Casing deformation is a common but serious problem experienced during hydraulic fracturing operations in shale reservoirs. The Multi-Finger Imaging Tool is used to measure the casing deformation where the casing inner diameter is the only parameter used to characterize the deformation. Many deformed casing geometric details are often ignored, and these geometric characteristics are helpful for revealing the casing deformation mechanism. In this study, we established a quantitative method to describe the casing deformation using methods of judging the similarity of curves. By comparing the field casing deformation sections and the initial casing section, we categorized the casing deformation sections into concave and elliptical types. Furthermore, using the centroid calculation, elliptical type was sub-divided into symmetric ellipse type and eccentric ellipse type. On the basis of the Weiyuan and Guandong oil field’s fault distribution maps, we demonstrated that the fault slip could be... [more]

Because of disruptive changes in energy businesses and services, as well as changes in people’s lifestyles around the world, energy demand and consumption have risen quickly in recent decades. A household energy awareness literature review was conducted. The survey was conducted in Poland with over 1097 respondents. Additionally, it was given a qualitative analysis. At the same time, in order to consider why energy consumption in households is increasing, a traditional quality management tool was used—the Ishikawa diagram. The Pareto−Lorenz diagram was used to analyze the causes of the increase in energy consumption in households. A model of the causes of increasing energy consumption in households has been built. The researchers calculated the chi-square test, which allows them to determine Pearson’s C coefficient. The C-Pearson coefficient can be calculated using the Chi square value. The results of the study clearly show that the respondents have knowledge of energy and the factors... [more]

The modular multilevel converter with embedded batteries is a viable alternative in electric vehicle drive systems. This research investigates integrated charging of the embedded batteries in a three-phase converter from a single-phase source without any additional hardware requirements. Two phases of the converter are connected to the supply while the third converter leg is not connected. In a typical charging of the converter batteries, the batteries with a lower state of charge are prioritised. Then all batteries are balanced at an average global state of charge. This research proposes a new sorting algorithm of the converter batteries with an override capability to bypass any individual submodule if required. This bypassing capability is modulation method independent, thus can be integrated with any modulation method. Simulation results and a real-time emulation of the charging system validate the proposed control method and the override algorithm. In addition, an open-loop switchi... [more]

In this paper, a new method using wind turbulence excitation is proposed to estimate the parameters of the mechanical system (drivetrain and pitch angle controller) in a Doubly Fed Induction Generator (DFIG) Wind Turbine (WT). Firstly, simulations were carried out for a DFIG WT under turbulence excitations. The spectral contents of the responses imply that the transients of the electrical system (generator and converter), which are much faster than those of the mechanical system, can be neglected when estimating the mechanical parameters. Based on this, a simplified model related to the mechanical system of the DFIG WT was derived by applying the model reduction technique. Secondly, the parameter sensitivity of Power Spectral Density (PSD) was used to quantify the impacts of individual parameters on the dynamics of the mechanical system, and the influential parameters were selected on the basis of the sensitivity results. Finally, a weighted least-squares optimization problem, which is... [more]

This study aims to review the potential benefits of peak load shaving in a microgrid system. The relevance of peak shaving for a microgrid system is presented in this research review at the outset to justify the peak load shaving efficacy. The prospective benefits of peak shaving in microgrid systems, including technological, economic, and environmental advantages, are thoroughly examined. This review study also presents a cost−benefit numerical analysis to illustrate the economic viability of peak load shaving for a microgrid system. Different peak shaving approaches are briefly discussed, as well as the obstacles of putting them into practice. Finally, this review study reveals some potential future trends and possible directions for peak shaving research in microgrid systems. This review paper lays a strong foundation for identifying the potential benefits of peak shaving in microgrid systems and establishing suitable projects for practical effectuation.

One of the big concerns when planning the expansion of power distribution systems (PDS) is reliability. This is defined as the ability to continuously meet the load demand of consumers in terms of quantity and quality. In a scenario in which consumers increasingly demand high supply quality, including few interruptions and continuity, it becomes essential to consider reliability indices in models used to plan PDS. The inclusion of reliability in optimization models is a challenge, given the need to estimate failure rates for the network and devices. Such failure rates depend on the specific characteristics of a feeder. In this context, this paper discusses the main reliability indices, followed by a comprehensive survey of the methods and models used to solve the optimal expansion planning of PDS considering reliability criteria. Emphasis is also placed on comparing the main features and contributions of each article, aiming to provide a handy resource for researchers. The comparison i... [more]

Metal hydroxides, owing to their catalytic active sites for the decomposition of O3 to Reactive Oxygen Species (ROS), have been adapted for catalytic ozonation of micropollutants in wastewater. In this study, commercial Mg (OH)2 was used for the degradation of cyclophosphamide (CYP) by ozone. The crystal phase was confirmed by X-ray powder Diffraction (XRD). Percent degradation of 10 ppm CYP after 30 min by O3 and Mg (OH)2/O3 was 56 and 93, respectively, suggesting enhanced decomposition of O3 to ROS by the catalyst. The presence of ROS was further confirmed using pCBA as a probe, which showed that the concentration of ROS was eight times higher in the presence of Mg (OH)2/O3 than O3 alone. Catalytic ozonation experiments in the presence of scavengers showed that OH· radicals play a significant role in the degradation of CYP. The catalyst was found to be reusable for at least three cycles without significant loss in degradation efficiency. To study the compatibility of Mg (OH)2 for was... [more]

This paper presents a scalable IoT architecture based on the edge−fog−cloud paradigm for monitoring the Indoor Environmental Quality (IEQ) parameters in public buildings. Nowadays, IEQ monitoring systems are becoming important for several reasons: (1) to ensure that temperature and humidity conditions are adequate, improving the comfort and productivity of the occupants; (2) to introduce actions to reduce energy consumption, contributing to achieving the Sustainable Development Goals (SDG); and (3) to guarantee the quality of the air—a key concern due to the COVID-19 worldwide pandemic. Two kinds of nodes compose the proposed architecture; these are the so-called: (1) smart IEQ sensor nodes, responsible for acquiring indoor environmental measures locally, and (2) the IEQ concentrators, responsible for collecting the data from smart sensor nodes distributed along the facilities. The IEQ concentrators are also responsible for configuring the acquisition system locally, logging the acquir... [more]

Voltage sag state estimation on the basis of a limited number of installed monitors is essential to dividing the responsibility for the voltage sag and taking corresponding measurements for improvement in voltage quality. Therefore, a deep learning methodology via bidirectional WaveNet for the voltage sag state estimation is proposed in this paper. The presented method can simultaneously estimate voltage sag state at non-monitored buses via limited monitors. Especially, the proposed deep learning method using the bidirectional WaveNet is designed to explore the long-term and long-range temporal dependencies in both the forward and backward directions. In this way, only by using original measured voltages through monitors, high accuracy for voltage sag state estimation can be achieved without restructured or redesign of the raw monitored data. An excellent advantage of the presented algorithm is that it can be implemented without system parameters or operating conditions or any other pr... [more]

Intermediate pyrolysis can be used to obtain high-quality biofuels from low-value residues such as sewage sludge or digestate. A major obstacle is the high water content of sludgy biomass, which requires an energy-intensive and expensive drying step before pyrolysis. Solar greenhouse drying is an efficient and sustainable alternative to a thermally heated belt dryer. In this study, a techno-economic assessment of intermediate pyrolysis with solar drying is carried out. Marketable products of the process are bio-oil, a substitute for diesel or heating oil, and bio-char with various possible applications. Chile is chosen as the setting of the study as its 4000 km long extension from north to south gives the opportunity to evaluate different locations and levels of solar irradiation. It is found that solar drying results in higher capital investment, but lower fuel costs. Depending on the location and solar irradiation, solar drying can reduce costs by 5−34% compared to belt drying. The b... [more]

The oil and gas industry has shifted paradigms after seeing the drastic decrease in oil prices since 2015. Companies are now focused as much on cost reduction as much as production maximization to drive profitable operations. This aspect is more prevalent in unconventional plays with the need for long horizontal drilling and hydraulic fracturing (HF) operations to develop and produce from the tight reservoirs. There exists an optimum point between the costs of HF treatment and the expected production. Because of the paradigm shift, many operators are now focused on re-developing existing assets at much lower costs instead of developing newer, more costly assets. Re-fracturing existing wells provides an opportunity for companies to add economical wells to their portfolio. Re-fracturing consists of pumping HF treatments in wells that were previously drilled and completed. Although it may seem that the HF process on a well would be easier the second time around, this is not always the cas... [more]

Member 1 of the Cretaceous Qingshankou Formation (K2qn1 Member) in the Southern Songliao Basin, composed of mainly semi-deep and deep lacustrine shale layers, is rich in shale oil. Previous studies on shale reservoir characteristics mainly focused on marine shale strata, but few studies have considered lacustrine shale strata, so the pore-throat features and differences between the lacustrine shale reservoir and marine shale reservoir need to be studied. Taking the Class-I and II sweet spot sections and Class-III non-sweet spot section of Da’an shale oil demonstration area as examples, SEM (scanning electron microscopy) was used to qualitatively and semi-quantitatively describe the morphology and occurrence characteristics of the shale. Full-scale pore size distributions of lacustrine shale samples were quantitatively measured by N2GA (nitrogen absorption) combined with dominant pore size segments tested by experiments. Finally, the lacustrine shale reservoir was compared with classica... [more]

The aim of this study is to identify the correlation between the amount of greenhouse gas emissions, added value from agriculture and economic growth in the Visegrad Group countries. Four countries of Central Europe were studied the Czech Republic, Hungary, Poland and Slovakia in 2008−2019. Due to the objectives of the article, it was decided to use the panel model. The temporal scope of the research covers the years 2008−2019, i.e., two economic periods: 2008−2014 (a downward trend, including agriculture), and 2015−2019 (an upward trend). Greenhouse gas emissions are positively correlated with value added from agriculture and economic growth. The increase in the level of these variables stimulates of the amount of greenhouse gas emissions in the countries of the Visegrad Group. The analysis of the eco-efficiency of greenhouse gas emissions in agriculture, in relation to the gross added value produced, shows that the country with the least pollution of this value was Hungary, followed... [more]

The research proposes a new oppositional sine cosine muted differential evolution algorithm (O-SCMDEA) for the optimal allocation of distributed generators (OADG) in active power distribution networks. The suggested approach employs a hybridization of the classic differential evolution algorithm and the sine cosine algorithm in order to incorporate the exploitation and exploration capabilities of the differential evolution algorithm and the sine cosine algorithm, respectively. Further, the convergence speed of the proposed algorithm is accelerated through the judicious application of opposition-based learning. The OADG is solved by considering three separate mono-objectives (real power loss minimization, voltage deviation improvement and maximization of the voltage stability index) and a multi-objective framework combining the above three. OADG is also addressed for DGs operating at the unity power factor and lagging power factor while meeting the pragmatic operational requirements of... [more]

The paper presents chosen experimental and model methods of investigating heat transfer in a steel porous charge. The results of this investigation provide information on both the qualitative and quantitative course of the analysed processes of heat exchange. The parameters which characterise the analysed phenomenon in a quantitative manner, among others, are: The effective thermal conductivity kef, the thermal contact resistance Rct and Nusselt number Nu. It has been established that it is not possible to use literature models in order to determine the kef coefficient. The authors present their own model of effective thermal conductivity. The above-mentioned parameters for a porous charge reach the values within the following ranges: kef: 1.0−8.5 W/(m·K); Rct: 0.0019−0.0057 (m2⋅K)/W; Nu: 1.2−7.1.

An analysis of the literature data indicates a wide front of research and development in the field of the use of methane−hydrogen mixtures as a promising environmentally friendly low-carbon fuel. The conclusion of most works shows that the use of methane−hydrogen mixtures in internal combustion engines improves their performance and emission characteristics. The most important aspect is the concentration of hydrogen in the fuel mixture, which affects the combustion process of the fuel and determines the optimal operating conditions of the engine. When using methane−hydrogen mixtures with low hydrogen content, the safety measures and risks are similar to those that exist when working with natural gas. Serious logistical problems are associated with the difficulties of using the existing gas distribution infrastructure for transporting methane−hydrogen mixtures. It is possible that, despite the need for huge investments, it will be necessary to create a new infrastructure for the product... [more]

Using timber from multifunctional forests for energy production can be economically viable and environmentally friendly when it is consistent with the principles of sustainable management; otherwise, it could be harmful from both an ecological and commercial point of view. The objective of this paper was to present the overall balance of timber biomass from felled trees in multifunctional forests and assess what kind and how much of this biomass can be used for energy purposes. The research material consisted of data on forest resources and the volume of timber removal in Polish State Forests in 2016−2020. The biomass of branches and stumps of felled trees was determined using biomass expansion factors (BEFs). The results obtained in this study indicated that industrial timber, energy wood, and biomass left in the forest as a source of deadwood are 67%, 20%, and 13% of the total woody biomass, respectively. The Polish State Forest’s potential for energy wood is estimated at 6.18 millio... [more]

Smart grids provide a unique platform to the participants of energy markets to tweak their offerings based on demand-side management. Responding quickly to the needs of the market can help to improve the reliability of the system, as well as the cost of capital investments. Electric load forecasting is important because it is used to make and run decisions about the power grid. However, people use electricity in nonlinear ways, which makes the electric load profile a complicated signal. Even though there has been a lot of research done in this field, an accurate forecasting model is still needed. In this regard, this article proposed a hybrid cross-channel-communication (C3)-enabled CNN-LSTM model for accurate load forecasting which helps decision making in smart grids. The proposed model is the combination of three different models, i.e., a C3 block to enable channel communication of a CNN (convolutional neural networks) model, two convolutional layers to extract the features and an L... [more]

Methane is one of the most dangerous gases encountered in the mining industry. During mining operations, methane can be broadly classified into three states: mining excavation, stoppage safety check, and abnormal methane concentration, which is usually a precursor to a gas accident, such as a coal and gas outburst. Consequently, it is vital to accurately predict methane concentrations. Herein, we apply three deep learning methods—a recurrent neural network (RNN), long short-term memory (LSTM), and a gated recurrent unit (GRU)—to the problem of methane concentration prediction and evaluate their efficacy. In addition, we propose a novel prediction method that combines classical time series analysis with these deep learning models. The results revealed that GRU has the least root mean square error (RMSE) loss of the three models. The RMSE loss can be further reduced by approximately 35% by using the proposed combined approach, and the models are also less likely to result in overfitting.... [more]

In this research paper, various performances of five different rotor pole topologies of the proposed novel modular stator (MS) permanent magnet (PM) flux reversal machine were investigated. The proposed design had concentrated, non-overlapping winding, which offered high average torque capability at a wide speed range. The no-load performances such as coil test analysis, three-phase flux linkage, flux distribution, back-EMF, and cogging torque, and load analysis, such as average torque versus current density, instantaneous torque, and average electromagnetic torque, were compared. The PM modular stator machine had high cogging torque, which created vibration and noise in the machine. Different cogging torque reduction techniques, such as notching, arc, flange and hybrid technique arc flange, arc notch, notch flange, and arc notch flange, were applied to reduce the cogging torque, improve average load torque, and reduce the induced voltage, harmonics, and torque ripples. The maximum cog... [more]

This paper presents a conceptual development of sustainability evaluation, through an exergy-based indicator, by using the new concept of the Thermoeconomic Environment (TEE). The exergy-based accounting methods here considered as a background are Extended Exergy Accounting (EEA), which can be used to quantify the exergy cost of externalities like labor, monetary inputs, and pollutants, and Cumulative Exergy Consumption (CExC), which can be used to quantify the consumption of primary resources embodied in a final product or service. The new concept of bioresource stock replacement cost is presented, highlighting how the framework of the TEE offers an option for evaluating the exergy cost of products of biological systems. This sustainability indicator is defined based on the exergy cost of all resources directly and indirectly consumed by the system, the equivalent exergy cost of all externalities implied in the production process and the exergy cost of the final product.

In warm and hot climates, ceiling fans and/or air conditioners (ACs) are used to maintain thermal comfort. Ceiling fans provide air movement near the skin, which enhances the evaporation of sweat, reduces heat stress, and enhances thermal comfort. This is also called the cooling effect. However, AC usage behaviour and the effects of elevated air speed through the use of ceiling fans on indoor operative temperature during AC usage are not widely studied. This study investigated the optimum AC (cooling) set point temperature and air velocity necessary for maintaining thermal comfort while achieving energy conservation, in mixed-mode buildings in India, through field studies by using used custom-built Internet of Things (IOT) devices. In the current study, the results indicate a 79% probability that comfort conditions can be maintained by achieving a temperature drop of 3K. If this drop can be achieved, as much as possible, through passive measures, the duration of AC operation and its en... [more]

This study determines the energy usage pattern for Penghu, which is an island in the Taiwan Strait, for which electricity is the major energy source. There is an increase in electricity consumption as the number of inhabitants and tourists increases. Water supply from desalination plants represents another major electricity demand. To reduce energy consumption and carbon emissions, subsidy programs are used to encourage the use of LED lighting and energy-efficient appliances (air conditioners and refrigerators), but not for common appliances, such as chest freezers. Abundant solar radiation in summer and the northeast monsoon in autumn/winter make Penghu an ideal location to take advantage of solar energy and wind power. An undersea cable between Penghu and Taiwan is now available and can be used to stabilize the isolated grid system in Penghu. The target for a low-carbon island can be achieved by installing PV systems and onshore and offshore wind turbines to fulfill the energy demand... [more]

Wireless rechargeable sensor networks (WRSN) are utilized in environmental monitoring, traffic video surveillance, medical services, etc. In most existing schemes, WRSNs provide sustainable energy for sensor nodes by employing one or more wireless charging vehicles (WCVs). However, two essential drawbacks, regional limitations and traveling speed limitations, constrain these schemes when applied in hostile and large-scale environments. On the other hand, benefiting from the intrinsic flexibility, high flight speed, low cost, and small size of drones, some works have used drones to charge sensor nodes. However, suffering from limited battery capacities, it is also hard to only use drones in large-scale WRSNs. To overcome the drawbacks of WCVs and drones, we proposed a novelty wireless charging system that deploys WCV, WCV-carried drones, and wireless charging pads (pads) in a large-scale wireless sensor network. Based on this new wireless charging system, we first formulated a pad deplo... [more]

In the paper, the problem of modeling of thermal traces is addressed. The proposed model allows prediction of the behaviour of a thermal mark left by a warm body on cooler ground. In the model, a fractional order (FO) approach is employed. This allows consideration of an inital function (not only a condition in one, initial time instant). The proposed model uses a scalar FO differential equation approximated with the use of Continuous Fraction Expansion (CFE) approximation. This allows maintenance of a relatively small size of the model with good accuracy in the sense of a Mean Square Error (MSE) cost function. Experimental verification confirms good accuracy of the proposed model in modeling of thermal traces.