In this study, an asymmetric supercapacitor (ASSC) device is assembled by the deposition and annealing of silver-doped mixed metal oxides on reduced graphene oxide (rGO)/Ni foam and activated carbon (AC) on Ni foam as positive and negative electrodes, respectively. The best performing Ag:MnCoNiO active material is synthesized on rGO/Ni foam using chronopotentiometry combined with heat treatment. The XRD study clearly confirms the crystalline nature of the electrode with MnCo2O4 and MnNi2O4 phases. FT-IR and XPS studies revealed the formation of Ag:MnCoNiO/rGO on Ni foam. SEM images show a thin-film layer of fabricated material on the surface of rGO/Ni foam. The supercapacitor properties were tested in two- and three-electrode configurations, with cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) experiments in a 6 M KOH aqueous electrolyte. In the three-electrode configuration, reversible faradic reactions can be observed in... [more]

The market share of electric vehicles (EVs) has grown exponentially in recent years to reduce air pollution and greenhouse gas emissions. The principal part of an EV is the energy storage system, which is usually the batteries. Thus, the accurate estimation of the remaining useful life (RUL) of the batteries, for an optimal health management and a decision-making policy, still remains a challenge for automakers. In this paper, the problem of battery RUL prediction is studied from a new perspective. Unlike other estimation strategies existing in the literature, the proposed technique uses an intelligent prediction of the lifespan of lithium−iron−phosphate (LFP) batteries via a modified version of neural networks. It uses a data-driven life estimation approach and optimization method and does not require any prior comprehension and initialization of any parameters of the battery model. To validate and verify the proposed technique, we use LFP battery data sets, and the experimental resul... [more]

Field operations report that at least half of the fracturing fluid used in shale reservoirs is trapped. These trapped fluids can trigger various geochemical interactions. However, the impact of these interactions on well performance is still elusive. We modeled a hydraulic fracture stage where we simulated the initial conditions by injecting the fracturing fluid and shutting the well to allow the fluids to soak into the formation. Our results suggest a positive correlation between the dissolution and precipitation rates and the carbonate content of the rock. In addition, we observed that gas and load recovery are overestimated when geochemical interactions are overlooked. We also observed promising results for sea water as a good alternative fracturing fluid. Moreover, we observed better performance for cases with lower-saline connate water. The reactions of carbonates outweigh the reactions of clays in most cases. Sensitivity analysis suggests that the concentration of SO4, K and Na i... [more]

The performance of a perovskite-based oxygen carrier for the partial oxidation of methane in thermochemical energy storage applications has been investigated. A synthetic perovskite with formula La0.6Sr0.4FeO3 has been scrutinized for Chemical Looping Reforming (CLR) of CH4 under fixed-bed and fluidized-bed conditions. Temperature-programmed reduction and oxidation steps were carried out under fixed-bed conditions, together with isothermal reduction/oxidation cycles, to evaluate long-term perovskite performance. Under fluidized-bed conditions, isothermal reduction/oxidation cycles were carried out as well. Results obtained under fixed-bed and fluidized-bed conditions were compared in terms of oxygen carrier reactivity and stability. The oxygen carrier showed good reactivity and stability in the range 800−1000 °C. An overall yield of 0.6 Nm3 of syngas per kg of perovskite can be reached per cycle. The decomposition of CH4 catalyzed by the reduced oxide can also occur during the reductio... [more]

District heating systems (DHS) are driven by the heat demands of their consumers, with higher demands giving a higher load on the heat production. While heat demands are human-dependent, they contain diurnal behaviors and weather dependencies. The diurnal behaviors contain periods with high demands causing peak loads on the heat production, which is operationally costly. This is especially true for heat pumps, a solution for DHS to include green energy, as the cost depends directly on the needed temperature. This paper presents a formulation of adaptive model predictive control (MPC) for inducing peak shaving on the production load to handle the peak load problem by using the DHS distribution network as a heat storage. It also presents a simulator model to describe the DHS. The MPC was applied to data from a case study of the DHS in Brønderslev, Denmark, showing a peak reduction of around 8%.

Study of the literature and personal research experience have resulted in the identification of many challenges in the field of energy poverty, both in terms of social and technical dimensions. The research problems indicated in the paper and the proposed topics for further methodological and analytical work appear to be important not only from the perspective of the categories of energy poverty but also in the contexts of climate change, the ongoing energy transformation and attempts to implement a new energy model based to a large degree on unconventional and renewable sources of energy. This article also contains both methodological and scientific considerations.

Leading edge erosion (LEE) of wind turbine blades causes decreased aerodynamic performance leading to lower power production and revenue and increased operations and maintenance costs. LEE is caused primarily by materials stresses when hydrometeors (rain and hail) impact on rotating blades. The kinetic energy transferred by these impacts is a function of the precipitation intensity, droplet size distributions (DSD), hydrometeor phase and the wind turbine rotational speed which in turn depends on the wind speed at hub-height. Hence, there is a need to better understand the hydrometeor properties and the joint probability distributions of precipitation and wind speeds at prospective and operating wind farms in order to quantify the potential for LEE and the financial efficacy of LEE mitigation measures. However, there are relatively few observational datasets of hydrometeor DSD available for such locations. Here, we analyze six observational datasets from spatially dispersed locations an... [more]

Natural gum derived from the natural surrounding (gum arabic, guar gum, xanthan gum, gellan gum, fenugreek gum, karaya gum, and acacia gum) is one of the most abundant polysaccharides currently present around the world. As natural gum dissolved solution can be very sticky in nature, its role as a binder for both anodes and cathodes in rechargeable batteries have been recently significantly researched. Although much research has been delved into using natural gum as a feasible binder for rechargeable batteries, little investigation so far has taken place to compile, summarize, analyze, and evaluate the current status-quo of the natural gum-based binder research, as well as understanding some of the obstacles and issues that may need to be addressed. This review gives a comprehensive review on the natural gum-based binder that was used for both anode and cathode in rechargeable batteries and how each kind of natural gum improved the electrochemical performance in terms of cycle retention... [more]

As an important form of distributed renewable energy utilization and consumption, the multi-parallel inverter microgrid system works in both an isolated and grid-connected operation mode. Secondary-frequency and voltage-regulation control are very important in solving problems that appears in these systems, such as the distributed secondary-frequency regulation real-time scheme, voltage and reactive power balancing, and the secondary-frequency regulation control under the disturbances and unbalanced conditions of a microgrid system. This paper introduces key technologies related to these issues, such as the consensus algorithm and event-triggered technique, the dynamic and adaptive virtual impedance technique, and the robust and self-anti-disturbance control technique. Research and design methods such as small-signal state-space analysis, the Lyapunov function design method, the impedance analysis method, μ-synthesis design, and the LMI matrix design method are adopted to solve the iss... [more]

Gas hydrate blockage is a major issue that the production and transportation processes in the oil/gas industry faces. The formation of gas hydrates in pipelines results in significant financial losses and serious safety risks. To tackle the flow assurance issues caused by gas hydrate formation in the pipelines, some physical methods and chemical inhibitors are applied by the oil/gas industry. The physical techniques involve subjecting the gas hydrates to thermal heating and depressurization. The alternative method, on the other hand, relies on injecting chemical inhibitors into the pipelines, which affects gas hydrate formation. Chemical inhibitors are classified into high dosage hydrate inhibitors (thermodynamic hydrate inhibitors (THI)) and low dosage hydrate inhibitors (kinetic hydrate inhibitors (KHI) and anti-agglomerates (AAs)). Each chemical inhibitor affects the gas hydrate from a different perspective. The use of physical techniques (thermal heating and depressurization) to in... [more]

In this work, the application of a feed-forward artificial neural network (FFANN) in predicting the degree of polymerization (DP) and loss of life (LOL) in oil-submerged transformers by using the solid insulation evaluation method is presented. The solid insulation evaluation method is a reliable technique to assess and predict the DP and LOL as it furnishes bountiful information in examining the transformer condition. Herein, two FFANN models are proposed. The first model is based on predicting the DP when only the 2-Furaldehyde (2FAL) concentration measured from oil samples is available for new and existing transformers. The second FFANN model proposed is based on predicting the transformer LOL when the 2FAL and DP are available to the utility owner, typically for the transformer operating at a site where un-tanking the unit is a daunting and unfeasible task. The development encompasses constructing numerous FFANN designs and picking networks with superlative performance. The trainin... [more]

Long electromagnetic transients occur in electrical systems because of switching and impulse actions As a result, the simulation time of such processes can be long, which is undesirable. Simulation time is significantly increased if the circuit in the study is complex, and also if this circuit is described by a rigid system of state equations. Modern requests of design engineers require an increase in the speed of calculations for realizing a real-time simulation. This work is devoted to the development of a unified spectral method for calculating electromagnetic transients in electrical circuits based on the representation of solution functions by series in algebraic and orthogonal polynomials. The purpose of the work is to offer electrical engineers a method that can significantly reduce the time for modeling transients in electrical circuits. Research methods. Approximation of functions by orthogonal polynomials, numerical methods for integrating differential equations, matrix metho... [more]

A global modeling method is developed to describe the relationship between multi-type parameters and fuel cell performance, which significantly contributes to the efficient performance prediction of fuel cell systems. The multi-type parameters include operating parameters, geometric parameters of the graphite end plates, and the membrane electrolyte assembly physical parameters. An adaptive sampling method integrated with the Kriging method is newly developed for global modeling. Experiments are designed and implemented for model construction and evaluation. The results show the local development and global development in the whole design space can be balanced during the adaptive sampling process. Meanwhile, the prediction capability of accuracy and sensitivity for the global model is reliable in the whole design space. The prediction accuracy is improved by nearly 26% compared to the fuel cell model built for optimization with the same sample size. The prediction sensitivity also prov... [more]

As one of the most promising thermal management solutions, spray cooling has the advantages of high heat-transfer coefficient and maintaining a low temperature of the cooling surface. By summarizing the influential factors and practical applications of spray cooling, the current challenges and bottlenecks were indicated so as to prompt its potential applications in the future. Firstly, this paper reviewed the heat-transfer mechanism of spray cooling and found that spray cooling is more advantageous for heat dissipation in high-power electronic devices by comparing it with other cooling techniques. Secondly, the latest experimental studies on spray cooling were reviewed in detail, especially the effects of spray parameters, types of working fluid, surface modification, and environmental parameters on the performance of cooling system. Afterwards, the configuration and design of the spray cooling system, as well as its applications in the actual industry (data centers, hybrid electric ve... [more]

Drying is an extremely energy-intensive process. Superheated steam as a drying medium can improve the energy efficiency of the drying processes. In superheated steam drying, waste heat can be recovered by condensing the exhaust steam or raising its specific enthalpy. Spray drying is widely used in industry, even though its energy efficiency is often low. Substitution of air by superheated steam as a drying medium in a spray dryer may reduce the energy consumption of the drying process by 20−30%; moreover, if excess steam generated by moisture evaporation is upgraded to a higher temperature level and reused for drying, the energy demand could be decreased by even 80%. A literature review showed that superheated steam spray drying was successfully applied for both thermally resistant and a wide range of thermally sensitive materials. Superheated steam drying gives a number of advantages in terms of product properties, i.e., higher particle porosity due to rapid moisture evaporation resul... [more]

In an electric vehicle (EV), using more than one energy source often provides a safe ride without concerns about range. EVs are powered by photovoltaic (PV), battery, and ultracapacitor (UC) systems. The overall results of this arrangement are an increase in travel distance; a reduction in battery size; improved reaction, especially under overload; and an extension of battery life. Improved results allow the energy to be used efficiently, provide a comfortable ride, and require fewer energy sources. In this research, energy management between the PV system and the hybrid energy storage system (HESS), including the battery, and UC are discussed. The energy management control algorithms called Artificial Neural Network (ANN) and Aquila Optimizer Algorithm (AOA) are proposed. The proposed combined ANN−AOA approach takes full advantage of UC while limiting the battery discharge current, since it also mitigates high-speed dynamic battery charging and discharging currents. The responses’ beh... [more]

Spark-ignited natural gas engines have received increasing attention in the heavy-duty market due to their low cost and reliability advantages. However, there are still some issues with natural gas engines retrofitted from 10 to 15 L diesel engines, which is a valuable medium-term goal for the automotive industry. In this work, the effect of intake port structure on the performance of a spark-ignited heavy-duty natural gas engine was investigated by multidimensional numerical simulations. A newly designed intake port was proposed, with strengthened in-cylinder turbulent kinetic energy and homogeneous air-fuel mixtures. Bench tests show that the proposed intake port has impressive thermal efficiency, cycle variation, and acceptable emissions performance. The effective thermal efficiency improves from 41.0% to 41.4%, and the cycle variation is 36% lower than traditional schemes. However, with the accelerated flame propagation, the in-cylinder temperature and NOx emission of the mixed-flo... [more]

The thermal management system of batteries plays a significant role in the operation of electric vehicles (EVs). The purpose of this study is to survey various parameters enhancing the performance of a heat pipe-based battery thermal management system (HP-BTMS) for cooling the lithium-ion batteries (LIBs), including the ambient temperature, coolant temperature, coolant flow rate, heat generation rate, start-up time, inclination angle of the heat pipe, and length of the condenser/evaporator section. This review provides knowledge on the HP-BTMS that can guarantee achievement of the optimum performance of an EV LIB at a high charge/discharge rate.

Reliable energy consumption forecasting is essential for building energy efficiency improvement. Regression models are simple and effective for data analysis, but their practical applications are limited by the low prediction accuracy under ever-changing building operation conditions. To address this challenge, a Joinpoint−Multiple Linear Regression (JP−MLR) model is proposed in this study, based on the investigation of the daily electricity usage data of 8 apartment complexes located within a university in Xiamen, China. The univariate model is first built using the Joinpoint Regression (JPR) method, and then the remaining residuals are evaluated using the Multiple Linear Regression (MLR) method. The model contains six explanatory variables, three of which are continuous (mean outdoor air temperature, mean relative humidity, and temperature amplitude) and three of which are categorical (gender, holiday index, and sunny day index). The performance of the JP−MLR model is compared to tha... [more]

Different control strategies for microgrid applications have been developed in the last decade. In order to enhance flexibility, scalability and reliability, special attention has been given to control organisations based on distributed communication infrastructures. Among these strategies, the implementation of consensus protocol stands out to cooperatively steer multi-agent systems (i.e., distributed generators), which is justified by its benefits, such as plug and play capability and enhanced resilience against communication failures. However, as the consensus protocol has a long trajectory of development in different areas of knowledge including multidisciplinary subjects, it may be a challenge to collect all the relevant information for its application in an emerging field. Therefore, the main goal of this paper is to provide the fundamentals of multi-agent systems and consensus protocol to the electrical engineering community, and an overview of its application to control systems... [more]

This work investigates the thermal−physical and rheological properties of hexagonal boron nitride/carbon nanotubes (hBN/CNTs) applied to reinforce water-based working fluid in a flat plate solar collector (FPSC). The hybrid nanoadditives of hBN and the chemically functionalized CNTs (CF-CNTs) were suspended in distilled water (DW) with a nonionic surfactant. The hybridization ratio between CF-CNTs and hBN was optimized to be 40:60. The thermal efficiency tests on the solar collector were carried out using different volumetric flow rates (2, 3, and 4 L/min) under the ASHRAE-93-2010 standard. The morphological characteristics of the hybrid nanoadditives were evaluated using X-ray diffraction (XRD), ultraviolet−visible spectroscopy (UV−vis), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Different concentrations of hBN/CF-CNTs were added to the water-based working fluid to record the optimal wt.% for maximum enhancement in the FPSC’s effic... [more]

This paper proposes a Data-Driven (DD) framework for the real-time monitoring, detection, and mitigation of False Data Injection (FDI) attacks in DC Microgrids (DCMGs). A supervised algorithm is adopted in this framework to continuously estimate the output voltage and current for all Distributed Generators (DGs) with acceptable accuracy. Accordingly, among the various evaluated supervised DD algorithms, Adaptive Neuro-Fuzzy Inference Systems (ANFISs) are utilized because of their low computational burden, efficiency in operation, and simplicity in design and implementation in a distributed control system. The proposed framework is based on the residual analysis of the generated error signal between the estimated and actual sensed signals. The proposed framework detects and mitigates the cyber-attack depending on trends in generated error signals. Moreover, by applying Online Change Point Detection (OCPD), the need for a static user-defined threshold for the residual analysis of the gen... [more]

The paper presents an innovated method for territorial zoning and its implementation in the territory of the Zdíkovský stream catchment area. The basis for projecting is ananthropo-ecological approach to the territory and the proposition of determining the new GES (geo-ecological units). Four essential territorial zones differing by anthropo-ecological burden and the degree of protection are suggested. A procedure for determining ecocritical lines (situations) in the territory, their regime, and possible solutions is suggested in the spirit of sustainability for future generations. The formulae and procedure for calculating the CES (coefficient of ecological stability) or ZSES (essential degrees of ecological stability), which divide the tested territory into appropriate zones, are also suggested. A comparison of zoning prior to 1989 and following was carried out, and it was proven that the significant presence of agricultural and forest subsystems in the territory with the extensive f... [more]

A record amount of renewable energy has been added to global electricity generation in recent years. Among the renewable energy sources, solar photovoltaic (PV) is the most popular energy source integrated into low voltage distribution networks. However, the voltage limits and current-carrying capacity of the conductors become a barrier to maximizing the PV-hosting capacity in low voltage distribution networks. This paper presents an optimization approach to maximize the PV-hosting capacity in order to fully utilize the existing low voltage distribution network assets. To achieve the maximum PV-hosting capacity of the network, a novel method based on the dynamic line rating of the low voltage distribution network, the coordinated operation of voltage control methods and the PV re-phasing technique was introduced and validated using a case study. The results show that the proposed methodology can enhance the PV-hosting capacity by 53.5% when compared to existing practices.

The Tanshan area is located in the southern section of the west margin of the Ordos basin. The Middle Jurassic Yan’an Formation is relatively thick and rich in coal and oil shale layers, having positive potential for energy development. In order to explore the sedimentary environment of oil shale and the controlling factors of organic matter accumulation, 18 oil shale samples collected from two boreholes (Guyou-3 and Guyou-4) in the Tanshan area were selected as the research objects, and organic geochemical and elemental geochemical tests were carried out systematically. The results show that oil shales have the characteristics of medium oil content, medium ash, high calorific value, low sulfur and low maturity stage, which constitutes good hydrocarbon generation potential. The organic matter is mainly humic type, resulting from terrigenous debris and higher plant debris. The indictors of C-value (mean 81.90), Th/U ratio (mean 3.44), CaO/(MgO·Al2 O3) ratio (mean 0.07), δEu (mean 0.71),... [more]