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In computational fluid dynamics, defining precise boundary conditions, especially at inlets, is of great importance. Inlet flows typically exhibit natural turbulence, which is managed in various ways in scale-resolving simulations. Methods to establish turbulent inlet conditions are commonly created using natural transition, uncorrelated oscillations, periodic boundary conditions from auxiliary simulations, or synthetic turbulent fields. In this study, we explore a technique aimed at generating a divergence-free synthetic inflow turbulence with arbitrary anisotropy. The methodology is based on the conventional portrayal of turbulence as consisting of several coherent structures. While our approach adeptly emulates predefined statistical characteristics across different scales, its primary focus is on generating input parameters that impact the airflow within the wake of individual wind turbines and the atmospheric boundary layer within a wind farm. The results are compared with high-resolution velocity experimental measurements, large eddy simulations, and the digital filter-based inlet boundary condition already available in OpenFOAM. The findings demonstrate that the applied inflow generator outperforms the default OpenFOAM filter, particularly in the context of a single wind turbine. [ABSTRACT FROM AUTHOR]

Renewable energy sources like wind and solar have increased demand for surplus power capacity. The demand is primarily fueled by the growing impact of forecasting errors associated with these intermittent energy sources. Implementing advanced control methods for automatic generation control (AGC) is essential to integrate wind and solar power with conventional generation sources to balance the power system and reduce reliance on traditional reserves. Therefore, this paper comprehensively overviews solar and wind energy integration in the AGC framework to provide optimal grid ancillary services. Initially, the paper presents an overview of the basic equations used to integrate reserve power from the photovoltaic (PV) system by employing the de-loading strategy. Subsequently, a comprehensive review is conducted on integrating the PV system in AGC strategies to provide grid ancillary services. The study also analyzes the contribution of wind power in AGC services using relevant equations and past practices. The paper presents a real-time dynamic control strategy to optimize the dispatch of the AGC unit by integrating the operating reserves from wind energy systems in conjunction with thermal power systems. The study simulates an 8-bus, 5-machine model using the Dig-SILENT Power Factory. The findings reveal that utilizing operating reserves from wind power can significantly reduce large-scale forecasting errors in massively renewable energy resources (RES) integrated power systems, thereby ensuring the necessary system operational security and reducing the reliance on traditional generating units. [ABSTRACT FROM AUTHOR]

Solar energy is a rapidly growing sector, and agrivoltaic farms are playing an increasingly important role in meeting the world's energy needs. However, as the size and complexity of these farms increase, so do the challenges associated with managing them efficiently. This article presents a comprehensive review of the fundamental parameters that underpin agrivoltaic systems. Focusing on the latest research, this review examines the challenges and opportunities intrinsic to the implementation of agrivoltaic energy systems, paying particular attention to the various parameters that contribute to their performance. These parameters encompass a range of factors such as heat islands, shading factors, and surface energy budget. The review underscores the importance of considering a diverse array of parameters when developing agrivoltaic energy systems to optimize their efficiency and effectiveness. [ABSTRACT FROM AUTHOR]

In this study, a standalone solar parabolic dish Stirling system is mathematically modeled and simulated using MATLAB to investigate the effects of material design and opt-geometrical parameters on output performance of the system. The concentrator diameter, rim angle, dispersion angle, incidence angle, solar angle, receiver emissivity, receiver absorbance, receiver thermal conductivity, and concentrator reflectance are the major parameters considered for investigation. The effects of the aforementioned parameters have been rigorously observed on Geometrical Concentration Ratio (G.C.R), receiver temperature, receiver thermal loss, output power, and overall efficiency of the system. In addition, the optimized values of the studied parameters have also been identified to establish the optimal geometrical configuration of the system. The results revealed that the maximum output power and the overall efficiency of the system have been calculated at 45° rim angle, 0.4° dispersion angle, 0° incidence angle, and 0.3° solar angle. At these optimal angles, receiver thermal loss may be significantly minimized while maintaining the desired G.C.R. The results, for the purpose of validation, have also been compared with theoretical and experimental dataset from the contemporary literature and found in good agreement. [ABSTRACT FROM AUTHOR]

Laboratory experiments are conducted to inspect the modulation of model low-level-jet (LLJ) velocity profiles on the wake of a model wind turbine and power output fluctuations and a spectral structure of a simple two-turbine system in an aligned configuration. The scenario with a canonical incoming turbulent boundary layer profile is included for comparison. The results reveal a significant effect of the relative height of the LLJ peak velocity on the near and intermediate wake and power output fluctuations. Those effects are more notorious with the LLJ peak velocity coincident with the turbine top tip. The strong mean shear right above the wake promotes enhanced vertical transport and generation of energetic coherent motions. In particular, the near and intermediate wake velocity spectra showed a robust local signature with a streamwise length on the order of ∼4 times the rotor diameter. Although this shear layer did not significantly affect the spectrum of the power output fluctuations, the relatively large-scale velocity fluctuations may affect wind turbines' downwind in arrays. [ABSTRACT FROM AUTHOR]

The industrial sector is one of the major sources of environmental pollution. Industrial processes can generate many types of pollution including water pollution, soil pollution, air pollution, and noise pollution. With the expansion of industrial towns across Iran, this country has seen an increase in the amount of industrial pollutants. To tackle this issue, it is necessary to identify the factors that affect the development of green industries. This study aimed to identify and model the factors that influence the development of green industries and determine government policies and regulations that could be effective in reducing industrial pollution. First, the existing literature was reviewed, and 45 factors that can potentially affect the development of green industries were identified. Then the subject was further explored by designing and distributing a questionnaire with focus on a specific case, which was Mashhad industrial zone. The software SmartPLS was used to evaluate the fit of the developed model and then the structural equation modeling technique was employed to construct a model for the influential factors. The results showed that among the studied variables, seven variables have a significant impact on the development of green industries. The factor with the greatest effect on the development of green industries was found to be the "current situation of the industry," followed by "government incentives," "managerial commitment," "market for green products," "competition strategies," "government oversight," and "political affairs," respectively. [ABSTRACT FROM AUTHOR]

Conventional fossil fuel sources are being reduced and simultaneously became more and more sources of considerable undesirable influences on the environment. In an attempt to expand renewable energy sources, wind energy is playing a significant role. A doubly fed induction generator as an alternative concept of different prevalent generators in wind power industry has a conspicuous efficiency improvement impact. There are nonlinear dynamics and many uncertainties in wind power plants, such as matched and mismatched disturbances and uncertainties of parameters. Designing a convenient controller to address these nonlinearities and uncertainties is a problematic task and has been the topic of much great research. Sliding mode control is a powerful nonlinear high-frequency switching controller, which has been widely applied. In a more specialized scope, combining fractional order calculus with controllers provides more degrees of freedom for responding to the demands of existing fractional dynamics of systems. To this regard, this paper presents an adaptive fractional-order terminal sliding mode controller to extract maximum energy from a wind turbine based doubly fed induction generator, which as the name of the controller implies is adaptive and robust against uncertainties, improves control accuracy, reduces chattering and mechanical stresses, and speeds up response time. A novel and unique sliding surface has been selected for this controller. Lumped uncertainties and switching control signal parameters have been estimated by adaptation laws. Maximized aerodynamic wind energy has been harvested by utilizing the proposed controller for the rotor side converter. The Lyapunov theorem is applied to guarantee the closed-loop system stability. Under normal conditions and in the presence of uncertainty and disturbance, the proposed method has been compared with SMC and a feedback linearization proportional integral controller. [ABSTRACT FROM AUTHOR]

We experimentally explored the effect of a series of low-level-jet (LLJ) velocity profiles on the energy entrainment of a single and a pair of counter-rotating Giromill–Darrieus vertical-axis wind turbines (VAWTs) models under two types of rotations. Planar particle image velocimetry (PIV) was used to obtain the mean flow and turbulence statistics in the wake of the model wind turbines. Incoming LLJ profiles had peaks coincident with the turbines midspan and top tip; complementary flow characterization with a canonic turbulent boundary layer is also included for comparison. Results show that the positive shear region of the LLJ velocity profiles increased the wake asymmetry due to higher vertical velocity gradients. The positive shear of the LLJ contributed to the enhancement of energy entrainment in the wake compared with a standard turbulent boundary layer profile by increasing the mean kinetic energy advection into the wake in the single and a pair of counter-rotating VAWTs. Comparatively, high vertical velocity gradients may be responsible for this phenomenon; it promoted stronger cross-flow and counter-rotating vortices in the wake. [ABSTRACT FROM AUTHOR]

A data-driven approach is an alternative to extract general models for wind energy applications. A spatial sensitivity analysis is achieved using a probabilistic model to quantitatively identify the variability in performance due to individual parameters and visualize spatial distributions. Proper orthogonal decomposition results are combined with linear discriminant analysis under the clustering framework to present low-dimensional classifiers. Using the decomposition enables the system to be far away from ill-conditioned states. The optimal sensor locations are explicitly distributed in the transition region, where the velocity and Reynolds stresses relax toward a wake recovered state. With the optimal sensors, the cluster assignment and flow dynamics are obtained. There is an advantage in including more features in the reconstruction process to capture the slow and fast dynamics. Assessing the differences in the wake response and establishing the importance of spatial sensitivities are provided here for seeking accurate models. The bidirectional neural network is used to predict the fluctuating velocity of the considered sensors. The result of long–short term memory shows correlations of 92% between the real and predicted fluctuating velocities. [ABSTRACT FROM AUTHOR]

A common, worldwide atmospheric phenomenon known as a low-level jet (LLJ) offers benefits to wind energy production. Despite the fact that this effect may be used to increase the capacity factor of wind farms, the interaction between LLJs and wind power plants is not entirely known. By producing a synthetic LLJ velocity profile under well-controlled laboratory conditions, we show that this phenomenon enhances energy entrainment in the wake of wind turbines. The mechanism is associated with the increased velocity shear around the wind farm canopy height, which leads to higher turbulent mixing and, consequently, more energy flux for inner turbines within wind farms. The new insight from this work offers an opportunity to strategically develop, configure, and operate wind farms by taking into account the particular modulation of LLJs. [ABSTRACT FROM AUTHOR]

Nowadays, consumption of renewable energies such as solar energies is increasing. Electricity in solar systems is produced using either photovoltaics or concentrated solar power (CSP) systems. Therefore, concentrating technologies are key parts of CSP systems. The lower cost of linear Fresnel collectors makes them attractive for electricity production and thermal energy applications. However, due to partly losing the reflected rays, their optical efficiency is low. By installing a secondary reflector above the absorber tube of Fresnel collectors, lost rays are mostly redirected toward the absorber tube and a higher optical efficiency is achieved. The geometry and configuration of secondary reflectors have an intense influence on the optical efficiency. Therefore, there is a need to determine the most appropriate shape and configuration of secondary reflectors. In this study, four different types and orientations of secondary reflectors including circular, flat, few segmented, and parabolic were investigated and compared optically. All the geometric parameters were optimized for each case individually. To calculate the solar flux intensity and uniformity on the absorber tube, a ray-tracing method was implemented using a mathematical code that was developed based on MATLAB software. All the secondary reflectors were simulated in the code, with variable geometrical parameters. A wide range of geometrical parameters were investigated to obtain the most efficient geometry of every secondary reflector design in flux intensity and flux uniformity in comparison with the other cases. The results showed that few flat segmented collectors increase the flux to 87.9%. In addition, the highest uniformity of solar flux was obtained by using the circular and parabolic secondary reflectors. Considering the manufacturing cost as an important parameter, the flat reflector was the favorable one from the flux quantity point of view. Finally, if all the three criteria, i.e., flux quantity, its distribution, and manufacturing cost, were essential to be considered, the flat reflector might be chosen as the most appropriate secondary reflector. [ABSTRACT FROM AUTHOR]

The wake flow in a wind turbine array boundary layer is described using the Koopman operator. Dynamics of the flow are decomposed into the linear and forcing terms, and the low-energy delay coordinates are revealed. The rare events show the non-Gaussian long tails that capture the switching and bursting phenomena. The near-wake region shows the incoherent phase space region, where the dynamics are strongly nonlinear. The far-wake region is marked with the small non-Gaussian forcing term, and the dynamics are largely governed by linear dynamics. The data-driven predictive model is built based on the Hankel-based dynamic mode decomposition and treats the nonlinear state of forcing term as external actuation. The model forecasts the evolution of the flow field for short-term timescales. The mean relative errors between the predictive and test fluctuating velocities are approximately 15%. [ABSTRACT FROM AUTHOR]

A combinatorial technique merging image segmentation via K-means clustering and colormap of the barycentric triangle is used to investigate the Reynolds stress anisotropy tensor. The clustering aids in extracting the identical features from the spatial distribution of the anisotropy colormap images by minimizing the sum of squared error between the cluster center and all data points. The dataset used to investigate the applicability of the clustering technique consists of the flow in a large wind farm for different thermal stratification representatives of a characteristic diurnal cycle. Based on the attribute values defining the colormap of the Reynolds anisotropy stress tensor, the images are converted into color space and then the K-means algorithm assesses the similarities and dissimilarities via a distance metric. In unsupervised learning problems, the K-means algorithm runs independently for different numbers of clusters. The elbow criterion is used to determine the best trade-off between the cluster number and the total variance to select the optimal number of clusters. The clustering technique improves pattern visualization and allows us to identify characteristic regions of the flow based on the structure of the Reynolds stress anisotropy. The dominant patterns reveal that there are major perturbations that control the operation of the wind farm during the diurnal cycle, including the formation and growth of the convective boundary layer and the strong stratification among the flow layers during the stably-stratified period. These parameters attempt to redistribute energy into the velocity deficit region and contribute to the energy balance in the flow domain through the distributions of the momentum flux. As a result of the weak mixing and negligible buoyancy effect, the neutral wind farm displays gradual changes from a prolate turbulence state near the rotor to an oblate turbulence state at the top of the domain. [ABSTRACT FROM AUTHOR]

The flow over a mushroom-shaped microscale coating was experimentally inspected over a diverging channel that followed the pressure side of a wind turbine blade (S835). High-resolution particle image velocimetry was used to obtain in-plane velocity measurements in a refractive-index-matching flume at Reynolds number Reθ ≈ 1200 based on the momentum thickness. The results show that the evolution of the boundary layer thickness, displacement thickness, and shape factor change with the coating, contrary to the expected behavior of an adverse pressure gradient boundary layer over a canonical rough surface. Comparison of the flow with that over a smooth wall revealed that the turbulence production exhibited similar levels in both cases, suggesting that the coating does not behave like a typical rough wall, which increases the Reynolds stresses. Proper orthogonal decomposition was used to decompose the velocity field to investigate the possible structural changes introduced by the wall region. It suggests that large-scale motions in the wall region lead to high-momentum flow over the coated case compared to the smooth counterpart. This unique behavior of this surface coating can be useful in wind-turbine applications, with great potential to increase the power production. [ABSTRACT FROM AUTHOR]

Date palm biomass generates a huge amount of waste throughout the world which can be utilized to produce energy through thermochemical or biochemical conversion technologies. The objective of this study is to present a detailed characterization of parts of date palm branches (twig) and analyse the trace elements including heavy metals for environmental safety and potential slagging and fouling in a reactor. The biomass was divided into four parts: L (leaf ribs), SB (small part of the branch attached to the ribs), MB (middle part of the branch), and LB (large part of the branch attached to the trunk). Different characterization techniques applied were X-ray diffraction, Thermogravimetric analysis, FT-IR, Inductively coupled plasma mass spectrometry, X-Ray Fluorescence, Higher heating values, and ultimate (CHNSO) analysis. High crystallinity was observed in LB with all the heavy metals present in permissible limits. However, it showed a considerably high moisture holding capability. Conversely, SB was found to have low moisture holding capability, moderate higher heating values, and one heavy metal (As) higher than the permissible limit defined by the European Union standards. It can be concluded that LB can be used directly for energy generation after sun drying. The other parts are required to be treated for heavy metal reduction before being used for energy production, keeping in mind the environmental safety. [ABSTRACT FROM AUTHOR]

The availability of consistent and cheap energy is key to a sustainable economy. The challenge of cheap, clean, and sustainable energy supply is faced by all countries. Pakistan is an energy starved country and is trying to overcome its energy woes by installing different types of energy plants under the massive investment of China Pakistan Economic Corridor (CPEC). This paper attempts to determine the suitability of existing power plants installed under the umbrella of CPEC in Pakistan. By considering four different types of power plants, i.e., Coal, Hydro, Solar, and wind, with four essential criteria of Technical, Economic, Life Quality, and Socioeconomic and 11 sub-criterias, the appropriate model has been formulated consisting of goals, criteria, sub-criteria, and alternatives. The analytical network process approach has been applied that uses the principle of multi-criteria decision making to rank and evaluate the four alternatives of electricity generation. The quantitative secondary data were collected from the governmental organizations and international research publications. The results show that hydro power plants are the best source of electricity generation followed by wind, solar, and coal. The proposed decision framework can be used for formulating policies aiming at low cost, clean, and secure energy generation. [ABSTRACT FROM AUTHOR]

Distribution generation (DG) opened a new era for using renewable energy sources to face the future load expansion and enhance the stability of the power system. A methodology for allocating and sizing and analysis for renewable energy sources as DG sources are introduced. Allocation criteria for weaken bus-bars are introduced in this paper. The selected bus-bars are then supported with optimized DG sources in order to enhance the system capability to withstand any future expansion in load. The voltage weakening index is used to compare the voltage of the post-load increase with the base voltage at normal load. A new proposed nested particle swarm optimization (PSO) technique is introduced to design the optimal size of renewable energy source capacity. Two objective functions have been designed for optimal allocation and sizing of the DG; they are the generation and operation energy cost and the transmission line losses (TLLs). The allocation methodology is performed using multi-objective particle swarm optimization. Different scenarios for the optimal operation under different operating conditions are introduced. The new contribution of this paper is the use of the new nested PSO technique for optimal sizing taking the time variation into consideration which has not been revealed before in the literature. The results obtained using the new proposed optimization program show a great potential of deployment of DG renewable energy sources in terms of reducing the cost of energy and TLLs and improving the system operational conditions. [ABSTRACT FROM AUTHOR]

The integration of distribution generation (DG) in distribution networks with improper planning adversely influences the quality of the electrical networks. Conventionally, the outputs from the intermittent DGs, such as solar photovoltaic (PV) plants, are assumed dispatchable. The intermittency of solar irradiance on the outputs of the PV modules has been ignored in most studies on the sizing and placement of DGs. By looking at this problem, this paper presents the sizing and placement of a distributed solar photovoltaic plant (DSPP) by using time series historical weather data. To predict the output from the PV modules, 15 years of solar data were modeled with the aid of a beta probability density function. The total energy loss index was formulated as the main objective function, and the optimization problem was solved by mixed integer optimization by using genetic algorithm. By adopting a time-varying commercial load, the proposed algorithm was applied on IEEE 33 bus and IEEE 69 bus distribution networks. The numerical studies on the two distribution networks show the advantages of the proposed approach for minimizing the total energy losses and improving the bus voltage profiles. It was revealed that up to 38% of the total energy losses in distribution networks could be reduced at sites with solar insolation of 5.65 peaks sun hours. In contrast to existing methods, planning for DGs by using weather data provided more realistic results for DSPP in distribution networks. [ABSTRACT FROM AUTHOR]

This work aims to study, analyze, and compare two direct torque control (DTC) methods of induction machine fed by [3 × 3] direct matrix converter (MC). The first method, DTC, uses the direct model of the matrix converter, whereas the second method, direct torque control indirect (DTCI), uses its indirect model, which describes MC as a combination of a four-quadrant rectifier with a two-level inverter. The two methods are simulated with the same parameters and references of speed and flux. An experimental validation is performed on a prototype of a [3 × 3] direct matrix converter realized in the laboratory, which feeds a three-phase induction machine coupled with a brake. These tests allowed us to demonstrate the practical feasibility of these control schemes. The algorithms are implemented on a dSPACE 1104 controller board. The input power factor is fixed to 1. A comparison between the two algorithms results based on several criteria (power quality, static and dynamic performance of the system, and maintenance of the unity power factor) is presented, and the results are discussed. [ABSTRACT FROM AUTHOR]

The rate of integration of distributed generation (DG) using renewable sources is increasing in distribution networks because of their technical and economic advantages. However, mismatches in the timing of electricity demand and generation in distribution networks have restricted the penetration of non-dispatchable DGs such as photovoltaic (PV) plants. Such a problem associated with the integration of DGs in distribution networks could be eliminated using the proper application of battery energy storage systems. In this paper, optimal planning of battery-coupled distributed photovoltaic generators (BCDPGs) in distribution networks is presented. The optimal planning determines the size and location of BCDPGs and schedules the charging and discharging of the batteries, while minimizing the total energy losses subject to technical constraints. To estimate the output from PV modules, 15-year solar irradiance data is modeled using the beta probability density function. Mixed-integer optimization using a genetic algorithm is employed for solving the optimization problem. The numerical studies on a 33-node distribution network show the advantages of the proposed methodology. The results obtained through this study show the capability of the proposed method to optimally allocate BCDPGs to largely improve the quality of supply of power from non-dispatchable DGs in terms of reducing energy losses, improving bus voltages and increasing penetration levels of renewable energy. The proposed approach can also be useful when applied to realistic networks for proper sizing and operations of battery-coupled photovoltaic plants. [ABSTRACT FROM AUTHOR]

Three-phase controlled/uncontrolled converters have been used in renewable energy applications such as photovoltaic and wind energy as rectifiers and inverters. The main drawback of these converters is the high THD (Total Harmonic Distortion) in their line currents. Many techniques have been used to remedy this problem. Third harmonic current injection is one of the best solutions for the harmonic reduction in line currents of these converters. Injecting third harmonic current from the dc-bus to the line currents reduces its harmonic contents. Minimum THD for any firing angle of the controlled converter is a function of the phase-angle and amplitude of harmonic injection current that can be controlled by a single-phase controlled converter and a boost converter, respectively. This scheme is used with a zigzag transformer to circulate the harmonic injection current to the line currents. A novel mathematical analysis for the proposed scheme and state of the art scheme is introduced. The mathematical analysis introduces the optimum values for components on the harmonic injection path at minimum THD and the corresponding efficiency. The scheme under study has been simulated using the PSIM program. A lab prototype for this scheme has been implemented. Mathematical, simulation, and experimental results for this scheme have been introduced, compared, and discussed. The results show the superiority of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents an assessment of three types of battery in a designed battery controller for a battery energy storage system (BESS) integrated with a solar photovoltaic system for load leveling and peak shaving applications. Three types of battery--lead acid, lithium ion, and nickel metal hydride--are discussed in detail and assessed in this work, focusing on small-scale integration. The controller was designed using Matlab Simulink to monitor consumer load demand, control the charging and discharging process of the BESS, and regulate while fulfilling the load demand, in addition to prolonging the BESS lifetime. From the simulation results, the nickel metal hydride battery is the best option for development of a battery controller. It achieved an average 37.45% leveled load profile and a 35.75% reduction of the load peak. However, the lead acid battery is still the dominant choice among consumers, in spite of average performance, because it has the best cost performance. [ABSTRACT FROM AUTHOR]

This paper aims to provide a novel framework for optimal congestion management via encouraging a collaboration between the independent system operator (ISO) and Retail electricity companies (Recos) in implementing demand response (DR) programs based on the market mechanism. The merit of this paper is to increase the market efficiency. Three economic signals, namely, demand reduction, congestion elasticity and electricity spot price values, specified by the ISO, are used for assisting Recos in evaluating any benefits from implementing DR in various network buses. A Stackelberg game is adopted for designing a DR trade between Recos and demand response aggregators to help Recos identifying their optimal demands in the market, which are then used by the ISO to analyze grid congestion and consequently to re-specify the new economic signals. The game is repeated until the Nash equilibrium point, the optimal congestion reduction and the optimal Recos' demands are obtained. The performance of the proposed framework is assessed using a test power system and the results are compared with the current practices in the Australian electricity market. This paper demonstrates an effective performance of the proposed framework. [ABSTRACT FROM AUTHOR]

This paper proposes a maximum power point tracking (MPPT) technique based on the tip speed ratio control for small scale wind turbines (WTs). In this paper, artificial neural network based particle swarm optimization has been trained offline to learn the characteristic of the turbine power as a function of wind and machine speeds. Afterwards, it has been realized online to estimate the varying wind speed. It is essential to design a controller that can track the maximum peak of energy regardless of wind speed changes. Therefore, this work provides a novel robust direct adaptive fuzzy-Proportional-Integral (PI) controller during the MPPT process through tuning duty cycle of the boost converter for permanent magnet synchronous generator driven by a WT. The proposed method has successfully decreased the ripples of coefficient of power (Cp) which is the index of MPPT mode, under variations of the wind speed in comparison with conventional controller. Finally, a systematic analysis is presented which is in good agreement with simulation results, confirming the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

Hot-wire anemometry measurements have been performed in a 3×3 wind turbine array to study the multifractality of the turbulent kinetic energy dissipation. A multifractal spectrum and Hurst exponents are determined at nine locations downstream of the hub height, bottom and top tips. Higher multifractality is found at 0.5D and 1D downstream of the bottom tip and hub height. The second order of the Hurst exponent and combination factor shows the ability to predict the flow state in terms of its development. Snapshot proper orthogonal decomposition (POD) is used to identify the coherent and incoherent structures and to reconstruct the stochastic velocity signal using a specific number of the POD eigenfunctions. The accumulation of the turbulence kinetic energy in the top tip location exhibits fast convergence compared with the bottom tip and hub height. The dissipation of the large and small scales is determined using the reconstructed stochastic velocities. The higher multifractality is shown in the dissipation of the large scale compared with small scale dissipation showing consistency with the behavior of the original signals. Multifractality of turbulent kinetic energy dissipation in the wind farm is examined and the effect of the reconstructed flow field via proper orthogonal decomposition on the multifractality behavior is investigated. Findings are relevant in wind energy as multifractal parameters identify the variation between the near- and far-wake regions. [ABSTRACT FROM AUTHOR]

The aim of this study was to use the CALPUFF modeling system, an effective and reliable atmospheric modeling tool, to predict the concentrations of formaldehyde (HCHO) and nitrogen oxides (NOx) released, due to the combustion of biogas in the combined heat and power (CHP) engines, from the Kawartha renewable energy generation facility at its proposed location in Ontario, Canada. In this study, HCHO and NOx were selected as the indicator and point source pollutants since they were the most significant products of biogas combustion emitted during the facility's normal operations (production of electricity and heat). The Lambert Conformal Conic projection coordinate system was implemented for the operation of the CALPUFF model. The proposed modeling scheme was coupled with both surface meteorological data (from 00:00 to 23:00) on an hourly basis and 12-h intervalbased upper air meteorological data (from 00:00 to 12:00) to simulate the emission of these pollutants for the four seasonal Eastern Time meteorological conditions of winter (January 11-13, 2013), spring (April 14-16, 2013), summer (July 10-12, 2013), and autumn (November 16-18, 2013). The results from the CALPUFF dispersion model clearly demonstrated that the maximum 1-h average concentrations of both HCHO and NOx, emitted from the combustion of biogas (composed of 60% CH4 and 40% CO2) in five CHP engines (operation load = 100%, maximum electricity generation capacity = 9.8 MW), were found to be within the limits defined by Ontario Regulation 419/05. [ABSTRACT FROM AUTHOR]

The demand for electrical energy increased drastically due to the exponential growth of the world population. In the last decade, owing to environmental issues and decay of non-renewable energy resources, the development of power generation from hydrokinetic energy has grown considerably. Many individuals and companies are considering hydrokinetic power as the better solution to the prevailing energy crisis. However, there is a paucity of published literature that sheds light on the economic and environmental sides of hydrokinetic turbines (HKTs) in hybrid renewable energy systems (HRES). The prime objective of this study is to provide an economic and environmental assessment of using the HKT in combination with other renewable energy resources for cost-effective, reliable, and sustainable electrical energy supply for the rural households in Naga Hammadi, Egypt, where adequate water resources are available from the Nile River. The HKT is simulated together with photovoltaic (PV), diesel generator (DG), and battery (B) power using the well-known Hybrid Optimization of Multiple Electric Renewables software to optimize the HRES. The net present cost (NPC) of the optimum HRES is $12.7 million with minimal cost of energy of $0.158/kWh. The optimum system is capable of saving approximately $9.7 million during the project lifetime (25 years) in the form of NPC as compared to the diesel generator system. In addition, the system is capable of saving 28.971×106 l of fuel at the cost of $5.11 million during the project lifetime. Finally, it is concluded that the hybrid PV/HKT/DG/B is the more economic and environment friendly system as compared to other system configurations especially the diesel generator system, because it is able to reduce 76.29×106 kg of the amount of CO2 emissions during the project lifetime. [ABSTRACT FROM AUTHOR]

The configuration of hybrid energy systems has a great influence on the cost of generated energy from the system. This paper introduces a design, simulation, assessment, and selection of optimum autonomous hybrid renewable energy configuration out of three different configurations. The proposed hybrid system contains photovoltaic (PV), wind, diesel, and battery energy systems. A new computer program has been designed to simulate different configurations of hybrid energy systems. A genetics optimization smart technique using a genetic algorithm has been used to calculate the optimum sizing for each component at different configurations of the hybrid system for minimum cost and highest reliability. The optimum penetration ratio of renewable energy systems (PV and wind) will be selected according to the lowest price. Actual data for one remote site in Saudi Arabia has been used in the input data of this computer program. Sensitivity analysis has been carried out to show the conditions for selecting any configuration under study. The results obtained from this study can help researchers, designers, and decision makers to answer many open questions regarding the design and installations of hybrid renewable energy systems. [ABSTRACT FROM AUTHOR]

This paper presents a model-based algorithm for fast tracking of maximum power point of a photovoltaic panel. Parameters of an equivalent circuit have been estimated based on experimental data and characteristic data provided by manufacturer. Since photoelectric current is highly temperature-dependent, the effect of temperature is considered in the model. The proposed method is based on the maximum power point locus of the solar panel. So the tracking speed is much faster than a model-free method. In the suggested technique, the voltage of maximum power point can be determined using output voltage and current of solar panel and the voltage of a point on the maximum power point locus with the same current, in three steps. The main novelty of the proposed model-based method is that there is no need to measure solar radiation. Experiment results are presented and prove the feasibility of the proposed maximum power point tracking method. [ABSTRACT FROM AUTHOR]

In this paper, a double-glazed solar air heater (SAH) using paraffin wax as phase change material (PCM) was designed, fabricated, and tested under the climatic condition of Mashhad, Iran (latitude, 37° 280 N and longitude, 57° 200 E) during three typical days in the summer. The PCM stores solar radiation of the sun as latent and sensible heat during daytime and then restores such stored energy during the night. Exploitation of both first and second laws of Thermodynamics, the energy and exergy efficiencies of this system are assessed. According to the experiments undertaken, it is found that the daily energy efficiency of the system varies between 58.33% and 68.77%, whereas the daily exergy efficiency varies from 14.45% to 26.34%. Eventually, the economic analysis shows that the cost of 1 kg of heated air utilizing double-glazed SAH would be 0.0036$. [ABSTRACT FROM AUTHOR]

Hot-wire measurements obtained in a 3×3 wind turbine array boundary layer are utilized to analyze high order structure functions, intermittency effects as well as the probability density functions of velocity increments at different scales within the energy cascade. The intermittency exponent is found to be greater in the far-wake region in comparison with the near-wake. At hub height, the intermittency exponent is found to be null. Extended self-similarity scaling exponents of the second, fourth, and fifth order structure functions remain relatively constant as a function of height in the far-wake; whereas in the near-wake, these are highly affected by the passage of the rotor where tip vortices reside, thus showing a dependence on physical location. When comparing with proposed models, these generally overpredict the structure functions in the far-wake region. The probability density function distributions in the far-wake region display wider tails compared to the near-wake region, and the constant skewness hypothesis based on the local isotropy is disrupted in the wake. [ABSTRACT FROM AUTHOR]

This paper introduces a new proposed design and optimization simulation program for the techno-economic sizing of a stand-alone hybrid photovoltaic/wind/diesel/ battery energy system using the iterative optimization. The main function of the new proposed simulation program is to determine the optimum size of each component of a hybrid renewable energy system for the lowest price of generated energy and the lowest value of dummy energy at highest reliability. An accurate methodology for pairing between five Saudi Arabia sites and ten wind turbines from different manufacturers to maximize energy production and minimize the price of the generated power is introduced. This methodology changes the penetration ratio of the renewable energy sources in certain increments to meet the load requirements of the sites under study. A detailed economic methodology to obtain the price of the generated energy is introduced. The new proposed simulation program is implemented in flexible fashion, which is not possible for the market-available software, such as HOMER, INSEL, TRNSYS, and RETScreen. The results obtained from the new proposed simulation program are compared with those from genetic algorithm and HOMER software to evaluate the effectiveness of the proposed program. Many valuable results can be extracted from the proposed program to assist researchers and decision makers. [ABSTRACT FROM AUTHOR]

Partial shading on photovoltaic (PV) modules reduces the generated power of the PV system than the maximum power generated from each module separately. The shaded PV module acts as a load to unshaded ones which can lead to hot-spot. To alleviate the effect of partial shading, bypass diodes should be connected across each PV modules. Connecting several PV modules together produces multiple peaks (one global peak (GP) and multiple local peaks (LPs)) on partial shading conditions. Maximum power point tracker conventional techniques are designed to follow the GP but they stuck around LPs such as fuzzy logic controller (FLC). In this paper, modified particle swarm optimization (MPSO) using genetic algorism has been used to follow the GP under any operating conditions. MPSO has been studied and compared with the FLC technique to show the superiority of this technique under all operating conditions. Co-simulation between Matlab/Simulink and PSIM has been used to model the PV system under partial shading conditions. The simulation results show that the MPSO technique is more effective than FLC in following the GP. The generated power increases considerably with the MPSO than the FLC technique in shading conditions. [ABSTRACT FROM AUTHOR]

A novel method for computing sky view factor for isotropic diffuse radiations on tilted collectors located in obstacle free and urban sites has been introduced in this paper. The proposed method involves disintegrating the hemispherical sky vault around collector into small portions (sky elements). Collector is a flat receiving surface, positioned at a particular tilt angle and facing a specific azimuthal orientation. The three-dimensional celestial vault is transformed into a twodimensional plane. This plane is converted into a computer graphic raster image for computing. Each pixel of raster image represents a sky element. Color (gray shade) of every pixel describes specific weight which depends upon sky element's solid angle and incidence angle with respect to collector. Sky view factor is evaluated by taking ratio of the sum of color codes of all the pixels for tilted collector to that of horizontal collector. Sky view factors at different tilt angles for obstacle free sites are evaluated and results are found in good agreement with Liu Jordan method. To evaluate sky view factor for urban sites having obstacles (e.g., buildings, trees, etc.) that may cause sky blocking, the obstacles are taken into account by projecting them onto the celestial vault. Their projections are transformed onto a two dimensional plane and then onto the raster image. For enhancing the applicability of the proposed method, so as to analyze sites with complex sky blocking obstacles, the approach is developed such that it can be computer programmed easily. Small portions of sky can be located and analyzed in a program using a specially developed coordinate system recognized by various programing languages. The program results in grey scaled raster images presenting radiances received by the collector, coming from different portions of the sky. Comparison of sky view factors obtained from the proposed method with existing methods published in literature is also presented. Results show that the proposed methodology is in good agreement with Liu Jordan method and provides more logical results as compared to results published in literature for urban sites with obstacles. The deviations between results are quantified and discussed. [ABSTRACT FROM AUTHOR]

An aerodynamic shape optimization method for a horizontal axis wind turbine is developed and verified through experimentation with a laboratory-scale wind turbine. Our method is based on matching the rotor's and the coupled generator's torque. Prior to shape optimization, an initial rotor design is established with a hybrid use of Schmitz and blade element momentum theories. The experimental verification of the developed method is conducted with a small-scale wind turbine; thus, the operating Reynolds number is one order of magnitude lower than large-scale wind turbines. Therefore, a high-lift low-Re airfoil, namely, SG6043, is selected for the blade along the whole span. The shape is optimized by determining the optimum chord and cumulative pitch angle distributions by manipulating the tapering and twisting of the blade. The objective of the optimization is to maximize the turbine's power coefficient Cp, while maintaining the torque equal to that of the generator. The generator's characteristics are found through experimentations which are conducted apart from the wind tunnel experiments. During the optimization process, the local aerodynamic forces on the blade are calculated by interfacing the optimization program with XFOIL; thus, the torque and power can be calculated for the rotor at each iteration step. The optimized turbine performance is evaluated under a design and off-design operating condition. The performance verification experiments are carried out in the wind tunnel with a specially designed setup. A comparison of the measured and computed performance shows good agreement. [ABSTRACT FROM AUTHOR]

This paper presents an improved Fractional Short Circuit Current (FSCC) Maximum Power Point Tracking (MPPT) technique in which an additional control loop is used to find the proper moment to measure the SCC. The target is to reduce the power losses in MPPT process that occur as a result of intermittent time based short circuit current measurements. The proposed modification enables the conventional FSCC MPPT to decide intelligently about the measurement of SCC thus reduces the number of times the photovoltaic (PV) module is isolated from the load. Although number of algorithms for tracking MPPT has been reported, the proposed method suits well for low cost PV applications. A Matlab/Simulink based model is employed to test the functional abilities of the proposed method. The comparison of the proposed method and conventional time based FSCC method is also presented in the simulation analysis. Finally, a 130W prototype based on the dSPACE DS1104 controller and experimental results are presented to verify the effectiveness of the proposed method. The technique is verified under uniform shading conditions. The results show satisfactory performance against test conditions. [ABSTRACT FROM AUTHOR]

This paper presents a novel control method for Maximum Power Point Tracking of wind turbines (WTs) equipped with a Permanent Magnet Synchronous Generator (PMSG) and a Direct Matrix Converter (DMC). The method calculates the optimum wind turbine speed and maximizes the extracted power from wind turbine. This is done by Hill Climb Search method, which is simple and does not need to know the generator parameters and no need to solve the complicated differential equations of generator. WT rotor speed is compared with its optimal value and then DMC controls WT until its rotor speed reaches its optimum value. Under this situation, maximum power is extracted from WT and is injected to the grid with unity power factor. It is implemented by controlling the phase and the amplitude of the DMC output voltage by Venturini switching method. Simulations are done on a 2MW PMSG WT in MATLAB/SIMULINK to obtain the results, the wind speed was varied both using the Van Der Hoven method and changing the wind step. The obtained results verify the accuracy and simplicity of proposed method. [ABSTRACT FROM AUTHOR]

A nonlinear computational model, based on solving the Navier-Stokes equation, is used to study the motion of a 5MW spar buoy floating wind turbine in moderate and extreme sea states with irregular waves. The main advantages of using the current model are that there is no limitation on the platform motion, the hydrodynamic loads do not rely on experimental data, and nonlinear hydrodynamic loads can be predicted. The current work extends a previously developed Navier-Stokes model for regular periodic waves on a tension leg platform floating wind turbine. Free decay tests are performed, and pitch, heave, and surge natural frequencies are determined. The responses of the spar buoy to operating conditions with significant wave height of 8m and mean period of 10 s, and an extreme sea states including waves over 17m height are studied. For the extreme sea state, a nonlinear model is required, since the platform response amplitudes are not small with respect to the spar buoy diameter. Effects not included in linear models, such as platform pitch angles higher than 10, complete submergence of the platform tank and tether slacking are captured. Finally, a design study on spar buoy aspect ratio is performed for one sea state and it is shown that higher aspect ratio spars generally lead to lower mean pitch and surge responses as expected, but also may lead to a nonlinear trend in the standard deviations in pitch and heave, probably due to the increase in wind and wave moments on the spar. [ABSTRACT FROM AUTHOR]

The issue of searching alternatives for diesel fuel in transport sector that is one of the largest diesel fuel consuming sectors in each country has become more attractive nowadays. In this study, the energy consumption and CO2 emissions of biodiesel production from rapeseed as an alternative for diesel fuel in transport sector was assessed in terms of three main stages including agricultural crop production, transport, and industrial conversion. The results revealed that the total fossil energy input cost was calculated as 28 122.16 MJ ha-1 and the renewable energy output content (biodiesel as the final outcome) was estimated as 31 802.06 MJ ha-1. The net energy returns and the fossil energy ratio were calculated as 3679.9 MJ ha-1 and 1.13, respectively. It shows rapeseed could be a suitable energy crop for biodiesel production. CO2 emissions assessment showed that the total greenhouse gas emissions over biodiesel production life cycle were 1054.98 kg CO2 eq ha-1 and the agricultural crop production stage ranks the first. In order to establish energy crops cultivation such as rapeseed and achieve the sustainable development, meteorological and water source availability data collected and analyzed for all the 31 provinces in Iran to generate a map of regions capable of rapeseed cultivation. The results revealed that 24 provinces among 31 provinces have a great potential for rapeseed cultivation. [ABSTRACT FROM AUTHOR]

A comprehensive Quality Assurance (QA) process was implemented on the meteorological measurements and power output of the neighboring wind turbine at the Wind Energy Institute of Canada's wind farm on Prince Edward Island. The data, obtained from May 2013 to September 2021, include wind power, speed, direction, temperature, pressure, and relative humidity, averaged over 10 min. The first QA step was the detection of erroneous values due to well-known causes, such as the icing of the cup anemometers, the wake of the neighboring turbine, and the meteorological mast. Subsequent, and mainly novel, procedures were developed to capture systematic errors, nonphysical values, and repeated constant values, to assess the internal consistency, and to deal with abnormally high variation and erroneous small values in the data. Most of the data taken before the calibration of the anemometers in 2017 and some a few months after the calibration were invalid; a fact that shows the importance of yearly calibration. The installation of two instruments on the opposite sides of the mast provided "counterpart" measurements, which greatly facilitated the QA. We also offer some recommendations about the layout of the mast and closest wind turbine and the value of using sonic anemometers which are not affected by icing. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvesting technologies have received a great attention during the last decade to design self-powered microelectronic devices such as wireless sensor nodes. Piezoelectric energy harvester is a resonant system that produces maximum power output when its resonant frequency matches the ambient vibration frequency. The deviation from the resonance causes significant decrease in the power output. There are two possible solutions to compensate the effect of frequency deviation: widening the operating frequency bandwidth and tuning the resonant frequency. Tuning the resonant frequency is a more efficient technique for applications with single time varying dominant frequency. This paper presents a comprehensive review of frequency tuning methods for piezoelectric energy harvesting systems. Two categories generally investigated in the literature include manual and autonomous tuning methods. The recent developments of many tuning strategies are discussed and summarized. [ABSTRACT FROM AUTHOR]

Potable water supply/return pipe freeze problem of domestic passive solar water heaters in chilly spells is a major concern which limits the reliability of this renewable energy in building applications. Thus, a thermosiphon heat pump-piping system was introduced that pumps indoor room air heat to the outdoor section for pipe freeze protection. In the outdoor section, the hot pipe (return) has been embedded in supply (cold) tube, while the indoor section mainly consists of a metal heat absorber pipe as supplier. Room air heat is transferred from indoor to outdoor section via a naturally driven water loop due to buoyant pressure. A prototype has been fabricated and tested in a freezer with the base temperature of -22 ± 2 °C (as the outdoors ambient), while the indoor section had been placed in a separate chamber with adjustable ambient temperature in the range of 15-40 °C (simulating the indoors air). Performance tests have been conducted in draw-off, for different chamber temperatures, heat absorber tube lengths, and filled/empty water storage tank conditions. In the filled tank experiment, threshold pipe freezing was observed where chamber temperature was as low as 15.5 °C compatible with residential condition. Moreover, the heat pumping rate decreases linearly with room (chamber) temperature and approach to 10 W at pipe freeze threshold. Thermosiphon, low room air temperature performance, slight parasitic energy loss (0.25-0.45 kWh/day), low price, and its simplicity are the promising aspects of this heat pump for prevention of pipe freeze for domestic passive solar water heaters and sustainable development of solar energy in residential buildings. [ABSTRACT FROM AUTHOR]

This paper aims at determining the optimum tilt angle for south facing flat-plate solar collectors in Iran. Solar radiation on a horizontal surface was estimated by applying an empirical method and employing meteorological data from 80 selected cities. A mathematical model was used for estimating the solar radiation at different tilt angles. Daily, monthly, seasonally, bi-annually, and yearly optimum tilt angles and solar radiations were determined for 80 selected cities. Recommendations were made on the optimum tilt angle adjustment for different places in the country in order to benefit the best solar radiation available. The averaged benefits of annual solar radiation for 80 cities were 21.3% for daily, 21% for monthly, 19.6% for seasonal, 19.3% for bi-annual, and 13.3% for yearly adjustments compared with the radiation on the horizontal collector. Based on these results, adjusting tilt angles, at least twice a year, is recommended. Optimum tilt angles for cloudy sky cities with a low clearness index are lower than those for cities at the same latitude angle having a higher clearness index. In addition to latitude angle, the climate conditions are also important for determining the optimum tilt angle. [ABSTRACT FROM AUTHOR]

Today's society relies heavily on electric power produced mainly using coal and petroleum. These sources of energy are nonrenewable. The rise in the cost of petroleum and the effects of coal on the environment force the issue of seeking alternative sources of energy that are renewable and environmentally friendly. One such source is solar energy. Solar energy is extracted via photovoltaic (PV) modules. The problem with this alternative form of energy is the poor efficiency of solar cells. This work deals with the development of an improved dynamical model of PV modules to maximize the amount of power extracted from the Sun. The developed model has been implemented using MATLAB®/SIMULINK. Field data are used to compare the efficiency of the newly developed model to the existing models reported in the available literature. Results reveal that the proposed model led to an improvement of 21% in the efficiency of the PV module. Such improvement in efficiency will lead to great energy saving when used on a large number of PV modules. [ABSTRACT FROM AUTHOR]

There has been an increase in recognition of the important role that the boundary layer turbulent flow structure has on wake recovery and concomitant wind farm efficiency. Most research thus far has focused on onshore wind farms, in which the ground surface is static. With the expected growth of offshore wind farms, there is increased interest in turbulent flow structures above wavy, moving surfaces and their effects on offshore wind farms. In this study, experiments are performed to analyze the turbulent structure above the waves in the wake of a fixed-bottom model wind farm, with special emphasis on the conditional averaged Reynolds stresses, using a quadrant analysis. Phase-averaged profiles show a correlation between the Reynolds shear stresses and the curvature of the waves. Using a quadrant analysis, Reynolds stress dependence on the wave phase is observed in the phase-dependent vertical position of the turbulence events. This trend is primarily seen in quadrants 1 and 3 (correlated outward and inward interactions). Quantification of the correlation between the Reynolds shear stress events and the surface waves provides insight into the turbulent flow mechanisms that influence wake recovery throughout the wake region and should be taken into consideration in wind turbine operation and placement. [ABSTRACT FROM AUTHOR]

In the interest of understanding the dynamics and energy transfer between the atmospheric boundary layer and large wind turbine arrays, a description of the turbulence anisotropy in the wake region of wind turbines is necessary. Flux of high momentum flow into the wind turbine array by anisotropic turbulence is a dominant factor of mean kinetic energy resupply for the wind farm. Under thermal stratification, the behavior of the turbulence field, and the energy flux, is significantly altered. Here, a thermally stratified wind turbine array boundary layer is studied in detail using a combination of Lumley and barycentric maps together with the recently introduced spheroid and color maps. The atmospheric flow is modelled using a large eddy simulation driven by a constant geostrophic wind and a time-varying ground surface temperature, obtained from a selected period of the Cooperative Atmosphere-Surface Exchange Study-99 field experiment. The wind farm is modelled using the traditional actuator-disk with rotation and yaw-alignment. The results show that turbulence under unstable stratification tends to be more isotropic than that under neutral and stable stratification. The turbulent mixing attributed to positive buoyancy in unstable regimes determines the energy distribution between flow layers, directly affecting the vertical distribution of anisotropy. Contrarily, in the stably stratified flow, negative buoyancy damps the turbulent fluctuations, hence affecting the evolution of the Reynolds stress, leading to an increase of flow anisotropy. In both thermal stratification regimes, wind turbines alter the structure of the turbulence within the atmospheric boundary layer by creating regions of greater anisotropy and expanding the boundary layer vertically. For the modeling community, it is important to note that the wind turbine wakes display a larger degree of anisotropy that is related well to the production of turbulent kinetic energy and mean kinetic energy entrainment, and hence, it is important to model correctly for accurate power forecasting. Leveraging the new insights into wind turbine/atmospheric boundary layer interaction found here will benefit the formulation of a new generation of efficient low order models for commercial application. [ABSTRACT FROM AUTHOR]

The uncertainty associated with renewable energy sources, particularly wind, makes them an unpredictable means of power generation. To guarantee continuous and reliable power supply, wind speed variability modeling is considered a vital step for meeting the planning and operational challenges of an electric power grid. In this paper, a novel probabilistic generation model is developed to estimate and generate time-coupled wind speed patterns. A 1 h time step is considered to construct the time-coupled probabilistic wind speed patterns based on a two-parameter Weibull distribution. These parameters of the Weibull distribution are found by considering the variations of reference wind speed patterns at two successive time steps. The probabilistic model is then used to create a number of aggregate wind speed generation scenarios. The validity of our proposed approach is evaluated with the help of goodness-of-fit test indicators such as average mean absolute percentage error and the Kolmogorov–Smirnov test error. The results of goodness of fit tests and comparison of output power determined through the proposed model with the existing model in the literature suggest that the proposed model is appropriate for wind speed uncertainty modeling and can be applied in power system planning studies. [ABSTRACT FROM AUTHOR]

Skirted foundations denoted as suction caissons are becoming an increasingly prevalent offshore foundation solution for either the oil and gas industry or renewable energy infrastructure. Their response to combined vertical, horizontal, and moment loading must be found to ensure their stability under harsh environmental conditions. As part of this process, knowledge of uniaxial capacities is required. Previous studies have neglected the effect of deformable ground by assuming that the soil within skirts behaves rigid during drained loading, but this assumption needs rigorous studies. A series of 3-D finite element analyses has been conducted to investigate directly how the skirt geometry, soil–skirt interface roughness, and deformable plug within the skirt compartment affect the drained skirted foundation capacity and depth factors under uniaxial loading. The results show that the foundation embedment, interface friction, and soil plug placed within the skirt significantly influence the accompanying mechanisms occurring at failure and therefore the uniaxial capacities. The finite element analyses under uniaxial loads are performed for the rough and smooth interface assumptions, to show how the roughness interface influences the ultimate bearing capacities and depth factors and the corresponding failure mechanisms in different soil profiles. [ABSTRACT FROM AUTHOR]

Today, energy consumption and demand together with global warming are one of the most important challenges of human life. From the environmental point of view, the Heating Ventilation and Air Conditioning industry and current refrigerants are one of the important factors of global warming which need to be resolved. In terms of energy consumption, the main way is the development and use of renewable energy technologies which not only increases the efficiency of these systems but also generates diversification in energy resources. Among the various renewable energy systems, geothermal heat pumps offer significant potential to reduce energy consumption and also carbon dioxide emissions. The main purpose of this research is to select environmentally friendly refrigerants with the best performances. To assess the thermodynamic performance of organic refrigerants in geothermal heat pumps, this system is modeled using Engineering Equation Solver software. In this research, the results are compared with the results of the thermodynamic behavior of conventional refrigerants R22 and R134a for geothermal heat pumps with horizontal and vertical closed loop ground heat exchangers and also open-loop systems. Finally, R152a, R600, and R717 were introduced as substitute refrigerants to replace with synthetic refrigerants in the above-mentioned geothermal heat pump systems, resulted in an increase in 2.97–5.8 percent coefficient of performance in the cooling mode which means reducing the operating cost of the system compared to conventional artificial refrigerants. [ABSTRACT FROM AUTHOR]

A constant load and generation model is generally considered in planning studies that pertain to Distributed Generation (DG) integrated distribution systems. However, such considerations may result in misleading and inconsistent values for the voltage profile, loss reduction, payback period, deferral values, and other related calculations due to the variation of both renewable energy-based generation and load demand. This paper investigates the impact of time varying voltage dependent load models on the DG planning studies. The study is based on the comparative assessment of different impact indices, penetration level, active and reactive power intake, active and reactive power loss, and Mega Volt Ampere support offered by the installation of photovoltaic based DG for different time varying load models. The outcomes of the current research work reveal that the time varying load modeling approach has significant impact on the distribution systems. [ABSTRACT FROM AUTHOR]