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Energies, Volume 15, Issue 14 (July-2 2022) – 379 articles

Cover Story (view full-size image): Imagine that overnight the share of renewable energy resources reaches 100% and that all vehicles are replaced by electric vehicles; what will happen next? Are the power grids ready to support such an influx? Do we have sufficient advancements in power electronics technology to smoothly provide grid support using RES? The answer is NO. Currently, the system predominantly uses grid-following (GFL) converters, built on the assumption that inertial sources regulate the system stability. Such an assumption does not hold for low-inertia grids of the future. Grid-forming (GFM) converters, which mimic the traditional synchronous machinery’s functionalities, have been identified as a potential solution to support low-inertia grids. Performance analyses of GFM converters for small-signal instability can be found in the literature, but large-signal instability is also an open research question. View this paper
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18 pages, 437 KiB  
Article
Real-Time Locational Detection of Stealthy False Data Injection Attack in Smart Grid: Using Multivariate-Based Multi-Label Classification Approach
by Hanem I. Hegazy, Adly S. Tag Eldien, Mohsen M. Tantawy, Mostafa M. Fouda and Heba A. TagElDien
Energies 2022, 15(14), 5312; https://doi.org/10.3390/en15145312 - 21 Jul 2022
Cited by 19 | Viewed by 2692
Abstract
Recently, false data injection attacks (FDIAs) have been identified as a significant category of cyber-attacks targeting smart grids’ state estimation and monitoring systems. These cyber-attacks aim to mislead control system operations by compromising the readings of various smart grid meters. The real-time and [...] Read more.
Recently, false data injection attacks (FDIAs) have been identified as a significant category of cyber-attacks targeting smart grids’ state estimation and monitoring systems. These cyber-attacks aim to mislead control system operations by compromising the readings of various smart grid meters. The real-time and precise locational identification of FDIAs is crucial for smart grid security and reliability. This paper proposes a multivariate-based multi-label locational detection (MMLD) mechanism to detect the presence and locations of FDIAs in real-time measurements with precise locational detection accuracy. The proposed architecture is a parallel structure that concatenates Long Short-Term Memory (LSTM) with Temporal Convolutional Neural Network (TCN). The proposed architecture is trained using Keras with Tensorflow libraries, and its performance is verified using an IEEE standard bus system in the MATPOWER package. Extensive testing has shown that the proposed approach effectively improves the presence-detection accuracy for locating stealthy FDIAs in small and large systems under various attack conditions. In addition, this work provides a customized loss function for handling the class imbalance problem. Simulation results reveal that our MMLD technique has a modest advantage in some aspects. First, our mechanism outperforms benchmark models because the problem is formulated as a multivariate-based multi-label classification problem. Second, it needs fewer iterations for training and reaching the optimal model. More specifically, our approach is less complex and more scalable than benchmark algorithms. Full article
(This article belongs to the Special Issue Secure and Efficient Communication in Smart Grids)
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34 pages, 3469 KiB  
Article
Reliability Analysis of MV Electric Distribution Networks Including Distributed Generation and ICT Infrastructure
by Miroslaw Parol, Jacek Wasilewski, Tomasz Wojtowicz, Bartlomiej Arendarski and Przemyslaw Komarnicki
Energies 2022, 15(14), 5311; https://doi.org/10.3390/en15145311 - 21 Jul 2022
Cited by 10 | Viewed by 2651
Abstract
In recent years, the increased distributed generation (DG) capacity in electric distribution systems has been observed. Therefore, it is necessary to research existing structures of distribution networks as well as to develop new (future) system structures. There are many works on the reliability [...] Read more.
In recent years, the increased distributed generation (DG) capacity in electric distribution systems has been observed. Therefore, it is necessary to research existing structures of distribution networks as well as to develop new (future) system structures. There are many works on the reliability of distribution systems with installed DG sources. This paper deals with a reliability analysis for both present and future medium voltage (MV) electric distribution system structures. The impact of DG technology used and energy source location on the power supply reliability has been analyzed. The reliability models of electrical power devices, conventional and renewable energy sources as well as information and communications technology (ICT) components have been proposed. Main contribution of this paper are the results of performed calculations, which have been analyzed for specific system structures (two typical present network structures and two future network structures), using detailed information on DG types, their locations and power capacities, as well as distribution system automation applied (automatic stand-by switching on—ASS and automatic power restoration—APR). The reliability of the smart grid consisting of the distribution network and the coupled communications network was simulated and assessed. The observations and conclusions based on calculation results have been made. More detailed modeling and consideration of system automation of distribution grids with DG units coupled with the communication systems allows the design and application of more reliable MV network structures. Full article
(This article belongs to the Special Issue Intelligent Forecasting and Optimization in Electrical Power Systems)
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14 pages, 11688 KiB  
Article
The Sequence Stratigraphic Division and Depositional Environment of the Jurassic Yan’an Formation in the Pengyang Area, Southwestern Margin of the Ordos Basin, China
by Lianfu Hai, Caixia Mu, Qinghai Xu, Yongliang Sun, Hongrui Fan, Xiangyang Xie, Xiangcheng Wei, Chao Mei, Haibin Yu, Walter Manger and Jun Yang
Energies 2022, 15(14), 5310; https://doi.org/10.3390/en15145310 - 21 Jul 2022
Cited by 1 | Viewed by 1576
Abstract
Coal and organic-rich shale in the Yan’an Formation in the southwestern margin of the Ordos Basin are widely developed, which is an important fact for oil and gas exploration in China that has been widely explored for a long time. In this paper, [...] Read more.
Coal and organic-rich shale in the Yan’an Formation in the southwestern margin of the Ordos Basin are widely developed, which is an important fact for oil and gas exploration in China that has been widely explored for a long time. In this paper, detailed sequence division and sedimentary environment analyses of the Yan’an Formation in the Pengyang area on the southwestern margin of the Ordos Basin were conducted using field outcrops, drilling cores, logging, wavelet transform and organic geochemistry. The results showed that the succession consists of some units with distinctly different characteristics. Based on the petrographic assemblage and transform wavelet characteristics, the Yan’an Formation in this area can be divided into a long-term cycle, five medium-term cycles, and eleven short-term cycles, among which coal and carbonaceous shale were mainly developed in the short-term cycles I2, III1, III2, V1 and V2. Coal and organic-rich mud shale have been developed in the Yan’an Formation and plant debris in mudstone and coal is common, indicating the development of swamps and shallow water-covered depressions in this area. The sandstones showed parallel bedding, cross-bedding and scours, thus indicating fluvial deposits. The saturated hydrocarbon gas chromatographic parameters of mud shale showed that the pristane/phytane (Pr/Ph) ratio is 2.24–6.22, the Ph/nC18 ratio is 0.15–0.93, and the Pr/nC17 ratio is 0.97–2.78, supporting the finding that the organic matter has mainly originated from terrestrial sources. Full article
(This article belongs to the Special Issue Shale Oil and Gas Accumulation Mechanism)
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12 pages, 4076 KiB  
Article
The Influence of Movable Water on the Gas-Phase Threshold Pressure Gradient in Tight Gas Reservoirs
by Weiyao Zhu, Guodong Zou, Yuwei Liu, Wenchao Liu and Bin Pan
Energies 2022, 15(14), 5309; https://doi.org/10.3390/en15145309 - 21 Jul 2022
Cited by 8 | Viewed by 1703
Abstract
Threshold pressure gradient (TPG) is a key parameter determining the pore-scale fluid dynamics. In tight gas reservoirs, both gas and water exist in the porous rock, and the existing water can be divided into irreducible and movable water. However, how movable water saturation [...] Read more.
Threshold pressure gradient (TPG) is a key parameter determining the pore-scale fluid dynamics. In tight gas reservoirs, both gas and water exist in the porous rock, and the existing water can be divided into irreducible and movable water. However, how movable water saturation will influence TPG has not yet been investigated. Therefore herein, nuclear magnetic resonance (NMR) and high-pressure mercury intrusion (HPMI) experiments were performed to determine pore-scale water distribution, movable water saturation, and pore throat distribution in the core plugs. Subsequently, the air bubble method was used to measure TPG as a function of movable water saturation and permeability inside tight gas core plugs, finding that TPG increased from 0.01 MPa/m to 0.25 MPa/m with the movable saturation increased from 2% to 35%. Finally, a semi-empirical model was derived to describe the correlation between TPG, movable water saturation, and permeability, which performed better than previous models in the literature. These insights will advance the fundamental understanding of TPG in tight gas reservoirs and provide useful guidance on tight gas reservoirs development. Full article
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20 pages, 6575 KiB  
Article
An Approach for Pricing of Charging Service Fees in an Electric Vehicle Public Charging Station Based on Prospect Theory
by Yan Bao, Fangyu Chang, Jinkai Shi, Pengcheng Yin, Weige Zhang and David Wenzhong Gao
Energies 2022, 15(14), 5308; https://doi.org/10.3390/en15145308 - 21 Jul 2022
Cited by 9 | Viewed by 2044
Abstract
Within the context of sustainable development and a low-carbon economy, electric vehicles (EVs) are regarded as a promising alternative to engine vehicles. Since the increase of charging EVs brings new challenges to charging stations and distribution utility in terms of economy and reliability, [...] Read more.
Within the context of sustainable development and a low-carbon economy, electric vehicles (EVs) are regarded as a promising alternative to engine vehicles. Since the increase of charging EVs brings new challenges to charging stations and distribution utility in terms of economy and reliability, EV charging should be coordinated to form a friendly and proper load. This paper proposes a novel approach for pricing of charging service fees in a public charging station based on prospect theory. This behavioral economics-based pricing mechanism will guide EV users to coordinated charging spontaneously. By introducing prospect theory, a model that reflects the EV owner’s response to price is established first, considering the price factor and the state-of-charge (SOC) of batteries. Meanwhile, the quantitative relationship between the utility value and the charging price or SOC is analyzed in detail. The EV owner’s response mechanism is used in modeling the charging load after pricing optimization. Accordingly, by using the particle swarm optimization algorithm, pricing optimization is performed to achieve multiple objectives such as minimizing the peak-to-valley ratio and electricity costs of the charging station. Through case studies, the determined time-of-use charging prices by pricing optimization is validated to be effective in coordinating EV users’ behavior, and benefiting both the station operator and power systems. Full article
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21 pages, 13070 KiB  
Article
Distribution Strategy Optimization of Standalone Hybrid WT/PV System Based on Different Solar and Wind Resources for Rural Applications
by Yan Yang, Qingyu Wei, Shanke Liu and Liang Zhao
Energies 2022, 15(14), 5307; https://doi.org/10.3390/en15145307 - 21 Jul 2022
Cited by 9 | Viewed by 1643
Abstract
The characteristics of solar and wind energy determine that the optimization of a standalone hybrid wind turbine (WT)/photovoltaic panel (PV) system depends on the natural resources of the installation location. In order to ensure system reliability and improve the resource utilization, a method [...] Read more.
The characteristics of solar and wind energy determine that the optimization of a standalone hybrid wind turbine (WT)/photovoltaic panel (PV) system depends on the natural resources of the installation location. In order to ensure system reliability and improve the resource utilization, a method for determining the installed capacity ratio of a hybrid renewable energy system is required. This study proposes a calculation method to optimize the installed capacity ratio, considering the system reliability to meet the needs of the hybrid system to adapt to different natural resources. In this paper, a standalone hybrid WT/PV system to provide electricity for rural areas is designed. Taking the power supply guarantee rate and electricity supply continuity as indicators, the system is simulated by using the Transient System Simulator solver. The results show that the recommended installed capacity ratio of the WT and PV is 5:1 when the total solar irradiation is less than 5040 MJ/(m2·a) and the annual average wind velocity is in the range of 3.0~3.5 m/s. When the annual average wind velocity is in the range of 2.0~3.0 m/s, the PV plays an increasingly significant role in the hybrid system and exceeds the WT if the total solar irradiation is greater than 6300 MJ/(m2·a). However, if the total solar irradiation and the annual average wind velocity are less than 5040 MJ/(m2·a) and 2.0 m/s, respectively, it is not recommended to use the standalone hybrid system because it cannot meet the power demand. These conclusions provide guidance for the distribution strategies of the standalone hybrid WT/PV system within different natural resources. Full article
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20 pages, 17255 KiB  
Article
Sedimentary Architecture Analysis of Deltaic Sand Bodies Using Sequence Stratigraphy and Seismic Sedimentology: A Case Study of Jurassic Deposits in Zhetybay Oilfield, Mangeshrak Basin, Kazakhstan
by Jun Ni, Dingding Zhao, Xixuan Liao, Xuanran Li, Libing Fu, Ruxian Chen, Zhentong Xia and Yuming Liu
Energies 2022, 15(14), 5306; https://doi.org/10.3390/en15145306 - 21 Jul 2022
Cited by 6 | Viewed by 1957
Abstract
Three-dimensional (3D) seismic data and well log data were used to investigate the sandstone architecture of the Middle Jurassic deltaic reservoirs of the Zhetybay Oilfield, Mangeshrak Basin, Kazakhstan. The base-level cycles of different scales were identified and divided using well log and 3D [...] Read more.
Three-dimensional (3D) seismic data and well log data were used to investigate the sandstone architecture of the Middle Jurassic deltaic reservoirs of the Zhetybay Oilfield, Mangeshrak Basin, Kazakhstan. The base-level cycles of different scales were identified and divided using well log and 3D seismic data. Five types of sedimentary boundaries were identified in the mouth bar sandstones. The boundaries divide single mouth bars. Vertically, the spatial distribution of sand bodies can be divided into superposed, spliced, and isolation modes. Laterally, contact modes can be divided into superposition, lateral, and isolation modes. We found that the base-level cycle controls the evolution of the delta front sand body architecture. In the early decline or late rise of the base-level cycle, the superimposed or spliced modes dominate the sand body. By contrast, the lateral or isolation modes dominate the sand body in the late decline or early rise of the base-level cycle. This paper proposes an architecture model of the delta front sand bodies controlled by the base-level cycle. The spatial distribution and morphological variation of deltaic sand bodies could be linked to the base-level cycles. Full article
(This article belongs to the Special Issue Shale Oil and Gas Accumulation Mechanism)
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24 pages, 3715 KiB  
Article
A Method for the Evaluation of Power-Generating Sets Based on the Assessment of Power Quality Parameters
by Karol Jakub Listewnik
Energies 2022, 15(14), 5305; https://doi.org/10.3390/en15145305 - 21 Jul 2022
Viewed by 1728
Abstract
This article presents a new method for the classification of machine failures using an example of selected generating sets. Measurements and an analysis of the electrical parameters, such as the phase-to-phase voltages at the terminals of a synchronous generator, armature current, and voltage [...] Read more.
This article presents a new method for the classification of machine failures using an example of selected generating sets. Measurements and an analysis of the electrical parameters, such as the phase-to-phase voltages at the terminals of a synchronous generator, armature current, and voltage and excitation current of a synchronous generator, are the basis for determining the failure symptoms. The existing energy quality coefficients are adopted as symptoms for the assessment of failures in the monitored generating set. We assume in this method that the description of the input–output relationship is in the form of a black box and use the binary diagnostics matrix (BDM) to investigate the failure–symptom relationships between the inputs (intentional failures) and outputs (failures symptoms = fault-sensitive power quality (PQ) coefficients). The method presented in this article enables the detection and classification of both electrical damage in a synchronous generator and mechanical damage in a diesel engine. It is anticipated that further work and development of the method will focus on the implementation of the algorithm in the form of software into a miniature IoT module for the automatic classification of failures. Full article
(This article belongs to the Section F: Electrical Engineering)
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18 pages, 2922 KiB  
Article
An Empirical Energy Demand Flexibility Metric for Residential Properties
by Jenny Crawley, Despina Manouseli, Peter Mallaburn and Cliff Elwell
Energies 2022, 15(14), 5304; https://doi.org/10.3390/en15145304 - 21 Jul 2022
Cited by 6 | Viewed by 2572
Abstract
Shifting from heating using fossil fuel combustion to electrified heating, dominated by heat pumps, is central to many countries’ decarbonisation strategy. The consequent increase in electricity demand, combined with that from electric vehicles, and the shift from non-renewable to renewable generation requires increased [...] Read more.
Shifting from heating using fossil fuel combustion to electrified heating, dominated by heat pumps, is central to many countries’ decarbonisation strategy. The consequent increase in electricity demand, combined with that from electric vehicles, and the shift from non-renewable to renewable generation requires increased demand flexibility to support system operation. Demand side response through interrupting heating during peak demands has been widely proposed and simulation modelling has been used to determine the technical potential. This paper proposes an empirical approach to quantifying a building’s potential to operate flexibly, presenting a metric based on measured temperature drop in a dwelling under standard conditions after heating is switched off, using smart meter and internal temperature data. A result was derived for 96% of 193 homes within a test dataset, mean temperature drop of 1.5 °C in 3 h at 15 °C inside-outside temperature differential. An empirical flexibility metric may support decision making and decarbonisation. For households it may support the transition to heat pumps, enabling time of use costs and tariffs to be better understood and system to be specified by installers. Electricity system stakeholders, such as aggregators and DNOs may use it to identify the potential for demand response, managing local networks, infrastructure and aggregation. Full article
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12 pages, 2451 KiB  
Article
Modern Methods of Strengthening and Sealing Salt Mines
by Andrzej Gonet, Stanisław Stryczek and Marcin Kremieniewski
Energies 2022, 15(14), 5303; https://doi.org/10.3390/en15145303 - 21 Jul 2022
Cited by 4 | Viewed by 1807
Abstract
In order to ensure safe working conditions for miners underground, many works are carried out in mines to strengthen and seal mining excavations. This article presents the successfully applied technology for removing water inflow from the unique Salt Mine. Failure to take such [...] Read more.
In order to ensure safe working conditions for miners underground, many works are carried out in mines to strengthen and seal mining excavations. This article presents the successfully applied technology for removing water inflow from the unique Salt Mine. Failure to take such action may ultimately lead to the flooding of the “Wieliczka” Salt Mine (KSW). On the basis of the authors’ research studies, some of the implemented works at the “Wieliczka” Salt Mine are presented, the purpose of which is to better protect the mine against the risk of flooding with water. Thanks to this, the mine can safely survive for many more years. This article presents two innovative technologies in salt mines: (1) sealing of the rock mass surrounding the Kościuszko shaft casing in the “Wieliczka” Salt Mine, where jet injection was used as the basic method of making an anti-filter screen outside the shaft casing and classic injection as a supplementary method for sealing the anthropogenic embankment; (2) reconstruction of the internal pillar of safety by implementing a patented technology called “pipeline injection” on the example of the Mina cross-section, in which a catastrophic water inflow was previously created that threatened the existence of the “Wieliczka” Salt Mine. The first method consists of making an anti-filter screen, which is located outside the shaft housing. Unfortunately, it is not possible to perform injection works from inside the shaft housing, because the Kosciuszko shaft, as a ventilation shaft, must be open constantly. To solve this problem, it is designed as the main technology known as jet grouting, which is supplemented by pressure injection at a depth of up to several meters with continuous monitoring of the condition of the casing during injection works. The second example concerns the reconstruction of the internal pillar of mine safety in the area of the northern border of the salt deposit. In this case, the catastrophic hazard is documented, as evidenced by the inflow to the Mina transverse, which is located on the fourth level of the mine. This task was successfully completed by the implementation of a patented technological solution called pipeline injection, the details of which are discussed in this article. Full article
(This article belongs to the Special Issue Latest Technologies and Tools in Drilling Systems)
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4 pages, 157 KiB  
Editorial
Cogeneration Economics
by Eugenia Giannini
Energies 2022, 15(14), 5302; https://doi.org/10.3390/en15145302 - 21 Jul 2022
Viewed by 1069
Abstract
This editorial provides a synopsis of the contributions published during 2020–2021 in a Special Issue of Energies entitled “Cogeneration Economics” [...] Full article
(This article belongs to the Special Issue Cogeneration Economics)
2 pages, 180 KiB  
Editorial
Power Electronic Circuits for Electric Drives and Renewable Energy Sources
by Jelena Loncarski, Cecilia Boström and Riccardo Mandrioli
Energies 2022, 15(14), 5301; https://doi.org/10.3390/en15145301 - 21 Jul 2022
Viewed by 1379
Abstract
This Special Issue was intended to consolidate the most recent advances in the field of power electronics for renewable energy sources and electric drives [...] Full article
24 pages, 3950 KiB  
Article
Control of Heat Transfer in a Vertical Ground Heat Exchanger for a Geothermal Heat Pump System
by Khaled Salhein, C. J. Kobus and Mohamed Zohdy
Energies 2022, 15(14), 5300; https://doi.org/10.3390/en15145300 - 21 Jul 2022
Cited by 5 | Viewed by 4204
Abstract
This paper presents a mathematical model of heat transfer behavior between the liquid inside vertical underground geothermal pipes and the surrounding ground for heating (in the winter) and cooling (in the summer) modes in a ground heat exchanger (GHE) that can optimize its [...] Read more.
This paper presents a mathematical model of heat transfer behavior between the liquid inside vertical underground geothermal pipes and the surrounding ground for heating (in the winter) and cooling (in the summer) modes in a ground heat exchanger (GHE) that can optimize its output temperature. The GHE’s output temperature reaches the appropriate value when the water velocity is lowered enough. Subsequently, the proposed model was applied to a case study of a 400-ton geothermal heat pump system (GHPS) at Oakland University, in both the heating and cooling modes, to assess its validity and improve the GHE’s performance. The model was implemented in MATLAB using an ordinary differential equation (ODE) solver. Four different water velocities were used to demonstrate the significant effect of velocity on the loop exit temperature. Model predictive control (MPC) was designed to optimize the GHE’s output temperature by controlling the water velocity, which could reduce the energy consumption used for heat and water circulating pumps. The results reveal that the acceptable range of the water velocity for Oakland University’s GHE was between 0.35 and 0.45 m/s, which ensured that the heat pump system delivered the proper temperature to provide the Human Health Building (HHB) with a comfortable temperature regardless of the season. The suggested water velocity ranges in vertical single U-tube pipes with diameters of De 25 mm, De 32 mm, and De 40 mm are between 0.33 and 0.43 m/s, 0.35 to 0.45 m/s, and 0.38 to 0.48 m/s, respectively. Full article
(This article belongs to the Topic Geothermal Energy Technology and Current Status)
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17 pages, 3902 KiB  
Article
Short-Term Load Forecasting with a Novel Wavelet-Based Ensemble Method
by V. Y. Kondaiah and B. Saravanan
Energies 2022, 15(14), 5299; https://doi.org/10.3390/en15145299 - 21 Jul 2022
Cited by 6 | Viewed by 1699
Abstract
“Short-term load forecasting (STLF)” is increasingly significant because of the extensive use of distributed energy resources, the incorporation of intermitted RES, and the implementation of DSM. This paper provides a novel ensemble forecasting model with wavelet transform for the STLF depending on the [...] Read more.
“Short-term load forecasting (STLF)” is increasingly significant because of the extensive use of distributed energy resources, the incorporation of intermitted RES, and the implementation of DSM. This paper provides a novel ensemble forecasting model with wavelet transform for the STLF depending on the decomposition principle of load profiles. The model can effectively capture the portion of daily load profiles caused by seasonal variations. The results indicate that it is possible to improve STLF accuracy with the proposed method. The proposed approach is tested with the data taken from Ontario’s electricity market in Canada. The results show that the proposed technique performs well in-terms of prediction when compared to existing traditional and cutting-edge methods. The performance of the model was validated with different datasets. Moreover, this approach can provide accurate load forecasting using ensemble models. Therefore, utilities and smart grid operators can use this approach as an additional decision-making tool to improve their real-time decisions. Full article
(This article belongs to the Special Issue Control and Optimization of Electrical Power and Energy Systems)
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13 pages, 3131 KiB  
Article
A Comparative Analysis on the Variability of Temperature Thresholds through Time for Wind Turbine Generators Using Normal Behaviour Modelling
by Alan Turnbull, James Carroll and Alasdair McDonald
Energies 2022, 15(14), 5298; https://doi.org/10.3390/en15145298 - 21 Jul 2022
Cited by 5 | Viewed by 1498
Abstract
Data-driven normal behaviour models have gained traction over the last few years as a convenient way of modelling turbine operational health to detect anomalies. By leveraging high-dimensional operational relationships, temperature thresholds can be automatically calculated based on each individual turbine unique operating envelope, [...] Read more.
Data-driven normal behaviour models have gained traction over the last few years as a convenient way of modelling turbine operational health to detect anomalies. By leveraging high-dimensional operational relationships, temperature thresholds can be automatically calculated based on each individual turbine unique operating envelope, in theory minimising false alarms and providing more reliable diagnostics. The aim of this work is to provide further insight into practical uses and limitations of implementing normal behaviour temperature models in practice, to inform practitioners, as well as assist in improving wind turbine generator fault detection systems. Results suggest that, on average, as little as two months of data are adequate to produce stable temperature alarm thresholds, with the worst case example requiring approximately 200–290 days of data depending on the component and desired convergence criteria. Full article
(This article belongs to the Special Issue Intelligent Condition Monitoring of Wind Power Systems)
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15 pages, 1839 KiB  
Article
Solar Farms as the Only Power Source for the Entire Country
by Anna Manowska and Andrzej Nowrot
Energies 2022, 15(14), 5297; https://doi.org/10.3390/en15145297 - 21 Jul 2022
Cited by 2 | Viewed by 2392
Abstract
The presented paper shows a hypothetical large solar farm that would be the only source of electricity for the entire country. The energy crisis in Europe raises the question of whether it is possible to supply an electrical system based only on renewable [...] Read more.
The presented paper shows a hypothetical large solar farm that would be the only source of electricity for the entire country. The energy crisis in Europe raises the question of whether it is possible to supply an electrical system based only on renewable energy sources. What should the surface area of the solar panels be in a hypothetical large solar farm to power the entire country? In this work, we will show what requirements must be met to make this feasible. Very important differences between the installed power capacity in a coal-fired or nuclear power plant and a solar power plant are discussed. The article presents calculations of the surface area of photovoltaic panels in that solar farm for four exemplary countries in Central Europe: Poland, Germany, the Czech Republic and the Slovak Republic. These studies are particularly important for Poland, whose electrical system is still mainly based on coal-fired power plants. The hypothetical solar farm could, in practice, take the form of dozens of solar power plants located in different parts of the country. Most importantly, the proposed solution will counteract climate change. Full article
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16 pages, 21071 KiB  
Article
Modeling, Optimization, and Analysis of a Virtual Power Plant Demand Response Mechanism for the Internal Electricity Market Considering the Uncertainty of Renewable Energy Sources
by Zahid Ullah, Arshad and Hany Hassanin
Energies 2022, 15(14), 5296; https://doi.org/10.3390/en15145296 - 21 Jul 2022
Cited by 24 | Viewed by 2576
Abstract
The penetration of renewable energy sources (RESs) in the electrical power system has increased significantly over the past years due to increasing global concern about climate change. However, integrating RESs into the power market is highly problematic. The output of RESs such as [...] Read more.
The penetration of renewable energy sources (RESs) in the electrical power system has increased significantly over the past years due to increasing global concern about climate change. However, integrating RESs into the power market is highly problematic. The output of RESs such as wind turbines (WTs) and photovoltaics (PVs) is highly uncertain. Their correlation with load demand is not always guaranteed, which compromises system reliability. Distributed energy resources (DERs), especially demand response (DR) programs and energy storage systems (ESSs), are possible options to overcome these operational challenges under the virtual power plant (VPP) setting. This study investigates the impact of using a DR program and battery energy storage system (BESS) on the VPP’s internal electricity market, and also cost-minimization analysis from a utility viewpoint. Three different constrained optimal power flow (OPF) problems are solved such as base case, DR case, and BESS case to determine total incurred costs, locational marginal prices (LMPs), and generator commitments. A scenario tree approach is used to model the uncertainties associated with WTs, PVs, and load demand. The proposed model is investigated on a 14-bus distribution system. The simulation results obtained demonstrate a favorable impact of DR and a BESS on renewable operational challenges. Full article
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20 pages, 12103 KiB  
Article
Dynamic Characteristics and Demonstration of an Integrated Linear Engine Generator with Alternative Electrical Machines
by Ramin Moeini Korbekandi, Nick J. Baker, Mehmet C. Kulan, Aslan S. Jalal, Dawei Wu and Mingqiang Li
Energies 2022, 15(14), 5295; https://doi.org/10.3390/en15145295 - 21 Jul 2022
Cited by 6 | Viewed by 1629
Abstract
A linear engine generator with a compact double-acting free piston mechanism allows for full integration of the combustion engine and generator, which provides an alternative chemical-to-electrical energy converter with a higher volumetric power density for the electrification of automobiles, trains, and ships. This [...] Read more.
A linear engine generator with a compact double-acting free piston mechanism allows for full integration of the combustion engine and generator, which provides an alternative chemical-to-electrical energy converter with a higher volumetric power density for the electrification of automobiles, trains, and ships. This paper aims to analyse the performance of the integrated engine with alternative permanent magnet linear tubular electrical machine topologies using a coupled dynamic model in Siemens Simcenter software. Two types of alternative generator configurations are compared, namely long translator-short stator and short translator-long stator linear machines. The dynamic models of the linear engine and linear generator, validated with lab-scale prototypes, are applied to investigate the influence of alternative topologies of the generator on system performance. The coupled model will facilitate the early design phase and reveal the optimal match of the key parameters of the engine and generator. Then, experimental tests on an integrated compressor cylinder-generator prototype were successfully performed, and it is shown that this concept is feasible and electrical power and compressed working fluid, such as air, can be generated by this prototype. Full article
(This article belongs to the Section F: Electrical Engineering)
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15 pages, 3506 KiB  
Article
Study of the Pipeline in Emergency Operation and Assessing the Magnitude of the Gas Leak
by Andrey Schipachev, Vadim Fetisov, Ayrat Nazyrov, Lee Donghee and Abdurakhmat Khamrakulov
Energies 2022, 15(14), 5294; https://doi.org/10.3390/en15145294 - 21 Jul 2022
Cited by 12 | Viewed by 2360
Abstract
Accidents on gas pipelines cause significant damage to the national economy and the economy of the state. Thus, it is necessary to always be prepared for such situations in order to restore the normal operation of the gas pipeline as soon as possible. [...] Read more.
Accidents on gas pipelines cause significant damage to the national economy and the economy of the state. Thus, it is necessary to always be prepared for such situations in order to restore the normal operation of the gas pipeline as soon as possible. An important role is played by the execution time of the control actions to localize the accident, pump out the gas, and change the operating modes. It is essential that such control be undertaken, especially if such a situation occurs near a gas-measuring installation for measuring the amount of vented gas. Therefore, the control actions must be error-free in order to quickly stop the non-stationary process, which can lead to undesirable consequences. The paper presents a mathematical model of the operation of the pipeline, developed for the management of the pipeline in an emergency. The analysis of the problem of the occurrence of accidents was carried out, and the effect of liquid on its walls was modeled when the operating mode of the pipeline changed. An example is presented using a numerical model carried out in ANSYS, as well as being analyzed analytically. The results of the calculations are presented, and special attention is paid to the parameters influencing the change in the operating mode of the pipeline. Full article
(This article belongs to the Special Issue Geotechnologies and Structures in the Energy Sector)
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18 pages, 6432 KiB  
Article
Laser Profilometry on Micro-PTC
by Gianluca Marotta, Daniela Fontani, Franco Francini, David Jafrancesco, Maurizio De Lucia and Paola Sansoni
Energies 2022, 15(14), 5293; https://doi.org/10.3390/en15145293 - 21 Jul 2022
Viewed by 1502
Abstract
Profilometry is useful in detecting surface faults on solar concentrators, which can be imperfectly manufactured, thus affecting system performance. Profilometric analyses are performed on a micro-parabolic trough collector (m-PTC), with reduced sizes and greater mirror curvature than a usual PTC. The peculiar dimensions [...] Read more.
Profilometry is useful in detecting surface faults on solar concentrators, which can be imperfectly manufactured, thus affecting system performance. Profilometric analyses are performed on a micro-parabolic trough collector (m-PTC), with reduced sizes and greater mirror curvature than a usual PTC. The peculiar dimensions and shape of this micro-PTC request to develop a specific configuration of laser profilometry. It includes a laser diode with a converging lens placed in front of it, ensuring that the mirror curvature does not affect the beam reflection. A new method to calculate the spot position furnishes the reflected beam center even if it lies outside the target, giving it a virtual expansion. The profile is assessed with an iterative calculation, starting from a first point, physically measured. The results are the 3D profile reconstruction of the parabolic mirror and a map of the slope error for each mirror point. It also estimates the intercept factor, a parameter fundamental to optimize the m-PTC system, whose value is in agreement with a structured light measurement on the same object. This intercept factor was obtained averaging the local intercept factor calculated for each mirror point, which individuates the mirror portions not focusing the sunrays on the tube. Full article
(This article belongs to the Special Issue Solar Energy Storage: Materials, Devices, Designs and Systems Level)
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15 pages, 5656 KiB  
Article
Ce:Nd:YAG Solar Laser with 4.5% Solar-to-Laser Conversion Efficiency
by Dário Garcia, Dawei Liang, Cláudia R. Vistas, Hugo Costa, Miguel Catela, Bruno D. Tibúrcio and Joana Almeida
Energies 2022, 15(14), 5292; https://doi.org/10.3390/en15145292 - 21 Jul 2022
Cited by 27 | Viewed by 2209
Abstract
The efficiency potential of a small-size solar-pumped laser is studied here. The solar laser head was composed of a fused silica aspheric lens and a conical pump cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic [...] Read more.
The efficiency potential of a small-size solar-pumped laser is studied here. The solar laser head was composed of a fused silica aspheric lens and a conical pump cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic mirror with an effective collection area of 0.293 m2 to end-side pump a Ce (0.1 at%):Nd (1.1 at%):YAG rod of 2.5 mm diameter and 25 mm length. Optimum solar laser design parameters were found through Zemax© non-sequential ray-tracing and LASCAD™ analysis. The utilization of the Ce:Nd:YAG medium with small diameter pumped by a small-scale solar concentrator was essential to significantly enhance the end-side pump solar laser efficiency and thermal performance. For 249 W incoming solar power at an irradiance of 850 W/m2, 11.2 W multimode solar laser power was measured, corresponding to the record solar-to-laser power conversion efficiency of 4.50%, being, to the best of our knowledge, 1.22 times higher than the previous record. Moreover, the highest solar laser collection efficiency of 38.22 W/m2 and slope efficiency of 6.8% were obtained, which are 1.18 and 1.02 times, respectively, higher than the previous records. The lowest threshold solar power of a Ce:Nd:YAG solar-pumped laser is also reported here. Full article
(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)
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22 pages, 6053 KiB  
Article
Hybrid Game Optimization of Microgrid Cluster (MC) Based on Service Provider (SP) and Tiered Carbon Price
by Fei Feng, Xin Du, Qiang Si and Hao Cai
Energies 2022, 15(14), 5291; https://doi.org/10.3390/en15145291 - 21 Jul 2022
Cited by 5 | Viewed by 1173
Abstract
Carbon trading is a market-based mechanism towards low-carbon electric power systems. A hy-brid game optimization model is established for deriving the optimal trading price between mi-crogrids (MGs) as well as providing the optimal pricing scheme for trading between the microgrid cluster(MC) and the [...] Read more.
Carbon trading is a market-based mechanism towards low-carbon electric power systems. A hy-brid game optimization model is established for deriving the optimal trading price between mi-crogrids (MGs) as well as providing the optimal pricing scheme for trading between the microgrid cluster(MC) and the upper-layer service provider (SP). At first, we propose a robust optimization model of microgrid clusters from the perspective of risk aversion, in which the uncertainty of wind and photovoltaic (PV) output is modeled with resort to the information gap decision theo-ry(IGDT). Finally, based on the Nash bargaining theory, the electric power transaction payment model between MGs is established, and the alternating direction multiplier method (ADMM) is used to solve it, thus effectively protecting the privacy of each subject. It shows that the proposed strategy is able to quantify the uncertainty of wind and PV factors on dispatching operations. At the same time, carbon emission could be effectively reduced by following the tiered carbon price scheme. Full article
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21 pages, 2868 KiB  
Article
Profit Maximization with Imbalance Cost Improvement by Solar PV-Battery Hybrid System in Deregulated Power Market
by Ganesh Sampatrao Patil, Anwar Mulla, Subhojit Dawn and Taha Selim Ustun
Energies 2022, 15(14), 5290; https://doi.org/10.3390/en15145290 - 21 Jul 2022
Cited by 16 | Viewed by 1827
Abstract
The changeable nature of renewable sources creates difficulties in system security and stability. Therefore, it is necessary to study system risk in several power system scenarios. In a wind-integrated deregulated power network, the wind farm needs to submit the bid for its power-generating [...] Read more.
The changeable nature of renewable sources creates difficulties in system security and stability. Therefore, it is necessary to study system risk in several power system scenarios. In a wind-integrated deregulated power network, the wind farm needs to submit the bid for its power-generating quantities a minimum of one day ahead of the operation. The wind farm submits the data based on the expected wind speed (EWS). If any mismatch occurs between real wind speed (RWS) and expected wind speed, ISO enforces the penalty/rewards to the wind farm. In a single word, this is called the power market imbalance cost, which directly distresses the system profit. Here, solar PV and battery energy storage systems are used along by the wind farm to exploit system profit by grasping the negative outcome of imbalance cost. Along with system profit, the focus has also been on system risk. The system risk has been calculated using the risk assessment factors, i.e., Value-at-Risk (VaR) and Cumulative Value-at-risk (CVaR). The work is performed on a modified IEEE 14 and modified IEEE 30 bus test system. The solar PV-battery storage system can supply the demand locally first, and then the remaining power is given to the electrical grid. By using this concept, the system risk can be minimized by the incorporation of solar PV and battery storage systems, which have been studied in this work. A comparative study has been performed using three dissimilar optimization methods, i.e., Artificial Gorilla Troops Optimizer Algorithm (AGTO), Artificial Bee Colony Algorithm (ABC), and Sequential Quadratic Programming (SQP) to examine the consequence of the presented technique. The AGTO has been used for the first time in the risk assessment and alleviation problem, which is the distinctiveness of this work. Full article
(This article belongs to the Special Issue Power System Dynamics and Renewable Energy Integration)
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16 pages, 3416 KiB  
Article
Closed-Loop Combustion Optimization Based on Dynamic and Adaptive Models with Application to a Coal-Fired Boiler
by Chuanpeng Zhu, Pu Huang and Yiguo Li
Energies 2022, 15(14), 5289; https://doi.org/10.3390/en15145289 - 21 Jul 2022
Cited by 1 | Viewed by 1942
Abstract
To increase combustion efficiency and reduce pollutant emissions, this study presents an online closed-loop optimization method and its application in a boiler combustion system. To begin with, three adaptive dynamic models are established to predict NOx emission, the carbon content of fly ash [...] Read more.
To increase combustion efficiency and reduce pollutant emissions, this study presents an online closed-loop optimization method and its application in a boiler combustion system. To begin with, three adaptive dynamic models are established to predict NOx emission, the carbon content of fly ash (Cfh), and exhaust gas temperature (Teg), respectively. In these models, the orders of the input variables are considered to enable them to reflect the dynamics of the combustion system under load changes. Meanwhile, an adaptive least squares support vector machine (ALSSVM) algorithm is adopted to cope with the nonlinearity and the time-varying characteristics of the combustion system. Subsequently, based on the established models, an economic model predictive control (EMPC) problem is formulated and solved by a sequential quadratic programming (SQP) algorithm to calculate the optimal control variables satisfying the constraints on the control and control moves. The closed-loop optimization system is applied on a 600 MW boiler, and the performance analysis is conducted based on the operation data. The results show that the system can effectively increase boiler efficiency by about 0.5%. Full article
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21 pages, 2655 KiB  
Article
An Output Feedback Discrete-Time Controller for the DC-DC Buck Converter
by Martin A. Alarcón-Carbajal, José E. Carvajal-Rubio, Juan D. Sánchez-Torres, David E. Castro-Palazuelos and Guillermo J. Rubio-Astorga
Energies 2022, 15(14), 5288; https://doi.org/10.3390/en15145288 - 21 Jul 2022
Cited by 4 | Viewed by 2455
Abstract
This paper presents a discrete-time output feedback controller to regulate the output voltage of a DC-DC buck converter. The proposal’s main feature is the application of a discrete-time equivalent of the robust exact filtering differentiator. First, the document exposes a theoretical analysis of [...] Read more.
This paper presents a discrete-time output feedback controller to regulate the output voltage of a DC-DC buck converter. The proposal’s main feature is the application of a discrete-time equivalent of the robust exact filtering differentiator. First, the document exposes a theoretical analysis of the closed-loop system, where it is considered the problem of implementing a real-time differentiator with a good relationship between exactness and noise filtration performance. Hence, secondly, the controller in a laboratory setup is presented. The first experimental results suggest that the proposed controller exhibits good robustness against noise and maintains the asymptotic accuracy, even with saturated control inputs, as in the case of the DC-DC buck converter. Consequently, aiming to verify the features of the proposed method, the controller is validated through multiple experiments, showing satisfactory voltage tracking accuracy, good suppression of instantaneous load and supply voltage disturbances, and robustness against bounded measurement noise. Full article
(This article belongs to the Section F3: Power Electronics)
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15 pages, 6460 KiB  
Article
Energy Efficiency of Small Wind Turbines in an Urbanized Area—Case Studies
by Adam Zagubień and Katarzyna Wolniewicz
Energies 2022, 15(14), 5287; https://doi.org/10.3390/en15145287 - 21 Jul 2022
Cited by 7 | Viewed by 2012
Abstract
This study aimed to determine whether the wind zone that characterizes a given area of the country in open area is reflected in the built-up area lying within the zone. Analysis included four Polish cities located in different wind zones. The two-parameter Weibull [...] Read more.
This study aimed to determine whether the wind zone that characterizes a given area of the country in open area is reflected in the built-up area lying within the zone. Analysis included four Polish cities located in different wind zones. The two-parameter Weibull density distribution function was used to present the wind conditions at each location. Two 3 kW VAWT devices were selected to evaluate the productivity of wind turbines at the locations analyzed. It was shown that the wind zones characterizing the wind potential of a region in an open area have no significant influence on the wind conditions in the built-up area located in that area. It was determined that the study location’s did not exhibit wind potential that could be economically justified by a wind turbine. WTs in the city do not reach their nominal productivity. A decisive advantage of very light winds was observed (up to 2 m/s) and a large proportion of so-called atmospheric calms. It was shown that the installation of small wind turbines in an urbanized area requires a minimum of annual wind measurements at the exact location and height of each future turbine planned. Full article
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12 pages, 2684 KiB  
Article
Natural Gas Sweetening Using an Energy-Efficient, State-of-the-Art, Solid–Vapor Separation Process
by Hani Ababneh, Ahmed AlNouss, Iftekhar A. Karimi and Shaheen A. Al-Muhtaseb
Energies 2022, 15(14), 5286; https://doi.org/10.3390/en15145286 - 21 Jul 2022
Cited by 8 | Viewed by 2948
Abstract
With the anticipated rise in global demand for natural gas (NG) and liquefied natural gas (LNG), sour gas reserves are attracting the attention of the gas industry as a potential resource. However, to monetize these reserves, sour natural gas has to be sweetened [...] Read more.
With the anticipated rise in global demand for natural gas (NG) and liquefied natural gas (LNG), sour gas reserves are attracting the attention of the gas industry as a potential resource. However, to monetize these reserves, sour natural gas has to be sweetened by removing acid gases (carbon dioxide and/or hydrogen sulfide) before liquefaction. The solidification of these acid gases could be the basis for their separation from natural gas. In this study, a state-of-the art solid-vapor (SV) separation unit is developed for removal of acid gases from methane and simulated using a customized Aspen Plus operation unit. The operating principles and conditions, mathematical model, and performance results are presented for the SV unit. Further performance analyses, means of optimization and comparisons to conventional methods used by the industry were studied. Results showed that for similar sweet gas purity, the developed SV unit consumes only 27% of the energy required by the amine sweetening unit. Furthermore, it saves on capital costs, as it requires less equipment and does not suffer from high levels of corrosion. Full article
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22 pages, 12116 KiB  
Review
Review of Selected Advances in Electrical Capacitance Volume Tomography for Multiphase Flow Monitoring
by Rafiul K. Rasel, Shah M. Chowdhury, Qussai M. Marashdeh and Fernando L. Teixeira
Energies 2022, 15(14), 5285; https://doi.org/10.3390/en15145285 - 21 Jul 2022
Cited by 17 | Viewed by 2437
Abstract
Electrical Capacitance Volume Tomography (ECVT) has emerged as an attractive technology for addressing instrumentation requirements in various energy-related multiphase flow systems. ECVT can monitor multiple flow conditions and reconstruct real-time 3D images from capacitance measurements using a large set of electrode plates placed [...] Read more.
Electrical Capacitance Volume Tomography (ECVT) has emerged as an attractive technology for addressing instrumentation requirements in various energy-related multiphase flow systems. ECVT can monitor multiple flow conditions and reconstruct real-time 3D images from capacitance measurements using a large set of electrode plates placed around the processes column enclosing the sensed flow system. ECVT is non-intrusive and allows the measurement of changes in mutual capacitance between all possible plate pair combinations. The objective of this paper is to provide a comprehensive review of recent advances in ECVT, enabling robust monitoring of multiphase flows, especially water-containing multiphase flows. Full article
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16 pages, 1705 KiB  
Article
Investigation of the Effects of Torrefaction Temperature and Residence Time on the Fuel Quality of Corncobs in a Fixed-Bed Reactor
by Joseph I. Orisaleye, Simeon O. Jekayinfa, Ralf Pecenka, Adebayo A. Ogundare, Michael O. Akinseloyin and Opeyemi L. Fadipe
Energies 2022, 15(14), 5284; https://doi.org/10.3390/en15145284 - 21 Jul 2022
Cited by 12 | Viewed by 2568
Abstract
Biomass from agriculture is a promising alternative fuel due to its carbon-neutral feature. However, raw biomass does not have properties required for its direct utilization for energy generation. Torrefaction is considered as a pretreatment method to improve the properties of biomass for energy [...] Read more.
Biomass from agriculture is a promising alternative fuel due to its carbon-neutral feature. However, raw biomass does not have properties required for its direct utilization for energy generation. Torrefaction is considered as a pretreatment method to improve the properties of biomass for energy applications. This study was aimed at investigating the effects of torrefaction temperature and residence time on some physical and chemical properties of torrefied corncobs. Therefore, a fixed-bed torrefaction reactor was developed and used in the torrefaction of corncobs. The torrefaction process parameters investigated were the torrefaction temperature (200, 240, and 280 °C) and the residence time (30, 60, and 90 min). The effects of these parameters on the mass loss, grindability, chemical composition, and calorific value of biomass were investigated. It was shown that the mass loss increased with increasing torrefaction temperature and residence time. The grinding throughput of the biomass was improved by increasing both the torrefaction temperature and the residence time. Torrefaction at higher temperatures and longer residence times had greater effects on the reduction in particle size of the milled corncobs. The calorific value was highest at a torrefaction temperature of 280 °C and a residence time of 90 min. The energy yield for all treatments ranged between 92.8 and 99.2%. The results obtained in this study could be useful in the operation and design of torrefaction reactors. They also provided insight into parameters to be investigated for optimization of the torrefaction reactor. Full article
(This article belongs to the Special Issue Energy Systems Design in Agriculture)
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17 pages, 36695 KiB  
Article
Influence of Nanoemulsion Droplet Size of Removing Water Blocking Damage in Tight Gas Reservoir
by Yuan Li, Fujian Zhou, Jie Wang, Bojun Li, Hang Xu, Erdong Yao and Longhao Zhao
Energies 2022, 15(14), 5283; https://doi.org/10.3390/en15145283 - 21 Jul 2022
Cited by 7 | Viewed by 1883
Abstract
During the production process, water phase incursion into the reservoir causes water blocking damage and seriously affects the production of tight gas reservoirs. Recently, nanoemulsions have been used as highly effective water blocking removing agents in the field, but their mechanism is still [...] Read more.
During the production process, water phase incursion into the reservoir causes water blocking damage and seriously affects the production of tight gas reservoirs. Recently, nanoemulsions have been used as highly effective water blocking removing agents in the field, but their mechanism is still unclear. In this research, a series of nanoemulsions with different droplet sizes were synthesized, and their water blocking removing performance was intensively investigated. To begin, the relationship between the droplet size and the chemical composition of the nanoemulsion was determined by dynamic light scattering. Second, the influence of the nanoemulsion droplet size on the surface tension and the contact angle experiments was studied. Finally, NMR and permeability recovery experiments were used to study the relationship between the droplet size and the water locking removing effect of the nanoemulsions. Simultaneously, the surfactant release process was investigated using the static adsorption curves of the nanoemulsions. The experimental results show that the droplet size of nanoemulsion has an exponential relationship with the oil phase content. The surface tension decreases with the increase in droplet size, but the wetting reversal effect decreases with the increase in droplet size. The nanoemulsion with an oil phase content of 5 wt.% has the best water locking removing effect, and the permeability recovery value of the core reaches 59.54%. The adsorption control of the nanoemulsion on the surfactant is the key to its water blocking removing ability. This comprehensive study shows that the nanoemulsion with an oil phase content of 5 wt.% has optimum adsorption control capability. Thus, it can be used as a promising candidate for removing water blocking in tight gas reservoirs. Full article
(This article belongs to the Special Issue Shale Oil and Gas Accumulation Mechanism)
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