Environmental concerns with unconventional oil and gas development are frequently centered on elevated water usage and the induction of seismic events during waste disposal. Reuse of produced water for subsequent production well stimulation can effectively address these concerns, but the variability among such samples must be well understood. Twenty-four samples of wastewater from unconventional oil and gas development were collected from south and west Texas to assess their variability and feasibility for direct reuse. Bulk metrics were collected, including total organic carbon, total nitrogen, as well as total dissolved and suspended solids. The profiles of pertinent inorganic constituents were also evaluated. Variations were not only seen between regions but also among samples collected from the same region. For example, the average total organic carbon for Eagle Ford samples collected was 700 ± 500 mg/L, while samples collected from the Permian Basin featured an average total organ... [more]

In this paper, detailed scalability and replicability plans have been developed to facilitate the adoption of innovation technologies in the pan-EU market. Smart grid development must enable both information and power exchange between suppliers and customers, thanks to the enormous innovation in intelligent communication, monitoring, and management systems. Implementing physical infrastructure alone is not enough, but a smart grid must include new business models and new regulations. In recent years, the number, participants, and scope of smart grid initiatives have increased, with different goals and results. FLEXITRANSTORE project integrates hardware and software solutions in all areas of the transmission system and wholesale markets, unleashing the potential for full flexibility of power systems and promoting the penetration of renewable energy sources and pan-EU markets. Full deployment of these demonstrated solutions requires a reasonable level of scalability and replicability to... [more]

Increasing Uganda’s low electrification rate is one of the country’s major challenges. Power service is essential to achieve socioeconomic development and poverty reduction, especially in rural areas. This paper shows the advantages of using an integrated (grid and off-grid) electrification model with high geospatial, temporal, and customer-class granularity as the Reference Electrification Model (REM). In universal electrification strategies, REM will help better ascertain the role of minigrids, jointly with grid extension, solar kits, and stand-alone systems. REM has been applied to the Southern Service Territory (SST) to determine the least-cost mix of electrification modes—grid extension, off-grid minigrids, and standalone systems—that satisfies the hourly demand requirements of each customer—residential, commercial, or industrial—considering its individual location. REM incorporates the existing grid layout, the hourly solar local profile, and the catalogs of actual components for... [more]

The paper deals with the important challenges in terms of electricity transmission by means of underground cable lines. The power cable’s performance is characterized by an ampacity that represents its maximum electric current-carrying capacity. The ampacity of power cables depends on their ability to diffuse the heat generated by the current flow into the environment. In the performed research, the analysis of the efficiency of heat dissipation from the cable is based on the measurement of temperatures at selected points in individual sections of the cable. As a consequence, the proposed test stand and applied research methodology are vital for the experimental evaluation of the analyzed thermal phenomena in the investigated underground cable lines. The research program covers an in-depth analysis based on the results related to the vital parameters of the investigated cable. The experimental methodology was used to analyze the influence of the properties of the medium surrounding the... [more]

Effective sorting and extraction of tiny plastic objects is becoming increasingly important for manufacturing high-quality recycled plastics. Herein, we designed a manipulation device for tiny objects that can drive multiple target objects individually. This type of device has a potential to sort tiny pieces of a wide variety of materials, not strongly depending on their physical properties, by combining different detection meanings. In this study, two types of devices were tested as the basic components of the proposed device. One of them had a single object-holding point and the other had two of them. These holding points consisted of strip-shaped electrodes facing each other. The high voltage applied to the facing electrodes created forces heading toward the object-holding points caused by the heterogeneity of the electric field in the devices. The forces created in these devices were determined from the motion analysis of a glass sphere, which is a model for target objects, and a n... [more]

The aging of PV cells reduces their electrical performance i.e., the parasitic parameters are introduced in the solar panel. The shunt resistance (RSh), series resistance (RS), photo current (IPh), diode current (Id), and diffusion constant (a1) are known as parasitic or extraction parameters. Cracks and hotspots reduce the performance of PV cells and result in poor V−I characteristics. Certain tests are carried out over a long period of time to determine the quality of solar cells; for example, 1000 h of testing is comparable to 20 years of operation. The extraction of solar parameters is important for PV modules. The Tabu Search Optimization (TSO) algorithm is a robust meta-heuristic algorithm that was employed in this study for the extraction of parasitic parameters. Particle Swarm Optimization (PSO) and a Genetic lgorithm (GA), as well as other well-known optimization methods, were used to test the proposed method’s correctness. The other approaches included the lightning search al... [more]

Metal halide perovskites are excellent semiconductors materials that can be exploited in many fields, from the vastly explored photovoltaics to the recent applications in photocatalysis. One of the material’s known limitations is the poor resistance to moisture which induces degradation, triggered by the soft and defective nature of its surface. In this study, we explore non-equilibrium plasmas, to deposit a fluorocarbon polymer on the surface of a MAPbI3 film. We found that the treatment generally enhances the film stability over time, and in certain conditions it improves the perovskite optical properties, demonstrating to be a good strategy aiming defects passivation. Thanks to the solvent-free and non-invasive nature of plasmas, this technique has the potential to be extensively applied to a wide range of perovskite materials targeting different applications.

The goal of carbon neutrality is an extensive and profound economic and social change, which will have far-reaching impacts on industrial structure, energy structure, and social consumption structure. Energy sectors will face in-depth adjustment, and it is essential to optimize major structures consequently due to the foresight of talent training. This research first employs Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis, Analytic Network Process (ANP), and the weighted fuzzy Technique for Order Performance by Similarity to Ideal Solutions (TOPSIS) to formulate and analyze the structure optimization of academic disciplines, and finally, the universities featuring mining are taken as an example to verify the feasibility of the method. Results reveal that the integration of ANP, SWOT, and the fuzzy TOPSIS evaluation method is able to qualify the assessment for academic discipline optimization. The specialty structure optimization results should focus on clean, intellig... [more]

Considering the problem of passive interference caused by electromagnetic scattering effects of transmission lines to neighboring radio stations and other communication equipment, this paper refines the passive interference calculation model for UHV transmission lines. The solution calculation is carried out by the Method of Moments, and the law of passive interference effect of the tower structure, auxiliary angles, and ground roughness under different frequency incident waves, is summarized. By designing an orthogonal test, the degree of influence of the above attributing factors on passive interference results in the established joint model of three towers with two stall distances was explored by using Analysis of Variance. The results demonstrate that both auxiliary angles and rough ground show a pattern of enhanced electromagnetic scattering effect with increasing plane wave frequency in single-factor analysis. When multiple factors are combined, the rough ground has a significant... [more]

The lower price of energy leads to higher coal consumption in China. The idea of an “environment-for-trade policy” could be used to achieve an international competitive advantage, which, in turn, has important implications. To address the issue, we develop properties to examine the link between the low price of energy and strategic environmental policy in China and investigate the choice of policy instruments in a strategic environmental policy model with vertical contracts. In addition, to contribute to the literature on strategic environmental policy, this paper also develops properties to investigate different choices of instruments for the environmental policy and includes the degree of energy marketization for the wholesale price in the study. To do so, we assume that the wholesale price of the polluting input increases with the market price. By using this assumption, this paper analyzes the effects of two instruments of the environmental policy on social welfare and concludes tha... [more]

Recently, false data injection attacks (FDIAs) have been identified as a significant category of cyber-attacks targeting smart grids’ state estimation and monitoring systems. These cyber-attacks aim to mislead control system operations by compromising the readings of various smart grid meters. The real-time and precise locational identification of FDIAs is crucial for smart grid security and reliability. This paper proposes a multivariate-based multi-label locational detection (MMLD) mechanism to detect the presence and locations of FDIAs in real-time measurements with precise locational detection accuracy. The proposed architecture is a parallel structure that concatenates Long Short-Term Memory (LSTM) with Temporal Convolutional Neural Network (TCN). The proposed architecture is trained using Keras with Tensorflow libraries, and its performance is verified using an IEEE standard bus system in the MATPOWER package. Extensive testing has shown that the proposed approach effectively imp... [more]

Coal and organic-rich shale in the Yan’an Formation in the southwestern margin of the Ordos Basin are widely developed, which is an important fact for oil and gas exploration in China that has been widely explored for a long time. In this paper, detailed sequence division and sedimentary environment analyses of the Yan’an Formation in the Pengyang area on the southwestern margin of the Ordos Basin were conducted using field outcrops, drilling cores, logging, wavelet transform and organic geochemistry. The results showed that the succession consists of some units with distinctly different characteristics. Based on the petrographic assemblage and transform wavelet characteristics, the Yan’an Formation in this area can be divided into a long-term cycle, five medium-term cycles, and eleven short-term cycles, among which coal and carbonaceous shale were mainly developed in the short-term cycles I2, III1, III2, V1 and V2. Coal and organic-rich mud shale have been developed in the Yan’an Form... [more]

In recent years, the increased distributed generation (DG) capacity in electric distribution systems has been observed. Therefore, it is necessary to research existing structures of distribution networks as well as to develop new (future) system structures. There are many works on the reliability of distribution systems with installed DG sources. This paper deals with a reliability analysis for both present and future medium voltage (MV) electric distribution system structures. The impact of DG technology used and energy source location on the power supply reliability has been analyzed. The reliability models of electrical power devices, conventional and renewable energy sources as well as information and communications technology (ICT) components have been proposed. Main contribution of this paper are the results of performed calculations, which have been analyzed for specific system structures (two typical present network structures and two future network structures), using detailed... [more]

Within the context of sustainable development and a low-carbon economy, electric vehicles (EVs) are regarded as a promising alternative to engine vehicles. Since the increase of charging EVs brings new challenges to charging stations and distribution utility in terms of economy and reliability, EV charging should be coordinated to form a friendly and proper load. This paper proposes a novel approach for pricing of charging service fees in a public charging station based on prospect theory. This behavioral economics-based pricing mechanism will guide EV users to coordinated charging spontaneously. By introducing prospect theory, a model that reflects the EV owner’s response to price is established first, considering the price factor and the state-of-charge (SOC) of batteries. Meanwhile, the quantitative relationship between the utility value and the charging price or SOC is analyzed in detail. The EV owner’s response mechanism is used in modeling the charging load after pricing optimiza... [more]

The characteristics of solar and wind energy determine that the optimization of a standalone hybrid wind turbine (WT)/photovoltaic panel (PV) system depends on the natural resources of the installation location. In order to ensure system reliability and improve the resource utilization, a method for determining the installed capacity ratio of a hybrid renewable energy system is required. This study proposes a calculation method to optimize the installed capacity ratio, considering the system reliability to meet the needs of the hybrid system to adapt to different natural resources. In this paper, a standalone hybrid WT/PV system to provide electricity for rural areas is designed. Taking the power supply guarantee rate and electricity supply continuity as indicators, the system is simulated by using the Transient System Simulator solver. The results show that the recommended installed capacity ratio of the WT and PV is 5:1 when the total solar irradiation is less than 5040 MJ/(m2·a) and... [more]

Three-dimensional (3D) seismic data and well log data were used to investigate the sandstone architecture of the Middle Jurassic deltaic reservoirs of the Zhetybay Oilfield, Mangeshrak Basin, Kazakhstan. The base-level cycles of different scales were identified and divided using well log and 3D seismic data. Five types of sedimentary boundaries were identified in the mouth bar sandstones. The boundaries divide single mouth bars. Vertically, the spatial distribution of sand bodies can be divided into superposed, spliced, and isolation modes. Laterally, contact modes can be divided into superposition, lateral, and isolation modes. We found that the base-level cycle controls the evolution of the delta front sand body architecture. In the early decline or late rise of the base-level cycle, the superimposed or spliced modes dominate the sand body. By contrast, the lateral or isolation modes dominate the sand body in the late decline or early rise of the base-level cycle. This paper proposes... [more]

This article presents a new method for the classification of machine failures using an example of selected generating sets. Measurements and an analysis of the electrical parameters, such as the phase-to-phase voltages at the terminals of a synchronous generator, armature current, and voltage and excitation current of a synchronous generator, are the basis for determining the failure symptoms. The existing energy quality coefficients are adopted as symptoms for the assessment of failures in the monitored generating set. We assume in this method that the description of the input−output relationship is in the form of a black box and use the binary diagnostics matrix (BDM) to investigate the failure−symptom relationships between the inputs (intentional failures) and outputs (failures symptoms = fault-sensitive power quality (PQ) coefficients). The method presented in this article enables the detection and classification of both electrical damage in a synchronous generator and mechanical d... [more]

Shifting from heating using fossil fuel combustion to electrified heating, dominated by heat pumps, is central to many countries’ decarbonisation strategy. The consequent increase in electricity demand, combined with that from electric vehicles, and the shift from non-renewable to renewable generation requires increased demand flexibility to support system operation. Demand side response through interrupting heating during peak demands has been widely proposed and simulation modelling has been used to determine the technical potential. This paper proposes an empirical approach to quantifying a building’s potential to operate flexibly, presenting a metric based on measured temperature drop in a dwelling under standard conditions after heating is switched off, using smart meter and internal temperature data. A result was derived for 96% of 193 homes within a test dataset, mean temperature drop of 1.5 °C in 3 h at 15 °C inside-outside temperature differential. An empirical flexibility met... [more]

In order to ensure safe working conditions for miners underground, many works are carried out in mines to strengthen and seal mining excavations. This article presents the successfully applied technology for removing water inflow from the unique Salt Mine. Failure to take such action may ultimately lead to the flooding of the “Wieliczka” Salt Mine (KSW). On the basis of the authors’ research studies, some of the implemented works at the “Wieliczka” Salt Mine are presented, the purpose of which is to better protect the mine against the risk of flooding with water. Thanks to this, the mine can safely survive for many more years. This article presents two innovative technologies in salt mines: (1) sealing of the rock mass surrounding the Kościuszko shaft casing in the “Wieliczka” Salt Mine, where jet injection was used as the basic method of making an anti-filter screen outside the shaft casing and classic injection as a supplementary method for sealing the anthropogenic embankment; (2) r... [more]

To increase combustion efficiency and reduce pollutant emissions, this study presents an online closed-loop optimization method and its application in a boiler combustion system. To begin with, three adaptive dynamic models are established to predict NOx emission, the carbon content of fly ash (Cfh), and exhaust gas temperature (Teg), respectively. In these models, the orders of the input variables are considered to enable them to reflect the dynamics of the combustion system under load changes. Meanwhile, an adaptive least squares support vector machine (ALSSVM) algorithm is adopted to cope with the nonlinearity and the time-varying characteristics of the combustion system. Subsequently, based on the established models, an economic model predictive control (EMPC) problem is formulated and solved by a sequential quadratic programming (SQP) algorithm to calculate the optimal control variables satisfying the constraints on the control and control moves. The closed-loop optimization syste... [more]

This editorial provides a synopsis of the contributions published during 2020−2021 in a Special Issue of Energies entitled “Cogeneration Economics” [...]

This Special Issue was intended to consolidate the most recent advances in the field of power electronics for renewable energy sources and electric drives [...]

This paper presents a mathematical model of heat transfer behavior between the liquid inside vertical underground geothermal pipes and the surrounding ground for heating (in the winter) and cooling (in the summer) modes in a ground heat exchanger (GHE) that can optimize its output temperature. The GHE’s output temperature reaches the appropriate value when the water velocity is lowered enough. Subsequently, the proposed model was applied to a case study of a 400-ton geothermal heat pump system (GHPS) at Oakland University, in both the heating and cooling modes, to assess its validity and improve the GHE’s performance. The model was implemented in MATLAB using an ordinary differential equation (ODE) solver. Four different water velocities were used to demonstrate the significant effect of velocity on the loop exit temperature. Model predictive control (MPC) was designed to optimize the GHE’s output temperature by controlling the water velocity, which could reduce the energy consumption... [more]

The efficiency potential of a small-size solar-pumped laser is studied here. The solar laser head was composed of a fused silica aspheric lens and a conical pump cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic mirror with an effective collection area of 0.293 m2 to end-side pump a Ce (0.1 at%):Nd (1.1 at%):YAG rod of 2.5 mm diameter and 25 mm length. Optimum solar laser design parameters were found through Zemax© non-sequential ray-tracing and LASCAD™ analysis. The utilization of the Ce:Nd:YAG medium with small diameter pumped by a small-scale solar concentrator was essential to significantly enhance the end-side pump solar laser efficiency and thermal performance. For 249 W incoming solar power at an irradiance of 850 W/m2, 11.2 W multimode solar laser power was measured, corresponding to the record solar-to-laser power conversion efficiency of 4.50%, being, to the best of our knowledge, 1.22 times higher than the previous re... [more]

The penetration of renewable energy sources (RESs) in the electrical power system has increased significantly over the past years due to increasing global concern about climate change. However, integrating RESs into the power market is highly problematic. The output of RESs such as wind turbines (WTs) and photovoltaics (PVs) is highly uncertain. Their correlation with load demand is not always guaranteed, which compromises system reliability. Distributed energy resources (DERs), especially demand response (DR) programs and energy storage systems (ESSs), are possible options to overcome these operational challenges under the virtual power plant (VPP) setting. This study investigates the impact of using a DR program and battery energy storage system (BESS) on the VPP’s internal electricity market, and also cost-minimization analysis from a utility viewpoint. Three different constrained optimal power flow (OPF) problems are solved such as base case, DR case, and BESS case to determine tot... [more]