• 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.

• Water for future
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• v.54 no.12
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• pp.84-91
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• 2021

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.470-475
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• 2019

This paper deals with a 30kW grid-connected PCS (Power Conversion System) for an Oscillating Water Column (OWC) wave-power generation system. Wave power generation in marine energy is suitable for Korea with the characteristics of a peninsula with three sides facing the sea. In the case of coastal disasters, wave generators can act as a breakwater to reduce damage, and can be integrated with other marine power generation systems to increase efficiency. Wave power generation systems are classified into various types, such as oscillating bodies, OWC, and overtopping according to the operation principle, and they can also be classified into two types according to the installation method: a fixed structure and floating structure. This paper proposes a 30kW grid-connected PCS topology and model for OWC wave power generation that is structurally stable with a turbine and generator that are relatively easy to maintain, and then provide a control method required for grid connection, including DC link voltage control. Simulation verification was performed to verify the proposed PCS.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.17-18
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• 2014

Wave energy generation system is sorted as oscillating water chamber type, over topping device type and wave activating body type. The wave activating body type converts from wave energy to kinetic of the machine one and the power generation amount increases while the motion of a activating body increases. In this paper the wave energy convertor consists of a main body which has a generation system and the activating body. They are connected by a bar type bridge. The twisting moment and angular velocity at a shaft of convertor are calculated when various condition of the incident wave, a diversity of connection methods between the main body and the activating body. It can be used as basic idea for determining the design of wave activating body type convertor.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.3
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• pp.184-191
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• 2011

Preliminary design of a mooring system for a floating wave energy converter(WEC) is performed. A mooring line is designed to consist of two parts; the one is a chain in heavy weight laid on the seabed and linked to an anchor on the seabed and the other is a light weight chain suspended at a floater. A high weight chain laid on the seabed can contribute to mitigate dynamic energy propagated from top oscillation and decrease anchor weight and volume. Through a low weight chain suspended between a floater and seabed the WEC's function to produce energy from wave can be affected in minimum by the motion of a chain. The static and dynamic analyses for the designed mooring system were carried out to evaluate WEC system's safety. The present study shows that the designed gravity anchor moves horizontally due to the tension exerted on the anchor in the severe ocean environmental condition. The present mooring system should be redesigned to satisfy the safety requirements. The present study will be useful to predict the safety of the mooring system under ocean environment.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.20-25
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• 2001

부유식 파랑에너지 변환시스템(Oscillating Water Column)에서 에너지 변환은 입력파와 챔버, 챔버내 공기의 상호작용으로 이루어진다. 이 논문은 파랑에너지를 기계적 운동으로 변환하는 기계적 특성을 해석한다. 단일 진동수 규칙파가 입력되었을 때에 파에 의하여 챔버의 상하운동이 선형적으로 발생하며, 이 상하운동은 챔버내의 압력 변화에 영향을 받는다. 상하운동과 챔버내로 투과한 파, 그리고 챔버내 압력에 의해 발생되는 파에 의해 챔버내의 상대운동을 정하고, 그 상대운동에 의한 공기의 압축 팽창과 온도상승을 근사적 열역학적 방정식으로 해석하여 오리피스를 통한 유량과 압력을 기준으로 에너지 변환요율을 결정하였다. 얻어진 식은 간단하면서도 관련요소의 영향을 전반적으로 표현한다. 개구율 변화에 따른 운동응답을 비교하였다.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.28-35
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• 2011

In this paper, the wave-induced motion characteristics of a floating pendulor are investigated numerically. A floating pendulor is a movable-body-type wave energy converter. This device consists of three main parts (floater, pendulum, and damping plates). In order to obtain the hydrodynamic coefficients and wave exciting forces acting on floating bodies, a higher-order boundary element method (HOBEM) using a wave Green function is applied to the present problems. The hinged motion of a pendulum is simulated by applying the penalty method. In order to obtain a more realistic motion response for a pendulor, numerical body damping is included. First, the wave force and motion characteristics of just a floater are observed with respect to different shape parameters. Then, a coupled analysis of a floater, pendulum, and damping plates is carried out. The relative pitch velocity and wave forces acting on the floating pendulor are compared with those of a fixed pendulor.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.2
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• pp.129-136
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• 2016

Floating offshore structures keep its position by a mooring system against various kind of environmental loadings. For this reason, a reliable design of the mooring system is a key factor for initial design stage of a floating structure. However, there exists possibility of mooring failure, even the system is designed with enough safety margin, due to the unexpected extreme environmental conditions or long-term fatigue loadings. The breaking of one of the mooring lines may change the tension level of the other mooring lines, which can potentially result in a progressive failure of the entire structure. In this study, time domain numerical simulation of 10MW class wind-wave hybrid platform was carried out with partially broken mooring line. Overall platform responses and variations of the mooring line tension were numerically evaluated.

• Journal of Ocean Engineering and Technology
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• v.30 no.2
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• pp.84-90
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• 2016

In this study, a six degree-of-freedom motion analysis of a wind-wave hybrid platform equipped with numerous wave energy converters (WECs) was carried out. To examine the effect of the WECs on the platform, an analysis of one-way coupling was carried out, which only considered the power take-off (PTO) damping of the static WECs on the platform. The equation of motion of a floating platform with mooring lines in the time domain was established, and the responses of the one-way coupled platform were then compared with the case of a platform without any coupling effects from the WECs. The hydrodynamic coefficients and wave exciting forces were obtained from the 3D diffraction/radiation pre-processor code WAMIT based on the boundary element method. Then, an analysis of the dynamic responses of the floating platform with or without the WEC effect in the time domain was carried out. All of the dynamics of a floating platform with multiple wind turbines were obtained by coupling FAST and CHARM3D in the time domain, which was further extended to include additional coupled dynamics for multiple turbines. The analysis showed that the PTO damping effect on platform motions was negligible, but coupled effects between multiple WECs and the platform may differentiate the heave, roll, and pitch platform motions from the one without any effects induced by WECs.

• Journal of Ocean Engineering and Technology
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• v.27 no.6
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• pp.16-21
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• 2013

In this paper, the mooring system for a floating wave energy farm is designed based on a two-dimensional analysis. The mooring system uses an anchorless mooring line linking two floaters in a floating wave energy farm. The basic equation to determine the length of the mooring line between the two floaters is proposed. The other properties such as the diameter and pretension are taken from the mooring line for a single floater. The dynamic behavior and safety of the designed mooring system under extreme ocean conditions are analyzed with the commercial software Orcaflex. A numerical study shows the stability and high safety in tension of the designed mooring lines for a floating wave energy farm. The proposed anchorless mooring system for a floating wave energy farm results in a considerable reduction in the length of the mooring line, contributing to the economics of a floating wave energy farm.