| Summary: | 碩士 === 國立臺灣海洋大學 === 河海工程學系 === 99 === 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.
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