極端風況與尾流動態分析在風場開發之應用

An Application of Extreme Wind Regimes and Wake Dynamical Analysis in Wind Farm Developments

端木豫(Yu Tuan-Mu)

指導教授 ： 張建成

共同指導教授 ： 郭志禹(Chih-Yu Kuo)

國立臺灣大學/工學院/應用力學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702781

摘要

台灣近年致力於發展再生能源，特別是離岸風電場的開發。雖然台灣海峽擁有世上罕見的絕佳風場，但是卻有一些問題必須面對。不同於離岸風場發展成熟的北歐地區，亞洲地區每年夏秋之際都受到颱風侵襲。對於颱風侵襲，中央氣象局依據颱風侵台路線歸類出10種路徑。在本研究中，研究從2015年9月到2016年底之間四種不同侵臺路徑的颱風:杜鵑、尼伯特、莫蘭蒂與梅姬颱風。

本研究藉由彰濱外海福海氣象塔紀錄四個颱風所量測到的實際資料進行風況特徵分析，並與IEC 61400s所規範的極限風速模型、一般紊流模型、極端紊流模型與垂直風切值進行比較，給出福海地區建議的風機選擇種類與設計要求。除了實際資料分析外，本研究使用中尺度數值天氣預報系統(WRF模式)進行福海地區極端氣候的風況重建，並在結果中呈現了GFS-FNL初始資料在極端氣候下模擬相對於ERA-interim初始資料更近似於實際風況，也應證全時段模擬法相對於大氣研究常用的36小時模擬法更適用在極端氣候下之模擬。除了極端氣候下風況會造成離岸風場葉片斷裂與崩塌外，風場後方尾流擾動效應亦會造成風機的疲勞性結構破壞，因此本研究利用適當正交分解法(POD)分析彰濱外海預定30台SWT-4.0-120風機後方尾流擾動動態分析，藉由主要的模態描述整段時間下的尾流擾動結構，快速傅立葉轉換所對應的重建係數求出每個模態所對應的響應頻率。

總結，希望藉由本文研究呈現福海地區在極端氣候下的風況特徵，並利用WRF模式重建該地區極端風況的歷史訊息，給出福海地區離岸風場在極端氣候下的風機建議選擇，最後藉由POD分析尾流擾動動態，以期作為福海地區下游風場規劃與開發的重要依據。

關鍵字

台灣福海 ； 颱風 ； IEC 61400s 規範 ； 極限風速模型 ； 一般紊流模型 ； 極端紊流模型 ； 垂直風切 ； 風機選擇種類 ； WRF 模式 ； 適當正交分解 ； 擾動動態分析

並列摘要

Renewable energy has been recently devoted to developing in Taiwan, especially the development of offshore wind farms. Taiwan Strait is gifted with the rarest outstanding offshore wind resources in the world. However, couples of dilemmas are followed when constructing wind farms on it. Different from the developed wind farms of Northern Europe, the regime of Pacific Asia are facing with the typhoon strikes in the period between summer and autumn of every single year. According to the typhoon databases of Central Weather Bureau, the typhoon trajectories are divided into ten different paths. In this study, four of ten kinds of typhoon：Du-Juan, Nepartak, Meranti and Megi that have struck on Taiwan between September 2015 and December 2016 are addressed.

In this study, the wind data of four typhoons were recorded by Fuhai offshore meteorological mast which is located at about 8 km from the Chunghwa coastline. Based on the characteristics of extreme winds and the diversified model analysis of IEC 61400s standards, the extreme wind speed model (EWM), the normal turbulence model (NTM), the extreme turbulence model (ETM) and vertical wind shear are included into the standard criterion. Furthermore, the adoption of the type of wind turbine and design requirements for the Fuhai offshore wind farm is suggested. On the other hand, the Weather Research and Forecast model (WRF model), a famous mesoscale atmospheric numerical system, is selected to reconstruct the characteristics of wind regimes of Fuhai area and the associated numerical results are evaluated by the measured wind data. Consider the results of extreme weather condition with two different initial data, the GFS-FNL is better than the ERA-interim reanalysis data, and the full-time method is more reliable than the commonly used 36hrs method in atmospheric studies. Additionally, the collapse and damage of the wind turbines are the significant issues for the maintenance of the wind farm operation. Not only in the extreme weather condition but the effect of wake fluctuation might also cause the structural damage of the downstream wind turbines. Therefore, the proper orthogonal decomposition (POD) is chosen to discuss the dynamic structures of the wake fluctuation behind the 30 SWT-4.0-120 of wind turbines around Fuhai area. Through this method, the main structure of the wake fluctuation during the simulation period can be identified by the main mode and the corresponded response frequencies are available to be obtained by the Fast Fourier Transform with the given reconstruction coefficients of each mode.

To sum up, this study is aiming to present the extreme wind characteristics in Fuhai area, apply WRF model to reconstruct the historical wind condition, provide the adoption of wind turbines based on the extreme weather condition in Fuhai area. Last but not the least, it is expected to be an important contribution on the basis of POD dynamic analysis for the deployment and development of the offshore wind farm behind the Fuhai offshore wind farm.

並列關鍵字

Fuahai area ； typhoon ； IEC 61400s standards ； the extreme wind speed model ； the normal turbulence model ； the extreme turbulence model ； vertical wind shear ； subclass of wind turbines ； WRF model ； proper orthogonal decomposition ； the dynamical analysis of wake fluctuation

參考文獻

[1] T. W. Feng, C. H. Lee, C. T. Chen, C. Y. Kuo, and C. C. Chang. Installation and Data Acquisition Analysis of the Primary Offshore Meteorological Mast of Taiwan. In Proceedings of the 18th Ocean & Underwater Technology and , National Cheng Kung University. Chinese Ocean & Underwater Technology Association, May 2016.

[4] IEC 61400-3. Design requirements for offshore wind turbines. International Electrotechnical Commission, 2009.

[5] Z. Q. Li, S. J. Chen, H. Ma, and T. Feng. Design defect of wind turbine operating in typhoon activity zone. Engineering Failure Analysis, 27:165–172, 2013.

[6] T. S. Leu, J. M. Yo, Y. T. Tsai, J. J. Miau, T. C. Wang, and C. C. Tseng. Assessment of IEC 61400-1 Normal Turbulence Model for Wind Conditions in Taiwan West Coast Areas. In International Journal of Modern Physics: Conference Series, volume 34, page 1460382. World Scientific, 2014.

[7] J. Y. Chen, H. Y. Tsai, T. S. Leu, and J. J. Miau. Wind Characteristics Studies of Fuhai Offshore Wind Mast of Taiwan Generations Corporation and its Comparison with Normal Wind Conditions in IEC 61400. In Taiwan Wind Energy Association, National Taiwan Ocean University. Taiwan Wind Energy Association, December 2016.