The paper presents an analysis of the hygrothermal performance of an inverted flat roof with a CLT (cross-laminated timber) structure in a building that meets the requirements of Passive House Standard (PHS) with regards to the potential risk of moisture. The calculations were made in the WUFI®Plus and WUFI®Bio software. The following variants were taken into account: three structure configurations, three different external climates and different scenarios of microclimate control and air change rate. The results of the calculations show that, especially in cooler climates, there is an actual moisture risk in the structure despite the excellent thermal insulation. The structure of the inverted flat roof, due to the use of a tight membrane on the outer side, allows for the partition to discharge the excess moisture only to the inside of the building. Ensuring the comfort of users may require periodic humidification of internal air, which translates directly into an increase in moisture c... [more]

Analyses and comparisons of generic models and a novel modeling method of line-commutated converter (LCC)-based high voltage direct current (HVDC) systems are presented for the power system simulator for engineering (PSS/E) simulation tool. The main purposes are to describe the dynamics of the DC voltage and current of HVDC system and to improve estimation of the maximum values using the generic and proposed HVDC models when AC line-to-ground faults are occurred. For the generic HVDC models, the characteristics and limitations as well as parameter investigations are conducted. Three modules are also are developed for the proposed HVDC model, which are composed of (a) AC/DC conversion; (b) controller selection; and (c) DC line model. Case studies were conducted considering the real-operated HVDC system in Korea under the PSS/E and power systems computer aided design (PSCAD) simulation environments. The simulation results were compared with measured data from the real-operated HVDC syste... [more]

The temperature properties of real-type direct-current gas-insulated transmission lines (DC-GIL) with a basin-type spacer were investigated by the finite element method in this paper. A horizontally installed model was established and the temperature distribution was obtained with a 3D model. The specific heat capacity and thermal conductivity of the spacer were measured and applied in the simulation. The results show that the temperature of the convex surface was slightly higher than that of the concave surface. With an increase in the SF6 pressure, the temperature of the spacer decreased, which can be attributed to the improvement of convection due to increases in the heat capacity per unit volume. With an increase in the ambient temperature, the temperature of the spacer increased linearly. The temperature difference between the inner and outer parts of the spacer increased with increases in the load current. Besides, an obvious increase in the surface electric field strength appear... [more]

The e-commerce industry has been developing extremely dynamically for many years. This development was intensified during the COVID-19 pandemic. According to the research conducted by the authors of this paper, in Poland, during the pandemic, the number of delivered parcels increased 20−100%, depending on the courier company. The research of the authors of this article focused on the energy efficiency of the last mile, which is very important for the efficiency of the entire delivery process to customers. As the authors calculated, the last mile can consume over 70% of energy of the whole distribution channel. The article presents the results of research concerning the energy efficiency of deliveries performed by couriers and express companies in Poland. Two models of distribution used Poland have been compared—direct deliveries to final customers, and deliveries to parcel lockers. The research methods are interviews with the managers and couriers, analysis of the literature, and the s... [more]

The removal of solids is the most important step when treating rainwater. The article evaluates two designs of sedimentation tanks that can be used for the continuous separation of fine particles from water: OS—standard sedimentation tanks, and OW—swirl sedimentation tanks. The tanks were studied by conducting computational fluid dynamics (CFD) modeling and particle image velocimetry (PIV) experiments. The settling process in sedimentation tank was carried out at varying operating flow rates. A tank with a modified structure was used for the tests, where water was supplied by a nozzle placed at an angle. This solution made it possible to obtain a rotational flow that transported the suspended particles towards its wall, where downward axial velocity resulted in the settling of particles. Based on the research, it was observed that the flow patterns showed inward flow at the bottom of the tank and an upward flow and the lifting of the settled particles near the hatch at the bottom. The... [more]

In this work, a data-driven methodology for modeling combustion kinetics, Learned Intelligent Tabulation (LIT), is presented. LIT aims to accelerate the tabulation of combustion mechanisms via machine learning algorithms such as Deep Neural Networks (DNNs). The high-dimensional composition space is sampled from high-fidelity simulations covering a wide range of initial conditions to train these DNNs. The input data are clustered into subspaces, while each subspace is trained with a DNN regression model targeted to a particular part of the high-dimensional composition space. This localized approach has proven to be more tractable than having a global ANN regression model, which fails to generalize across various composition spaces. The clustering is performed using an unsupervised method, Self-Organizing Map (SOM), which automatically subdivides the space. A dense network comprised of fully connected layers is considered for the regression model, while the network hyper parameters are o... [more]

Minimum miscible pressure (MMP) is an essential design parameter of gas flooding for enhanced oil recovery (EOR) applications. Researchers have developed a number of methods for MMP computations, including the analytical methods, the slim-tube simulation method, and the multiple-mixing-cell (MMC) method. Among these methods, the MMC method is widely accepted for its simplicity, robustness, and moderate computational cost An important version of the MMC method is the Jaubert et al. method which has a much lower computational cost than the slim-tube simulation method. However, the original Jaubert et al. method suffers several drawbacks. One notable drawback is that it cannot be applied to the scenario where the oil-gas MMP is lower than the saturation pressure of the crude oil. In this work, we present a modified MMC method that is more versatile and robust than the original version. Our method can handle the scenario where the oil-gas MMP is lower than the saturation pressure of the cr... [more]

This study focuses on optimizing a 100-W-class β-Type Stirling engine by combining the modified thermodynamic model and the variable-step simplified conjugate gradient (VSCGM) method. For the modified thermodynamic model, non-uniform pressure is directly introduced into the energy equation, so the indicated power and heat transfer rates can reach energy balance while the VSCGM is an updated version of the simplified conjugate gradient method (SCGM) with adaptive increments and step lengths to the optimization process; thus, it requires fewer iterations to reach the optimal solution than the SCGM. For the baseline case, the indicated power progressively raises from 88.2 to 210.2 W and the thermal efficiency increases from 34.8 to 46.4% before and after optimization, respectively. The study shows the VSCGM possesses robust property. All optimal results from the VSCGM are well-matched with those of the computational fluid dynamics (CFD) model. Heating temperature and rotation speed have p... [more]

Electric vehicles may reduce greenhouse gas emissions from individual mobility. Due to the long charging times, accurate planning is necessary, for which the availability of charging infrastructure must be known. In this paper, we show how the occupation status of charging infrastructure can be predicted for the next day using machine learning models— Gradient Boosting Classifier and Random Forest Classifier. Since both are ensemble models, binary training data (occupied vs. available) can be used to provide a certainty measure for predictions. The prediction may be used to adapt prices in a high-load scenario, predict grid stress, or forecast available power for smart or bidirectional charging. The models were chosen based on an evaluation of 13 different, typically used machine learning models. We show that it is necessary to know past charging station usage in order to predict future usage. Other features such as traffic density or weather have a limited effect. We show that a Gradi... [more]

Due to the development of dedicated software and the computing capabilities of modern computers, the application of numerical methods to analyse more complex geotechnical problems is becoming increasingly common. However, there are still some areas which, due to the lack of unambiguous solutions, require a more thorough examination, e.g., the numerical simulations of displacement pile behaviour in soil. Difficulties in obtaining the convergence of simulations with the results of static load tests are mainly caused by problems with proper modelling of the pile installation process. Based on the numerical models developed so far, a new process of static load test modelling has been proposed, which includes the influence of pile installation on the soil in its vicinity and modelling of contact between steel pile and the soil. Although the presented method is not new, this is relevant and important for practitioners that may want to improve the design of displacement piles. The results of... [more]

In this paper, we study how uncertainties weighing on the climate system impact the optimal technological pathways the world energy system should take to comply with stringent mitigation objectives. We use the TIAM-World model that relies on the TIMES modelling approach. Its climate module is inspired by the DICE model. Using robust optimization techniques, we assess the impact of the climate system parameter uncertainty on energy transition pathways under various climate constraints. Unlike other studies we consider all the climate system parameters which is of primary importance since: (i) parameters and outcomes of climate models are all inherently uncertain (parametric uncertainty); and (ii) the simplified models at stake summarize phenomena that are by nature complex and non-linear in a few, sometimes linear, equations so that structural uncertainty is also a major issue. The use of robust optimization allows us to identify economic energy transition pathways under climate constra... [more]

This numerical investigation presents the effects of the position of baffles in the shape of a circle’s segment placed inside a circular channel to improve the thermal and flow performance of a solar air heater. Three different baffles’ positions with Reynolds number varying between 10,000 to 50,000 were investigated computationally. The k-omega SST model was used for solving the governing equations. Air was taken as the working fluid. Three pitch ratios (Y = 3, 4, and 5) were considered, while the height of the baffles remained fixed. The result showed an enhancement in Nusselt number, friction factor, j-factor, and thermal performance factor. Staggered exit-length baffles showed maximum enhancement in heat transfer and pressure drop, while inline inlet-length baffles showed the least enhancement. For a pitch ratio of Y = 3.0, the enhancement in all parameters was the highest, while for Y = 5.0, the enhancement in all parameters was the least. The highest thermal performance factor of... [more]

Underground mining machines, such as wheel-tyre drilling rigs, are articulated and equipped with booms that project far beyond the undercarriage. Such a structure makes these machines prone to losing stability. Hence, it is necessary to analyse the distribution of masses and geometry as well as their broadly understood stability during the entire design process, taking into account many factors resulting from the manner and conditions of their operation. However, there are no appropriate computational models that would enable analytical tests to be carried out for machines with this kind of construction. This article is concerned with the author’s computational model, which allows the stability of single- and twin-boom drilling rigs to be quickly assessed. The model makes it possible to perform analyses without having to solve differential equations that are present in dynamic models or using specialist software based on CAD and CAE tools. The developed model allows determination of th... [more]

A 1.2 kV SiC MOSFET with an integrated heterojunction diode and p-shield region (IHP-MOSFET) was proposed and compared to a conventional SiC MOSFET (C-MOSFET) using numerical TCAD simulation. Due to the heterojunction diode (HJD) located at the mesa region, the reverse recovery time and reverse recovery charge of the IHP-MOSFET decreased by 62.5% and 85.7%, respectively. In addition, a high breakdown voltage (BV) and low maximum oxide electric field (EMOX) could be achieved in the IHP-MOSFET by introducing a p-shield region (PSR) that effectively disperses the electric field in the off-state. The proposed device also exhibited 3.9 times lower gate-to-drain capacitance (CGD) than the C-MOSFET due to the split-gate structure and grounded PSR. As a result, the IHP-MOSFET had electrically excellent static and dynamic characteristics, and the Baliga’s figure of merit (BFOM) and high frequency figure of merit (HFFOM) were increased by 37.1% and 72.3%, respectively. Finally, the switching ene... [more]

Nowadays reducing green-house gas emissions and pushing the fossil fuel savings in the field of light-duty vehicles is compulsory to slow down climate change. To this aim, the use of new combustion modes and dilution strategies to increase the stability of operations rich in diluent is an effective technique to reduce combustion temperatures and heat losses in throttled operations. Since the combustion behavior in those solutions highly differs from that of typical market systems, fundamental analyses in optical engines are mandatory in order to gain a deep understanding of those and to tune new models for improving the mutual support between experiments and simulations. However, it is known that optical accessible engines suffer from significant blow-by collateral flow due to the installation of the optical measure line. Thus, a reliable custom blow-by model capable of being integrated with both mono-dimensional and three-dimensional simulations was developed and validated against exp... [more]

To predict the temperature distribution of the tooth surface of a herringbone gear pair, a numerical method for the determination of frictional heat generation was proposed by establishing a thermal elastohydrodynamic lubrication (TEHL) model in the meshing zone taking surface roughness into account. According to the real micro topography of the tooth surface measured by a non-contact optical system and loaded tooth contact analysis, the friction coefficient was obtained by a TEHL analysis and then the heat generation in the contact zone was determined. With the combination of heat generation and heat dissipation analysis, the single tooth model of the herringbone gear pair due to the finite element method (FEM) was proposed and the steady-state temperature distribution of the tooth surfaces was predicted by FEM simulations. The simulation and the experimental results demonstrated good agreement, which verified the feasibility of the present numerical method.

This article presents the modeling, simulation and experimental validation of the movement of the floating bearing bushing in an external gear pump. As a starting point, a complete pump parameterization was carried out through standard tests, and these parameters were used in a first bond graph model in order to simulate the gear pump behavior. This model was experimentally validated under working conditions in field tests. Then, a sophisticated bond graph model of the movement of the floating bushing was developed from the equations that define its lubrication. Finally, as a result, both models were merged by integrating the dynamics of the floating bushing bearing with the variation of the characteristic parameters (loss coefficients). Finally, the final model was experimentally validated both in laboratory and field tests by assembling the pump in a drilling machine to drive the auxiliary movements. The novelty of this article is the conception and construction of a simple and exper... [more]

Gas and oil pipelines are widely used to supply customers. They are often laid in parallel with high voltage power lines, sharing right of way. When the pipeline is located near overhead high-voltage power, corrosion caused by induced voltages from AC power lines can occur in utility pipelines. Therefore, the calculation of induced voltage is always required for both interference and maintenance workers as well as pipeline facility safety. For parallel distribution lines, the calculation method for the induced voltage is not suitable due to the excessive error caused by using the screening factors of the neutral current. For a more practical analysis of the induced voltage, a new analysis is needed using the actual neutral current and which also considers the overhead ground conductor and the neutral conductor. This paper analyzed the induced voltage from a parallel distribution system using Carson’s formula and vector analysis. Simulation analysis results are verified by separate Elec... [more]

This article presents the concept of a method of improving the dynamics of combustion in boilers operating in power plants, cogeneration plants, and heating plants by introducing a catalyst that is fed with a carrier in the form of droplets. Thanks to the proposed method, a greater degree of fuel burnout can be obtained, which, in turn, results in lower energy consumption in the case of producing the same amount of power. The parameters of the emitted exhaust gases and ash are also improved. The method described in the article involves the adding of a catalyst to the dust pipe of the boiler, which improves the combustion parameters. The catalyst was implemented using a sprayer/nebulizer. In order to obtain the correct flow parameters, the sprayer was modeled using CFD calculations. The calculations include trajectories, velocities and concentrations with regards to various flow parameters. Particular attention should be paid to the model of the evaporation of moving droplets. The resul... [more]

This paper presents a Hybrid Excited Double-Sided Linear Flux Switching Machine (HEDSLFSM) with a crooked tooth modular stator. Generally, the conventional stators are made of a full-length iron core, increasing manufacturing costs and iron losses. Higher iron losses result in lower efficiency and lower overall performance. A U-shaped modular stator with a crooked tooth is used to lower iron consumption and increase the machine’s efficiency. Ferrite magnets are used to replace rare earth magnets, which also reduces the machine cost. Two DC excitation windings are used above and below the ferrite magnet to reduce the PM volume. 2D electromagnetic performance analysis is done to observe the key performance indices. Geometric optimization is used to optimize the Split Ratio (S.R), DC winding slot area (DCw), and AC winding slot area (ACw). Stator Tooth Width (STW), space between the modules (S.S.), and crooked angle (α) are optimized through JMAG in-built Genetic Algorithm (G.A.) optimiza... [more]

The pumped-storage power station is an efficient stability regulator of the power grid. However, due to the instability of the pump-turbine in the S-shaped characteristic region, rotational speed fluctuation is easy to occur in the speed no-load condition, making synchronization with and connection to the grid difficult. To investigate the key factors of these difficult grid connections, the start-up processes of a practical pump-turbine under the lowest head condition were simulated by using the three-dimensional CFD method, in which the governor regulating equations with different regulating parameters were integrated successfully. The results show that the working points oscillate with the fluctuations of rotational speed, discharge, and torque, and different regulating parameters have a significant influence on the dynamic histories. In addition, the internal flow patterns, especially the backflows at the runner inlet, keep apparent values at the middle span (0.5 span) but have reg... [more]

In recent years, many researchers across the world have addressed the implementation of Building Information Modelling (BIM) in the energy assessment of the built environment. However, several potential issues still need to be resolved in order to utilise the benefits provided by BIM to a maximum degree. To fill this gap, a systematic literature review is conducted in this study to critically investigate the utilisation of BIM tools in energy assessment. To achieve the above-mentioned objective, after shortlisting the relevant papers published hitherto, using keyword searching, a systematic review was undertaken, including the application of BIM in the contexts of different countries, types of BIM tools, BIM and Life Cycle Assessment (LCA) integration, energy affiliations, stakeholders’ involvement and their roles, uncertainty, and sensitivity analysis. The outcomes show the most widely used and effective BIM tools in different types of construction projects in various countries. The r... [more]

This paper discusses some design issues of a magnetic rotating to linear motion converter (RLMC), suitable for the propulsion system of a short-distance low-capacity vehicle. It basically operates like a magnetic rack, which executes the contactless conversion of the motor torque into a propulsion thrust, deriving from the interaction of on-board permanent magnet (PM) modules and stationary ferromagnetic steel pieces. A design procedure is set up that deals with both the PM module arrangement and the geometric shape of the steel pieces to optimize different performance aspects. A simplified modeling based on 2D transient finite element analyses is carried out to determine the thrust profile and the RLMC losses, which are essential to assess its practical feasibility. Finally, the characteristics as functions of the load angle and speed are determined to enable the prediction of the dynamic power exchange and then of the net energy demand useful to size the on-board source.

Agro-photovoltaic systems are of interest to the agricultural industry because they can produce both electricity and crops in the same farm field. In this study, we aimed to simulate staple crop yields under agro-photovoltaic panels (AVP) based on the calibration of crop models in the decision support system for agricultural technology (DSSAT) 4.6 package. We reproduced yield data of paddy rice, barley, and soybean grown in AVP experimental fields in Bosung and Naju, Chonnam Province, South Korea, using CERES-Rice, CERES-Barley, and CROPGRO-Soybean models. A geospatial crop simulation modeling (GCSM) system, developed using the crop models, was then applied to simulate the regional variations in crop yield according to solar radiation reduction scenarios. Simulated crop yields agreed with the corresponding measured crop yields with root mean squared errors of 0.29-ton ha−1 for paddy rice, 0.46-ton ha−1 for barley, and 0.31-ton ha−1 for soybean, showing no significant differences accord... [more]

With the emergence of new technologies and policies to transition to clean energy, the household energy consumption sector is also changing. In response to policy, environmental, and technical changes, researchers need to find out what significant issues are related to household energy consumption, and comprehensively analyze which issues are likely to attract attention in the future to contribute to research in the household sector. Based on the abstracts of academic papers published between 2011 and 2020, this study uses probabilistic topic modeling to increase understanding of academic issues in the household energy consumption sector and statistically reviews changes in issues over time. As a result of the analysis, topics related to digitalization and renewable energy, such as microgrid system, smart home, residential solar power generation systems, and non-intrusive load monitoring (NILM), belonging to Strong signals, are being actively studied. Weak Signals, which can attract at... [more]