• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.3
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• pp.194-202
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• 2016

This study aims to review a topology optimization based on finite element analysis (FEA) for conceptual design of platform in the 10MW class floating type wave-wind hybrid power generation system (WHPGS). Two topology optimization theories, density method (DM) and homogenization design method (HDM) were used to check which one is more effective for a simplified structural design problem prior to the topology optimization of platform of WHPGS. From the results of the simplified design problem, the HDM was applied to the topology optimization of platform of WHPGS. For the conceptual platform design of WHPGS, FEA model was created and then the structural analysis was performed considering offshore environmental loads at installation site. Hydrodynamics analysis was carried out to calculate pressure on platform and tension forces in mooring lines induced from the offshore environmental loads such as design wave and current. Loading conditions for the structural analysis included the analysis results from the hydrodynamic analysis and the weights of WHPGS. Boundary condition was realized using inertia relief method. The topology optimization of WHPGS platform was performed using the HDM, and then the conceptual arrangement of main structural members was suggested. From the results, it was confirmed that the topology optimization might be a useful tool to design the conceptual arrangement of main structural members for a newly developed offshore structure such as the floating type WHPGS.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.3
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• pp.239-245
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• 2017

As a new technical approach, wave energy converter by using vertical motion of water in the multiple water chambers were developed to realize actual wave power generation as eco-environmental renewable energy. And practical use of wave energy converter was actually to require the following conditions: (1) setting up of the relevant device and its application to wave power generation in case that severe wave loading is avoided; (2) workability in installation and maintenance operations; (3) high energy conversion potential; and (4) low cost. In this system, neither the wall(s) of the chambers nor the energy conversion device(s) are exposed to the impulsive load due to water wave. Also since this system is profitable when set along the jetty or along a long floating body, installation and maintenance are done without difficulty and the cost is reduced. In this paper, we describe the system which consists of a float, a shaft connected with another shaft, a rack and pinion arrangement, a ratchet mechanism, and rotary type generator(s). Then, we present the dynamics model for evaluating the output electric power, and the results of numerical calculation including the effect of the phase shift of up/down motion of the water in the array of water chambers aligned along the direction of wave propagation.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.209-215
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• 2017

A large floating offshore wind-wave hybrid power generation system with an area of 150 m2 and four 3 MW class wind turbine generators was installed at each column top. In accordance with the wind turbine arrangement, the wake generated from upstream turbines can adversely affect the power performance and load characteristics of downstream turbines. Therefore, an optimal arrangement design, obtained through a detailed flow analysis focusing on wake interference, is necessary. In this study, to determine the power characteristics and annual energy production (AEP) of individual wind turbines, transient computational fluid dynamics, considering wind velocity variation (8 m/s, 11.7 m/s, 19 m/s, and 25 m/s), was conducted under different platform conditions ($0^{\circ}$, $22.5^{\circ}$, and $45^{\circ}$). The AEP was calculated using a Rayleigh distribution, depending on the wind turbine arrangement. In addition, we suggested an optimal arrangement design to minimize wake losses, based on the AEP.

• Ocean Systems Engineering
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• v.2 no.4
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• pp.297-314
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• 2012

Power-take-off through inner dynamic system inside a floating buoy is suggested. The power take-off system is characterized by mass, stiffness, and damping and generates power through the relative heave motion between the buoy and inner mass (magnet or amateur). A systematic hydrodynamic theory is developed for the suggested WEC and the developed theory is illustrated by a case study. A vertical truncated cylinder is selected as a buoy and the optimal condition of the inner dynamic system for maximum PTO (power take off) through double resonance for the given wave condition is systematically investigated. Through the case study, it is seen that the maximum power can actually be obtained at the optimal spring and damper condition, as predicted by the developed WEC theory. However, the band-width of high performance region is not necessarily the greatest at the optimal (maximum-power-take-off) condition, so it has to be taken into consideration in the actual design of the WEC.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.123-132
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• 2015

In this study, an arrangement design process for multiple wind turbines, placed on the 10MW class floating wave-offshore wind hybrid power generation system, was presented, and the aerodynamic performance was evaluated by using a computational fluid dynamics. An arrangement design, which produces a maximum power in the site wind field, was found by using a commercial program, WindPRO, based on a blade element momentum theory, then the effect of wake interference on the system between multiple wind turbines was studied and evaluated by using ANSYS CFX.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.291-297
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• 2015

The wave spectrum was generated from wave data measured at the Chagwi-do site in Jeju, where a 10MW class floating wave-offshore wind hybrid power generation system will be installed. The latching control technology (Sheng et al.[2015]) was applied in order to improve the extracted power from WEC (Wave Energy Converter), which is heaving in corresponding irregular waves. The peak period as a representative value of irregular waves was used when we determined the latching duration. From the numerical results in the time-domain analysis, the latching control technology can significantly improve the extracted power about 50%.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.508-508
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• 2012

CST microwave studio is used to simulate the plasma profile of the 450mm CCP source. Standing wave effect becomes important at the high frequency as the electrode radius increases. To solve plasma non-uniformity problem, we designed multi electrode chamber to decreasing standing wave effect. Simulation showed the ratio of input power of each electrode is related with electric field strength. The multi electrode was constructed and measured by 2D probe arrays using floating harmonic method. Uniformity of 450 mm CCP was changed by the ratio of input power of each electrode. We described this dependence with circuit model.

• Journal of the Korean Solar Energy Society
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• v.37 no.1
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• pp.1-14
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• 2017

A series of coupled time domain simulations considering stochastic waves and wind based on five 1-h time-domain analyses are performed in normal operating conditions. Power performance and tower base Fore-Aft bending moment and pitching motion response of the floating spar-buoy wind turbine with 2 MW direct-drive PMSG have been analyzed by using HAWC2 that account for aero-hydro-servo-elastic time domain simulations. When the floating spar-buoy wind turbine is tilted in the wind direction, maximum of platform pitching motion is close to $4^{\circ}$. Statistical characteristics of tower base Fore-Aft bending moment of floating spar-buoy wind turbine are compared to that of land-based wind turbine. Maximum of tower base Fore-Aft bending moment of floating spar-buoy wind turbine and land-based wind is 94,448 kNm, 40,560 kNm respectively. This results is due to changes in blade pitch angle resulting from relative motion between wave and movement of the floating spar-buoy wind turbine.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.135-142
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• 2015

Floating offshore structures should be designed by considering the most extreme environmental loadings which may be encountered in their design life. The most severe loading on a wave-offshore wind hybrid power generation system is wave loads. The principal parameters of wave loads are wave length, wave height and wave direction. The wave loads have different effects on the structural behavior characteristic depending on the combination of wave parameters. Therefore, the process of investigation for critical loads based on the individual wave loading parameter is need. Namely, the equivalent design wave should be derived by finding the wave condition which generates the maximum stress in entire wave conditions. Through a series of analysis, an equivalent regular wave height can be obtained which generates the same amount of the hydrodynamic loads as calculated in the response analysis. The aim of this study is the determination of equivalent design wave regarding to characteristic global hydrodynamic responses for wave-offshore wind hybrid power generation system. It will be utilized in the global structural response analysis subjected to selected design waves and this study also includes an application of global structural analysis.

• Ocean Systems Engineering
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• v.3 no.4
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• pp.275-294
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• 2013

Side-by-side offloading operations are widely utilized in engineering practice. The hydrodynamic interactions between two vessels play a crucial role in safe operation. This study focuses on the coupled effects between two floating bodies positioned side-by-side as a shuttle tanker-FPSO (floating production, storage and offloading) system. Several wave directions with different side-by-side distances are studied in order to obtain the variation tendency of the horizontal hydrodynamic coefficients, motion responses and mean drift forces. It is obtained that the coupled hydrodynamics between two vessels is evidently distinguished from the single body case with shielding and exaggerating effects, especially for sway and yaw directions. The resonance frequency and the peak amplitude are closely related with side-by-side separation distance. In addition, the horizontal hydrodynamics of the shuttle tanker is more susceptible to coupled effects in beam waves. It is suggested to expand the gap distance reasonably in order to reduce the coupled drift forces effectively. Attention should also be paid to the second peaks caused by hydrodynamic coupling. Since the horizontal mean drift forces are the most mainly concerned forces to be counteracted in dynamic positioning (DP) system and mooring system, prudent prediction is beneficial in saving consumed power of DP system and reducing tension of mooring lines.