天氣預報模式與風能統計分析在風場開發之應用

An Application of the Weather Prediction Model and the Wind Statistics in Wind Farm Development

陳建廷(Chien-Ting Chen)

指導教授 ： 張建成

共同指導教授 ： 郭志禹

國立臺灣大學/工學院/應用力學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602722

摘要

近年來，離岸風能於再生能源中扮演舉足輕重的角色。開發離岸風場時，兩種區域性的風能評估(WRA) 是不可或缺的: 1. 實測資料風能統計分析，2. 數值天氣預報(NWP)之風能模擬。另一方面，為了產生較多電能，風機體積隨之增大，更多的動量從大氣中被截取，這意味大型風機對大氣邊界層、環境之影響將更為顯著。因此，離岸風場對大氣環境的影響需被重視。

基於以上，本研究以大氣研究軟體(WRF 模式) 之模擬，與福海氣象塔實測資料比對，詮釋台灣彰化離岸風能，並結合工程觀點探討其風場開發。考量風場運作，本研究利用Fitch 等人提出的風機參數化模型，進行福海風力發電股份有限公司於彰濱外海預訂30 台SWT-4.0-120 風機(第一、二期) 之風場模擬。經模擬後，發現風場後方有相當顯著、最大損失2(m/s) 的風場尾流。為了驗證其結果，本研究以一維動量理論做基本驗證，並進一步探討尾流特徵與尾流擾動等特性。此外，藉由Jensen 單一風機尾流模型構想，推廣出改良式尾流模型，以對風場開發進行初步的尾流評估。比較模型與模擬之尾流中心線速度恢復，發現風場的尾流衰變常數(wake decay constant) 與單一風機有相當程度的關聯性，間接證明了風場尾流能以單一風機來比擬。除了數值模擬，本文亦利用實測的冬季(10/7 ~ 11/7, 2015) 與夏季(5 月, 2016) 一個月風資料，依據國際規範IEC 61400 所制定的準則，以客觀角度評估台灣彰濱外海季節性風勢能。最後，台灣典型的極端風速條件將以杜鵑颱風(9/27 _ 29, 2015) 的風資料呈現，並參考IEC 61400 之極端風速模型(EWM)，比較預訂風機所能承受的極端風力條件。

總結，希望能夠以此研究首次呈現數值天氣預報模式在台灣風場開發之應
用，並嘗試結合工程觀點解釋風場尾流影響，最後再進一步藉由海象氣象塔風能統計資料分析，以全面性探討彰濱離岸風力資源。

關鍵字

離岸風能 ； 風能評估 ； 福海氣象塔 ； WRF 模式 ； Fitch 參數化 ； 尾流特徵 ； 尾流擾動 ； Jensen 模型 ； 尾流衰變常數 ； IEC 61400 規範 ； 極端風速模型

並列摘要

Offshore wind energy have played an important role in sustainable energy recently. In the development of the offshore wind farm, two regional wind resources assessments (WRA): 1.wind statistics on the measurements of meteorological mast and 2.application of numerical weather prediction (NWP) to wind simulation are significant and indispensable without doubts. On the other hand, in order to generate more electrical power, the size of the wind turbine has been enlarged for extracting more momentum from the atmosphere. However, it also implies that the influences of the atmospheric boundary layer and the environment will be significantly occurred. Thus, issues such as the environmental impacts on the atmosphere due to the wind farm operation are worthy to be alerted.

According to the above statements, in this study, the simulation by conducting atmospheric research software (WRF model) with the comparison of data provided by the Fu-Hai met mast is drawn to present the offshore wind energy of Changhua, Taiwan. Further, the wind farm development taken in combination with the engineering perspectives are also addressed. Considering the wind farm operation, parameterization of the wind turbine proposed by Fitch et al. was applied to simulate the 30 SWT-4.0-120 wind turbines (Phase I + II) designed by the Fuhai Wind Farm Corporation at offshore Changhua. Results of the parameterization showed a distinct wake with a nearly 2 (m/s) velocity deficit behind the scheduled wind farm. To verify them, a 1D momentum theory is used for fundamental validation and the further evaluation of the wake effect such as the wake characteristics, wake fluctuation and related properties are followed. Moreover, a modified wake model based on Jensen’s approaches is proposed to preliminarily evaluate the wake effect of wind farm. Having compared with the results of the modified wake model and Fitch scheme, it was found that the wake decay constant of wind farm had a substantially connection to the suggestion of single wind turbine. It is, therefore indirect to indicate the wake performance of wind farm can be imitated to a single wind turbine. In addition to numerical simulation, the objective assessment of wind resources at offshore Changhua is concerned. Based on the regular criterion proposed by the IEC standards, the wind statistics on the measurements of one month winter (Oct. 7~Nov. 7, 2015) and summer (May, 2016) data are presented to evaluate the seasonal wind potential. Finally, the typical extreme weather condition of Taiwan are illustrated by the wind data of Du- Juan Typhoon (Sep. 27~29, 2015). Additionally, to verify the maximum allowable wind condition of the scheduled wind turbine, the results were compared with the extreme wind speed model (EWM) suggested by IEC standards.

To conclude, in Taiwan, this is a first study which might be of importance in applying the NWP model to wind farm development, attempting to explain the wake effect of wind farm with engineering perspectives, as well as in providing the wind statistics with a comprehensive understanding of the offshore wind resources of Changhua.

並列關鍵字

offshore wind energy ； wind resources assessment ； Fu-Hai meteorological mast ； WRF model ； Fitch scheme ； wake characteristics ； wake fluctuation ； Jensen wake model ； wake decay constant ； IEC 61400 standards ； extreme wind speed model

參考文獻

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