Lithium-ion batteries will generate a large amount of heat during high-rate charging and discharging. By transferring the heat to the environment in time, the batteries can be kept in a suitable temperature range. This allows them to work normally, prolongs their cycle life, and reduces the risk of thermal runaway. Immersion cooling is a simple and efficient thermal management method. In this paper, a battery thermal management system (BTMS) with immersion cooling was designed by immersing the lithium-ion cells in the non-conductive coolant—dimethyl silicone oil. The electric−thermal coupled model was adopted to obtain the heat production and temperature distribution of the cell during discharging, and the performance of the system was obtained by numerical calculation. It was found that, compared with natural cooling, immersion cooling could significantly reduce both the maximum temperature (MAT) of the cell and the temperature of the tabs during the 3C discharging process. However, t... [more]

This paper analyses the validity of using superconductors in the power supply system of arc devices. Two cases were analysed: when an additional superconducting element was included in the conventional power supply system and when the total power supply system was made of a superconductor. The analysis was carried out by simulating the cooperation of the arc receiver with its simplified power supply system in Matlab Simulink software. The characteristics of the changes of the arc current, its conductance and voltage as a function of the arc length changes for selected superconductor parameters, i.e., different values of the critical current and different values of the resistance in the resistive state, are given. The time courses of these quantities as well as the courses of resistance changes in the superconductor at randomly varying arc lengths are presented. The analysis showed that by selecting the critical current and resistance in the resistive state of the superconductor, arc pa... [more]

With the increasing global requirements for environmental protection, refrigerants with ODP of 0 and low GWP are widely concerned and applied. In this paper, the CFD numerical method simulates the R134a centrifugal compressor directly replaced by R1234yf and R1234ze(E). The results show that at the same compressor rotational speed, using R1234yf to replace R134a directly can obtain a higher cooling capacity, but it reduces COP by about 12.5%; using R1234ze(E) to replace R134a directly reduces the cooling capacity under partial working conditions, the COP is reduced by about 7.0%. When the evaporation temperature, condensation temperature, and cooling capacity are the same, compared with the R134a unit, the COP of the R1234ze(E) unit is reduced by about 5.14%, and it is reduced by about 8.93% for the R1234yf unit. For the R134a centrifugal chiller, the drop-in replacement of R134a with R1234ze(E) can obtain better system performance compared with R1234yf.

This article discusses methods of enhanced power generation using a binary power system with low-boiling fluid as an intermediate energy carrier. The binary power system consists of micro-gas and steam power units and is intended for remote standalone power supply. Trifluotrichloroethane was considered as the working agent of the binary cycle. The developed system was modeled by two parts in MATLAB Simulink and Aspen HYSYS. The model in Aspen HYSYS calculates the energy and material balance of the binary energy system. The model in MATLAB Simulink investigates the operation of power electronics in the energy system for quality power generation. The results of the simulation show that the efficiency of power generation in the range of 100 kW in the developed system with micro-turbine power units reaches 50%.

With increasingly more renewable energy being integrated into the AC-DC hybrid grid, the grid shows more complex dynamic characteristics due to the mutual coupling of HVDC and renewable energy. To evaluate the renewable energy resources’ penetration capacity of the AC-DC hybrid grid, this paper proposes an evaluation method of the renewable energy resources’ penetration capacity of an AC-DC hybrid grid, which considers both economy and safety. Firstly, indicators are proposed for an evaluation of the economy and safety of the AC-DC hybrid grid integrated with renewable energy, where both static and transient stability indicators are considered. Secondly, to maximize the renewable energy penetration capacity and minimize the network loss, an optimization model of the renewable energy penetration capacity of the AC-DC hybrid grid is established considering the static and transient stability constraints. Then, a heuristic solution method for solving the renewable energy penetration capaci... [more]

This research aims to examine the direct impact of green innovation strategies and the green dynamic capability on green innovation. The indirect effect is also tested, using green organizational identity as a mediator. A cross-sectional and quantitative research approach was used to collect data from energy firms. The results show that green innovation strategies and green dynamic capabilities positively affect the green innovation. The findings also proved that a green organizational identity acts as a mediator. The research outcomes suggest that the role of green organizational identity needs to be verified by firm managers who want to boost green innovation. In the advance era, society is more conscious about the green environment. Managers need a green innovation strategy to achieve green innovation within their firm. This study will help to manage the environmental issues, environmental degradation reductions, and establishment of green programs and products, which will all benef... [more]

Carbon dioxide (CO2) capture and storage have attracted global focus because CO2 emissions are responsible for global warming. Recently, injecting CO2 into shale gas reservoirs is regarded as a promising technique to enhance shale gas (i.e., methane (CH4)) production while permanently storing CO2 underground. This study aims to develop a calculation workflow, which is built on the simplified local-density (SLD) model, to predict excess and absolute adsorption isotherms of gas mixture based on single-component adsorption data. Such a calculation workflow was validated by comparing the measured adsorption of CH4, CO2, and binary CH4/CO2 mixture in shale reported previously in the literature with the predicted results using the calculation workflow. The crucial steps of the calculation workflow are applying the multicomponent SLD model to conduct regression analysis on the measured adsorption isotherm of each component in the gas mixture simultaneously and using the determined key regress... [more]

Due to the complex operation conditions in a power transformer, an oil-impregnated pressboard (OIP) simultaneously suffers from thermal, electrical, and mechanical stress. Since most research studies have paid much attention to thermal or electrical aging of OIPs, this paper analyzes the effects of long-term mechanical vibrations on cellulose degradation in OIPs under simultaneous multi-stress. The aging experiments were firstly conducted at 130 °C, with a DC electric voltage of +6 kV, vibration amplitude of 10−50 μm, and vibration frequency of 100−300 Hz. The finite element analysis (FEA) of the pressboard vibration model was then performed on Abaqus to investigate the time−frequency domain characteristic parameters of compressive stress on the pressboard under varied vibration frequencies and amplitudes. The FEA results reveal that compressive stress on the pressboard in a multi-stress aging experiment coincided with the axial compressive stress on the insulation spacers in an SZ-500... [more]

Unplanned power plant failures have been seen to be a major cause of power shortages, and thus customer power cuts, in the South African power grid. These failures are measured as the unplanned capability loss factor (UCLF). The study of South Africa’s UCLF is almost non-existent. Parameters that affect the future UCLF are, thus, still not well understood, making it challenging to forecast when power shortages may be experienced. This paper presents a novel study of South African UCLF forecasting using state-of-the-art deep learning techniques. The study further introduces a novel deep learning ensemble South African UCLF forecasting system. The performance of three of the best recent forecasting techniques, namely, long short-term memory recurrent neural network (LSTM-RNN), deep belief network (DBN), and optimally pruned extreme learning machines (OP-ELM), as well as their aggregated ensembles, are investigated for South African UCLF forecasting. The impact of three key parameters (in... [more]

In recent years, verification and validation processes of automated driving systems have been increasingly moved to virtual simulation, as this allows for rapid prototyping and the use of a multitude of testing scenarios compared to on-road testing. However, in order to support future approval procedures for automated driving functions with virtual simulations, the models used for this purpose must be sufficiently accurate to be able to test the driving functions implemented in the complete vehicle model. In recent years, the modelling of environment sensor technology has gained particular interest, since it can be used to validate the object detection and fusion algorithms in Model-in-the-Loop testing. In this paper, a practical process is developed to enable a systematic evaluation for perception−sensor models on a low-level data basis. The validation framework includes, first, the execution of test drive runs on a closed highway; secondly, the re-simulation of these test drives in a... [more]

This paper is a study of unintended cogging torque for the IPMSM (Internal Permanent Magnet Synchronous Motor) of an EPS (Electric Power Steering) system considering manufacturing disturbances. The IPMSM has been used recently in EPS systems with high power density. However, due to the complex rotor shape of the IPMSM, considering manufacturing disturbances, it is expected to reduce the quality of IPMSM performance. Therefore, the unintended cogging torque for motor quality is also expected to increase. This paper analyzes the causes of unintended cogging torque in the IPMSM of an EPS system considering manufacturing disturbances. Based on the harmonic order analysis of measured cogging torque for the IPMSM prototypes, the causes of unintended cogging torque in the IPMSM are verified due to the manufacturing disturbances.

The Gallium Nitride high electron mobility transistor (GaN HEMT) has been considered as a potential power semiconductor device for high switching speed and high power density application since its commercialization. Compared with the traditional Si transistors, GaN HEMT has faster switching speed and lower on-off loss. As a result, it is more sensitive to the nonlinear parameters due to the fast switching speed. The subsequent voltage and current overshooting will affect the efficiency and safety of the GaN HEMT and power electronic systems. In this paper, an accurate switching transient analytical model for GaN HEMT is proposed, which considers the effects of parasitic inductances, nonlinear junction capacitances and nonlinear transconductance. The model characteristic of turn-ON process and turn-OFF process is illustrated in detail, and the equivalent circuits are derived for each switching transition. The accuracy of the proposed model can be verified by comparing the predicted swit... [more]

In the creation of this Special Issue, the editors identified circular bioeconomy, i [...]

The Earth is permanently surrounded by cloud cover that, particularly, is an essential component in the planet’s energy balance. In turn, cloud cover intervenes in the main conditioning factor for soil temperature: solar radiation. In particular, the soil thermal amplitude should be dampened with the attenuation of solar radiation. However, the scientific community rarely analyzes this relationship, neglecting the model that is used to estimate the soil temperature. In this context, the present study seeks to reformulate the model by inserting a variable referent to cloud cover. Thus, to achieve this objective, a physical-mathematical review of the heat flow in the vertical profile of soil is performed. The reformulated model indicates the influence of cloud cover, intervening for both the soil’s heating (nighttime period) and cooling (daytime period). Finally, the reformulated model should be employed to estimate the soil thermal behavior (in particular, on “overcast sky” days).

The complex flow phenomena in a three-dimensional supersonic steam ejector were simulated with a non-equilibrium condensation model including real physical properties in different pressure conditions. The different working conditions include discharge pressure, motive pressure, and suction pressure. The influence of different pressures on shock waves in the steam ejector was investigated comprehensively. The intrinsic causes of shock wave variation with pressure conditions were explained in detail. The results show that the width of the primary shock train region expand with an increase in the motive pressure or a decrease in suction pressure. The diamond shock waves move downstream with an increase in motive pressure or a decrease in suction pressure. The shocking position in the diffuser moves upstream until it reaches the diffuser entrance with an increase in discharge pressure or a decrease in motive pressure or suction pressure. The intensity and number of oblique shock waves in t... [more]

A prediction method of hydrocarbon distribution associated with fault-shale caprock configuration leakages is established through superposing hydrocarbon distribution at deep basin fault-shale caprock configuration leakages, and conducting faults to understand distribution of shallow reservoirs of “lower generation, upper accumulation” in petroliferous basins based on fault-shale caprock configuration leakage mechanism. Prediction of hydrocarbon distribution at the Ed-3 Member in the south of the northern Dagang area of Bohai Bay Basin was used to demonstrate the application of the proposed method. Results show that predicted oil and gas at the Ed-3 Member are mainly distributed in the middle of the north and in the middle of the south edge, where fault-shale caprock configuration leakages in the middle of the Sha-1 Member contributed positively to oil and gas migration from the hydrocarbon reservoir at deep basin to the shallow reservoirs. The prediction matches well with discovered o... [more]

In this study, the conductivity and permittivity of electrical pressboard—insulating liquid—water composites were investigated, and the electrical properties of the composites and water were analysed comparatively. Mineral oil and synthetic ester were used as insulating liquids. It was found that the presence of water caused an increase in the permeability of the composite in the frequency range below 100 Hz. The value of static permittivity determined by water in the content of 5 wt. % was approximately 15. To obtain this value caused by liquid water, its volume should be approximately five (oil) and four times (ester) higher than its actual content, respectively. The determined values of the activation energy of the DC conductivity of the composites were several times higher than the values of the activation energy of the conductivity of the liquid water. The experimental values of the dielectric relaxation times were many orders of magnitude higher than the dielectric relaxation tim... [more]

Ongoing climate change most pronounces itself in northern latitudes, including in the Arctic zone of the Russian Federation (AZRF). Climate change is a complex multidirectional process that is characterized by both positive and negative effects on the functioning of territorial economic systems. In this regard, an analysis of the impacts of climate change on economic development is a particularly urgent scientific and practical task that requires comprehensive study. This research was devoted to assessing the probable impacts of climate transformations on the parameters of the economic development of the AZRF regions. The authors created a methodological approach to the assessment of the costs of the effects of climate change for the economy of the AZRF regions, taking into account the average predicted dynamics of surface air temperature and key regional economic specializations, as well as the degree of susceptibility of various industries to the climate change. The energy industry w... [more]

During coreflooding under stationary conditions, permeability is determined by the Darcy formula; thus, the apparent permeability is determined, which characterizes the average hydraulic conductivity of the core, but does not take into account the processes occurring at the microlevel. Transient processes during fluid injection regime change are important for understanding the evolution of permeability and underlie such phenomena as permeability degradation and its hysteresis. Our paper presents the coreflooding methodology and the results showing that during changes in injection conditions, the permeability of samples can significantly decrease due to the migration of colloids. In the developed methodology, coreflooding conditions exclude the influence of other factors on permeability, such as creep, the chemical reactions of rocks and fluids, and chemical mobilization of colloids. It has been established that the decrease in permeability occurs only when fluid is injected through the... [more]

This study deals with gaseous insulation contaminated by free moving particles. Two gases were investigated: SF6 (0.45 MPa) and a CO2/O2 gas mixture (0.75 MPa). Video recordings were used to track a free particle moving between a plate and a Rogowski electrode for validation of a 1D particle motion model. The effect of fixed and free particles (4 or 8 mm, Ø 0.9 mm) on the breakdown voltage and the mean time between breakdowns was determined in a concentric set of electrodes. The value of the breakdown voltage for a free particle was between those of a particle fixed to the enclosure and the central electrode. The particle motion in the concentric case could not be observed in the experimental set-up and was therefore simulated using a 1D model. For the 4 mm free particle, the breakdown seemed to be initiated in the inter-electrode gap in CO2 and at the crossing in SF6, while for the 8 mm particle, breakdown occurred at lift-off in both gases. A parameter k describing the width of the t... [more]

There are systems dedicated to measuring the eccentricity of enameled wires based on optical and electromagnetic phenomena. However, these methods are limited by the nature of the insulation and the conductor. The proposed solution consists of checking the wire eccentricity by an electrical measurement. Since it is a conductor on which an insulator is placed, the idea consists of forming a capacitor and measuring its capacitance in order to deduce the insulation thickness.

As an economic corridor, the Silk Road Economic Belt (SREB) connects the East to Western nations, where carbon emissions are gradually becoming severe. This study aims to provide solutions for dealing with carbon emissions from the transportation of the SREB in the Chinese range. By employing the Malmquist index method of data envelopment analysis (DEA), this study develops models to test the different carbon-reduction performances (CRP) of transportation in the Chinese provinces along the SREB. This study shows that carbon-reduction performance has improved since 2013 because of the improvements in transportation technology. Technical efficiency, including scale efficiency and pure technological efficiency, may improve carbon reduction, while the lagged technological progress restricts the CRP. It is further suggested that the provincial CRPs are different. The southwest provinces have the best decarbonization performance, followed by the northwest, while the northeast provinces, incl... [more]

Contrary to the assumption of previous researchers, the radial temperature in the petroleum reservoir during production is non-isothermal because several heat transfer mechanisms change the radial temperature in reservoirs. As there have been few studies, especially after long-term production, this work derives steady-state analytic solutions considering the long-term production. It also presents sensitivity analysis with the various production conditions to investigate heat transfer between the producing fluids and surrounding formations during fluids flowing (hereafter, system heat transfer) in a steady-state. For oil production, the system heat transfer induces a cooling effect on the radial temperature in the reservoir, reducing the temperature rise due to the Joule−Thomson (J−T) heating. This cooling effect increases with the larger Peclet number, however, the relative contribution of the cooling effect to the radial temperature change diminishes. The equations explain that the co... [more]

This paper presents a flux-weakening model predictive control (FW-MPC) for the interior permanent magnet synchronous motor (IPMSM) drive system. The FW control is a strategy to extend the IPMSM’s operating region. However, the primary FW needs to track the torque reference and maximize the electrical torque per current amplitude with the current and voltage limitations. The two objects make it impossible to solve the FW problem using the optimization method. We proposed an equivalent optimization problem to simplify the complex FW problem, including two objective functions. The MPC is selected as the controller due to its high robustness and transient performance. The constraints from the equivalent optimization problem are added in the MPC to control the IPMSM in the FW region. The simulation and experiment results indicate that the proposed FW-MPC is feasible and effective in driving the IPMSM in the FW region. The proposed FW-MPC can find the optimal point with the maximum electrica... [more]

The greater demand for high-quality iron ores has forced the iron and steel industries to utilize low-grade iron ores, such as banded hematite quartzite (BHQ). In the present work, a striped hematite quartzite sample from the Haraginadoni area, in the Sandur schist belt, Ballari District, Karnataka, India, was subjected to characterization studies and conventional mineral processing methods to produce pellet-grade concentrate, assayed as Fe > 63.0%, SiO2 + Al2O3 < 7%, (Al2O3/SiO2 < 0.5). The sample was analyzed as 35.70% Fe, 47.44% SiO2, 0.75% Al2O3, 0.06% Mn, 0.07% TiO2, 0.03% P, 0.02% S, and 0.83% LOI. We focused on two routes of beneficiating BHQ samples: (1) conventional gravity followed by reverse floatation and (2) magnetic separation followed by cleaning of magnetic concentrate by reverse floatation. Route 1, achieved pellet-grade concentrate through assaying, and was 63.73% Fe, 6.20% SiO2, 0.19% Al2O3, 0.03% Al2O3/SiO2, and 0.23% LOI, D80 45 µm, with 70.1% Fe recovery and... [more]