Discrete Wind Speed Research Articles

Particle swarm optimization for the optimal layout of wind turbines inside a wind farm

The wind turbine’s output power is heavily affected by the arrangement of the wind turbine location. Wind farm planning endeavors to firstly maximize the farm’s output energy. Secondly, it seeks to minimize the effects of the wake phenomenon. This paper attempts to find the best possible location of a wind turbine inside a square farm using the particle swarm optimization (PSO) method whilst focusing on the three salient cases: the steadiness of wind direction and speed, the variability of the flow direction with a steady speed, and the variability of direction for three discrete wind speeds. The proposed algorithm generated results that will be contrasted to previous studies on the same topic with different metaheuristic methods such as a genetic algorithm. When compared to the optimum findings from prior research, the suggested approach has a reduced cost. It is developed by language C through MATLAB environment considering a square with the dimensions 2×2 kilometers.

Measurement and large-eddy simulation of single-sided natural ventilation in urban building groups

Natural ventilation is a highly respected and effective way to improve indoor air quality, and single-sided natural ventilation is easily formed in residential buildings. The site experiments were carried out, and the unsteady characteristics of the airflow were analyzed based on 3D wind speed series. With the experimental verification, large-eddy simulation was successfully applied to calculate the indoor–outdoor flow field of urban building groups. When the entrance boundary was constant, the flow field of the window varied all the time, and outflow was irregular. The natural ventilation efficiency was 42% with the incoming flow almost parallel to the window. The discrete wind speed inlet boundary is more suitable for the natural ventilation simulation of buildings in a real environment than the average wind speed boundary and the average wind speed superposition ±10% disturbance.

Matérn process-based simulation of wind speed time series

This work proposes a practical methodological framework for simulating long-term discrete wind speed time series, for applications to renewable energy systems. The framework is based on the Matérn stochastic process, that is used to identify and extract the short and long-term periodic components present in the mean and variance of a wind speed time series, and to characterize the residual random component. The procedure of construction of synthetic wind speed time series is developed, rooted in a fast numerical simulation algorithm for the Matérn process. We empirically validate the usefulness of the proposed framework by numerical experiments based on three real historical wind speed datasets. The results show consistent statistical similarities between the historical and simulated wind speed time series of data.

FLOW Estimation and Rose Superposition (FLOWERS): an integral approach to engineering wake models

Abstract. Annual energy production (AEP) is often the objective function in wind plant layout optimization studies. The conventional method to compute AEP for a wind farm is to first evaluate power production for each discrete wind direction and speed using either computational fluid dynamics simulations or engineering wake models. The AEP is then calculated by weighted-averaging (based on the wind rose at the wind farm site) the power produced across all wind directions and speeds. We propose a novel formulation for time-averaged wake velocity that incorporates an analytical integral of a wake deficit model across every wind direction. This approach computes the average flow field more efficiently, and layout optimization is an obvious application to exploit this benefit. The clear advantage of this new approach is that the layout optimization produces solutions with comparable AEP performance yet is completed 2 orders of magnitude faster. The analytical integral and the use of a Fourier expansion to express the wind speed and wind direction frequency create a relatively smooth solution space for the gradient-based optimizer to excel in comparison to the existing weighted-averaging power calculation.

Increase a real wind farm productivity through optimizing wind turbines layout

In this paper, a 3D wake model considering both axial and radial wind speed variations along the incoming wind direction, and the non-flat topography effect on the wind flow, is developed for the layout optimization of a real onshore wind farm. The effectiveness of two methods (i.e., the discretization method that divides the wind scenario into small intervals and the Monte Carlo method which randomly generates the discrete wind speed samples), for evaluating the overall wind farm power production under the wind speed variation of Weibull distribution is investigated for the comparative study. It is found that the Monte Carlo power evaluation method achieves a better outcome than the traditional discretization method, with more total power output and less computational cost. Through the layout optimization with a total of 15 wind turbines installed, the individual wind turbine yields more than 533 kW power out of 536 kW theoretical wake-free power. As the installed wind turbine number increases, the maximum discrepancy of the actual wind turbine power output with respect to the theoretical power increases from 3 kW (with 15 wind turbines) to 6 kW (with 20 wind turbines). Through the comparative study of different wind rotation scenarios, it is found that the maximum discrepancy of individual actual wind turbine power outputs is 8 kW and 13 kW for a rotational angle of [Formula: see text] and [Formula: see text], respectively. Under the scenario of [Formula: see text] wind rotation scenario, the maximum individual power output deficit with 20 installed wind turbines is around 20 kW and the discrepancy of the total power output by comparing to the baseline wind model is maximally 1% proving the robustness of the optimization results with respect to the wind scenario variation.

Optimization of tow-steered composite wind turbine blades for static aeroelastic performance

The concept of passive aeroelastic tailoring is explored to maximize power extraction from an NREL 5-MW wind turbine blade rotating in a uniform flow, where a single blade with periodic boundary conditions simulates a three-bladed wind turbine rotor. Variable-angle tow composite materials model the spanwise-variable wind turbine blade design and enable coupled bend-twist deformations under aerodynamic loading. A constrained optimization algorithm varies only the composite fiber angles along the blade span to determine their optimal distribution at four uniform inflow conditions ranging from cut-in to rated wind speeds. The computational fluid dynamics solver CRUNCH CFD ® and commercial finite element analysis solver Abaqus compute the static aerodynamic loads and structural deformations of the blade, respectively, until aeroelastic convergence is achieved. The resulting computational aeroelastic formulation predicts an increase in turbine power extraction by up to 14% when the blade is optimized near the cut-in wind speed, and by 7% when optimized at the rated wind speed. Using the results from optimizations at discrete wind speeds, two blade design strategies are evaluated to determine a single composite layup for the blade that maximizes power output over the range of operational wind speeds.

An advanced modeling system for optimization of wind farm layout and wind turbine sizing using a multi-level extended pattern search algorithm

This paper presents a system of modeling advances that can be applied in the computational optimization of wind plants. These modeling advances include accurate cost and power modeling, partial wake interaction, and the effects of varying atmospheric stability. To validate the use of this advanced modeling system, it is employed within an Extended Pattern Search (EPS)-Multi-Agent System (MAS) optimization approach for multiple wind scenarios. The wind farm layout optimization problem involves optimizing the position and size of wind turbines such that the aerodynamic effects of upstream turbines are reduced, which increases the effective wind speed and resultant power at each turbine. The EPS-MAS optimization algorithm employs a profit objective, and an overarching search determines individual turbine positions, with a concurrent EPS-MAS determining the optimal hub height and rotor diameter for each turbine. Two wind cases are considered: (1) constant, unidirectional wind, and (2) three discrete wind speeds and varying wind directions, each of which have a probability of occurrence. Results show the advantages of applying the series of advanced models compared to previous application of an EPS with less advanced models to wind farm layout optimization, and imply best practices for computational optimization of wind farms with improved accuracy.

Efficiency Comparison of Power Electronic Converters Used in Grid-Connected Permanent-Magnet Wind Energy Conversion System Based on Semiconductors Power Losses

An efficiency comparison of power converters is presented for a permanent magnet generator based grid-connected wind energy conversion system. The power converters examined are: the intermediate boost converter (IBC), the intermediate buck-boost converter (IBBC), the back-to-back converter (BBC) and the matrix converter (MC). The aim is to determine which power electronic converter yields the highest efficiency in terms of power losses of the semiconductor devices with the varying wind speeds. In view of this, a furled wind turbine model is developed that generates power for different wind speeds. Afterwards, a relation between the wind speed and power loss is established to evaluate the efficiency of the power electronic converters for discrete wind speeds. The power loss model presented in this paper has taken into account the conduction and switching losses of the semiconductor devices within each converter. Simulation results are presented showing the power loss characteristics with the variation in wind speeds. Finally, with regard to the global efficiency for the power electronic converters of the considered wind speed regime, the IBC is found to be the most favourable choice considering the typical wind conditions encountered by a wind energy conversion system operating at the kWatt level.

Convective heat transfer coefficients for exterior building surfaces: Existing correlations and CFD modelling

Convective heat transfer at exterior building surfaces has an impact on the design and performance of building components such as double-skin facades, solar collectors, solar chimneys and ventilated photovoltaic arrays, and also affects the thermal climate and cooling load in urban areas. In this study, an overview is given of existing correlations of the exterior convective heat transfer coefficient (CHTC) with the wind speed, indicating significant differences between these correlations. As an alternative to using existing correlations, the applicability of CFD to obtain forced CHTC correlations is evaluated, by considering a cubic building in an atmospheric boundary layer. Steady Reynolds-averaged Navier–Stokes simulations are performed and, instead of the commonly used wall functions, low-Reynolds number modelling (LRNM) is used to model the boundary-layer region for reasons of improved accuracy. The flow field is found to become quasi independent of the Reynolds number at Reynolds numbers of about 10 5. This allows limiting the wind speed at which the CHTC is evaluated and thus the grid resolution in the near-wall region, which significantly reduces the computational expense. The distribution of the power-law CHTC- U 10 correlation over the windward and leeward surfaces is presented ( U 10 = reference wind speed at 10 m height). It is shown that these correlations can be accurately determined by simulations with relatively low wind speed values, which avoids the use of excessively fine grids for LRNM, and by using only two or three discrete wind speed values, which limits the required number of CFD simulations.

Global ocean wind power sensitivity to surface layer stability

Global ocean wind power has recently been assessed (W. T. Liu et al., 2008) using scatterometry‐based 10 m winds. We characterize, for the first time, wind power at 80 m (typical wind turbine hub height) above the global ocean surface, and account for the effects of surface layer stability. Accounting for realistic turbine height and atmospheric stability increases mean global ocean wind power by +58% and −4%, respectively. Our best estimate of mean global ocean wind power is 731 W m−2, about 50% greater than the 487 W m−2 based on previous methods. 80 m wind power is 1.2–1.5 times 10 m power equatorward of 30° latitude, between 1.4 and 1.7 times 10 m power in wintertime storm track regions and >6 times 10 m power in stable regimes east of continents. These results are relatively insensitive to methodology as wind power calculated using a fitted Weibull probability density function is within 10% of power calculated from discrete wind speed measurements over most of the global oceans.

Wind-induced instability of structures

Forms of wind-induced instability of structures are described, and two of these, typical of long bodies with bluff cross-sections, are selected for more detailed consideration. The first is vortex-induced bending oscillation, a type of resonant response to the periodic surface pressure loading caused by the discrete wake vortex street formed from the shear layers separating from the bluff cross-section. Oscillation phenomena are described, including capture of the vortex frequency by the structural response frequency over a discrete wind speed range and amplification and phase shift of the loading over this range. The second form is transverse galloping, arising from aerodynamic instability of the bluff cross-sectional shape, so that small-amplitude oscillations generate forces which increase the amplitudes to large values. Oscillation phenomena are described, including the occurrence at very nearly natural frequencies, and the relatively large amplitudes (compared to vortex-induced oscillations) increasing with wind speed beyond a critical wind speed dependent on the level o fstructural damping. Effects of body and wind parameters on both forms of oscillation are considered, and methods of analysis and suppression for susceptible structures are described. Some probable future requirements and prospects are considered.

The Vertical Mean Wind Profile Over the Ocean for Light to Moderate Winds

Analysis of 299 wind profile observations collected at the Massachusetts Institute of Technology oceano-graphic research platform provides a detailed picture of the behavior of wind profile parameters. A plot of roughness length vs velocity suggests the existence of classical hydrodynamic phenomena such as Jeffreys’ minimum wind speed and the Kelvin-Helmholtz instability. The friction velocity appears to be, in general, a linear function of the wind velocity, except in regions where discontinuities exist. It is suggested that the air flow regime over the ocean in the wind range of 2-10 m sec−1 (measured at a height of 10 m) is best described as a region of constant drag coefficient (CD = 1.6 × 10−3) modified by the superposition of almost singular departures at a number of discrete wind speeds, apparently caused by the onset of distinct instabilities at the water's surface.