The absence of electricity is among the gravest problems preventing a nation’s development. Hybrid renewable energy systems (HRES) play a vital role to reducing this issue. The major goal of this study is to use the non-dominated sorting genetic algorithm (NSGA)-II and hybrid optimization of multiple energy resources (HOMER) Pro Software to reduce the net present cost (NPC), cost of energy (COE), and CO2 emissions of proposed power system. Five cases have been considered to understand the optimal HRES system for Kutubdia Island in Bangladesh and analyzed the technical viability and economic potential of this system. To demonstrate the efficacy of the suggested strategy, the best case outcomes from the two approaches are compared. The study’s optimal solution is also subjected to a sensitivity analysis to take into account fluctuations in the annual wind speed, solar radiation, and fuel costs. According to the data, the optimized PV/Wind/Battery/DG system (USD 711,943) has a lower NPC t... [more]

This paper describes a system for the automatic determination of rock-breaking target poses for impact hammers used in underground mines. The rock-breaking target pose is defined as the position and angle at which the impact hammer must strike a rock in order to break it. The automatic determination of this pose is essential for the autonomous operation of an impact hammer. The proposed system takes as input sensor data composed of point clouds and images, and automatically determines a rock-breaking target pose. The system consists of a rock segmentation subsystem that receives the sensor data and identifies and individualizes the rocks/boulders present above the grizzly, and a rock-breaking target pose generation and evaluation subsystem that receives the rock information produced by the rock segmentation subsystem, and generates a list of rock-breaking target pose candidates, it evaluates them, and it selects the best candidate as the rock-breaking target pose. The system is evaluat... [more]

The Special Issue “Sensitivity Analysis, Uncertainty Quantification and Predictive Modeling of Nuclear Energy Systems” comprises nine articles that present important applications of concepts for performing sensitivity analyses and uncertainty quantifications of models of nuclear energy systems [...]

This editorial aims to summarize 10 articles (7 scientific papers and 3 review papers) that contributed to the Special Issue “Geothermal Systems—An Overview”. This Special Issue contains information on both shallow and deep geothermal systems, and analyzes geothermal resources (low and high temperature) in various locations around the world.

A global transition to power grids with high penetrations of renewable energy generation is being driven in part by rapid installations of distributed energy resources (DER). New DER equipment includes standardized IEEE 1547-2018 communication interfaces and proprietary communications capabilities. Interoperable DER provides new monitoring and control capabilities. The existence of multiple entities with different roles and responsibilities within the DER ecosystem makes the Access Control (AC) mechanism necessary. In this paper, we introduce and compare two novel architectures, which provide a Role-Based Access Control (RBAC) service to the DER ecosystem’s entities. Selecting an appropriate RBAC technology is important for the RBAC administrator and users who request DER access authorization. The first architecture is centralized, based on the OpenLDAP, an open source implementation of the Lightweight Directory Access Protocol (LDAP). The second approach is decentralized, based on a p... [more]

It is known that the energy transition can be achieved not only with the use of renewable energy sources but also with a new conception and management of the electricity system. Renewable energy communities are then introduced as organizations for maximizing the self-consumption of energy produced from renewable energy sources. To ensure that these energy communities can operate, there is a need for enabling technologies that allow for monitoring, data and algorithms processing as well as the enabling of the same algorithms. There exists a huge confusion in the actual technologies useful to implement the energy communities. This paper first describes and groups the main enabling technologies, analyzing the services that can be offered. The scope is to emphasize the importance of having accurate, efficient and effective technologies that allow the implementation of such communities, underlining how such technologies interact with each other. Using such technologies is important to obser... [more]

With the increase of the scale of wind turbines, the problem of data quality of wind turbines has become increasingly prominent, which seriously affects the follow-up research. A large number of abnormal data exist in the historical data recorded by the wind turbine Supervisory Control And Data Acquisition (SCADA) system. In order to improve data quality, it is necessary to clean a large number of abnormal data in the original data. Aiming at the problem that the cleaning effect is not good in the presence of a large number of abnormal data, a method for cleaning abnormal data of wind turbines based on constrained curve fitting is proposed. According to the wind speed-power characteristics of wind turbines, the constrained wind speed-power curve is fit with the least square method, and the constrained optimization problem is transformed into an unconstrained optimization problem by using the external penalty function method. Data cleaning was performed on the fitted curve using an impr... [more]

This paper presents the Park model of a solid-rotor induction motor. In this model, the dynamic state of the motor is described by integer and noninteger order differential equations. The skin effect in the solid rotor was represented by resistance and inductance with lumped constants, and the fractional inductance was dependent on the frequency of the eddy current induced in the rotor. The parameters of the equivalent circuit were determined by the standstill frequency response test with the stationary machine on the basis of the finite element method analysis of the electromagnetic field. A simulation of the dynamic states of the induction motor with a solid rotor was carried out based on the calculated parameters. The simulation was carried out using a program written in the Matlab environment. The simulations show that the electromagnetic moment during the motor start-up is about 2 times greater than the initial torque in the steady state. On the other hand, the maximum value of th... [more]

Most temperature predictions for deep geothermal applications rely on correcting bottom-hole temperatures (BHTs) to undisturbed or static formation temperatures (SFTs). The data used for BHT correction are usually of low quality due to a lack of information and poor documentation, and the uncertainty of the corrected SFT is therefore unknown. It is supposed that the error within the input data exceeds the error due to the uncertainty of the different correction schemes. To verify this, we combined a global sensitivity study with Sobol indices of six easy-to-use conventional correction schemes of the BHT data set of the Bavarian Molasse Basin with an uncertainty study and developed a workflow that aims at presenting a valid error range of the corrected SFTs depending on the quality of their input data. The results give an indication of which of the investigated correction methods should be used depending on the input data, as well as show that the unknown error in the input parameters e... [more]

Underfloor air distribution (UFAD) systems are increasingly used for their advantages in improving energy savings, indoor air quality, and thermal comfort. In UFAD systems, an underfloor plenum delivers conditioned air to the air supply diffusers. The distribution of internal air velocity and static pressure in plenums determines the uniformity of the airflow to the occupied zones. As a result, the plenum has a detrimental effect on the characteristics of the supply air and, thus, the resulting indoor air quality and thermal comfort. Nevertheless, most existing studies on underfloor plenums focused on small-scale plenums with a single internal air duct. Large plenums and multiple air ducts in UFAD equipped in large premises are underexplored. In this study, a circular underfloor plenum with a large scale (radius of 15 m, height difference of 0.9−2.9 m) and 503 under-seat diffusers in a conference room was studied using computational fluid dynamics (CFD) simulation (ANSYS Fluent (16.0))... [more]

Separation of water-in-oil emulsion is a significant part of the cost of oil production due to the use of expensive demulsifiers and additional heating of the emulsion by burning associated petroleum gas. The article discusses an acoustic method that enables the increasing of the rate of separation of the emulsion. In field conditions, tests were carried out in which the efficiency of separation in the acoustic field was determined depending on the temperature of the product, the concentration of the demulsifier, and the frequency and time of exposure to the emitter. The results obtained allow us to talk about a significant reduction in the consumption of demulsifiers, a decrease in the influence of temperature on the phase separation process and an increase in the efficiency of oil treatment at existing facilities.

Methane emissions into mine workings and the atmosphere are still a significant environmental and work safety problem. Since 2000, the Rydułtowy coal mine, located in the western part of the Upper Silesian Coal Basin, has been struggling with significant methane emissions compared to the previous period. The distribution of the methane content in coal seams was analysed, and the factors that influenced it were reviewed. Then, the annual variability in methane emissions in mining excavations was investigated, and the depth of coal extraction was linked to methane conditions and the time of mining works. It has been shown that the currently observed distribution of methane in coal seams is the result of, inter alia, the geological development of the western part of the basin, the lithological character of coal-bearing Carboniferous deposits and overburden, and fault tectonics. The sorption capacity of coal seams decreases with increasing temperature and the coal rank. The amount of metha... [more]

In order to optimize the combustion chamber of a highly intensified single-cylinder diesel engine, including improvement of the air utilization rate in the combustion chamber, optimization of the fuel/air mixture process, reduction of the soot emission in the cylinder, and obtainment of the optimal combustion performance parameters, a re-entrant combustion chamber with step-typed lip (RCSL) and a re-entrant combustion chamber with tilted lip (RCTL) were innovatively designed and the effects of the throat diameter on the combustion process was obtained through experiments. When the RCSL with a diameter of 72 mm worked, target for the Brake Mean Effective Pressure (BMEP) of 2.6 MPa could be achieved under the condition of excess air coefficient of 1.5~1.7. At the same time, this had the advantages of lower fuel consumption, lower exhaust temperature, lower smoke level, and shorter combustion duration. Under the same BMEP, the RCTL had lower fuel consumption, exhaust gas temperature and m... [more]

Rock bursts occur in nearly vertical coal seam mines at shallow to moderate burial depths, which endangers safe mining. To study the rock burst mechanisms of nearly vertical and extremely thick coal seams, the characteristics of rock bursts were studied via on-site investigation, and a field test of in situ stress was carried out. The mechanical behavior of rock pillars in the middle of the B1+2 and B3+6 coal seams was analyzed using theoretical and numerical simulation methods. The results show that the horizontal maximum principal stress orientation and the nearly vertical coal seam strike were both 82°. The bending of the rock pillars occurred due to the horizontal unbalanced force, and a large amount of bending energy was accumulated within 50 m above the mining level. Rock pillars were bent toward the B1+2 mining goaf and exerted a reverse bending and squeezing effect on the B3+6 coal seam below the mining levels. In addition to the inclination and compression of the B3+6 coal sea... [more]

As a country with not only significant production potential but also fragmented land ownership, the Kyrgyz Republic struggles with environmental efficiency, which is a strategic element of environmental management in agricultural production. The objective of this study was to assess the environmental efficiency of sheep’s wool when used as a fertilizer in bean production in northern Kyrgyzstan. In this study, the efficiency indicator was taken to be GHG emissions per functional unit of product, using a proprietary methodology for calculating GHG emissions to determine the true value of this material as a source of soil nutrients and organic matter. Two experimental factors were used in the experiment: fertilizer type and fertilizer rate. Fertilization with sheep wool resulted in a 15% higher bean yield compared to when fertilized with mineral fertilizers at a comparable rate, converted to pure nitrogen. By using sheep wool as a source of mineral nutrients for the plants, the carbon foo... [more]

Voltage source converter based high voltage DC system (VSC-HVDC) has become a very promising solution to integrate offshore wind farm. However, the equivalent inertia of the modern power system with large renewable energy integration becomes small, which will arouse some frequency stability problems. To tackle this problem, this paper proposes an improved frequency regulation strategy for VSC-HVDC integrated offshore wind farm. Firstly, in the frequency decrease stage, the rotor kinetic energy of wind turbines (WTs) is used to suppress the decrease of the frequency, and the control parameters are determined to make full use of the mechanical power and rotor kinetic energy of WTs, the frequency nadir is improved. Secondly, in the rotor speed recovery stage, the DC capacitors of VSC-HVDC are used to release power to compensate the deficiency value of wind farm output power and avoid the secondary frequency drop (SFD) problem. Lastly, the simulation is conducted in PSCAD/EMTDC to validate... [more]

The use of fossil energy sources has a negative impact on the economic and socio-political stability of specific regions and countries, causing environmental changes due to the emission of greenhouse gases. Moreover, the stocks of mineral energy are limited, causing the demand for new types and forms of energy. Biomass is a renewable energy source and represents an alternative to fossil energy sources. Microorganisms produce energy from the substrate and biomass, i.e., from substances in the microenvironment, to maintain their metabolism and life. However, specialized microorganisms also produce specific metabolites under almost abiotic circumstances that often do not have the immediate task of sustaining their own lives. This paper presents the action of biogenic and biogenic−thermogenic microorganisms, which produce methane, alcohols, lipids, triglycerides, and hydrogen, thus often creating renewable energy from waste biomass. Furthermore, some microorganisms acquire new or improved... [more]

A novel three-port converter (TPC) is proposed to meet the diversity of demand for electrical equipment in this paper. It interfaces a single input power port and two output ports. The proposed TPC can be viewed as two bidirectional DC-DC converters. With a different operation mode, the proposed TPC can output two DC voltages or a single DC and a single AC voltage. The topology and operation principal of the TPC is analyzed in detail. Moreover, the mathematic model of the TPC is derived. Then, by considering the dynamic response and disturbance suppression, a step by step PI and PR controller design process for TPC is also presented. Both the simulation and the experimental results validate the proposed method.

Conventional fuels commonly used in cars with combustion engines and the effects of their combustion have a very negative impact on the state of the environment. The combustion of liquid fuels causes the introduction of many thousands of tons of CO2 and other harmful substances into the atmosphere every year. That is why the authorities of many countries are introducing more and more stringent emission standards for cars with internal combustion engines, and car manufacturers are trying to meet these standards. Therefore, the aim of the undertaken research was to compile and analyze the power of spark engines in individual capacity ranges, compression ratios, efficiency, CO2 emissions, dependence of combustion on engine capacity, dependence of CO2 emissions on engine capacity, and dependence of combustion on engine power. The conducted research also compared the level of average selected variables related to CO2 emission in terms of engine displacement by country of production using st... [more]

The liquid chemical hydrogen storage technology has great potentials for high-density hydrogen storage and transportation at ambient temperature and pressure. However, its commercial applications highly rely on the high-performance heterogeneous dehydrogenation catalysts, owing to the dehydrogenation difficulty of chemical hydrogen storage materials. In recent years, the chemists and materials scientists found that the supported metal nanoparticles (MNPs) can exhibit high catalytic activity, selectivity, and stability for the dehydrogenation of chemical hydrogen storage materials, which will clear the way for the commercial application of liquid chemical hydrogen storage technology. This review has summarized the recent important research progress in the MNP-catalyzed liquid chemical hydrogen storage technology, including formic acid dehydrogenation, hydrazine hydrate dehydrogenation and ammonia borane dehydrogenation, discussed the urgent challenges in the key field, and pointed out t... [more]

The Carboniferous reservoir KT-II layer in the Eastern margin of the Pre-Caspian Basin was formed in the open platform sedimentary environment and marked by a complicated pore-throats structure. Understanding the main controls on the carbonate reservoir quality is of great significance for reservoir classification and a relevant production prediction. This study focuses on revealing reservoir pore-throats structure’s fractal characteristics by analyzing the mercury intrusion capillary pressure (MICP), with the integration of the pore-throats radius’ distribution data. The relationship between fractal dimensions and reservoir parameters such as physical properties, mercury median saturation pressure (Pc50) and the proportion of large-size (radius > 0.1 μm) pores demonstrate that the lower fractal dimension corresponds not only to core plug samples with higher permeability, but also to lower Pc50 and a higher proportion of large pore-throats. Three classes of carbonate reservoir with dif... [more]

The boiler is an essential energy conversion facility in a thermal power plant. One small malfunction or abnormal event will bring huge economic loss and casualties. Accurate and timely detection of abnormal events in boilers is crucial for the safe and economical operation of complex thermal power plants. Data-driven fault diagnosis methods based on statistical process monitoring technology have prevailed in thermal power plants, whereas the false alarm rates of those methods are relatively high. To work around this, this paper proposes a novel fault detection and identification method for furnace negative pressure system based on canonical variable analysis (CVA) and eXtreme Gradient Boosting improved by genetic algorithms (GA-XGBoost). First, CVA is used to reduce the data redundancy and construct the canonical residuals to measure the prediction ability of the state variables. Then, the fault detection model based on GA-XGBoost is schemed using the constructed canonical residual va... [more]

The conventional fracture in shale hydraulic fracturing belongs to the type-I fracture, and the size of the fracture process zone (FPZ) is an important index to measure the fracability of rock mass. This index is also one of the feasible entry points to study the complexity of the fracture network. In order to visually observe the type-I FPZ at the tip of shale fractures, and to study the relationship between the mechanical properties, the shape and size of the FPZ, and the bedding structure, Notched Semi-Circular Bend (NSCB) tests were conducted with three typical fracture direction-bedding orientations (splitter, arrester, divider). The digital image correlation (DIC) method was used to realize the intuitive observation of the real fracture process and the FPZ near the fracture tip. The test found that the FPZ of shale is narrow and long as a whole and is “flame-like”. The height-to-length ratio of the FPZ at the fracture tip determines whether bending and deflection happen between t... [more]

Thermal energy storage integration using phase change materials (PCMs) in buildings has great potential for energy conservation and greenhouse gas (GHG) emission reduction. Cutting-edge research and innovative ideas are required when using multilayered PCMs within typical construction materials to take advantage of their heat storage capability over a wide temperature range within buildings. This current study was carried out to experimentally test the efficacy of using dual PCMs RT28HC and RT21HC with different melting temperature ranges (28 °C and 21 °C) under variable thermal loading. The transient thermal response of various PCM-based configurations of concrete and cement blocks at different temperature inputs was obtained to determine the effectiveness of dual PCMs and their optimized configuration under experimental laboratory conditions. The range of the temperature input was varied from 22 °C to 50 °C, suitable for hot climatic conditions such as those in Pakistan. Laboratory a... [more]

This study presents an adaptive proportional-integral (PI) and radial basis function neural network proportional-integral-derivative (PID) current control solution for permanent magnet synchronous motor (PMSM) drives. The proposed controller includes four controls: a decoupling term, a PI term, a supervision term, and a radial basis neural network-PID (RBFNN-PID) term. The first control term makes up the nonlinear factors, the second automatically adjusts the control gains, the third guarantees the system stability, and the fourth optimizes the PID parameters to achieve optimal system performance. Unlike off-line tuned PID controllers, the adaptive controller includes an adaptive tuning method for the on-line adjustment of control gain based on the gradient descent strategy. Therefore, it can be adjusted and handle the uncertainty of any system parameters. The program is not only simple and easy to be implemented but also ensures the accuracy and rapidity of the tracking speed. The con... [more]