• 한국해양환경ㆍ에너지학회지
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• 제16권4호
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• pp.239-247
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• 2013

최근 화석연료의 고갈과 환경오염으로 인하여 해상풍력에너지와 같은 신재생 에너지에 대한 관심이 높아지고 있다. 본 연구에서는 범용 동역학해석 프로그램인 MSC.ADAMS를 이용하여 공력하중 및 전기 발전기 토오크를 결정하기 위한 테브난(Thevenin) 방정식이 고려된 해상풍력발전기의 다물체 동역학 해석 기법을 검토하였다. 해석대상으로 고려한 시스템은 5MW급 해상풍력발전기이며, 3개의 블레이드가 수평축 방향에서 역풍을 받아 전기를 생산하는 수평축 풍력발전 형태이다. 블레이드에 작용하는 공력하중은 블레이드 요소 모멘텀 이론을 기반으로 일반화된 동적 웨이크를 고려할 수 있도록 개발된 AeroDyn 프로그램으로부터 산출하였다. 해상풍력발전기의 주요 연결부에서의 동적하중과 토오크 특성이 실제 현상과 유사하게 산출될 수 있도록 하기 위하여, 다물체 동역학 모델 상에 블레이드와 타워는 실제 구조 특성치를 고려한 유연체 모델링을 적용하였다.

• 해양환경안전학회지
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• 제26권5호
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• pp.551-560
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• 2020

최근 해상풍력발전기 시장은 에너지 수요 증가, 화석 연료 기반 발전에 대한 의존도 감소와 환경 규제로 인해 향후 5년 내에 빠른 성장이 예상된다. 이러한 상황에 따라서 전 세계적으로 풍력 발전을 가속화하고 있으며, 해상풍력으로 진입하려는 시도가 많아지고 있다. 노르웨이 해상 안전 관리처(PSA: Petroleum Safety Authority)는 운영하는 동안 충돌사고에 대한 충돌에너지가 35 MJ을 견딜 수 있는 안전설계 기준을 요구하고 있다. 따라서 본 연구에서는 북해 해상풍력발전기 설치 단지에 투입되는 해상풍력발전기 설치 선박(WTIV)의 레그 (Leg)와 선박충돌 사고에 대하여 발생 가능한 충돌시나리오에 대해서 비선형 소성붕괴 거동 결과를 바탕으로 레그의 충돌강도평가법을 분석하였다. 분석된 결과로 현재 설계된 기존 선박을 기준으로 요구치인 35 MJ을 만족을 위해서는 200 % 이상의 단면계수 증가가 필요하고, 이는 현실적인 레그 설계에서는 불가능한 조건으로 판단됐다. 또한, 합리적인 충돌시나리오를 기반으로 한 충돌에너지 기준의 제정이 필요하다.

• Korean Chemical Engineering Research
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• 제45권5호
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• pp.460-465
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• 2007

엔도설판류(${\alpha}$, ${\beta}$, sulfate)를 UV 및 초음파에너지를 조사하여 분해하였다. 물질의 분해과정은 가스크로마토그래프(GC)와 총유기탄소(TOC)를 분석하여 검토되었다. UV 원으로서 low pressure mercury multilamp(8Wx2)와 초음파발생기를 이용하였으며, 초기농도는 10 mg/L로 하였다. 단일성분에서의 실험결과 엔도설판류(${\alpha}$, ${\beta}$, sulfate)의 UV 광분해도는 순서대로 48.2%, 50.0%, 76.5%였으며, 초음파를 이용한 분해에서는 각각 66.9%, 55.8%, 72.7%였다. 3성분 혼합용액에서는 단일성분용액의 분해효율과 달리 엔도설판-sulfate의 분해속도가 급감하여 가장 낮았고 엔도설판 -${\alpha}$, -${\beta}$들은 두드러진 차이를 보이지 않았다. 혼합용액에서 엔도설판-sulfate의 분해속도 감소로부터 엔도설판-${\alpha}$, -${\beta}$와 엔도설판-sulfate 사이의 낮은 평형상수값을 갖는 가역적 반응을 가정할 수 있었다. TOC 분석자료는 엔도설판류의 무기질화가 약 20%~40% 수준으로 진행되었음을 보여주며, 동시에 두 고도처리법이 라디칼분해반응을 유도하면서 상당한 분율의 중간산물을 생성함을 추정할 수 있었다. 또한 엔도설판류의 분해는 유기물 및 TOC 분석자료에 의거하면 모두 겉보기 1차 속도식과 잘 부합되었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권3호
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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.

• 한국환경과학회지
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• 제27권9호
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• pp.763-770
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• 2018

Bioremediation in situ is heavily dependent on the oxygenic environment which would privide the dwelling microorganism with sufficient oxygen. The situation could be easily resolved with supply of an Oxygen Releasing Compound (ORC). In this paper we prepared that sort of material out of oyster shell powder (mostly calcium carbonate) that prevails every shore areas of the country. We used two different oxidizing methods in the first step of the whole manufacturing process-conventional heating in a furnace and an ultrasound generator to obtain calcium oxide. Then that calcium oxide was further oxidized into calcium peroxide which may release oxygen under a moisturized condition. The oxygen releasing experiments were run to test the performance of our products, and to determine the gas kinetics during the experiments. Interestingly, calcium peroxide derived from ultrasound treatment was much more energy-effective as ORC than that from furnace heating although the heat derived process was better than that of ultrasound in terms of oxygen content and its releasing rate. We also found that most of the data collected from the gas releasing experiments fairly supported an ordinary $1^{st}$ order kinetics to oxygen concentration, which shaped a sharp discharge of oxygen at the very early moment of each test.

• 한국해양공학회지
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• 제29권4호
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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.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 춘계종합학술대회
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• pp.383-387
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• 2001

본 논문은 여러 형태의 해저 침전물인 뻘, 모래, 자갈, 패류 등을 초음파를 이용하여 구별하는 것인데, 이는 해저목표물에 대한 신호패턴 데이터베이스를 구축한 후, 기존 어군탐지기로부터 아날로그 신호를 디지털 신호로 변환하고, 이 신호를 컴퓨터에서 가공하여 정확한 목표물 인식이 가능하도록 하는 판독시스템을 개발하는 것이다. 지금까지 연구한 결과를 바탕으로 많은 실험을 거친 후(수조 및 현장 실험 등) 침전물의 데이터를 정밀 분석하면 해저목표물을 알아낼 수 있다. 수중에서 어종별로 어체에서 반사되는 초음파 특성과, 해저면에서 뻘과 딱딱한 패류 껍질, 모래 자판 등에서 반사되는 초음파 특성 등을 분석한 값을 데이터베이스화하여 저장해 두고, 실제 측정시 해저 목표물로부터 반사 되어오는 값과 비교하여 침전물과 어·패류의 서식 상태 현황을 파악하는데, 이런 어·패류 판독용 초음파 탐지기는 된 연구를 통하여 개발 할 수 있다. 중점적으로 추후 연구해야 할 분야는 초음파의 특성을 더욱더 세밀히 샘플링 하는 것과 초음파가 해저 목표물의 여러 형태에 따라 산란 특성을 가지고 있는데 이들에 대한 문제점을 연구하는 것이다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.699-722
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• 2019

It is difficult to observe the potential risks of lifting or turn-over operations in the early stages before a real operation. Therefore, many dynamic simulations have been designed to predict the risks and to reduce the possibility of accidents. These simulations, however, have usually been performed for predetermined and fixed scenarios, so they do not reflect the real-time control of an operator that is one of the most important influential factors in an operation; additionally, lifting or turn-over operations should be a collaboration involving more than two operators. Therefore, this study presents an integrated method for a collaborative simulation that allows multiple workers to operate together in the virtual world. The proposed method is composed of four components. The first component is a dynamic analysis that is based on multibody-system dynamics. The second component is VR (virtual reality) for the generation of realistic views for the operators. The third component comprises the control devices and the scenario generator to handle the crane in the virtual environment. Lastly, the fourth component is the HLA (high-level architecture)-based integrated simulation interface for the convenient and efficient exchange of the data through the middleware. To show the applicability of the proposed method, it has been applied to a block turn-over simulation for which one floating crane and two crawler cranes were used, and an offshore module installation for which a DCR (dual-crane rig) was used. In conclusion, the execution of the proposed method of this study is successful regarding the above two applications for which multiple workers were involved.

• 한국해양공학회지
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• 제34권6호
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• pp.454-460
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• 2020

In 2019, the Korean government announced the 3rd Basic Plan for Energy, which included expanding the rate of renewable energy generation by 30-40% by 2040. Hence, offshore wind power generation, which is relatively easy to construct in large areas, should be considered. The East Sea coast of Korea is a sea area where the depth reaches 50 m, which is deeper than the west coast, even though it is only 2.5 km away from the coastline. Therefore, for offshore wind power projects on the East Sea coast, a floating offshore wind power should be considered instead of a fixed one. In this study, a response analysis was performed by applying the analytical conditions of IEC61400-3-2 for the design of floating offshore wind power generation systems. In the newly revised IEC61400-3-2 international standard, design load cases to be considered in floating offshore wind power systems are specified. The upper structure applied to the numerical analysis was a 5-MW-class wind generator developed by the National Renewable Energy Laboratory (NREL), and the marine environment conditions required for the analysis were based on the Ulsan Meteorological Buoy data from the Korea Meteorological Administration. The FAST v8 developed by NREL was used in the coupled analysis. From the simulation, the maximum response of the six degrees-of-freedom motion and the maximum load response of the joint part were compared. Additionally, redundancy was verified under abnormal conditions. The results indicate that the platform has a maximum displacement radius of approximately 40 m under an extreme sea state, and when one mooring line is broken, this distance increased to approximately 565 m. In conclusion, redundancy should be verified to determine the design of floating offshore wind farms or the arrangement of mooring systems.

• 대한조선학회논문집
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• 제59권3호
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• pp.183-191
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• 2022

A design method for a propeller type rim-driven axial-flow turbine for a micro-hydropower system is presented. The turbine consists of pre-stator, impeller and post-stator, where the pre-stator plays a role as a guide vane to provide circumferential velocity to the on-coming flow, and the impeller as a rotational power generator by absorbing angular momentum of the flow. BEM(Blade Element Method), which is based on the turbine Euler equation, is employed to design the pre-stator and impeller blades. NACA 66 thickness form and a=0.8 mean camber line, which is widely accepted as a marine propeller blade section, is used for the pre-stator and turbine blade section. A CFD method, derived from the discretization of the RANS equations, is applied for the analysis of the designed turbine system. The design conditions of the turbine is confirmed by the CFD calculation. Turbine characteristic curve is calculated by the CFD method, in order to provide the performance characteristics at off-design operation conditions. The proposed procedures for the design of a propeller type rim-driven axial-flow turbine are established and confirmed by the CFD analysis.