• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.4
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• pp.239-247
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• 2013

Recently renewable energy such as offshore wind energy takes a higher interest due to the depletion of fossil fuel and the environmental pollution. This paper deals with multi-body dynamics (MBD) analysis technique for offshore wind turbine system considering aerodynamic loads and Thevenin equation used for determination of electric generator torque. Dynamic responses of 5MW offshore wind turbine system are evaluated via the MBD analysis, and the system is the horizontal axis wind turbine (HAWT) which generates electricity from the three blades horizontally installed at upwind direction. The aerodynamic loads acting on the blades are computed by AeroDyn code, which is capable of accommodating a generalized dynamic wake using blade element momentum (BEM) theory. In order that the characteristics of dynamic loads and torques on the main joint parts of offshore wind turbine system are simulated similarly such an actual system, flexible body modeling including the actual structural properties are applied for both blade and tower in the multi-body dynamics model.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.281-294
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• 2015

In order to quantitatively estimate the nonlinear destructive interaction of wave load with wind load, which is very vital for the optimal design of offshore wind energy converter, we carried out a hydraulic model test and wind tunnel test. As a substructure of offshore wind energy converter, we would deploy the monopile, which is popular due to its easiness in construction. Based on the simulation using Monte Carlo simulation using Kaimal spectrum and cross spectrum, the instantaneous maximum wind velocity is adjusted to 10 m/s. And, considering the wave conditions of the Western Sea where a pilot wind farm is planned to be constructed, $H_s=0.1m$, 0.15 m, 0.2 m is carefully chosen. It turns out that the nonlinear destructive interaction between the wind and wave loads acting on the offshore wind energy converter is more clearly visible at rough seas rather than at mild seas, which strongly support our deduction that a Large eddy, a swirling vortex developed near the bumpy water surface in the opposite direction of the wind, is the driving mechanism underlying nonlinear destructive interaction between the wind and wave loads.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.551-560
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• 2020

Recently, the offshore wind power generator market is expected to grow significantly because of increased energy demand, reduced dependence on fossil fuel-based power generation, and environmental regulations. Consequently, wind power generation is increasing worldwide, and several attempts have been made to utilize offshore wind power. Norway's Petroleum Safety Authority (PSA) requires a leg-structure design with a collision energy of 35 MJ owing to the event of a collision under operation conditions. In this study, the results of the numerical analysis of a wind turbine installation vessel subjected to ship collision were set such that the maximum collision energy that the leg could sustain was calculated and compared with the PSA requirements. The current leg design plan does not satisfy the required value of 35 MJ, and it is necessary to increase the section modulus by more than 200 % to satisfy the regulations, which is unfeasible in realistic leg design. Therefore, a collision energy standard based on a reasonable collision scenario should be established.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.4
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• pp.191-199
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• 2018

In this paper, wind data at 20 locations are collected and analyzed in order to review optimal candidate site for offshore wind farm around Korean marginal seas. Observed wind data is fitted to Rayleigh and Weibull distribution and annual energy production is estimated according to wind frequency. As the model of wind turbine generator, seven kinds of output of 1.5~5 MW were selected and their performance curves were used. As a result, Repower-5 MW turbines showed high energy production at wind speeds of 7.15 m/s or higher, but G128-4.5 MW turbines were found to be favorable at lower wind speeds. In the case of Marado, Geojedo and Pohang, where the rate of occurrence of wind speeds over 10 m/s was high, the capacity factor of REpower's 5 MW offshore wind turbine was 56.49%, 50.92% and 50.08%, respectively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.658-665
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• 2019

Among the renewable energy resources, wind power is growing rapidly in terms of technological development and market share. Recently, onshore wind farm have been affected by limitations of terrestrial space and environmental problems. Consequently, installation sites have been moved to the sea, and the development of floating offshore wind farms that are installed at deep waters with more abundant wind conditions is actively underway. In the context of maritime traffic, the optimal site of offshore wind farms is required to minimize the interference between ships and wind turbines and to reduce the probability of accidents. In this study, genetic algorithm based AIS(Automatic Indentification System) data composed of genes and chromosomes has been used. The optimal site of floating offshore wind farm was selected by using 80 genes and by evaluating the fitness of genetic algorithm. Further, the final site was selected by aggregating the seasonal optimal site. During analysis, 11 optimal site were found, and it was verified that the final site selected usng the genetic algorithm was viable from the perspective of maritime traffic.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.365-373
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• 2008

When the wind power system is planned to construct, it is important to understand the physical, chemical and mechanical properties of sediment. Especially, If it is the seabed unconsolidated sediment, we need to experiment on sediment through seabed unconsolidated sediment test and sediment survey. Because the sediment's properties are different as its formation, accumulation and load, unconsolidated sediment is difficult to be expected to its behavior. So we can estimate suitability for mechanical material and decrease the uncertainty through seabed unconsolidated sediment test. Seabed unconsolidated sediment test can be experimented in laboratory or in-situ as purpose, in-situ condition, economic problem. In this study, we sampled the seabed unconsolidated sediment at offshore around Korea Maritime University and measured properties of sediment through the laboratory test, showed the effect on physical properties of seabed unconsolidated sediment when the wind power system is planned to construction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.118-125
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• 2019

In this study, the vibration characteristics and the resonance phenomena of a wind-solar hybrid light pole structure are compared with respect to the wind turbine type through the dynamic response measurement. Two different turbines are considered including 2-bladed and 3-bladed vertical axis wind turbine rotors. The resonance phenomenon that can occur in hybrid light pole structure is analyzed by comparing the dynamic characteristics of the structure and the excitation force under operational conditions. Displacement responses are also estimated using the acceleration measurement data by use of recently proposed method, and it is observed that the amplitude of dynamic displacement responses are in the range of 4-6 cm under the resonance in the case of 2-bladed turbine and those are limited under 2 mm in the case of 3-bladed turbine because there is no resonance.

• Journal of Wind Energy
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• v.2 no.2
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• pp.30-37
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• 2011

A floating wind turbine dynamic simulation program, WindHydro, is newly developed taking into account wind inflow and incident wave. WindHydro consists of 5 modules, HDFloat for hydrodynamics, HDProp for hydrodynamic property calculation, HDMoor for mooring dynamics, AeroDyn for aerodynamics, DAFUL for multi-body dynamics with nonlinear elasticity, and interface program that connects each calculation module. A turbulent wind and regular wave load case is simulated for the 5-MW OC3-Hywind with a spar bouy platform and catenary mooring lines. The results are compared with the results of the FAST(developed by NREL). As a result, the overall system responses from WindHydro and FAST agree well although some differences in the generator responses are observed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.244-253
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• 2022

Recently, installation projects of structures such as offshore wind farms have been increasing, and the installation of such marine obstacles could affect ships that pass nearby. Therefore, the purpose of this study was to quantitatively evaluate the risk posed to passing ships due to obstacles in their passage. Hence, parameters that affected the risk were selected, and scenarios were set based on the parameters. The scenarios were evaluated through the ES model, which is a risk assessment model, and we confirmed that the risk ratio increased as the size of the obstacle increased, the safe distance from the obstacle increased, the speed of ship decreased, and the traffic volume increased. Additionally, we found that when the traffic flow direction was designated, the risk ratio was lower than that of general traffic flow. In this study, we proposed a generalization model based on the results of the performed scenarios, applied it to the Dadaepo offshore wind farm, and demonstrated that the estimation of the approximate risk ratio was possible through the generalization model. Finally, we judged that the generalization model proposed in this study could be used as a preliminary reference for the installation of marine obstacles.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.394-401
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• 2021

The construction of new renewable energy facilities is steadily increasing every year. In particular, the offshore wind farm market, which has abundant development scalability and a high production coefficient, is growing rapidly. The southwest sea has the highest possible offshore wind power potential, and related projects are to be promoted. This study presents a basic design procedure by the EUROCODE and considers structural safety in the development of an effective of shore wind foundation in the clay layer. In a previous study, the wind power generator of 5MW class was the main target, but the 8MW of wind turbine generator, which meets the technical trend of the wind turbine market in the Southwest sea, was selected as the standard model. Furthermore, a foundation that fulfills the geological conditions of the Southwest sea was developed. The structural safety of this foundation was verified using finite element method. Moreover, structural safety was secured by proper reinforcement from the initial design. Based on the results of this study, structural safety check for various types of foundations is possible in the future. Additionally, specialized structural design and evaluation guidance were also established.