The purpose of the current study is to investigate the non-Newtonian unsteady Williamson fluid on a stretching/shrinking surface along with thermophoresis and Brownian effects. Basically, the model consists of a time-dependent magnetic field. The fluid is considered to be electrically conducting due to the effect of the external magnetic field. The values of magnetic Reynolds number are so small that the induced magnetic field is assumed to be negligible. In the concentration equation, the effects of Brownian motion and thermophoresis are discussed. Employing the similarity transformations, the governing nonlinear Partial Differential Equations (PDEs) are converted into the Ordinary Differential Equations (ODEs). The resulting ODEs are solved with the combined effects of the Successive Over Relaxation (SOR) method and Finite Difference Method (FDM). The impact of all the including parameters such as suction parameter, injection parameter, stretching/shrinking parameter, the ratio of vi... [more]

This research paper aims to evaluate the effect of social networks on the green innovation of energy sector firms working around the globe. The study also evaluated green dynamic capabilities’ mediating, and green organizational culture’s moderating role in the association of the social networks and green innovation. The study will help electricity production and distribution firms to become more environmentally proactive and achieve green innovation. For this research, study data were collected from employees working in the energy sector firms of Pakistan. Standardized scales were adapted from previous studies and a questionnaire was developed using ‘Google Docs’ and distributed using Facebook. From different energy sectors of Pakistan,476 respondents filled the questionnaires. To examine the research hypotheses, we chose energy firms that act as small and medium enterprises and face problems in the achievement of green innovation. For testing the proposed relationships, descriptive s... [more]

The article deals with the issue of the influence of selected material and construction solutions for a floor in a historic wooden building on heat exchange with the ground. The scope of the work included continuous measurements of selected parameters of internal and external microclimate, which were later used for numerical analysis of selected calculation variants. The research was carried out in a historic wooden church located in southern Poland. The research period covered 2019, while all measurements were performed every 1 h. For the variant analysis, a building with a wooden and stone floor was adopted. The influence of the heating system on the heat exchange with the ground for wooden and stone floors was also analysed. As a result of a detailed analysis, it was found that the material and construction solutions, as well as the heating system, have a significant impact on the formation of heat exchange with the ground. The building with a wooden floor was characterised by signi... [more]

Several management and control techniques for hybrid energy storage systems (HESS) with batteries and supercapacitors are presented in the literature applied to microgrids (MGs). The filter-based control strategy for defining the control loop actuation is one of the most widely used approaches with satisfactory performance. Variations of the Filter-Based Method (FBM) method are proposed to improve the control efficiency of the HESS under load disturbance and intermittent generator sources. However, not enough attention has been paid to the impacts of MG on the operational performance of batteries, despite the fact that they represent a non-negligible percentage of the total cost of MGs. In this paper, a control strategy called FBM-CSoC is proposed that focuses primarily on mitigating battery safety and degradation issues. The control strategy proposes a distribution of the charging and discharging current in a weighted proportional way to the normalized rated capacity and current state... [more]

Steel converter slag, also called Linz-Donawitz (LD) slag, has been considered as an oxygen carrier for biofuel chemical looping applications due to its high availability. In addition to its content of iron which contributes to its oxygen-carrying capacity, LD slag also contains a significant amount of calcium. Calcium, however, is known to interact with sulfur, which may affect the usability of LD slag. To get a better understanding of the interaction between sulfur and LD slag, batch scale experiments have been performed using solid and gaseous fuel with or without sulfur dioxide, together with LD slag as an oxygen carrier. The reactivity and sulfur interaction were compared to the benchmark oxygen carrier ilmenite. Sulfur increases the gasification rate of biofuel char and the conversion of CO for both LD slag and ilmenite. However, no effect of sulfur could be seen on the conversion of the model tar species benzene. The increased gasification rate of char was suspected to originate... [more]

Nowadays, aerodynamics is a key focal point in the vehicle design process. Beyond its direct impact on the performance of a vehicle, it also has significant effects on economics and safety. In the last decade numerical methods, mainly Computational Fluid Dynamics (CFD), have established themselves as a reliable tool that assists in the design process and complements classical tunnel tests. However, questions remain about the possible obtained accuracy, best practices and applied turbulence models. In this paper, we present a comprehensive study of motorcycle aerodynamics using CFD methods which, compared to the most common car aerodynamics analysis, has many specific features. The motorcycle, along with its rider, constitutes a shape with very complex aerodynamic properties. A detailed insight into the flow features is presented with detailed commentary. The front fairing, the front wheel and its suspension were identified as the main contributors to the aerodynamic drag of the motorcy... [more]

The increase in inverter-based resources associated with the increased installation of PV sources is a concern because it reduces the inertia of the power system during peak PV generation periods. As a countermeasure to reduce grid inertia, the addition of pseudo-inertia using virtual synchronous machines can be selected, and PV generation can cooperatively contribute to the stable operation of the power system by using the suppressed output as reserve power. However, few studies have analyzed VSMs that do not use batteries and use PV as a resource (PV-VSM) in simulations, including grid interconnection and solar radiation fluctuations, and it is necessary to clarify the issues and discuss countermeasures. In this study, electromagnetic transient response analysis was applied to a VSM connected to a two-generator system, simulations were performed, and the following findings were reported and countermeasure methods for the problem were proposed. When the PV capacity is insufficient for... [more]

Vibrations occur in the wind turbine drivetrain due to the drivetrain’s elasticity and gear clearance. Typically, the PID control method is used to suppress elastic vibration, while the method with the disturbance suppression function is used to suppress nonlinear gear clearance vibration. The purpose of this paper is to propose an equivalent PID control method based on the internal model control (IMC) for suppressing vibration caused by the wind turbine drivetrain’s elasticity and gear clearance. The equivalent PID controller can suppresses elastic vibration; the IMC controller can suppresses gear clearance vibration. First, the vibration principle of the two-mass wind turbine drivetrain with clearance is discussed. After analyzing the nonlinear characteristics of the gear clearance, the nonlinear clearance system is decomposed into a linear unit and a nonlinear bounded disturbance unit. To suppress nonlinear bounded disturbances, a disturbance suppression method based on IMC is propo... [more]

A large number of bubbles generated by the air agitation device in an external melting ice storage system can cause the disturbance of the ice−water mixture, which can enhance the heat transfer and contribute to the reduction in energy consumption. The structural design and optimization of the air agitation device in an external melting ice storage system is the key issue for energy savings. In this study, the influence of different orifice spacings and diameters on the distribution of the gas−liquid flow field, gas holdup, heat-transfer coefficient, and power consumption in the ice storage tank was investigated by numerical simulation. The simulated results showed that the heat-transfer coefficient of the ice−water mixture with air bubbles should be 3−5 times higher than the natural convection when the air superficial velocity is 0.03 m/s. The gas holdup was mainly affected by the orifice spacing, and the maximum varied from 5.0% to 8.2%. When the orifice spacing was less than 150 mm,... [more]

This paper presents the experimental estimation of the ignition pressure value produced by a primer in small arms ammunition. Investigations were performed using a chamber of the capacity equal to the capacity of the 12.7 mm ammunition case. The inner volume of the chamber was adjusted to the free volume in the cartridge by inserting a sleeve or glass balls of a diameter of 2 or 4 mm. The pressure values were measured inside the chamber after the action of the primer. The maximum pressure value was used as an estimation of the ignition pressure value. Depending on the nature of the filling, considerably different values were obtained; they were compared with the values of pressure measured inside the case at the live firing. A considerable difference between the ignition pressure values measured inside the case and those measured in the model setup was detected. Based on these results, a discussion concerning the choice of the starting pressure in interior ballistics lumped parameters... [more]

Currently in the European Union (EU) there is an intense debate on the limits to acquire the European Green Deal, to make Europe the first climate neutral continent in the world [...]

Traditional charging stations have a single function, which usually does not consider the construction of energy storage facilities, and it is difficult to promote the consumption of new energy. With the gradual increase in the number of new energy vehicles (NEVs), to give full play to the complementary advantages of source-load resources and provide safe, efficient, and economical energy supply services, this paper proposes the optimal operation strategy of a PV-charging-hydrogenation composite energy station (CES) that considers demand response (DR). Firstly, the operation mode of the CES is analyzed, and the CES model, including a photovoltaic power generation system, fuel cell, hydrogen production, hydrogen storage, hydrogenation, and charging, is established. The purpose is to provide energy supply services for electric vehicles (EVs) and hydrogen fuel cell vehicles (HFCVs) at the same time. Secondly, according to the travel law of EVs and HFCVs, the distribution of charging deman... [more]

Energy monitoring is a vast field of research [...]

A helium (He) dielectric barrier discharge plasma jet (DBD jet) was used for the first time for treating graphite foil as the current collector of a paper-based fluidic aluminum-air battery. The main purpose was to improve the distribution of the catalyst layer through modification and functionalization of the graphite foil surface. The plasma functionalized the graphite foil surface to enhance the wettability where the more hydroxyl could be observed from XPS results. The 30 s-He DBD jet treatment on the graphite foil significantly improved the battery performance. The best current density of 85.6 mA/cm2 and power density of 40.98 mW/cm2 were achieved. The energy density was also improved to 720 Wh/kg.

China’s green credit has mostly been invested in new energy areas with positive environmental externalities in recent years, while coal power enterprises have been neglected. This paper constructs a tripartite evolutionary game model among government, coal power enterprises, and banks to clarify the key factors and mechanisms for coal power enterprises undergoing green transformation. The research results show that: Firstly, to realize the spontaneous green transformation of coal power enterprises, spontaneous profitability must be achieved before the removal of policy incentives, which is reflected in the continuous increase in electricity price, carbon emission trading price, and decrease in green transformation cost. Secondly, the green credit adjustment factor cannot determine whether a company chooses to undertake green transition, but it provides a valuable window of green transition for companies. When the relative benefits of green transformation projects are greater than the r... [more]

Accurately predicting the critical differential pressure (CDP) of sand production contributes to improving the peak-shaving capacity and ensuring safe operation of underground gas storage (UGS). The CDP of sanding production in the target wells of the UGS was predicted coupling laboratory tests, inversed analysis with well logging data and numerical simulations. The in-situ mechanical properties of rock were estimated by coupling the laboratory test results and well-logging data. The in-situ stress field of the target formation was then deduced through inversed analysis coupled finite element method (FEM) and genetic algorithm (GA), based on the existing known stress data and the seismic data of the measured points. Using the critical strain limit (CSL) of 5‰ as the sanding criterion of the wellbore, the CDPs of the gas production in the UGS were predicted, which was 5.59 MPa, 3.98 MPa, and 4.01 MPa for well #1, well #2 and well #3, when the pressure of the gas storage was 30 MPa, resp... [more]

Kick is one of the most important drilling problems, and because its occurrence makes drilling engineering extremely complex, it is essential to predict the possibility of kick as soon as possible. In this study, k-means clustering was combined with four artificial neural networks: regularized RBFNN, generalized RBFNN, GRNN, and PNN, to estimate the kick risk. To reduce data redundancy and normalize the drilling data, which contain kick conditions, k-means clustering was introduced. The output layer weights were then determined using a brute-force search with different Gaussian function widths, resulting in a series of artificial neural networks composed of different clustering samples and different Gaussian function widths. The results showed that the prediction accuracy of regularized RBFNN + k-means model was the highest, that of the GRNN + k-means model was the lowest. The kick prediction accuracy for regularized RBFNN, generalized RBFNN, GRNN, and PNN were 75.90%, 65.20%, 51.70%,... [more]

The largest Precambrian gasfield in China has been found from the Ediacaran (Sinian) carbonates in the central Sichuan Basin. The deep ancient reservoirs were generally attributed to the high-energy mound-shoal body in the carbonate platform. However, there is still little understanding on the distribution of the mound-shoal bodies that hampers further gas exploitation from the deep subsurface. Based on the seismic data, a large strike-slip fault system was identified by new 3D seismic data in the central Sichuan Basin. Further, it was found that the strike-slip fault had some effects on the mound-shoal bodies of the Ediacaran Dengying Formation. First, the platform margin was divided by strike-slip faults into three distinct segments to show two weak-rimmed margins and one interbedded rimmed margin. Second, the platform margin could be offset or migrated with the strike-slip faults. Third, there is varied margin thickness across the strike-slip fault zone. In the inner platform, more... [more]

In response to the difficulty of fracture modification in inter-salt shale reservoirs and the unknown pattern of hydraulic fracture expansion, corresponding physical model experiments were conducted to systematically study the effects of fracturing fluid viscosity, ground stress and pumping displacement on hydraulic fracture expansion, and the latest supercritical CO2 fracturing fluid was introduced. The test results show the following. (1) The hydraulic fractures turn and expand when they encounter the weak surface of the laminae. The fracture pressure gradually increases with the increase in fracturing fluid viscosity, while the fracture pressure of supercritical CO2 is the largest and the fracture width is significantly lower than the other two fracturing fluids due to the high permeability and poor sand-carrying property. (2) Compared with the other two conventional fracturing fluids, under the condition of supercritical CO2 fracturing fluid, the increase in ground stress leads to... [more]

If global energy consumption returns to its pre-pandemic growth rate, it will be almost impossible to transition to a zero-emission or net-zero-emission energy system by 2050 in the absence of large-scale CO2 removal. Since relying on unproven technologies for CO2 removal is speculative and risky, this paper considers an energy descent scenario for reaching zero greenhouse gas emissions from energy by 2050. To drive the rapid transition from fossil fuels to carbon-free energy sources and ensure demand reduction, funding is needed urgently in order to implement four strategies: (i) technology change, i.e., implementing the growth of zero-carbon energy production, end-use energy efficiency and ‘green’ energy carriers, together with ongoing R&D on CO2 removal; (ii) reducing climate impacts; (iii) reducing energy consumption by social and behavioural changes; and (iv) improving human wellbeing while increasing social justice. Modern monetary theory explains how monetary sovereign governmen... [more]

This work presents some numerical simulations, performed using AMESim software, for a system composed by two redundant servo-actuators. Certain operating conditions are taken into account for these two electro-hydrostatic servo-actuators, which are coupled to the command surface (aileron) of a transport aircraft. We first considered the situation of slight asymmetries in the construction of the servo-actuators, then a situation in which one servo-actuator fails at maximum flight speed, and then at a medium flight speed, and finally we considered the effect of gusts upon the system. Small differences in the construction of the servo-actuators were taken into consideration by modifying each of the pump displacements, one by +2% and one by −2%, from the nominal value. It is possible that many other asymmetries exist in the construction of servo-actuators, such as different liquid leakages in the cylinders or pumps, small differences in the controller coefficients, and so on. These differe... [more]

The article discusses the methods used to measure the water content in liquid dielectrics. The pros and cons of currently used methods are presented. The main aim of the research was to check the possibility of using near-infrared spectroscopy to measure the water content in liquid dielectrics. On the basis of the conducted research, the absorbance bands are indicated that can be used to determine the water content in synthetic and natural esters. These bands are centered at 1901 and 1904 nm for natural and synthetic esters, respectively. The determined dependence of the absorbance on the water content in liquid dielectrics confirmed the linear nature of this relationship. Moreover, the influence of liquid aging degree on the result of absorbance measurements was checked. The verification of the method allowed for confirming the possibility of using near-infrared spectroscopy for the reliable quantitative analysis of water content in synthetic and natural esters.

The solar-assisted cold water phase-change energy heat pump system is a clean energy heating system which can effectively reduce the ice melting energy consumption of the cold-water phase-change energy heat pump system. In this paper, the operation mode of the solar-assisted cold-water phase-change energy heat pump system is given, three new ice melting methods are proposed, the performance of three ice melting modes using solar energy for thermal ice melting are simulated, and the influence of ice thickness on system operation is analyzed. The results show that among the three ice melting modes, the affected serial dual-source heat pump mode has the largest system COP, and the pure serial dual-source heat pump mode has the smallest annual total cost. Among the solar collector price, glycol price and electricity price, the change in solar collector price has the greatest impact on the total annual cost, and the change in glycol price has the least impact on the total annual cost. When... [more]

The performance of heat exchangers is severely limited by airside thermal resistance. The effect of redirection louvers (RLs) on the airside thermal performance of a compact flat-tube louvered fin heat exchanger was investigated. A steady-state 3D numerical analysis was conducted for different fin configurations by varying the number of RLs (NRL = 1, 2, 3, and 5). Conjugate heat transfer analysis was performed at the low Re (50−450) for domestic and transport air-conditioning applications. Geometric parameters such as louver pitch, louver angle, fin pitch, and flow depth were set as 1.7 mm, 27°, 1.2 mm, and 20 mm, respectively. The effective heat transfer fin surface areas of different fin configurations were also kept identical for a comparative analysis. The influence of the RLs on the airside thermal−hydraulic performance was analysed by exploring the local and average Nusselt numbers, pressure drop, Colburn j factor, friction factor f, performance evaluation criteria (PEC), and flo... [more]

In low voltage (LV) distribution systems, the problem of overvoltage is common during the lower load intervals. This problem arises because of the high value of R/X ration of these systems. Many techniques are available in literature to cope up with this problem at the converter level; mostly these methods control the reactive or active power of the photovoltaic (PV) systems. However, there are certain restrictions and complications with the reactive power control of PV systems. Most of the active power control methods have been implemented at the inverter stage of the PV system, resulting in implementation complexities and excessive oversizing of the converter. Therefore, in this paper, a simple, de-rating based voltage control algorithm is proposed to overcome the problem of overvoltage. So far de-rating technique has been used to enable frequency support functions in PVs; in a first of its kind, de-rating technique is used here to control the voltages in PV rich LV distribution syst... [more]