Conversion Unit Research Articles

An improved energy management operation strategy for integrating adiabatic compressed air energy storage with renewables in decentralized applications

Adiabatic compressed air energy storage (A-CAES) has shown great application potentials in integrated hybrid energy systems (HES) in recent years. The integration requires A-CAES to store intermittent renewables power to meet the fluctuating load demand. Therefore, the operation of compressors and turbines must be adjusted by renewable power output and load demand, respectively. This paper presents an improved energy management operation strategy (I-EMOS) to enhance the A-CAES system's utilization for decentralized applications. In doing so, besides integrating thermal energy storage (TES) unit into CAES, several limitations of an A-CAES unit, such as its conversion process mode, dynamic characteristics, power input/output constraints of compressor/turbine train, air pressure constraint, and thermal storage capacity limitations are considered. An HES consisting of PV, A-CAES, and grid to answer the building's electric demand is simulated. The results are validated against data from an existing A-CAES pilot. It is concluded that adopting features and capacity limitations of the A-CAES system's power conversion unit in operational strategies contributes to improved management of energy flow in HES. It is observed that for certain air tank volume and maximum/minimum pressures under I-EMOS, an enhanced performance can be achieved. This analysis presents a feasibility assessment approach for decentralized A-CAES integrated with renewables implemented and tested in a real-world case study.

Compass: Supporting Large Group Mentorship in a Chat-Based UI

While mentorship offers many benefits, student access to mentorship is often limited. In this paper, we introduce Compass, a chat platform where industry professionals mentor large cohorts of 30+ students with the support of novel features that enable full engagement without the typical chaos of group chat. Specifically, we conceptualize conversations as composed of not only individual messages, but also multi-person conversational units that collapse large numbers of small but related conversational exchanges into single conceptual units in the main dialogue. Doing so makes it possible to preserve a coherent linear flow of conversation while also supporting non-linear conversational exchanges that can be concisely summarized computationally and built on in the main conversation. We report on design lessons learned over a year of small real-world studies culminating in a final deployment in which 2 industry professionals successfully mentored 30+ students over a 10-week period. We find that both mentors and mentees find the chat UI effective and sometimes preferable, and discuss broader implications for the design of chat UI for large group conversations.

Application of nanomaterial based alkaline electrolyzer for hydrogen production in renewable energy-driven system: Multi-criteria assessment, environmental and exergoeconomic approaches

An alkaline electrolyzer is a traditional equipment to generate hydrogen. Improving the yield of electrolyzers has recently captured much attention. In this regard, the utilization of carbon-coated nanomaterial structures is a state-of-art method. On the other hand, considering the current crisis of fossil energies, the exploitation of renewables and green technologies is necessary and unavoidable. Additionally, the design and development of integrated energy systems with two or more output products and the maximum usage of thermal losses to enhance productivity can increase the flexibility and acceptability of the energy system. In this regard, the current paper develops a framework for the performance of a new solar and biomass energies-driven multigeneration system (MGS). The main units installed in MGS are three electric energy generation units based on a gas turbine process, a solid oxide fuel cell unit (SOFCU) and an organic Rankine cycle unit (ORCU), a biomass energy conversion unit to useful thermal energy, a seawater conversion unit into useable freshwater, a unit for converting water and electricity into hydrogen energy and oxygen gas via a nanomaterial-based alkaline electrolyzer, a unit for converting solar energy into useful thermal energy (based on Fresnel collector), and a cooling load generation unit. The planned MGS has a novel structure and layout that has not been considered by researchers in previous papers. The current article is based on presenting a multi-aspect evaluation in order to investigate thermodynamic-conceptual, environmental and exergoeconomic analyzes. The outcomes indicated that the planned MGS can produce about 6.31 MW of electrical power and 0.49 MW of thermal power. Furthermore, MGS is able to produce various products such as potable water (∼0.977 kg/s), cooling load (∼0.16 MW), hydrogen energy (∼1.578 g/s) and sanitary water (∼0.957 kg/s). The overall energy and exergy productivities were measured as 78.13% and 47.72%, respectively. Also, the total investment and unit exergy costs were 47.16 USD per hour and 11.07 USD per GJ, respectively. Further, the content of carbon dioxide released from the planned system was equal to 10.59 kmol per MWh. A parametric study has been also developed to identify influencing parameters.

Designing a Multi-Output Power Supply for Multi-Electrode Arc Welding

Multi-output power converters using different architectures can have significant efficiency advantages. This paper proposes a multi-output welding power supply that is based on the middle DC converter distributed architecture. This machine includes two converter groups, and each group comprises a three-phase rectifier unit, a full-bridge converter unit, a HF (high frequency) transformer, a rectifier unit, and a chopper converter unit. Among these units, the three-phase rectifier unit, full-bridge converter unit, HF transformer, and rectifier unit convert three-phase AC voltage into a low voltage, and the chopper converter unit converts the low voltage into the required current. The welding power supply can output four DC and two AC currents. This paper also analyzes the stability of the welding power supply. Finally, a prototype is designed and verified through experiments, and the maximum output of the prototype is 300 A. The experimental results show that the converter can output different DC and AC currents according to the requirement, the multiple outputs are independent of the others, and the output phase and value are independently adjustable. After verification, the proposed multi-output welding power supply can output steady current according to the requirement.

ソフトウェア構造情報と動作ログを活用した企業情報システムの実装言語刷新支援方式

Legacy enterprise information systems are required to convert their implementation languages into modern languages to enhance their maintainability. However, in a planning phase, it is difficult for engineers to identify units of programs to be converted appropriately and quickly. In this paper, we propose a support method that can effectively identify the units of programs for language conversion and test data acquisition points by relating application logs to software structure. We implemented this method by using graph database, and through the application of this method to real enterprise information system, we confirmed that we can effectively identify units of program conversion and test data acquisition points.

High-Activity Fe3 C as pH-Universal Electrocatalyst for Boosting Oxygen Reduction Reaction and Zinc-Air Battery.

Transition metal catalysts are regarded as one of promising alternatives to replace traditional Pt-based catalysts for oxygen reduction reaction (ORR). In this work, an efficient ORR catalyst is synthesized by confining Fe3 C nanoparticles into N, S co-doped porous carbon nanosheets (Fe3 C/N,S-CNS) via high-temperature pyrolysis, in which 5-sulfosalicylic acid (SSA) demonstrates as an ideal complexing agent for iron (ΙΙΙ) acetylacetonate while g-C3 N4 behaves as a nitrogen source. The influence of the pyrolysis temperature on the ORR performance is strictly examined in the controlled experiments. The obtained catalyst exhibits excellent ORR performance (E1/2 = 0.86V; Eonset = 0.98V) in alkaline electrolyte, coupled by exhibiting the superior catalytic activity and stability (E1/2 = 0.83V, Eonset = 0.95V) to Pt/C in acidic media. In parallel, its ORR mechanism is carefully illustrated by the density functional theory (DFT) calculations, especially the role of the incorporated Fe3 C played in the catalytic process. The catalyst-assembled Zn-air battery also exhibits a much higher power density (163mW cm-2 ) and ultralong cyclic stability in the charge-discharge test for 750h with a gap increase down to 20mV. This study provides some constructive insights for preparation of advanced ORR catalysts in green energy conversion units correlated systems.

A study of a modified design of dumbbell-shaped flux switching tubular linear generator for regular wave energy conversion

Wave energy converters (WEC) use indirect drive hydraulic or turbine-type power take-off (PTO) mechanisms which consist of many moving parts, creating mechanical complexity and increasing the installation and maintenance costs. Linear generator-based direct drive wave energy converters could be a solution to overcome this problem, but the efficiency of the single conventional linear generator is not high enough, and it cannot work satisfactorily in the low-frequency range.In this paper, a novel dumbbell-shaped flux-switching linear generator has been proposed and studied as a power take-off unit for ocean wave energy conversion. The linear generator has a dumbbell-shaped stator, and the design is ameliorated by placing the permanent magnet rings of longitudinally alternating magnetic pole directions in the slots of its stator outer surface and is separated by thin wall steel ring shoulders. The linear generator also has a dumbbell-shaped translator. The stator is hollow where the translator slides inside axially inducing current in the coil. A long permanent magnet is inserted inside the hollow steel dumbbell core of the translator and a copper coil is wound around the outer surface of the moving translator core. The addition of permanent magnets on the outer slots of the stator is found to increase the output power significantly. To facilitate the investigation, the modified generator design has been compared to the conventional linear permanent magnet generator for their performances using the finite element method, as both machines are different in their structures. The results show that the double dumbbell-shaped flux-switching linear generator gives higher power output, magnetic flux density, branch current, and induced voltage. The double dumbbell-shaped flux-switching linear generator is then placed in a cylindrical buoy and investigated in a wave energy converter in the ocean environment. The hydrodynamic response of the cylindrical buoy has been investigated through ANSYS AQWA. The dynamic differential equations of the wave energy converter have been developed and solved for regular waves using Matlab codes. The peak output voltage, power, and the relative displacement of the linear generator translator with respect to the stator fixed with the buoy have been calculated through the Fourier Transform in the frequency domain using a Matlab code and through numerical integrations in the time domain using a Matlab Simulink code. The results in the time and frequency domains are compared and verified with each other. The relative displacement between the translator and stator buoy has been used as motion input of the ANSYS Maxwell simulation model, and the output voltage results of the ANSYS Maxwell simulation model have been compared and verified with those of the Matlab simulation models. The linear generator design in the wave energy converter under the regular wave excitation is further optimized for the maximum ratio of the peak output power to peak cogging force using the central composite design-based response surface method (RSM). The ANOVA analysis is used to validate the response surface model where its R2 coefficient of 99.93% has indicated an excellent fit. The methods and results differ from those presented in previous studies.

Fuzzy-Based Efficient Control of DC Microgrid Configuration for PV-Energized EV Charging Station

Electric vehicles (EVs) are considered as the leading-edge form of mobility. However, the integration of electric vehicles with charging stations is a contentious issue. Managing the available grid power and bus voltage regulation is addressed through renewable energy. This work proposes a grid-connected photovoltaic (PV)-powered EV charging station with converter control technique. The controller unit is interfaced with the renewable energy source, bidirectional converter, and local energy storage unit (ESU). The bidirectional converter provides a regulated output with a fuzzy logic controller (FLC) during charging and discharging. The fuzzy control is implemented to maintain a decentralized power distribution between the microgrid DC-link and ESU. The PV coupled to the DC microgrid of the charging station is variable in nature. Hence, the microgrid-based charging is examined under a range of realistic scenarios, including low, total PV power output and different state of charge (SOC) levels of ESU. In order to accomplish the effective charging of EV, a decentralized energy management system is created to control the energy flow among the PV system, the battery, and the grid. The proposed controller’s effectiveness is validated using a simulation have been analyzed using MATLAB under various microgrid situations. Additionally, the experimental results are validated under various modes of operation.

Multiple input self-organizing-map ResNet model for optimization of petroleum refinery conversion units

Multiple input self-organizing-map ResNet model for optimization of petroleum refinery conversion units

A Single-Stage Bridgeless Isolated AC–DC Conversion System for Light Electric Vehicles Charging Application

A 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\phi $ </tex-math></inline-formula> single-stage ac–dc power conversion unit employing bridgeless isolated modified single-ended primary inductor converter (BLIMSEPIC) is presented in this work for the light electric vehicles (LEVs) charger applications. Unlike the existing SEPIC and Cuk high-power factor (HPF) ac–dc converters, the presented BLIMSEPIC HPF ac–dc converter incorporates continuous input and output current features while operating under discontinuous current mode (DCM) condition. Therefore, it demonstrates excellent applicability in charging applications. The DCM operation considerably simplifies overall control architecture, as the presented BLIMSPEIC ac–dc converter exhibits inherent power factor correction capability under DCM operation, and therefore, significantly reduces the cost of control implementation. Besides, the continuous input and output currents attribute lessen the filter’s size and associated losses. Furthermore, the reduced voltage stress and zero current switching of semiconductor devices, together with the front-end bridgeless structure, considerably improve the conduction and switching losses of the charger. The operation, design, control, and performance of the BLIMSEPIC HPF ac–dc converter are experimentally verified, and corresponding results are presented to justify its efficacy for LEVs charging applications.

Rolling stand electric drive model regarding influence of power supply network parameters

&lt;span lang="EN-US"&gt;Operation mode of hot rolling mill finishing group stands of ArcelorMittal Temirtau JSC electric drives along with thyristor converter units, intended for the drives supply effect significantly the power network parameters. While being carried out the experimental research on operating modes of power network supplying the rolling mill, some oscillograms were constructed that indicate voltage during the rolling process. Analyzing the oscillograms it appears that there are unacceptable voltage drops throughout the network (more than 10%), that, in its turn, effects negatively the main and auxiliary electric drives functioning. Electric drive simulation model have been constructed with the aim accomplishment to learn more about operating modes features of finishing group stands electric drives as well as power network supplying the hot rolling mill, where the main objective is getting the decreased parameters of their mutual influence. The scientific project purpose is verification of the mathematical model choice correctness, construction of a simulation model of the electric drive control system for the main drives of the hot rolling mill stands, taking into consideration the parameters of the power supply network and checking its adequacy.&lt;/span&gt;

Four-channel all-optical wavelength conversion unit based on nonlinear effect of three-section monolithically integrated semiconductor lasers.

A simple and highly efficient four-channel all-optical wavelength conversion based on four-wave mixing effect of the directly modulated three-section monolithically integrated semiconductor laser is proposed and experimentally investigated. For this wavelength conversion unit, the spacing of the wavelength can be adjusted by tuning the bias current of the lasers and setting it to be 0.4nm (50GHz) as a demonstration is this work. A 50Mbps 16-QAM signal centers at 4-8GHz is experimentally switched to a targeted path. Up- or downconversion depends on a wavelength-selective switch, and the conversion efficiency can reach up to -2 to 0dB. This work provides a new technology for photonic radio-frequency switching matrix and contributes to the integrated implementation of satellite transponders.

Dual Mode Strain–Temperature Sensor with High Stimuli Discriminability and Resolution for Smart Wearables

AbstractStrain and temperature are important physiological parameters for health monitoring, providing access to the respiration state, movement of joints, and inflammation processes. The challenge for smart wearables is to unambiguously discriminate strain and temperature using a single sensor element assuring a high degree of sensor integration. Here, a dual‐mode sensor with two electrodes and tubular mechanically heterogeneous structure enabling simultaneous sensing of strain and temperature without cross‐talk is reported. The sensor structure consists of a thermocouple coiled around an elastic strain‐to‐magnetic induction conversion unit, revealing a giant magnetoelastic effect, and accommodating a magnetic amorphous wire. The thermocouple provides access to temperature and its coil structure allows to measure impedance changes caused by the applied strain. The dual‐mode sensor also exhibits interference‐free temperature sensing performance with high coefficient of 54.49 µV °C−1, low strain and temperature detection limits of 0.05% and 0.1 °C, respectively. The use of these sensors in smart textiles to monitor continuously breathing, body movement, body temperature, and ambient temperature is demonstrated. The developed multifunctional wearable sensor is needed for applications in early disease prevention, health monitoring, and interactive electronics as well as for smart prosthetics and intelligent soft robotics.

A New Wave Energy Converter for Marine Data Buoy

Providing stable and reliable power supply for offshore equipment with special power requirements, such as marine data platforms and marine buoys far away from the coast is currently topical research issue. At present, most of these devices use photovoltaic power generation or install high-capacity batteries and carry out regular replacement of electricity supply schemes. Due to the high dependence of photovoltaic power generation on solar radiation and the high cost arising from frequent battery replacements, wave energy is considered as a solution. Wave energy converters (WECs) are devices that convert the energy stored in waves into electrical energy, and its main advantage is the sustainable supply of electricity. In this article, a new built-in wave energy converter with high reliability and low maintenance costs is proposed and investigated for marine data buoys. Its core is a direct-drive energy conversion unit based on a magnetic lead screw design. The device can passively follow the pitching state of the buoy under the impact of waves to maximize its power generation. The proposed WEC is introduced and investigated through model analysis and prototype experiments. The experimental results confirm the power generation performance of a 50 kg power generation prototype and show the advantages of the proposed device.

PREFERRED AND DISPREFERRED SECOND PARTS OF QUESTION-ANSWER ADJACENCY PAIRS

The present article is devoted to the study of adjacency pairs as units of conversation organization in modern English. The choice of the topic is conditioned by the rising interest to the linguistic studies of conversation organization. Thus, the purpose of the research has been the examination of the function of adjacency pairs as conversational units. The aim of the study was to discover how adjacency pairs function in and assist to the organization of conversation. In addition the analysis of semantics and pragmatics of adjacency pairs with preferred and dispreferred second parts was carried out.

Remote‐Controlled Droplet Chains‐Based Electricity Generators

AbstractHarnessing ambient renewable mechanical energies for achieving carbon‐neutrality demands the rational design of materials and architectures which are favorable for both energy collection and conversion simultaneously. However, the direct coupling of energy collection and conversion modules leads to many unwanted problems such as material wearing, the spatial constraint for large‐scale integration, and low energy conversion efficiency. Herein, a remote‐controlled energy harvesting strategy that cleverly harnesses the unique advantage of diffusive, long‐range airflow within a confined capillary channel is developed. The reported device separates the energy collection unit, made of an elastic cavity that directly transforms external mechanical motion to pneumatic motion, from the conversion units, made of encapsulated droplet chains that serve to translate their recurring motion within the capillary channel into electrical output. In contrast to single‐drain electrode design for electricity generation from fresh droplets in open spaces, two drain electrodes are designed to collect and release electrostatically induced charges from recurring droplets in the confined channel, respectively, thereby eliminating unwanted charge accumulation on recurring droplets and leading to efficient output performance. The integration of multiple electricity generation units with such a two‐drain electrode architecture with a single energy collector improves the design resilience and relaxes the spatial limitation.

An impedance matrix model of DFIG for harmonic power flow analysis considering DC-link dynamics

The doubly-fed induction generator (DFIG) has been increasingly used in modern power systems for interfacing wind energies.Because of the nonlinear characteristics of the DFIG, it is important to properly model the DFIG when conducting harmonic analysis in power systems. This is especially important for low-order harmonics that are routinely encountered by present power systems. Therefore, this paper presents a model of DFIG for harmonic power flow analysis. The harmonic model of the back-to-back converters, i.e., the combined rotor-side converter (RSC) and grid-side converter (GSC) unit, is first established through mathematical derivations, and the result shows that it can be represented by a coupled impedance matrix, which includes the harmonic coupling between the RSC and the GSC and coupling between different harmonics. The studies also show that the coupling between different harmonics is negligible; thus, a simplified 2 × 2 impedance matrix can be practically used with confidence. After integrating with the induction generator model, a full harmonic model of DFIG can be obtained through circuit analyses. The correctness of the developed model has been verified using EMT simulations and lab experiments. The new model fills in a gap in the modeling of renewable energies for harmonic power flow analysis.

A portable colorimetric point-of-care testing platform for MicroRNA detection based on programmable entropy-driven dynamic DNA network modulated DNA-gold nanoparticle hybrid hydrogel film

Point-of-care testing (POCT) platforms for microRNA (miRNA) detection have attracted considerable attention in recent years, due to the increasingly important role of miRNA as biomarkers for the diagnosis of many diseases, such as cancers. However, several limitations such as the requirement of enzyme-related amplification system, expensive preservation cost, sophisticated analysis instruments and tedious operations of conventional miRNA biosensing devices severely hinder their widespread applications. In this work, a portable and smart colorimetric analysis platform was developed by employing the ultrathin DNA-gold nanoparticle (AuNP) hybrid hydrogel film as the signaling unit and the enzyme-free entropy-driven dynamic DNA network (EDN) as the signal converter and amplification unit. By programming the DNA sequences of the EDN, the EDN could respond to a specific miRNA, with miRNA-155 or miRNA-21 as the model target, and release a converter DNA with amplified concentration to further trigger the release of AuNPs from the hydrogel film as a colorimetric signal output. To avoid the use of sophisticated spectral instruments, digital analysis based on primary three-color channel (R/G/B) was further introduced by using user-friendly camera and image processing software, and a detection limit at pM level was achieved. Moreover, by introducing H2O2-mediated AuNPs enlargement procedure in the colorimetric analysis platform, the detection limit for miRNA target could further be enhanced to fM level. The POCT platform is also portable and storable with a good storage stability for at least 45 days, suggesting its great potential in practical diagnosis applications.

Review on power conversion unit of noble gas closed Brayton cycle for space and underwater applications

The closed Brayton cycle (CBC) has become a promising solution for the high-energy density power conversion unit in underwater and space applications. Differing from the design requirements of the grounded plant, the CBC in the underwater application gives priority to the compact size. Therefore, there is a need to provide a summary of the current research, particularly on working fluid and turbomachinery, with the view to obtaining the strategies adopted in power conversion unit to meet the design requirements of the underwater and space application. This paper presented the comprehensive considerations behind the selection of helium as the ideal working fluids for underwater and space applications and reviews the various predictions methods of the unacquainted physical properties of noble gas, among which the method pertaining to the Chapman-Enskog kinetic theory and the law of the corresponding state is more precise with the comprehensive accuracies of 2% for pure gas and 5% for the binary mixture. The studies on the characteristics of noble gas to support the application feasibility of the existing aerodynamic method to it were also reviewed. Two strategies to reduce the size of the power conversion unit, based on highly-loaded design and He-Xe turbomachinery design, were presented. Through the strategies, the stage number of the compressor under the given pressure ratio can reduce by about 75% compared with the prototype. Moreover, the paper also paid an attention to the similarity modeling method in the performance map of turbomachinery between the noble gas and air. Based on the review, the current problems encountered and the expected future breakthroughs were highlighted.

Three-Port Bi-Directional DC–DC Converter with Solar PV System Fed BLDC Motor Drive Using FPGA

The increased need for renewable energy systems to generate power, store energy, and connect energy storage devices with applications has become a major challenge. Energy storage using batteries is most appropriate for energy sources like solar, wind, etc. A non-isolated three-port DC–DC-converter energy conversion unit is implemented feeding the brushless DCmotor drive. In this paper, a non-isolated three-port converter is designed and simulated for battery energy storage, interfaced with an output drive. Based on the requirements, the power extracted from the solar panel during the daytime is used to charge the batteries through the three-port converter. The proposed three-port converter is analyzed in terms of operating principles and power flow. An FPGA-based NI LabView PXI with SbRio interface is used to develop the suggested approach’s control hardware, and prototype model results are obtained to test the proposed three-port converter control system’s effectiveness and practicality. The overall efficiency of the converter’s output improves as a result. The success rate is 96.5 percent while charging an ESS, 98.1 percent when discharging an ESS, and 95.7 percent overall.