bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Value of Information in Status Update Systems
Authors: Zou Peng , Subramaniam Suresh
Published: March 2022

The age of information (AoI) is now well established as a metric that measures the freshness of information delivered to a receiver from a source that generates status updates. This paper is motivated by the inherent value of packets arising in many cyber-physical applications (e.g., due to precision of the information content or an alarm message). In contrast to AoI, which considers all packets are of equal importance or value, we consider status update systems with update packets carrying values as well as their generated time stamps. A status update packet has a random initial value at the source and a deterministic deadline after which its value vanishes (called ultimate staleness). In our model, the value of a packet either remains constant until the deadline or decreases in time (even after reception) starting from its generation to the deadline when it vanishes. We consider two metrics for the value of information (VoI) at the receiver: sum VoI is the sum of the current values of all packets held by the receiver, whereas packet VoI is the value of a packet at the instant it is delivered to the receiver. We investigate various queuing disciplines under potential dependence between value and service time and provide closed form expressions for both average sum VoI and packet VoI at the receiver. Numerical results illustrate the average VoI for different scenarios and relations between average sum VoI and average packet VoI.
Metastability of Synchronous and Asynchronous Dynamics
Authors: Cirillo Emilio Nicola Maria , Jacquier Vanessa , Spitoni Cristian
Published: March 2022

Metastability is a ubiquitous phenomenon in nature, which interests several fields of natural sciences. Since metastability is a genuine non-equilibrium phenomenon, its description in the framework of thermodynamics and statistical mechanics has progressed slowly for a long time. Since the publication of the first seminal paper in which the metastable behavior of the mean field Curie–Weiss model was approached by means of stochastic techniques, this topic has been largely studied by the scientific community. Several papers and books have been published in which many different spin models were studied and different approaches were developed. In this review, we focus on the comparison between the metastable behavior of synchronous and asynchronous dynamics, namely, stochastic processes in discrete time in which, at each time, either all the spins or one single spin is updated. In particular, we discuss how two different stochastic implementations of the very same Hamiltonian give rise to different metastable behaviors.
An Efficient and Accurate Multi-Sensor IF Estimator Based on DOA Information and Order of Fractional Fourier Transform
Authors: Khan Nabeel Ali , Ali Sadiq , Choi Kwonhue
Published: March 2022

Instantaneous frequency in multi-sensor recordings is an important parameter for estimation of direction of arrival estimation, source separation, and sparse reconstruction. The instantaneous frequency estimation problem becomes challenging when signal components have close or overlapping signatures and the number of sensors is less than the number of sources. In this study, we develop a computationally efficient method that exploits the direction of the IF curve in addition to the angle of arrival as additional features for the accurate tracking of IF curves. Experimental results show that the proposed scheme achieves better accuracy compared to the-state-of-art method in terms of mean square error (MSE) with a slight increase in the computational cost, i.e., the proposed method achieves MSE of −50 dB at the signal to noise ratio of 0 dB whereas the existing method achieves the MSE of −38 dB.
CTRL: Closed-Loop Transcription to an LDR via Minimaxing Rate Reduction
Authors: Dai Xili , Tong Shengbang , Li Mingyang , Wu Ziyang , Psenka Michael , Chan Kwan Ho Ryan , Zhai Pengyuan , Yu Yaodong , Yuan Xiaojun , Shum Heung-Yeung , Ma Yi
Published: March 2022

This work proposes a new computational framework for learning a structured generative model for real-world datasets. In particular, we propose to learn a Closed-loop Transcriptionbetween a multi-class, multi-dimensional data distribution and a Linear discriminative representation (CTRL) in the feature space that consists of multiple independent multi-dimensional linear subspaces. In particular, we argue that the optimal encoding and decoding mappings sought can be formulated as a two-player minimax game between the encoder and decoderfor the learned representation. A natural utility function for this game is the so-called rate reduction, a simple information-theoretic measure for distances between mixtures of subspace-like Gaussians in the feature space. Our formulation draws inspiration from closed-loop error feedback from control systems and avoids expensive evaluating and minimizing of approximated distances between arbitrary distributions in either the data space or the feature space. To a large extent, this new formulation unifies the concepts and benefits of Auto-Encoding and GAN and naturally extends them to the settings of learning a both discriminative and generative representation for multi-class and multi-dimensional real-world data. Our extensive experiments on many benchmark imagery datasets demonstrate tremendous potential of this new closed-loop formulation: under fair comparison, visual quality of the learned decoder and classification performance of the encoder is competitive and arguably better than existing methods based on GAN, VAE, or a combination of both. Unlike existing generative models, the so-learned features of the multiple classes are structured instead of hidden: different classes are explicitly mapped onto corresponding independent principal subspaces in the feature space, and diverse visual attributes within each class are modeled by the independent principal components within each subspace.
Causal Transmission in Reduced-Form Models
Authors: Bazinas Vassilios , Nielsen Bent
Published: March 2022

We propose a method to explore the causal transmission of an intervention through two endogenous variables of interest. We refer to the intervention as a catalyst variable. The method is based on the reduced-form system formed from the conditional distribution of the two endogenous variables given the catalyst. The method combines elements from instrumental variable analysis and Cholesky decomposition of structural vector autoregressions. We give conditions for uniqueness of the causal transmission.
A Review of the State of the Art of Industrial Microgrids Based on Renewable Energy
Authors: Gutiérrez-Oliva Daniel , Colmenar-Santos Antonio , Rosales-Asensio Enrique
Published: March 2022

Electric microgrids based mainly on renewable energies have seen a big expansion in recent years due to the great advantages they present against fossil fuels. Nowadays different governments are becoming aware of the use of environmentally friendly energies, so progressive investment has been granted to the consumers in Spain. Many microgrids have been installed in both connected and isolated circumstances, and this fact brings new challenges regarding the technical and economic points of view. This study aims to delve into electrical microgrids based on renewable energies applied in industrial facilities through a review of the literature associated with the study of general microgrids. It later focuses on the relationships between renewable energies and industrial environments. A brief reference is made to the use of energy storage systems in industrial installations depicting the most used systems. This paper presents a review of the state of the art of microgrids from distributed energy resources technologies to industrial microgrids optimization, with the primary objective of providing insight on current trends and directions in research and further identifying areas in need of further development.
Dual Voltage Forward Topology for High Efficiency at Universal Mains
Authors: Ezra Noam , Werner Toine , Long Teng
Published: March 2022

This paper introduces a forward converter aimed at the universal mains voltages, i.e., 220–230 Vac and 115 Vac, named the ‘dual voltage forward converter’. The suggested converter has a narrow dynamic range at the universal mains voltages, which results in lower stress on devices, optimal duty cycles, and better overall efficiency. The topology comprises two primary power loops reconfigurable by additional two-state switches and a passive diode, which allows the converter to run in parallel or in series modes and increase the performance over the full universal mains range of 90–265 Vac. The utilization of the devices is better, as they experience lower voltage and current stress by supporting two optimized working points. A converter operating at 100 kHz with an output power of 75 W and output voltage of 12 Vdc was designed and tested. The results were compared with a conventional forward converter with the identical specification. The results at the low mains were similar between the converters; however, at the high mains, the efficiency improvement was between 5% and 23%.
Accumulatively Increasing Sensitivity of Ultrawide Instantaneous Bandwidth Digital Receiver with Fine Time and Frequency Resolution for Weak Signal Detection
Authors: Wu Chen , Tang Taiwen , Elangage Janaka , Krishnasamy Denesh
Published: March 2022

It is always an interesting research topic for digital receiver (DRX) designers to develop a DRX with (1) ultrawide instantaneous bandwidth (IBW), (2) high sensitivity, (3) fine time-of-arrival-measurement resolution (TMR), and (4) fine frequency-measurement resolution (FMR) for weak signal detection. This is because designers always want their receivers to have the widest possible IBW to detect far away and/or weak signals. As the analog-to-digital converter (ADC) rate increasing, the modern DRX IBW increases continuously. To improve the signal detection based on blocking FFT (BFFT) method, this paper introduces the new concept of accumulatively increasing receiver sensitivity (AIRS) for DRX design. In AIRS, a very large number of frequency-bins can be used for a given IBW in the time-to-frequency transform (TTFT), and the DRX sensitivity is cumulatively increased, when more samples are available from high-speed ADC. Unlike traditional FFT-based TTFT, the AIRS can have both fine TMR and fine FMR simultaneously. It also inherits all the merits of the BFFT, which can be implemented in an embedded system. This study shows that AIRS-based DRX is more efficient than normal FFT-based DRX in terms of using time-domain samples. For example, with a probability of false alarm rate of 10−7, for N=220 frequency-bins with TMR = 50 nSec, FMR = 2.4414 KHz, IBW > 1 GHz and ADC rate at 2.56 GHz, AIRS-based DRX detects narrow-band signals at about −42 dB of input signal-to-noise ratio (Input-SNR), and just uses a little less than N/2 real-samples. However, FFT-based DRX have to use all N samples. Simulation results also show that AIRS-based DRX can detect frequency-modulated continuous wave signals with ±0.1, ±1, ±10 and ±100 MHz bandwidths at about −39.4, −35.1, −30.2, and −25.5 dB of Input-SNR using about 264.6 K, 104.7 K, 40.2 K and 18.3 K real-samples, respectively, in 220 frequency-bins for TTFT.
The Hydrolysis of Ball-Milled Aluminum–Bismuth–Nickel Composites for On-Demand Hydrogen Generation
Authors: Davies Jamey , Du Preez Stephanus P. , Bessarabov Dmitri G.
Published: March 2022

The hydrolysis of aluminum (Al) is a promising method for on-demand hydrogen generation for low-power proton exchange membrane fuel cell (PEMFC) applications. In this study, Al composites were mechanochemically activated using bismuth (Bi) and nickel (Ni) as activation compounds. The main objective was to determine the effects of Bi and Ni on Al particles during mechanochemical processing, and the hydrolysis activity of the Al-Bi-Ni composites. Successfully formulated ternary Al-Bi-Ni composites were hydrolyzed with de-ionized water under standard ambient conditions to determine the reactivity of the composite (extent of hydrogen production). Scanning electron microscopy (SEM) showed that Bi and Ni were distributed relatively uniformly throughout the Al particles, resulting in numerous micro-galvanic interactions between the anodic Al and cathodic Bi/Ni during hydrolysis reaction. The addition of >1 wt% Ni resulted in incomplete activation of Al, and such composites were non-reactive. All successfully prepared composites had near-complete hydrogen yields. X-ray diffraction (XRD) showed that no mineralogical interaction occurred between Al, Bi, and/or Ni. The main phases detected were Al, Bi, and minute traces of Ni (ascribed to low Ni content). In addition, the effect of the mass ratio (mass Al:mass water) and water quality were also determined.
Experiment and Model of Conductivity Loss of Fracture Due to Fine-Grained Particle Migration and Proppant Embedment
Authors: Zhang Weidong , Zhao Qingyuan , Guan Xuhui , Wang Zizhen , Wang Zhiwen
Published: March 2022

In weakly cemented reservoirs or coal-bed methane reservoirs, the conductivity of hydraulic fractures always declines after a period of production, which greatly influences gas production. In this paper, a comprehensive model considering fine-grained particle migration and proppant embedment is proposed to give a precise prediction for conductivity decline. Then, an experiment was conducted to simulate this process. A published experiment using coal fines was also tested and simulated. The results indicate that both fine-grained particle migration and proppant embedment have great negative effect on conductivity of fractures in weakly cemented sandstone and coal-bed methane reservoirs. The formulation we proposed matches the experimental data smoothly and can be widely used in the prediction of conductivity decline in weakly cemented sandstone and coal-bed methane reservoirs. In order to discuss the influencing factors of the filtration coefficient in the particle transport model, a porous media network model was established based on the theoretical model. The simulation results show that the filtration coefficient increases with the increase in particle size and/or throat size, and the filtration coefficient increases with the decrease in the fluid velocity. At the same time, it was found that the large larynx did not easily cause particle retention. Large size particles tend to cause particle retention.
Comparison of Three-Dimensional Numerical Methods for Modeling of Strut Effect on the Performance of a Vertical Axis Wind Turbine
Authors: Aihara Aya , Mendoza Victor , Goude Anders , Bernhoff Hans
Published: March 2022

This paper compares three different numerical models to evaluate their accuracy for predicting the performance of an H-rotor vertical-axis wind turbine (VAWT) considering the influence of struts. The strut of VAWTs is one factor that makes the flow feature around the turbine more complex and thus influences the rotor performance. The focus of this study is placed on analyzing how accurately three different numerical approaches are able to reproduce the force distribution and the resulting power, taking the strut effect into account. For the 12 kW straight-bladed VAWT, the blade force is simulated at three tip speed ratios by the full computational fluid dynamics (CFD) model based on the Reynolds-averaged Navier–Stokes (RANS) equations, the actuator line model (ALM), and the vortex model. The results show that all the models do not indicate a significant influence of the struts in the total force over one revolution at low tip speed ratio. However, at middle and high tip speed ratio, the RANS model reproduces the significant decrease of the total tangential force that is caused due to the strut. Additionally, the RANS and vortex models present a clear influence of the struts in the force distribution along the blade at all three tip speed ratios investigated. The prediction by the ALM does not show such distinctive features of the strut impact. The RANS model is superior to the other two models for predicting the power coefficient considering the strut effect, especially at high tip speed ratio.
Exhaust Gas Temperature Pulsations of a Gasoline Engine and Its Stabilization Using Thermal Energy Storage System to Reduce Emissions
Authors: Bohm Michael , Stetina Josef , Svida David
Published: March 2022

Modern automotive gasoline engines have highly efficient after-treatment systems that reduce exhaust gas emissions. However, this efficiency greatly depends on the conditions of the exhaust gas, mainly the temperature and air–fuel ratio. The temperature instability during transient conditions may cause a reduction in the efficiency of the three-way catalyst (TWC). By using a thermal energy storage system before TWC, this negative effect can be suppressed. In this paper, the effects of the temperature stabilization on the efficiency of the three-way catalyst were investigated on a 1-D turbocharged gasoline engine model, with a focus on fuel consumption and emissions. The thermal energy storage system (TESS) was based on PCM materials and was built in the exhaust between the turbine and TWC to use the energy of the exhaust gas. Three different materials were picked up as possible mediums in the storage system. Based on the results, the usage of a TESS in a gasoline after-treatment system has shown great potential in improving TWC efficiency. This approach can assist the catalyst to operate under optimal conditions during the drive. In this study, it was found that facilitating the heat transfer between the PCM and the catalyst can significantly improve the emissions’ reduction performance by avoiding the catalyst to light out after the cold start. The TESS with PCM H430 proved to reduce the cumulative CO and HC emissions by 8.2% and 10.6%, respectively, during the drive. Although a TES system increases the after-treatment cost, it can result in emission reductions and fuel consumption over the vehicle’s operating life.
Effects of Heating Temperature on the Isothermal Performance of a Potassium Concentric Annular Heat Pipe
Authors: Zhang Hongzhe , Ye Fang , Guo Hang , Yan Xiaoke
Published: March 2022

For high-precision thermocouple calibration, the uniformity of the temperature field provided by the metal temperature equalizing block is low, and the structure of the gas-controlled heat pipe is complex. In order to improve the thermocouple calibration equipment, heat pipe technology can be used to provide the stability and uniformity of the temperature field of the equipment. The concentric annular heat pipe (CAHP) is completely placed in the heating furnace to provide a uniform temperature field, and limited studies consider this heating mode for alkali metal CAHPs. Specifically, no information is available on the effect of heating temperatures on the temperature distribution of the internal pipe of potassium CAHP. In this study, a temperature comparison based on potassium CAHP for high-precision thermocouple calibration was manufactured. The temperature stability and temperature uniformity of CAHP were measured, and the effects of heating temperature and heating mode on the isothermal performance in the metering wells of CAHP were studied. The CAHP can provide a very stable and uniform temperature field. Under uniform heating at 400 °C, the maximum temperature difference within 16 cm was 0.174 °C. After adjusting the heating mode, the maximum temperature difference was within 16 cm 0.095 °C. The CAHP can effectively reduce the influence of heating temperature fluctuation on the temperature in the metering well; the maximum temperature change rate of the metering wells affected by the heating furnace temperature was 0.0942 °C/°C.
Carbon Emission Efficiency and Low-Carbon Optimization in Shanxi Province under “Dual Carbon” Background
Authors: Guo Xiaojia , Wang Xin , Wu Xueling , Chen Xingpeng , Li Ya
Published: March 2022

As an important energy base in China, Shanxi Province, in its economic development, has depended heavily on coal resources. However, enormous coal consumption produces a large amount of carbon dioxide and an aggravated ecological problem. In this paper, the super efficiency slack-based measure and data envelopment analysis (SBM-DEA) model and Malmquist index were used to calculate the energy consumption and carbon emission efficiency of 11 prefecture-level cities in Shanxi in the period from 2000 to 2020. The results were as follows: (1) The primary form of energy consumption in Shanxi Province is the burning of coal, and the carbon emission efficiencies of the 11 prefecture-level cities are quite different. The technical efficiency, technological progress, and total factor productivity of Taiyuan and Shuozhou were found to be greater than 1 compared to other cities in Shanxi. (2) On the whole, although the carbon emission rate of Shanxi Province has slowed down, it still faces the problems of a large total emission base, high carbon emission intensity, and low efficiency of the unit carbon emission output. Industrial structure is the key factor restricting improvements in the efficiency of carbon emissions in Shanxi Province. (3) From the spatial and temporal evolution of the carbon emission efficiency in Shanxi Province, we can see that the carbon emission efficiency of the whole province gradually dispersed and improved from the central and northern regions to the southern regions during the period of 2000–2020. In order to achieve a low-carbon economy, Shanxi Province must optimize its industrial structure, accelerate research and development in low-carbon technologies, adjust the energy structure, and promote the construction of an energy supply system with clean low-carbon energy as the main source.
Correlations and Numerical Modeling of Stacked Woven Wire-Mesh Porous Media for Heat Exchange Applications
Authors: G Trilok , Srinivas Kurma Eshwar Sai , Harikrishnan Devika , N Gnanasekaran , Mobedi Moghtada
Published: March 2022

Metal foams have gained attention due to their heat transfer augmenting capabilities. In the literature, correlations describing relations among their morphological characteristics have successfully been established and well discussed. However, collective expressions that categorize stacked wire mesh based on their morphology and thermo-hydraulic expressions required for numerical modeling are less explored in the literature. In the present study, cross relations among the morphological characteristics of stacked wire-mesh were arrived at based on mesh-size, wire diameter and stacking type, which are essential for describing the medium and determining key input parameters required for numerical modeling. Furthermore, correlation for specific surface area, a vital parameter that plays a major role in interstitial heat transfer, is provided. With the arrived correlations, properties of stacked wire-mesh samples of orderly varied mesh-size and porosity are obtained for various stacking scenarios, and corresponding thermo-hydraulic parameters appearing in the governing equations are evaluated. A vertical channel housing the categorized wire-mesh porous media is numerically modeled to analyze thermal and flow characteristics of such a medium. The proposed correlations can be used in confidence to evaluate thermo-hydraulic parameters appearing in governing equations in order to numerically model various samples of stacked wire-mesh types of porous media in a variety of heat transfer applications.
Onshore Wind Farm Development: Technologies and Layouts
Authors: Haces-Fernandez Francisco , Cruz-Mendoza Mariee , Li Hua
Published: March 2022

Significantly growing wind energy is being contemplated as one of the main avenues to reduce carbon footprints and decrease global risks associated with climate change. However, obtaining a comprehensive perspective on wind energy considering the many diverse factors that impact its development and growth is challenging. A significant factor in the evolution of wind energy is technological advancement and most previous reviews have focused on this topic. However, wind energy is influenced by a host of other factors, such as financial viability, environmental concerns, government incentives, and the impact of wind on the ecosystem. This review aims to fill a gap, providing a comprehensive review on the diverse factors impacting wind energy development and providing readers with a holistic panoramic, furnishing a clearer perspective on its future growth. Data for wind energy was evaluated by applying pivot data analytics and geographic information systems. The factors impacting wind energy growth and development are reviewed, providing an overview of how these factors have impacted wind maturity. The future of wind energy development is assessed considering its social acceptance, financial viability, government incentives, and the minimization of the unintended potential negative impacts of this technology. The review is able to conclude that wind energy may continue growing all over the world as long as all the factors critical to its development are addressed. Wind power growth will be supported by stakeholders’ holistic considerations of all factors impacting this industry, as evaluated in this review.
Understanding Sustainable Energy in the Context of Smart Cities: A PRISMA Review
Authors: Cortese Tatiana Tucunduva Philippi , Almeida Jairo Filho Sousa de , Batista Giseli Quirino , Storopoli José Eduardo , Liu Aaron , Yigitcanlar Tan
Published: March 2022

In the context of smart cities, sustainability is an essential dimension. One of the ways to achieve sustainability and reduce the emission of greenhouse gases in smart cities is through the promotion of sustainable energy. The demand for affordable and reliable electrical energy requires different energy sources, where the cost of production often outweighs the environmental factor. This paper aims to investigate the ways smart cities promote sustainability in the electricity sector. For this, a systematic literature review using the PRISMA protocol was employed as the methodological approach. In this review, 154 journal articles were thoroughly analyzed. The results were grouped according to the themes and categorized into energy efficiency, renewable energies, and energy and urban planning. The study findings revealed the following: (a) global academic publication landscape for smart city and energy sustainability research; (b) unbalanced publications when critically evaluating geographical continents’ energy use intensity vs. smart cities’ energy sustainability research outcomes; (c) there is a heavy concentration on the technology dimension of energy sustainability and efficiency, and renewables topics in the literature, but much less attention is paid to the energy and urban planning issues. The insights generated inform urban and energy authorities and provide scholars with directions for prospective research.
Energy Efficiency and Industry 4.0 in Wood Industry: A Review and Comparison to Other Industries
Authors: Haddouche Mohamed , Ilinca Adrian
Published: March 2022

This paper presents a literature review of recent research on introducing the Industry 4.0 approach to improving energy efficiency, especially in the wood industry. While researchers focus on processes, service, and customer concepts, the effect on energy consumption is less addressed in these studies and applications. This paper focuses on previous works that discuss how to apply Industry 4.0 concepts to energy issues, such as to achieve better efficiency and performance for the industry in general and the wood industry in particular. The complexity of the study requires a multistep development. First, we define each concept separately and the relationships between them. Second, we apply a search algorithm to find related articles with specific terms, and then use the PRISMA method to select the most important ones, eliminating duplicates and excluding articles that do not mention energy efficiency and Industry 4.0 in the manufacturing or wood industry. Third, we explain and categorize the results and consolidate the study with brief examples from other industries. Finally, we conclude the study by mentioning the limitations and perspectives.
Feasibility of Replacing Nuclear and Fossil Fuel Energy with Offshore Wind Energy: A Case for Taiwan
Authors: Yue Cheng-Dar , Wang I-Chun , Huang Jhou-Sheng
Published: March 2022

Adequate recognition of the offshore wind energy potential may help coastal states frame proper energy policies for replacing nuclear and fossil fuel energy. In this study, we examined the application potential of the offshore wind energy generated by 31 offshore wind farms designated by the Taiwanese government for future exploitation. Our findings indicate that offshore wind energy (through its substantial power generation volume and capacity factor) can play the most pivotal role in future power generation for Taiwan. A total of 59.3 TWh of electricity produced from offshore wind energy and solar photovoltaics (PVs) each year could replace the power generated from nuclear energy by 2025. Coal-fired power generation could be replaced by offshore wind energy and other renewables by 2032. The full exploitation of offshore wind farms as detailed in this study (103.4 TWh/year), together with other renewables, could reduce the share of liquefied natural gas-fired power generation to 5.6% of the total Taiwanese power supply by 2040. Realizing the ultimate target of 100% carbon-neutral power generation would rely mainly on a further decrease in electricity consumption per unit of gross domestic product and the expansion of offshore wind energy and geothermal energy.
Reserve-Constrained Unit Commitment Considering Adjustable-Speed Pumped-Storage Hydropower and Its Economic Effect in Korean Power System
Authors: Kim Woo-Jung , Lee Yu-Seok , Chun Yeong-Han , Jeong Hae-Seong
Published: March 2022

The Korean government has declared the goal of net-zero-carbon emissions with a focus on renewable energy expansion. However, a high proportion of baseload generators and an increasing proportion of variable renewable energy (VRE) may cause problems in the power system operation owing to the low cycling capability of baseload generators and variability of VRE. To maintain system reliability, the government is planning to construct pumped-storage hydropower (PSH) plants, which can provide flexibility to the system. This study evaluated the operating cost savings obtained by different types of PSH: the adjustable-speed PSH (AS-PSH) and fixed-speed PSH (FS-PSH), based on the duck-curve phenomenon and the increase in spinning reserve requirement. In this study, the reserve-constrained unit commitment was formulated using a mixed-integer-programming considering the operational characteristics of AS-PSH and conventional generators. To consider the duck-shaped net-load environment, the projected VRE output data were calculated through physical models of wind turbines and photovoltaic modules. The operating costs for the non-PSH, FS-PSH, and AS-PSH construction scenarios were KRW 43,129.38, 40,038.44, and 34,030.46, respectively. The main factor that derived this difference was determined to be the primary reserve of AS-PSH’s pumping mode.
Intensity and Biodiversity: The ‘Green’ Potential of Agriculture and Rural Territories in Poland in the Context of Sustainable Development
Authors: Chmieliński Paweł , Wrzaszcz Wioletta , Zieliński Marek , Wigier Marek
Published: March 2022

In the paper we provide an analysis of the potential of agricultural holdings for biomass production, an assessment of the level of farm sustainability and a description of the farming conditions of agricultural holdings depending on the degree of natural valuation of a given area. The approach makes it possible to assess the level of sustainability of farms, also in the context of their potential and taking into account the quality of the production space and its importance for increasing biodiversity. We use public and unpublished data of Statistics Poland (2005, 2007, 2016) as well as data on farms keeping accounts for the Polish FADN in 2016–2018. The paper shows that although concentration processes are progressing, farm productivity is increasing, but this is linked to specialisation, leading to efficient management of labour and land resources. Nevertheless, the decreasing number of farms with proper winter vegetation cover and optimal balances was confirmed. The farming conditions of the farms should take into account the share and degree of natural value of the production space of the areas (municipalities) in which they are located. The study found that farms in municipalities with a high share of high natural value farmland (HNVf) areas, compared to the other municipalities, characterized by lower livestock density per ha UAA, which indicates their less intensive organisation of agricultural production. Moreover, in these municipalities, as their natural value increased, the share of forests and waters in the total area increased and the share of permanent grassland in the total area decreased slightly.
Improvement of the Control of a Grid Connected Photovoltaic System Based on Synergetic and Sliding Mode Controllers Using a Reinforcement Learning Deep Deterministic Policy Gradient Agent
Authors: Nicola Marcel , Nicola Claudiu-Ionel , Selișteanu Dan
Published: March 2022

This article presents the control of a grid connected PV (GC-PV) array system, starting from a benchmark. The control structure used in this article was a cascade-type structure, in which PI or synergetic (SYN) controllers were used for the inner control loop of id and iq currents and PI or sliding mode control (SMC) controllers were used for the outer control loop of the udc voltage from the DC intermediate circuit. This paper presents the mathematical model of the PV array together with the main component blocks: simulated inputs for the PV array; the PV array itself; the MPPT algorithm; the DC-DC boost converter; the voltage and current measurements for the DC intermediate circuit; the load and connection to power grid; the DC-AC converter; and the power grid. It also presents the stages of building and training the reinforcement learning (RL) agent. To improve the performance of the control system for the GC-PV array system without using controllers with a more complicated mathematical description, the advantages provided by the RL agent on process controls could also be used. This technique does not require exact knowledge of the mathematical model of the controlled system or the type of uncertainties. The improvement in the control system performance for the GC-PV array system, both when using simple PI-type controllers or complex SMC- and SYN-type controllers, was achieved using an RL agent based on the Deep Deterministic Policy Gradient (DDPG). The variant of DDPG used in this study was the Twin-Delayed (TD3). The improvement in performance of the control system were obtained by using the correction command signals provided by the trained RL agent, which were added to the command signals ud, uq and idref. The parametric robustness of the proposed control system based on SMC and SYN controllers for the GC-PV array system was proven in the case of a variation of 30% caused by the three-phase load. Moreover, the results of the numerical simulations are shown comparatively and the validation of the synthesis of the proposed control system was obtained. This was achieved by comparing the proposed system with a software benchmark for the control of a GC-PV array system performed in MATLAB Simulink. The numerical simulations proved the superiority of the performance of control systems that use the RL-TD3 agent.
Life Cycle Assessment and Energy Balance of a Polygeneration Plant Fed with Lignocellulosic Biomass of Cynara cardunculus L.
Authors: Barros Lovate Temporim Ramoon , Cavalaglio Gianluca , Petrozzi Alessandro , Coccia Valentina , Iodice Paola , Nicolini Andrea , Cotana Franco
Published: March 2022

This article aims to present an evaluation of the environmental performance of a combustion polygeneration plant fed with lignocellulosic material from cardoon (Cynara cardunculus L.) through the technique of Life Cycle Assessment (LCA). The system boundaries encompassed macro-phases of crop production, transportation, and polygeneration processes that were able to produce 100 kW of electricity, a residual thermal energy recovery system and district heating and cooling with 270 kW of heating, and a 140 kW of cooling. The LCA was performed using Cumulative Energy Demand and ReCiPe Life Cycle Impact Assessment methods through midpoint and endpoint indicators. From 2000 h/year, 165.92 GJ of electricity and 667.23 GJ of primary energy were consumed, and 32.82 tCO2eq were emitted. The rates of Greenhouse Gas (GHG) and energy demand per MJ produced were 0.08 MJSE/MJPD, 0.30 MJPE/MJPD, and 0.01 kgCO2eq/MJPD. According to the ReCiPe method, the impact categories with the highest impact loads were Terrestrial ecotoxicity (2.44%), Freshwater ecotoxicity (32.21%), Marine ecotoxicity (50.10%), Human carcinogenic toxicity (8.75%), and Human non-carcinogenic toxicity (4.76%). Comparing the same energy outputs produced by Italian power and gas grids, the proposed polygeneration plant was able to reduce primary energy demand and GHG emissions by 80 and 81%, respectively, in addition to reducing the emissions of the five main categories of impacts by between 25 and 73%.
On-Road and Laboratory Emissions from Three Gasoline Plug-In Hybrid Vehicles—Part 1: Regulated and Unregulated Gaseous Pollutants and Greenhouse Gases
Authors: Selleri Tommaso , Melas Anastasios D. , Franzetti Jacopo , Ferrarese Christian , Giechaskiel Barouch , Suarez-Bertoa Ricardo
Published: March 2022

Road transport is a relevant source of greenhouse gas emissions. In order to meet the European decarbonisation targets, the share of electrified vehicles, including battery electric vehicles and plug-in hybrid electric vehicles (PHEVs), is rapidly growing, becoming the second most popular powertrain in the European market. PHEVs are of interest since they are expected to deliver a reduction in gaseous pollutants such as NOx as well as in greenhouse gases such as CO2. Herein, we explored both categories of emissions for three PHEVs with gasoline direct-injection engines, meeting the latest European emission standards (Euro 6d and Euro 6d-TEMP). They were studied in laboratory and on the road, in different modalities and temperatures. All tested vehicles met the Euro 6 emission limits in the Worldwide Harmonised Light-Duty Vehicles Test Procedure (WLTP) and the real driving emissions (RDE) test procedure. Still, when their internal combustion engine ignited even for a few km, their emissions were comparable to, and in some cases higher than, the average emissions reported for a fleet of eight conventional Euro 6d-TEMP gasoline direct-injection vehicles. The tested PHEVs presented similar trends to those of conventional vehicles, such as the increase in all pollutants considered at low ambient temperature or the high CO emissions during acceleration events, concomitantly with NH3. Moreover, depending on the boundary conditions, emissions were higher for the vehicles with a battery fully charged with respect to tests performed with the depleted battery. Furthermore, the use of an operating mode that allowed charging the vehicles’ high voltage battery using the internal combustion engine had a very strong impact on the vehicles’ CO2 emissions, offsetting the benefits in terms of greenhouse gas reduction demonstrated in other conditions. The results indicate that for the sample tested, the expected reduction in pollutants emission due to the presence of a hybrid gasoline-electric traction seemed in some cases limited, also showing high variability. CO2 emissions were also affected by the initial state of charge of the vehicles’ high voltage battery as well as from the user-selectable operating mode, also in this case with high variability.
Environmental Impact Assessment and Classification of 48 V Plug-in Hybrids with Real-Driving Use Case Simulations
Authors: Frambach Tobias , Kleisch Ralf , Liedtke Ralf , Schwarzer Jochen , Figgemeier Egbert
Published: March 2022

Plug-in hybrid electric vehicles (PHEVs) are commonly operated with high-voltage (HV) components due to their higher power availability compared to 48 V-systems. On the contrary, HV-powertrain components are more expensive and require additional safety measures. Additionally, the HV system can only be repaired and maintained with special equipment and protective gear, which is not available in all workshops. PHEVs based on a 48 V-system level can offer a reasonable compromise between the greenhouse gas (GHG) emission-saving potential and cost-effectiveness in small- and medium-sized electrified vehicles. In our study, the lifecycle emissions of the proposed 48 V PHEV system were compared to a conventional vehicle, 48 V HEV, and HV PHEV for individual driving use cases. To ensure a holistic evaluation, the analysis was based on measured real-driving cycles including Global Position System (GPS) map-matched slope profiles for a parallel hybrid. Optimal PHEV battery capacities were derived for the individual driving use cases. The analysis was based on lifecycle emissions for 2020 and 2030 in Europe. The impact analysis revealed that 48 V PHEVs can significantly reduce GHG emissions compared to vehicles with no charging opportunity for all use cases. Furthermore, the findings were verified for two vehicle segments and two energy mix scenarios. The 48 V PHEVs can therefore complement existing powertrain portfolios and contribute to reaching future GHG emission targets.
The Embedded System to Control the Illuminance of an Office Workplace with LED Light Sources
Authors: Górecki Krzysztof , Ptak Przemysław , Wnuczko Sylwia
Published: March 2022

In the paper, an embedded system dedicated to control lighting of the workplace is proposed. The construction of the considered lighting system with a power LED (Light Emitting Diode) and the idea of its control are presented. Some results of investigations of the constructed lighting system, particularly those of the measurements of its optical and electrical parameters, are shown and discussed. The presented results show that by using this system, it is possible to obtain a high value of lighting uniformity in the workplace at different values of the main lighting in the room. The control is fast, and none of the reaction times achieved during the tests exceeded even 1 s while ensuring a smooth change. Although the layout and algorithms used are simple, it can be considered an advantage as they do not introduce unnecessary complexity while meeting all the requirements of standards. A discussion of the obtained results is given, particularly in the range of energy savings.
Control Strategies Applied to Active Power Filters
Authors: Buła Dawid , Zygmanowski Marcin
Published: March 2022

Almost 50 years have passed since the first works on active power filters were published [...]
Experimental Performance Analysis of Wi-SUN Channel Modelling Applied to Smart Grid Applications
Authors: Tangsunantham Natthanan , Pirak Chaiyod
Published: March 2022

The grid operation and communication network are essential for smart grids (SG). Wi-SUN channel modelling is used to evaluate the performance of Wi-SUN smart grid networks, especially in the last-mile communication. In this article, the distribution approximation of the received signal strength for IEEE 802.15.4g Wi-SUN smart grid networks was investigated by using the Rician distribution curve fitting with the accuracy improvement by the biased approximation methodology. Specifically, the Rician distribution curve fitting was applied to the received signal strength indicator (RSSI) measurement data. With the biased approximation method, the Rician K-factor, a non-centrality parameter (rs), and a scale parameter (σ) are optimized such that the lower value of the root-mean squared error (RMSE) is acheived. The environments for data collection are selected for representing the location of the data concentrator unit (DCU) and the smart meter installation in the residential area. In summary, the experimental results with the channel model parameters are expanded to the whole range of Wi-SUN’s frequency bands and data rates, including 433.92, 443, 448, 923, and 2440 MHz, which are essential for the successful data communication in multiple frequency bands. The biased distribution approximation models have improved the accuracy of the conventional model, by which the root mean-squared error (RMSE) is reduced in the percentage range of 0.47–3.827%. The proposed channel models could be applied to the Wi-SUN channel simulation, smart meter installation, and planning in smart grid networks.
Cost Functions for Generation Dispatching in Microgrids for Non-Interconnected Zones in Colombia
Authors: Hoyos-Velandia Cristian , Ramirez-Hurtado Lina , Quintero-Restrepo Jaime , Moreno-Chuquen Ricardo , Gonzalez-Longatt Francisco
Published: March 2022

Generation dispatching is a challenge in islanded microgrids due to the operational and economic restrictions in isolated zones. Furthermore, the impact of usual operational network changes in topology, load demand, and generation availability may become significant considering the grid size. This research paper presents a detailed multiple cost function modeling methodology of an optimal power flow algorithm applied to a non-interconnected zone in Colombia. The optimal power flow (OPF) formulation includes cost functions related to renewable resources as presented in the isolated zone and a complete model of the charging and discharging of batteries. Additionally, the flexibility of the proposal is tested using three different network topologies with a characteristic daily load curve from the zone. The main contribution of this paper lies in the implementation of an optimal power flow including cost functions of renewable sources for isolated microgrids. A test case for a non-interconnected zone in Colombia is performed for various operation cases.
A Study on the Effect of Initial Temperature on Combustion Characteristics of RDX Based on the Optical Diagnosis Methods
Authors: Yan Zhiyu , Song Chen , Li Qianqian , Niu Yulei , Wang Jinhua , Huang Zuohua
Published: March 2022

The purpose of this work is to investigate the effect of different initial temperatures on the combustion characteristics of RDX materials. In the experiments, the electric heating plate below the RDX samples was controlled so that the initial temperatures were set to be 298, 323, 373, 423, and 473 K (below the material melting point), respectively. Three optical diagnostic methods were employed to capture the ignition process, flame thermal radiation, and NO distribution in the flame at different conditions. The results show that the increase in initial temperature can improve the reaction rate, shorten the ignition delay time, and increase the flame combustion intensity and speed, because of the earlier evaporation and pyrolysis process in the RDX samples. Increasing the initial temperature also enhances the thermal effect of the flame, which is related to the generation and consumption of NO to a certain extent.