The building sector consumes as much as 80% of generated electricity in the UAE; during the COVID-19 pandemic, the energy consumption of two sub-sectors, i.e., commercial (50%) and residential (30%), was significantly impacted. The residential sector was impacted the most due to an increase in the average occupancy during the lockdown period. This increment continued even after the lockdown due to the fear of infection. The COVID-19 pandemic and its lockdown measures can be considered experimental setups, allowing for a better understanding of how users shift their consumption under new conditions. The emergency health measures and new social dynamics shaped the residential sector’s energy behavior and its increase in electricity consumption. This article presents and analyzes the identified issues concerning residential electricity consumers and how their behaviors change based on the electricity consumption data during the COVID-19 period. The Dubai Electricity and Water Authority co... [more]

The geometry of a conventional two-bladed Savonius rotor was used in this study based on a report available in the literature. A two-dimensional rotor model consisting of two buckets and an overlap ratio of 0.1 was prepared. The unsteady Reynolds averaged Navier-Stokes (URANS) equations and the eddy-viscosity turbulence model SST k-ω were employed in order to solve the fluid motion equations numerically. Instantaneous velocities and pressures were calculated at defined points around the rotor and then averaged. The research shows that the operating rotor significantly modifies the flow on the downwind part of the rotor and in the wake, but the impact of the tip speed ratio on the average velocity distribution is small. This parameter has a much greater influence on the characteristics of the aerodynamic moment and the distribution of static pressure in the wake. In the upwind part of the rotor, the average velocity parallel to the direction of undisturbed flow is 29% lower than in the... [more]

Smart buildings are becoming a new standard in construction, which allows for many possibilities to introduce ergonomics and energy savings. These contain simple improvements, such as controlling lights and optimizing heating or air conditioning systems in the building, but also more complex ones, such as indoor movement tracking of building users. One of the necessary components is an indoor localization system, especially without any device worn by the person being located. These types of solutions are important in locating people inside smart buildings, managing hospitals of the future and other similar institutions. The article presents a prototype of an innovative energy-efficient device for radio tomography, in which the hardware and software layers of the solution are presented. The presented example consists of 32 radio sensors based on a Bluetooth 5 protocol controlled by a central unit. The preciseness of the system was verified both visually and quantitatively by the image r... [more]

Changes in the energy sector, associated with the move away from fossil fuels, pose a challenge for appropriate thermal energy management in residential buildings. The important element to deal with the variability of renewable energy in thermal systems is latent heat thermal energy storage. Due to the low thermal conductivity of phase change materials, a number of techniques are proposed to enhance the heat transfer process. In this research, the global sensitivity of fin geometrical parameters on the melting and solidification times and energy efficiency of these processes was investigated. The computational model of the phase change was developed using the finite volume method with the enthalpy-porosity model and Boussinesq approximation. Numerical simulations were carried out according to the design of experiments technique. The multi-dimensional response surface was developed, and the multi-objective optimisation was done. The research shows that the melting process is most influe... [more]

The variations in the boiler operation conditions have a great effect on the combustion characteristics and the pollutant formation in furnaces. This work aims to investigate the effects of operational parameters on NOx formation and its distribution in furnaces using the numerical simulation method to obtain the optimum control strategy for reducing NOx emissions. The numerical simulation models of pulverized coal combustion in furnaces involving flow, heat transfer, combustion and NOx formation are established. Taking a 600 MW supercritical opposed firing pulverized coal boiler as the study object, a full-scale three-dimensional physical model of the boiler is constructed with Gambit software. On this basis, the pulverized coal combustion and the NOx formation under various boiler loads are numerically simulated using the software of Ansys Fluent 2021R1, and the accuracy and the reliability of the models established are verified by comparing the simulation data with the field test da... [more]

In this study, the fracture propagation characteristics and associated mechanisms of coal are investigated by using computed tomography (CT) observation and image-based simulation. The spatial distribution and the structural morphology of original fractures provide significant influences on the failure behavior of fractured coal. The fractures with small dip angles and large openings result in more-obvious fracture closure and stable propagation stages, while failure pattern is more sensitive to those with large dip angles. The coal tends to experience brittle failure, which transits from a splitting to mixed-splitting faulting mode because of the difference in original fracture distribution. The final failure fracture network originates mainly from the propagation of original fractures, driven by localized tensile stress. Fracture interaction and mineral influence tend to increase the complexity in the failure fracture network. Moreover, image-based numerical models are established on... [more]

Lignin depolymerization has been studied for decades to produce carbon-neutral chemicals/biofuels and biopolymers. Among different chemical reaction pathways, catalytic hydrogenolysis favors reactions under relatively mild conditions, while its yield of bio-oil and high-value aromatic products is relatively high. In this study, the influence of reaction parameters on lignin hydrogenolysis are discussed by chemical process parameter mapping and modeled using three different machine learning algorithms based upon literature experimental data. The best R2 scores for solid residue and aromatic yield were 0.92 and 0.88 for xgboost, respectively. The parameter importance was examined, and it was observed that lignin-to-solvent ratio and average pore size have a larger impact on lignin hydrogenolysis results. Finally, the optimal conditions of lignin hydrogenolysis were predicted by chemical process parameter mapping using the best-fit machine learning model, which indicates that further proc... [more]

The generation of entropy and mixed convection in a nanofluid-filled 3D wavy tank containing a rotating cylinder is investigated. The top wavy surface of the tank is heated and all vertical surfaces are assumed to be adiabatic, while the bottom horizontal surface remains isothermally cold. The tank contains a solid cylinder and is saturated with an Al2O3−water nanofluid. The numerical simulations using the FEM are performed for the Richardson number (0.01≤Ri≤100), nanoparticle volume fraction (0≤ϕ≤0.04) and number of oscillations (0≤N≤4). The numerical results of the present work are given in terms of 3D streamlines, isotherms and local entropy generation, as well as average heat transfer and Bejan number. The results show that for low values of the Richardson number and oscillation, heat transfer enhancement can be achieved by increasing the nanoparticle volume fraction.

During the rebuilding of a gas reservoir, repeated “strong injection and mining” processes change the seepage capacities of gas and water. Hence, accurately determining the seepage laws of gas and water in a gas storage reservoir is crucial. In this study, a standard relative permeability test was conducted with a one-dimensional core. Additionally, a gas reservoir injection and mining simulation experiment was conducted with a two-dimensional plate. The results show that the relative permeability curve obtained by the one-dimensional core test did not accurately reflect the operation characteristics of the gas storage and the change in the seepage law during the gas reservoir construction. Furthermore, in the two-dimensional plate experiment, the operation mode was restored using the plane radial flow formula, the mutual relationship between the gas and water’s effective permeability under different injection stages was established, and the multi-cycle injection operation was accurate... [more]

Several rural regions located in Africa are experiencing recurrent and even permanent problems in terms of energy production, supply, and distribution to citizens. This study was conducted to investigate the relevance of the use of a new solar technology that is gradually responding in Europe and in industrialized countries. It is about the use of hybrid photovoltaic thermal (PV/T) solar panels that co-produce electricity and hot water for local use. Furthermore, in Africa, local use of solar energy can provide a share in the energy mix. This work is motivated by the lack of studies on these hybrid solar panels in tropical climates. Hence, the paper examines the potential for integration of these systems in small households. A complete PV/T system consisting of solar panels, pump, storage tank, batteries, and controllers was tested and calibrated by using the TRNSYS simulation tool. A comparative study could thus be carried out for the performance of PV/T in a tropical climate (case of... [more]

This paper addresses issues related to modeling energy consumption and emissions using microscopic traffic simulations. This paper develops a method in which a traffic model is used to calculate the energy needed to travel through selected types of intersections. This paper focuses on energy consumption and derived values of calculated energy, which can be, for example, carbon dioxide emissions. The authors present a review of the scientific literature on the study of factors affecting energy consumption and emissions and methods to estimate them in traffic. The authors implemented an energy consumption model into a microsimulation software module to estimate results as a function of varying traffic volumes at selected types of intersections and for selected traffic organization scenarios. The results of the study show the lowest energy consumption and the lowest emissions when road solutions are selected that contribute to reducing vehicle travel times on the urban street network at h... [more]

The development of the electric power industry needs to be understood against the current backdrop of the transition to technological platforms facilitating the adoption of smart grids. Smart grids can be made up of separate clusters (microgrids) consisting of power consumers, power grids, and distributed generation (DG) units. To improve energy efficiency, DC microgrids can be integrated into smart grids to deliver power to consumers within a building (or several buildings) and at the sites of C&I facilities. It is advisable to carry out integrations of DC and AC microgrids with DG and energy storage units on the basis of power routers used to couple grids of different voltage classes. This study outlines a computer model of power router-based integration of DC and AC microgrids with distributed generation and energy storage units. The model was developed in the MATLAB environment. The paper also features the results of a study of the proposed methods as applied to voltage control und... [more]

The main aim of this work is to propose a new algorithm of reliability assessment for steel civil engineering structures subjected to fire temperatures. This new algorithm is based upon the relative probabilistic entropy concept elaborated by Bhattacharyya, and this probabilistic distance is sought in-between extreme and admissible deformations of some structural beam subjected to higher temperatures. Similar to the First Order Reliability Method, this approach uses the first two probabilistic characteristics of the structural response, when structural output may be modelled with the use of Gaussian distribution. The probabilistic structural response is found here using hybrid computational technique−the Finite Element Method system ABAQUS with its fully coupled thermo-elastic analysis with 3D solid elements and probabilistic modules implemented in the computer algebra system MAPLE. The probabilistic response is determined via a triple stochastic analysis, which is based on the classic... [more]

Protonic ceramic fuel cells (PCFCs) are one of the promising and emerging technologies for future energy generation. PCFCs are operated at intermediate temperatures (450−750 °C) and exhibit many advantages over traditional high-temperature oxygen-ion conducting solid oxide fuel cells (O-SOFCs) because they are simplified, have a longer life, and have faster startup times. A clear understanding/analysis of their specific working parameters/processes is required to enhance the performance of PCFCs further. Many physical processes, such as heat transfer, species transport, fluid flow, and electrochemical reactions, are involved in the operation of the PCFCs. These parameters are linked with each other along with internal velocity, temperature, and electric field. In real life, a complex non-linear relationship between these process parameters and their respective output cannot be validated only using an experimental setup. Hence, the computational fluid dynamics (CFD) method is an easier... [more]

A wave energy converter features the ability to convert wave energy into the electrical energy required by unmanned devices, and its energy-conversion efficiency is an essential aspect in practical applications. This paper proposes a novel point-absorption wave energy converter with passive morphing blades to meet the demand for improved energy-conversion efficiency. We first introduce its concept and design, with its blades forming their shape by adaptive changes with the direction of the water flow. Next, the three-dimensional geometrical-morphing model, energy-conversion model, and energy-conversion-efficiency model of the wave energy converter were established. Then, the CFD model was built to optimize the design parameters, and the simulation results revealed that the maximum conversion efficiency can be obtained at 90% solidity with 10 blades, a 40−60% load, and 20~25 degrees for the external deflection angle. The simulations also showed that the passive morphing-blade group prov... [more]

Classification is one of the most common methods of supervised learning, which is divided into a process of data acquisition, data mining, feature analysis, machine learning algorithm selection, model learning and validation, as well as prediction of the result, which was done in the current work. The data that were analyzed concerned ionizing radiation signals generated by partial discharges, recorded by a method using the phenomenon of scintillation. It was decided to check if the data could be classified and if it was possible to determine the defect of an electrical power device. It was possible to find out which classifier (algorithm) worked best for the task, and that the data obtained can be classified, as well as that it is possible to determine the defect. In addition, it was possible to check what effect changing the default values of the classifier’s parameters has on the effectiveness of classification.

Liquid foams exist in a wide variety of chemical and industrial processes, and they can contaminate the end-product and cause time and economical losses. Understanding and simulating foam is not a straightforward task, due to the highly dispersed time and length scales where the physical phenomena occur. Surfactants’ or proteins’ length scales are far beyond the capability of macroscopic and even mesoscopic numerical fluid solvers, yet the macroscales are still required to be resolved. Meanwhile, the lattice Boltzmann method (LBM) has gained much attention and success as a mesoscopic approach which can deal with complex multiphase multicomponent systems. The aim of this study is to implement LBM to simulate liquid foams while considering the accompanying thermal effects. A coupled multiphase multicomponent thermal flow model and its selected add-ons from the literature are tuned and explained, limitations and future suggestions are fairly discussed. Validations and a final study case a... [more]

The vision of decarbonization creates the need to design and construct even more energy-efficient buildings. This current target is even more compelling and challenging. The main issue when designing energy-efficient buildings is to identify present and future building energy requirements. A trending method for solving this problem is dynamic building energy simulation. One of the main inputs during energy simulation is weather data. However, the real problem lies in the fact that standard weather data are good at defining the present situation, and they help in designing buildings that behave efficiently under current climate conditions. To achieve the goal of constructing climate proof buildings, the Weather Research and Forecast meteorological model (WRF) was used to predict future climate scenarios. At first, data from previous years (2006−2010) were used to represent the current climate. The model was used to generate future climate data. Thus, results were produced for 5 year per... [more]

The application of cross-linked polyethylene (XLPE) cables to voltage sourced converter (VSC)-based high voltage direct current (HVDC) systems has already been technically verified and has become common, and thermoplastic (TP) is attracting attention as an insulation material for next-generation cables due to the recent development of material-related technologies. However, studies related to TP cables are mainly focused on improving material properties, and studies related to cable systems are insufficient. In this paper, XLPE and TP cables were designed for application to VSC-based HVDC systems, and major characteristics such as electric field distribution and thermal stability were compared and analyzed through overvoltage simulation. The insulation design method of HVDC cable was presented, and the design was performed using XLPE and TP insulation materials. The temperature and electric field profiles of the cables were also analyzed through a finite element method simulation. To a... [more]

High-voltage direct current (HVDC) links are starting to become widely implemented thanks to their interesting advantages such as reduced operation losses, the absence of reactive power, which allows energy transport via underground cables over long distances, and improved power control. The latter advantage is very essential for renewable energy resource integration into power grids. However, a thorough understanding of the behavior of insulation systems for HVDC components is critical so as to ensure a more reliable service. Indeed, the existence of the direct current (DC) voltage in HVDC components may induce surface and space charge accumulation that can stress insulation further or even promote discharge inception and propagation. As such, this work focuses on showcasing the effect of surface charge on streamers that develop on the interface of liquid−solid insulation due to the advent of lightning impulse (LI) voltage in the HVDC link. This study was performed using finite-elemen... [more]

Carbon monoxide is often produced during the incomplete combustion of volatile organic carbon compounds in industry. In the combustion chamber for oxidizing carbon monoxide emissions, a penta-coaxial port device can be used to improve the process of mixing the fuel and oxidizer. In this study, the conjugate heat transfer analysis was conducted by solving both Reynolds-averaged Navier−Stokes equations with the eddy dissipation model and solid heat conduction equation in the wall using Fluent 2019R2 to simulate the reaction flow of a volatile organic carbon compound burner and heat transfer of the stack insulation layer. The mass fractions of the O2, CO2, and CO gases; the temperature; and the velocity distribution in a combustion chamber were computed to investigate how various design parameters of the combustor, including air inlet size and stack height, and air inflow conditions affected the combustion performance. Results show that the size of the air inlet had only a minor effect on... [more]

This paper investigates magnet demagnetization characteristics of the modular permanent magnet machine. The influence of flux gaps on magnet flux density, losses distribution, torque and demagnetization are analyzed for different operating conditions. The magnet demagnetizations caused by three sources, such as the PM field, the armature field, and the magnet temperature rise, are individually investigated using the frozen permeability method. Furthermore, coupled electromagnetic (EM)-thermal modelling is also adopted in this paper to fully reveal the advantages of the modular machine in improving machine EM performances. This is essential due to the temperature-dependent properties of the machines, such as the magnet remanence, coercivity, and copper resistivity. For comparison propose, the EM performances with a particular focus on the demagnetization withstand capability for both the modular and non-modular machines are investigated based on the EM-thermal coupling. It is found that... [more]

The key to ensuring the economic feasibility of EGS mainly includes two points. On the one hand, it is necessary to ensure the connectivity of the artificial fracture network; on the other hand, it is necessary to determine the most efficient geothermal energy exploitation mode. Most previous studies have only focused on one of the points. To restitute the entire geothermal energy development process, the two parts should be combined to conduct research. In this study, a random fractured medium model was established based on the TOUGH2-BIOT simulation program and the whole process of reservoir stimulation was analyzed. According to the results of reservoir stimulation, different geothermal energy exploitation schemes are set up, and the heat transfer efficiency of the conventional double vertical wells, the horizontal wells, and the double-pipe heat exchange system are comparatively analyzed. The results show that reservoir reconstruction is mainly divided into three stages: In the fir... [more]

With the increasing constraints on energy and resource markets and the non-decreasing trend in energy demand, the need for relevant clean energy generation and storage solutions is growing and is gradually reaching the individual home. However, small-scale energy storage is still an expensive investment in 2022 and the risk/reward ratio is not yet attractive enough for individual homeowners. One solution is for homeowners not to store excess clean energy individually but to produce hydrogen for mutual use. In this paper, a collective production of hydrogen for a daily filling of a bus is considered. Following our previous work on the subject, the investigation consists of finding an optimal buy/sell rule to the grid, and the use of the energy with an additional objective: mobility. The dominant technique in the energy community is reinforcement learning, which however is difficult to use when the learning data is limited, as in our study. We chose a less data-intensive and yet technica... [more]

The performance degradation issue caused by carbon deposition has limited the commercial application of natural-gas-fueled solid oxide fuel cells. Most previous corresponding studies are based on thermodynamic equilibrium analyses, while long-term transient evaluation work is lacking. Therefore, a transient multi-physics numerical model is developed in present work. The corresponding long-term performance degradation evaluation is then conducted. The results show that, for a direct internal reforming solid oxide fuel cell, the increase in carbon deposition and deterioration of performance degradation were concentrated in the first 180 days of steady−state operation and slowed down at the later stage. The electrode inlet rapidly developed a high concentration of carbon deposition after 180 days of steady−state operation. The deposited carbon deteriorated the gas transport and decayed reaction activity within the porous electrode, eventually inducing a deactivation zone with 0 current de... [more]