bluuebunny/crossref_metadata_2025 huggingface dataset:
Joint Power and Time Allocation in Hybrid NoMA/OMA IoT Networks for Two-Way Communications
Authors: Chen Dong-Hua , Jiang En-Hua
Published: November 2022

This article investigates two-way communications between an access point (AP) and multiple terminals in low-cost Internet of Things (IoT) networks. The main issues considered are the asymmetric transmission traffic on the uplink (UL) and downlink (DL), and the unbalanced receivers processing capability at the AP and the terminals. As a solution, a hybrid non-orthogonal multiple access/orthogonal multiple access (NoMA/OMA) scheme together with a joint power and time allocation method is proposed to address these issues. For the system design, we formulated the optimization problem with the aim of minimizing the system power and satisfying the UL and DL transmission rate constraints. Due to the coupling of power and time variables in the objective function and the multi-user interference (MUI) in the UL transmission rate constraints, the formulated problem is shown to be non-linear and non-convex and thus is hard to solve. To obtain a numerical, efficient solution, the original problem is first reformulated to be a convex one relying on the successive convex approximation (SCA) method, and then a numerical efficient solution is thus obtained by using an iterative routine. The proposed transmission scheme is shown to be not only physically feasible but also power-efficient.
Broadcast Approach to Uplink NOMA: Queuing Delay Analysis
Authors: Zohdy Maha , Tajer Ali , Shamai (Shitz) Shlomo
Published: November 2022

Emerging wireless technologies are envisioned to support a variety of applications that require simultaneously maintaining low latency and high reliability. Non-orthogonal multiple access techniques constitute one candidate for grant-free transmission alleviating the signaling requirements for uplink transmissions. In open-loop transmissions over fading channels, in which the transmitters do not have access to the channel state information, the existing approaches are prone to facing frequent outage events. Such outage events lead to repeated re-transmissions of the duplicate information packets, penalizing the latency. This paper proposes a multi-access broadcast approach in which each user splits its information stream into several information layers, each adapted to one possible channel state. This approach facilitates preventing outage events and improves the overall transmission latency. Based on the proposed approach, the average queuing delay of each user is analyzed for different arrival processes at each transmitter. First, for deterministic arrivals, closed-form lower and upper bounds on the average delay are characterized analytically. Secondly, for Poisson arrivals, a closed-form expression for the average delay is delineated using the Pollaczek-Khinchin formula. Based on the established bounds, the proposed approach achieves less average delay than single-layer outage approaches. Under optimal power allocation among the encoded layers, numerical evaluations demonstrate that the proposed approach significantly minimizes average sum delays compared to traditional outage approaches, especially under high arrival rates.
The Struggle between Cash and Electronic Payments
Authors: Pintér Zsófia , Nagy Mónika Zita , Tóth Katalin , Varga József
Published: November 2022

The assessment of consumer behavior regarding the choice of financial instruments may be extremely important in the near future, since the fight between cash and electronic money has reached a turning point, and electronic payments are slowly defeating cash. On one hand, in the long term, this possible separation threatens sustainable development goals, and on the other hand, financial awareness can affect the number of purchases and savings. In a survey of 499 people, we examined the reasons behind their decisions, with a particular focus on financial awareness. The result shows that the vast majority of Hungarian consumers are not yet ready to fully accept electronic payments. It can be stated that financial awareness is not present at all in one-fifth of respondents, and one-third are influenced by habituation in everyday shopping situations, which indicates a lack of financial awareness. Based on our results, we have concluded that our consumers still find it difficult to abandon cash payments. Financial awareness needs to be improved in parallel with the Hungarian government’s strategy to reduce the use of cash.
Zero-Tolerance Security Paradigm for Enterprise-Specific Industrial Internet of Things
Authors: Tariq Usman
Published: November 2022

The complex industrial environment of the 21st century is equipped with the Internet of Things platform, with the objective of real-time operational visibility, improved device management and predictive maintenance. To unleash the focused importance of its policy, a secure connectivity must be realized through a range of existing and dissimilar devices and data sources. During the conceptualization phase, the authors aimed to compel the following: (a) that restriction of access should be based on the presence of unexpected device actions that may point to a security breach, and (b) ensure the safety of the system by constant tracking of connected devices and data. In this paper, a policy-driven, zero-trust defense model is proposed to address numerous vulnerable entry points, validate device access to legitimate enterprise functions, quarantine unsecure devices, and trigger automated warnings and policy validation for hardware, software, network connectivity and data management. To handle active scanning, bots, passive auditing, outbound threat management, and device interconnections, an experimental environment was put up. This environment provides holistic visibility and a persistent view of all resources, including those that were previously unknown. A steady stream of reliable and authenticated data has helped to develop and adjust a scalable implementation strategy by avoiding recognized anomalous traps. Actual data was aggregated and analyzed to assess the proposed methodology. Comparative analysis of ‘device exposure view, attack path analysis, controlled view of devices, comprehensive vulnerability evaluation, and effective communication of cyber risk’ has proved the effectiveness of the proposed methodology.
Empirical Evidence on the Development and Digitalization of the Accounting and Finance Profession in Europe
Authors: Ionescu-Feleagă Liliana , Dragomir Voicu D. , Bunea Ștefan , Stoica Oana Cristina , Barna Laura-Eugenia-Lavinia
Published: November 2022

The objective of this research was to evaluate the development and digitalization of professional services in the field of accounting and finance, as well as to calculate and compare several indicators of the development of the profession in each European country. We also sought to identify the factors that drive the development of the accounting and finance profession at the international level. We collected rich information on 337 professional associations in 40 countries in Europe. Using this dataset, 20 accounting and finance services and 14 membership services and benefits provided by professional associations were identified. Digitalization of the profession is a prominent membership service, but also a characteristic of country competitiveness. The results of the intergroup analysis showed that high-income countries have a significantly larger number of professional associations and services compared to middle-income countries. Furthermore, the accounting and finance profession in high-income countries covers a larger number of accounting and membership services. The size of the population and the competitiveness of the national economy are the main predictors of the development and digitalization of the accounting and finance profession in a country. This research has implications for professional associations and national regulators in reducing disparities between European countries on the matter of accounting education and service quality. The scale of this research can provide institutional actors with a holistic perspective on the accounting and finance profession at the national and international level.
The Characteristics of the Second and Third Virtual Cathodes in an Axial Vircator for the Generation of High-Power Microwaves
Authors: Mumtaz Sohail , Choi Eun-Ha
Published: November 2022

A virtual cathode oscillator or vircator is a vacuum tube for producing high-power microwaves (HPM). The efficiency of the vircator has been a difficult task for decades. The main reasons for low efficiency are intense relativistic electron beam (IREB) loss and few or no interactions between IREB and HPM. In this case, forming multiple virtual cathodes may be beneficial in overcoming these constraints. By reusing the axially propagating leaked electrons (LE), we could confine them and form multiple virtual cathodes (VCs). This article discussed the characteristics of newly formed VCs based on simulation results. The formation time of new VCs was discovered to be highly dependent on the reflector position and the density of LE approaching their surfaces. Furthermore, multiple VC formation in the waveguide region does not affect conventional VCs’ position or forming time. The emission mode of the generated HPM was TM01 with single and multiple VCs and remained unaffected. The formation of multiple VCs positively influenced the axial and radial electric fields. When compared to a single VC, the axial and radial electric field increased 25.5 and 18 times with multiple VCs. The findings suggested that forming multiple VCs could be a future hope for achieving high vircator efficiency.
Mitigating Adverse Impacts of Increased Electric Vehicle Charging on Distribution Transformers
Authors: Jain Akansha , Karimi-Ghartemani Masoud
Published: November 2022

As the world is transitioning to electric vehicles (EVs), the existing power grids are facing several challenges. In particular, the additional charging power demand may repeatedly overload the traditionally-sized distribution transformers and adversely impact their operational life. To address this challenge, this paper proposes an EV-based reactive power compensation strategy for transformer overloading mitigation. Specifically, a low-bandwidth centralized recursive controller is proposed to determine a set point for the EV’s onboard charger’s reactive power. Importantly, the proposed strategy is practically implementable in existing distribution grids as it does not rely on smart grid infrastructure and is stable under potential communication delays and partial failures. This paper discusses the controller’s structure, design, and stability in detail. The proposed solution is tested with a realistic secondary distribution system considering four different EV charging scenarios with both Level 1 and Level 2 residential EV charging. Specifically, IEEE Standard C57.91-2011 is used to quantify the impact of EV charging on the transformer’s life. It is shown that with the proposed method, transformer overloading is significantly reduced, and the transformer’s life improves by an average of 47% over a year in all four scenarios.
Multi-Objective Optimal Scheduling of a Microgrid Using Oppositional Gradient-Based Grey Wolf Optimizer
Authors: Rajagopalan Arul , Nagarajan Karthik , Montoya Oscar Danilo , Dhanasekaran Seshathiri , Kareem Inayathullah Abdul , Perumal Angalaeswari Sendraya , Lakshmaiya Natrayan , Paramasivam Prabhu
Published: November 2022

Optimal energy management has become a challenging task to accomplish in today’s advanced energy systems. If energy is managed in the most optimal manner, tremendous societal benefits can be achieved such as improved economy and less environmental pollution. It is possible to operate the microgrids under grid-connected, as well as isolated modes. The authors presented a new optimization algorithm, i.e., Oppositional Gradient-based Grey Wolf Optimizer (OGGWO) in the current study to elucidate the optimal operation in microgrids that is loaded with sustainable, as well as unsustainable energy sources. With the integration of non-Renewable Energy Sources (RES) with microgrids, environmental pollution is reduced. The current study proposes this hybrid algorithm to avoid stagnation and achieve premature convergence. Having been strategized as a bi-objective optimization problem, the ultimate aim of this model’s optimal operation is to cut the costs incurred upon operations and reduce the emission of pollutants in a 24-h scheduling period. In the current study, the authors considered a Micro Turbine (MT) followed by a Wind Turbine (WT), a battery unit and a Fuel Cell (FC) as storage devices. The microgrid was assumed under the grid-connected mode. The authors validated the proposed algorithm upon three different scenarios to establish the former’s efficiency and efficacy. In addition to these, the optimization results attained from the proposed technique were also compared with that of the results from techniques implemented earlier. According to the outcomes, it can be inferred that the presented OGGWO approach outperformed other methods in terms of cost mitigation and pollution reduction.
An Enhanced Second-Order Cone Programming-Based Evaluation Method on Maximum Hosting Capacity of Solar Energy in Distribution Systems with Integrated Energy
Authors: Wang Chunyi , Luo Fengzhang , Jiao Zheng , Zhang Xiaolei , Lu Zhipeng , Wang Yanshuo , Zhao Ren , Yang Yang
Published: November 2022

In order to adjust to the change of the large-scale deployment of photovoltaic (PV) power generation and fully exploit the potentialities of an integrated energy distribution system (IEDS) in solar energy accommodation, an evaluation method on maximum hosting capacity of solar energy in IEDS based on convex relaxation optimization algorithm is proposed in this paper. Firstly, an evaluation model of maximum hosting capacity of solar energy for IEDS considering the electrical-thermal comprehensive utilization of solar energy is proposed, in which the maximization of PV capacity and solar collector (SC) capacity are fully considered. Secondly, IEDS’s potential in electricity, heat, and gas energy coordinated optimization is fully exploited to enhance the hosting capacity of solar energy in which the electric distribution network, heating network, and natural gas network constraints are fully modeled. Then, an enhanced second-order cone programming (SOCP)-based method is employed to solve the proposed maximum hosting capacity model. Through SOCP relaxation and linearization, the original nonconvex nonlinear programming model is converted into the mixed-integer second-order cone programming model. Meanwhile, to ensure the exactness of SOCP relaxation and improve the computation efficiency, increasingly tight linear cuts of distribution system and natural gas system are added to the SOCP relaxation. Finally, an example is given to verify the effectiveness of the proposed method. The analysis results show that the maximum hosting capacity of solar energy can be improved significantly by realizing the coordination of an integrated multi-energy system and the optimal utilization of electricity, heat, and gas energy. By applying SOCP relaxation, linearization, and adding increasingly tight linear cuts of distribution system and natural gas system to the SOCP relaxation, the proposed model can be solved accurately and efficiently.
Social Innovation, Circularity and Energy Transition for Environmental, Social and Governance (ESG) Practices—A Comprehensive Review
Authors: Popescu Catalin , Hysa Eglantina , Kruja Alba , Mansi Egla
Published: November 2022

It has been extensively debated how social innovation, circularity, and energy transition may all be considered environmental, social, and governance (ESG) components from a sustainability perspective. To comprehend the conceptual development of this subject in the academic literature, few studies, however, tackle the problems above by reviewing earlier research on the subject. By developing the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) technique, this study aims to address the current and anticipated advancements in social innovation, energy transition, and circularity. As a result, we create two metasynthesis analyses related to “social innovation–energy transition” and “social innovation–circularity.” In the first analysis, the three databases Web of Science, Scopus, and JSTOR had a total of 1767 studies and reports, and in the second analysis, we reviewed the work from a total of 466 studies and reports. We emphasize that implementing environmental, social, and governance (ESG) practices require social innovation, circularity, and energy transition. The study’s key contributions are the five cluster themes classification for the two metasynthesis analyses, which point to potential future directions for both firms and governments to pursue some macro-level goals concerning energy transition and circularity through social innovation.
Formation of Yolk–Shell MoS2@void@Aluminosilica Microspheres with Enhanced Electrocatalytic Activity for Hydrogen Evolution Reaction
Authors: Li Li , Zhao Yuanyuan , Qiao Nanli , Yu Zhengbao , Zhang Yongxing
Published: November 2022

The development of low-cost electrode materials with enhanced activity and favorable durability for hydrogen evolution reactions (HERs) is a great challenge. MoS2 is an effective electrocatalyst with a unique layered structure. In addition, aluminosilica shells can not only provide more hydroxyl groups but also improve the durability of the catalyst as a protective shell. Herein, we have designed a hard-template route to synthesize porous yolk–shell MoS2@void@Aluminosilica microspheres in a NaAlO2 solution. The alkaline solution can directly etch silica (SiO2) hard templates on the surface of MoS2 microspheres and form a porous aluminosilica outer shell. The electrocatalytic results confirm that the MoS2@void@Aluminosilica microspheres exhibit higher electrocatalytic activity for HERs with lower overpotential (104 mV at the current density of −10 mA cm−2) and greater stability than MoS2 microspheres. The superior electrocatalytic activity of MoS2@void@Aluminosilica microspheres is attributed to the unique structure of the yolk@void@shell geometric construction, the protection of the aluminosilica shell, and the greater number of active sites offered by their nanosheet subunits. The design of a unique structure and new protection strategy may set up a new method for preparing other excellent HER electrocatalytic materials.
Time-Average Heat Transfer Coefficient for Steam-Air Condensation during the Dropping of Containment Pressure
Authors: Li Shaodan , Hui Kai , Ke Zhiwu , Li Yong
Published: November 2022

The passive containment cooling system (PCCS) has been applied in the new generation nuclear power plant. Previous studies mainly focused on steady-state heat transfer, but the actual heat transfer of PCCS is the transient process. Thus, investigating the transient heat transfer during the containment pressure dropping is necessary. The present study proposes a time-average condensation heat transfer coefficient (time-average condensation HTC) to characterize the intensity of transient condensation heat transfer. The time-average condensation HTC is defined as the heat absorbed per unit heat transfer area and per unit wall subcooling in a unit time. Experiments were performed to research the effect of initial gas-mixture pressure and air mass fraction on transient HTC. The result showed that the more significant gas-mixture pressure and lower air mass fraction could promote the transient-state heat transfer, especially the low air mass fraction. Based on the experimental result, a detailed empirical correlation for the time-average heat transfer coefficient is developed with an error of ±20%. Another simplified empirical correlation that only includes air mass fraction is also proposed to predict the transient heat transfer roughly. Besides, research on self-sustaining stability is also conducted to evaluate the stable operation characteristic of PCCS. The system can respond quickly and then run to a new steady state after interference during the long-term operation of PCCS. The phenomenon above implies that PCCS has good self-sustaining stability.
Occurrence and Migration Mechanisms of Methane in Marine Shale Reservoirs
Authors: Hu Zhiming , Mu Ying , Guo Qiulei , Niu Wente , Duan Xianggang , Chang Jin , Wu Zhenkai
Published: November 2022

The occurrence mechanism of methane is very important as evaluating the gas-bearing properties of marine shale reservoirs, and the evaluation of the development effect of shale gas wells need to focus on the migration mechanism of methane. In this study, LTNA technology and NMR technology were used to analyze the pores and methane of shale. The results show that inorganic pores have better connectivity, larger pore size, and micro–nano cracks between pores compared to organic pores. Most of the pores in shale are micropores and mesopores, which provide most of the specific surface area, but the contribution of macropores to pore volume cannot be ignored. Adsorbed gas volume depends on the pore surface area and gas pressure, while free gas volume depends on pore volume and gas pressure. The pore structure of micropores and mesopores is complex, and the specific surface area is large. The dispersion force between pore surface molecules and methane molecules is firm, which makes the pore wall an ideal enrichment space for adsorbed gas. Macropores have larger pore volumes and can store more free gas. In the process of gas well development, free gas is first discharged from pores under the action of the pressure gradient. As the pore pressure is lower than the critical desorption pressure, adsorbed gas begins to desorb in large quantities. It should be noted that the desorption process of adsorbed gas is slow and persistent, which makes it impossible for gas wells to achieve higher recovery in a shorter production cycle. Therefore, improving the recovery rate of adsorbed gas is the key to future research on shale gas development effects. This study is helpful in clarifying the occurrence and migration mechanism of methane in marine shale reservoirs and guiding the development of gas wells.
Additional Compound Damping Control to Suppress Low-Frequency Oscillations in a Photovoltaic Plant with a Hybrid Energy Storage System
Authors: Dai Kanglin , Xiong Wei , Yuan Xufeng , Zheng Huajun , Feng Qihui , Xu Yutao , Cai Yongxiang , Guo Dan
Published: November 2022

The use of the conventional dual closed-loop control strategy by photovoltaic (PV) plants with grid-connected inverters may weaken the damping of a power system, which may aggravate low-frequency oscillations (LFOs). This influence will become more severe as the penetration of PV plants increases. Therefore, it is necessary to incorporate damping controls into PV plants to suppress LFOs. This paper proposed an additional compound damping control (ACDC) system that combines additional damping control (ADC) for the inverter with ADC-based dynamic power compensation control (DPCC), allowing hybrid energy storage systems (HESSs) to suppress LFOs. First, the feasibility of suppressing low-frequency oscillations in PV plants is demonstrated by the torque method and a small signal model. Then, an additional damping controller is added to the active power control link of the PV inverter to enhance the damping abilities of the system. However, given that the damping performance of PV plants with only ADC is limited by the compensated power, PV plants require devices that can rapidly compensate for the damping power. Therefore, we added the HESS to the DC bus and proposed DPCC. Finally, a three-machine nine-node system for a PV plant was modeled and simulated in the PSCAD platform. The simulation results showed that the proposed control strategy could provide effective damping for interarea oscillation.
The Effect of Nodalization Schemes on the Stability Characteristics of a Three Heated Channels under Supercritical Flow Condition
Authors: Singh Munendra Pal , Berrouk Abdallah Sofiane , Saeed Muhammad
Published: November 2022

The present analysis is aimed at conducting node sensitivity analysis on the thermal–hydraulic performance of supercritical fluid in a three parallel channel configuration system. The heated channel was divided into different nodes and is examined under wide-ranging operating conditions. Firstly, the heated channel was divided into two nodes, like the two-phase flow system. In the second case, based on the correlation between the fluid properties, the heated channel was divided into three regions: heavy, mixture, and supercritical fluids. Finally, the channel was divided into N-nodes. Post the nodalization analysis, a non-linear analysis of three parallel channels was carried out under varied heat flux conditions. The analytical approximation functions were developed to capture the fluid flow dynamics. These functions were used to capture each node’s density, enthalpy, and velocity profiles under a wide range of operating conditions. The different flow instability (density wave oscillations and static) characteristics were observed at low pseudo- and relatively high subcooling numbers. In the density wave oscillations regime, out-of-phase oscillations and limit cycles are observed. A co-dimension parametric analysis with numerical simulations was carried out to confirm the obtained non-linear characteristics. Such analysis for parallel channel systems under supercritical working fluid flow conditions is missing in the literature which is limited to only linear stability analysis. This analysis can help to improve heat and mass transfer for designing efficient heated channel systems.
Evaluation of the Immobilization of Fly Ash from the Incineration of Municipal Waste in Cement Mortar Incorporating Nanomaterials—A Case Study
Authors: Czop Monika , Łaźniewska-Piekarczyk Beata , Kajda-Szcześniak Małgorzata
Published: November 2022

Fly ash generated in the process of combustion of municipal waste is classified as hazardous waste. Its management today has become a significant problem. One of the methods of safe management of such ash may be using it for the production of concrete as a partial replacement for cement. Using immobilization, the number of hazardous compounds could be limited so that the obtained new material would be safe for the natural environment. Recovery of byproducts—in this case, fly ash—complies with the business models applied in the production cycle in the circular economy model. Such a solution may result in saving energy, limiting CO2 emissions, reducing the use of natural resources, and management of dangerous waste. It should be added that concretes with the addition of hazardous waste would be used for industrial purposes according to the binding legal regulations. This article presents the influence of the addition of fly ash on the selected mechanical properties of concrete. Fly ash from the incineration of municipal waste was used as a partial replacement of CEM I concrete at amounts of 4%, 8%, and 18% of its mass. The compressive strength and flexural strength of such concretes were tested after 28 days of concrete curing. This article also presents the tests of the leachability of contaminants from fly ash and concretes produced with Portland cement CEM I. The test results confirm that immobilization is an effective process that limits the amount of contamination in the water extract. Zinc, lead, and chrome were almost completely immobilized by the C-S-H (calcium silicate hydrate) concrete phase, with their immobilization degree exceeding 99%. Chloride content also underwent immobilization at a similar level of 99%. The sulfates were immobilized at the level of 96%. The subject matter discussed in this article is essential because, to protect the natural environment and, thus, reduce the use of natural resources, it is increasingly necessary to reuse raw materials—not natural, but recycled from the industry. Waste often contains hazardous compounds. A proposal for their safe disposal is their immobilization in a cement matrix. An important aspect is reducing leachability from concrete as much as possible, e.g., using nanomaterials. The effectiveness of reducing the leachability of hazardous compounds with the proposed method was checked in this study.
Water Vapor Blending Ratio Effects on Combustion Thermal Performance and Emission of Hydrogen Homogeneous Charge Compression Ignition
Authors: Yuan Wenhua , Huang Xueliang , Fu Jun , Ma Yi , Li Guangming , Huang Qike
Published: November 2022

A numerical model of the micro-free-piston engine was developed and its correctness was verified by the comparison between the simulation and referential experiment results under the same work conditions. Based on this numerical model, the effects of the water vapor blending ratio (α) on combustion thermal performance and emission characteristics of hydrogen (H2) homogeneous charge compressing ignition (HCCI) were investigated numerically. The water vapor impact on combustion temperature was analyzed as well. The simulation results reveal that when the initial equivalent ratio is 0.5, blending H2 with water vapor can delay the ignition time and prolong the whole process. At the same time, the addition of water vapor to H2 decreases the peak combustion temperature and pressure, which will alleviate the detonation phenomenon of the combustion chamber. Moreover, the power output capacity and NOx emissions decrease with the increase in α. When α increases to 0.8, the mixture gas cannot be compressed to ignite. Finally, the dilution effect, thermal effect, and chemical effect of water vapor all have the potential to lower the combustion temperature and the dilution effect plays the leading role.
The Instability Characteristics and Displacement Law of Coal Wall Containing Joint Fissures in the Fully Mechanized Working Face with Great Mining Height
Authors: Guo Weibin , Li Yuhui , Wang Gang
Published: November 2022

Coal wall rib-spalling is regarded as a key technical problem influencing safe and efficient mining of fully mechanized working face with great mining height (FGH) while the coal wall stability is influenced by the strength of the coal body, of which the internal joint fissures have a crucial impact on the strength of the coal body. This research attempted to explore how the coal wall stability of FGH is influenced by the occurrence of joint fissures. This paper uses physical and numerical simulations to systematically analyze the instability characteristics and displacement law of FGH. Research results show that the form and scope of the instability of coal wall rib-spalling depend on the state of the coal seam joint fissures development area, and the development state of coal seam joint fissures is related to the combination of the coal seam joints; under the condition of hard coal, the coal wall stability is better at the inclination angle of 90°, and less stable at 45° and 135°; under the condition of medium-hard coal and joint surface inclination angle of 45° and 135°, the smaller the spacing of joint surface, the larger the area of the working face rib-spalling, and the less stable the coal wall.
A Review of Peer-to-Peer Energy Trading with Standard Terminology Proposal and a Techno-Economic Characterisation Matrix
Authors: Domènech Monfort Meritxell , De Jesús César , Wanapinit Natapon , Hartmann Niklas
Published: November 2022

Nowadays decarbonisation of the energy system is one of the main concerns for most governments. Renewable energy technologies, such as rooftop photovoltaic systems and home battery storage systems, are changing the energy system to be more decentralised. As a consequence, new ways of energy business models are emerging, e.g., peer-to-peer energy trading. This new concept provides an online marketplace where direct energy exchange can occur between its participants. The purpose of this study is to conduct a content analysis of the existing literature, ongoing research projects, and companies related to peer-to-peer energy trading. From this review, a summary of the most important aspects and journal papers is assessed, discussed, and classified. It was found that the different energy market types were named in various ways and a proposal for standard language for the several peer-to-peer market types and the different actors involved is suggested. Additionally, by grouping the most important attributes from peer-to-peer energy trading projects, an assessment of the entry barrier and scalability potential is performed by using a characterisation matrix.
Influencing Factors of a Cooling System Based on Low-Temperature Mine Water as a Direct Cooling Source
Authors: Jiang Heguo , Cui Shuwen , Mu Xingwang , Tang Lin , Wang Yuheng , Jian Congguang , Chen Chen
Published: November 2022

With the depletion of shallow metal mineral resources, deep mining has become more common. In the process of deep mining, heat hazards in mines seriously threaten the health of personnel and the safety of mining operations. According to the flow and low-temperature characteristics of abundant water in Maoping Lead Zinc Mine, this paper proposes the direct use of the low-temperature water inflow of the mine as the cold source by which to conduct the heat exchange with a single spiral-tube heat exchanger for mine cooling. An experimental platform was built for the cooling system to allow us to explore the mechanism of the influence of the inlet air volume and air temperature and the inlet water temperature and flow on the cooling effect of the single spiral-tube heat exchanger. It was found that with the increase in the inlet air volume and inlet water temperature, the cooling efficiency of the heat exchanger decreased, while with the increase in the inlet air temperature, the cooling efficiency of the heat exchanger increased. Within the experimental range, 127.2 m3/h was found to be the optimum inlet air volume, and 33.0 °C was the most appropriate inlet air temperature; the water temperature of Maoping Coal Mine is about 20 °C throughout the year, and the industrial test site can reduce the wind temperature of 31.5 °C to 23.9 °C. The inlet water flow is positively related to the cooling effect. With the increase in the water flow, the outlet temperature of the air flow at each working point was continuously reduced, and the cooling effect of the heat exchanger was improved. The moisture content of the inlet air flow can be reduced by increasing the low-temperature inlet water flow. Through experiments, the feasibility of the cooling system that directly uses the mine’s low-temperature water as the cold source was verified. A multiple linear regression analysis equation for the cooling system model is proposed, which provides a reference for formulating effective measures to prevent and control heat hazards in mines.
Feasibility of Photovoltaic Module Single-Diode Model Fitting to the Current–Voltage Curves Measured in the Vicinity of the Maximum Power Point for Online Condition Monitoring Purposes
Authors: Kalliojärvi Heidi , Lappalainen Kari , Valkealahti Seppo
Published: November 2022

Photovoltaic system condition monitoring can be performed via single-diode model fitting to measured current–voltage curves. Model parameters can reveal cell aging and degradation. Conventional parameter identification methods require the measurement of entire current–voltage curves, causing interruptions in energy production. Instead, partial curves measured near the maximum power point offer a promising option for online condition monitoring. Unfortunately, measurement data reduction affects fitting and diagnosis accuracy. Thus, the optimal selection of maximum power point neighbourhoods used for fitting requires a systematic analysis of the effect of data selection on the fitted parameters. To date, only one published article has addressed this issue with a small number of measured curves using symmetrically chosen neighbourhoods with respect to the maximum power. Moreover, no study has determined single-diode fit quality to partial curves constructed via other principles, e.g., as a percentage of the maximum power point voltage. Such investigation is justified since the voltage is typically the inverter reference quantity. Our work takes the study of this topic to a whole new scientific level by systematically examining how limiting the current–voltage curve measuring range to maximum power point proximity based on both power and voltage affects single-diode model parameters. An extensive dataset with 2400 measured curves was analysed, and statistically credible results were obtained for the first time. We fitted the single-diode model directly to experimental curves without measuring outdoor conditions or using approximations. Our results provide clear guidance on how the choices of partial curves affect the fitting accuracy. A significant finding is that the correct selection of maximum power point neighbourhoods provides promising real-case online aging detection opportunities.
Effect of Hydrogen Enhancement on Natural Flame Luminosity of Tri-Fuel Combustion in an Optical Engine
Authors: Cheng Qiang , Ahmad Zeeshan , Kaario Ossi , Vuorinen Ville , Larmi Martti
Published: November 2022

A novel combustion mode, namely tri-fuel (TF) combustion using a diesel pilot to ignite the premixed methane–hydrogen–air (CH4–H2–air) mixtures, was experimentally investigated under various H2 fractions (0%, 10%, 20%, 40%, 60%) and ultra-lean conditions (equivalence ratio of φ= 0.5). The overarching objective is to evaluate the effect of H2 fraction on flame characteristics and engine performance. To visualize the effect of H2 fraction on the combustion process and flame characteristics, a high-speed color camera (Photron SA-Z) was employed for natural flame luminosity (NFL) imaging to visualize the instantaneous TF combustion process. The engine performance, flame characteristics, and flame stability are characterized based on cylinder pressure and color natural flame images. Both pressure-based and optical imaging-based analyses indicate that adding H2 into the CH4–air mixture can dramatically improve engine performance, such as combustion efficiency, flame speed, and flame stability. The visualization results of NFL show that the addition of H2 promotes the high-temperature reaction, which exhibits a brighter bluish flame during the start of combustion and main combustion, however, a brighter orangish flame during the end of combustion. Since the combustion is ultra-lean, increasing the H2 concentration in the CH4–air mixture dramatically improves the flame propagation, which might reduce the CH4 slip. However, higher H2 concentration in the CH4–air mixture might lead to a high-temperature reaction that sequentially promotes soot emissions, which emit a bright yellowish flame.
Real-Time Power Quality Enhancement in a Hybrid Micro-Grid Using Nonlinear Autoregressive Neural Network
Authors: Satapathy Anshuman , Nayak Niranjan , Parida Tanmoy
Published: November 2022

The extensive use of renewable energy sources (RESs) in energy sectors plays a vital role in meeting the present energy demand. The widespread utilization of allocated resources leads to multiple usages of converters for synchronization with the power grid, introducing poor power quality. The integration of distributed energy resources produces uncertainties which are reflected in the distribution system. The major power quality problems such as voltage sag/swell, voltage unbalancing, poor power factor, harmonics distortion (THD), and power transients appear during the transition of micro-grids (MGs). In this research, a single micro-grid is designed with PVs, wind generators, and fuel cells as distributed energy resources (DERs). A nonlinear auto regressive exogenous input neural network (NARX-NN) controller has been investigated in this micro-grid in order to maintain the above power quality issues within the specific standard range (IEEE/IEC standards). The performance of the NARX-NN controller is compared with PID and fuzzy-PID controllers. The single micro-grid is extended to design a three-phase large-scale realistic micro-grid structure to test the feasibility of the proposed controller. The realistic micro-grid is verified through addition of line-impedance, communication delay, demand response, and off-nominal situations. The proposed controller is also validated by simulating different test scenarios using MATLAB/Simulink and TMS320-based processor-in-loop (PIL) for real-time implementation.
Numerical Simulation Research on the Vibration of Helical Tube Arrays under Transverse Flow
Authors: Ding Zhenyu , Bai Xilan , Zhai Yanfei , Yang Jiahuan , Liu Dawei , Yang Yin , Tang Di
Published: November 2022

Helical tube steam generators are often used in nuclear power plants because of their compact structure and high heat transfer efficiency. The impact of the internal fluid causes the vibration of the tube bundle, which leads to the failure of the integrity of the safety structure. Aiming at flow-induced vibration (FIV) of helical tube arrays, a finite element model of the helical tube was established to consider the constraint of the support structure. The computational fluid dynamics (CFD)/computational structural dynamics (CSD) coupling calculation method based on the superposition of three modes was used to study the FIV characteristics of helical tube arrays at different flow velocities. The influence of adjacent helical tubes’ vibration on the vibration of the target tube was also investigated. The results show that when FIV occurs in the helical tube, with the increase of inlet velocity, the axial amplitude will be greater than the radial at the same velocity. When some tubes vibrate, the vibration of the target tube will be enhanced; while adjacent tubes vibrate, it will weaken the impact of the fluid on the target tube and obviously weaken the vibration of the target tube.
Simulation and Optimization of Lignocellulosic Biomass Wet- and Dry-Torrefaction Process for Energy, Fuels and Materials Production: A Review
Authors: Nazos Antonios , Politi Dorothea , Giakoumakis Georgios , Sidiras Dimitrios
Published: November 2022

This review deals with the simulation and optimization of the dry- and wet-torrefaction processes of lignocellulosic biomass. The torrefaction pretreatment regards the production of enhanced biofuels and other materials. Dry torrefaction is a mild pyrolytic treatment method under an oxidative or non-oxidative atmosphere and can improve lignocellulosic biomass solid residue heating properties by reducing its oxygen content. Wet torrefaction usually uses pure water in an autoclave and is also known as hydrothermal carbonization, hydrothermal torrefaction, hot water extraction, autohydrolysis, hydrothermolysis, hot compressed water treatment, water hydrolysis, aqueous fractionation, aqueous liquefaction or solvolysis/aquasolv, or pressure cooking. In the case of treatment with acid aquatic solutions, wet torrefaction is called acid-catalyzed wet torrefaction. Wet torrefaction produces fermentable monosaccharides and oligosaccharides as well as solid residue with enhanced higher heating value. The simulation and optimization of dry- and wet-torrefaction processes are usually achieved using kinetic/thermodynamic/thermochemical models, severity factors, response surface methodology models, artificial neural networks, multilayer perceptron neural networks, multivariate adaptive regression splines, mixed integer linear programming, Taguchi experimental design, particle swarm optimization, a model-free isoconversional approach, dynamic simulation modeling, and commercial simulation software. Simulation of the torrefaction process facilitates the optimization of the pretreatment conditions.
Dairy Wastewater as a Potential Feedstock for Valuable Production with Concurrent Wastewater Treatment through Microbial Electrochemical Technologies
Authors: Ganta Anusha , Bashir Yasser , Das Sovik
Published: November 2022

A milk-processing plant was drafted as a distinctive staple industry amid the diverse field of industries. Dairy products such as yogurt, cheese, milk powder, etc., consume a huge amount of water not only for product processing, but also for sanitary purposes and for washing dairy-based industrial gear. Henceforth, the wastewater released after the above-mentioned operations comprises a greater concentration of nutrients, chemical oxygen demand, biochemical oxygen demand, total suspended solids, and organic and inorganic contents that can pose severe ecological issues if not managed effectively. The well-known processes such as coagulation–flocculation, membrane technologies, electrocoagulation, and other biological processes such as use of a sequencing batch reactor, upflow sludge anaerobic blanket reactor, etc., that are exploited for the treatment of dairy effluent are extremely energy-exhaustive and acquire huge costs in terms of fabrication and maintenance. In addition, these processes are not competent in totally removing various contaminants that exist in dairy effluent. Accordingly, to decrease the energy need, microbial electrochemical technologies (METs) can be effectively employed, thereby also compensating the purification charges by converting the chemical energy present in impurities into bioelectricity and value-added products. Based on this, the current review article illuminates the application of diverse METs as a suitable substitute for traditional technology for treating dairy wastewater. Additionally, several hindrances on the way to real-world application and techno-economic assessment of revolutionary METs are also deliberated.
Pythagorean Fuzzy Storage Capacity with Controllable Carbon Emission Incorporating Green Technology Investment on a Two-Depository System
Authors: Bhavani Gudivada Durga , Meidute-Kavaliauskiene Ieva , Mahapatra Ghanshaym S. , Činčikaitė Renata
Published: November 2022

Global warming is mainly caused by carbon emissions. Currently, fewer countries are concentrating on reducing carbon emissions. The primary strategy utilized by numerous countries to achieve carbon emissions reduction is the carbon tax policy. With this in mind, a sustainable two-warehouse inventory model was taken carbon tax into account for a controllable carbon emissions rate by investing in green technology initiatives under uncertain emission and cost parameters. The globe is currently experiencing an eco-friendly period. Many individuals are interested in purchasing natural or herbal items since they are made from natural sources and do not affect the environment. The demand for products made with herbal or natural ingredients is considered eco-friendly demand. This study examines a two-warehouse inventory model of deteriorating commodities with price and marketing-dependent eco-friendly demand. The inventory system is presented to handle the inventory in the depository with last-in-first-out and first-in-first-out strategies. After comparing both the policies under deterioration rate and holding cost, this study recommended a suitable dispatch policy. Interval-valued numbers and fuzzy numbers are the mathematical techniques that deal with uncertainties, so this model’s emission and cost parameters are taken as interval-valued numbers, and the storage capacity of the owned warehouse is a Pythagorean fuzzy number. The optimal solution for the two-warehouse inventory system is evaluated by taking the parametric form of interval-valued cost parameters and the new concept of the ranking function of triangular Pythagorean fuzzy numbers. Numerical results prove that emissions are reduced by 87% under green technology investment in both policies. As a consequence, in the FIFO policy, the total cost of the two-warehouse inventory system decreases by 34.45% and cycle length increases by 5.72%, and in the LIFO policy, the total cost of the two-warehouse inventory system decreases by 34.42% and cycle length increases by 11.19%. Sensitivity analysis of the key parameters has been performed to study the effect of various parameters on the optimal solution.