As key supporting equipment in coal mining, hydraulic supports are vulnerable to impact pressure from roof movement and deformation. In this paper, a mechanical-hydraulic co-simulation platform for hydraulic supports is established. Moreover, the rationality of the simulation platform is verified. Based on this platform, the rigid-flexible coupling impact dynamics model of hydraulic support is built. Finally, by delaying the opening time of the relief valve, the energy dissipation problem of the relief valve hysteresis effect on the hydraulic support system under the rotary impact is discussed. The results indicate that the rotary load acting on the hydraulic support decreases gradually with the backward movement of the roof rotary position, which causes the peak pressure in the column to decrease (by 69 MPa). The hinge point load of different parts shows different load transfer laws. The hysteresis effect of the relief valve prolongs the energy release time of the system, increasing t... [more]

Biomass as a clean and renewable source of energy has immense potential to aid in solving the energy crisis in the world. In order to accurately predict the fluidization behavior of biomass particles using the Eulerian−Eulerian approach and the kinetic theory for granular flows (KTGF), employing appropriate models that adapt to irregularly shaped particles and can precisely predict the interaction between particles is crucial. In this study, the effects of varying radial distribution functions (RDF), frictional viscosity models (FVM), angles of internal friction (ϕ), and stress blending functions (SBF) on the performance of two-fluid models (TFM) were investigated. Simulation predictions were compared and validated with the previous experiments in the literature on Geldart B biomass particles of walnut shells. When applying sphericity to account for size irregularities of biomass particles, the results of this study demonstrated that predictions of both the Ma−Ahmadi and the Carnahan−S... [more]

Because of the short distance between stations in urban rail transit, frequent braking of urban rail trains during operation will generate a large amount of regenerative braking energy. Urban rail trains can reduce their actual traction energy consumption using regenerative braking energy. Therefore, an energy-efficient optimization method for urban rail trains is proposed. By taking the punctuality of trains as the premise, the weighted acceleration of trains is taken as the synergetic variable, the synergetic coefficient is introduced to construct the following consistency model, and its convergence is proved. By analyzing the influencing factors of the following consistency coordination time, an adaptive parameter adjustment strategy is designed to solve the latest secondary traction time and the corresponding maximum speed of the primary traction. In order to save communication resources, the event trigger function is used to construct trigger conditions, and the consistency algori... [more]

A 3D computational fluid dynamics (CFD) model was developed to predict the airflow and heat transfer in half of a pallet layer of tomatoes. The numerical and experimental results were compared, and a good agreement was obtained between both results using the root-mean-square error (RMSE) and absolute relative deviation (ARD) values as criteria. The validated CFD model was then used to minimise the product temperature heterogeneity by optimising the airflow rate and the crate design. A downward flow of the air along the central parts of the crates and an upward flow close to the lateral walls of the crates were observed. Three different total ventilated areas (TVAs) were tested to study their influence on the product temperature uniformity and cooling rate. The MTD and ATD decreased from 6.8 to 3.5 °C and from 1.5 to 0.7 °C, respectively, when the TVA was increased from 11 to 15%.

This paper provides a procedure to design robust controllers based on observed states applied to three-phase inverters with LCL filters connected to a grid with uncertain and possibly time-varying impedances, which can arise in renewable energy systems and microgrid applications. Linear matrix inequalities are used to rapidly compute, off-line, based only on the choice of two scalar parameters for pole location, sets of gains for the controller and the observer, and also to provide a theoretical certificate of the closed-loop stability, including a limit for the rate of variations of the grid impedances. The proposed design procedure allows the easy implementation of robust state feedback controllers with a reduced number of sensors, ensuring good performance for different sets of grid impedances. Additionally, larger regions of guaranteed stability are provided by the proposed procedure, when compared with a similar condition from the literature. The control law using the observed sta... [more]

To clarify the organic matter (OM) enrichment of the Lishui Sag, the factors influencing the variable abundance of OM in the Lingfeng Formation are studied using organic geochemical data. The source rocks of the Lingfeng Formation have medium−high total organic carbon (TOC) values (0.53−3.56%). The main type of kerogen is II2-III. Compared to the shallow marine subfacies source rocks, the TOC of the delta front subfacies source rocks is higher. The distribution of biomarkers shows that the redox environment of the delta front subfacies source rock is the sub-oxidizing and oxic environment, and the source rock is mainly supplied by terrigenous higher plants; the redox environment of shallow marine subfacies source rocks is a sub-reducing and suboxic environment, and the OM mainly comes from algae. The link between OM input and OM abundance demonstrates that terrigenous OM (TOM) input has a considerable influence on OM abundance. However, there is no obvious relationship between preserva... [more]

The aim of this work is to introduce a novel statistical technique for quantifying the concentration field uniformity of the liquid-liquid mixing process within a micro-scale chaotic pipeline. For illustration, the microscale liquid-liquid mixer in which the inlet direction is parallel to the mixing unit is designed by using the chaotic pipeline with Baker map. Meanwhile, the non-uniformity coefficient method is adopted quantificationally instead of qualitatively estimating the concentration field uniformity of the chaotic micromixer based on uniform design theory and image analysis. Results show that the concentration distribution of the chaotic mixing process of liquid-liquid under various working conditions is obtained by solving the steady-state Navier−Stokes and diffusion convection equations. The average contribution ratio of the three basic mixing units of the chaotic Baker pipeline to the concentration field uniformity is approximately 6:3:1, which is calculated aligned with th... [more]

The dynamic development of electromobility has resulted in new directions of research, one of which is the analysis of the noise of traction motors. The designs of the motors used in electric vehicles are relatively new and often modified. In addition, strong competition also forces an increase in the power generated per unit mass of the motor, often at the expense of weakening the mechanical structure. This may result in an increase in the noise level generated by the electric drive, so this issue should be analyzed at the motor design stage. Different construction and operating conditions in relation to industrial or railway traction motors make it necessary to constantly develop methods for the noise analysis of the motors for electric vehicles. The aim of this article is to review the methods used so far in an analysis of the noise generated by the motors for electric vehicles. Three main methods are used by the authors of this paper: the analytical method, the hybrid method using... [more]

Recent research has highlighted wettability alteration as the main consequence of the different mechanisms involved in technologies such as adjusted brine composition water flooding (ABCW) and low-salinity water flooding (LSW). However, studies are still needed to give a phenomenological explanation, and the most influential components of the system (rock−oil−brine) must be clarified. This work focuses on determining the most relevant variables for the smart water effects to occur. Static (contact angles) and dynamic tests (coreflooding) were conducted. For the static tests, aged Berea slices, a specific crude oil (27° API, 10.5 cp at 60 °C), and mono and divalent inorganic salts (Na+, K+, Ca2+, and Mg2+/Cl−) were used in 3 different concentrations of 1000, 3000, and 5000 ppm (ionic strength variation between 0.015 and 0.06) to establish the wettability state by measuring the contact angles of the system. When salts containing chloride were evaluated, a decrease in oil wettability was... [more]

The annual yield of bifacial photovoltaic systems is highly dependent on the albedo of the underlying soil. There are currently no published data about the albedo of red soil in western Africa. In this study, the impact of the albedo of red soil in Ghana on the energy yield of bifacial photovoltaic systems is analysed. A bifacial photovoltaic simulation model is created by combining the optical view factor matrix with an electrical output simulation. For an exact simulation, the albedo of red soil at three different locations in Ghana is measured for the first time. The average albedo of every red soil is clearly determined, as well as the measurement span including instrumentation uncertainty; values between 0.175 and 0.335 were measured. Considering these data, a state-of-the-art bifacial photovoltaic system with an average of 19.8% efficient modules in northern Ghana can achieve an annual energy yield of 508.8 kWh/m2 and a bifacial gain of up to 18.3% in comparison with monofacial p... [more]

Two immiscible fluids flows are materialized in science and technology; the combined convection of the two immiscible fluids in a square conduit is reviewed in this study. The nanofluid and pure viscous fluid which do not mix are discussed, and both layers saturated with a porous matrix have different permeabilities. The Dupuit−Forchheimer and Tiwari−Das models are applied to outline the permeability of the layer and nanofluids, respectively. The finite difference method is utilized to find the solutions of conservation equations along with suitable boundary and interface conditions. The boundary condition for the velocity is no slip at all the boundaries, while continuity of velocity and shear stress are used at the interface. The left and right walls are kept at constant but different temperatures, the top and bottom walls are isolated, and the continuity of temperature and heat flux is assumed at the interface. Grashof number, Brinkman number, Darcy number, inertia parameter, permea... [more]

In this paper, we propose a sophisticated battery model for vanadium redox flow batteries (VRFBs), which are a promising energy storage technology due to their design flexibility, low manufacturing costs on a large scale, indefinite lifetime, and recyclable electrolytes. Primarily, fluid distribution is analysed using computational fluid dynamics (CFD) considering only half-cells. Based on the analysis results, a novel model is developed in the MATLAB Simulink environment which is capable of identifying both the steady-state and dynamic characteristics of VRFBs. Unlike the majority of published studies, the inherent characteristics of the flow battery, such as shunt current, ion diffusion, and pumping energy consumption, are considered. Furthermore, simplified charge transfer resistance (CTR) is taken into account based on electrochemical impedance spectroscopy (EIS) measurement results. The accuracy of the model was determined by comparing the simulation results generated by the equiv... [more]

Generally, the unit cell in a proton exchange membrane fuel cell (PEMFC) stack is divided into different zones according to the characteristics of the bipolar plate. There is a zone that has been neglected, which we define as the “neck zone” for the first time in this work. Uneven stress and deformation are prone to appearing in the neck zone due to its unique structure. A three-dimensional finite element model was applied to study the influence of the membrane electrode assembly (MEA) frame materials on the mechanical characteristics of the neck zone. In addition, the sealing and the water−gas transport performances of the neck zone were evaluated via the stress fluctuation and deformation. It was found that even with the commercial polyethylene naphthalate (PEN) frame, a leak point would be generated at the region with the lowest stress, reducing the performance and even causing safety hazards. The invasion rate was proposed to assess the water−gas transport ability. When an inapprop... [more]

Electrical energy substitution is an important way to achieve the optimization of the energy consumption structure as well as to alleviate environmental problems, and it is also an important source of benefits of the integrated energy system. However, there are few works that study the effects of electrical energy substitution on the construction of the integrated energy system (IES) and electrical energy substitution work without incentives carried out in the IES. To this end, this paper proposed a G1 method with constructing consistency matrix to determine the evaluation index weights for the IES with electrical energy substitution. Specifically, we firstly construct the evaluation index system for the IES including electrical energy substitution indicators, low-carbon indicators, technical indicators and economic indicators as well as their secondary indicators. Then, a tri-level evaluation index system of target-criteria-indicator benefits is established based on pertinent standard... [more]

Although a mixed carbonate−siliciclastic system of the Strawn Group on the Eastern Shelf in King County, Texas, USA provides excellent hydrocarbon reservoirs, facies variability and reservoir properties within such systems are not well understood. We conducted prestack, simultaneous seismic inversion, and high-level petrophysical analysis to derive elastic properties of rocks to facilitate lithology identification and determination and distribution of the different carbonate facies. Our results show that (1) the Strawn Group in King County is dominated mostly by carbonates and (2) given the ratio of P- and S-wave velocity (Vp/Vs ratio), the carbonates can be separated into three facies: (a) high-Vp/Vs-ratio shelf-edge reef carbonates, in which the Vp/Vs ratio decreases linearly as porosity increases and the Vp/Vs ratio varies from ~2.1 to ≤2.6; (b) moderately low-Vp/Vs-ratio shelf (platform) carbonates, in which the Vp/Vs ratio also decreases as porosity increases and in which the Vp/V... [more]

Removal of noise and restoration of images has been one of the most interesting topics in the field of image processing in the past few years. Existing filter-based methods can remove image noise; however, they cannot preserve image quality and information such as lines and edges. In this article, various classifiers and spatial filters are combined to achieve desirable image restoration. Meanwhile, the time adaptive self-organizing map (TASOM) classifier is more emphasized in our feature extraction and dimensionality reduction approaches to preserve the details during the process, and restore the images from noise. The TASOM was compared with the self-organizing map (SOM) network, and a suitable noise reduction method for images was attempted. As a result, we achieved an optimum method to reduce impulsive noise. In addition, by using this neural network, better noise suppression was achieved. Experimental results show that the proposed method effectively removes impulse noise and main... [more]

This study aims to develop statistical and machine learning methodologies for forecasting yearly electricity consumption in Saudi Arabia. The novelty of this study include (i) determining significant features that have a considerable influence on electricity consumption, (ii) utilizing a Bayesian optimization algorithm (BOA) to enhance the model’s hyperparameters, (iii) hybridizing the BOA with the machine learning algorithms, viz., support vector regression (SVR) and nonlinear autoregressive networks with exogenous inputs (NARX), for modeling individually the long-term electricity consumption, (iv) comparing their performances with the widely used classical time-series algorithm autoregressive integrated moving average with exogenous inputs (ARIMAX) with regard to the accuracy, computational efficiency, and generalizability, and (v) forecasting future yearly electricity consumption and validation. The population, gross domestic product (GDP), imports, and refined oil products were obs... [more]

The World Energy Council has consistently formulated useful policies and ranked countries in term of their performances in environmental sustainability, energy equity, and energy security. In a novel approach, and possibly in one of the most unique studies in the World Energy Trilemma literature, the current study examines the interaction of energy efficiency and economic growth of several top-performing economies (Austria, Denmark, France, Finland, Germany, New Zealand, Sweden, Switzerland, and the United Kingdom) in respect to environmental sustainability, energy equity, and energy security. Importantly, while affirming the inappropriateness of the linear econometric approach, the study utilized the newly developed quantile-on-quantile approach to examine the dataset for the period 1990Q1 to 2018Q4. As such, the result largely indicates a significant and positive effect of economic growth toward the energy efficiency across the quantiles for the examined countries (Austria, Denmark,... [more]

The design of moisture-durable building enclosures is complicated by the number of materials, exposure conditions, and performance requirements. Hygrothermal simulations are used to assess moisture durability, but these require in-depth knowledge to be properly implemented. Machine learning (ML) offers the opportunity to simplify the design process by eliminating the need to carry out hygrothermal simulations. ML was used to assess the moisture durability of a building enclosure design and simplify the design process. This work used ML to predict the mold index and maximum moisture content of layers in typical residential wall constructions. Results show that ML, within the constraints of the construction, including exposure conditions, does an excellent job in predicting performance compared to hygrothermal simulations with a coefficient of determination, R2, over 0.90. Furthermore, the results indicate that the material properties of the vapor barrier and continuous insulation layer... [more]

Liquid biowaste represents more than 98% of the total municipal waste streams on wet basis and 4−5% on dry basis. Recent attention has been focused on how to manage it optimally, and several novel technologies are being developed to valorize it. Among the developing alternatives is a technology that operates continuously by integrating a hydrothermal reactor, a gasifier and condenser to recover hydrochar using any produced gases to power the system. This study introduces the “3-step evolution model” in order to simulate the hydrothermal reactor. The model has been developed in a MATLAB/Cantera environment and calculates the outputs as the products of a series of sub-stoichiometric char-gas reactions. Experiments with chicken manure slurry as feedstock were implemented for the validation of the model. Treatment of 32.16 kg/h of chicken manure produces 4.57 kg/h of hydrochar and 3.45 kg/h of syngas. The 3-step evolution model simulated the correct ratio of solid-to-gas, 57−43% (excluding... [more]

This paper shows the technical−economic assessment of two power systems based on renewable electricity to cover the energy consumption requirements of a drinking water treatment plant in the town of Pile, Ecuador, with a planning horizon of 15 years. A stand-alone and a grid-connected solar PV system were proposed to power this plant, which was designed considering the maximum daily potable water supply condition. This plant operated under two scenarios: (1) 12 h during daylight hours and (2) 24 h. Both schedules were proposed to assess the impact of PV power systems on plant operation. We modeled and optimized a total of four scenarios, where each scenario consisted of one of the proposed PV power systems and the plant with one of its operating schedules. Homer Pro software was used to size and find an optimal solution in each scenario, considering the net present cost (NPC) as the main criterion for optimization. The results showed that the change in the plant operation schedule sign... [more]

The main objective of this research is to identify the scope of the use of EU funds for the formation of a low-carbon economy by enterprises providing energy services in Poland in 2014−2020. As a result of the identification, a model for the use of EU funds based on the following criteria was identified: the purpose of the investment, the type of fund, the type of support program, the range of support values and the form and level of funding. As a research gap has been identified due to the insufficient investigation of the use of EU funds by the largest energy companies in Poland to shape a low-carbon economy, the findings presented are novel and contribute to a better understanding of the use of EU funds by Poland’s largest energy sector companies. Data on investment projects financed by EU funds were obtained from the database of the Ministry of Funds and Regional Policy for 2014−2020, while the characteristics of the companies were obtained from industry reports, the National Court... [more]

The management of energy in distribution networks has been gathering attention in recent years. The simultaneous control of generation and demand is crucial for achieving energy savings and can further lower energy pricing. The work aims to develop a control scheme for a hybrid microgrid that can provide stability to the bus voltage and effectively manage the power flow. Solar energy is the current trend in renewable energy sources (RES). There is a surge in the installation of solar PV systems both on a large scale and on a small scale, such as rooftop PV systems. Installation of RES at residential premises has to be conducted with a proper power management scheme. The hybrid microgrid for this work consists of a PV system with a boost converter to extract maximum power, a DC-DC bi-directional converter to charge or discharge the hybrid energy-storing devices, and a three-phase AC-DC interlinking converter for exchange of energy with the utility grid. The control and power management... [more]

This study analyzes European natural gas (NG) prices since the eve of the 2008 financial crisis. Spearman’s rank correlation coefficients associate prices with and without taxation, whereas a hierarchical clustering analysis clarifies similarities in NG pricing behavior. After performing econometric tests to ensure the satisfaction of classical hypotheses and identify a system of endogenous variables, structured unrestricted and restricted vector autoregressive models are applied to panel data composed of 34 spatial units and 31 units of time drawn from 2007−2022 to confirm the presence of short-term and long-term causal dependencies. The nonparametric analysis identifies three groups of countries that exhibit a differentiated pricing behavior. The parametric analysis reveals a significant and asymmetric short run relation, which is imposed by liquefied natural gas (LNG) imports from Nigeria on the logarithm of NG prices. However, the sign of coefficients associated with lagged LNG imp... [more]

For load forecasting, numerous machine learning (ML) approaches have been published. Besides fully connected feedforward neural networks (FFNNs), also called multilayer perceptron, more advanced ML approaches like deep, recurrent or convolutional neural networks or ensemble methods have been applied. However, evaluating the added benefit by novel approaches is difficult. Statistical or rule-based methods constitute a too low benchmark. FFNNs need extensive tuning due to their manifold design choices. To address this issue, a structured, comprehensible five-step FFNN model creation methodology is presented, which constitutes of initial model creation, internal parameter selection, feature engineering, architecture tuning and final model creation. The methodology is then applied to forecast real world heat load data of a hospital in Germany. The forecast constitutes of 192 values (upcoming 48 h in 15 min resolution) and is composed of a multi-model univariate forecasting strategy, with t... [more]