Next Article in Journal
Nuclear Power Learning and Deployment Rates; Disruption and Global Benefits Forgone
Next Article in Special Issue
Machine Learning for Wind Turbine Blades Maintenance Management
Previous Article in Journal
A Combined Electro-Thermal Breakdown Model for Oil-Impregnated Paper
Previous Article in Special Issue
Structural Reliability Analysis of Wind Turbines: A Review
Article Menu
Issue 12 (December) cover image

Export Article

Open AccessArticle
Energies 2017, 10(12), 2164; doi:10.3390/en10122164

Flow Adjustment Inside and Around Large Finite-Size Wind Farms

Wind Engineering and Renewable Energy Laboratory (WIRE), School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL), EPFL-ENAC-IIE-WIRE, 1015 Lausanne, Switzerland
*
Author to whom correspondence should be addressed.
Received: 1 December 2017 / Revised: 13 December 2017 / Accepted: 14 December 2017 / Published: 18 December 2017
(This article belongs to the Collection Wind Turbines)
View Full-Text   |   Download PDF [23119 KB, uploaded 18 December 2017]   |  

Abstract

In this study, large-eddy simulations are performed to investigate the flow inside and around large finite-size wind farms in conventionally-neutral atmospheric boundary layers. Special emphasis is placed on characterizing the different farm-induced flow regions, including the induction, entrance and development, fully-developed, exit and farm wake regions. The wind farms extend 20 km in the streamwise direction and comprise 36 wind turbine rows arranged in aligned and staggered configurations. Results show that, under weak free-atmosphere stratification ( Γ = 1 K/km), the flow inside and above both wind farms, and thus the turbine power, do not reach the fully-developed regime even though the farm length is two orders of magnitude larger than the boundary layer height. In that case, the wind farm induction region, affected by flow blockage, extends upwind about 0.8 km and leads to a power reduction of 1.3% and 3% at the first row of turbines for the aligned and staggered layouts, respectively. The wind farm wake leads to velocity deficits at hub height of around 3.5% at a downwind distance of 10 km for both farm layouts. Under stronger stratification ( Γ = 5 K/km), the vertical deflection of the subcritical flow induced by the wind farm at its entrance and exit regions triggers standing gravity waves whose effects propagate upwind. They, in turn, induce a large decelerating induction region upwind of the farm leading edge, and an accelerating exit region upwind of the trailing edge, both extending about 7 km. As a result, the turbine power output in the entrance region decreases more than 35% with respect to the weakly stratified case. It increases downwind as the flow adjusts, reaching the fully-developed regime only for the staggered layout at a distance of about 8.5 km from the farm edge. The flow acceleration in the exit region leads to an increase of the turbine power with downwind distance in that region, and a relatively fast (compared with the weakly stratified case) recovery of the farm wake, which attains its inflow hub height speed at a downwind distance of 5 km. View Full-Text
Keywords: atmospheric boundary layer (ABL); boundary-layer depth; exit region; farm wake; induction region; large-eddy simulation (LES); large finite-size wind farm; turbulence atmospheric boundary layer (ABL); boundary-layer depth; exit region; farm wake; induction region; large-eddy simulation (LES); large finite-size wind farm; turbulence
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Share & Cite This Article

MDPI and ACS Style

Wu, K.L.; Porté-Agel, F. Flow Adjustment Inside and Around Large Finite-Size Wind Farms. Energies 2017, 10, 2164.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Energies EISSN 1996-1073 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top