bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Port PWM DC-DC Power Converter for Renewable Energy Applications
Authors: Almutairi Abdulaziz , Sayed Khairy , Albagami Naif , Abo-Khalil Ahmed G. , Saleeb Hedra
Published: June 2021

In this paper, a new multi-port DC-DC power converter used to deal with the intermittent nature and slow response in renewable energy applications is proposed. The proposed converter integrates a DC-DC converter and a DC-AC inverter, and the proposed circuit integrates various renewable energy sources in addition to the energy storage unit. By combining renewable energy sources with a statistical trend to offset each other, the impact of the intermittency can be considerably minimized. This combination increases the overall system reliability and usability. Moreover, integrating such systems with energy storage systems can overcome the slow response issue of renewable sources. It can provide the additional energy required by the load or absorb the extra energy provided by the power sources, which greatly improves the dynamics of the overall system. The proposed converter can reduce the system cost and size and improve the efficiency and reliability. The operation principle is studied in detail, and the design considerations are provided. The proposed architecture and its control strategy were analyzed and studied using the Simulink/MATLAB environment. Finally, the feasibility of the proper operation of the studied converter was experimentally verified based on the results of experimental studies conducted on a 300 W prototype implemented in a laboratory.
Modular Marx Generator Based on SiC-MOSFET Generating Adjustable Rectangular Pulses
Authors: Achour Yahia , Starzyński Jacek , Rąbkowski Jacek
Published: June 2021

The paper introduces a new design of Marx generator based on modular stages using Silicon Carbide MOSFETs (SiC-MOSFET) aimed to be used in biomedical applications. In this process, living cells are treated with intense nanosecond Pulsed Electrical Field (nsPEF). The electric field dose should be controlled by adjusting the pulse parameters such as amplitude, repetition rate and pulse-width. For this purpose, the structure of the proposed generator enables negative pulses with a quasi-rectangular shape, controllable amplitude, pulse-width and repetition-rate. A complete simulation study was conducted in ANSYS-Simplorer to verify the overall performance. A compact, modular prototype of Marx generator was designed with 1.7 kV rated SiC-MOSFETs and, finally, a set of experiments confirmed all expected features.
Fast Frequency Support from Hybrid Wind Power Plants Using Supercapacitors
Authors: Long Qian , Celna Aivaras , Das Kaushik , Sørensen Poul
Published: June 2021

The concept of hybrid wind power plants (HWPPs) that consist of wind, solar and batteries has received a lot of attention, since HWPPs provide a number of advantages thanks to the complementary nature of wind and solar energy and the flexibility of batteries. Nevertheless, converter-based technologies, as interfaces of HWPPs to the utility grid, contribute to the reduction of total system inertia, making the system more volatile and creating additional threats to frequency stability. To address these operational challenges, the capability of supercapacitors (SCs) to provide fast frequency reserve (FFR) is explored in this paper to enhance the frequency response of the HWPP. Two topologies for integrating SCs into the HWPP are proposed: (1) connecting SC to the DC link of wind turbine (WT) via a DC-DC converter interface, (2) directly connecting SC to the DC link of WT without converter interface. Frequency controllers at the asset level are proposed for these two topologies accordingly. The idea of the proposed frequency controller is to provide frequency response by varying SC voltage in proportion to frequency deviation, namely droop-based FFR. A practical SC sizing method for FFR provision is also discussed. The simulation results have shown, that in the case of frequency event, the proposed frequency controllers for SCs in both topologies positively contribute to the frequency of the system by reducing the rate of change of frequency by at least 5% and improving frequency nadir by at least 10%, compared to the case where the SC has no contribution to FFR. However, the capacitor size requirement for directly connected SC is more demanding in order to achieve the same level of improvement. The performance of frequency support has been highly related to total system inertia and control parameters. Therefore, any change to the severity of frequency events or control parameters calls for the reevaluation of the capacitance.
Comprehensive Assessment of Smart Grids: Is There a Universal Approach?
Authors: Lyulyov Oleksii , Vakulenko Ihor , Pimonenko Tetyana , Kwilinski Aleksy , Dzwigol Henryk , Dzwigol-Barosz Mariola
Published: June 2021

A comprehensive assessment of smart grids is critical for their development. Existing scientific research testifies to the urgency and complexity of the problem of implementing smart grids effectively, both in terms of a single project performance and from the standpoint of creating a local, and later global, energy system. The multidimensionality of smart grids makes it challenging to assess the effectiveness of their implementation. Difficulties in evaluation arise because it is challenging to consider technical, technological, economic, and other relevant aspects of smart grids’ development within a single evaluation system. There are currently a significant number of smart grid assessment systems. However, it remains debatable how systematically and comprehensively they measure the efficiency of a smart grid. This, in turn, raises the question of whether there is a universal evaluation system that integrally considers all the crucial components of smart grids and is suitable for evaluating smart grid projects of different content. This article analyzes the most well-known approaches to comprehensive assessment of smart grids according to the completeness of their coverage of smart grids’ most critical components. This paper identifies the essential areas for assessing smart grids according to the most cited and authoritative research and regulatory documents of the European Union. As a result, seven groups of indicators were identified. These groups of indicators are the basis for comparative analysis of the comprehensive assessment approaches of smart grids. The results of the study should help determine the appropriateness of applying a particular evaluation system. In addition, the analysis of existing evaluation systems allows the shaping of a universal approach to evaluating smart grids comprehensively and systematically.
Double Fed Induction Generator Control Design Based on a Fuzzy Logic Controller for an Oscillating Water Column System
Authors: Napole Cristian , Barambones Oscar , Derbeli Mohamed , Cortajarena José Antonio , Calvo Isidro , Alkorta Patxi , Bustamante Pablo Fernandez
Published: June 2021

Oscillating water column (OWC) systems are water power generation plants that transform wave kinetic energy into electrical energy by a surrounded air column in a chamber that changes its pressure through the waves motion. The chamber pressure output spins a Wells turbine that is linked to a doubly fed induction generator (DFIG), flexible devices that adjust the turbine speed to increase the efficiency. However, there are different nonlinearities associated with these systems such as weather conditions, uncertainties, and turbine stalling phenomenon. In this research, a fuzzy logic controller (FLC) combined with an airflow reference generator (ARG) was designed and validated in a simulation environment to display the efficiency enhancement of an OWC system by the regulation of the turbine speed. Results show that the proposed framework not only increased the system output power, but the stalling is also avoided under different pressure profiles.
Bin Weather Data for HVAC Systems Energy Calculations
Authors: Papakostas Konstantinos T. , Kyrou Dimitrios , Kourous Kyrillos , Founda Dimitra , Martinopoulos Georgios
Published: June 2021

The increase in global air temperature is well documented, as during the last several years each decade has been consecutively warmer than the preceding. As climatic conditions affect the energy performance of buildings, the changes in outdoor air temperature and humidity will inevitably lead to significant alterations in energy consumption and costs for the heating, ventilating and air conditioning (HVAC) of buildings. The availability and quality of climatic data play an important role in the accuracy of energy analysis results. In this study, the hourly temperature and relative humidity of outdoor air measurements, for a period of three decades (1983–2012), recorded at the climatic station of the National Observatory of Athens were processed, and an up-to-date set of specific data for the application of bin methods was produced and presented. The data were then used to calculate changes in the energy demands in a typical office building throughout the specified period. Results showed a progressive reduction in the low and increase in the high temperature intervals, leading to an increase in the building’s annual energy requirements for air conditioning of up to 14.5% from the first to the third decade, with decrease in the energy demands for heating and increase in the energy demands for cooling.
Small Unconventional Hydrocarbon Gas Reservoirs as Challenging Energy Sources, Case Study from Northern Croatia
Authors: Malvić Tomislav , Barudžija Uroš , Pašić Borivoje , Ivšinović Josip
Published: June 2021

Small possible hydrocarbon gas reservoirs were analysed in the Bjelovar Subdepression in Northern Croatia. This area includes the Neogene–Quaternary, mostly clastics, sequences, reaching 3000+ metres in the deepest part. The shallow south-eastern part of the Drava Depression contains a subdepression characterised with several, mostly small, discovered hydrocarbon fields, where the majority are located on the northern subdepression margin. The reason is the large distance from the main depressional migration pathways and main, deep, mature source rock depocenters. However, two promising unconventional targets were discovered inside the subdepression and both were proven by drilling. The first are source rocks of Badenian, of kerogen type III in early catagenesis, where partially inefficient expulsion probably kept significant gas volumes trapped in the source rock during primary migration. Such structures are the Western Bjelovar (or Rovišće) and the Eastern Bjelovar (or Velika Ciglena) Synclines. The second promising unconventional reservoir consists of “tight” clastic lithofacies of mostly Lower Pontian located on the north-eastern margin of the subdepression. These are fine-grained sandstones with frequent alternations in siltites, silty and clayey sandstones. They are located on secondary migration pathways, but were never evaluated as regional reservoirs, although numerous drilling tests showed gas “pockets”.
Simulation-Based Analysis of Greenhouse Gas Emissions in Sustainable Supply Chains—Re-Design in an Approach to Supply Chain Strategy
Authors: Tundys Blanka , Wiśniewski Tomasz
Published: June 2021

The aim of the study was to analyze emissions in the supply chain and to identify, based on a literature analysis, which supply chain strategies could contribute to reducing these emissions. A broad spectrum of new supply chain strategy solutions was identified and, based on simulations of selected products, conclusions were drawn and the advantages and disadvantages of theoretical solutions were presented for individual cases. A critical analysis of the literature and simulation methods were used to illustrate the problem presented in this paper, to identify the factors causing greenhouse gas emissions and to draw conclusions in the form of proposals to redesign existing strategies, considering the factors determining the increase in pollution caused by the performed logistics processes. The results of the simulations and the literature analysis indicate that solutions related to the redesign of strategies must consider the specificity of the product and the nature of the chain. Not all proposed strategies are applicable to all chains, and each new strategy must be carefully considered and consider many factors. An important element to reduce the negative environmental impact of chains is a well-thought-out relationship with suppliers, a well-chosen and adapted logistics infrastructure, including means of transport. The presented solutions clearly indicate that the environmental aspect plays an increasingly important role in chain management and influences the applied chain strategies. However, reducing the environmental impact of a chain is not a revolutionary approach and an easy-to-implement strategy change, but a well-thought-out, long-term process that considers the specifics of the products, the possibilities of alternative sourcing and distribution modes, and the need to invest in logistics infrastructure to make it as environmentally neutral as possible.
Microwave Spectroscopy as a Potential Tool for Color Grading Diamonds
Authors: Rabinowitz Yossi , Etinger Ariel , Yahalom Asher , Cohen Haim , Pinhasi Yosef
Published: June 2021

A diamond’s color grading is a dominant property that determines its market value. Its color quality is dependent on the light transmittance through the diamond and is largely influenced by nitrogen contamination, which induces a yellow/brown tint within the diamond, as well as by structural defects in the crystal (in rare cases boron contamination results in a blue tint). Generally, spectroscopic instrumentation (in the infrared or UV–visible spectral range) is used in industry to measure polished and rough diamonds, but the results are not accurate enough for precise determination of color grade. Thus, new methods should be developed to determine the color grade of diamonds at longer wavelengths, such as microwave (MV). No difference exists between rough and polished diamonds regarding stray light when the MW frequency is used. Thus, several waveguides that cover a frequency range of 3.95–26.5 GHz, as well as suitable resonator mirrors, have been developed using transmission/reflection and resonator methods. A good correlation between the S12 parameter and the nitrogen contamination content was found using the transmission/reflection method. It was concluded that electromagnetic property measurements of diamonds in the MW frequency range can be used to determine their nitrogen content and color grading. The MW technique results were in good agreement with those obtained from the infrared spectra of diamonds.
Electrodynamics of Reactive Power in the Space of Inter-Substation Zones of AC Electrified Railway Line
Authors: Kostin Mykola , Nikitenko Anatolii , Mishchenko Tetiana , Shumikhina Lyudmila
Published: June 2021

In railway traction, the definition of “electromagnetic field” is functionally connected to the concept of the reactive power consumed by the electric rolling stock, and characterized by the running and standing electromagnetic waves in the space of the inter-substation zones from the site of the AC traction system. Such a definition is established and theoretically justified by the theory of electromagnetic fields. This article uses the methodology of this theory, in particular, a method for power balance estimation in electromagnetic fields based on Maxwell’s equations, as well as methods for the analysis of running and standing electromagnetic waves based on the theory of reflection, propagation and transmission of plane harmonic waves. The research considers the regularities of standing electromagnetic waves in the space of inter-substation zones of electric traction systems, which occur due to the incomplete reflection of incident waves from the contact wire and metal parts of the roof surface and the frontal part of the body of the electric rolling stock. The flow of electricity to the roof surface and the frontal part of the body of an electric locomotive is considered. The possibility of using existing methods to reduce wave reflections and thereby to effectively compensate for reactive power in the space of inter-substation zones is discussed.
Conventional and Advanced Exergoeconomic Analysis of a Compound Ejector-Heat Pump for Simultaneous Cooling and Heating
Authors: Al-Sayyab Ali Khalid Shaker , Navarro-Esbrí Joaquín , Soto-Francés Victor Manuel , Mota-Babiloni Adrián
Published: June 2021

This work focused on a compound PV/T waste heat driven ejector-heat pump system for simultaneous data centre cooling and waste heat recovery for district heating. The system uses PV/T waste heat as the generator’s heat source, acting with the vapour generated in an evaporative condenser as the ejector drive force. Conventional and advanced exergy and advanced exergoeconomic analyses are used to determine the cause and avoidable degree of the components’ exergy destruction rate and cost rates. Regarding the conventional exergy analysis for the whole system, the compressor represents the largest exergy destruction source of 26%. On the other hand, the generator shows the lowest sources (2%). The advanced exergy analysis indicates that 59.4% of the whole system thermodynamical inefficiencies can be avoided by further design optimisation. The compressor has the highest contribution to the destruction in the avoidable exergy destruction rate (21%), followed by the ejector (18%) and condenser (8%). Moreover, the advanced exergoeconomic results prove that 51% of the system costs are unavoidable. In system components cost comparison, the highest cost comes from the condenser, 30%. In the same context, the ejector has the lowest exergoeconomic factor, and it should be getting more attention to reduce the irreversibility by design improving. On the contrary, the evaporator has the highest exergoeconomic factor (94%).
A Technology of Hydrocarbon Fluid Production Intensification by Productive Stratum Drainage Zone Reaming
Authors: Bazaluk Oleg , Slabyi Orest , Vekeryk Vasyl , Velychkovych Andrii , Ropyak Liubomyr , Lozynskyi Vasyl
Published: June 2021

The paper proposes a new technology for fluid production intensification, in particular hydrocarbons, which is implemented via significant increasing of the local wellbore diameter in the interval, where the productive stratum is present. The proposed technology improves the well productivity by increasing the filtration surface area and opening new channels for filtering fluids into the well. The innovative, technical idea is to drill large diameter circular recesses in planes perpendicular to the well axis. After that, the rock mass located between the circular recesses are destroyed by applying static or dynamic axial loads. The required value of the axial force is provided by the weight of the standard drilling tool. As a result of the study, the analytical relations to specify the admissible radius of circular recesses and admissible thickness of rock mass between two adjacent circular recesses from the condition of safe operation are obtained. The numerical analysis carried out for typical reservoir rocks substantiated the possibility of well diameter local reaming twenty times. A special tool for circular recess drilling is developed and the principle of its operation is described. The advantage of the proposed approaches is the low energy consumption for well diameter reaming. Our technology will have special economic expediency for the intensification of production from hydrodynamically imperfect wells and under the condition of fluid filtration according to the expressed nonlinear law.
Investigation of Thermal Stress Arising in a Graphene Neutral Density Filter for Concentrated Photovoltaic System
Authors: Alzahrani Mussad M. , Roy Anurag , Sundaram Senthilarasu , Mallick Tapas K.
Published: June 2021

As an excellent heat spreader candidate, graphene attracts considerable interest concerning its application in concentrated photovoltaic (CPV) systems. The consequences of employing a graphene-coated neutral density (GCND) filter to mitigate concentrated light impact adequately. Hence, the temperature for a concentrated photovoltaic system is reported in this work. A systematic thermal characterisation study was carried out using three different thickness-based GCND filters. Interestingly, using the GCND filter, the focal spot temperature remained considerably lower than that of the incident temperature for a more extended period. The graphene coating orientation further influenced the temperature gradient behaviour of the focal spot and incident temperature. The thermal and electrical results depended on the GC samples’ thickness and emplacement, leading to dramatic differences in their respective photovoltaic performance. As a base substrate of the GCND filter, the low-iron glass suffered extreme thermal stress under concentrated solar irradiance. This thermal stress phenomenon on the GCND filter was further analysed. This study suggests that using GCND leads to lower temperature maintenance of the CPV focal point, which minimises the PV cell thermal stress. However, the GCND filter also experienced considerable thermal stress during the CPV experiment.
Optimization of Static and Dynamic Charging Infrastructure for Electric Buses
Authors: Csonka Bálint
Published: June 2021

The adoption of electric buses in public transport requires careful planning for the bus fleet and charging infrastructure. A mathematical model of an urban bus service was developed to support the deployment of charging infrastructure. The novelty of the model is that it incorporates infrastructure elements for both static and dynamic charging technologies at the same time. The model supports the electrification of the bus lines without route and schedule adjustments. The volume of charged energy at charging units is considered as a variable in the objective function to determine the location of charging units at minimum cost. The model was verified by a case study based on actual bus service data. It was found that the use of static chargers is more favorable if the cost of a static charging unit is less than the cost of a dynamic charger with a length of 1600 m and the charging power of static chargers is three times greater than the charging power of dynamic chargers. The relationship between charging power and the length of the dynamic charging unit was analyzed. It was noted that the use of charging power higher than 162.5 kW at dynamic charging units is not necessary.
An Investigation into the Energy-Efficient Motion of Autonomous Wheeled Mobile Robots
Authors: Mohammadpour Mohammad , Zeghmi Lotfi , Kelouwani Sousso , Gaudreau Marc-André , Amamou Ali , Graba Massinissa
Published: June 2021

In recent years, the use of electric Autonomous Wheeled Mobile Robots (AWMRs) has dramatically increased in transport of the production chain. Generally, AWMRs must operate for several hours on a single battery charge. Since the energy density of the battery is limited, energy efficiency becomes a key element in improving material transportation performance during the manufacturing process. However, energy consumption is influenced by the navigation stages, because the type of motion necessary for the AWMR to perform during a mission is totally defined by these stages. Therefore, this paper analyzes methods of energy efficiency that have been studied recently for AWMR navigation stages. The selected publications are classified into planning and motion control categories in order to identify research gaps. Unlike other similar studies, this work focuses on these methods with respect to their implications for the energy consumption of AWMRs. In addition, by using an industrial Self-Guided Vehicle (SGV), we illustrate the direct influence of the motion planning stage on global energy consumption by means of several simulations and experiments. The results indicate that the reaction of the SGV in response to unforeseen obstacles can affect the amount of energy consumed. Hence, energy constraints must be considered when developing the motion planning of AWMRs.
Investigating Carbon Emissions from Electricity Generation and GDP Nexus Using Maximum Entropy Bootstrap: Evidence from Oil-Producing Countries in the Middle East
Authors: Zanjani Zeinab , Macedo Pedro , Soares Isabel
Published: June 2021

The maximum entropy bootstrap for time series is applied in this study to investigate the nexus between carbon emissions from electricity generation and the gross domestic product, using a bivariate framework for eight Middle Eastern countries between 1995 and 2017. The sample under study includes oil-producing countries such as Bahrain, Iran, Iraq, Kuwait, Oman, Qatar, Saudi Arabia, and United Arab Emirates. As the electricity generation in these economies relies mainly on oil and gas, finding out the existence and direction of the relationship between the two considered variables has remarkable implications for policymakers and governments in these countries to achieve both higher economic growth and environmental protection. As expected, this nexus is validated for all countries in the sample but not in all models, time periods, and lags. Therefore, policymakers can set appropriate electricity conservation policies based on these varied empirical findings to boost economic growth with minimum environmental degradation.
Investigating the Sustainable Impact of Seaport Infrastructure Provision on Maritime Component of Supply Chain
Authors: Bernacki Dariusz , Lis Christian
Published: June 2021

The aim of the research is to identify and quantify the direct economic effects resulting from the improved seaport nautical access and capacity expansion. This case study considers a regional port located in the Baltic sea and relates to port users, i.e., shipping operators and shippers. The effects were identified for maritime transport by comparing transport performance in two scenarios: with-the-investment and without-the-investment. Incremental calculus addresses freights (containers, dry bulk, and cereals) traded to and from the given port, changes in size of vessels, and the shipping route alternatives vis-a-vis adjacent ports in the range. Sustainable impact concerns generalized maritime transport cost, i.e., shipping operating costs and port-to-port transit time, as well as energy consumption and external costs of maritime shipping. To capture effects, daily and unit dry bulk, as well as container shipping cost, values of time, and marginal external costs were revealed in freight sea transport. As investigated, shipping operators and shippers will benefit from the reduction in ships’ operating (including ships’ fuel cost savings) and time cost, while the community will enjoy the reduction in externalities. However, the main economic effect is the reduction in shipping operating cost resulting from the increased vessel size (economies of scale).
Analysis of New Flexibility Market Models in Europe
Authors: Valarezo Orlando , Gómez Tomás , Chaves-Avila José Pablo , Lind Leandro , Correa Mauricio , Ulrich Ziegler David , Escobar Rodrigo
Published: June 2021

To identify the trends in new flexibility markets, a set of market and aggregator platforms were selected and compared. The analyzed initiatives are relevant to consider alternative designs for European electricity markets. This review proposes a common methodology for analyzing these market models by comparing their description, market structure, market timing, and implementation. Furthermore, a range of policy implications and future research directions towards implementing these markets are presented. The results provide compelling evidence that the new market models represent a promising business with technical and economic justification, as they incentivize the uptake of flexibility from distributed resources by providing services to Distribution System Operators (DSOs) in coordination with Transmission System Operators (TSOs). Moreover, the interactions between these new market platforms and existing markets are of particular interest, and the contributions from aggregator platforms are also relevant to enhance the political vision of empowering the customers through their active participation in markets.
Population Balance Application in TiO2 Particle Deagglomeration Process Modeling
Authors: Krzosa Radosław , Makowski Łukasz , Orciuch Wojciech , Adamek Radosław
Published: June 2021

The deagglomeration of titanium-dioxide powder in water suspension performed in a stirring tank was investigated. Owing to the widespread applications of the deagglomeration process and titanium dioxide powder, new, more efficient devices and methods of predicting the process result are highly needed. A brief literature review of the application process, the device used, and process mechanism is presented herein. In the experiments, deagglomeration of the titanium dioxide suspension was performed. The change in particle size distribution in time was investigated for different impeller geometries and rotational speeds. The modification of impeller geometry allowed the improvement of the process of solid particle breakage. In the modelling part, numerical simulations of the chosen impeller geometries were performed using computational-fluid-dynamics (CFD) methods whereby the flow field, hydrodynamic stresses, and other useful parameters were calculated. Finally, based on the simulation results, the population-balance with a mechanistic model of suspension flow was developed. Model predictions of the change in particle size showed good agreement with the experimental data. Using the presented method in the process design allowed the prediction of the product size and the comparison of the efficiency of different impeller geometries.
Congestion Management by Allocating Network Use Cost for the Small-Scale DER Aggregator Market in South Korea
Authors: Noorfatima Nadya , Yang Yejin , Jung Jaesung , Kim Jun-Sung
Published: June 2021

The increasing penetration level of distributed energy resources (DERs) increases the risk of congestion in the distribution network. To mitigate this, the concept of the small-scale DER aggregator was introduced as a change from uncoordinated to coordinated DERs. However, without appropriate network use cost allocation, the unwanted DER curtailment will be enforced by the network operator. Therefore, this paper proposes a new approach for congestion management by allocating the different network usage costs depending on how much congestion is caused by the DERs in the distribution network. For this, a modified Kirschen’s tracing method is proposed and applied to the small-scale DER aggregator market. To verify the effectiveness of the proposed method, a simulation of the small-scale DER aggregator market in South Korea was performed under the IEEE 69-bus distribution network. The model was able to allocate the different network usage costs at different buses and, thus, encouraged the DERs to reduce their generation by charging the energy storage system (ESS) to mitigate congestion. An economic benefit analysis was also performed from the point of view of the aggregator concerning whether they should have an ESS or not.
Using Value Stream Mapping to Eliminate Waste: A Case Study of a Steel Pipe Manufacturer
Authors: Salwin Mariusz , Jacyna-Gołda Ilona , Bańka Michał , Varanchuk Dari , Gavina Anna
Published: June 2021

Value Stream Mapping (VSM) is a popular and easy tool for visualizing production processes in enterprise. It allows one to eliminate or reduce waste, i.e., activities that do not create added value for the customer. The versatility of this tool allows it to be used in industry. There are theoretical, methodological, and practical aspects encountered by practitioners in developing Value Stream Mapping (VSM) for a specific manufacturing industry, but they are not fully resolved and require clarification. This paper presents a case study that describes the use of Value Stream Mapping (VSM) in the production of steel pipes. Relevant data from this process were collected and analyzed at the start of the project. An initial process was mapped, associated waste was identified, and then future processes were mapped. The financial results were estimated. Consequently, the process was improved, and savings were achieved. The article should constitute the basis for further development of an improvement project for a selected company aimed at improving the areas identified in a given article.
Performance Optimization of Solar-Assisted Heat Pump System for Water Heating Applications
Authors: Meena Chandan Swaroop , Raj Binju P , Saini Lohit , Agarwal Nehul , Ghosh Aritra
Published: June 2021

The use of solar energy in water heating applications, such as in solar-assisted heat pump systems, has great benefits, such as reductions in heat transfer losses, control over incident solar heat, and generation of environmentally benign water heat. In the present study, we performed parametric optimization based on an experimental model of a solar-assisted heat pump system for water heating (SAHPSWH) in the context of colder climatic regions receiving minimal solar radiation. Various parameters were investigated, such as the different glazing arrangements, the distances between fluid-circulating tubes, and the absorber sheet arrangement. The results showed that double glazing was more efficient than single glazing, with average COP values of 3.37 and 2.69, respectively, and with similar heat gain rates. When the evaporator tube was soldered below the absorber plate, the COP was 1.19 times greater than when the tube was soldered above the absorber plate. We also analyzed whether the collector efficiency factor F′ has an inverse relationship with the tube distance and a direct relationship with the absorber plate thickness. Through this experimental study, we verified that the SAHPSWH is reliable if designed judiciously. This promising energy-saving system is particularly suitable for areas abundant in solar radiation, such as in India, where the needs for space conditioning and water heating are constant.
Removing the Bottleneck on Wind Power Potential to Create Liquid Fuels from Locally Available Biomass
Authors: Castro Garcia Abraham , Cheng Shuo , Cross Jeffrey S.
Published: June 2021

In order to reduce global greenhouse gas emissions, renewable energy technologies such as wind power and solar photovoltaic power systems have recently become more widespread. However, Japan as a nation faces high reliance on imported fossil fuels for electricity generation despite having great potential for further renewable energy development. The focus of this study examines untapped geographical locations in Japan’s northern most prefecture, Hokkaido, that possess large wind power potential. The possibility of exploiting this potential for the purpose of producing green hydrogen is explored. In particular, its integration with a year-round conversion of Kraft lignin into bio-oil from nearby paper pulp mills through a near critical water depolymerization process is examined. The proposed bio-oil and aromatic chemical production, as well as the process’ economics are calculated based upon the total available Kraft lignin in Hokkaido, including the magnitude of wind power capacity that would be required for producing the necessary hydrogen for such a large-scale process. Green hydrogen integration with other processes in Japan and in other regions is also discussed. Finally, the potential benefits and challenges are outlined from an energy policy point-of-view.
Experimental and Numerical Assessment of the Impact of an Integrated Active Pre-Swirl Generator on Turbocharger Compressor Performance and Operating Range
Authors: Stuart Charles , Spence Stephen , Teichel Sönke , Starke Andre
Published: June 2021

The implementation of increasingly stringent emissions and efficiency targets has seen engine downsizing and other complementary technologies increase in prevalence throughout the automotive sector. In order to facilitate ongoing improvements associated with the use of these strategies, delivering enhancements to the performance and stability of the turbocharger compressor when operating at low mass flow rates is of paramount importance. In spite of this, a few concepts (either active or passive) targeting such aims have successfully transitioned into use in automotive turbochargers, due primarily to the requirement for a very wide compressor-operating range. In order to overcome the operational limitations associated with existing pre-swirl generation devices such as inlet guide vanes, this study developed a concept comprising of an electrically driven axial fan mounted upstream of a standard automotive turbocharger centrifugal compressor. Rather than targeting a direct contribution to compressor boost pressure, the fan was designed to act as a variable pre-swirl generation device capable of being operated completely independently of the centrifugal impeller. It was envisioned that this architecture would allow efficient generation of the large pre-swirl angles needed for compressor surge margin extension and efficiency enhancement at low mass flow rate-operating points, while also facilitating the delivery of zero pre-swirl at higher mass flow rates to ensure no detrimental impact on performance at the rated power point of the engine. Having progressed through 1-D and 3-D aerodynamic modelling phases to understand the potential of the system, detailed component design and hardware manufacture were completed to enable an extensive experimental test campaign to be conducted. The experimental results were scrutinized to validate the numerical findings and to test the surge margin extension potential of the device. Compressor efficiency improvements of up to 3.0% pts were witnessed at the target-operating conditions.
Production of Agricultural Biogas with the Use of a Hydrodynamic Mixing System of a Polydisperse Substrate in a Reactor with an Adhesive Bed
Authors: Klimek Kamila , Kapłan Magdalena , Syrotyuk Serhiy , Konieczny Ryszard , Anders Dorota , Dybek Barbara , Karwacka Agnieszka , Wałowski Grzegorz
Published: June 2021

The properties, types, and physical and chemical aspects of pig slurry used in the fermentation process were presented. Characterization of the pig slurry microflora for a controlled biogas production process was performed. A pilot biogas treatment installation was presented on the example of a farm with 1100 Dan Bred fatteners kept in a grate system. The research was carried out to measure the biogas flow rate resulting from the reference pressure in the fermentor. An independent assessment of the amount of biogas and the pressure drop in the skeletal deposit was carried out. The basis for assessing the hydrodynamics of gas flow through the adhesive bed is the flow characteristic, which results from the pressure that forces this flow. In each case, the determination of this characteristic consists in determining the influence of the biogas stream on the value of this overpressure, equivalent to the pressure drop (it is tantamount to determining the total biogas flow resistance through the adhesive bed). The results of the measurements indicate the practical application of pig slurry-a substrate in a polydisperse system for the production of agricultural biogas in the context of renewable energies. The article indicates that the ferment was periodically mixed during the day, together with the fermentation of the ferment with fresh substrate. The tests were conducted for 49 days, thus demonstrating that it is more advantageous to mix the ferment hydrodynamically, obtaining a CH4 level of about 80%.
Renewable Energy Integration in Vietnam’s Power System: Generation Adequacy Assessment and Strategic Implications
Authors: Do Binh , Tran Thai , Nguyen Ninh
Published: June 2021

Vietnam is widely considered as an energy-intensive economy. Renewable energy integration has been set as an important goal in the country’s revised Power Development Plan 7 (PDP7). This study first conducted a generation adequacy assessment using the basic probabilistic modeling approach to evaluate how the generation fleet, as foreseen in the PDP7, can meet the demand, despite the fast-changing renewable energy sources (RES) generation. The adequacy of the generation was measured using the Loss of Load Expectation (LOLE, expressed in hours) index. The study then conducted in-depth interviews with key stakeholders to identify and propose efficient strategic approach and policy implementations for integration of RES into the current power system in Vietnam. The results suggested that three major pillars should be considered to ensure the success of RES integration: strategic objectives, structural reforms and system transformation.
A Tree-Ring-Based Assessment of Pinus armandii Adaptability to Climate Using Two Statistical Methods in Mt. Yao, Central China during 1961–2016
Authors: Peng Jianfeng , Li Jingru , Li Jinbao , Li Xuan , Cui Jiayue , Peng Meng , Huo Jiaxin , Yang Liu
Published: June 2021

Assessing the characteristics and limiting factors of tree growth is of practical significance for environmental studies and climatic reconstruction, especially in climate transition zones. In this study, four sites of Pinus armandii Franeh are investigated to understand regional climate-tree growth response in Mt. Yao, central China. Based on the high similarity of four residual chronologies and high correlations between chronologies and climatic factors, we analyzed the correlations of regional residual chronology with monthly climatic factors and the self-calibrating Palmer Drought Severity Index (scPDSI) from 1961–2016. The results indicate that the hydrothermal combination of prior August and current May and the scPDSI in May are main limiting factors of regional tree growth in Mt. Yao. The results of stepwise regression models also show that temperature and scPDSI in May are the main limiting factors of tree growth, but the limiting effect of scPDSI is more than temperature in this month. Through the analysis of the number of tree growth years corresponding to high temperature and high scPDSI, it was further confirmed that scPDSI in May is the main limiting factor on the growth of P. armandii in Mt. Yao. However, the influence of scPDSI in May has weakened, while temperature in May has increasingly significant influence on tree growth. The above findings will help improve our understanding of forest dynamics in central China under global climate change.
Generation of Gravity Waves by Pedal-Wavemakers
Authors: Vivanco Isis , Cartwright Bruce , Ledesma Araujo A. , Gordillo Leonardo , Marin Juan F.
Published: June 2021

Experimental wave generation in channels is usually achieved through wavemakers (moving paddles) acting on the surface of the water. Although practical for engineering purposes, wavemakers have issues: they perform poorly in the generation of long waves and create evanescent waves in their vicinity. In this article, we introduce a framework for wave generation through the action of an underwater multipoint mechanism: the pedal-wavemaking method. Our multipoint action makes each point of the bottom move with a prescribed pedalling-like motion. We analyse the linear response of waves in a uniform channel in terms of the wavelength of the bottom action. The framework naturally solves the problem of the performance for long waves and replaces evanescent waves by a thin boundary layer at the bottom of the channel. We also show that proper synchronisation of the orbital motion on the bottom can produce waves that mimic deep water waves. This last feature has been proved to be useful to study fluid–structure interaction in simulations based on smoothed particle hydrodynamics.
Characterization of Coffee Silver Skin as Potential Food-Safe Ingredient
Authors: Martuscelli Maria , Esposito Luigi , Di Mattia Carla , Ricci Antonella , Mastrocola Dino
Published: June 2021

By-products from the coffee industry are produced in large amounts each year. Among other wastes, coffee silver skin (CSS) is highly available and more stable due to its lower content of water. This research aimed to characterize coffee silver skin composition and evidence its potentiality for use as a food-safe ingredient in new formulations. Results showed an average total dietary fiber content of 50% but with a higher ratio for insoluble than soluble fiber. A high content of total phenolic compounds, chlorogenic acid, caffeine, and caffeic acid was found and correlated with the high measured antioxidant capacity. Moreover, minerals (e.g., calcium, magnesium, phosphorous, potassium, copper, iron, manganese) important for human wellbeing were found at a high level in CSS, while toxic minerals (e.g., nickel) were found at low levels. In conclusion, coffee silver skin could have an advantageous role for the recovery of valuable compounds and as a potential food-safe ingredient.
Adropin Slightly Modulates Lipolysis, Lipogenesis and Expression of Adipokines but Not Glucose Uptake in Rodent Adipocytes
Authors: Jasaszwili Mariami , Pruszyńska-Oszmałek Ewa , Wojciechowicz Tatiana , Strowski Mathias Z. , Nowak Krzysztof W. , Skrzypski Marek
Published: June 2021

Adropin is a peptide hormone which modulates energy homeostasis and metabolism. In animals with diet-induced obesity, adropin attenuates adiposity and improves lipid and glucose homeostasis. Adropin promotes the proliferation of rodent white preadipocytes and suppresses their differentiation into adipocytes. By contrast, the effects of adropin on mature white adipocytes are unknown. Therefore, we aimed to evaluate the effects of adropin on lipolysis, lipogenesis and glucose uptake in white rodent adipocytes. We assessed the effects of adropin on the mRNA expression of adiponectin, resistin and visfatin. White preadipocytes were isolated from male Wistar rats. Differentiated 3T3-L1 cells were used as a surrogate model of white adipocytes. Lipolysis was measured by the evaluation of glycerol and free fatty acid secretion using colorimetric kits. The effects of adropin on lipogenesis and glucose uptake were measured using radioactive-labelled glucose. The expression of adipokine mRNA was studied using real-time PCR. Our results show that adropin slightly promotes lipolysis in rat adipocytes and 3T3-L1 cells. Adropin suppresses lipogenesis in rat adipocytes without influencing glucose uptake. In addition, adropin stimulates adiponectin mRNA expression and suppresses the expression of resistin and visfatin. These results indicate that adropin may be involved in controlling lipid metabolism and adipokine expression in white rodent adipocytes.
Sex-Differences in Traumatic Brain Injury in the Absence of Tau in Drosophila
Authors: Shah Ekta J. , Gurdziel Katherine , Ruden Douglas M.
Published: June 2021

Traumatic brain injuries, a leading cause of death and disability worldwide, are caused by a severe impact to the head that impairs physiological and psychological function. In addition to severity, type and brain area affected, brain injury outcome is also influenced by the biological sex of the patient. Traumatic brain injury triggers accumulation of Tau protein and the subsequent development of Tauopathies, including Alzheimer’s disease and Chronic traumatic encephalopathy. Recent studies report differences in Tau network connections between healthy males and females, but the possible role of Tau in sex-dependent outcome to brain injury is unclear. Thus, we aimed to determine if Tau ablation would alleviate sex dependent outcomes in injured flies. We first assessed motor function and survival in tau knock-out flies and observed sex-differences in climbing ability, but no change in locomotor activity in either sex post-injury. Sex differences in survival time were also observed in injured tau deficient flies with a dramatically higher percent of female death within 24 h than males. Additionally, 3′mRNA-Seq studies in isolated fly brains found that tau deficient males show more gene transcript changes than females post-injury. Our results suggest that sex differences in TBI outcome and recovery are not dependent on the presence of Tau in Drosophila.