Energy Science & Engineering

In the later stages of horizontal gas well development, due to insufficient formation energy, the stratified flow of gas and liquid in the horizontal section generates a decrease in the well's liquid‐carrying capacity, accumulating liquid in the wellbore. Since the flow pattern of gas–liquid two‐phase flow in horizontal wells is significantly different from that in vertical wells, existing vertical well liquid removal and gas production technologies cannot be directly applied to address the liquid accumulation issues in horizontal wells. This paper presents a swirl jet composite device that, through the combination of a spiral guide belt and an internal flow channel, effectively integrates the jet and vortex effects, capable of transforming the stratified flow in the horizontal section into an annular flow, thereby enhancing the gas well's liquid‐carrying capacity. This study applies a combination of theoretical, experimental, and simulation methods to conduct computational fluid dynamics analysis on the device's ability to improve the gas well's liquid‐carrying capacity. It deeply investigates the flow characteristics of the gas–liquid two‐phase flow within the device. The results indicate that the device can not only achieve gas–liquid separation by transforming the flow regime from laminar to an orderly annular flow but also increase the axial velocity to extend the effective distance of the swirling section. Compared with the case without the device installed, the liquid phase volume fraction at the bottom of the well is reduced by 85.9%, and the liquid holdup is reduced by 38%. This demonstrates that compared to traditional technologies such as gas‐lift dewatering and gas production, the device can enhance the liquid‐carrying capacity of horizontal wells and effectively address the issue of liquid accumulation in horizontal wells. It provides theoretical guidance and a practical basis for future research on applying swirl jet composite devices to improve the liquid‐carrying capacity of horizontal wells.

Nima Basin, as a typical Tethys area, is a Cenozoic oil‐bearing basin in the middle of Qinghai‐Tibet Plateau, which is expected to become an important target for petroleum exploration. The main controlling factors and models of organic matter enrichment are not yet clear. To identify the organic geochemical characteristics of high‐quality source rocks and the main controlling factors of their formation, this study analyzes the paleoclimate and paleo‐salinity indexes based on the analysis of the major and trace elements through systematic sampling of the muddy sediments of Niubao Formation in Well Shuangdi 1, Cebuco Depression. The results show that the organic matter of the E1‐2n source rocks in Nima Basin is differentially enriched, which shows that the organic matter of the middle E1‐2n source rocks is more enriched than that of the upper E1‐2n source rocks. Hydrocarbon source rocks of the middle E1‐2n are mainly of type I organic matter, while those of the upper E1‐2n are mainly of type Ⅱ1 organic matter, both of which are in the mature stage. Organic matter enrichment is primarily governed by a combination of climate and redox conditions, with humid climate and reducing environments emerging as the dominant factors, whereas salinity exerts a lesser influence. On the one hand, this study can supplement the accumulation mechanism of organic matter in the Tethys domain in Asia; on the other hand, it will fill the gap in the geological research of Nima Basin, contributing to the prediction and exploration of oil and gas resources in the Nima Basin.

Bolt support mechanisms represent a key technique to support the surrounding rock in coal mines. In deep rock engineering applications, the bolt‐supported structure of the surrounding rock of a deep roadway under high bearing stress may fail under dynamic loads such as those of blasting vibrations and earthquake motion. In this study, dynamic uniaxial compression tests were conducted on steel bar reinforced rock to investigate the rockbolt performance under dynamic loading. The deformation of the specimen surface and rockbolt was recorded during the test. The strengths and failure modes of the bolted rock samples were investigated. The results show that the bolt and rock deform asynchronously when the bolted specimen is subjected to a dynamic load, and the time of the asynchronous deformation of the specimens with different bolt angles is considerably different. When the stress wave acts along the direction of the bolt, it is more likely to cause the failure of the bolted specimen. Anchorage agents should be employed to realize the synchronous deformation of the bolt and rock mass. The slip and dislocation of the anchorage agent/rock surface and anchorage agent/bolt interface are the key factors influencing the failure of bolted specimens. The influence of a dynamic stress wave on the surrounding rock support structure of a deep roadway can be effectively reduced by improving the antisliding characteristics of the anchoring agent and increasing the bolt density. The research results can provide theoretical guidance and serve as a reference to realize the reinforcement engineering of underground permanent chambers and roadways.

CCUS‐enhanced oil recovery (EOR) technology relies on the unique properties of CO2 gas in the process of efficient oil displacement while achieving effective storage, which has become one of the most economical and effective measures for reducing greenhouse gas emissions in today's society and is important for helping to realize the global strategic goal of carbon neutrality. Based on previous research results, this review presents the oil displacement and geological storage mechanisms of CO2 in micropores in the oil and gas fields, and summarizes their respective influencing factors. At the same time, it also summarizes the current research status of CO2‐EOR and geological storage from the perspectives of laboratory experiments and numerical simulations. Moreover, it provides a detailed overview of four key technologies namely, miscibility improvement, swept volume expansion, storage potential assessment and storage safety monitoring, and their field applications. On this basis, this review compares the development status of field applications in Developed Countries and China, analyzes the problems of CCUS‐EOR technology in theoretical research, technology research and development and project industrialization, and points out the future development directions. Results are presented that research on CO2‐EOR and geological storage in Developed Countries such as the United States started early and developed rapidly. A relatively complete industrial chain system has been formed, and the scale and number of CCUS‐EOR projects are far ahead those in China. In China, relevant research started relatively late and developed slowly at the early stage. In recent years, due to the notable attention given to climate change and carbon storage, development efforts in China have gradually intensified. At present, there are more than 20 large‐scale CCUS‐EOR demonstration projects in operation, which are preliminarily ready for industrial promotion. Notably, the world has continued to increase its attention to CCUS‐EOR projects based on national conditions, further improving policy guidance mechanisms, strengthening research and development efforts, promoting the construction of the full‐process industry chain, achieving large‐scale and refined development, and providing theoretical guidance and technical support for realizing the strategic goal of carbon neutrality.

Demand response schemes play a vital role in managing the load demand. However, the demand response applicability is pre‐descriptive where loads to be managed are pre‐selected majorly based on the availability of renewable energy and lower tariff rates. However, in hospitality buildings such as hotels, user comfort cannot be compromised by the cost of energy. The arrival of guests is a unique parameter that drives the load consumption regardless of the availability of free energy or lower tariff rates. During higher guest arrivals, pre‐descriptive loads meant to be scheduled during low renewable energy availability and higher tariff rates cannot be compromised over guest comfort. Similarly, pre‐descriptive loads that are already not in operation at the time of low guest arrivals will result in wastage of green power at times of its availability. There is a need to develop an automated demand response that has the liberty to select any load for shifting to renewable energy based on the power they consume to utilize maximum resources without compromising guest comfort. In this research, a novel automated demand response scheme is developed that intelligently selects any load from the building in real time while mapping it with the available capacity of renewable power. A cascaded fuzzy integrated knapsack algorithm is designed for intelligent selection of loads participation in demand response. Based on the availability of solar PV power, grid rates, and load operations, fuzzy designates values to the random operational loads. In the second step, the designated values are given to the Knapsack algorithm to find the best optimal responsive loads to be operated at that time. In the proposed approach, random loads were selected for shifting to renewable power without any prior load selection, which enhances the operation and usability of solar PV power. It was found that 88%–100% of solar PV power was utilized under all simulated scenarios of operation.

In recent years, energy storage technology has developed rapidly with the aim to promote the development of renewable energy sources and establish a green and sustainable energy structure. A novel compressed CO2 energy storage system based on Gua2SO4 adsorption is proposed in this study. Gua2SO4 has low sorption enthalpy and mild physical conditions in the adsorbent and desorption process, which are very beneficial for reducing the design difficulty of low‐pressure gas storage devices and improving the system performance. The energy and exergy analysis models are conducted after establishing several assumptions. The round trip efficiency, energy density, CO2 capture unit volume and liquid CO2 tank volume are 68.8%, 12.6 kWh/m³, 44,208 m³ and 19,235 m³ under design conditions, respectively. In addition, according to the exergy analysis, the liquefaction unit and compression unit have the highest exergy destructions. The monotonic increase in high‐pressure cooler end temperature difference and ambient temperature will cause the system efficiency to show a trend of first increasing and then decreasing. The liquid CO2 tank temperature and throttling pressure have a trade‐off relationship on system performance. It should be noted that when the throttling pressure is below a certain value and the liquid CO2 tank temperature is above a certain value, the system efficiency will sharply decrease. Moreover, increasing compressor and turbine efficiency has a conducive effect on improving system efficiency while the growth of heat exchanger pinch temperature and pressure loss rate have a negative influence to that.

Battery‐ and hydrogen‐powered trains are emerging technologies that have the potential to play a key role in the decarbonization of railway lines for which full trackside electrification is not feasible. In this study, we examine Pareto‐optimal energy supply concepts for a specific location along the Cologne–Gerolstein railway line. We investigate two supply concepts, one for battery trains making use of overhead line islands (OHLIs), referred to as the OHLI supply concept, and another for hydrogen trains that make use of hydrogen refueling station (HRSs), referred to as the HRS supply concept. The public grid, as well as renewable energy sources such as wind and PV energy, are considered sources of electrical energy supply. The sizing of these takes into account storage technologies and load time series specific to each supply concept. Simulation models are defined to evaluate the characteristics of an OHLI and HRS supply concept located in a small town (Gerolstein, Germany). Our findings indicate that the HRS supply concept results in more than twice the cost per MWh (111%/MWh higher) compared to the OHLI supply concept. However, the HRS supply concept achieves a 24.7% higher degree of self‐sufficiency. Furthermore, the HRS supply concept requires a larger energy system in terms of installed renewable power and storage capacity. This enables the HRS to supply the entire line with energy, whereas the OHLI supply concept covers only a share of the overall energy demand of battery trains at the location under consideration. The remaining energy demand is covered by existing overhead lines or OHLI at another location.

Rolling bearings are fundamental components of contemporary machinery, yet their prolonged usage frequently leads to wear, performance deterioration, and potential faults. In scenarios characterized by limited sample sizes and complex, noisy environments, traditional diagnostic methods often encounter difficulties achieving satisfactory fault identification results. To address these challenges, this study introduces an innovative approach for rolling bearing fault diagnosis. Initially, the black‐winged kite algorithm (BKA) is enhanced through the integration of a differential evolution strategy and an iterative search method, enabling the precise determination of optimal parameters for variational mode decomposition (VMD). Subsequently, a comprehensive index evaluation criterion is established to identify the optimal signal components, which are then subjected to a detailed analysis to extract diverse sensitive features, ultimately forming a hybrid feature set. To further improve the accuracy and efficiency of fault diagnosis, this study proposes an enhanced extreme learning machine model, termed twin extreme learning machine (TELM). Moreover, the TELM model is seamlessly integrated into the architecture of a convolutional neural network (CNN), specifically as a component of its output layer, resulting in a novel hybrid fault diagnosis model. Rigorous data validation performed on a rolling bearing testbed underscores that the proposed fault diagnosis model significantly surpasses conventional approaches, including SVM, KELM, ELM, LSTM, and softmax, in terms of accuracy, recall, and F1 score. Notably, the model maintains robust fault diagnosis capabilities even in environments with varying degrees of noise interference.

Current concentrating solar power (CSP) systems operate below 550°C, achieving annual electricity generation efficiencies of 10%–20%, which primarily employs nitrate molten salts as heat transfer fluids (HTFs). However, nitrate salts decompose at temperature exceeding 600°C, rendering them unsuitable for next‐generation CSP systems, which aim to operate above 700°C. This review presents the first comprehensive analysis of high‐temperature molten salts for third‐generation CSP systems. This highlights the potential of carbonates, chlorides, and sulfates as HTFs due to their extended operational temperature ranges. Guided by phase diagrams, multicomponent molten salts are systematically engineered to achieve desirable thermal properties. The review provides a detailed synthesis of compositions and working temperature ranges for these molten salts, with a particular focus on underexplored sulfate‐based salts. It consolidates critical data on the melting points and phase compositions of multicomponent sulfates and examines advancements in thermal property enhancements, including the integration of nanoparticles. By summarizing the latest progress and identifying future research directions, this work offers invaluable insights into the design and application of high‐temperature molten salts in next‐generation CSP systems.

This study investigates the viability and benefits of utilizing compressed earth blocks (CEBs) as a sustainable construction material under varying climatic conditions, focusing on two cities in Saudi Arabia: Riyadh, representing a hot desert climate, and Abha, representing a cooler, high‐altitude climate. A comprehensive simulation‐based methodology was employed, which included energy performance modeling and optimization using EnergyPlus software, climate data analysis, environmental impact assessment, and cost analysis. To further verify the results, the EnergyPlus simulations were validated using a machine learning model, specifically the gradient boosting regressor (GBR), to ensure accuracy and reliability. The simulations demonstrate that CEBs provide substantial benefits in terms of structural performance, energy efficiency, and sustainability. For instance, CEB buildings showed reduced cooling loads by 35% in Riyadh and 25% in Abha, while also maintaining high indoor air quality and thermal comfort, leading to 80‐85% occupant satisfaction. The use of CEBs contributed to significant reductions in carbon emissions, with 90% renewable materials, and proved to be cost‐effective over the long term. The GBR validation confirmed less than 2% variation from the EnergyPlus simulations, further ensuring the reliability of the results. Environmental impact assessments revealed substantial reductions in carbon emissions, resource consumption, and waste generation through the adoption of CEBs. Although the initial cost of CEBs may be slightly higher than traditional materials, the long‐term energy savings and reduced maintenance costs make them an economically viable option, particularly in regions with extreme climates. This study underscores the potential of CEBs as a versatile, efficient, and sustainable building material, offering significant benefits in energy efficiency, environmental impact reduction, cost‐effectiveness, and occupant comfort—all based on robust simulation and modeling results.

As urban areas expand, energy demands are escalating, necessitating the development of urban energy systems (UES) to achieve energy conservation and emission reduction goals. Although small‐scale regional integrated energy supply technologies have reached a level of maturity, urban‐scale integrated energy supply solutions are still in development. In response, this study introduces an architecture for the UES and an economic and low‐carbon operation strategy. The approach begins by constructing a highly reliable and robust integrated energy system (IES) within each independent region to accommodate a variety of energy needs, followed by the establishment of an operational architecture for large‐scale urban energy systems. The study then examines the energy flow and the mathematical model of multiple energies within urban energy systems, simplifying the complex model for practical application. Subsequently, a multiobjective optimization model is developed to facilitate the large‐scale consumption of clean energy, with considerations for economic and low‐carbon operations, and is formatted into a linear programming model. The model's accuracy is empirically tested through numerical simulation in a city divided into three regions. The simulation results demonstrate substantial improvements in clean energy consumption, a reduction in carbon emissions, and a decrease in operational costs. Specifically, the proposed strategy can boost the clean energy consumption rate to 96.41%, cut operational costs by up to 50.13%, and lower carbon dioxide emissions by up to 57.59% compared to traditional technologies. These findings robustly validate the methodology's effectiveness, paving the way for more sustainable urban energy management practices.

The number and spacing of boreholes drilled along a coal seam are important parameters of the borehole layout. Despite the previous extensive research by many experts, quantitative and visual comparisons of the gas extraction effects with different borehole spacings and numbers are rare. Here, the effective gas extraction range, delimited by the 0.74 MPa isobaric surface and lines, was simulated. The 0.74 MPa isobaric surface around multiple sets of boreholes at 60 days of gas extraction is wavy. At 50 days, the isobaric lines around a single set of boreholes are approximately circular, whereas those around multiple sets of boreholes are approximately elliptical. When five sets of boreholes are used, the short semiaxis of the elliptical contour around the middle borehole is approximately 59% greater than the effective extraction radius of a single borehole. Among the spacings investigated, the effective extraction volume V5 peaks at a borehole spacing of 5 m at 90 days; but, the isobaric lines at the top and bottom of the working face are concave inwards, that is, certain gas pressures exceed 0.74 MPa, thereby increasing the likelihood of gas emissions. Thus, at 90 days, the efficiency of gas extraction in this studied working face is higher as the borehole spacing is 4 m. This approach, which takes into account the superimposed effect of boreholes drilled along a coal seam, the radius of gas extraction, isolines, isobaric surface and the effective extraction volume, offers theoretical guidance for the arrangement of boreholes.

The identification of coal and gas outburst risks is crucial for the safe production of coal mines. The application of deep learning techniques in this domain shows significant promise, particularly in small sample scenarios. This paper investigates the use of transfer learning and self‐supervised learning strategies in static outburst risk identification models under small sample data scenarios. A TabNet‐based model was utilized, focusing on performance improvements achieved through pretraining, particularly with respect to recall rate and false negative rate. The model was pretrained using a combination of self‐supervised and supervised learning to enhance adaptability and generalization capabilities for small sample data scenarios, followed by evaluation with stratified fivefold cross‐validation. Experimental results demonstrated that the pretrained TabNet model significantly outperformed the non‐pretrained model as well as traditional machine learning models, including random forest, XGBoost, LightGBM, SVM, and MLP, in terms of accuracy and stability. Furthermore, removing features with weak correlations to the target variable further improved model performance, emphasizing the importance of integrating various learning strategies during data preprocessing and model training, particularly in limited data contexts. Model interpretability was also analyzed using SHAP and TabNet's inherent interpretability, confirming consistent feature importance rankings and highlighting the model's robustness and reliability.

On the basis of the structure of the traditional electromagnetic injector, this paper proposes a new type of electromagnetic injector structure by changing the opening mode of the control valve. Taking the fuel injection consistency and response time as the evaluation indexes, a one‐dimensional simulation model was established to compare the fuel injection performance of the traditional electromagnetic injector and the new electromagnetic injector. For the new electromagnetic injector, the structural parameters of the control valve were optimized by orthogonal analysis. The results show that: compared with the traditional electromagnetic injector, the new electromagnetic injector had better multicylinder fuel injection consistency and more stable fuel injection quantity, but the opening delay, opening time, closing delay, and injection duration were increased by 30.77%, 11.14%, 33.46%, and 0.44%, respectively. The closing time was decreased by 8.55%, which was due to the change in the force and motion of the control valve body. After optimization, the response delay time of the injector was decreased and the fuel injection consistency became better. The opening delay, opening time, closing delay, and injection duration were decreased by 10.08%, 10.03%, 14.72%, and 4.57%, respectively; the closing time was increased by 3.42%. The average injection volume was decreased by 5.57%, and the variance value of fuel injection volume was decreased by 41.03%.

To better understand the properties of low rank coals, especially the correlation information between the trace elements (TEs) and minerals, four typical low‐rank coals in China, namely Xiaolongtan (XLT), Shenbei (SB), Huolinhe (HLH), and Shengli (SL) were quantitatively studied for their mineralogical characteristics and TEs distributions, to provide a basis for proposing methods to remove impurities from low‐rank coal and reduce environmental pollution. Results show that light mineral fractions (LMFs, ρ < 2.89 g/cm³) are more than 90% (wt.%) in the four low‐rank coals with clay minerals dominating in composition. Minerals in the heavy mineral fractions (HMFs, ρ > 2.89 g/cm³) vary from coal to coal. Rare heavy mineral particles including zircon, sphalerite, and gypsum are observed in HMFs from four low‐rank coals. Minerals are the major carriers of the TEs, and different kinds of minerals carry different kinds of TEs. TEs such as Cu, Zn, Tl, As, Cd, Sn, Ni, Sb, Pb have an affinity to occur in pyrite; Gd, Sr, Ba, Eu, and Bi are associated with barite; Cr, Mo are abundant in Fe‐bearing carbonate.

The seepage and heat transfer characteristics of fractured rock are critical issues in hot dry rock exploitation. This paper investigates the effects of proppant on the seepage characteristics under different conditions through seepage experiments on split granite fractures. Subsequently, seepage–heat transfer coupling mechanisms in fractured granite are elucidated through numerical simulations. The results indicate that the flow rate increases in fractures with large crack widths as temperature rises, while in fractures with small crack widths, an increase in temperature reduces the flow rate. Additionally, normal constraint force increases with rising confining pressure, consequently reducing the flow rate. Extension of seepage paths is favored by higher injection pressures, thereby improving flow rates. The inclusion of proppant effectively supports the fracture, expanding its width and significantly increasing the flow rate. Furthermore, injection into the reservoir forms a low‐temperature cooling zone, which gradually advances towards the outlet over time. Initially, the outlet temperature and extract heat rate remain stable before decreasing almost linearly. Proppant filling accelerates the heat transfer rate and significantly boosts the initial extract heat rate; however, it also leads to a faster decline in reservoir heat quantity, resulting in a subsequent extract heat rate lower than that of unfilled fractures. These findings underscore the importance of balanced extract heat efficiency and enhanced geothermal system reservoir longevity for the sustained exploitation of geothermal energy.

In this article, a new single‐switch high step‐up DC/DC converter with soft‐switching performance is presented for sustainable energy applications. In this circuit, zero input current ripple is obtained at a small value of the input inductance. Therefore, the ohmic loss of the input inductor will be significantly alleviated. Also, a three‐winding coupled‐inductor (TWCI) and a voltage multiplier are merged in this topology to achieve high voltage gain with an appropriate duty cycle. Semi‐trans‐inverse specification of this circuit makes it possible to achieve high output voltages under a lower magnetic turns ratio, which leads to power loss reduction. Moreover, a regenerative clamp recycles the leakage energy to the output and also mitigates the maximum voltage stress across the power switch. In addition, to help further efficiency improvement, a resonant tank with a quasiresonant performance between the middle capacitors and the leakage inductance of the TWCI is adopted to decrease the power dissipations of the switching components. The operating principle and steady‐state analysis of the introduced converter are described in detail. To verify the superiority of the presented circuit, a comparison with relevant converters is provided. Eventually, the theoretical analysis was verified by a 300‐W experimental prototype.

Because of their greater accident tolerance, iron‐chromium‐aluminum (FeCrAl) alloys hold great promise for applications in nuclear fuel claddings. Here, a finite element‐based computational framework is developed to analyze the thermomechanical performance of APR1400 fuel rods with FeCrAl claddings subjected to a typical LOCA condition preceded by 4 years of normal operation. The effect of enhancements in the yield and ultimate strength of FeCrAl on the burst safety of fuel rods is evaluated for various choices of pellet diameters and cladding thicknesses. The pellet diameter is increased by reducing the cladding thickness and/or the pellet‐clad gap thickness with the intention of compensating for the additional neutronic penalty of FeCrAl in comparison to the conventional Zircaloy. It is found that a reduction of the pellet‐clad gap thickness from 83 to 50 μm can increase the cladding's burst safety by up to 35%. Additionally, strengthening FeCrAl alloys has significantly improved cladding performance under LOCA (Loss of Coolant Accident) conditions. Specifically, an 80% enhancement in the yield and ultimate strength has been shown to improve the cladding burst safety by 80%. The findings of this study suggest that improved material properties and geometric modifications can significantly improve the burst safety of FeCrAl‐based ATF systems, which is an important consideration for their practical implementation.

Agrovoltaics, also known as Agri‐PV or AV, is an innovative approach that entails the shared utilization of land for both the production of agricultural commodities and energy generation. This concept has gained immense popularity in recent times owing to its ability to boost income per unit of land area significantly. The scope of AV systems is quite extensive, as it encompasses solar energy converters and other renewable energy sources like bioenergy. Current strategies for agrovoltaic (AV) in agriculture are the outcome of the gradual development of agroecology and the integration of photovoltaic (PV) power supply into the grid. These approaches could lead to a nearly doubled income per unit area. Without on‐site power supply, reduced chemical fertilizers and pesticides, and on‐site yield processing, AV has the potential to revolutionize large‐scale unmanned precision agriculture and smart farming. These approaches might lead to significant changes in the logistics and value‐added production chain, thereby reducing agriculture's carbon footprint. In the future, it is possible to reduce the cost of AV technology by half by utilizing decommissioned solar panels in the technology and to delay the need for bulk PV recycling by several years. This review presents a different perspective to the common discourse on the topic, by giving special emphasis to the potential to further integrate AV into agriculture, which has the potential to facilitate the resolution of relevant legal disputes over the use of AV.

In this article, a closed‐loop piping system that includes the self‐priming pump is established and calculated. Two operating processes reflecting real situations are accurately calculated by means of UDF. The vortex identification method, entropy production theory, and energy gradient method are employed to deeply analyze and reveal the energy loss characteristics and flow stability. The results show that in the oscillating exhaust stage, the energy loss is greatest during the oscillating exhaust stage of the self‐priming process. The reflux hole, the tongue, and the outlet section of the volute have larger energy loss. Within the impeller region, the entropy production is mainly concentrated at the impeller inlet and outlet; the entropy production distribution area and value are larger in the clearance of the wear‐ring. In addition, the instability region in the impeller and the left side of the volute is significantly larger than the rest of the locations and increases considerably with the self‐priming process.

Prolonged exposure of deep coal mines to erosion from groundwater results in a gradual accumulation of rock mass damage, which can lead to geological hazards such as deformation and instability. These challenges significantly impact the safe operation of deep coal mines. To understand the mechanisms behind siltstone damage progression related to water content and confining pressure, this study explores the influence of these factors on the deformation and damage evolution of siltstone, employing a combination of rock mechanics testing, numerical simulation, and CT scanning techniques. Results demonstrate that increasing water content reduces the compressive strength of rock, leading to more complex failure modes. In contrast, higher confining pressure strengthens the compressive capacity, thereby suppressing the formation and growth of transverse cracks under compression. Using Avizo software, a three‐dimensional model of siltstone was developed to visualize the distribution of fractures in a three‐dimensional field. In the MATLAB platform, a box dimension algorithm based on three‐dimensional digital volume imaging was developed, employing box dimension theory and digital image storage methods. Fractal analysis reveals that the fractal dimension of internal fractures in loaded samples increases linearly with water content, indicating more extensive fracture development and greater specimen damage. Applying the box dimension from three‐dimensional digital volume images as a metric facilitates characterizing the damage evolution in siltstone under different water content conditions. This approach provides a new means to quantitatively evaluate the growth and complexity of internal fractures in siltstone, offering insights into rock damage progression under varying moisture conditions.

Electricity production using fossil fuels contributes to air pollution and adverse health impacts. One option for decreasing fossil fuel consumption is replacing fossil fuel power plants with electricity produced from green hydrogen (H2, produced from renewable sources). Previous studies mainly focused on greenhouse gas emissions from two common H2 production methods, steam methane reforming (SMR) and water electrolysis. This study compares the estimated emissions and associated health outcomes of generating electricity from fossil fuels with electricity generated from H2 produced through SMR or electrolysis in various regions of the United States. Shifting from coal‐generated electricity to SMR‐produced H2‐generated electricity results in health benefits while shifting from natural gas‐generated electricity to electricity generated from H2 generated via water electricity results in health costs in all regions. Depending on the region, replacing a natural gas power plant with electricity generated from H2 produced via SMR or replacing a coal power plant with electricity generated from water electrolysis could result in either health benefits or costs. This study also considers the impact of plant location on human health outcomes as well as the impact of increasing renewable energy percentages on health outcomes associated with replacing a coal or natural gas power plant with electricity generated from H2 produced through grid‐based water electrolysis. The results indicate that a high renewable fraction (over 85% of the grid) is required to experience health benefits, emphasizing the challenges associated with moving toward electrolysis‐based H2 production for electricity generation.

This paper aims to study the frequency‐power coupling dynamic response and regulation characteristics of a variable speed pumped storage unit (VSPSU) with full‐size converter (FSC). Firstly, the mathematical model of VSPSU with FSC is established. Secondly, the dynamic response of VSPSU with FSC under power disturbance is simulated, and the effect of operating speed on dynamic response of VSPSU with FSC is analyzed. Then, the frequency‐power coupling regulation characteristics of VSPSU with FSC are revealed. Finally, the dynamic responses between VSPSU with FSC and fixed speed pumped storage unit (FSPSU) are compared. The results show that, with the same disturbance amplitude, the variation times of speed and output under positive power disturbance are longer than those under negative power disturbance. With a negative power disturbance of larger amplitude, the speed and output of VSPSU have a faster response. The regulation characteristics of VSPSU can be improved by adjusting both the parameters of governor and converter based on the operation requirements. Under both the positive and negative power disturbances, the dynamic response of active power of VSPSU is faster than that of FSPSU. Under the negative power disturbance, the dynamic response of speed of VSPSU is slightly slower than that of FSPSU.

Water‐suspended sediments wear down hydro turbine components by erosion, reducing their lifetime. Nonetheless, even heavily sediment‐loaded rivers are a valuable renewable and clean energy resource. Forecasting sediment erosion and optimizing the hydraulic turbine design for extended durability by numerical flow simulations became imperative to operate the hydropower plant safely and economically in sediment‐laden environments. This strategy is challenged by the unknown model parameters, that is, the lack of reliable validation data. Therefore, in this study, a 2 kW Francis‐type model turbine is tested in a non‐recirculating sediment‐laden test facility. The Francis turbine runner and the guide vanes are coated with four different colors to visualize locations of surface degradation qualitatively due to erosion during operation in representative sediment concentrations. The turbine is tested at two different operating conditions OP1 and OP2 for visualizing the locations of erosion. For operating condition OP1, with low rotational speed, erosion is primarily observed at the leading and trailing edge of the suction and pressure side, respectively. The Francis turbine runner is particularly eroded in the transition between the hub and the blades on the suction side towards the trailing edge. Meanwhile, for operating condition OP2, with higher rotational speed, the trailing edge of the pressure side of the blade and the region of the shroud close to the trailing edge of the blades are found to be vulnerable to erosion. Test for the material erosion of the runner is conducted at OP3 conditions with high sediment concentration over 45 h, reporting the weight loss in intervals of 15 h. It is observed that the cumulative erosion rate of the Francis runner made of brass material is 0.016 mg g⁻¹ h⁻¹ after 45 h of operation. Similarly, the percentage loss of the runner with respect to the hours of operation is calculated to be 0.0065%, 0.04%, and 0.07% for 15, 30, and 45 h of operation, respectively. This data set can also be useful for qualitative and quantitative validation of computational fluid dynamic simulations for erosion prediction.

Both developed and developing countries are affected by the global energy problem. Over the last few decades, the industrial sector's electrical energy demand has grown exponentially, altering the supply‐and‐demand balance. The trend toward Industry 4.0 compliant production facilities necessitates a greater demand for high‐reliability power. Because severe production losses caused by power outages cannot be tolerated, an increasing number of large vital industrial processes integrate centralized high‐quality, online UPS technology onto their network to establish a grid‐to‐load link and continuously condition dirty electricity from the national grid. These facilities distribute electrical power using either an MV or LV system. Based on the integration design, investigating ways to quantify energy efficiency savings of MV versus LV UPS system is required. This paper proposes strategic and technical interventions for these systems and assesses their electrical losses and budgetary ramifications. The paper also aims to contribute to the implementation of an energy efficiency plan and help facilities close power efficiency gaps. From the results obtained, the MV UPS system offers a significant reduction in energy consumption. Compared to the LV UPS system, annual energy losses are reduced by 46% at a load factor of 65%. A significant energy improvement is expected at higher load factors and in larger facilities where longer distribution cables are used. Compared to the LV UPS system, MV UPS saves R221 509 per meter of cable length increase and R31 457 per percentage increase in load factor.