly reduces the V-Q error and increases the accuracy in adjusting the voltage at the DG output terminals. Various case studies conducted out in this paper validate the truthfulness of the proposed method, considering the stability analysis using Lyapunov function. Finally, by comparing the control parameters of the proposed technique with existing methods, the superiority, simplicity and effectiveness of the 3rd order sliding mode control (SMC) method are determined.

Piezoelectric Nanogenerator Based on Lead-Free Flexible PVDF-Barium Titanate Composite Films for Driving Low Power Electronics

Self-powered sensor development is moving towards miniaturization and requires a suitable power source for its operation. The piezoelectric nanogenerator (PENG) is a potential candidate to act as a partial solution to suppress the burgeoning energy demand. The present work is focused on the development of the PENG based on flexible polymer-ceramic composite films. The X-ray spectra suggest that the BTO particles have tetragonal symmetry and the PVDF-BTO composite films (CF) have a mixed phase. The dielectric constant increases with the introduction of the particles in the PVDF polymer and the loss of the CF is much less for all compositions. The BTO particles have a wide structural diversity and are lead-free, which can be further employed to make a CF. An attempt was made to design a robust, scalable, and cost-effective piezoelectric nanogenerator based on the PVDF-BTO CFs. The solvent casting route was a facile approach, with respect to spin coating, electrospinning, or sonication routes. The introduction of the BTO particles into PVDF enhanced the dielectric constant and polarization of the composite film. Furthermore, the single-layered device output could be increased by strategies such as internal polarization amplification, which was confirmed with the help of the polarization-electric field loop of the PVDF-BTO composite film. The piezoelectric nanogenerator with 10 wt% BTO-PVDF CF gives a high electrical output of voltage 7.2 V, current 38 nA, and power density of 0.8 μW/cm2 at 100 MΩ. Finally, the energy harvesting using the fabricated PENG is done by various actives like coin dropping, under air blowing, and finger tapping. Finally, low-power electronics such as calculator is successfully powered by charging a 10 μF capacitor using the PENG device.

Power-HIL Application Analysis of a 3-level Inverter for PMSM Machine

Power-HIL simulation is one of the emerging areas in power electronics development nowadays. It offers a convenient test environment for the whole power electronics hardware but eliminates the necessity of motor test benches and rotating machines. Selecting a suitable power amplifier for the simulator is however a challenging task. Switching power supplies can be an interesting option as Power Amplifier, but they have to offer superior power capability and dynamic performance over the DUT (Device Under Test), while maintaining high enough switching frequency to meet the dynamic requirements as well. Using commercially available inverters as Power Amplifiers would be an attractive option, if they can achieve the desired emulation accuracy. This paper investigates the possibility of using a common 3-level inverter with an L-C-L coupling network as a Power Amplifier for a P-HIL simulator, to emulate a PMSM (Permanent Magnet Synchronous Machine) machine.

A novel intrinsic space vector transformation based solar fed dynamic voltage restorer for power quality improvement in distribution system

Electric power aims to generate electrical energy and distribute to the end-user application at an acceptable voltage level. The quality of power will be affected by various factors like voltage sag, swell, harmonic and Power interruptions, etc. The major reason behind the deteriorations of the power quality is nonlinearity in loads which draws out harmonics. Due to this nonlinearity, all loads cause disturbances in the voltage waveform. In this paper, an Intrinsic Space Vector Transformation (ISVT) based solar fed Dynamic Voltage Restorer (DVR) is connected in series with the power grid to compensate for the reactive power. The operation of the proposed DVR model produces reactive power based on the voltage sag and voltage swell. The ISVT controller produces an appropriate pulse to the voltage source inverter (VSI), which delivers a suitable reactive power to compensate for the sag and swell voltages in the grid. Moreover, solar fed DVR reduces Total Harmonic Distortion (THD) value at the time of voltage sag mitigation. The performance of the proposed system is evaluated by analysing the power consumption and efficiency. Finally, the proposed system is compared with other existing methods. The simulation is carried out using MATLAB SIMULINK 2017b software.

Assessing the Potential of LPWAN Communication Technologies for Near Real-Time Leak Detection in Water Distribution Systems.

While low-power wide-area network (LPWAN) technologies have been studied extensively for a broad spectrum of smart city applications, their potential for water distribution system monitoring in high temporal resolution has not been studied in detail. However, due to their low power demand, these technologies offer new possibilities for operating pressure-monitoring devices for near real-time leak detection in water distribution systems (WDS). By combining long-distance wireless communication with low power consumption, LPWAN technologies promise long periods of maintenance-free device operation without having to rely on an external power source. This is of particular importance for pressure-based leak detection where optimal sensor positions are often located in the periphery of WDS without a suitable power source. To assess the potential of these technologies for replacing widely-used wireless communication technologies for leak detection, GPRS is compared with the LPWAN standards Narrowband IoT, long-range wide area network (LoRaWAN) and Sigfox. Based on sampling and transmission rates commonly applied in leak detection, the ability of these three technologies to replace GPRS is analyzed based on a self-developed low-power pressure-monitoring device and a simplified, linear energy-consumption model. The results indicate that even though some of the analyzed LPWAN technologies may suffer from contractual and technical limitations, all of them offer viable alternatives, meeting the requirements of leak detection in WDS. In accordance with existing research on data transmission with these technologies, the findings of this work show that even while retaining a compact design, which entails a limited battery capacity, pressure-monitoring devices can exceed runtimes of 5 years, as required for installation at water meters in Austria. Thus, LPWAN technologies have the potential to advance the wide application of near real-time, pressure-based leak detection in WDS, while simultaneously reducing the cost of device operation significantly.

An ultra-miniature broadband operational transconductance amplifier utilizing 10 nm wrap-gate CNTFET technology

Operational Transconductance Amplifiers (OTAs) are the most pivotal blocks in analog circuits and systems. With the emersion of catastrophic short channel effects for Complementary Metal Oxide Semiconductor (CMOS) transistors at deep nanometric regime, the microelectronics scientists have focused on designing ultra-miniature OTAs based on non-silicon materials. During the last few years, Gate-All-Around Carbon Nanotube Field Effect Transistors (GAA-CNTFETs) with astonishing electrical and physical properties have drawn extensive attention of nanoelectronics researchers as a potential platform to represent high-performance nanoscale OTAs. In this regard, this work aims to propose an ultra-miniature ultra-wideband OTA based on the 10 nm GAA-CNTFET technology node. The proposed OTA benefits from the ballistic transport operation of the GAA-CNTFET transistors at ultra-scaled dimensions which provide a superior bandwidth (2.88 GHz) along with suitable power consumption (44.8 $$\upmu$$ W). The proposed OTA shows a 64.5 dB open-loop gain and a 59 dB common-mode rejection ratio at a 1 V supply voltage. Moreover, due to the utilization of the indirect feedback compensation method, the proposed GAA-CNTFET-based OTA presents an appropriate phase margin (61 $$^{\circ }$$ ) with a smaller compensator capacitor. With the mentioned performance metrics and occupying only 0.198 $$\upmu {\mathrm{m}^{2}}$$ physical area, the proposed GAA-CNTFET OTA has the potential to be considered as a replacement for nanoscale CMOS-based OTAs.

Performance Analysis of 3GPP NB-IoT Downlink System towards 5G Machine Type Communication (5G-MTC)

5G Technology is the most recent scientific development in wireless communication and it is evolving day by day to meet the demand of near future. As per 3GPP, NB-IoT is chosen as a most promising technology that has been specified for 5G machine type communication (5G-MTC). Since 5G relies on low power wide area networks (LPWAN) and NB-IoT is suitable low power technology in deploying MTC in 5G networks. NB-IoT operates in a licensed spectrum bands and has the potential to guarantee quality of service (QoS). NB-IoT is a specified LPWAN that is based upon system bandwidth of 180 kHz and sub carrier spacing can be considered as 3.75 kHz and 15 kHz as per 3GPP, NB-IoT in downlink system only supports 15 kHz sub carrier spacing. NB-IoT is a top competitor for other low power networks that operates in both licensed and unlicensed spectrum ad 3GPP has specialized NB-IoT as a top priority in 5G networks to support massive machine type communication. In this article, we have studied the technologies for NB-IoT and its implementation in 5G MTC. We also designed a NB-IoT downlink system based on 3GPP guidelines considering sub carrier spacing as 15 kHz and its performance analysis is carried out for MTC scenario. The analysis is performed with two different antenna configurations and compared its performance analysis in terms of BER, FER and QPSK constellation of NPDCCH and NPDSCH after channel estimation. The BER and FER of both NPDCCH and NPDSCH decrease with SNR, resulting the better performance towards machine type communications in 5G.

A Smart On-Line Centralized Coordinated Charging Strategy in Residential Distribution Networks

Environmental and economic aspects encourage the transition of conventional fuel-based vehicles to electric vehicles (EVs). However, the uncoordinated charging activities of EVs may increase the stress on the distribution networks. Coordination between EVs charging activities is the perfect way to avoid the negative consequences of unscheduled charging activities without reinforcing the existing network infrastructure. Many previous works proposed coordinated charging strategies but without considering some influencing factors like EV departure time and energy tariff. Some others used impractical assumptions like a very large parking period or forced the users to choose the preferred charging period before the vehicles' arrival. In this work, a centralized coordinated charging strategy is proposed to reduce EVs charging costs from users’ point of view side by side with the safe operation of the distribution network considering vehicle departure time and charging prices. The proposed strategy mainly determines the proper starting instant and the suitable charger power rate of the charging process. The proper starting instant of the EV charging process is calculated by ranking the charging priority of the arrived vehicles. In contrast, the charging power rate is estimated based on the available duration from starting instant to the instant of vehicle departure. The strategy is applied to a modified IEEE 31 bus residential distribution system with 22 residential distribution feeders. The results proved the proposed strategy’s effectiveness in reducing the charging costs, alleviating overloading on the main substation, improving voltage deviations, and reducing the power loss.

A Hybrid Power System for a Permanent Colony on Mars

Since the dawn of humanity, people have contemplated the sky exploring the firmament. However, it was not until the twentieth century that humans were able to leave Earth and visit other celestial objects. In fact, nowadays, rovers roam Mars on a daily basis pushing the limits of science in a seemingly routine fashion. It is just a matter of time before humanity sets foot on the red planet with the aim of establishing a permanent colony. Such a complex endeavour demands continuous research, simulation, and planning. Consequently, this paper is aimed at starting a proper discussion about the configuration and design of a suitable power system for said Martian outpost. An initial literature review leads to the definition of a reference colony and its growing stages, which is followed by a revision of available energy-related technologies leading to a concrete design of a suitable electrical network. Lastly, the proposed hybrid power system is evaluated in terms of its reliability during the long-term operation under the extreme environmental conditions of Mars. The reference colony starts as an unmanned mission, as robots will prepare the selected location for the first human inhabitants. Later, it suffers several upgrades in size reaching a permanent population of 100 people. Therefore, a holistic approach is needed when designing the power system in order to ensure the continuous supply of the colony. Finally, the selected topology of the colony’s power system is presented.

Research regarding the common problems of design of the bunkers – A review

Understanding the behavior of granular material in a bunker not only helps to design properly and achieve the correct granular flow, but also needs the engineer to ensure that the bunker is properly designed and conducted to withstand the tasks and demands exercised during its operation. Small and shallow bunkers are commonly used in industry when free space is limited. Shallow bunkers induce the flow of the funnel, which can cause problems such as segregation and agglomeration of the material inside it, which leads to considerable damage to the final product. The design and location of a suitable power supply and an appropriate outlet is still critical and is perceived rather as a science. The paper presents some innovative solutions related to the design, modeling and construction of solid material storage and unloading bunkers.

English

English

Effects analysis on soot combustion performance enhancement of an improved catalytic gasoline particulate filter regeneration system with electric heating

The soot combustion performance of catalytic gasoline particulate filter regeneration system (C-GPFs) can be significantly improved by increasing the temperature of gasoline exhaust gas at low-temperature conditions. In this paper, firstly, the soot oxidation rate is introduced as an evaluation index for the combustion performance of C-GPFs, and a suitable electric heating power is defined. Secondly, based on the computational fluid dynamics software, the traditional and improved electric heating C-GPFs combustion performance is compared and analyzed, and the accuracy of the improved electric heating C-GPFs model is verified through experiments. Finally, the effects of critical exhaust parameters on the soot combustion performance and electric energy consumption of the electric heating C-GPFs is studied by numerical simulation. The results of the study show that: the electric energy consumption under the suitable electric heating power is reduced by 49.6% as the exhaust flow rate decreases from 0.023 kg/s to 0.017 kg/s. The electric energy consumption under the suitable electric heating power is reduced by 50.4% as the exhaust temperature increases from 558 K to 588 K. The electric energy consumption under the suitable electric heating power is reduced by 31.6% as the exhaust oxygen concentration increases from 1.6% to 2.4%. The electric energy consumption under the suitable electric heating power is reduced by 34.7% as the exhaust NO concentration increases from 0.08% to 0.12%. Finally, this work provides a direction for improving the soot combustion performance in gasoline engines at low-temperatures.

Families of retractions and families of closed subsets on compact spaces

It is know that the Valdivia compact spaces can be characterized by a special family of retractions called r-skeleton (see [10]). Also we know that there are compact spaces with r-skeletons which are not Valdivia. In this paper, we shall study r-skeletons and special families of closed subsets of compact spaces. We prove that if X is a zero-dimensional compact space and {rs:s∈Γ} is an r-skeleton on X such that |rs(X)|≤ω for all s∈Γ, then X has a dense subset consisting of isolated points. Also we give conditions to an r-skeleton in order that this r-skeleton can be extended to an r-skeleton on the Alexandroff Duplicate of the base space. The standard definition of a Valdivia compact spaces is via a Σ-product of a power of the unit interval. Following this fact we introduce the notion of π-skeleton on a compact space X by embedding X in a suitable power of the unit interval together with a pair (F,φ), where F is family of metric separable subspaces of X and φ an ω-monotone function which satisfy certain properties. This new notion generalize the idea of a Σ-product. We prove that a compact space admits a r-skeleton iff it admits a π-skeleton. This equivalence allows to give a new proof of the fact that the product of compact spaces with r-skeletons admits an r-skeleton (see [9]).

Passively mode-locked cascaded Raman fiber laser in a linear cavity

Passively mode-locked cascaded Raman fiber laser is proposed and demonstrated in a linear cavity. The mode-locking is based on nonlinear polarization rotation (NPR) with a polarization beam splitter (PBS) in the proposed laser. The passively mode-locked Raman fiber laser with a spectral range of 220 nm operates in a low pump power level, and up to the three orders Raman frequency shift are observed under our pump power conditions. The maximum output average power and single pulse energy of the proposed laser are 119.3 mW and 63.97 nJ with a slope efficiency of 41.7%. Multi-pulse mode-locked operation can also be generated by precisely adjusting polarization controller (PC) under suitable pump power conditions.

On principal frequencies and isoperimetric ratios in convex sets

On a convex set, we prove that the Poincare-Sobolev constant for functions vanishing at the boundary can be bounded from above by the ratio between the perimeter and a suitable power of the $N-$dimensional measure. This generalizes an old result by Polya. As a consequence, we obtain the sharp {\it Buser's inequality} (or reverse Cheeger inequality) for the $p-$Laplacian on convex sets. This is valid in every dimension and for every $1<p<+\infty$. We also highlight the appearing of a subtle phenomenon in shape optimization, as the integrability exponent varies.

A Review on Real-Size Epoxy Cast Resin Insulators for Compact High Voltage Direct Current Gas Insulated Switchgears (GIS) and Gas Insulated Transmission Lines (GIL)—Current Achievements and Envisaged Research and Development

Due to the ever-increasing demand for electricity in the one hand and the environmental constraints to use clean energy on the other hand, the global production of energy from remote renewable sources, particularly from large hydropower plants and offshore wind farms and their connection to the grid are expected to grow significantly in the future. Consequently, the demand to carry this electric power by high voltage direct current (HVDC) technology will increase too. The most suitable HVDC power transmission technology to deliver large amounts of power, exceeding a capacity of 5 GW per bipolar system over long distances with lower losses is by using compact HVDC gas insulated transmission lines (DC GIL) and gas insulated switchgears (DC GIS) with rated voltage (maximum continuous operating voltage) of ±550 kV and 5000 A which are presently under development worldwide. Among the critical challenges for the development of these HVDC gas insulated systems, there are the epoxy cast resin insulators that are used to separate gas compartments also called spacers. Indeed, thorough research studies have been and still being carried out to well understand and clarify the electrical insulation characteristics of HVDC spacers using mainly cylindrical samples and small insulator models, where useful results have been obtained and proposed for implementation in real compact gas insulated systems. However, few practical investigations have been undertaken on real size spacers (product scale) to verify such research outcomes and validate the reliability of the spacers to collect experiences or for commercial use. This paper reviews the current achievements of real size HVDC spacers development. It describes the basic electric field calculation and spacers design, the verification of the insulation performance and validation testing. It gives today’s commercially available compact HVDC GIS/GIL and finally it presents the envisaged future research and development.