As global energy consumption continues to increase, the negative impact of global warming also grows. Therefore, eco-friendly energy policy is being established all over the world. Korea’s energy consumption problems are further complicated by the country’s high dependence on energy sourced overseas. Korean energy policy is evolving rapidly to address these problems. Korea has begun to phase out nuclear power and is focusing on developing new sources of renewable energy. So there has been substantial interest in the development of ocean energy. Of all ocean energy technologies, tidal current energy is the closest to the commercialization. Especially, the southwestern coast of Korea is the most promising candidate site for the development of tidal current energy owing to the abundant tidal current energy resource. Meanwhile, ocean energy policy is an important factor in determining the development of ocean energy. Thus, this paper presents the overview of the current status of policy and technology for the tidal current energy system in Korea. These policies explained in this paper can provide significant interest and motivation for the use of tidal current energy resources.

Many mathematical models have been proposed to estimate vertical tidal current profiles. However, as previous studies have shown that tidal current energy sites have different characteristics in their vertical tidal current profiles, it is necessary to estimate the profiles from field-measured data for practical purposes. In this study, we measured layered tidal currents over two months using an acoustic Doppler current profiler (ADCP) to analyze the characteristics of vertical tidal current profiles at the Jangjuk Strait, a candidate site for tidal current energy. As a result, the power law parameter $\alpha$ and bed roughness $\beta$ were estimated as 4.51–12.41 and 0.38–0.42, respectively. Additionally, the maximum roughness length representing seabed roughness in the logarithmic profile was estimated as 0.221 m, and the estimated friction velocity was 0.038–0.194 m/s. Furthermore, a high correlation was observed between the depth-averaged tidal current velocity and friction velocities at all sites during flood and ebb tide conditions. A high correlation was also found between the bed roughness, roughness length, and power law exponent at relatively deeper sites. Tidal current energy sites display distinct characteristics compared to other sea areas. Therefore, it is essential to account for field conditions when conducting numerical modeling and design.

Lee, U.-J.; Cho, H.-Y.; Lee, B.W., and Ko, D.-H., 2023. Joint probability distribution of significant wave height and peak wave period using Gaussian copula method. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 96-100. Charlotte (North Carolina), ISSN 0749-0208. In this study, the joint probability distribution was estimated using the significant wave height-peak wave period data observed for 3 years for 3 stations along the coast of Korea, and an environmental contour line drawing was performed. For accurate estimation, an optimal probability distribution model was calculated for each wave parameter, and the Kolmogorov-Smirnov test and Kullback-Leibler divergence were used for the distribution fit test. Using each estimated optimal probability distribution, a Gaussian copula function was applied considering the correlation between the two wave parameters. As a result of the analysis, it was found that the significant wave height was suitable for the ‘Log-normal’ and ‘3-P Weibull’ distributions, and the peak wave period was suitable for the ‘Log-normal’ distribution. Then, as a result of correlation analysis between significant wave height and peak wave period at all points, it was confirmed that there was a significant correlation. As a result of performing environmental contour line drawing through this, observation data exceeding 3-year recall were found to be less than 1.0% of the total data. In addition, the environmental contour line calculated through the Gaussian Copula showed a limit to reproduce the area where no wave exists as a concave tendency appeared.

본 연구에서는 조류발전시스템의 설계근거(design basis) 작성을 위해 2003년부터 2019년까지 장죽수도 인근해역의 장기 파랑 후측 자료를 이용하여 극치파랑조건을 분석하였다. 장기파랑자료의 극치모델로는 Weibull-3 분포형을 사용하였으며, 매개변수 추정법으로는 확률가중모멘트법과 최소자승법을 사용하였다. 또한 극치분포함수의 적합도 검정을 위해 95%의 신뢰수준으로 K-S 검정법(Kolmogorov-Smirnov test)을 사용하였으며, POT(Peaks-Over-Threshold) 기법을 이용하여 재현기간별 설계파고를 산정하였다. 그 결과, 파랑 후측 자료는 Weibull-3 분포형에 잘 접합하는 것으로 나타났으며, 확률가중모멘트법을 이용하여 추정한 극치파고가 최소자승법으로 추정한 극치파고보다 높게 산정되었다. 또한 재현주기별 극치파고에 상응하는 파주기를 산정하기 위해 파고와 파주기에 대한 관계식을 추정하였다.

In this study, a smoothing method was applied to improve the accuracy of peak wave period estimation using water surface elevation data collected from two oceanographic and meteorological observation towers situated on the western coast of the Korean Peninsula. The effectiveness of the smoothing method was validated by assessing the surface elevation variance and total wave energy. Subsequently, we examined the impact of the smoothing application. The results of our analysis revealed a reduction of approximately 27% in comparison to the confidence interval of the initially estimated spectrum upon applying the smoothing method. Furthermore, a slight variation of approximately 1–2 s was observed between the peak wave period calculated from the estimated spectrum and that obtained through the smoothing process. Utilizing statistical methods to determine the optimal smoothing parameter count, we observed an increasing trend as the range of significant wave heights decreased.