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Energies, Volume 15, Issue 10 (May-2 2022) – 375 articles

Cover Story (view full-size image): Distributed generation of multiple energy vectors is gaining significant ground in the ongoing transition toward a decarbonized energy mixture. Dynamic simulation of such energy systems is a key driver for performance enhancement and optimization of the profitability gained. In this paper, a trigeneration system in a student residence complex, located in Greece, powered by solar thermal energy, biomass, and photovoltaics, is studied. The representation of the system is implemented through validated dynamic models developed in the Modelica language. The potential benefits of additional measures applied in the system are evaluated in terms of renewables’ contribution, biomass fuel consumption, and temporal flexibility. View this paper
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Article
Reduction of Starting Current in Large Induction Motors
Energies 2022, 15(10), 3848; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103848 - 23 May 2022
Viewed by 407
Abstract
Large induction motors can have a high inrush and run-up current during starting, often up to ten times the rated current. In weak supplies, this could be a problem, causing system stability issues and the voltage to dip below acceptable levels. In islanded [...] Read more.
Large induction motors can have a high inrush and run-up current during starting, often up to ten times the rated current. In weak supplies, this could be a problem, causing system stability issues and the voltage to dip below acceptable levels. In islanded systems, the capacity could be pulled below its maximum. There are several different starting methods possible, but they are often only suitable for smaller machines. One method not investigated is the use of parallel capacitor compensation during the starting because large induction motors are very inductive during the starting sequence, so that supplying reactive power may be more effective than supplying energy. This paper first investigates several different induction motors with increasing size and assesses their compensation requirements in terms of the reactive power requirement during starting. It is shown that they do generally become more inductive as they increase in size. It is illustrated, using simulations, that using parallel capacitors during starting can significantly reduce the starting current. The concept is tested using a small experimental motor. Series inductors are added to the motor to make it more inductive and look more like a larger machine. The experimental results confirm that the method works. It is also found that the parallel capacitors require series filters to prevent harmonic current, and these can be realized using inductors in series with the compensation capacitors. Point-on switching using solid-state relays was tested, and these can reduce the transient switch-on current over the first voltage cycle. Full article
(This article belongs to the Special Issue Modelling and Simulation of Rotating Machines)
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Article
Optimization Model for the Integration of the Electric System and Gas Network: Peruvian Case
Energies 2022, 15(10), 3847; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103847 - 23 May 2022
Viewed by 363
Abstract
This paper presents a method for multi-period optimization of natural gas and electric power systems incorporating gas-fired power plants to analyze the impact of the interdependence between those commodities, in terms of cost and energy supply. The proposed method considers electricity network constraints, [...] Read more.
This paper presents a method for multi-period optimization of natural gas and electric power systems incorporating gas-fired power plants to analyze the impact of the interdependence between those commodities, in terms of cost and energy supply. The proposed method considers electricity network constraints, such as voltage profile, electrical losses, and limits of the transmission lines, as well as the technical restrictions on the gas network, such as the diameter, length, pressure, and limits for those variables. The proposed method was applied to a 12-bus electric network and a 7-node gas network, and several interdependencies between the electricity and the natural gas system network can be observed. The results show how the restrictions cause the behavior of the gas-fired power plants—in a low demand stage, it is restricted even when the gas-fired power generation prices are below the hydraulic generation prices, while in scenarios of higher demand, saturated cargo flows are observed, causing bus bar prices to be affected with higher operating costs. In this sense, the results of the variation in bus bar prices show little price stability in some bus bars in different stages, due to the behavior of the generation supply that is forced to operate by system restrictions. Full article
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Article
Research on Diagenetic Evolution and Hydrocarbon Accumulation Periods of Chang 8 Reservoir in Zhenjing Area of Ordos Basin
Energies 2022, 15(10), 3846; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103846 - 23 May 2022
Viewed by 330
Abstract
The Mesozoic Chang 8 Section in the Zhenjing area is a typical low permeability-tight sand reservoir and is regarded as the most important set of paybeds in the study area. Guided by the principles of basic geological theory, the diagenetic evolution process and [...] Read more.
The Mesozoic Chang 8 Section in the Zhenjing area is a typical low permeability-tight sand reservoir and is regarded as the most important set of paybeds in the study area. Guided by the principles of basic geological theory, the diagenetic evolution process and hydrocarbon accumulation periods of the Chang 8 reservoir in the study area were determined through various techniques. More specifically, core observation, scanning electron microscopy (SEM), X-ray diffraction (XRD), and vitrinite reflectance experiments were performed in combination with systematic studies on rock pyrolysis and the thermal evolutionary history of basins, the illite-dating method, and so on. The Chang 8 reservoir is dominated by feldspar lithic and lithic feldspar sandstones. Quartz, feldspar, and lithic fragments are the major clastic constituents. In clay minerals, the chlorite content is the highest, followed by illite/smectite formation and kaolinite, while the illite content is the lowest. The major diagenesis effect of the Chang 8 reservoir includes compaction, cementation, dissolution, metasomatism, and rupturing. The assumed diagenetic sequence is the following: mechanical composition → early sedimentation of chlorite clay mineral membrane → early cementation of sparry calcite → authigenic kaolinite precipitation → secondary production and amplification of quartz → dissolution of carbonate cement → dissolution of feldspar → late cementation of minerals such as ferrocalcite. Now, the study area is in Stage A in the middle diagenetic period. Through the inclusion of temperature measurements, in conjunction with illite dating and thermal evolutionary history analysis technology in basins, the Chang 8 reservoir of this study was determined as the phase-I continuous accumulation process and the reservoir formation epoch was 105~125 Ma, which was assigned to the Middle Early Cretaceous Epoch. Full article
(This article belongs to the Special Issue Natural Gas Hydrate and Deep-Water Hydrocarbon Exploration)
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Article
Optimization of Large-Scale Battery Storage Capacity in Conjunction with Photovoltaic Systems for Maximum Self-Sustainability
Energies 2022, 15(10), 3845; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103845 - 23 May 2022
Viewed by 399
Abstract
The photovoltaic array has gained popularity in the global electrical market. At the same time, battery storage, which is recently being placed by energy consumers alongside photovoltaics, continues to fall in price. Domestic and community loads may be combined utilizing central battery storage [...] Read more.
The photovoltaic array has gained popularity in the global electrical market. At the same time, battery storage, which is recently being placed by energy consumers alongside photovoltaics, continues to fall in price. Domestic and community loads may be combined utilizing central battery storage and shared solar power through an integrated grid or microgrid system. One of the main targets is maximum self-sustainability and independence of the microgrid system and implemented solution. This research study looks at the energy flows in a single household system that includes solar arrays and battery storage. The analysed household system is represented by a model which uses real load profiles from experimental measurements, local solar distribution, and onsite weather data. The results show that depending on the system configuration, two important parameters, self-consumption and self-sufficiency, can vary significantly. For a properly designed photovoltaic system, the energy self-consumption can be up to 90.19%, while self-sufficiency can be up to 82.55% for analysed cases. As an outcome, a large sample size with a variety of setups is recommended for a thorough examination of self-sustainability. Regional variations can worsen under different weather conditions, different photovoltaic and battery capacities, and different municipal rules. Full article
(This article belongs to the Special Issue Computer Simulation of Hybrid Energy System)
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Article
Energy Efficient Communication Design in UAV Enabled WPCN Using Dome Packing Method in Water Distribution System
Energies 2022, 15(10), 3844; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103844 - 23 May 2022
Viewed by 283
Abstract
The water distribution system has deployed several low-power IoT devices on an uneven surface where battery power is a major concern. Therefore, this paper focuses on using a UAV-enabled wireless powered communication network capable of directing energy to a target location and using [...] Read more.
The water distribution system has deployed several low-power IoT devices on an uneven surface where battery power is a major concern. Therefore, this paper focuses on using a UAV-enabled wireless powered communication network capable of directing energy to a target location and using it for communication, thereby reducing battery issues. In this paper, a static optimization was applied to find the initial height values using 3D clustering and beamforming method and dynamic optimization using extremum seeking method was applied to find the optimized height. The optimized height values were calculated and Travelling Salesman Problem (TSP) was applied to create the trajectory of the UAV. The overall energy consumption of the UAV was minimized by integrating dynamic optimization and dome packing method, which can find an optimal position and trajectory where the UAV will be hovering to direct energy and collect data. Moreover, we also minimized the total flight time of the UAV. Full article
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Article
Benefits Achieved by Energy Suppliers through Cooperation with Individual Recipients and Their Readiness for This Cooperation
Energies 2022, 15(10), 3843; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103843 - 23 May 2022
Viewed by 302
Abstract
The aim of this article is to identify the benefits perceived by individual recipients that are achieved by consumer energy suppliers on the market, through multilateral trade cooperation, and to define the structure of these benefits according to the declared readiness of recipients [...] Read more.
The aim of this article is to identify the benefits perceived by individual recipients that are achieved by consumer energy suppliers on the market, through multilateral trade cooperation, and to define the structure of these benefits according to the declared readiness of recipients to cooperate with the suppliers. The results of the analysis of the available literature on the subject indicate that there is a cognitive and research gap in relation to the perceived benefits achieved by the suppliers through joint marketing activities. The benefits are not being analyzed; especially from the perspective of individual recipients’ readiness for this cooperation. This gap is noticeable not only in relation to the energy market, but also in other areas of the consumer market. In an effort to reduce the identified gap, an online survey was conducted among 1196 adult individual energy recipients in Poland. The primary data collected was subjected to quantitative analysis using the following research methods: average grade analysis, comparative analysis, and exploratory factor analysis. The Kruskal–Wallis test was also conducted. The results of the quantitative analysis indicate, inter alia, that the majority of the respondents declared their readiness to cooperate with energy suppliers on the preparation of marketing offers. This variable statistically significantly differentiated nine out of twelve analyzed benefits that, according to the respondents, suppliers obtain as a result of cooperation. This differentiation was not found only in the case of three benefits related to the cost-free acquisition of recipient potential. For all respondents, as well as for the respondents willing to cooperate with suppliers and for those who did not express such willingness, three sections were identified, including the respondents who saw the same benefits achieved by suppliers. The conclusions drawn on the basis of the analysis results constitute a significant contribution to the theory of marketing and the theory of market behavior of individual recipients in the energy market. They also bear clear application advantages, making it easier for energy suppliers to effectively initiate cooperation with individual recipients and/or strengthen this cooperation. Full article
Article
Study on the Thermomechanical Response of Deep Buried Pipe Energy Piles under Temperature Load
Energies 2022, 15(10), 3842; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103842 - 23 May 2022
Viewed by 286
Abstract
A deep buried pipe energy pile (DBP-EP) is a composite structure that integrates ground-source heat pump (GSHP) systems and inside buried pipe energy piles (IBP-EP) to effectively achieve the improvement of heat transfer efficiency and quantity. Utilizing this technology in building a pile [...] Read more.
A deep buried pipe energy pile (DBP-EP) is a composite structure that integrates ground-source heat pump (GSHP) systems and inside buried pipe energy piles (IBP-EP) to effectively achieve the improvement of heat transfer efficiency and quantity. Utilizing this technology in building a pile foundation can contribute to reducing carbon emissions. This paper studies the variation rules of the thermomechanical response of DBP-EP under temperature load via field testing and numerical simulation. The results show that, under heating and cooling conditions, the DBP-EP temperature variation within the pile is substantial, while there is no significant change in the temperature field at the bottom of the pile. This is different from the internal temperature change of the temperature distribution of IBP-EP. The minimum axial average strain of the DBP-EP under the cooling condition is significantly smaller than that under the heating condition. However, the additional axial average strain under the temperature load is significantly larger than that in the heating condition, resulting in larger additional axial stress when the pile is cooled. The connection between the pile and foundation must considered in design due to the large settlement of the pile top under cooling conditions. When only under the temperature load, the maximum axial average pressure increments of the pile in our test during heating and cooling are −85.3 kN/°C and 99.4 kN/°C, respectively, suggesting that the additional load cannot be ignored. Full article
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Article
Performance Study of Methane Dry Reforming on Ni/ZrO2 Catalyst
Energies 2022, 15(10), 3841; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103841 - 23 May 2022
Viewed by 337
Abstract
Dry reforming of methane (DRM) has important and positive environmental and industrial impacts, as it consumes two of the top greenhouse gases in order to produce syngas (H2 and CO) and thus hydrogen (H2). The performance of DRM of conversions [...] Read more.
Dry reforming of methane (DRM) has important and positive environmental and industrial impacts, as it consumes two of the top greenhouse gases in order to produce syngas (H2 and CO) and thus hydrogen (H2). The performance of DRM of conversions of CH4 and CO2 was investigated over Ni/ZrO2 catalysts. The catalytic performance of all prepared catalysts for DRM was assessed in a micro-tubular fixed bed reactor under similar reaction conditions (i.e., activation and reaction temperatures at 700 °C, a feed flow rate of 70 mL/min, reaction temperature, and a 440 min reaction time). Various characterization techniques, such as BET, CO2-TPD, TGA, XRD, EDX, and TEM, were employed. The zirconia support was modified with MgO or Y2O3. The yttria-stabilized zirconia catalyst (5Ni15YZr) provided the optimum activity performance of CH4 and CO2 conversions of 56.1 and 64.3%, respectively, at 700 °C and a 70 mL/min flow rate; this catalyst also had the highest basicity. The Ni-based catalyst was promoted with Cs, Ga, and Sr. The Sr-promoted catalyst produced the highest enhancement of activity. The influence of the reaction temperature and the feed flow rate on 5Ni15YZr and 5NiSr15YZr indicated that the activity increased with the increase in the reaction temperature and lower feed flow rate. For 5Ni3Sr15YZr, at a reaction temperature of 800 °C, the CH4 and CO2 conversions were 76.3 and 79.9%, respectively, whereas at 700 °C, the conversions of CH4 and CO2 were 66.6 and 79.6% respectively. Full article
(This article belongs to the Special Issue Catalysis for Clean Energy and Environmental Sustainability)
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Article
Maximum Efficiency Conditions Satisfying Power Regulation Constraints in Multiple-Receivers Wireless Power Transfer
Energies 2022, 15(10), 3840; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103840 - 23 May 2022
Viewed by 292
Abstract
We propose the conditions for maximum overall efficiency at the constraint of satisfying asymmetric load power requirements for each receiver, for multiple-receivers wireless power transfer. Previously, the limitation of multiple-receiver analysis was that only the efficiency was maximized, whereas the requirements of load [...] Read more.
We propose the conditions for maximum overall efficiency at the constraint of satisfying asymmetric load power requirements for each receiver, for multiple-receivers wireless power transfer. Previously, the limitation of multiple-receiver analysis was that only the efficiency was maximized, whereas the requirements of load power were neglected. In many cases, conventional efficiency maximization assigns insufficient power to receivers far from the transmitter, while supplying excessive power to receivers near the transmitter. To resolve this limitation, we maximize the efficiency at the constraints of specified load power for each receiver. The proposed closed-form equation provides an optimum TX coil current amplitude, and the optimum load resistances of each receiver, to achieve the maximum efficiency at the load power regulation. Full article
(This article belongs to the Special Issue Next Generation Wireless Charging System for Mobile Devices)
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Article
Projecting and Forecasting the Latent Volatility for the Nasdaq OMX Nordic/Baltic Financial Electricity Market Applying Stochastic Volatility Market Characteristics
Energies 2022, 15(10), 3839; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103839 - 23 May 2022
Viewed by 300
Abstract
In this empirical study, multifactor stochastic volatility models for the financial Nordic/Baltic power markets are developed, implemented, and analyzed. Stochastic volatility projections are the primary aim, followed by volatility forecasts and market repercussions. The research provides a functional variant of the conditional distribution [...] Read more.
In this empirical study, multifactor stochastic volatility models for the financial Nordic/Baltic power markets are developed, implemented, and analyzed. Stochastic volatility projections are the primary aim, followed by volatility forecasts and market repercussions. The research provides a functional variant of the conditional distribution (f(x|y)) based on conditional moments and a long-simulated state vector realization (MCMC-GMM) that is evaluated on observed data (a non-linear Kalman Filter) and applicable for step-forward volatility forecasts. For front year and quarter financial electricity contracts, the SV model creates two mean-reverting factors: one persistent and slowly moving component and one choppy, rapidly moving component. According to these factors, static volatility predictions with optimum and generous lags have a Theil covariance percentage of well over 97 percent for the front year contracts and 86 percent for the front quarter contracts. The volatility visibility and its associated static forecasts improve market transparency and will eventually make diversification and risk management easier to implement. Full article
(This article belongs to the Special Issue Intelligent Control for Future Systems)
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Article
Design of Intelligent Solar PV Power Generation Forecasting Mechanism Combined with Weather Information under Lack of Real-Time Power Generation Data
Energies 2022, 15(10), 3838; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103838 - 23 May 2022
Viewed by 309
Abstract
In order to reduce the cost of data transmission, the meter data management system (MDMS) of the power operator usually delays time to obtain the power generation information of a solar photovoltaic (PV) power generation system. Although this approach solves the problem of [...] Read more.
In order to reduce the cost of data transmission, the meter data management system (MDMS) of the power operator usually delays time to obtain the power generation information of a solar photovoltaic (PV) power generation system. Although this approach solves the problem of data transmission cost, it brings more challenges to the solar PV power generation forecast. Because power operators usually need real-time solar PV power generation as a basis for the power dispatch, but considering the cost of communication, they cannot always provide corresponding historical power generation data in real time. In this study, an intelligent solar PV power generation forecasting mechanism combined with weather information is designed to cope with the issue of the absence of real-time power generation data. Firstly, the Pearson correlation coefficient analysis is used to find major factors with a high correlation in relation to solar PV power generation to reduce the computational burden of data fitting via a deep neural network (DNN). Then, the data preprocessing, including the standardization and the anti-standardization, is adopted for data-fitting or real-time solar PV power generation data to take as the input data of a long short-term memory neural network (LSTM). The salient features of the proposed DNN-LSTM model are: (1) only the information of present solar PV power generation is required to forecast the one at the next instant, and (2) an on-line learning mechanism is helpful to adjust the trained model to adapt different solar power plant or environmental conditions. In addition, the effectiveness of the trained model is verified by six actual solar power plants in Taiwan, and the superiority of the proposed DNN-LSTM model is compared with other forecasting models. Experimental verifications show that the proposed forecasting model can achieve a high accuracy of over 97%. Full article
(This article belongs to the Special Issue Selected Papers from iTIKI IEEE ICASI 2022 in Energies)
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Article
Numerical and Experimental Analysis of Heat Flow at Window-to-Wall Interface
Energies 2022, 15(10), 3837; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103837 - 23 May 2022
Viewed by 366
Abstract
External walls have a great influence on the thermal and humidity conditions in buildings as well as on the possibility of reducing energy consumption. While the structural and material aspects of walls and windows are well known, obtaining a tight connection to reduce [...] Read more.
External walls have a great influence on the thermal and humidity conditions in buildings as well as on the possibility of reducing energy consumption. While the structural and material aspects of walls and windows are well known, obtaining a tight connection to reduce thermal bridges between the window and walls still poses a significant problem. Therefore, a new window installation system proposed by the authors, eliminating linear and point thermal bridges at the window-to-wall interface, opens a pathway for lowering energy consumption in buildings and increasing thermal comfort and thermal efficiency. To prove the effectiveness of this system, numerical and experimental analyses of heat flow through an outer wall with a window were carried out. The numerical analyses were performed using the TRISCO software package. It was shown that the proposed solution eliminated the occurrence of linear thermal bridges at the window-to-wall interface (a linear heat transmittance coefficient Ψ ≈ 0.007, which meets the requirements of the passive house, was obtained). Thus, heat losses were reduced by nearly eight times compared to conventional installation systems. Numerical calculations were experimentally verified. Full article
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Article
Comparing the Energy System of a Facility with Uncertainty about Future Internal Carbon Prices and Energy Carrier Costs Using Deterministic Optimisation and Two-Stage Stochastic Programming
Energies 2022, 15(10), 3836; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103836 - 23 May 2022
Viewed by 279
Abstract
For an organisation, one aspect on the path to a decarbonised future is the cost-optimal decarbonisation of their facilities’ energy systems. One method to guide the decarbonisation is internal carbon pricing. However, the design process of decarbonisation pathways, guided by internal carbon prices, [...] Read more.
For an organisation, one aspect on the path to a decarbonised future is the cost-optimal decarbonisation of their facilities’ energy systems. One method to guide the decarbonisation is internal carbon pricing. However, the design process of decarbonisation pathways, guided by internal carbon prices, can be challenging, since the energy system environment consists of many uncertainties. Despite the numerous uncertainties and existing methods to address uncertainties during the optimisation process, the optimisation of a facility’s energy system is often done by assuming perfect knowledge of all relevant input parameters (deterministic optimisation). Since real-world decisions can never be based on perfect knowledge and certain decisions might lead to path dependencies, it is important to consider the robustness of a solution in the context of developments that vary from the assumed scenarios. So far, no academic work has analysed the potential benefits of using an optimisation method that considers uncertainty about future CO2 prices and energy carrier cost as two important input parameters during the optimisation process. This publication closes the knowledge gap by optimising a real-world energy system of a manufacturing site with two-stage stochastic programming and comparing it with methods of deterministic optimisation. The results show considerably more robust results for the solutions generated by stochastic programming. The total cost deviation does not exceed 52%, while the deviation of the deterministic results reaches up to 96%. The results also indicate that organisations should not analyse their energy systems by only considering uncertain internal carbon prices, but should examine the effects together with other important but uncertain parameters. Full article
(This article belongs to the Special Issue Energy Decision Making: Problems, Methods, and Tools)
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Article
Design of a Non-Linear Observer for SOC of Lithium-Ion Battery Based on Neural Network
Energies 2022, 15(10), 3835; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103835 - 23 May 2022
Viewed by 302
Abstract
This paper presents a method for use in estimating the state of charge (SOC) of lithium-ion batteries which is based on an electrochemical impedance equivalent circuit model with a controlled source. Considering that the open-circuit voltage of a battery varies with the SOC, [...] Read more.
This paper presents a method for use in estimating the state of charge (SOC) of lithium-ion batteries which is based on an electrochemical impedance equivalent circuit model with a controlled source. Considering that the open-circuit voltage of a battery varies with the SOC, an equivalent circuit model with a controlled source is proposed which the voltage source and current source interact with each other. On this basis, the radial basis function (RBF) neural network is adopted to estimate the uncertainty in the battery model online, and a non-linear observer based on the radial basis function of the RBF neural network is designed to estimate the SOC of batteries. It is proved that the SOC estimation error is ultimately bounded by Lyapunov stability analysis, and the error bound can be arbitrarily small. The high accuracy and validity of the non-linear observer based on the RBF neural network in SOC estimation are verified with experimental simulation results. The SOC estimation results of the extended Kalman filter (EKF) are compared with the proposed method. It improves convergence speed and accuracy. Full article
(This article belongs to the Special Issue Lithium-Ion Batteries: Latest Advances, Challenges and Prospects)
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Review
Internet of Things Approaches for Monitoring and Control of Smart Greenhouses in Industry 4.0
Energies 2022, 15(10), 3834; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103834 - 23 May 2022
Viewed by 386
Abstract
In recent decades, climate change and a shortage of resources have brought about the need for technology in agriculture. Farmers have been forced to use information and innovation in communication in order to enhance production efficiency and crop resilience. Systems engineering and information [...] Read more.
In recent decades, climate change and a shortage of resources have brought about the need for technology in agriculture. Farmers have been forced to use information and innovation in communication in order to enhance production efficiency and crop resilience. Systems engineering and information infrastructure based on the Internet of Things (IoT) are the main novel approaches that have generated growing interest. In agriculture, IoT solutions according to the challenges for Industry 4.0 can be applied to greenhouses. Greenhouses are protected environments in which best plant growth can be achieved. IoT for smart greenhouses relates to sensors, devices, and information and communication infrastructure for real-time monitoring and data collection and processing, in order to efficiently control indoor parameters such as exposure to light, ventilation, humidity, temperature, and carbon dioxide level. This paper presents the current state of the art in the IoT-based applications to smart greenhouses, underlining benefits and opportunities of this technology in the agriculture environment. Full article
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Article
Design of an MPPT Technique for the Indirect Measurement of the Open-Circuit Voltage Applied to Thermoelectric Generators
Energies 2022, 15(10), 3833; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103833 - 23 May 2022
Viewed by 425
Abstract
This paper presents the design of a maximum power point-tracking (MPPT) technique for DC–DC converters that are used in energy-harvesting systems based on thermoelectric generators. This technique is based on the analysis of the characteristics of the converter to measure the open-circuit voltage [...] Read more.
This paper presents the design of a maximum power point-tracking (MPPT) technique for DC–DC converters that are used in energy-harvesting systems based on thermoelectric generators. This technique is based on the analysis of the characteristics of the converter to measure the open-circuit voltage indirectly. The main contribution of this article is that the algorithm measures the voltage at the maximum power point without the need to disconnect the source of the circuit, as happens when the fractional open-circuit voltage (FOCV) technique is used. The algorithm is based on a predetermined initial duty cycle, which is applied to the circuit, and the input voltage and input current are read. With these values, the open-circuit voltage and short-circuit current are calculated with equations obtained from the circuit. Then, it calculates the duty cycle at the maximum power point and applies it to the circuit. If this duty cycle does not obtain the maximum power from the circuit, the algorithm starts a second stage based on fuzzy logic to calculate an increase or decrease in the duty cycle. The designed technique was evaluated using a topology based on a DC–DC flyback converter variant and was compared with the P&O technique and obtained better results. The designed technique provides between 3.9% and 5.6% more power to the load than the P&O technique in a 20 W system. Full article
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Article
Sensitivity Analysis of High-Pressure Methanol—Steam Reformer Using the Condensation Enthalpy of Water Vapor
Energies 2022, 15(10), 3832; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103832 - 23 May 2022
Viewed by 292
Abstract
A methanol–steam reformer (MSR) can safely provide hydrogen-rich fuel for a fuel cell system. Since the operating temperature of an MSR is relatively low, convective heat transfer is typically used to provide thermal energy to the endothermic reactions in the MSR. In this [...] Read more.
A methanol–steam reformer (MSR) can safely provide hydrogen-rich fuel for a fuel cell system. Since the operating temperature of an MSR is relatively low, convective heat transfer is typically used to provide thermal energy to the endothermic reactions in the MSR. In this study, the use of phase change heat transfer to provide thermal energy to the endothermic reactions was investigated, which enhanced the temperature uniformity longitudinally along the MSR. ANSYS Fluent® software was used to investigate the performance of the reforming reactions. A comparative analysis using sensible heat and latent heat as the heat supply sources was performed. Using latent heat as a heat source achieved a lesser temperature drop than sensible heat that was under 5.29 K in the outer pipe. Moreover, a sensitivity analysis of methanol–steam-reforming reactions that use phase change heat transfer in terms of the carbon ratio, gas hourly velocity (for the inner and outer pipes of the MSR), inlet temperature (inner and outer pipes), reactor length, and operating pressure (inner pipe) was performed. When the phase change energy of water vapor is used, the wall temperature of the MSR is conveniently controlled and is uniformly distributed along the channel (standard deviation: 0.81 K). Accordingly, the methanol conversion rate of an MSR that uses phase change energy is ~4% higher than that of an MSR that employs convective heat transfer. Full article
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Editorial
Integrated Solar Thermal Systems
Energies 2022, 15(10), 3831; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103831 - 23 May 2022
Viewed by 287
Abstract
The renewable energy technologies attracted 70% global energy investment in 2021, but the global CO2 emission is increased by 1 [...] Full article
(This article belongs to the Special Issue Integrated Solar Thermal Systems)
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Review
Iron Recovery Technology of Red Mud—A review
Energies 2022, 15(10), 3830; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103830 - 23 May 2022
Viewed by 302
Abstract
RM (red mud), which comes from the Bayer process, has a huge annual output and is harmful to the environment. Because of the high iron content in RM, the process of iron recovery from RM can reduce the amount of RM well and [...] Read more.
RM (red mud), which comes from the Bayer process, has a huge annual output and is harmful to the environment. Because of the high iron content in RM, the process of iron recovery from RM can reduce the amount of RM well and create economic benefits, so it is a promising process. The paper focuses on the review on the research of the iron recovery method from RM, which includes the physical recovery method, chemical recovery method and emerging recovery method. By comparing the advantages and disadvantages of these processes, it is concluded that the fluidized bed reduction is a promising process that can be rapidly applied to the industry, but it still needs more investigation to overcome the current technical difficulties in the near future. Full article
(This article belongs to the Topic Green Mining)
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Article
Comparative Analysis of Overheating Risk for Typical Dwellings and Passivhaus in the UK
Energies 2022, 15(10), 3829; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103829 - 23 May 2022
Viewed by 335
Abstract
There is growing concern that airtight and well-insulated buildings designed to limit heat loss in temperate and cold climates could unintentionally elevate the risk of overheating in summers. Existing literature primarily uses dynamic simulation to investigate this problem due to the difficulty of [...] Read more.
There is growing concern that airtight and well-insulated buildings designed to limit heat loss in temperate and cold climates could unintentionally elevate the risk of overheating in summers. Existing literature primarily uses dynamic simulation to investigate this problem due to the difficulty of obtaining large-scale in-performance data. To address this gap, we undertake a meta-analysis of large-scale indoor air temperature data for 195 UK dwellings, as a study of performance in a temperate climate. Of these, 113 are baseline (i.e., typical existing dwellings) and the rest designed to the high-performance Passivhaus standard. Using both Passivhaus and the well-known CIBSE TM59 overheating standards, this study found that there were few overheated cases for any building type. However, the average summer nighttime temperature of Passivhaus bedrooms was 1.6 °C higher than baseline, with 20 out of 31 measured bedrooms exceeding the overheating criterion, and the average overheating hours constituting approximately 19% of the total summertime observation period. These findings suggest that bedrooms in highly insulated dwellings may pose an overheating risk although whole-dwelling overheating risk is low. Full article
(This article belongs to the Topic Sustainable Built Environment)
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Article
A Numerical Evaluation of Coal Seam Permeability Derived from Borehole Gas Flow Rate
Energies 2022, 15(10), 3828; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103828 - 23 May 2022
Viewed by 328
Abstract
Coal seam permeability is a critical factor in coal seam gas extraction and gas outburst control. In Australian coal mines, coal seam permeability is normally estimated using a packer test or drill stem test. In contrast, Chinese coal mines generally estimate a parameter [...] Read more.
Coal seam permeability is a critical factor in coal seam gas extraction and gas outburst control. In Australian coal mines, coal seam permeability is normally estimated using a packer test or drill stem test. In contrast, Chinese coal mines generally estimate a parameter called the “gas conductivity coefficient” by measuring natural gas flow rates from an underground borehole drilled through a coal seam. With this method, it has been frequently reported that the permeability of many Chinese coal seams is between 0.0001 mD and 0.01 mD, which is extremely low compared to that of Australian coal seams (1–100 mD). It is therefore natural to wonder how closely the Chinese method measures permeability. Resolving this question will allow knowledge and experience in outburst management to be shared between Australian and Chinese coal mines. This question is investigated by the numerical modelling of gas desorption and flow through a seam of known permeability and by using the model’s borehole gas flow rate to estimate the permeability using the Chinese method. A total of 126 simulations were run with various input reservoir parameters. The results suggest that the Chinese method estimates permeability at an accuracy of 85% to 100%, which is adequate for mine pre-drainage design and outburst control. For the high diffusion rate (e.g., high gas content and short desorption time) and low Darcy flow rates (e.g., low permeability), these errors are reduced. Full article
(This article belongs to the Special Issue Gas Production from Coal Seam Gas/Deep Coal Seam Gas Reservoirs)
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Article
Optimal Scheduling of Movable Electric Vehicle Loads Using Generation of Charging Event Matrices, Queuing Management, and Genetic Algorithm
Energies 2022, 15(10), 3827; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103827 - 23 May 2022
Viewed by 446
Abstract
The extensive adoption of electric vehicles (EVs) can introduce negative impacts on electric infrastructure in the form of sporadic and excessive charging demands, line overload, and voltage quality. Because EV loads can be movable around the system and time-dependent due to human daily [...] Read more.
The extensive adoption of electric vehicles (EVs) can introduce negative impacts on electric infrastructure in the form of sporadic and excessive charging demands, line overload, and voltage quality. Because EV loads can be movable around the system and time-dependent due to human daily activities, it is therefore proposed in this research to investigate the spatial effects of EV loads and their impacts on a power system. We developed a behavior-based charging profile simulation for daily load profiles of uncontrolled and controlled charging simulations. To mitigate the impact of increased peak demand, we proposed an optimal scheduling method by genetic algorithm (GA) using charging event matrices and EV queuing management. The charging event matrices are generated by capturing charging events and serve as an input of the GA-based scheduling, which optimally defines available charging slots while maximizing the system load factor while maintaining user satisfaction, depending on the weight coefficients prioritized by the system operator. The EV queuing management strategically selects EVs to be filled in the available slots based on two qualification indicators: previous charging duration and remaining state of charge (SoC). The proposed methodology was tested on a modified IEEE-14 bus system with 3 generators and 20 transmission lines. The simulation results show that the developed methodology can efficiently manage the peak demand while respecting the system’s operational constraints and the user satisfaction level. Full article
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Article
Permanent Magnet Generator for a Gearless Backyard Wind Turbine
Energies 2022, 15(10), 3826; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103826 - 23 May 2022
Viewed by 341
Abstract
This paper presents the design of a permanent magnet generator for a gearless backyard wind turbine. The magnetisation characteristics of the rotor steel and the stator at different field strength ranges were considered at the design stage and mathematically described using a model [...] Read more.
This paper presents the design of a permanent magnet generator for a gearless backyard wind turbine. The magnetisation characteristics of the rotor steel and the stator at different field strength ranges were considered at the design stage and mathematically described using a model in Matlab. The detailed calculations and the design of the planar model were carried out using FEMM software. The high-quality results obtained from the calculations shown in the paper made it possible to make a real model of the generator. This paper presents views of the stator package, the rotor, the entire generator and selected test results. The parameter of this turbine that distinguishes it from a wide range of manufactured generators is its low, non-standard rotational speed and low breakaway torque, which allows the power plant to start in winds of approximately 2 m/s. Other advantages of this generator is its low weight resulting from the use of a light rotor and light alloys for the generator housing. Full article
(This article belongs to the Special Issue The Development of Renewable Energies in Poland)
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Article
Swiveling Magnetization for Anisotropic Magnets for Variable Flux Spoke-Type Permanent Magnet Motor Applied to Electric Vehicles
Energies 2022, 15(10), 3825; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103825 - 23 May 2022
Viewed by 341
Abstract
This paper investigates the application of anisotropic low-coercive force (LCF) magnets to a novel variable-flux spoke-type permanent magnet synchronous motor (VFS-PMSM) for electrical vehicles with a wide speed range. In the VFS-PMSM, flux is regulated by swiveling the magnetization of the anisotropic LCF [...] Read more.
This paper investigates the application of anisotropic low-coercive force (LCF) magnets to a novel variable-flux spoke-type permanent magnet synchronous motor (VFS-PMSM) for electrical vehicles with a wide speed range. In the VFS-PMSM, flux is regulated by swiveling the magnetization of the anisotropic LCF magnets instead of directly magnetizing or demagnetizing them. The previously proposed VFS-PMSM uses only isotropic LCF magnets for easily swiveling the magnetic pole direction, resulting in lower torque density. The challenge thus lies in the feasibility to swivel the magnetic pole direction of the anisotropic LCF magnet, and the impact of the different magnetization strengths of the anisotropic magnets on the motor performance. This paper first studies the feasibility to swivel the magnetization direction of anisotropic LCF magnets through experiments. It is confirmed that the magnetization direction can be successfully swiveled by 90 degrees with a reduced external magnetizing field. Then, two VFS-PMSM topologies and various rotor configurations are compared in terms of key performance indices to determine critical sizing factors for performance enhancement. Finite element analysis is used for simulations. In comparison with the VFS-PMSM equipped with isotropic LCF magnets, the maximum torque of the proposed topology can be improved for the same flux adjustment ability. Alternatively, the flux adjustment ability can also be enhanced by 37.43% for the same maximum torque. Full article
(This article belongs to the Topic Application of Innovative Power Electronic Technologies)
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Article
Study on a Discharge Circuit Prediction Model of High-Voltage Electro-Pulse Boring Based on Bayesian Fusion
Energies 2022, 15(10), 3824; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103824 - 23 May 2022
Viewed by 460
Abstract
It is necessary to develop new drilling and breaking technology for hard rock construction. However, the process of high-voltage electro-pulse (HVEP) rock-breaking is complex, and the selection of electro-pulse boring (EPB) process parameters lacks a theoretical basis. Firstly, the RLC model, TV-RLC model, [...] Read more.
It is necessary to develop new drilling and breaking technology for hard rock construction. However, the process of high-voltage electro-pulse (HVEP) rock-breaking is complex, and the selection of electro-pulse boring (EPB) process parameters lacks a theoretical basis. Firstly, the RLC model, TV-RLC model, and TV-CRLC model are established based on the characteristics of the HVEP circuit to predict the EPB dynamic discharge curve. Secondly, the parameters are identified by the Particle Swarm Optimization Genetic Algorithm (PSO-GA). Finally, due to the nonlinear and complex time-varying characteristics of the discharge circuit, the discharge circuit prediction models based on Bayesian fusion and current residual normalization fusion method are proposed, and the optimal weight of these three models is determined. Compared with the single models for EPB current prediction, the average relative error reduction rates based on Bayesian fusion and current residual normalization fusion methods are 25.5% and 9.5%, respectively. In this paper, the discharge circuit prediction model based on Bayesian fusion is established, which improves the prediction accuracy and reliability of the model, and it guides the selection of process parameters and the design of pulse power supply and electrode bits. Full article
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Article
Integration of Electromagnetic Geophysics Forward Simulation in Coupled Flow and Geomechanics for Monitoring a Gas Hydrate Deposit Located in the Ulleung Basin, East Sea, Korea
Energies 2022, 15(10), 3823; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103823 - 23 May 2022
Viewed by 500
Abstract
We investigate the feasibility of electromagnetic (EM) geophysics methods to detect the dissociation of gas hydrate specifically from a gas hydrate deposit located in the Ulleung Basin, East Sea, Korea via an integrated flow-geomechanics-EM geophysics simulation. To this end, coupled flow and geomechanics [...] Read more.
We investigate the feasibility of electromagnetic (EM) geophysics methods to detect the dissociation of gas hydrate specifically from a gas hydrate deposit located in the Ulleung Basin, East Sea, Korea via an integrated flow-geomechanics-EM geophysics simulation. To this end, coupled flow and geomechanics simulation is first performed with the multiple porosity model employed, where a mixed formulation with the finite volume (FV) and finite element (FE) methods are taken for the flow and geomechanics, respectively. From the saturation and porosity fields obtained from the coupled flow and geomechanics, the electrical conductivity model is established for the EM simulation. Solving the partial differential equation of electrical diffusion which is linearized using the 3D finite element method (FEM), the EM fields are then computed. For numerical experiments, particularly two approaches in the configuration for the EM methods are compared in this contribution: the surface-to-surface and the surface-to-borehole methods. When the surface-to-surface EM method is employed, the EM is found to be less sensitive, implying low detectability. Especially for the short term of production, the low detectability is attributed to the similarity of electrical resistivity between the dissociated gas (CH4) and hydrate as well as the specific dissociation pattern within the intercalated composites of the field. On the other hand, when the surface-to-borehole EM method is employed, its sensitivity to capture the produced gas flow is improved, confirming its detectability in monitoring gas flow. Hence, the EM geophysics simulation integrated with coupled flow and geomechanics can be a potential tool for monitoring gas hydrate deposits. Full article
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Article
Overview of Battery Impedance Modeling Including Detailed State-of-the-Art Cylindrical 18650 Lithium-Ion Battery Cell Comparisons
Energies 2022, 15(10), 3822; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103822 - 23 May 2022
Viewed by 516
Abstract
Electrical models of battery cells are used in simulations to represent batteries’ behavior in various fields of research and development involving battery cells and systems. Electrical equivalent circuit models, either linear or nonlinear, are commonly used for this purpose and are presented in [...] Read more.
Electrical models of battery cells are used in simulations to represent batteries’ behavior in various fields of research and development involving battery cells and systems. Electrical equivalent circuit models, either linear or nonlinear, are commonly used for this purpose and are presented in this article. Various commercially available cylindrical, state-of-the-art lithium-ion battery cells, both protected and unprotected, are considered. Their impedance properties, according to four different equivalent circuit models, are measured using electrochemical impedance spectroscopies. Furthermore, the pricing, impedance, specific energy, and C-rate of the chosen battery cells are compared. For example, it is shown that the energy density of modern 18650 cells can vary from a typical value of 200 to about 260 Wh kg−1, whereas the cell price can deviate by a factor of about 3 to 5. Therefore, as a result, this study presents a concise but comprehensive battery parameter library that should aid battery system designers or power electronic engineers in conducting battery simulations and in selecting appropriate battery cells based on application-specific requirements. In addition, the accuracies and computational efforts of the four equivalent circuit models are compared. Full article
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Article
Electromagnetic Torque Fluctuating Properties under Dynamic RISC Fault in Turbogenerators
Energies 2022, 15(10), 3821; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103821 - 23 May 2022
Viewed by 345
Abstract
This paper analyzes the electromagnetic torque (EMT) fluctuation characteristics in synchronous generators under rotor interturn short-circuit (DRISC) fault. The novelty of this paper is that the DRISC fault is proposed based on the intermittent interturn short circuit existing in the actual operation and [...] Read more.
This paper analyzes the electromagnetic torque (EMT) fluctuation characteristics in synchronous generators under rotor interturn short-circuit (DRISC) fault. The novelty of this paper is that the DRISC fault is proposed based on the intermittent interturn short circuit existing in the actual operation and compared with the static rotor interturn short-circuit (SRISC) fault. In the work, by studying the influence of DRISC with different positions and different short-circuit degrees, the fluctuation characteristic of the EMT is analyzed and verified. The results show that when the DRISC5% fails, the location is in slot 3, the amplitude of first harmonic decreases by 7.2%, second harmonic amplitude increases by 33.4%, third harmonic decreases by 4.3%, and fourth harmonic increases by 26.8%. As the degree increased and positioned away from the large tooth of the DRISC, the overall EMT amplitude and reverse pulse increased, first and third harmonics decreased, and second and fourth harmonics increased. Full article
(This article belongs to the Special Issue Condition Monitoring and Failure Prevention of Electric Machines)
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Review
A Critical Review of Alkaline Flooding: Mechanism, Hybrid Flooding Methods, Laboratory Work, Pilot Projects, and Field Applications
Energies 2022, 15(10), 3820; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103820 - 22 May 2022
Viewed by 557
Abstract
Over time, the dependence on oil has increased to meet industrial and domestic needs. Enhanced oil recovery (EOR) techniques in this regard have captured immense growth as EOR is not only used to increase the oil recovery but also to augment the sweep [...] Read more.
Over time, the dependence on oil has increased to meet industrial and domestic needs. Enhanced oil recovery (EOR) techniques in this regard have captured immense growth as EOR is not only used to increase the oil recovery but also to augment the sweep efficiency. Several techniques over the past decades have been used to improve oil recovery with cost-effectiveness. Cost-effective alkaline flooding has been effective for those oil reservoirs with a high total acid number. In this review, the significance of alkaline flooding has been discussed in detail, as well as the features of alkaline flooding in comparison to other modes of flooding. This review entails (1) alkaline flooding, (2) hybrid modes of injection, (3) experimental work, (4) pilot projects, (5) screening criteria, and (6) field applications. The findings of this study can help increase the understanding of alkaline flooding and provide a holistic view of the hybrid modes of flooding. Full article
(This article belongs to the Topic Enhanced Oil Recovery Technologies)
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Article
Low-Cost HEM with Arduino and Zigbee Technologies in the Energy Sector in Colombia
Energies 2022, 15(10), 3819; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103819 - 22 May 2022
Viewed by 414
Abstract
Since no solutions have been proposed in Colombia that seek to reduce the consumption of electricity at the residential level, this paper describes the design and implementation of a simple prototype of a low-cost home energy management system (HEMS). The objective of this [...] Read more.
Since no solutions have been proposed in Colombia that seek to reduce the consumption of electricity at the residential level, this paper describes the design and implementation of a simple prototype of a low-cost home energy management system (HEMS). The objective of this platform is to monitor the energy consumption of typical household devices so that users can access the consumption of each device separately and then establish the strategy that allows them to reduce energy consumption at home. In order to demonstrate that our system is viable, the system has been evaluated by measuring weekly energy consumption with the on-line and off-line HEMS using a test bench with typical household devices in a Sincelejo typical household. The evaluation has shown that with the installation of this HEMS, consumption is reduced by 27%. This shows that it is possible to achieve a good reduction percentage with a low-cost system. Full article
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