With the development of intelligent coal mine construction, China’s coal production safety has been greatly improved, but coal mine gas explosion accidents still cannot be completely avoided and the unsafe acts of miners are an important cause of the accidents. Therefore, this study firstly collected 100 coal mine gas explosion cases in China, improved the framework of human factors analysis and classification system (HFACS) and used it to identify the causes of miners’ unsafe acts in detail. A hierarchy of the impacting factors is established. Then, combining with the interpretive structural model (ISM), the correlation between the impacting factors among different levels, especially among non-adjacent levels, is qualitatively analyzed through expert judgment. Then, the correlation among the contributing factors was quantitatively tested by chi-square test and odds ratio (OR) analysis. On this basis, a Bayesian network (BN) is constructed for the impacting factors of miners’ unsafe ac... [more]

Based on the engineering background of providing advance support for the working face of mining roadways, this paper studies the reasonable support technology of advance roadway roofs by combining theoretical analysis, numerical simulation, and field tests. Based on the geological conditions of the 1304 working face of Yineng Coal Mine, the FLAC3D numerical simulation software was used to compare and analyze the effects of the original single hydraulic prop advance support and the bolt-mesh-cable support without the single hydraulic prop. The results show that although the deformation of the surrounding rock is reduced under the support of the single hydraulic prop, the convergence of the roof and floor of the roadway and the left and right sides are still as high as 288 mm and 308 mm, respectively, which does not meet the requirements for safe production. Based on this problem, this study proposes full-stress anchoring technology. FLAC3D numerical simulation software is used to simula... [more]

On the one hand, the twin perspectives of the construction industry and urban agglomeration proliferate economic prosperity. However, on the other hand, construction activities and increased population density give rise to environmental challenges. This study is an initial attempt to explore links between the construction industry, urban agglomeration, non-renewable energy utilization, carbon dioxide emissions (CO2e), and economic output within a system of simultaneous equation modeling. This study develops modeling specifications to include the construction industry as a shifting factor and CO2e as a determinant of technical efficiency. A heterogeneous fully modified ordinary least squares (FMOLS) technique, capable of providing concrete empirical outcomes even in the presence of modern panel-data econometric issues, is utilized for the data of China’s 30 provincial/ city divisions during the 2003−2019 period. It has been revealed that: (i) the influence of urban agglomeration on the... [more]

Carbon dioxide (CO2) is one of the main greenhouse gases and the major factor driving global climate change. From the viewpoint of abundance, economics, non-toxicity, and renewability, CO2 is an ideal and significant C1 resource, and its capture and recycling into fuels and chemical feedstocks using renewable energy is of great significance for the sustainable development of society. Electrochemical CO2 reduction reactions (CO2RRs) are an important pathway to utilize CO2 resources. Zinc has been demonstrated as an effective catalyst for CO2RRs. Numerous studies have focused on improving the efficiency of zinc-based catalysts by tuning their morphology and components, as well as controlling their oxidation states or doping. However, only a handful of reviews have evaluated the performance of Zn-based CO2RR electrocatalysts. The present review endeavors to fill this research gap and introduces the recent progress in using CO2RRs to create various fuels (carbon-containing substances or hy... [more]

At present, the carbothermal reduction and nitridation process is an important method for the large-scale preparation of aluminum nitride powder in industry, but the tremendous energy consumption caused by long-term high temperatures seriously restricts its practical application. To solve this problem, the (NaAlO2+C) mixture with a mole ratio of NaAlO2:C = 1:3 was prepared based on sodium aluminate and carbon black which has been ball milled with anhydrous ethanol as a grinding liquid. The crystal structure evolution and nitridation reaction behavior of sodium aluminate at 800−1600 °C under a nitrogen atmosphere in the presence of carbon were systematically studied employing XRD, SEM, and ICP-MS. The results showed that: high energy θ-Al2O3, η-Al2O3 can be excited by heating sodium aluminate to 1400 °C under a nitrogen atmosphere in the presence of carbon. The transformation process between sodium aluminate and aluminum nitride is carried out via the direct nitridation of θ-Al2O3, η-Al... [more]

To solve the safety hazard of a buried gas pipeline caused by subsidence of a mined-out area, a three-dimensional model of a buried pipeline in a mined-out area was established using geological parameters and the finite-element software ABAQUS. The effects of the friction coefficient of the pipe and soil, the coal-seam dip angle, and the horizontal angle on the mechanical behavior of the pipe under varying widths of goaf area were investigated. The results indicate that the maximum equivalent stress of the pipeline is negatively correlated with the horizontal angle. Concerning longitudinal mining, the pipeline exhibits a high-stress zone when the mining length is >200 m, the surface displacement appears in a small range when the mining length is 40 m, and the stratum displacement range increases gradually with the increase in the mining length. When the width of the goaf is constant, the maximum equivalent stress of the pipeline is positively correlated with the tube-soil friction coef... [more]

Based on the solid−liquid two-phase flow model, SST k-ω model, and Lagrangian equation model of particle motion, numerical simulations of the sediment−water flow in the injector of a large Pelton turbine were conducted. The distribution rules of pressure, velocity, erosion rate, and erosion location of the injector were obtained by analyzing the sediment−water flow characteristics and sediment erosion distribution characteristics of the injector. The results revealed that the velocity distribution trend of the water inside the cylindrical jet exhibited a nonlinear distribution, and the phenomenon of “velocity deficit” occurred at the end of the needle guide and needle tip, resulting in a decrease in the jet quality of the injector. The sediment particle diameter affected the erosion rate of the needle and erosion location of the needle and nozzle port ring. This study provided guidance for sediment erosion analysis and the prediction of the utility of large Pelton turbines.

This study proposes a new isolated intelligent adjustable buck-boost (IIABB) converter with an intelligent control strategy that is suitable for regenerative energy systems with unsteady output voltages. It also serves as a reliable voltage source for loads such as battery systems, microgrids, etc. In addition, the hill climbing (HC) maximum power point tracking (MPPT) algorithm can be utilized with this innovative IIABB converter to capture the MPP and then enhance system performance. In this converter, five inductors (LA, LB, LC, LD, and LE) and four power MOSFETs (SA, SB, SC, and SD) are used in the proposed novel isolated intelligent adjustable buck-boost (IIABB) converter to adjust the applied voltage across the load side. It also has a constant, stable output voltage. The new IIABB converter is simulated and verified using MATLAB R2021b, and the performances of the proposed IIABB converter and conventional SEPIC converter are compared. The solar photovoltaic module output voltage... [more]

Renewable energy power prediction plays a crucial role in the development of renewable energy generation, and it also faces a challenging issue because of the uncertainty and complex fluctuation caused by environmental and climatic factors. In recent years, deep learning has been increasingly applied in the time series prediction of new energy, where Deep Belief Networks (DBN) can perform outstandingly for learning of nonlinear features. In this paper, we employed the DBN as the prediction model to forecast wind power and PV power. A novel metaheuristic optimization algorithm, called swarm spider optimization (SSO), was utilized to optimize the parameters of the DBN so as to improve its performance. The SSO is a novel swarm spider behavior based optimization algorithm, and it can be employed for addressing complex optimization and engineering problems. Considering that the prediction performance of the DBN is affected by the number of the nodes in the hidden layer, the SSO is used to o... [more]

Fixed-bed pyrolysis of torrefied spruce wood, for a heating temperature of 800 K, results in char yields between about 27−57 wt% (versus 23 wt% for untreated wood), depending on both pre-treatment temperatures (533−583 K) and holding times (8−25 min). In this study char oxidation behavior and kinetics are investigated by means of thermogravimetric analysis. The differential thermogravimetric curves always showed a low-temperature zone of slow rates (oxidative devolatilization), followed by a high-rate zone with a well-defined peak (oxidation). As the torrefaction severity increases, the temperature range of the oxidative devolatilization enlarges. Moreover, the oxidation rates become slower (both burning and burnout temperatures tend to increase). As already found for untreated wood chars, the two stages are well described by a linear and a power-law rate reaction, respectively. Volatiles released from the devolatilizations are approximately around 20 wt%, but torrefaction causes lower... [more]

Composites of sawdust and crushed polyethylene were obtained by pressing at 5−10 atm. The resulting pellets with a size of about 10−20 mm were then burned in airflow in a muffle furnace at a temperature of 800 °C. The combustion process was recorded, and obtained video data were analyzed. The data obtained made it possible to estimate the change in particle size at different stages of combustion. An increase in linear dimensions during conversion was achieved of up to 2 times. Particle swelling led to a decrease in mechanical strength and destruction of particles before complete burnout.

Jordan’s energy situation is in a critical state of dependency, with the country relying heavily on imports to satisfy its ever-increasing energy requirements. Renewable energy is a more competitive and consistent source of energy that can supply a large proportion of a country’s energy demand. It is environmentally friendly and minimizes atmospheric pollutant emissions. Thus, bioenergy has the potential to be a crucial alternative energy source in Jordan. Biomass is the principal source of bioenergy; it accounts for approximately 13% of the primary energy demand and is anticipated to supply half of the total primary energy demand by 2050. Nanotechnology has emerged as an important scientific research area with numerous applications, including biofuels. This review summarizes the application of nanoparticles to improve the properties and processes of biofuels. It presents the availability and viability of nanotechnology-supported bioenergy production in Jordan. Jordan generates up to 5... [more]

Drying has been widely studied as a necessary process in biomass utilization. The steam diffusion law plays an important role in drying kinetics. The drying kinetics of a single biomass particle using Fick’s second law of diffusion was studied in this paper. A parabolic relationship appeared between the critical moisture content and temperature. The critical moisture content decreased with the increase in drying temperature and the initial moisture content. The drying temperature had a significant effect on the effective diffusivity and coefficient of mass transfer during the dramatically falling period of the biomass drying process. However, it was affected by the effective diffusivity and coefficient of mass transfer during the slowly falling period. The initial moisture caused the opposite effect during the different periods. The normalized biomass moisture content generally increased with the increase in drying temperature, and decreased with the increase in initial moisture conten... [more]

During the service of a landfill, uneven soil settlement and earthquakes can cause changes to the pore structure and cracks in the covering layer. The use of a biochar−methanotroph−clay mixture as a new landfill covering layer, can improve its engineering properties. The biochar−methanotroph−clay mixture’s shear-wave velocity and compression-wave velocity were measured by the bender−extender element test, and the elastic parameters under small-strain conditions, such as maximum shear modulus, Gmax, maximum constrained modulus, Mmax, and Poisson’s ratio, ν, were obtained. The parameters showed that the elastic characteristics and lateral deformation capacity were of great significance for settlement, seismic field, and stress−strain analysis. Based on the bender−extender element test, the effects of different compaction degrees, and biochar content on Gmax, Mmax, and ν of the biochar−clay mixture, and different methane cultivation days on the biochar−methanotroph−clay mixture, were inve... [more]

The formation of a rich underground-seam network is the key problem in the development of low-permeability hot dry rock (HDR) resources. Considering the lack of macroscopic continuum theory to study hydraulic fracturing having preset fracture-interface element, the particle-flow method of micro-mechanical discrete-element theory is introduced to simulate the mechanical behavior of hydraulic fracturing for HDR low permeability reservoirs. The reservoir is simulated as a round particle; the fracturing fluid movement is described by the seepage field equation, and rock movement is described by the displacement field equation. Finally, the particle-flow numerical model of hydraulic fracturing for HDR low permeability reservoirs is established under the condition of fluid-solid coupling: the model contains two parts (rock and fracture). Based on the parallel-bond model, a definition of micro-fractures of hydraulic fracturing is given. The relation between the fracturing effect and influence... [more]

The paper presents the possibilities of low-emission-powered vehicles based mainly on compressed hydrogen. It shows currently used forms of powering vehicles based on their genesis, process of obtention, and popularity. They are also compared to each other, presenting the advantages and disadvantages of a given solution. The share of electricity in transport, its forecasts for the future, and the possibilities of combination with conventional energy sources are also described. Based on current technological capabilities, hydrogen plays a crucial role, as presented in the above work, constituting a fundamental basis for future transport solutions.

Wettability in CO2-brine-mineral/rock systems is an important parameter influencing CO2 storage capacities and leakage risks in saline reservoirs. However, CO2 tends to react with various minerals and rocks at subsurface conditions, thus causing temporal and spatial wettability changes. Although many relevant research works have been published during past years, a thorough overview of this area is still lacking. Therefore herein, reaction-induced wettability changes are reviewed, and the underlying mechanisms are discussed. Current research gaps are identified, future outlooks are suggested, and some conclusions are drawn. The fundamental understanding of reaction-induced mineral and rock wettability changes during CO2 storage in saline reservoirs is analyzed and the guidance for long-term CO2 containment security evaluations is provided.

The possibilities for reducing the fuel consumption of internal combustion engines focus mainly on developing combustion systems, as one such solution is a two-stage combustion system using jet ignition. The combustion of gaseous mixtures with a high excess air ratio leads to an increase in overall efficiency and a reduction in the emissions of selected exhaust components. In such a convention, gas combustion studies were conducted in the methane/propane configuration. Using an active prechamber where spark plugs were placed and direct injection through a check valve, the fuel dose was minimized into the prechamber. The tests were conducted for a constant center of combustion (CoC). The combustion process in both the prechamber and main chamber was analyzed using a test stand equipped with a 0.5 dm3 single-cylinder engine. The engine was controlled by varying the fuel supply to the prechamber and main chamber in excess air ratio λ = 1.3−1.8. The study analyzed thermodynamic indices suc... [more]

Delamination damage to spar caps seriously endangers the operation safety of offshore wind turbines. The effect of initial delamination of various depths and areas on the ultimate tensile load of laminates is studied based on experiments and numerical simulation, and an effective method for predicting the residual tensile strength of laminates with high thickness is proposed. Three groups of initial delamination specimens with different characteristics were fabricated, and static displacement tensile tests were carried out. An accurate three-dimensional numerical analysis model was established, and the results were in good agreement with the experimental values, with the overall error of the failure load being less than 6%. Furthermore, a numerical model for a 20-ply high-thickness spar cap laminate was established to predict the effect of delamination on tensile strength. The results showed that, for the same depth of initial delamination, the difference in delamination area had littl... [more]

Recently, the demand for small, low-cost electronics has increased the use of cost-effective tiny inductors in power-management ICs (PMICs). However, the conduction loss caused by the parasitic DC resistance (RDCR) of a small inductor leads to low efficiency, which reduces the battery usage time and may also cause thermal problems in mobile devices. In particular, these issues become critical when a conventional boost converter (CBC) is used to achieve high-output voltage due to the large inductor current. In addition, as the output voltage increases, a number of issues become more serious, such as large output voltage ripple, conversion-ratio limit, and overlap loss. To solve these issues, this paper proposed a high-voltage boost converter with dual-current flows (HVDF). The proposed HVDF can achieve a higher efficiency than a CBC by reducing the total conduction loss in heavy load current conditions with a small inductor. Moreover, because in the HVDF, the current delivered to the ou... [more]

Appropriate frequency response is an issue of great importance in power system management, especially in an islanded one. An energy-based method for assessing a system’s response, which is needed to prevent under frequency load shedding (UFLS), is introduced. Renewable generation, such as wind turbine (WT) and photovoltaic (PV) facilities, reduces the ability of the power system to resist power imbalances and increases the risks of consumer disconnections by UFLS system, and even of total collapse. To estimate the amount of additional fast power reserve, an equation was developed, relating the moment of inertia, the system demand dynamics, and the available response of synchronous generating units. Clustering units based on their ability to respond to frequency changes in low inertia conditions allows the potential synchronous response to be assessed, providing information of its deficiency in a defined system state. The proposed method was applied to the Israeli power system and up to... [more]

To date, the majority of energy supply is still generated by non-renewable sources, which places a dramatic burden on our environment [...]

As one of the crucial factors contributing to coal spontaneous combustion, the oxidation of pyrite is a complex process involving multiple reactions, particularly in the presence of oxidants (Fe3+ and O2) and bacteria. However, experimental results based on mineral-pyrite are not entirely applicable to coal-pyrite due to their differences in formation environments and compositions. This study selected two types of coal-pyrite and one type of mineral-pyrite as research to conduct oxidation experiments with the participation of oxidant (Fe3+) and bacteria (Acidithiobacillus ferrooxidans), respectively, to obtain the following conclusions. Under natural conditions, the chemical oxidation rate of pyrite is slow, but the addition of oxidant Fe3+ and bacteria can significantly accelerate the oxidation rate. The promotion effect of oxidant Fe3+ on the oxidation reaction is stronger than that of bacteria. Under the same conditions, the oxidation rate of coal-pyrite samples is slightly higher t... [more]

Electric vehicles (EVs) have the advantage of being resilient to natural disasters. However, users hesitate to donate electricity when they lose the chance to recharge at the utility. Solar electric vehicles (SEVs) save energy through vehicle-integrated photovoltaics (VIPV) and make it possible to voluntarily donate excess energy, thus maintaining facility resilience. Given that the supply of solar energy to VIPV systems is not continuous and is difficult to forecast, the contribution of VIPV to the resilience of the larger energy system has been called into question. This is the first study in which the potential of VIPV to maintain utility resilience is investigated in the context of physical factors, such as irradiance, and social factors. The actual energy yield of a VIPV car was determined using an advanced 3D solar irradiation model under a nonuniform shading distribution, with validation from actual measures of solar irradiance on five orthogonal sides of the car body. The Monte... [more]

To enhance the operational dependability of renewable energy power systems with high proportions, this study proposes a multi-timescale optimization strategy based on the inertia evaluation model. Firstly, the inertia evaluation model is established based on the factors influencing the inertia demand of the power system, and the concept of the inertia margin coefficient is introduced. Secondly, to address the uncertainties associated with sustainable energy output and the cost of carbon emissions, a multi-timescale optimization operation model is formulated for day-ahead, intraday, and real-time operations, aimed at economic optimization. The output status of each unit is obtained and adjusted in a timely manner in the next stage, while meeting the system’s inertia demand, to derive the final scheduling strategy. Lastly, a sensitivity analysis of the inertia margin coefficient is conducted through simulations to validate the effectiveness and cost-efficiency of the proposed scheduling... [more]