• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.254-262
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• 2015

Parametric study on submerged body shape of an oscillating hemisphere point absorber was conducted to predict the optimal relation between radius and draft of the body. As an additional damping due to power takeoff system, the optimal damping same as wave radiation damping was applied to the PTO system to produce the maximum wave power. Body response spectrum and power spectrum were obtained for various peak frequencies on wave spectra. It was found that the maximum power can be generated when the peak frequency of available wave power was 20% greater than that of wave spectrum.

• 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.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.483-486
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• 2005

국내에서 대체에너지 공급 비율을 보면 청정에너지로 분류할 수 있는 태양열에너지, 태양광 에너지, 풍력에너지를 모두 합하여 대체에너지의 10% 이하이며, 대체에너지 비율의 90% 이상을 폐기물로부터 얻은 에너지가 차지하고 있는 실정이다. 신재생에너지원에는 여러 종류가 있지만 해양에너지원에 대해 대상을 설정하고 이에 대한 부존량을 살펴보면 진도 주변의 해역에서 조류발전 부존량이 약 362만 kW가 되며, 시화호와 새만금 등지에서의 조력발전 부존량이 650만 kW, 동해안 후포 연안을 비롯한 파력발전 부존량이 20만 kW가 되는 것으로 알려져 있다. 이에 따라 해양에너지를 실용화하기 위한 연구가 국내외에서 연구되고 있다. 본 논문은 권선형유도발전기를 갖는 조류발전 시스템을 대상으로 연구한 결과로 권선형유도발전기를 제어하기 위한 전력변환장치 개발과 관련한 내용이다. 신재생에너지원이 발전 단가 측면에서 경제성을 갖기 위해서 발전기 용량은 5MW 급까지 대용량화 되어 있는 단계이지만 국내에서는 아직 MW급 이상이 되는 권선형유도발전기와 권선형유도발전기를 제어하는 전력변환장치에 대한 연구 실적이 없는 상황이다. 이에 본 논문에서는 IMW급의 권선형유도발전기에 대한 개발 사례를 소개하면서 유효전력제어, 역률제어 특성과 운전 속도에 따라 변동되는 회전자 측에서의 피상전력 제어 특성에 대해 고찰하고자 한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.992-1001
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• 2023

OWEC (Overtopping Wave Energy Converter) is a wave power generation system using the wave overtopping. The performance and safety of the OWEC are affected by wave characteristics, such as wave height, period. To mitigate this issue, optimal OWEC designs based on wave characteristics must be investigated. In this study, the environmental conditions along the Ulleungdo coast were used. The hydraulic efficiency of the OWEC was calculated using SPH (Smoothed Particle Hydrodynamics) by comparing 4 models that changed the substructure. As a result, it was possible to change the substructure. Through design optimization, a new truss-type structure, which is a substructure capable of carrying the design load, was proposed. Through a case study using member diameter and thickness as design variables, structural safety was secured under allowable stress conditions. Considering wave load, the natural frequency of the proposed structure was compared with the wave period of the relevant sea area. Harmonic response analysis was performed using wave with a 1-year return period as the load. The proposed substructure had a reduced response magnitude at the same exciting force, and achieved weight reduction of more than 32%.

• Journal of Ocean Engineering and Technology
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• v.29 no.4
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• pp.317-321
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• 2015

Many kinds of generation systems have been developed to use ocean energy. Among these, with the use of an oscillating water column (OWC) for power generation is attracting attention. The OWC-type wave power generation system converts wave energy into electricity by operating a generator turbine with the oscillating water level in a column of water. There are two ways to convert wave power into electricity using an OWC. One uses a cross-flow turbine using the water level inside the OWC. The other method uses the flow of air in a Wells turbine, which depends on the water level. An experiment was carried out using a 2-D wave tank in order to minimize the number of empirical tests. The design factors were taken from Koo et al. (2012) and the experimental environment assumed by free surface motion. This paper deals with characteristics of two types of wave energy conversion systems combine with a breakwater. One model uses an air-driven Wells turbine and a cross-flow water turbine. The other type uses a cross-flow water turbine. Wave energy converters with OWCs have mostly been studied using air-driven Wells turbines. The efficiency of the cross-flow turbine was about 15% higher than that of the other model, and the water level of the OWC internal chamber for the cross-flow water turbine and air-driven Wells turbine was less than about 40% lower than the one using only the cross-flow water turbine.

• 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.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.11a
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• pp.219-220
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• 2022

최근 항로표지는 기본 업무를 위한 등명기의 구동과 해상 환경 정보 수집 및 데이터 전송 기능들의 확장을 통해 다양한 임무를 수행하기 위한 스마트 장비로써 진화하고 있다. 그래서 항로표지를 운영하기 위한 전력량의 요구가 높아지고 있고, 동작 구동 시간을 확보하기 위해 다양한 해상 에너지원을 통해 발전하는 시스템을 고려하고 있다. 하지만 전원 공급 및 교체가 쉽지 않은 해상 환경에서 태양광, 파력 등의 한정적인 에너지원의 활용은 지속적인 스마트 항로표지의 동작에 한계가 존재한다. 그래서 해양 환경 상황에서도 한정된 에너지원을 활용하여 에너지 수집을 하고 이를 활용하여 다양한 환경 센싱, 정보 연산, 데이터 처리, 무선 정보 전송 등의 시스템에 안정적으로 전력을 공급할 수 있는 방안이 필요하다. 본 논문에서는 해상 환경 적응 에너지 수집, 백업 전력운영, 항로표지 출력 에너지 재사용, 분산 전력관리 등을 포함한 차세대 스마트 항로표지 전원 시스템 구성 방안에 대해서 제안한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.50-51
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• 2012

The final purpose of this study is to develop a hybrid ocean power generation system which has innovate and very high efficiency performance, and which can be operated on both emergency and normal conditions. So, A survey on the electricity power consumption of residential areas at island on south coast.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.136-137
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• 2011

The final purpose of this study is to develop a hybrid ocean power generation system which has innovate and very high efficiency performance, and which can be operated on both emergency and normal conditions. So, A survey on the electricity power consumption of residential areas at island on south coast.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.4
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• pp.552-558
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• 2011

A 50 kW class rotating body type wave energy converter consisted of two floating bodies and a PTO (Power Takeoff) unit is studied. As an wave energy extractor, the body is designed to have a VLCO (Variable Liquid-Column Oscillator) having a liquid filled U-tube with air chambers. Owing to the oscillation of the liquid in the U-tube caused by the air spring effect of the air chambers, the amplitude of response of the VLCO becomes significantly amplified for a target wave period. The PTO converts the rotational moment introduced from the relative motion of the hinged bodies to an hydraulic power by means of a cylinder. A high pressure accumulator, hydraulic motor and a generator are equipped in the PTO to convert the hydraulic power to electric power. A control law for adjusting the oscillation period of the VLCO is proposed for the efficient operation of the VLCO with various wave conditions. It is found that the effect of the air spring has an important role to play in making the oscillation of the VLCO match with the ocean wave. In this way, the wave energy converter equipped with the VLCO provides the most effective mode for extracting energy from the ocean wave.