Effects of Terrain-Induced Turbulence on Wind Turbine Blade Fatigue Loads

Yasushi Kawashima,Takanori Uchida

doi:10.4236/epe.2017.913053

Abstract

Recently, the issue has surfaced that the availability factors for wind farms built on complex terrain are lower than the originally projected values. In other words, problems have occurred such as extreme decreases in generation output, failures of components inside and outside wind turbines including yaw motors and yaw gears, and cracking on wind turbine blades. As one of the causes of such issues, the effects of wind turbulence (terrain-induced turbulence) have been pointed out. In this study, we investigated the effects of terrain-induced turbulence on the structural strength of wind turbines through the measurement of strains in wind turbine blades and the analysis of wind data in order to establish a method for optimal wind turbine deployment that uses numerically simulated wind data and takes the structural strength of wind turbines into consideration. The investigation was conducted on Wind Turbine #10 of the Kushikino Reimei Wind Farm (in operation since Nov. 2012) in cooperation with Kyudenko New Energy Co., Ltd. Subsequently, we conducted numerical wind simulations (diagnoses of terrain-induced turbulence) to study the effects of the properties of airflow on the structural strength of wind turbines. For these simulations, the natural terrain version of the RIAM-COMPACT software package, which is based on large eddy simulation (LES), was used. The numerical simulations successfully reproduced the characteristics of the wind conditions and the structure of the three-dimensional airflow. These results enabled us to determine the threshold value for a turbulence index to be used for optimal wind turbine deployment planning that utilizes quantitative data from simulations with the natural terrain version of the RIAM-COMPACT software package.

Highlights

In recent times, the availability factors of wind farms constructed over complex terrain in mountains and other areas have fallen below the initially projected values
We investigated the effects of terrain-induced turbulence on the structural strength of wind turbines through the measurement of strains in wind turbine blades and the analysis of wind data in order to establish a method for optimal wind turbine deployment that uses numerically simulated wind data and takes the structural strength of wind turbines into consideration
The present study focuses on Wind Turbine (WT) #10, for which there is a concern that it is affected by turbulence which is generated when wind flows over Mt

Summary

Introduction

The availability factors of wind farms constructed over complex terrain in mountains and other areas have fallen below the initially projected values. When land-based wind turbines in Japan are constructed in the future, it can be anticipated that construction will continue to take place in complex terrain such as mountainous areas, as a result of the search for well-suited deployment sites. Highly-accurate evaluation methods for wind turbine deployment need to be established in order to reduce wind turbine accidents and failures. Given this circumstance, our research group has conducted “highly accurate numerical wind simulations (numerical wind diagnoses) with the RIAMCOMPACT natural terrain version software package [1]”. Based on the in-situ data, the wind direction is identified for which the structural strength of the wind turbine is most affected. A planning method is proposed for optimal wind turbine deployment, a method which uses numerical simulation results and takes wind turbine structural strength criteria into consideration

Overview of Kushikino Reimei Wind Farm

Overview of Numerical Simulation Method

Overview of Numerical Wind Simulation Set-Up

Simulation Results and Discussions

Conclusions