摘要 :
The phenomenon of wake meandering is long known empirically, but has so far not been treated in a satisfactory manner on the wind turbine load modelling side. We present a consistent, physically based theory for wake meandering, w...
展开
The phenomenon of wake meandering is long known empirically, but has so far not been treated in a satisfactory manner on the wind turbine load modelling side. We present a consistent, physically based theory for wake meandering, which we consider of crucial importance for the overall description of wind turbine loadings in wind farms. In its present version, the model is confined to single wake situations-including a simple heuristic description of wake interaction with a reflecting surface. Contrary to previous attempts to model wind turbine wake loading, the present approach opens for a unifying description in the sense that turbine power and load aspects can be treated simultaneously. This capability is a direct and attractive consequence of the model being based on the underlying physical process, and it potentially opens for optimization of wind farm topology, wind farm operation, as well as control strategies for the individual turbine. The application of the proposed dynamic wake meandering methodology with existing aeroelastic codes is straightforward and does not involve any code modifications. The strategy is simply to embed the combined effect of atmospheric turbulence, added wake turbulence and the intermittent 'turbulence contribution', caused by wake meandering, in files replacing the traditional turbulence file input to aeroelastic computations.
收起
摘要 :
The wake interference effect on the performance of a downstream wind turbine was investigated experimentally. Two similar model turbines with the same rotor diameter were used. The effects on the performance of the downstream turb...
展开
The wake interference effect on the performance of a downstream wind turbine was investigated experimentally. Two similar model turbines with the same rotor diameter were used. The effects on the performance of the downstream turbine of the distance of separation between the turbines and the amount of power extracted from the upstream turbine were studied. The effects of these parameters on the total power output from the turbines were also estimated. The reduction in the maximum power coefficient of the downstream turbine is strongly dependent on the distance between the turbines and the operating condition of the upstream turbine. Depending on the distance of separation and blade pitch angle, the loss in power from the downstream turbine varies from about 20 to 46% compared to the power output from an unobstructed single turbine operating at its designed conditions. By operating the upstream turbine slightly outside this optimum setting or yawing the upstream turbine, the power output from the downstream turbine was significantly improved. This study shows that the total power output could be increased by installing an upstream turbine which extracts less power than the following turbines. By operating the upstream turbine in yawed condition, the gain in total power output from the two turbines could be increased by about 12%.
收起
摘要 :
Wind farm control has demonstrated power production improvements using yaw-based wake steering compared to individual turbine optimization. However, slower yaw actuation rates in response to rapid inflow changes lend to impractica...
展开
Wind farm control has demonstrated power production improvements using yaw-based wake steering compared to individual turbine optimization. However, slower yaw actuation rates in response to rapid inflow changes lend to impracticality of yaw-based steering, as it causes time-varying downstream rotor-wake overlap, power production fluctuation, and consequent reduction. Therefore, closed-loop wake control is required to mitigate wake deflection uncertainty. To respond to rapid inflow variations, rotor speed actuated is investigated here. Furthermore, wake position information is required as feedback for closed-loop control function. For field-installed turbines, nacelle-based Light detection and ranging (LIDAR) is expected to provide this information. So far, LIDAR-derived wake position has been determined through model-based field reconstruction of scattered LIDAR data. However, this requires sophisticated, economically prohibitive LIDARs. To incorporate inexpensive, two-beam LIDAR for wake detection, a tip vortex-based approach was developed and is also presented here. These contributions can be considered as intermediate steps toward realization of a novel closed-loop wake control.
收起
摘要 :
One of the current major challenges in wind energy is to maximize energy production of wind farms. One approach in this effort is through control of wind turbine wake interactions, since undesirable wake interactions can introduce...
展开
One of the current major challenges in wind energy is to maximize energy production of wind farms. One approach in this effort is through control of wind turbine wake interactions, since undesirable wake interactions can introduce additional mechanical stresses on turbines, leading to early failures and reduce overall energy production of wind farms. To develop control strategies that can minimize wake interactions, it is essential to simulate wake behaviors accurately and quickly. In this work, a fast and accurate turbine wake model capable of modeling turbine wakes under yaw is presented. This model builds upon the work of existing wake models and is capable of producing results comparable to that of conventional full CFD simulations using a fraction of the computational cost. The accuracy and speed of the proposed model allows for the development of real-time turbine control strategies to maximize power output. The results of the proposed model are validated with previous numerical and experimental data. Published by Elsevier Ltd.
收起
摘要 :
This research explores the trade-offs between a wind farm's average power production and noise impact on nearby observers. Two specific wind farm designs were studied and optimized using the FLORIS wake model and an acoustic model...
展开
This research explores the trade-offs between a wind farm's average power production and noise impact on nearby observers. Two specific wind farm designs were studied and optimized using the FLORIS wake model and an acoustic model based on semi-empirical turbine noise calculations. It was found in the two wind farms that the average power production could be increased, up to 8.01% in one and 3.63% in the other, ignoring sound level considerations. Including a noise restriction in the optimization had a minimal impact on the optimal average power production within aboufa five-decibel range. Past this range, sound limitations decreased the wind farm's power production significantly. By analyzing average power production and sound pressure level together, we can take advantage of the multi-modality of the optimization to find solutions were noise impact can be improved with an insignificant effect on power production. (C) 2017 Elsevier Ltd. All rights reserved.
收起
摘要 :
We present an improved dynamic model to predict the time-varying characteristics of the far-wake flow behind
a wind turbine. Our model, based on the FAST.Farm engineering model, is novel in that it estimates the
turbulence gener...
展开
We present an improved dynamic model to predict the time-varying characteristics of the far-wake flow behind
a wind turbine. Our model, based on the FAST.Farm engineering model, is novel in that it estimates the
turbulence generated by convective instabilities, which selectively amplifies the inflow velocity fluctuations.
Our model also incorporates scale dependence when calculating the wake meandering induced by the
passive wake meandering mechanism. For validation, our model is compared with FAST.Farm and largeeddy
simulation (LES). For the mean flow, our model agrees well with LES in terms of the wake deficit
and wake width, but the FAST.Farm model underestimates the former and overestimates the latter. For the
instantaneous flow, our model predicts well the wake-center deflection and turbulent kinetic energy, reducing
the discrepancies in the spectral characteristics by more than a factor of two relative to LES, depending on
the Strouhal number. By incorporating two key mechanisms governing the far-wake dynamics, our model can
predict more accurately the dynamic wake evolution, making it suitable for real-time calculations of wind
farm performance.
收起
摘要 :
A wind farm's overall power production is significantly less than its nominal power, defined as the sum of the wind turbines' rated outputs. The primary cause for this significant loss is the exposure of downstream wind turbines t...
展开
A wind farm's overall power production is significantly less than its nominal power, defined as the sum of the wind turbines' rated outputs. The primary cause for this significant loss is the exposure of downstream wind turbines to the aerodynamic wake of their upstream counterparts. Wind farm layout optimization aims at minimizing such adverse effects by finding optimal wind turbine positions that are less exposed to the upstream wake. Over the past few years, researchers have extended their fight against adverse wake effects beyond the layout optimization, i.e., the design process, onto the control and operation process. Several active wake control strategies have been proposed and studied to decrease the power loss of downstream wind turbines by steering or weakening the upstream wakes. First, the article reviews these strategies, including yaw control, pitch control, torque control, tilt control, and finally, cone angle control. Then, it proposes a novel wake steering technique where passive stationary vanes redirect the upstream wake. The authors conducted scaled wind tunnel experiments to investigate the performance of the proposed concept. Using a 3D-printed wake deflector between two in-line turbines increased the downstream turbine's power production by more than 15%, which is significant compared to the existing wake control strategies. The article concludes by comparing the proposed technology's effectiveness against existing wake control techniques.
收起
摘要 :
Wind turbines are typically operated to maximize their performance without considering the impact of wake effects on nearby turbines. Wind plant control concepts aim to increase overall wind plant performance by coordinating the o...
展开
Wind turbines are typically operated to maximize their performance without considering the impact of wake effects on nearby turbines. Wind plant control concepts aim to increase overall wind plant performance by coordinating the operation of the turbines. This paper focuses on axial-induction-based wind plant control techniques, in which the generator torque or blade pitch degrees of freedom of the wind turbines are adjusted. The paper addresses discrepancies between a high-order wind plant model and an engineering wind plant model. Changes in the engineering model are proposed to better capture the effects of axial-induction-based control shown in the high-order model. Copyright (c) 2015 John Wiley & Sons, Ltd.
收起
摘要 :
The aim of the present paper is the analysis of simplified boundary conditions to be used in numerical simulations, to take into account blockage effects for wind tunnel experiments of large scale wind turbines. The goal is the de...
展开
The aim of the present paper is the analysis of simplified boundary conditions to be used in numerical simulations, to take into account blockage effects for wind tunnel experiments of large scale wind turbines. The goal is the development of an efficient and reliable tool to be used to correct data obtained from experiments where the blockage coefficient is high and/or the turbine is highly loaded, for which traditional correction coefficients (derived from the Glauert theory or its more recent versions) fail.
收起
原文获取