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Analysis on wave energy potential in coastal waters of Northeast Taiwan and off-shore islands and flume tests on wave field near a WEC
|Authors: ||Chun-Chih Wang|
|Contributors: ||NTOU:Department of Harbor and River Engineering|
coastal waters of northeast Taiwan;off-shore islands;wave energy;wave characteristic;HHT;wave energy conversion rate
|Issue Date: ||2011-11-23T03:18:43Z
|Abstract: ||本研究針對臺灣東北及海峽北部離島海域，包括了基隆港、蘇澳港、龍洞、蘇澳、金門、澎湖、馬祖七個測站，從2002~2010年之逐時波浪資料進行波浪統計及波能潛勢分析，另對蘇澳港及基隆港2008年的時序列資料進行週期特性分析以及應用HHT分析波能主頻與第一高頻在總能量上集中程度，並整理逐時資料之統計結果進行水槽模型試驗，從波浪轉換器模型前後之波高的變化，探討波能轉換在各種造波條件下之相關性。 逐時波浪之研究結果顯示，波高週期聯合分佈特性在東北海域週期多集中於6~8s，而以龍洞於秋、冬兩季週期達到9s為最高；離島海域波浪則多集中於4~6s。波高方面，離島區域澎湖波高可達2.5~3m，東北海域約1.5~2m。波向在基隆港、龍洞、蘇澳、澎湖、馬祖大部分時間為NE方向；蘇澳港、金門大部份時間則為E方向。波能潛勢結果顯示，東北海域超過10kw/m及平均波能，最高為龍洞冬季時約有30%以上超過10kw/m且平均波能最高達到約20kw/m，其次依序為基隆港、蘇澳港、蘇澳；離島海域超過10kw/m及平均波能，最高為馬祖，其次為澎湖及金門，而澎湖於冬季的時候約有30%以上超過10kw/m，平均波能達到15kw/m。深水與實際水深波能公式之計算結果，龍洞及蘇澳港因週期較大其差距可達1.2倍。 時序列資料分析波能週期Te與尖峰周期Tp之轉換係數Cep之年平均結果蘇澳港為0.8329，較基隆港同一年的Cep值0.8992為小。應用HHT拆解時序列波浪資料得到其主頻成份及次高頻成份在整年隨季節變化，結果顯示冬季最為集中，能量密度約佔總量的93.1%。最後，藉由現場波浪資料之縮尺計算結果，初步探討其在水槽試驗時及波能轉換器模型運動上的相互關係，藉由整體能量損失的概念，來代表波能轉換率，結果顯示當能量通量越高則波能轉換率越小並呈現指數遞減的關係，藉由此結果能對未來波能轉換器的設置做一個好的參考。|
In this study, hourly wave data from 2002 to 2010 of 7 field stations in coastal waters of northeast Taiwan and off-shore islands in Taiwan Strait, including Keelung Harbor, Su-ao Harbor, Longdong, Su-ao, Kinmen, Penghu, Matsu, have been analysed on wave statistics and energy potential. The temporal data in each hour from stations of Su-ao Harbor and Keelung Harbor in 2008 have been further analyzed by FFT and HHT for spectrum concentrations. Typical wave statistics were scaled down as the input conditions for flume tests on performance evaluation of a wave energy converter (WEC) model. The wave data on both up- and down-stream sides were measured and calculated for energy extraction ratio. In coastal waters of northeast Taiwan, the joint distributions of wave height and period have illustrated that waves concentrate about 1.5~2m in height and around 6~8s in period and up to 9s.in Longdon. Among the off-shore islands, waves concentrate around 4~6s in period while 2.5~3m in height at Penghu. The dominant wave derections are in NE direction except those in Harbor of Suao and Kinmen with E direction. Most of the monthly averaged wave energy potentials over 10kw/m occurre in winter season with highest values at Longdong to be over 30%. The subsequent smaller persentages are at Keelung Harbor, Suao Habor asnd Suao, respectively. At stations of off-shore islands, the results show that at Matsu the average wave energy potentials are highest and followed by Penghu and Kinmen while at Penghu the values could be more than 30% for those greater than 10kw/m. The comparisons of adopted formulae for between deep water and practical water depth have shown differences to be as high as 1.2 times at Longdong and Suao Habor due to longer wave period. Moreover, the analysis on the conversion factor between enegy and peak periods Cep (Te/Tp) has illustrated that the value of 0.8329 at Suao Harbor is smaller than that of 0.8992 at Keelung Habor. The decompositions of temporal wave data by HHT have demonstrated the summarized energy density of the primary and first higher-frequency components during winter seasoons coud constitute up to 93.1% of total energy density. Finally, by taking wave energy conversion rate to be represented by the total energy flux difference between up and down-stream measured waves, it is preliminarily found that the rate is exponentially decreasing with higher energy flux.
|Appears in Collections:||[河海工程學系] 博碩士論文|
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