• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.223-232
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• 2015

The present paper considers the conceptual design of floating wave-offshore wind hybrid power generation system. The worldwide demand for ocean renewable energy is increasing rapidly. Wave and offshore wind energy have been attractive among the various ocean renewable energy sources, and the site to generate electricity from wave and offshore wind accords well together. This means that a hybrid power generation system, which uses wave and offshore wind energy simultaneously has many advantages and several systems have been already developed in Western Europe. A R&D project for a 10 MW class floating wave-offshore wind hybrid power generation system has been also launched in Korea. A semi-submersible platform, which has four vertical columns at each corner of the platform to be connected with horizontal pontoons, was designed for this system considering arrangements of multiple wind turbines and wave energy converters. A mooring system and power cable were also designed based on the metocean data of installation site. In the present paper, those results are presented, and the difficulties and design method in the design of hybrid power generation system are presented.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.180.2-180.2
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• 2010

Simulation technology for dynamic analysis of wind turbine is developed. The Aerodyn and the DAFUL are chosen for aerodynamic analysis and multi-body and flexible body dynamics respectively. Subroutines and variables of Aerodyn developed by NREL are analyzed with hub-height wind data, full field turbulent wind data and Airfoil data. The interface to perform coupled analysis between AeroDyn and DAFUL, GUI for modeling several parts of wind turbines are developed. The program will be extended to analyze the coupled analysis of aerodynamic and hydrodynamic behavior for floating offshore wind turbines.

• Journal of Wind Energy
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• v.14 no.2
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• pp.26-33
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• 2023

In this study, the global response characteristics of floater and mooring for floating offshore wind turbine with a detachable mooring system are performed. Global motion and structural response result extracted from the coupled motion analysis of 10MW DTU floating offshore wind turbine with detachable mooring system modeled by high-order boundary element model and finite element mesh, were used to study the characteristics of tension on mooring lines subjected to three different types of ocean loads. Breaking limit of mooring line characterized by wind, current and wave load has a major effect on the distribution of mooring tension found in time domain analysis. Based on the numerical results of coupled motion analysis, governing equation for calculating the motion response of a floater under ocean loads, and excitation force and surge motion and tension respectively are presented using excursion curve. It is found that the response of floater is reliable and accurate for calculating the tension distributions along the mooring lines under complex loadings. This means that the minimun breaking limit of mooring system satisfied a design criteria at ultimate ocean environmental loading condtions.

• Journal of Wind Energy
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• v.14 no.3
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• pp.5-13
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• 2023

Floating LiDAR systems (FLSs) are used in many countries because they are easier to install than stationary weather towers, have low maintenance costs, and can be installed in deep sea areas. However, FLSs are rarely used in Korea due to a lack of clear evaluation criteria to verify the reliability and uncertainty of their measurements. This study is the first to verify the reliability of FLSs in Korea with one-year simultaneous observation of six lidar systems - two fixed and four floating systems - in sea areas of Gunsan and Yeonggwang. The reliability of FLSs measurement data was verified by comparison between fixed and floating systems. Moreover, differences between existing wind resource maps and the data observed from the six points were analyzed and wind resource maps were calibrated. The results show a return rate of more than 95 % of the observed data and strong correlations between fixed and floating systems (average R2 of 0.977). Additionally, errors in wind speed predictions to produce a wind resource map could be significantly reduced from 5.7 % to 0.6 % after calibrations with the observation data.

• Journal of Wind Energy
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• v.13 no.3
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• pp.72-78
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• 2022

This study performed a numerical analysis on the effect of platform shape and damaged mooring lines on the movement of the semi-submersible floating offshore wind turbines (FOWT). The NREL 5 MW-OC4-DeepCwind semi-submersible wind turbine was selected as the reference model. In order to find the effect of the semi-submersible floating platform shape, the dynamic movement and feasibility of three different models were observed with and without the presence of turbine blades. In addition, extreme conditions were considered by having one of the mooring lines detached to determine the effects on the FOWT. As a result, the remaining mooring lines deviated to change the surge and sway motion, which could cause a collision with nearby marine structures, and the variation of yaw angle might lead to critical accidents such as rollover. Since the response of the floating platform after receiving mooring line damage may vary depending on the mooring pattern, the location of the mooring damage, and the direction of the wind and waves, detailed simulations showed substantial variation of damage patterns.

• Journal of Ocean Engineering and Technology
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• v.32 no.1
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• pp.9-20
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• 2018

The present study deals with the conceptual design of a motion reduction device for a floating wave-offshore wind hybrid power generation platform. A damping plate attached to the bottom of a column of a large semi-submersible is introduced to reduce the motion of the platform. Performance analyses on various shapes and configurations of damping plates were performed using the potential flow solver, and the appropriate configuration and size of the damping plate were selected based on the numerical results. In order to see the effect of viscous damping, a small scale model test was performed in a 2D wave flume. The performances of five different damping plates were measured and discussed based on the results of free decay tests and regular wave tests.

• Journal of the Korea Society of Computer and Information
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• v.26 no.12
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• pp.255-264
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• 2021

In this paper, we propose operations and maintenance (O&M) planning approach for floating offshore wind farm using the mathematical optimization. To be specific, we present a MILP (Mixed Integer Linear Programming that suggests the composition of vessels, technicians, and maintenance works on a weekly basis. We reflect accessibility to wind turbines based on weather data and loss of power generation using the Jensen wake model to identify downtime cost that vary from time to time. This paper also includes a description of two-stage approach for maintenance planning & detailed scheduling and numeric analysis of the number of vessels and technicians on the O&M cost. Finally, the MILP model could be utilized in order to establish the suitable and effective maintenance planning reflecting domestic situation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.848-857
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• 2018

Recently, around the world, active development of new renewable energy sources including solar power, waves, and fuel cells, etc. has taken place. Particularly, floating offshore wind farms have been developed for saving costs through large scale production, using high-quality wind power and minimizing noise damage in the ocean area. The development of floating wind farms requires an evaluation of the Maritime Safety Audit Scheme under the Maritime Safety Act in Korea. Floating wind farms shall be assessed by applying the line and area concept for systematic development, management and utilization of specified sea water. The development of appropriate evaluation methods and standards is also required. In this study, proper standards for marine traffic surveys and assessments were established and a systemic treatment was studied for assessing marine spatial area. First, a marine traffic data collector using AIS or radar was designed to conduct marine traffic surveys. In addition, assessment methods were proposed such as historical tracks, traffic density and marine traffic pattern analysis applying the line and area concept. Marine traffic density can be evaluated by spatial and temporal means, with an adjusted grid-cell scale. Marine traffic pattern analysis was proposed for assessing ship movement patterns for transit or work in sea areas. Finally, conceptual design of a Marine Traffic and Safety Assessment Solution (MaTSAS) was competed that can be analyzed automatically to collect and assess the marine traffic data. It could be possible to minimize inaccurate estimation due to human errors such as data omission or misprints through automated and systematic collection, analysis and retrieval of marine traffic data. This study could provides reliable assessment results, reflecting the line and area concept, according to sea area usage.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.7-17
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• 2016

The present study experimentally considers dynamic performance of large floating wave-offshore hybrid power generation platform in extreme conditions. In order to evaluate the motion performance of the large floating hybrid power generation platform, 1/50 scaled model was manufactured. A mooring line was also manufactured, and free-decay and static pull-out tests were carried out to check the mooring model. A mooring line table was introduced to satisfy the water depth, and environmental conditions were checked. Motion responses in regular waves were measured and complicated environmental conditions including wave, wind, and current were applied to see the dynamic performance in extreme/survival conditions. Maximum motion and acceleration were judged following the design criteria, and maximum offset and mooring tension were also checked based on the rule. The characteristics of hybrid power generation platform are discussed based on these data.

• Journal of Wind Energy
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• v.14 no.1
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• pp.5-13
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• 2023

The commercialization has been of great importance to the clean energy research sector for investing the wind farm development, but it would be difficult to reach a social consensus on the need to expand the economic feasibility of renewable energy due to the lack of reliable and continuous information on levelized cost of Energy (LCOE). Regarding this fact, this paper presents the evaluation of LCOE, focusing on Ulsan offshore region targeting to build the first floating offshore wind farm. Energy production is estimated by the meteorology data combined with the Leanwind Project power curve of an exemplar wind turbine. This work aims to analyze the costs of the Capex depending on site-specific variables. The cost of final LCOE was estimated by using Monte-Carlo method, and it became an average range 297,090 KRW/MWh, a minimum of 251,080 KRW/MWh, and a maximum of 341,910 KRW/MWh. In the year 2021, the SMP (system marginal price) and 4.5 REC (renewable energy certificate) can be paid if 1 MWh of electricity is generated by renewable energy. Considering current SMP and REC price, the floating platform industry, which can earn around 502,000 KRW/MWh, can be finally estimated highly competitive in the Korean market.