This paper deals with the resonant type of wave energy converter (WEC) and the determination method of its geometric parameters, which were obtained to construct a robust and optimal structure. The optimization problem is formulated with the objectives of simultaneously maximizing the absorbed power output, which is mainly related to optimal power take-off damping, and minimizing the production cost by the volume of the required sheet plate using a weighting method. The constraints are composed of the response surfaces that indicate the resonance period (heave, pitch) and the meta-center height of the buoy. The signal-to-noise ratio calculated from the normalized multi-objective results with the weight factor can be used to help select the robust design level. In order to obtain a sample data set, the motion responses of the power buoy were analyzed using a commercial code based on the boundary element method. We present the Pareto-optimal set to reveal the relationship between the power and the volume of a sheet plate. Lastly, the power efficiency of the WEC with the optimum design variables is estimated as the captured wave ratio resulting from the absorbed power. The result of the WEC design is economically optimal and satisfies given constraints.

Multi-objective Optimum Design of a Buoy for the Resonant-type Wave Energy Converter

Response of wave energy to tidal currents in the western sea of Jeju Island, Korea

Wave data acquired over seven years near Daejin Harbor located in the north central area of the east coast was analyzed using spectral method and wave-by-wave analysis method and its major wave characteristics were examined. Significant wave heights were found to be high in winter and low in summer, and peak periods were also found to be long in winter and short in summer. The maximum significant wave height observed was 6.59 m and was caused by Typhoon No. 1216, SANBA. The distributional pattern of the significant wave heights and peak periods were both reproduced better by Kernel distribution function than by Generalized Gamma distribution function and Generalized Extreme Value distribution function. Meanwhile, the wave data was subdivided by month and wave height level and the cumulative appearance rate was proposed to aid designing and constructing works in nearby coastal areas.

Analysis of the Long-term Wave Characteristics off the Coast of Daejin

In this study, laboratory experiments and numerical simulations were conducted to test the performance of resonance power buoy system proposed by Kweon et al.(2010). The system is composed of a linear generator and a mooring buoy. The mover of the linear generator mainly has heave motion driven by vertical oscillation of the buoy. In this system, the velocity discrepancy between the mover and the buoy makes electricity. However, ocean wave energy as a natural resource around Korean peninsula is comparatively small and the driving force for producing electricity is not enough for commercialization. Therefore, it is necessary that the buoy motion be amplified by using resonance characteristics. In order to verify the resonance effects on the test power buoy, the experimental investigations were conducted in the large wave flume (length of 110 m, width of 8 m, maximum depth of 6 m) equipped with regular and random plunger wave generator. The resonance draft of test power buoy is designed for the corresponding period of incident wave, 1.96 sec. Regular wave test results show that the heave response amplitude operator(RAO) by a test buoy has the amplification of 5.66 times higher compared to the wave amplitude at the resonance period. Test results of random waves show that the buoy has the largest spectrum area of 20.73 times higher at the point of not the resonance period but the shorter one of 1.85 sec. Therefore this study suggests the resonance power buoy for wave power generation for commercial application in the case of the coastal and oceanic area with smaller wave energy.

https://www.koreascience.or.kr:443/article/JAKO201312855324615.pdf

Experimental Study for the Resonance Effect of the Power Buoy Amplitude

Wave data acquired over eleven years near Sokcho Harbor located in the central area of the east coast were analyzed using spectral method and wave-by-wave analysis method and its major wave characteristics were examined. Significant wave heights were found to be high in winter and low in summer, and peak periods were also found to be long in winter and short in summer. The maximum significant wave height observed was 8.95 m caused by the East Sea twister. The distributional pattern of the significant wave heights and peak periods were both fitted better by Kernel distribution function than by Generalized Gamma distribution function and Generalized Extreme Value distribution function. The wave data were compiled to subdivide the wave height into intervals for each month, and the cumulative occurrence rates of wave heights were calculated to be utilized for the design and construction works in nearby construction works.

/pdf/long-term-wave-monitoring-and-analysis-off-the-coast-of-h19mhu2auj.pdf

Long-term Wave Monitoring and Analysis Off the Coast of Sokcho

Wave energy distribution along the Korean coastal sea area was analysed based on the calculated wave data at KORDI. The wave data for the analysis is for the last 24 years (1979∼2002) and the model is HYPA and WAM using known wind field. The wave energy or wave power was evaluated based on the linear wave theory with a simple wave period assumption. The results shed some idea on the amount of usable wave energy and the sites of higher efficiency. It is fair to say that 3kw/m wave energy is easily observable and 10kw/m is frequently available depending on the season and location. The south west region of Jeju island is believed to have the highest overall wave energy density.

Hong Keyyong

Papers

Analysis of Wave Energy Density for Korean Coastal Sea Area Based on Long-Term Simulated Wave Data