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Energies, Volume 15, Issue 11 (June-1 2022) – 331 articles

Cover Story (view full-size image): Tangential inlet return cyclones are used as the first stage of air filtration for vehicle engines operating in dusty conditions. The filtration efficiency of cyclones was increased by modifying their construction. The symmetrical inlet channel was replaced by an asymmetrical channel, and the cylindrical outlet tube by a conical tube with a streamlined inlet opening. Experimental tests of each cyclone modification were performed for air flow rate QG = 5-30 m3/h. A polydisperse AC-fine test dust with a concentration of 1 g/m3 was used. An (approximately 1%) increase in separation efficiency was obtained for small (up to QG = 22 m3/h) air flux values and an approximately 30% decrease in pressure drop over the entire QG range. There was an increase in filtration accuracy for small and large QG. View this paper
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Article
A Catalytic Effectiveness Factor for a Microbial Electrolysis Cell Biofilm Model
Energies 2022, 15(11), 4179; https://doi.org/10.3390/en15114179 - 06 Jun 2022
Viewed by 399
Abstract
The aim of this work is to propose a methodology to obtain an effectiveness factor for biofilm in a microbial electrolysis cell (MEC) system and use it to reduce a partial differential equation (PDE) biofilm MEC model to an ordinary differential equation (ODE) [...] Read more.
The aim of this work is to propose a methodology to obtain an effectiveness factor for biofilm in a microbial electrolysis cell (MEC) system and use it to reduce a partial differential equation (PDE) biofilm MEC model to an ordinary differential equation (ODE) MEC model. The biofilm mass balances of the different species are considered. In addition, it is considered that all the involved microorganisms are attached to the anodic biological film. Three effectiveness factors are obtained from partial differential equations describing the spatial distributions of potential and substrate in the biofilm. Then, a model reduction is carried out using the global mass balances of the different species in the system. The reduced model with three uncertain but bounded effectiveness factors is evaluated numerically and analyzed in the sense of stability and parametric sensibility to demonstrate its applicability. The reduced ODE model is compared with a validated model taken from the literature, and the results are in good agreement. The biofilm effectiveness factor in MEC systems can be extended to the reduction of PDE models to obtain ODE models that are commonly used in optimization and control problems. Full article
(This article belongs to the Special Issue Biological Processes in the Green Hydrogen Value Chain)
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Review
Application of Microalgae Biomass for Biodiesel Fuel Production
Energies 2022, 15(11), 4178; https://doi.org/10.3390/en15114178 - 06 Jun 2022
Viewed by 396
Abstract
Recently, there has been a growing interest in the use of new types of cheaper raw materials for biodiesel production. There are many prospects for microalgae, which do not compete for land with conventional biodiesel raw materials, are characterized by rapid reproduction and [...] Read more.
Recently, there has been a growing interest in the use of new types of cheaper raw materials for biodiesel production. There are many prospects for microalgae, which do not compete for land with conventional biodiesel raw materials, are characterized by rapid reproduction and high biomass accumulation, and under certain conditions, some are able to accumulate a large amount of oil. A number of studies have been conducted on the extraction of oil from microalgae cells and transesterification with various acyl receptors. This paper provides an overview of the results of research on microalgal biomass preparation and oil extraction. Indicators of the quality of the oil are presented and its suitability for biodiesel synthesis is analyzed. The homogeneous and heterogeneous catalysts used for oil transesterification are described and the optimal conditions of the process when using various alcohols as acyl receptors are presented. Much attention is paid to the parameters affecting the transesterification efficiency and biodiesel yield. The physical and chemical, and operational and environmental properties of biodiesel obtained from algae oil are analyzed. The evaluation of the economic efficiency of biodiesel synthesis is also presented. Full article
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Article
Power Production from Produced Waters via Reverse Electrodialysis: A Preliminary Assessment
Energies 2022, 15(11), 4177; https://doi.org/10.3390/en15114177 - 06 Jun 2022
Viewed by 360
Abstract
Wastewaters generated by crude oil extraction processes, called “produced waters” (PWs), are complex solutions that contain organic compounds, mainly hydrocarbons, and often exhibit high salinity. The large amounts of PWs represent a global issue because of their environmental impact. An approach widely used [...] Read more.
Wastewaters generated by crude oil extraction processes, called “produced waters” (PWs), are complex solutions that contain organic compounds, mainly hydrocarbons, and often exhibit high salinity. The large amounts of PWs represent a global issue because of their environmental impact. An approach widely used in the oil industry is the reinjection of this wastewater into the extraction wells after a suitable treatment. The high salt concentration of such solutions may be used in salinity gradient technologies to produce green electricity. Among these technologies, reverse electrodialysis (RED) is one of the most promising. In this work, the application of RED for energy generation from two different real oil industry brines was investigated. An experimental campaign was performed by testing 10 × 10 cm2 units in long-run continuous operations, monitoring the performance for more than 25 days. Fouling phenomena, occurring during the continuous operation, decrease the unit performance and several anti-fouling strategies were adopted to tackle this issue. As a result, a positive net power density for up to 18 days of continuous operation was obtained. A maximum power density of about 2.5 W/m2 was observed, demonstrating how the RED technology could be an important strategy to harvest energy from an industrial waste. Full article
(This article belongs to the Special Issue Towards Zero-Waste Cities: Advancement in Waste-to-Energy)
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Review
A Critical Review of Modular Multilevel Converter Configurations and Submodule Topologies from DC Fault Blocking and Ride-Through Capabilities Viewpoints for HVDC Applications
Energies 2022, 15(11), 4176; https://doi.org/10.3390/en15114176 - 06 Jun 2022
Cited by 1 | Viewed by 332
Abstract
Modular multilevel converters (MMCs) based on half-bridge submodules (HBSMs) are unable to prevent the AC side contribution to DC side fault currents, thus necessitating circuit breakers (CBs) for protection. A solution to this problem is using submodules (SMs) that are capable of blocking [...] Read more.
Modular multilevel converters (MMCs) based on half-bridge submodules (HBSMs) are unable to prevent the AC side contribution to DC side fault currents, thus necessitating circuit breakers (CBs) for protection. A solution to this problem is using submodules (SMs) that are capable of blocking the flow of current from the AC grid to feed the DC side fault. The full-bridge submodule (FBSM) is one type of fault blocking SM where the presence of two extra switches ensures that in the event of a DC fault, the reverse voltage from the FBSM capacitor is placed in the path of the AC side current feeding the DC side fault through the antiparallel diodes. However, the additional semiconductor switches in the FBSMs increase the converter cost, complexity, and losses. Several SM configurations have been proposed in recent years that provide DC fault blocking capability with lower losses and device counts than those of FBSMs. Besides, many of the proposed hybrid converter configurations that combine different topologies to optimize converter performance are also capable of providing DC fault blocking. Furthermore, certain SM topologies are capable of riding through DC faults by remaining deblocked and operating in static synchronous compensator (STATCOM) mode to provide reactive power support to the AC grid. In this paper, noteworthy SM and MMC configurations capable of DC fault blocking and ride-through are reviewed and compared in terms of component requirements, semiconductor losses, and DC fault handing capability. The review also includes a discussion on control strategies for MMC arm/leg energy balancing during STATCOM operation. Full article
(This article belongs to the Section A3: Power Electronics)
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Article
Thermal—Airflow Coupling in Hourly Energy Simulation of a Building with Natural Stack Ventilation
Energies 2022, 15(11), 4175; https://doi.org/10.3390/en15114175 - 06 Jun 2022
Viewed by 350
Abstract
Natural ventilation dominates in Polish residential buildings. It is a simple and low-cost system but its performance is affected by varying environmental conditions. Hence, setting up constant ventilation airflow results in errors when calculating heating and cooling energy. In this paper, an attempt [...] Read more.
Natural ventilation dominates in Polish residential buildings. It is a simple and low-cost system but its performance is affected by varying environmental conditions. Hence, setting up constant ventilation airflow results in errors when calculating heating and cooling energy. In this paper, an attempt to integrate the buoyancy effect in natural ventilation of a residential building at hourly resolution with the hourly simulation method of EN ISO 13790 to obtain energy use for space heating and cooling is presented. The ping-pong coupling algorithm was proposed and applied. Hourly variation of ventilation airflow rate was from −26.8 m3/h (flow from outdoor to the interior of the building) to 87.2 m3/h with 55 m3/h on average. The lack of a cooling system resulted in overheating during summer and indicated the necessity of its application or use of other techniques to reduce solar gains. Application of the cooling system resulted in an hourly ventilation rate from −38.0 m3/h to 87.2 m3/h. Detailed simulation in EnergyPlus and statistical analysis proved the applicability of the proposed method in stack-induced ventilation assessment. The coefficient of determination R2 = 0.936, mean squared error MAE = 5.72 m3/h and root mean square error RMSE = 7.86 m3/h. Full article
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Article
A Core Damage Constitutive Model for the Time-Dependent Creep and Relaxation Behavior of Coal
Energies 2022, 15(11), 4174; https://doi.org/10.3390/en15114174 - 06 Jun 2022
Viewed by 337
Abstract
The creep and stress relaxation behaviors of coal are common in coal mining. The unified constitutive model is suitable to describe and predict both the creep and relaxation evolution characteristics of rocks. The generalized Kelvin model is the core element for traditional and [...] Read more.
The creep and stress relaxation behaviors of coal are common in coal mining. The unified constitutive model is suitable to describe and predict both the creep and relaxation evolution characteristics of rocks. The generalized Kelvin model is the core element for traditional and improved component models to reflect both the nonlinear creep and relaxation. In this paper, an improved core damage model, which could both reflect the creep and stress relaxation in relation to the damage evolution, was established based on a comparison of the traditional and improved component models, and the responding constitutive equations (creep and stress relaxation equation) at constant stress/strain were deduced. Then, the core damage model was validated to the uniaxial compressive multistage creep and stress relaxation test results of coal, showing that the model curves had great accordance with the experimental data. Moreover, the model comparisons on accuracy, parameter meaning, and popularization among the core damage model, hardening-damage model, and the fractional derivative model were further discussed. The results showed that the parameters in the core damage model had clear and brief physical significances. The core damage model was also popularized to depict the time-dependent behaviors of other rocks, showing great accuracy. Full article
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Article
BIPV Modeling with Artificial Neural Networks: Towards a BIPV Digital Twin
Energies 2022, 15(11), 4173; https://doi.org/10.3390/en15114173 - 06 Jun 2022
Viewed by 392
Abstract
Modeling the photovoltaic (PV) energy output with high accuracy is essential for predicting and analyzing the performance of a PV system. In the particular cases of building-integrated and building-attached photovoltaic systems (BIPV and BAPV, respectively) the time-varying partial shading conditions are a relevant [...] Read more.
Modeling the photovoltaic (PV) energy output with high accuracy is essential for predicting and analyzing the performance of a PV system. In the particular cases of building-integrated and building-attached photovoltaic systems (BIPV and BAPV, respectively) the time-varying partial shading conditions are a relevant added difficulty for modeling the PV power conversion. The availability of laser imaging detection and ranging (LIDAR) data to create very-high-resolution elevation digital models can be effectively used for computing the shading at high resolution. In this work, an artificial neural network (ANN) has been used to model the power generation of different BIPV arrays on a 5 min basis using the meteorological and solar irradiance on-site conditions, as well as the shading patterns estimated from a digital surface model as inputs. The ANN model has been validated using three years of 5-min-basis monitored data showing very high accuracy (6–16% of relative error depending on the façade). The proposed methodology combines the shading computation from a digital surface model with powerful machine learning algorithms for modeling vertical PV arrays under partial shading conditions. The results presented here prove also the capability of the machine learning techniques towards the creation of a digital twin for the specific case of BIPV systems that complements the conventional monitoring strategies and can be used in the diagnosis of performance anomalies. Full article
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Article
Design of a Deflection Switched Reluctance Motor Control System Based on a Flexible Neural Network
Energies 2022, 15(11), 4172; https://doi.org/10.3390/en15114172 - 06 Jun 2022
Viewed by 284
Abstract
Deflection switched reluctance motors (DSRM) are prone to chattering at low speeds, which always affects the output efficiency of the DSRM and the mechanical loss of the motor. Combining the characteristics of a traditional reluctance motor with the strong nonlinear and high coupling [...] Read more.
Deflection switched reluctance motors (DSRM) are prone to chattering at low speeds, which always affects the output efficiency of the DSRM and the mechanical loss of the motor. Combining the characteristics of a traditional reluctance motor with the strong nonlinear and high coupling of the DSRM, a control system for a DSRM based on a flexible neural network (FNN) is proposed in this paper. Based on the better robustness and fault tolerance of fuzzy PI control, the given speed signal is adjusted and converted into a torque control signal. As a result, the FNN control module possesses the strong self-learning ability and adaptive adjustment ability necessary to obtain the control voltage signal. Through simulations and experiments, it was verified that the control system can run stably on DSRM and shows good dynamic performance and anti-interference ability. Full article
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Article
Short-Term PV Power Forecasting Using a Regression-Based Ensemble Method
Energies 2022, 15(11), 4171; https://doi.org/10.3390/en15114171 - 06 Jun 2022
Viewed by 353
Abstract
One of the most critical aspects of integrating renewable energy sources into the smart grid is photovoltaic (PV) power generation forecasting. This ensemble forecasting technique combines several forecasting models to increase the forecasting accuracy of the individual models. This study proposes a regression-based [...] Read more.
One of the most critical aspects of integrating renewable energy sources into the smart grid is photovoltaic (PV) power generation forecasting. This ensemble forecasting technique combines several forecasting models to increase the forecasting accuracy of the individual models. This study proposes a regression-based ensemble method for day-ahead PV power forecasting. The general framework consists of three steps: model training, creating the optimal set of weights, and testing the model. In step 1, a Random forest (RF) with different parameters is used for a single forecasting method. Five RF models (RF1, RF2, RF3, RF4, and RF5) and a support vector machine (SVM) for classification are established. The hyperparameters for the regression-based method involve learners (linear regression (LR) or support vector regression (SVR)), regularization (least absolute shrinkage and selection operator (LASSO) or Ridge), and a penalty coefficient for regularization (λ). Bayesian optimization is performed to find the optimal value of these three hyperparameters based on the minimum function. The optimal set of weights is obtained in step 2 and each set of weights contains five weight coefficients and a bias. In the final step, the weather forecasting data for the target day is used as input for the five RF models and the average daily weather forecasting data is also used as input for the SVM classification model. The SVM output selects the weather conditions, and the corresponding set of weight coefficients from step 2 is combined with the output from each RF model to obtain the final forecasting results. The stacking recurrent neural network (RNN) is used as a benchmark ensemble method for comparison. Historical PV power data for a PV site in Zhangbin Industrial Area, Taiwan, with a 2000 kWp capacity is used to test the methodology. The results for the single best RF model, the stacking RNN, and the proposed method are compared in terms of the mean relative error (MRE), the mean absolute error (MAE), and the coefficient of determination (R2) to verify the proposed method. The results for the MRE show that the proposed method outperforms the best RF method by 20% and the benchmark method by 2%. Full article
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Article
An Assessment Method for the Impact of Electric Vehicle Participation in V2G on the Voltage Quality of the Distribution Network
Energies 2022, 15(11), 4170; https://doi.org/10.3390/en15114170 - 06 Jun 2022
Viewed by 273
Abstract
In order to further evaluate the impact of vehicle-to-grid (V2G) on the distribution network, this paper studies a method to assess the influence of electric vehicles participating in charge and discharge on the voltage quality of the distribution network. First, considering the state [...] Read more.
In order to further evaluate the impact of vehicle-to-grid (V2G) on the distribution network, this paper studies a method to assess the influence of electric vehicles participating in charge and discharge on the voltage quality of the distribution network. First, considering the state of charge of the EV, the participation of the owner and other factors, the charging and discharging model is built. Then, the probabilistic power flow calculation based on Latin hypercube sampling is used to obtain the probability distribution of the voltage amplitude of the charge and discharge load connected to the distribution network, and finally the evaluation index is established to quantify and calculate the voltage quality of the distribution network participating in the V2G process of electric vehicles. Simulation results show that the evaluation method has the advantage of fast calculation speed while ensuring known accuracy, introduces the probability distribution of expected value and variance quantification of voltage amplitude, more intuitively understands the degree of influence on voltage quality before and after V2G, and can effectively assess the impact of electric vehicles accessing the distribution network in V2G mode on the power quality of low-voltage residential areas and industrial and commercial areas, and this evaluation method can provide useful reference for the formulation of future V2G control strategies and the planning of future urban power grids. Full article
(This article belongs to the Section A6: Electric Vehicles)
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Article
Simulation of the Thermal Runaway Onset in Li-Ion Cells—Influence of Cathode Materials and Operating Conditions
Energies 2022, 15(11), 4169; https://doi.org/10.3390/en15114169 - 06 Jun 2022
Viewed by 368
Abstract
Li-ion batteries are already being used in several applications, from portable devices to the automotive industry, and they represent a promising option also for other critical uses, such as in the storage of energy from renewable sources. However, two of the main concerns [...] Read more.
Li-ion batteries are already being used in several applications, from portable devices to the automotive industry, and they represent a promising option also for other critical uses, such as in the storage of energy from renewable sources. However, two of the main concerns that still hinder their massive introduction in these further areas, are their safety and reliability. Depending on cell characteristics and operating conditions, the heat generated within the cell can exceed that dissipated from its surface, and the cell will fail, possibly with catastrophic consequences. To identify the hazardous working conditions of a cell, a simulation model including the main exothermic reactions was set up to investigate the onset of thermal runaway in several Li-ion cell configurations under various operating conditions. The behavior of four different cathodes under thermal abuse and the influence of external factors such as the environmental temperature and the cooling system efficiency were assessed. It was found that among those investigated, the lithium iron phosphate cathode is characterized by a higher thermal stability and that an efficient superficial heat exchange can prevent thermal runaway in most of the cases. Full article
(This article belongs to the Section D2: Electrochem: Batteries, Fuel Cells, Capacitors)
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Review
An Overview on Co-Pyrolysis of Biodegradable and Non-Biodegradable Wastes
Energies 2022, 15(11), 4168; https://doi.org/10.3390/en15114168 - 06 Jun 2022
Viewed by 414
Abstract
Continuous urbanization and modernization have increased the burning of fossil fuels to meet energy needs across the globe, emanating environmental pollution and depleting fossil fuels. Therefore, a shift towards sustainable and renewable energy is necessary. Several techniques to exploit biomass to yield energy [...] Read more.
Continuous urbanization and modernization have increased the burning of fossil fuels to meet energy needs across the globe, emanating environmental pollution and depleting fossil fuels. Therefore, a shift towards sustainable and renewable energy is necessary. Several techniques to exploit biomass to yield energy are trending, with pyrolysis one of them. Usually, a single feedstock is employed in pyrolysis for anoxygenic generation of biochar together with bio-oil at elevated temperatures (350–600 °C). Bio-oil produced through pyrolysis can be upgraded to crude oil after some modification. However, these modifications of bio-oil are one of the major drawbacks for its large-scale adoption, as upgradation increases the overall cost. Therefore, in recent years the scientific community has been researching co-pyrolysis technology that involves the pyrolysis of lignocellulosic biomass waste with non-biodegradable waste. Co-pyrolysis reduces the need for post-modification of bio-oil, unlike pyrolysis of a single feedstock. This review article discusses the recent advancements and technological challenges in waste biomass co-pyrolysis, the mechanism of co-pyrolysis, and factors that affect co-pyrolysis. The current study critically analyzes different recent research articles presented in databases such as PubMed, MDPI, ScienceDirect, Springer, etc. Hence, this review is one-of-a-kind in that it attempts to explain each and every aspect of the co-pyrolysis process and its current progress in the scientific field. Consequently, this review also compiles the remarkable achievements in co-pyrolysis and recommendations for the future. Full article
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Article
Stability Analysis of a Typical Salt Cavern Gas Storage in the Jintan Area of China
Energies 2022, 15(11), 4167; https://doi.org/10.3390/en15114167 - 06 Jun 2022
Viewed by 354
Abstract
Using underground space to store natural gas resources is an important means by which to solve emergency peak shaving of natural gas. Rock salt gas storage is widely recognized due to its high-efficiency peak shaving and environmental protection. Damage and stress concentrations inside [...] Read more.
Using underground space to store natural gas resources is an important means by which to solve emergency peak shaving of natural gas. Rock salt gas storage is widely recognized due to its high-efficiency peak shaving and environmental protection. Damage and stress concentrations inside the cavern injection during withdrawal operations and throughout the storage facility life have always been among the most important safety issues. Therefore, accurate evaluation of the stability of rock salt gas storage during operation is of paramount significance to field management and safety control. In this study, we used the finite element numerical analysis software Flac3D to numerically simulate large displacement deformations of the cavern wall during gas storage—in addition to the distribution of the plastic zone of the rock around the cavern and the surface settlement—under different working conditions. We found that the maximum surface settlement value occurred near the upper part of the cavern. The surface settlement value increased as a function of creep time, but this increase leveled off, that is, a convergence trend was observed. The value was relatively small and, therefore, had little impact on the surface. The application of gas pressure inhibited the growth of the plastic zone, but on the whole, the plastic zone’s range increased proportionally to creep time. For the 20-year creep condition, the deformation value of the cavern’s surrounding rock was large. Combined with the distribution of the plastic zone, we believe that the cavern’s surrounding rock is unstable; thus, corresponding reinforcement measures must be taken. Full article
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Editorial
Special Issue “Industry and Tertiary Sectors towards Clean Energy Transition”
Energies 2022, 15(11), 4166; https://doi.org/10.3390/en15114166 - 06 Jun 2022
Viewed by 266
Abstract
The Special Issue “Industry and Tertiary Sectors towards Clean Energy Transition” is focused on technical, financial and policy-related aspects linked to the transition of industrial and services sectors towards energy saving and decarbonisation. These different aspects are interrelated, and as such, they have [...] Read more.
The Special Issue “Industry and Tertiary Sectors towards Clean Energy Transition” is focused on technical, financial and policy-related aspects linked to the transition of industrial and services sectors towards energy saving and decarbonisation. These different aspects are interrelated, and as such, they have been analysed with an interdisciplinary approach combining economic and technical information. Collecting and analysing quantitative data would allow researchers to better understand the clean energy transition process, and how the international and national regulatory and policy framework are contributing to it. The papers within this Special Issue focus on energy efficiency and clean energy key technologies, renewable sources, energy management and monitoring systems, energy policies and regulations, and economic and financial aspects. Full article
(This article belongs to the Special Issue Industry and Tertiary Sectors towards Clean Energy Transition)
Communication
Experimental Investigation of Gaseous Sodium Release in Slag-Tapping Coal-Fired Furnaces by Spontaneous Emission Spectroscopy
Energies 2022, 15(11), 4165; https://doi.org/10.3390/en15114165 - 06 Jun 2022
Viewed by 277
Abstract
High-alkali coal is rich in alkali metals, which can cause serious effects such as slagging and corrosion on the heating surface during combustion and utilization. A portable spectral system was utilized to simultaneously measure gaseous Na concentration and temperature in a 20 kW [...] Read more.
High-alkali coal is rich in alkali metals, which can cause serious effects such as slagging and corrosion on the heating surface during combustion and utilization. A portable spectral system was utilized to simultaneously measure gaseous Na concentration and temperature in a 20 kW slag-tapping combustor and a slagging boiler furnace of a 300 MW power generation unit by flame spontaneous emission spectroscopy (FES) for simultaneous measuring. The result shows that both ZD-FK and ZD-HSQ (Fukang coal and Hongshaquan coal, Xinjiang Zhundong high-alkali coal) combustion flame temperatures are around 1400 °C at the outlet of the cyclone burner while the latter is slightly higher. The sodium concentration in the gas phase increases with the rising of the initial combustion temperature and unit load for one kind of coal, and the level of sodium concentration has a strong correlation with the Na content for different coal. Most of the sodium in the high temperature zone of the furnace exists in the form of gas phase, and more sodium migrates to fly ash. Combined with the analysis of fly ash and liquid slag samples, a closed-loop analysis of the Na migration path could be established. Full article
(This article belongs to the Special Issue Advanced Research on Clean Energy Combustion Diagnosis)
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Editorial
Situational Awareness for Smart Distribution Systems
Energies 2022, 15(11), 4164; https://doi.org/10.3390/en15114164 - 06 Jun 2022
Viewed by 269
Abstract
In recent years, the accelerating climate change and intensifying natural disasters have called for more renewable, resilient, and reliable energy from more distributed sources to more diversified consumers, resulting in a pressing need for advanced situational awareness of modern smart distribution systems [...] [...] Read more.
In recent years, the accelerating climate change and intensifying natural disasters have called for more renewable, resilient, and reliable energy from more distributed sources to more diversified consumers, resulting in a pressing need for advanced situational awareness of modern smart distribution systems [...] Full article
(This article belongs to the Special Issue Situation Awareness for Smart Distribution Systems)
Article
Adaptive Current Control for Grid-Connected Inverter with Dynamic Recurrent Fuzzy-Neural-Network
Energies 2022, 15(11), 4163; https://doi.org/10.3390/en15114163 - 06 Jun 2022
Viewed by 271
Abstract
The grid-connected inverter is a vital power electronic equipment connecting distributed generation (DG) systems to the utility grid. The quality of the grid-connected current is directly related to the safe and stable operation of the grid-connected system. This study successfully constructed a robust [...] Read more.
The grid-connected inverter is a vital power electronic equipment connecting distributed generation (DG) systems to the utility grid. The quality of the grid-connected current is directly related to the safe and stable operation of the grid-connected system. This study successfully constructed a robust control system for a grid-connected inverter through a dynamic recurrent fuzzy-neural-network imitating sliding-mode control (DRFNNISMC) framework. Firstly, the dynamic model considering system uncertainties of the grid-connected inverter is described for the global integral sliding-mode control (GISMC) design. In order to overcome the chattering phenomena and the dependence of the dynamic information in the GISMC, a model-free dynamic recurrent fuzzy-neural-network (DRFNN) is proposed as a major controller to approximate the GISMC law without the extra compensator. In the DRFNN, a Petri net with varied threshold is incorporated to fire the rules, and only the parameters of the fired rules are adapted to alleviate the computational workload. Moreover, the network is designed with internal recurrent loops to improve the dynamic mapping capability considering the uncertainties in the control system. In addition, to assure the parameter convergence in the adaptation and the stability of the designed control system, the adaptation laws for the parameters of the DRFNN are deduced by the projection theorem and Lyapunov stability theory. Finally, the experimental comparisons with the GISMC scheme are performed in an inverter prototype to verify the superior performance of the proposed DRFNNISMC framework for the grid-connected current control. Full article
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Article
Influence of a New Type of Two-Speed Planetary Gear Automatic Transmission on the Performance of Battery Electric Vehicles
Energies 2022, 15(11), 4162; https://doi.org/10.3390/en15114162 - 06 Jun 2022
Viewed by 333
Abstract
This paper introduces a new two-speed planetary gear automatic transmission using an electronically controlled wedge clutch. In order to verify the feasibility of using this transmission in pure electric vehicles, the influencing factors of the two-speed transmission due to the increase in mass [...] Read more.
This paper introduces a new two-speed planetary gear automatic transmission using an electronically controlled wedge clutch. In order to verify the feasibility of using this transmission in pure electric vehicles, the influencing factors of the two-speed transmission due to the increase in mass and the reduction in transmission efficiency are introduced. The vehicle simulation model was established on the MATLAB/Simulink platform, and the dynamic programming method was used to optimize the transmission ratio and shifting law. The simulation results show that the use of a two-speed automatic transmission can effectively improve the economic performance and dynamic performance of battery electric vehicles. Full article
(This article belongs to the Section A6: Electric Vehicles)
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Article
Study of Key Technology of Gob-Side Entry Retention in a High Gas Outburst Coal Seam in the Karst Mountain Area
Energies 2022, 15(11), 4161; https://doi.org/10.3390/en15114161 - 06 Jun 2022
Viewed by 276
Abstract
In the gob-side entry retaining by roof cutting (GERRC) technique, pressure is offloaded via directional roof cutting, and a roadway is automatically formed due to the ground pressure and rock-breaking expansion. To improve the application of the theory and technical system of GERRC [...] Read more.
In the gob-side entry retaining by roof cutting (GERRC) technique, pressure is offloaded via directional roof cutting, and a roadway is automatically formed due to the ground pressure and rock-breaking expansion. To improve the application of the theory and technical system of GERRC in the Karst area in Southwest China, this research studies the key technology of GERRC in a high gas outburst coal seam, based on the engineering background of the 39114 working face of the Honglin coal mine. According to the geological conditions of the 39114 working face, by means of formula calculation, UDEC numerical modeling, and on-site drilling peeping, the optimal roof-cutting parameters suitable for the 39114 working face were determined: the roof cutting height was 7 m, the roof cutting angle was 15°, and the spacing of pre-splitting blasting holes was 600 mm. Additionally, the above roof-cutting parameters have achieved good results in the engineering practices of the 39114 transportation roadway, which shows that the technology of GERRC is feasible in high gas outburst mines and achieves the goal of safe and efficient mining. Full article
(This article belongs to the Topic Mining Safety and Sustainability)
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Article
Energy Consumption Estimation for Electric Buses Based on a Physical and Data-Driven Fusion Model
Energies 2022, 15(11), 4160; https://doi.org/10.3390/en15114160 - 06 Jun 2022
Viewed by 309
Abstract
The energy consumption of electric vehicles is closely related to the problems of charging station planning and vehicle route optimization. However, due to various factors, such as vehicle performance, driving habits and environmental conditions, it is difficult to estimate vehicle energy consumption accurately. [...] Read more.
The energy consumption of electric vehicles is closely related to the problems of charging station planning and vehicle route optimization. However, due to various factors, such as vehicle performance, driving habits and environmental conditions, it is difficult to estimate vehicle energy consumption accurately. In this work, a physical and data-driven fusion model was designed for electric bus energy consumption estimation. The basic energy consumption of the electric bus was modeled by a simplified physical model. The effects of rolling drag, brake consumption and air-conditioning consumption are considered in the model. Taking into account the fluctuation in energy consumption caused by multiple factors, a CatBoost decision tree model was constructed. Finally, a fusion model was built. Based on the analysis of electric bus data on the big data platform, the performance of the energy consumption model was verified. The results show that the model has high accuracy with an average relative error of 6.1%. The fusion model provides a powerful tool for the optimization of the energy consumption of electric buses, vehicle scheduling and the rational layout of charging facilities. Full article
(This article belongs to the Topic Energy Storage and Conversion Systems)
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Article
Model for Optimal Power Coefficient Tracking and Loss Reduction of the Wind Turbine Systems
Energies 2022, 15(11), 4159; https://doi.org/10.3390/en15114159 - 06 Jun 2022
Viewed by 464
Abstract
This research aimed to introduce a comprehensive mathematical modeling approach based on the maximization of the power coefficient (Cp) to obtain the regulation in pitch angle and tip speed ratio (TSP), taking into account the detailed power losses at the different stages of [...] Read more.
This research aimed to introduce a comprehensive mathematical modeling approach based on the maximization of the power coefficient (Cp) to obtain the regulation in pitch angle and tip speed ratio (TSP), taking into account the detailed power losses at the different stages of the power train of the wind turbine. The model is used to track the optimal power coefficient of the wind turbine power train, considering both direct (without gearbox) and indirect (with gearbox) drive configurations. The result of the direct driveline was validated with a 100 W horizontal-axis wind turbine experimental system. The model estimated the optimal value of Cp at 0.48 for a pitch angle of 0 degrees and a TSR of 8.1, which could be obtained at a wind speed of around 11.2 m/s. The results also revealed that, within the lower wind regime, windage, hysteresis, and eddy current losses dominated, while during higher wind regimes, the copper, stray load, and insulator gate bipolar transistor (IGBT) losses gained high values. The developed model was applied to a 20 kW indirect drive wind turbine installed in Gwadar city in Pakistan. Compared with the direct coupling, the optimal value of Cp was obtained at a higher value of the pitch angle (1.7 degrees) and a lower value of TSR (around 6) due to the significant impact of the gear and copper losses in an indirect drivetrain. Full article
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Article
Line Loss Interval Algorithm for Distribution Network with DG Based on Linear Optimization under Abnormal or Missing Measurement Data
Energies 2022, 15(11), 4158; https://doi.org/10.3390/en15114158 - 06 Jun 2022
Viewed by 353
Abstract
Data collection is more difficult in distribution network than transmission networks since the structure of distribution networks is more complex. As a result, data could be partly abnormal or missing, which cannot completely describe the operation status of distribution network. In addition, access [...] Read more.
Data collection is more difficult in distribution network than transmission networks since the structure of distribution networks is more complex. As a result, data could be partly abnormal or missing, which cannot completely describe the operation status of distribution network. In addition, access of distributed generation (DG) to distribution network further aggravates the variability of power flow in distribution network. The traditional deterministic line loss calculation method has some limitations in accurately estimating the line loss of distribution network with DG. A line loss interval calculation method based on power flow calculation and linear optimization is proposed, considering abnormal data collection and distribution network power flow variability. The linear optimization model is established according to sensitivity of line loss to the injected power and sensitivity of transmission power of first branch to the injected power. Introducing the scheduling information into the optimization model, a reliable line loss fluctuation interval can be obtained which actual line loss locates. The effectiveness of the proposed algorithm is verified in IEEE 33-bus distribution network system. Full article
(This article belongs to the Special Issue Optimal Operation and Control of Energy System and Power System)
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Article
Influence of Growing Miscanthus x giganteus on Ecosystem Services of Chernozem
Energies 2022, 15(11), 4157; https://doi.org/10.3390/en15114157 - 06 Jun 2022
Viewed by 354
Abstract
The paper investigates the optimization of ecosystem services of podzolized heavy loamy chernozem (black soil) as a result of the cultivation of the perennial energy culture of Miscanthus x giganteus. The research was conducted on an experimental land plot during 2016–2021. No [...] Read more.
The paper investigates the optimization of ecosystem services of podzolized heavy loamy chernozem (black soil) as a result of the cultivation of the perennial energy culture of Miscanthus x giganteus. The research was conducted on an experimental land plot during 2016–2021. No fertilization was applied to the soil during the experiments, and over the years of research, the growing seasons were accompanied by abnormal droughts, but even under such conditions, the plants of Miscanthus x giganteus gradually increased their yield. At the initial stage of research, in the third year of cultivation, dry biomass of Miscanthus x giganteus was obtained at 14.3 t/ha, in the fourth year–18.6 t/ha, and already in the fifth and sixth years, 21.7 and 24.5 t/ha, respectively. That is, energy-wise, the harvest for the last year was equivalent to 15.9 tons of coal or 12,618 m3 of natural gas. Cultivation of Miscanthus x giganteus on black soil for six years has improved the provision of its ecosystem services, regulation, and ecosystem maintenance services. The possibility of growing perennial energy crops on agricultural soils has been proven by obtaining a significant amount of biomass and a positive phytoremediation effect on the soil by reducing erosion, preserving biodiversity, sequestering carbon, and sustainably improving the ecological situation. Full article
(This article belongs to the Special Issue Energy Sources from Agriculture and Rural Areas)
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Article
Cooling Thermal Comfort and Efficiency Parameters of Ceiling Panels, Underfloor Cooling, Fan-Assisted Radiators, and Fan Coil
Energies 2022, 15(11), 4156; https://doi.org/10.3390/en15114156 - 05 Jun 2022
Viewed by 408
Abstract
Climate change has brought a compelling need for cooling living spaces to the attention of researchers as well as construction professionals. The problem of overheating enclosures is now exacerbated in traditionally affected areas and is also affecting countries that were previously less prone [...] Read more.
Climate change has brought a compelling need for cooling living spaces to the attention of researchers as well as construction professionals. The problem of overheating enclosures is now exacerbated in traditionally affected areas and is also affecting countries that were previously less prone to the issue. In this paper, we address measurements of thermal comfort and cooling emission efficiency parameters for different devices: ceiling panels, underfloor cooling, fan-assisted radiators, and fan coil. These devices were tested in low and high cooling capacities of up to 40 W/m2 while also featuring heating dummies to imitate internal heat gains. Air temperatures were measured at different heights, allowing to evaluate the thermal stratification with high accuracy. Thermal comfort differences of the tested systems were quantified by measuring both air velocities and operative temperatures at points of occupancy. In summary, the best-performing cooling devices for the studied cooling applications were the ceiling panels and fan radiators, followed by underfloor cooling, with a limitation of stratification. Because of the strong jet, fan coil units did not achieve thermal comfort within the whole occupied zone. The results can be utilized in future studies for cooling emission efficiency and energy consumption analyses of the different cooling devices. Full article
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Article
The Role of Resource Consumption Accounting in Achieving Competitive Prices and Sustainable Profitability
Energies 2022, 15(11), 4155; https://doi.org/10.3390/en15114155 - 05 Jun 2022
Viewed by 462
Abstract
This study examines the roles of resource consumption accounting and competitive prices in attaining sustainable profitability. The objectives were (1) to determine whether the adoption of resource consumption accounting practices yields significant improvements in competitive strategies in a highly competitive situation where activity-based [...] Read more.
This study examines the roles of resource consumption accounting and competitive prices in attaining sustainable profitability. The objectives were (1) to determine whether the adoption of resource consumption accounting practices yields significant improvements in competitive strategies in a highly competitive situation where activity-based costing has proved to be insignificant, and (2) to ascertain if the positive relationship between competitive pricing and sustainable profitability is increased by the extent to which resource consumption accounting exerts pressure for sustainability profitability. A PLS-SEM procedure was applied in analysing 129 of the top 30 performing companies’ structured questionnaire responses drawn from five industries in Kurdistan from 2021. The empirical results demonstrated that competitive pricing models involving resource consumption accounting systems provide superior price forecasting, error reduction and profit maximisation capabilities than existing energy models. The study’s outcomes highlight that the extent to which resource consumption accounting exerts pressure on sustainability profitability significantly increases the positive relationship between competitive pricing and sustainable profitability. The results of this study advance construct and item development involving competitive pricing and resource consumption accounting while testing relationships to uncover the moderating role of resource consumption accounting in profit maximisation. Thus, energy and non-energy industrial companies must rely on resource consumption accounting to set competitive prices and enhance and sustain their profitability by considering the overlooked energy pricing stochastic parameters and errors amid rising energy shortages and costs. Full article
(This article belongs to the Special Issue Sustainable Development: Policies, Challenges, and Further)
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Article
Modeling and Analysis of the Flow Characteristics of Liquid Hydrogen in a Pipe Suffering from External Transient Impact
Energies 2022, 15(11), 4154; https://doi.org/10.3390/en15114154 - 05 Jun 2022
Viewed by 380
Abstract
Pipes can be subjected to external transient impacts such as accidental collision, which affects the safe operation of storage and transportation systems for liquid hydrogen. Fluid–structure coupling calculation for a pipe under external transient impact is performed, and the flow characteristics of liquid [...] Read more.
Pipes can be subjected to external transient impacts such as accidental collision, which affects the safe operation of storage and transportation systems for liquid hydrogen. Fluid–structure coupling calculation for a pipe under external transient impact is performed, and the flow characteristics of liquid hydrogen in the pipe are analyzed. The pipe deforms and vibrates when suffering from external transient impact. Liquid hydrogen pressure in a cross-section plane increases along the pipe deformation direction. Additionally, external transient impact enhances the disturbance of liquid hydrogen near the pipe wall. The increased flow resistance and the energy induced by the deformed pipe both affect the flow of liquid hydrogen, and contribute to the fluctuated characteristics of liquid pressure drop. In addition, the phase state of liquid hydrogen remains unchanged in the pipe, indicating that little of the induced energy is transformed into the internal energy of liquid hydrogen. The work provides theoretical guidance for the safe operation of liquid hydrogen storage and transportation systems. Full article
(This article belongs to the Special Issue Computational Fluid Dynamics Applied to Hydrogen Safety)
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Article
Effects of Different Exhaust Gas Recirculation (EGR) Rates on Combustion and Emission Characteristics of Biodiesel–Diesel Blended Fuel Based on an Improved Chemical Mechanism
Energies 2022, 15(11), 4153; https://doi.org/10.3390/en15114153 - 05 Jun 2022
Viewed by 370
Abstract
This paper studies the effects of different exhaust gas recirculation (EGR) rates (0%, 5%, 10%, and 15%) on the combustion, performance, and emission characteristics of a biodiesel–diesel (20% biodiesel + 80% diesel) blended fuel engine. This paper mainly analyzes the effects on engine [...] Read more.
This paper studies the effects of different exhaust gas recirculation (EGR) rates (0%, 5%, 10%, and 15%) on the combustion, performance, and emission characteristics of a biodiesel–diesel (20% biodiesel + 80% diesel) blended fuel engine. This paper mainly analyzes the effects on engine cylinder temperature, cylinder pressure, brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), NOx emissions, carbon monoxide (CO) emissions, hydrocarbon (HC) emissions, and soot emissions. Firstly, a 3D-CFD model was established by using CONVERGE software, combined with an improved chemical kinetic mechanism including 98 species and 314 reactions, and the accuracy of the simulation model was verified by experimental results. Secondly, the effects of different EGR rates on the combustion, performance, and emission characteristics of biodiesel–diesel blended fuel were studied. The results showed that with the increase in the EGR rate, the cylinder pressure and cylinder temperature in the cylinder decreased. When the EGR rate was 15%, the maximum cylinder temperature decreased by 4.33%. In addition, BSFC increased and BTE decreased. Moreover, with the increase in the EGR rate, NOx decreased significantly, and the higher the EGR rate, the more obvious the reduction in NOx emissions. When the EGR rate was 15%, NOx was reduced by 78.89%. However, with the increase in the EGR rate, the emissions of soot, HC, and CO increased. The optimal EGR rate for the engine is 10%. Full article
(This article belongs to the Special Issue Controlling of Combustion Process in Energy and Power Systems)
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Article
Experimental Study of Power Generation and COD Removal Efficiency by Air Cathode Microbial Fuel Cell Using Shewanella baltica 20
Energies 2022, 15(11), 4152; https://doi.org/10.3390/en15114152 - 05 Jun 2022
Viewed by 324
Abstract
Microbial fuel cells (MFCs) are a kind of bioreactor for generating electricity, facilitated by exoelectrogens while treating wastewater. The present article focuses on the performance of an air cathode plexiglass MFC in terms of chemical oxygen demand (COD) removal efficiency and power output [...] Read more.
Microbial fuel cells (MFCs) are a kind of bioreactor for generating electricity, facilitated by exoelectrogens while treating wastewater. The present article focuses on the performance of an air cathode plexiglass MFC in terms of chemical oxygen demand (COD) removal efficiency and power output by performing two sets of experiments. The proton exchange membrane and electrode materials were Nafion 117 and carbon felts, whereas, for stable biofilm formation on the anode surface, a pure culture of Shewanella baltica 20 was used. Firstly, sterile Luria-Bertani (LB) media containing lactate, ranging from 20 to 100 mM, was continuously fed to an MFC, and a maximum power density of 55 mW/m2 was observed. Similarly, artificial wastewater with COD ranging from 3250 mg/L to 10,272 mg/L was supplied to the MFC in the second set of experiments. In this case, the maximum power density and COD removal efficiency were 12 mW/m2 and 57%, respectively. In both cases, the hydraulic retention time (HRT) was 1.5 h. It was found that electricity generation depends on the characteristics of the wastewater. These initial findings confirm that the design aspects of an MFC, i.e., surface area to volume ratio, and external resistance with respect to the quality of influent need to be optimised to improve the MFC’s performance. Full article
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Article
Grid-Connected Power Converters: An Overview of Control Strategies for Renewable Energy
Energies 2022, 15(11), 4151; https://doi.org/10.3390/en15114151 - 05 Jun 2022
Viewed by 447
Abstract
The move towards a greener energy mix to fight climate change propels investments in converter-interfaced resources such as wind and photovoltaics, energy storage systems and electric vehicles. The ongoing evolution of the power system is occurring at a very fast pace, challenging transmission [...] Read more.
The move towards a greener energy mix to fight climate change propels investments in converter-interfaced resources such as wind and photovoltaics, energy storage systems and electric vehicles. The ongoing evolution of the power system is occurring at a very fast pace, challenging transmission and distribution system operators to seek solutions that are not only adequate for this moment but also for future scenarios. Ongoing research in the fields of power electronics, power systems and control aims at developing control strategies that will help the energy transition to occur, while keeping a stable, secure and reliable power system. The objective of this paper is to present a critical review of the control strategies developed for grid-connected power converters found in renewable energy systems, energy storage systems and electric vehicles. The impact of grid-connected converters on the stability of power grids is also reviewed, highlighting the promising control strategies for enhancing system stability. Full article
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Article
Performance Evaluation of PVT Air Collector Coupled with a Triangular Block in Actual Climate Conditions in Korea
Energies 2022, 15(11), 4150; https://doi.org/10.3390/en15114150 - 05 Jun 2022
Viewed by 311
Abstract
This study experimentally investigated the performance of a PVT air collector coupled with a triangular block. The triangular block, newly suggested by the authors, is a triangular-shaped obstacle and was inserted at the bottom of the PVT air collector to enhance the heat [...] Read more.
This study experimentally investigated the performance of a PVT air collector coupled with a triangular block. The triangular block, newly suggested by the authors, is a triangular-shaped obstacle and was inserted at the bottom of the PVT air collector to enhance the heat transfer performance of the collector. The experiment was carried out in actual climate conditions in Korea with two air mass flow rate conditions: 0.03606 kg/m2 s and 0.06948 kg/m2 s. Results show the average values of electrical efficiency of the collector during the test period to be 16.15% and 16.43% for each air mass flow rate, while thermal efficiencies were 28.83% and 38.36%, respectively. The average values of total energy efficiencies were found to be 44.99% and 54.79%, respectively. The results show that air mass flow rate has a large impact on thermal and total energy efficiency, while it has a small impact on electrical efficiency. Furthermore, it was confirmed that the PVT air collector coupled with a triangular block can enhance the utilization of solar energy since the thermal performance was higher than that of the collector without a triangular block. Full article
(This article belongs to the Topic Solar Thermal Energy and Photovoltaic Systems)
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