When wind turbines are deployed in large arrays, their ability to extract kinetic energy from the flow decreases due complex interactions among them, terrain topography and atmospheric boundary layer. In order improve understanding of vertical transport momentum across a layer with turbines, wind-tunnel experiment is performed. The includes 3×3 array model turbines. Particle-image-velocity measurements volume surrounding target turbine used compute mean velocity turbulence properties...

Wind tunnel experiments were performed, where the development of wake a model wind turbine was measured using stereo Particle Image Velocimetry to observe influence platform pitch motion. The wakes classical bottom fixed and streamwise oscillating are compared. Results indicate that creates an upward shift in all components flow their fluctuations. vertical created by motion as well reduced entrainment kinetic energy from undisturbed flows above result potentially higher loads less available...

Abstract To improve the performance of solar photovoltaic devices one should mitigate three types losses: optical, electrical and thermal. However, further reducing optical losses in modern is becoming increasingly costly. Therefore, there a rising interest minimizing thermal losses. These correspond to reduction power output resultant working at temperatures above 25 °C associated accelerated aging. Here, we quantify impact all possible strategies case mainstream crystalline silicon...

For large wind farms, kinetic energy must be entrained from the flow above turbines to replenish wakes and enable power extraction in array. Various statistical features of turbulence causing vertical entrainment mean-flow are studied using hot-wire velocimetry data taken a model farm scaled tunnel experiment. Conditional statistics spectral decompositions employed characterize most relevant turbulent structures determine their length-scales. Sweep ejection events shown largest contributors...

An array of model turbines with rotors is compared experimentally to an stationary porous disks. The main discrepancy in the mean velocity components between two cases found out-of-plane component while fluctuations are play a dramatically different role vertical flux kinetic energy. study has wide implications on use actuator disk as parametrization for rotor computational work.

Abstract Performance of solar PV diminishes with the increase in temperature modules. Therefore, to further facilitate reduction cost photovoltaic energy, new approaches limit module natural ambient conditions should be explored. Thus far only based at individual panel level have been investigated, while more complex, systems approach remains unexplored. Here, we perform first wind tunnel scaled farm experiments investigate potential for through system-level flow enhancement. The percentage...

An isolated wind turbine and a very large farm are introduced into large-eddy simulations of an atmospheric boundary layer. The flow is forced with constant geostrophic time-varying surface temperature extracted from selected period the CASES-99 field experiment. A control volume approach used to directly compare transfer mean kinetic energy around characteristic throughout diurnal cycle considering both scenarios. For case, results illustrate that recovery dominated by vertical flux,...

Abstract A reduced‐order model for a wind turbine wake is sought from large eddy simulation data. Fluctuating velocity fields are combined in the correlation tensor to form kernel of proper orthogonal decomposition (POD). Proper modes resulting represent spatially coherent turbulence structures wake; eigenvalues delineate relative amount turbulent kinetic energy associated with each mode. Back‐projecting POD onto snapshots produces dynamic coefficients that express amplitude mode time....

Abstract

A data-driven approach is an alternative to extract general models for wind energy applications. spatial sensitivity analysis achieved using a probabilistic model quantitatively identify the variability in performance due individual parameters and visualize distributions. Proper orthogonal decomposition results are combined with linear discriminant under clustering framework present low-dimensional classifiers. Using enables system be far away from ill-conditioned states. The optimal sensor...

A 4 × 3 wind turbine array in a Cartesian arrangement was constructed tunnel setting with four configurations based on the rotational sense of rotor blades. The fourth row devices is considered to be fully developed canopy for arrangement. Measurements flow field were made stereo particle-image velocimetry immediately upstream and downstream selected model turbines. Rotational blades evident mean spanwise velocity W Reynolds shear stress −vw¯. flux kinetic energy shown greater magnitude...

To understand the complex flow phenomena over wind turbine blades during stall development, a scaled three-dimensional non-rotating blade model is designed to be dynamically similar rotating full-scale NREL 5 MW blade. A time-resolved particle image velocimetry (PIV) investigation of behavior cycle examines processes development and reattachment. Proper orthogonal decomposition (POD) vortex detection techniques are applied PIV fields quantify relevant characteristics such as size, separation...

Wind turbine wakes are investigated in order to characterize the development of energetic turbulence structures. Experimental data from stereo particle image velocimetry render full Reynolds stress tensor accessible planes parallel swept area scale model rotor. Proper orthogonal decomposition (POD) is applied decompose and analyze structures wake. The modes resulting demonstrate that grow develop along streamwise direction. A second iteration snapshot POD, otherwise called double proper...

A large eddy simulation framework is used to explore the structure of turbulent flow in a thermally stratified wind turbine array boundary layer. The field driven by constant geostrophic with time-varying surface conditions obtained from selected period CASES-99 experiment. Proper orthogonal decomposition extract coherent structures under considered thermal stratification regimes. discussed context three-dimensional representations key modes, which demonstrate features ranging size wakes...

Laser Doppler anemometry measurements are carried out in order to investigate the influences of external conditions on a transitionally rough favorable pressure gradient turbulent boundary layer. The acquired data is normalized using scalings obtained by means equilibrium similarity outer flow. point at hand not only understand interaction between surface and flow but also include as evolves streamwise direction. It found that velocity profiles show effects upstream imposed when with...

Abstract Cartesian and row‐offset wind turbine array configurations were tested investigating the wake interaction recovery dynamics. The snapshot proper orthogonal decomposition is applied to velocity measurements. Resulting modes are used in constructing low‐dimensional descriptions of turbulence statistics including kinetic energy production flux energy. Descriptions turbulent behavior made on basis span streamwise average profile Reynolds shear stress, , with addition modes. stress...

Tilting the nacelle of a wind turbine modifies entrainment into plant and impacts total efficiency. Wakes are deflected vertically by tilt in case large angles can disrupt entertainment from undisturbed flow or dissipate on ground. The effect wake behavior is investigated series tunnel experiments for first time. Scale model turbines with hub height diameter 12 cm arranged Cartesian array composed four rows three each. angle was varied third row −15° to 15° chosen 5° increments. Stereo...

When solar photovoltaic (PV) module temperatures rise during operation, commonly-installed modules experience an efficiency loss between 0.1 and 0.5% per degree above 25∘C. Thus, extensive research has aimed to reduce the operating temperature of modules. However, many cooling solutions require additional cost or equipment that precludes their implementation in utility-scale PV plants. Based on previous studies land-atmosphere interactions surface thermal heterogeneity, we hypothesize...

Abstract Individual turbine location within a wind plant defines the flow characterisitcs experienced by given turbine. Irregular arrays and inflow misalignment can reduce efficiency producing highly asymmetric wakes with enhanced downstream longevity. Changes in wake dynamics as result of position were quantified tunnel experiment. Scale model turbines rotor diameter 20 cm hub height 24 placed symmetric, asymmetric, rotated configurations. Simultaneous velocity measurements recorded at 11...

Abstract. The eddy viscosity hypothesis is a popular method in wind turbine wake modeling for estimating turbulent Reynolds stresses. We document the downstream evolution of from experimental and large-eddy-simulation data. Wake isolated its surroundings by subtracting inflow profile, driving forces are identified each region. Eddy varies response to changes geometry nacelle misalignment with larger turbines generating stronger velocity gradients shear propose model based on Rayleigh...