Electric Vehicles (EVs) are becoming one of the main answers to the decarbonization of the transport sector and Renewable Energy Sources (RES) to the decarbonization of the electricity production sector. Nevertheless, their impact on the electric grids cannot be neglected. New paradigms for the management of the grids where they are connected, which are typically distribution grids in Medium Voltage (MV) and Low Voltage (LV), are necessary. A reform of dispatching rules, including the management of distribution grids and the resources there connected, is in progress in Europe. In this paper, a new paradigm linked to the design of reform is proposed and then tested, in reference to a real distribution grid, operated by the main Italian Distribution System Operator (DSO), e-distribuzione. First, in reference to suitable future scenarios of spread of RES-based power plants and EVs charging stations (EVCS), using Power Flow (PF) models, a check of the operation of the distribution grid, in... [more]

While filtration, chlorination, and UV drinking water treatments are commonplace, globally an estimated 1.2 billion people continue to boil their drinking water over inefficient biomass fires instead because it allows them to use available resources paired with a time-tested and trusted method. Although boiling water is culturally well-established, there is vast potential to improve human health, environmental impact, and efficiency by leveraging the fact that a significant reduction in pathogenic microorganisms occurs at temperatures well below boiling through a process known as pasteurization. This paper presents the evaluation of a community-scale, biomass-powered, flow-through water pasteurization system that was designed to heat water to the temperature required for pasteurization to occur before recuperating heat while cooling treated water down to a safe-to-handle temperature. The system is then compared to other common thermal treatment methods including batch-boiling over open... [more]

Although improving the hydrodynamic performance is a key objective in the design of ocean-powered devices, there are some factors that affect the efficiency of the device during its operation. In this study, the impacts of a wide range of surface roughness as a tribological parameter on stream flow around a hydro turbine and its power loss are studied. A comprehensive program of 3D Computational Fluid Dynamics (CFD) modeling, as well as an expansive range of experiments were carried out on a Darrieus Hydro (DH) turbine in order to measure reduction in hydrodynamic performance due to surface roughness. The results show that surface roughness of turbine blades plays an important role in the hydrodynamics of the flow around the turbine. The surface roughness increases turbulence and decreases the active fluid energy that is required for rotating the turbine, thereby reducing the performance of the turbine. The extent of the negative impact of surface roughness on the drag coefficient, pre... [more]

A modified computational fluid dynamic (CFD) model has been developed to obtain oil removal efficiency for oily wastewater treatment in large-scale flotation tanks. According to the investigation of oil droplet/bubble interactions in a flotation tank, a modified Bloom−Heindel model is used to calculate the collision and attachment efficiencies between oil droplets and bubbles. Effects of the gas flow rate, oil diameter and oil concentration on oil removal efficiency of flotation tank were analyzed experimentally. The application scope of this modified CFD model is evaluated using experimental results. In addition, the comparison between the existing model and the modified model demonstrates that this modified CFD model can make a good prediction for the separation performance of the flotation tank.

Currently, thanks to the rapid development of wireless sensor networks and network traffic monitoring, the data stream is gradually becoming one of the most popular data generating processes. The data stream is different from traditional static data. Cluster analysis is an important technology for data mining, which is why many researchers pay attention to grouping streaming data. In the literature, there are many data stream clustering techniques, unfortunately, very few of them try to solve the problem of clustering data streams coming from multiple sources. In this article, we present an algorithm with a tree structure for grouping data streams (in the form of a time series) that have similar properties and behaviors. We have evaluated our algorithm over real multivariate data streams generated by smart meter sensors—the Irish Commission for Energy Regulation data set. There were several measures used to analyze the various characteristics of a tree-like clustering structure (comput... [more]

Motion states of bottom hole assembly (BHA) have a great effect on the trajectory control and drilling efficiency while rotary drilling. In order to study the motion states of BHA in horizontal wells, a BHA dynamic model with the finite element method was established. Meanwhile, an indoor experimental setup based on similarity criterion was designed and built to verify the numerical simulation results. Finally, the effects of measuring positions, rotate speeds, weight on bit (WOB), and friction coefficients on the motion states were analyzed in numerical simulation and experiment. The results show that the experimental results can match well with the numerical simulation results. The motion states of BHA in horizontal wells can be divided into three kinds, including circular arc swing, "8" shape swing, and dot-like circular motion. The circular arc swing mainly appears at middle section of BHA and occurs through the collective result of gravity and tangential friction. The dot-like cir... [more]

This work aimed to study the bubble distribution in a multiphase pump. A Euler-Euler inhomogeneous two-phase flow model coupled with a discrete particle population balance model (PBM) was used to simulate the whole flow channel of a three-stage gas-liquid two-phase centrifugal pump. Comparison of the computational fluid dynamic (CFD) simulation results with experimental data shows that the model can accurately predict the performance of the pump under various operating conditions. In addition, the liquid phase velocity distribution, gas-phase distribution, and pressure distribution of the second stage impeller at a 0.5 span of blade height under three typical working conditions were compared. Results show that the region with high local gas volume fraction (LGVF) mainly appears on the suction surface (SS) of the blade. With the increase in inlet gas volume fraction (IGVF), vortices and low velocity recirculation regions are generated at the impeller outlet and SS of the blade, the area... [more]

The bifacial photovoltaic (PV) systems have recently met large interest. The performance of such systems heavily depends on the installation conditions and, in particular, on the albedo radiation collected by the module rear side. Therefore, it is of crucial importance to have an accurate performance model. To date, in the scientific literature, numerous models have been proposed and experimental data collected to study and optimize bifacial PV system performance. Currently, 3D and 2D models of bifacial PV devices exist. Though the former are more mathematically complex, they can lead to more accurate results, since they generally allow to fully consider the main aspects influencing a bifacial PV system performance. Recently, we have proposed and validated through experimental data a 3D model tested as a function of module height, tilt angle, and ground albedo. In this work, through such a model, we studied the role played by the perimeter zones surrounding the PV string, by considerin... [more]

Mining at the fully mechanized working face below the goaf of the short-distance coal seam is influenced by the upper goaf. To address this problem, methods such as theoretical analyses, numerical simulation, and on-site measurement are used to study the strata behavior characteristics of the Ningxia Lingxin Coal Mine 051508 working face in this study. The roof weighting intervals of the working faces below the goaf and the non-goaf are obtained via theoretical calculations. The stoping processes of the working faces below the goaf and the non-goaf are simulated with FLAC3D to obtain the distribution law of the bearing pressure and plastic zones before the working face. Based on the statistical analysis of the measured working resistance of the supports and its distribution, the roof weighting interval of the working face mining below the goaf is obtained. The results show that the roof weighting interval and the advanced abutment pressure during mining at the working face below the go... [more]

This paper presents a novel approach for Voltage Stability Margin (VSM) estimation that combines a Kernel Extreme Learning Machine (KELM) with a Mean-Variance Mapping Optimization (MVMO) algorithm. Since the performance of a KELM depends on a proper parameter selection, the MVMO is used to optimize such task. In the proposed MVMO-KELM model the inputs and output are the magnitudes of voltage phasors and the VSM index, respectively. A Monte Carlo simulation was implemented to build a data base for the training and validation of the model. The data base considers different operative scenarios for three type of customers (residential commercial and industrial) as well as N-1 contingencies. The proposed MVMO-KELM model was validated with the IEEE 39 bus power system comparing its performance with a support vector machine (SVM) and an Artificial Neural Network (ANN) approach. Results evidenced a better performance of the proposed MVMO-KELM model when compared to such techniques. Furthermore... [more]

The paper deals with the three-dimensional theoretical and numerical investigation of the electrical performance of a Photovoltaic System (PV) with active fluid cooling (PVFC) in order to increase its efficiency in converting solar radiation into electricity. The paper represents a refinement of a previous study by the authors in which a one-dimensional theoretical model was presented to evaluate the best compromise, in terms of fluid flow rate, of net power gain in a cooled PV system. The PV system includes 20 modules cooled by a fluid circulating on the bottom, the piping network, and the circulating pump. The fully coupled thermal and electrical model was developed in a three-dimensional geometry and the results were discussed with respect to the one-dimensional approximation and to experimental tests. Numerical simulations show that a competitive mechanism between the power gain due to the cell temperature reduction and the power consumption of the pump exists, and that a best comp... [more]

In order to study the deformation displacement and the stress field of brittle rocks under harmonic dynamic loading, a series of systematic numerical simulations are conducted in this paper. A 3D uniaxial compression simulation is carried out to calibrate and determine the property parameters of sandstone and a model of the cylindrical indenter intruding the rock is proposed to analyze the process of elastic deformation. Four main parameters are taken into account, namely the position on the rock, the frequency and the amplitude of dynamic load, the type of indenter and the loading conditions (static and static-dynamic). Based on the analysis undertaken, it can be concluded that both of the deformation displacement and stress field of the rock change in a harmonic manner under the static-dynamic loads. The frequency and the amplitude of harmonic dynamic load determine the period and the magnitude of the rock response, respectively. In addition, the existence of harmonic dynamic load ca... [more]

This article presents a method for the Maximum Power Point Tracking (MPPT) of a Photovoltaic (PV) panels array with partial shading, applying an Improved Pattern Search Method (IPSM). The method is simulated in PSIM @ and then implemented in hardware in the loop system, emulating the PV array on an industrial computer (Speedgoat) that allows real-time emulations and the IPSM is applied in an Arduino DUE. The experiments were carried out with TP245S-20/WD, KYOCERA KC200GT, YINGLY SOLAR JS65, and MSX60 photovoltaic panels. The results are the proper MPPT with changes in partial shading over time, inducing the increase and decrease of the maximum power point. The results obtained are the search for the global maximum power point in a matrix of panels in which, due to partial shading, it might have several local maximum power points, and thanks to the IPSM algorithm, it always manages to find the global maximum power point. Finally, the results are compared with other methods where... [more]

Climate change and the increase of the consumption of energy resources are expected to further strain anticipated water stress scenarios. The operation of existing thermal plants depends greatly on their cooling capacity, for which large amounts of water are withdrawn and consumed. Dry-cooling systems, on the other hand, do not require water, but they are less efficient and more expensive relative to conventional water-based systems, because of their dependency on the ambient temperature. This paper introduces the new idea of replacing water-based cooling systems in thermal power plants with earth-cooling air tunnels. Based on the concept of existing earth-air heat exchangers, the system takes advantage of the low and relatively constant underground temperature for cooling ambient air before it is introduced in the air condenser of the plant. In this work, we present an initial design of such an open-loop system for a 20 MW concentrated solar power plant. A sensitivity study of both ge... [more]

Dynamic energy modelling of buildings is a key factor for developing new strategies for energy management and consumption reduction. For this reason, the EnergyPlus software was used to model a near-zero energy building (Smart Energy Buildings, SEB) located in Savona, Italy. In particular, the focus of the present paper concerns the modeling of the ground source water-to-water heat pump (WHP) and the air-to-air heat pump (AHP) installed in the SEB building. To model the WHP in EnergyPlus, the Curve Fit Method was selected. Starting from manufacturer data, this model allows to estimate the COP of the HP for different temperature working conditions. The procedure was extended to the AHP. This unit is a part of the air-handling unit and it is working as a heat recovery system. The results obtained show that the HP performance in EnergyPlus can closely follow manufacturer data if proper input recasting is performed for EnergyPlus simulations. The present paper clarifies a long series of mi... [more]

Scenario analysis combined with system and market modelling is a well-established method to evaluate technological and societal developments and their impacts on future energy pathways. This paper presents a process-oriented method for developing consistent energy scenarios using multiple energy system models. Its added value is that the developed energy scenarios are consistent in a multi-model environment and practicable for a broader target group from scientists to practitioners. The scenarios consist of comprehensive storylines and systematically defined quantitative parameters. Following a step-by-step process, a condensed set of overlapping descriptors is generated and used to define the scenarios in a consistent parameter matrix. The set of descriptors allow consistent and comparable outputs independent of model-specific characteristics. The corresponding quantitative parameters can be used by diverse energy system tools. Using multiple models, a team of researchers can explore... [more]

Oscillating water column (OWC) devices, either fixed or floating, are the most common wave energy converter (WEC) devices. In this work, the fluid dynamic interaction between waves and a U-shaped OWC breakwater embedding a Wells turbine has been investigated through unsteady Computational Fluid Dynamic (CFD) simulations. The full-scale plant installed in the harbor of Civitavecchia (Italy) was numerically modeled. A two-dimensional domain was adopted to simulate the unsteady flow, both outside and inside the U-OWC device, including the air chamber and the oscillating flow inside the conduit hosting the Wells turbine. For the numerical simulation of the damping effect induced by the Wells turbine connected to the air chamber, a porous medium was placed in the computational domain, representing the conduit hosting the turbine. Several simulations were carried out considering periodic waves with different periods and amplitudes, getting a deep insight into the energy conversion process fr... [more]

The deployment of highly efficient cooling equipment is expected to promote energy savings and greenhouse gas emissions reductions in the tropics. A ground source heat pump (GSHP) has high energy-savings potential for use in Bangkok, Thailand. This study aimed to elucidate the operational conditions of a GSHP when used in Bangkok which was expected to achieve a higher efficiency than an air source heat pump (ASHP) over the long term. An operational experiment on a pilot facility in Bangkok and a simulation over a three-year GSHP operation were conducted. As a result of the operational experiment and simulation, the proposed operational condition was that the 90th percentile value of the hourly heat pump (HP) inlet temperature did not exceed 5 °C above that of the hourly annual ambient temperature during the third year of operation. When a GSHP designed based on this condition was utilized for a small government building, the required number of boreholes were 24, 4, and 3 for air-condit... [more]

In order to calculate heat transfer capacity and air-side pressure drop of an annular radiator (AR), one performance calculation method was proposed combining heat transfer unit (HTU) simulation and plate-and-fin heat exchanger (PFHX) performance calculation formulas. This method can obtain performance data with no need for meshing AR as a whole, which can be convenient and time-saving, as grid number is reduced in this way. It demonstrates the feasibility of this performance calculation method for engineering applications. In addition, based on the performance calculation method, one configuration optimization method for AR using nondominated sorted genetic algorithm-II (NSGA-II) was also proposed. Fin height (FH) and number of fins in circumferential direction (NFCD) were optimized to maximize heat transfer capacity and minimize air-side pressure drop. Three optimal configurations were obtained from the Pareto optimal points. The heat transfer capacity of the optimal configurations i... [more]

Cellulosic insulation paper is usually used in oil-immersed transformer insulation systems. In this study, the molecular dynamics method based on reaction force field (ReaxFF) was used to simulate the pyrolysis process of a cellobiose molecular model. Through a series of ReaxFF- Molecular Dynamics (MD) simulations, the generation path of ethanol at the atomic level was studied. Because the molecular system has hydrogen bonding, force-bias Monte Carlo (fbMC) is mixed into ReaxFF to reduce the cost of calculation by reducing the sampled data. In order to ensure the reliability of the simulation, a model composed of 20 cellobioses and a model composed of 40 cellobioses were respectively established for repeated simulation in the range of 500−3000 K. The results show that insulating paper produced ethanol at extreme thermal fault, and the intermediate product of vinyl alcohol is the key to the aging process. It is also basically consistent with others’ previous experiment results. So it ca... [more]

Reynolds-stress closure modeling is critical to Reynolds-averaged Navier-Stokes (RANS) analysis, and it remains a challenging issue in reducing both structural and parametric inaccuracies. This study first proposes a novel algebraic stress model named as tensorial quadratic eddy-viscosity model (TQEVM), in which nonlinear terms improve previous model-form failure due to neglection of nonlocal effects. Then a data-driven regression model based on a fully-connected deep neural network is designed to determine the TQEVM coefficients. The well-trained data-driven model using high-fidelity direct numerical simulation (DNS) data successfully learned the underlying input-output relationships, further obtaining spatial-dependent optimal values of these coefficients. Finally, detailed validations are made in wall-bounded flows where nonlocal effects are expected to be significant. Comparative results indicate that TQEVM provides improvements both for the stress-strain misalignment and stress an... [more]

This paper presents a numerical method and computational results for acoustic noise of electromagnetic origin generated by an induction motor. The computation of noise incorporates three levels of numerical calculation steps, combining both the finite element method and boundary element method. The role of magnetic forces in the production of acoustic noise is established in the paper by showing the magneto-mechanical and vibro-acoustic pathway of energy. The conversion of electrical energy into acoustic energy in an electrical motor through electromagnetic, mechanical, or acoustic platforms is illustrated through numerical computations of magnetic forces, mechanical deformation, and acoustic noise. The magnetic forces were computed through 2D electromagnetic finite element simulation, and the deformation of the stator due to these forces was calculated using 3D structural finite element simulation. Finally, boundary element-based computation was employed to calculate the sound pressur... [more]

In this study, the 3ω method was used to determine the thermal conductivity of nanofluids (ethylene glycol containing multi-walled carbon nanotubes (MWCNTs)) with temperature gradients. The thermal modeling of the traditional 3ω method was modified to measure the spatial variation of thermal conductivity within a droplet of nanofluid. A direct current (DC) heater was used to generate a temperature gradient inside a sample fluid. A DC heating power of 14 mW was used to provide a temperature gradient of 5000 K/m inside the sample fluid. The thermal conductivity was monitored at hot- and cold-side 3ω heaters with a spacing of 0.3 mm. Regarding the measurement results for the hot and cold 3ω heaters, when the temperature gradient was applied, the maximum thermal conductivity difference was determined to be 3% of the original value. By assuming that the thermo-diffusion of MWCNTs was entirely responsible for this difference, the Soret coefficient of the MWCNTs in the ethylene glycol was cal... [more]

In this paper, a case study is conducted based on the real data obtained from the local Distribution System Operator (DSO) of electrical energy. The analyzed network represents connections and high-voltage switchgears of 110 kV. Selected graph parameters—vertex degree distribution, the average vertex degree, the graph density, network efficiency, the clustering coefficient, the average path length, and the graph diameter were examined, taking into account that in the analysis, some nodes were removed due to the different failures. For each failure, the possible effects on network parameters were tested. As a final result, it was shown that in the analyzed case, the removal of only five nodes could cause a significant (almost four times) fall of graph efficiency. In turn, this means that the whole analyzed network cannot be considered as a fault-tolerant.

A heat exchanger is a device that transfers unneeded heat from one region to another, and transferred heat may be fully reused, thus improving energy efficiency. To augment this positive process, many studies and investigations on automation technologies have been performed. Inserts are widely used in pipe flow for heat transfer enhancement, since they can break the boundary layer and promote the heat exchange. Segmented twisted tape, which is applicable in 3D printing, is a novel insert and has potential in heat transfer enhancement. To clarify its advantages and disadvantages, this research presents a numerical investigation of vortex flow and heat enhancement in pipes containing one segmented twisted element. Flow state and heat transfer behaviour are obtained by simulation under constant wall temperature with different Reynolds numbers, ranging from 10,000 to 35,000. The effects of geometric parameters, including twist ratio (P/D = 2.0, 3.3 and 4.6) and length ratio (L/P = 0.3, 0.5... [more]