• Journal of the Korean Geotechnical Society
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• v.40 no.4
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• pp.33-47
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• 2024

Offshore wind structures are subject to long-term repeated horizontal loads from wind, waves, and currents, making it essential to consider these loads in the design of offshore foundations. In this respect, monopiles are large-diameter hollow steel pipes that are relatively simple to construct compared with piles used on onshore sites. They can provide stable support for wind structures and have well-established design codes, leading to their widespread use globally. The behavior of monopiles under lateral static loads is typically assessed using the p-y method proposed by the American Petroleum Institute (API). However, the applicability of p-y curves to large-diameter monopiles exposed to repeated cyclic horizontal loads, such as those experienced in offshore wind applications, must yet be evaluated. Thus, this study evaluated the behavior of monopiles under two-way cyclic horizontal loads in loose silty sand, a representative soil type of the southwestern coast of Korea, using centrifuge model tests. The results demostrated that the behavior of monopiles varied depending on the loading level, number of cycles, and direction of the cyclic loads. Furthermore, the p-y curve method proposed by the API overestimated the behavior of a large-diameter monopile installed in silty sand under two-way cyclic loads.

• Journal of the Korean Solar Energy Society
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• v.35 no.3
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• pp.1-8
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• 2015

The MERRA reanalysis data provided online by NASA was applied to predict the monthly energy productions of Donghai Bridge Offshore wind farms in China. WindPRO and WindSim that are commercial software for wind farm design and energy prediction were used. For topography and roughness map, the contour line data from SRTM combined with roughness information were made and used. Predictions were made for 11 months from July, 2010 to May, 2011, and the results were compared with the actual electricity energy production presented in the CDM(Clean Development Mechanism)monitoring report of the wind farm. The results from the prediction programs were close to the actual electricity energy productions and the errors were within 4%.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.141-143
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• 2018

세계적으로 해양자원의 개발, 해양과학자료 조사 등 다양한 목적으로 해양구조물은 증가되고 있다. 해양구조물의 안전과 선박의 충돌을 방지하기 위하여 IALA, IMO등 국제기구에서는 해양구조믈에 등부표, 등대, 전기폰, 레이콘 등 해양안전유도장비의 설치를 권고하고 있다. 해양안전유도 장비의 설치 목적을 달성하기 위하여는 안정된 전기 에너지의 공급이 필요하다. 고립된 해상에서의 전력을 공급하기 위하여는 태양광, 풍력 등 신재생에너지를 사용하여 전력을 생산할 때, 그간 에너지원으로 사용하지 않던 일정 전압 이하의 에너지를 최대한 충전 가능전압으로 승압하는 에너지 수확(Energy Harvest)형 충방전조절기 개발 기술을 연구하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.2
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• pp.265-278
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• 2022

The global energy paradigm is rapidly changing by centering on carbon neutrality, and wind energy is positioning itself as a leader in renewable energy-based power sources. The success of onshore and offshore wind energy projects focuses on securing the economic feasibility of the project, which depends on securing high-quality wind resources and optimal arrangement of wind turbines. In the process of constructing the wind farm, the optimal arrangement method of wind turbines considering the main wind direction is important, and this is related to minimizing the wake effect caused by the fluid passing through the structure located on the windward side. The accuracy of the predictability of the wake effect is determined by the wake model and modeling technique that can properly simulate it. Therefore, in this paper, using WindSim, a commercial CFD model, the wake diffusion pattern is analyzed through the sensitivity study of each wake model of the proposed onshore wind farm located in the mountainous complex terrain in South Korea, and it is intended to be used as basic research data for wind energy projects in complex terrain in the future.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.357-359
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• 2014

해상에서 선박의 안전한 항행을 위하여 항로표지를 운영하고 있으며, 항로표지는 형상표지, 광파표지, 음파표지, 전파표지, 특수신호표지로 구분할 수 있다. 전자기술의 발전과 안전한 항해에 도움을 주는 각종 시스템들이 등부표에 설치되고 있다. 이에 따라 등부표에서의 전력 수요는 과거보다 훨씬 더 많이 요구되고 있는 실정이다. 정부지원 연구과제로 등부표에서 태양광발전, 풍력발전 및 파력발전이 가능한 등부표용 발전시스템을 개발하였으며, 해상에 설치한 등부표에서 각종 에너지원으로 전력의 생산과 등부표 시스템의 운영에 따른 소비에 대한 분석이 필요하다. 현재 해상실험을 진행하고 있으며, TRS기반의 등부표용 통신시스템과 데이터 수신용 모니터링시스템을 설치하였고, 등부표내에서도 메모리카드를 이용하여 전력의 생산과 소비에 관련된 데이터 저장할 수 있게 구성하였다. TRS기반 모니터링시스템에서 저장된 데이터와 등부표에 설치한 메모리카드에 저장된 데이터 분석을 통하여 등부표용 하이브리드 발전시스템의 전력상태를 분석하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.615-621
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• 2007

Wind power generation is one of the promising gateways that will solve the energy crisis in the future. The wind power generator studied so far is limited to static interpretation in the areas related to tower. This study broadly sets the form of tower as tubular and jacket, identifies the characteristics of each and aims to find and apply their trend to in actual design and manufacturing process. This paper identified the resonance frequency of tower at each mode and studied their features. Furthermore, this study identified the characteristics of the load that occurs in operation and the effect of additional mass incurring when installed in sea, and it compared the two types of tower and was able to predict their trend.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1162-1164
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• 2015

본 논문에서는 태양광, 해상풍력 등 신재생 에너지 증가에 따른 HVDC Grid의 가능성을 소개하고, HVDC Grid에서 HVDC 차단기의 필요성을 언급하며, 유럽 선진사의 개발동향과 차단방식에 따른 비교 및 당사의 연구개발 진행상황을 간략히 소개하고자 한다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.189.2-189.2
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• 2010

The purpose of this study is fatigue damage assessment for large sized casting parts (hub and mainframe) of the 3MW offshore wind turbine by computer simulation. Hub and mainframe durability assessment is necessary because wind turbine have to guarantee for 20 years. Fatigue life evaluation must be considered all of fatigue load conditions as the components are wind load transmission path. Palmgren-Miner linear damage accumulation hypothesis is applied for fatigue life estimation with stress-life approach. S-N curve for the spheroid graphite cast iron EN-GJS-400-18-LT is derived according to durability guidelines. Reduction factors were applied for survival probability, surface roughness, material quality and partial safety factor according to Germanischer Lloyd rules. To calculate fatigue damage, stress tensors, extracted from the unity load calculation from ANSYS is multiplied with time track of fatigue loads extracted from GH bladed. Damage accumulation is performed with all of fatigue load conditions at each finite element nodes. In this study maximum nodal damage value is under 1.0. casted parts are safe. This research was financially supported by the Ministry of Knowledge Economy(MKE), Korea Institute for Advancement of Technology(KIAT) and Honam Leading Industry Office through the Leading Industry Development for Economic Region.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.62.1-62.1
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• 2011

The wind can be stronger and steadier further from shore, but water depth is also deeper. Then bottom-mounted towers are not feasible, and floating turbines are more competitive. There are additional motions in an offshore floating wind turbine, which results in a more complex aerodynamics operating environment for the turbine rotor. Many aerodynamic analysis methods rely on blade element momentum theory to investigate aerodynamic load, which are not valid in vortex ring state that occurs in floating wind turbine operations. So, vortex lattice method, which is more physical, was used in this analysis. Floating platform's prescribed positions were calculated in the time domain by using floating system RAO and waves that are simulated using JONSWAP spectrum. The average value of in-plane aerodynamic force increase, but the value of out-of-plane force decrease. The maximum variation aerodynamic force abruptly increases in severe sea state. Especially, as the pitch motion of the barge platform is large, this motion should be avoided to decrease the aerodynamic load variation.

• Journal of the Korean Solar Energy Society
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• v.37 no.2
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• pp.1-11
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• 2017

The investigation on reliability of ERA-Interim reanalysis wind data was conducted using wind data from the five met masts measured at inland and coastal areas, Jeju island. Shinchang, Handong, Udo, Susan and Cheongsoo sites were chosen for the met mast location. ERA-Interim reanalysis data at onshore and offshore twenty points over Jeju Island were analyzed for creating Wind Statistics using WindPRO software. Reliability of ERA-Interim reanalysis wind data was assessed by comparing the statistics from the met mast wind data with those predicted at the interest point using the Wind Statistics. The relative errors were calculated for annual average wind speed and annual energy production. In addition, the trend of the error was analyzed with distance from met mast. As a result, ERA-Interim reanalysis wind data was more suitable for offshore wind resource assessment than onshore.