By using text mining techniques, this study identifies the topics of sustainable consumption that are important during the COVID-19 pandemic. An Application Programming Interface (API) streaming method was used to extract the data from Twitter. A total of 14,591 tweets were collected using Twitter streaming API. However, after data cleaning, 13,635 tweets were considered for analysis. The objectives of the study are to identify (1) the topics users tweet about sustainable consumption and (2) to detect the emotion-based sentiments in the tweets. The study used Latent Dirichlet Allocation (LDA) algorithm for topic modeling and the Louvain algorithm for semantic network clustering. NRC emotion lexicon was used for sentiment analysis. The LDA model discovers six topics: organic food consumption, food waste, vegan food, sustainable tourism, sustainable transport, and sustainable energy consumption. While the Louvain algorithm detects four clusters—lifestyle and climate change, responsible c... [more]

Currently, more than 30% of the fine dust generated in the Seoul metropolitan area is a pollutant emitted from automobiles such as diesel vehicles, and air pollution caused by this is becoming increasingly serious. In addition, the importance of electric vehicle distribution is increasing due to the strengthening of international environmental regulations on automobile exhaust gas and increasing the possibility of depletion of petroleum resources. This manuscript proposes a method for selecting an optimal electric vehicle charging station location in expanding charging facilities to activate electric vehicle distribution. For the sake of illustration, directions will be provided on how to select the best location for electric vehicle charging stations using data from Seoul, which has the best access. As the features, the number of living population and work force people and the number of guest facilities, which are determined to affect demand for quick charging, are considered. The mis... [more]

Bubble flow can be simulated by the two-fluid model and the multi-fluid model based on the Eulerian method. In this paper, the gas phase was further divided into several groups of dispersed phases according to the diameter by using the Eulerian-Eulerian (E-E) multi-fluid model. The diameters of bubbles in each group were considered to be the same, and their distributions were reorganized according to a specific probability density function. The experimental data of two kinds of bubble flow with different characteristics were used to verify the model. With the help of the open-source CFD software, OpenFOAM-7.x (OpenFOAM-7.0, produced by OpenFOAM foundation, Reading, England), the influences of the group number, the probability distribution function, and the parameters of different bubble diameters on the calculation results were studied. Meanwhile, the numerical simulation results were compared with the two-fluid model and the experimental data. The results show that for the bubble flow... [more]

The solar chimney is one of the uninvestigated areas in the possible selection in the field of renewable solar energy utilization. CFD can be demonstrated as a useful tool of figure confidence in the design and employment of a solar chimney. A realistic numerical model for a solar-based updraft power plant for power generation was established through this research work. Iraqi weather in Kirkuk, northern Iraq was considered for this case study. A three-dimensional (3D) simulation of the main geometric dimensions of the Spanish, Manzanares model integrated with a real turbine was performed using computational fluid dynamics (CFD). The turbulent model of RNG k-e, the nongrey discrete coordinate (DO) radiation model, and the solar raytracing algorithm were used. It was observed that the air velocity below the turbine was graded according to the seasons of the year and was at its maximum in July with 18.28 m/s due to the high ambient temperature, and the lowest value was recorded in January... [more]

In the present work, a network model for the numerical resolution of the heat transport problem in porous media coupled with a water flow is presented. Starting from the governing equations, both for 1D and 2D geometries, an equivalent electrical circuit is obtained after their spatial discretization, so that each term or addend of the differential equation is represented by an electrical device: voltage source, capacitor, resistor or voltage-controlled current source. To make this possible, it is necessary to establish an analogy between the real physical variables of the problem and the electrical ones, that is: temperature of the medium and voltage at the nodes of the network model. The resolution of the electrical circuit, by means of the different circuit resolution codes available today, provides, in a fast, simple and precise way, the exact solution of the temperature field in the medium, which is usually represented by abaci with temperature-depth profiles. At the end of the ar... [more]

The Ecuador’s expansion plans for the power sector promote the exploitation of hydro power potential, natural gas and a small share of alternative renewable energies. In 2019, electricity generation reached 76.3% from hydroelectric power, 21.9% from thermal plants and 1.8% from other renewable resources. Although the power energy mix is mainly based on renewable technologies, the total energy demand is still dependent on fossil fuels, which is the case of the transport sector that alone accounted for 50% of the total primary energy consumed in the country. This paper analyzes the pathway to develop a clean and diversified electricity mix, covering the demand of three specific development levels of electric transportation. The linear optimization model (urbs) and the Ecuador Land Use and Energy Netwrok Analysis (ELENA) are used to optimize the expansion of the power system in the period from 2020 to 2050. Results show that reaching an electricity mix 100% based on renewable energies is... [more]

Power suppliers in a dynamic power market can achieve full benefit by introducing a bidding strategy mechanism. In the power sector, renewable resources have significant gradual usage and their effect on the production of detailed bidding approaches is becoming further complicated in the industry. Due to the irregular nature of these renewable resources and because they are subject to several fluctuations, there is an inherent issue with generating electricity. Taking these considerations into account, attempts have been made to create a model of bidding strategy to optimize the benefit of the electricity producers using the oppositional gravitational search algorithm. The Weibull and Beta distribution functions are utilized to describe the stochastic characteristics of the wind-speed profile and solar-irradiation, respectively. For the IEEE-30 and IEEE-57 frameworks, the suggested method is being checked and explained. In comparison to other optimization approaches, the results of thi... [more]

Energy system modelling is an essential practice to assist a set of heterogeneous stakeholders in the process of defining an effective and efficient energy transition. From the analysis of a set of open-source energy system models, it emerged that most models employ an approach directed at finding the optimal solution for a given set of constraints. On the contrary, a simulation model is a representation of a system used to reproduce and understand its behaviour under given conditions without seeking an optimal solution. In this paper, a new open-source energy system model is presented. Multi Energy Systems Simulator (MESS) is a modular, multi-energy carrier, multi-node model that allows the investigation of non optimal solutions by simulating an energy system. The model was built for urban level analyses. However, each node can represent larger regions allowing wider spatial scales to be represented as well. In this work, the tool’s features are presented through a comparison between... [more]

Frequency response analysis (FRA) is a powerful and widely used tool for condition assessment in power transformers. However, interpretation schemes are still challenging. Studies show that FRA data can be influenced by parameters other than winding deformation, including temperature. In this study, a machine-learning approach with temperature as an input attribute was used to objectively identify faults in FRA traces. To the best knowledge of the authors, this has not been reported in the literature. A single-phase transformer model was specifically designed and fabricated for use as a test object for the study. The model is unique in that it allows the non-destructive interchange of healthy and distorted winding sections and, hence, reproducible and repeatable FRA measurements. FRA measurements taken at temperatures ranging from −40 °C to 40 °C were used first to describe the impact of temperature on FRA traces and then to test the ability of the machine learning algorithms to discri... [more]

A laboratory-scale chamber is convenient for combustion scenarios in the practical analysis of industrial explosions and devices such as internal combustion engines. The safety risks in hazardous areas can be assessed and managed during accidents. Increased hydrogen usage in renewable energy production requires increased attention to the safety issues since hydrogen produces higher explosion overpressures and flame speed and can cause more damage than methane or propane. This paper reports numerical simulation of turbulent hydrogen combustion and flame propagation in the University of Sydney's small-scale combustion chamber. It is used for the investigation of turbulent premixed propagating flame interaction with several solid obstacles. Obstructions in the direction of flow cause a complex flame front interaction with the turbulence generated ahead of it. For numerical analysis, OpenFOAM CFD software was chosen, and a custom-built turbulent combustion solver based on the progress vari... [more]

The yokeless and segmented armature axial flux machine is considered an excellent topology for electric vehicles application. However, its performance is severely limited by the stator cooling system. The heat pipe, as the small size, lightweight, but highly efficient passive phase-change cooling element, has been attracting more and more attention in the thermal management methods of electric motors. Therefore, the relationship between the thermal performance of the heat pipe with temperature is measured in detail through an experimental test platform in this paper. Further, a novel stator cooling structure that combines the heat pipe with the housing water-cooling method is introduced to improve the temperature distribution of the stator. Computational fluid dynamics (CFD) simulation verifies that the proposed cooling structure can accelerate the release of heat from the stator and reduce the temperature of the stator significantly.

Due to the existence of a Dean vortex in a U-tube, the flow and heat transfer process of supercritical methane is complex, and its thermophysical property are greatly influenced by different factors. Based on computational fluid dynamics theory, the numerical simulation of the turbulent flow and heat transfer characteristics of supercritical methane in a U-tube with an inner diameter of 10 mm and a radius of curvature of 27 mm carried out by using the finite volume method. On the basis of verifying the reliability of the model, the influences of inlet mass flux (G), heat flux on the tube wall boundary (q), pressure on the outlet (P), and gravity acceleration factors (g) on heat transfer characteristics were analyzed. The calculation results show that the sensitivity of the effects of G, q, P, and g on the heat transfer coefficient is, from large to small, in the order of P, G, g, and q. Compared with a horizontal straight tube, a U-tube can significantly improve heat transfer in the el... [more]

In cold climatic regions such as those located across Canada, it is necessary to implement heating system technology that is ultra-efficient and that has near-zero rates of emissions. Such systems would satisfy consumers’ energy needs and also comply with environmental standards, especially because the systems would account for more than 80% of residential energy use. This paper investigates two complementary efficient systems that can support these heating systems; ground-source heat pumps (GSHPs) and organic Rankine cycle systems (ORCs). The study proposes to couple these two systems in a parallel configuration. A dynamic simulation model created in TRNSYS platform has been deployed to assess the performance of the combined ORC-GSHP based micro-cogeneration system. This former provides heating to a residential house during the heating mode as needed. It has the capacity to switch to a charging mode, during which the ORC system is directly coupled to the ground heat exchanger (GHE), w... [more]

A series of large eddy simulations was conducted to analyze conjugate heat transfer characteristics in a ribbed channel. The cross section of the rib is square and the blockage ratio is 0.1. The pitch between the ribs is 10 times the rib height. The Reynolds number of the channel is 30,000. In the simulations, the effect of the thermal resistance of the solid wall of the channel on convective heat transfer was observed in the turbulent flow regime. The numerical method used was based on the immersed boundary method and the concept of effective conductivity is introduced. When the conductivity ratio between the solid wall and the fluid (K*) exceeded 100, the heat transfer characteristics resembled those for an isothermal wall, and the cold core fluid impinging and flow recirculation mainly influenced the convective heat transfer. For K* ≤ 10, the effect of the cold core fluid impinging became weak and the vortices at the rib corners strongly influenced the convective heat transfer; the... [more]

Beginning with the classic methods, a mathematical model of an electromechanical system is developed that consists of a deep bar cage induction motor that, via a complex motion transmission with distributed mechanical parameters, drives a working machine, loading the drive system with a constant torque. The electromagnetic field theory serves to create the motor model, which allows addressing the displacement of current in the rotor cage bars. Ordinary and partial differential equations are used to describe the electromechanical processes of energy conversion in the motor. The complex transmission of the drive motion consists of a long shaft with variable geometry cardan joints mounted on its ends. Non-linear electromechanical differential equations are presented as a system of ordinary differential equations combined with a mixed problem of Dirichlet first-type and Poincaré third-type boundary conditions. This system of equations is integrated by discretising partial derivatives by me... [more]

Cable fire caused by arc faults is one of the essential factors threatening the safe operation of a power system. The ignition and flame propagation of cable fire dependent on the characteristics of the arc discharge is lackingin in-depth understanding at present. In this work, with the constant electric power deposited into the arc discharge, the effects of arc size on the ignition and flame propagation of 110 kV XLPE cable fire are investigated for the first time. The arc size is changed by varying the gap distance of electrodes from 1.5 cm to 2.5 cm. It is interesting to find that the larger the arc size is, the faster the cable fire is ignited and propagates, and the larger the damaged area of the sheath of the cable is. Therein, when the gap distance increases from 1.3 cm to 3.1 cm, the equivalent impedance and the length of the arc discharge increase nearly seven times and three times, respectively. However, the gas temperature of the arc decreases slightly from 2280 K to 2100 K.... [more]

Methane, as a clean energy source and a potent greenhouse gas, is produced in marine sediments by microbes via complex biogeochemical processes associated with the mineralization of organic matter. Quantitative modeling of biogeochemical processes is a crucial way to advance the understanding of the global carbon cycle and the past, present, and future of climate change. Here, we present a new approach of dynamic transport-reaction model combined with sediment deposition. Compared to other studies, since the model does not need the methane concentration in the bottom of sediments and predicts that value, it provides us with a robust carbon budget estimation tool in the sediment. We applied the model to the Blake Ridge region (Ocean Drilling Program, Leg 164, site 997). Based on seafloor data as input, our model remarkably reproduces measured values of total organic carbon, dissolved inorganic carbon, sulfate, calcium, and magnesium concentration in pore waters and the in situ methane p... [more]

In this paper, new methods for determining the pressure drop in internal channels of a hydraulic motor are proposed and described. Mathematical models of pressure losses in internal channels have also been described. Experimental tests of the satellite motor were carried out according to one of the proposed methods. The tests were carried out for two liquids, i.e., water and mineral oil. Experimental studies have shown that at a high flow rate in the motor supplied with water the pressure losses are a dozen or so percent greater than in the motor supplied with oil. However, at low flow rates is the inverse, that is, the pressure losses in the motor supplied with water are about ten percent lower than in the motor supplied with oil. The CFD calculation of the pressure drop in the internal channel of the motor was also conducted. It was assumed that holes in the commutation unit plate are placed face to face and that the liquid did not cause changes in the working chambers’ volume. In th... [more]

In this paper, a seasonal performance analysis of a hybrid ejector cooling system is carried-out, by considering a multi-ejector pack as expansion device. A 20 kW ejector-based chiller was sized to obtain the optimal tradeoff between performance and investment costs. The seasonal performance of the proposed solution was then evaluated through a dynamic simulation able to obtain the performance of the designed chiller with variable ambient temperatures for three different reference climates. The optimized multi-ejector system required three or four ejectors for any reference climate and was able to enhance the system performance at partial load, with a significant increase (up to 107%) of the seasonal energy efficiency ratio. The proposed system was then compared to conventional cooling technologies supplied by electric energy (electrical chillers EHP) or low-grade heat sources (absorption chillers AHP) by considering the total costs for a lifetime of 20 years and electric energy-specif... [more]

Industrial Waste Heat Recovery (IWHR) is one of the areas with strong potential for energy efficiency and emissions reductions in industry. Thermoelectric (TE) generators (TEGs) are among the few technologies that are intrinsically modular and can convert heat directly into electricity without moving parts, so they are nearly maintenance-free and can work unattended for long periods of time. However, most existing TEGs are only suitable for small-scale niche applications because they typically display a cost per unit power and a conversion efficiency that is not competitive with competing technologies, and they also tend to rely on rare and/or toxic materials. Moreover, their geometric configuration, manufacturing methods and heat exchangers are often not suitable for large-scale applications. The present analysis aims to tackle several of these challenges. A module incorporating constructive solutions suitable for upscaling, namely, using larger than usual TE elements (up to 24 mm in... [more]

Thermal analysis represents a key factor in electrical machine design due to the impact of temperature increase on insulation lifetime. In this context, there has been a wide investigation on thermal modeling, particularly for machines used in harsh working conditions. In this perspective, brake-by-wire (BBW) systems represent one of the most challenging applications for electrical machines used for automotive smart actuators. Indeed, electro-actuated braking systems are required to repeatedly operate the electric machine in high overload conditions in order to limit the actuator response time, as well as to enhance gravimetric and volumetric specific performance indexes. Moreover, BBW systems often impose unconventional supply conditions to the electric machine, consisting of dc currents in three-phase windings to keep the rotor fixed during the braking intervals. However, a dc supply leads to uneven temperature distributions in the machine, and simplified thermal models may not accur... [more]

Cities take a central place in today’s energy landscape. Urban Buildings Energy Modeling (UBEM) is identified as a promising approach for energy planning and optimization in cities and districts. It generally relies on the use of Building Archetypes, i.e., simplified deterministic models for categorized building typologies. However, this implies large assumptions which may accumulate and induce significant bias on energy consumption estimates. In this work, we address this issue with static stochastic models whose parameters are inferred over national thermo-energy data using Bayesian Inference. We analyze inference results and validate them with a panel of standard indicators. Then, we provide comparative results with deterministic building archetypes and stock data from the TABULA European project. Comparisons between heat loss coefficients show relative coherence between building categories, but highlight some significant bias between both approaches. This bias is also shown in the... [more]

Energy system modeling is essential in analyzing present and future system configurations motivated by the energy transition. Energy models need various input data sets at different scales, including detailed information about energy generation and transport infrastructure. However, accessing such data sets is not straightforward and often restricted, especially for energy infrastructure data. We present a detection model for the automatic recognition of pipeline pathways using a Convolutional Neural Network (CNN) to address this lack of energy infrastructure data sets. The model was trained with historical low-resolution satellite images of the construction phase of British gas transport pipelines, made with the Landsat 5 Thematic Mapper instrument. The satellite images have been automatically labeled with the help of high-resolution pipeline route data provided by the respective Transmission System Operator (TSO). We have used data augmentation on the training data and trained our mo... [more]

The development of green energy conversion devices has been promising to face climate change and global warming challenges over the last few years. Energy applications require a confident performance prediction, especially in polymer electrolyte fuel cell (PEFC), to guarantee optimal operation. Several researchers have employed optimization algorithms (OAs) to identify operating parameters to improve the PEFC performance. In the current study, several nature-based OAs have been performed to compute the optimal parameters used to describe the polarization curves in a PEFC. Different relative humidity (RH) values, one of the most influential variables on PEFC performance, have been considered. To develop this study, experimental data have been collected from a lab-scale fuel cell test system establishing different RH percentages, from 18 to 100%. OAs like neural network algorithm (NNA), improved grey-wolf optimizer (I-GWO), ant lion optimizer (ALO), bird swarm algorithm (BSA), and multi-... [more]

Workshops with a large area and a high ceiling height without compartments, such as large-scale assembly factories, have an uneven thermal comfort during heating, making it difficult to establish an effective heating strategy. In this study, we evaluate the heating performance of a large-scale factory based on thermal comfort and energy flow and discuss effective heating methods. In addition, an analysis of the heating performance of a large-scale factory is attempted for the first time. To analyze the heating performance, computational fluid dynamics (CFD) and building energy simulation (BES) were used to confirm thermal comfort distribution and energy flow in a large-scale factory. Temperature distribution and thermal comfort were evaluated through CFD, and the temperature of a large-scale assembly factory was compared with experimental data. Based on the CFD results, the current heating level of large factories was predicted to be 15.4 °C, and the ADPIrev was 70%. Moreover, the BES... [more]