• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.262-267
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• 2008

The long-term wind data are reconstructed from the short-term meteorological data to design the 4 MW offshore wind park which will be constructed at Woljeong-ri, Jeju island, Korea. Using two MCP (Measure-Correlate-Predict) models, the relative deviation of wind speed and direction from two neighboring reference weather stations can be regressed at each azimuth sector. The validation of the present method is checked about linear and matrix MCP models for the sets of measured data, and the characteristic wind turbulence is estimated from the ninety-percent percentile of standard deviation in the probability distribution. Using the Gumbel's model, the extreme wind speed of fifty-year return period is predicted by the reconstructed long-term data. The predicted results of this analysis concerning turbulence intensity and extreme wind speed are used for the calculation of fatigue life and extreme load in the design procedure of wind turbine structures at offshore wind farms.

• Journal of Power Electronics
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• v.13 no.5
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• pp.737-745
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• 2013

Offshore wind farms are rapidly growing owing to their comparatively more stable wind conditions than onshore and land-based wind farms. The power capacity of offshore wind turbines has been increased to 5MW in order to capture a larger amount of wind energy, which results in an increase of each component's size. Furthermore, the weight of the marine turbine components installed in the nacelle directly influences the total mechanical design, as well as the operation and maintenance (O&M) costs. A reduction in the weight of the nacelle allows for cost-effective tower and foundation structures. On the other hand, longer transmission distances from an offshore wind turbine to the load leads to higher energy losses. In this regard, DC transmission is more useful than AC transmission in terms of efficiency because no reactive power is generated/consumed by DC transmission cables. This paper describes some of the challenges and difficulties faced in designing high-power-density power conversion systems (HPDPCSs) for offshore wind turbines. A new approach for high gain/high voltage systems is introduced using transformerless power conversion technologies. Finally, the proposed converter is evaluated in terms of step-up conversion ratio, device number, modulation, and costs.

• Wind and Structures
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• v.2 no.1
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• pp.1-23
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• 1999

Wind effects are critical considerations in the design of topside structures, overall structural systems, or both, depending on the water depth and type of offshore platform. The reliable design of these facilities for oil fields in regions of hostile environment can only be assured through better understanding of the environmental load effects and enhanced response prediction capabilities. This paper summarizes the analysis and performance of offshore platforms under extreme wind loads, including the quantification of wind load effects with focus on wind field characteristics, steady and unsteady loads, gust loading factors, application of wind tunnel tests, and the provisions of the American Petroleum Institute Recommended Practice 2A - Working Stress Design (API RP 2A-WSD) for the construction of offshore structures under the action of wind. A survey of the performance of platforms and satellite structures is provided, and failure mechanisms concerning different damage scenarios during Hurricane Andrew are examined. Guidelines and provisions for improving analysis and design of structures are addressed.

• Wind and Structures
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• v.24 no.4
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• pp.333-350
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• 2017

Differing from the fixed-type, the dynamic motion of floating-type offshore wind turbines is very sensitive to wind and wave excitations. Thus, the sensing and monitoring of its motion is important to evaluate the dynamic responses to the external excitation. In this context, a monitoring system for sensing and processing the wind-induced dynamic motion of spar-type floating offshore wind turbine is developed in this study. It is developed by integrating a 1/00 scale model of 2.5MW spar-type floating offshore wind turbine, water basin equipped with the wind generator, sensing and data acquisition systems, real-time CompactRIO controller and monitoring program. The scale model with the upper rotatable blades is installed within the basin by means of three mooring lines, and its translational and rotational motions are detected by 3-axis inclinometer and accelerometers and gyroscope. The detected motion signals are processed using a real-time controller CompactRIO to calculate the acceleration and tilting angle of nacelle and the attitude of floating platform. The developed monitoring system is demonstrated and validated by measuring and evaluating the time histories and trajectories of nacelle and platform motions for three different wind velocities and for eight different fairlead positions.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.273-274
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• 2013

Recently, as offshore wind towers are developed, the size of wind towers have become larger and larger, and offshore wind towers are exposed to various external forces such as wave and current compared with onshore wind towers. Thus, the stability of offshore wind towers is more required than onshore wind towers. In this study, when the wind celerity of 60m/s blows to the cylinder, cone, and stair typed towers, the wind and wave forces on foundation are calculated by p-y relation.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.60-64
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• 2018

As the offshore wind farms increase, interest in the efficient power system configuration of submarine cables is increasing. Currently, transmission system of the offshore wind farm uses almost AC system. High temperature superconducting (HTS) power cable of the high capacity has long been considered as an enabling technology for power transmission. The HTS cable is a feasible way to increase the transmission capacity of electric power and to provide a substantial reduction in transmission losses and a resultant effect of low CO2 emission. The HTS cable reduces its size and laying sectional area in comparison with a conventional XLPE or OF cable. This is an advantage to reduce its construction cost. In this paper, we discuss the economic feasibility of the 22.9 kV HTS power cable and the conventional AC power cables for an offshore wind farm connections. The 22.9 kV HTS power cable cost for the offshore wind farm connections was calculated based on the capital expenditure and operating expense. The economic feasibility of the HTS power cable and the AC power cables were compared for the offshore wind farm connections. In the case of the offshore wind farm with a capacity of 100 MW and a distance of 3 km to the coast, cost of the 22.9 kV HTS power cable for the offshore wind farm connections was higher than 22.9 kV AC power cable and lower than 70 kV AC power transmission cable.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.48-55
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• 2019

With recent rapid increases in the power generation capacity of offshore wind power generators, reliable structural analysis of the large-scale infrastructure needed to install wind power generators at sea is required. Therefore, technology for heavy marine equipment such as barges and excavation equipment is needed. Under submarine conditions, rock drilling technology to install the substructure for offshore wind pile excavation is a very important factor in supporting a wind farm safely under dynamic loads over periods of at least 20 years. After investigating the marine environment and on-site ground excavation for the Saemangeum offshore wind farm, in this study we suggest.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.2
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• pp.47-52
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• 2018

The Korea Offshore Wind Power (KOWP) is planning to construct offshore wind energy farms with an overall rated power of 2.5 GW in the south-western coast of the country until 2019. Various types of support structures for offshore wind turbines have been proposed in the past. Nevertheless, in South Korea, jacket structures have in general, been applied as support structures for offshore wind turbines owing to the many accumulated experiences and know-how regarding this kind of support structure. The choice of offshore structure is mainly influenced by site conditions such as seabed soil type and sea environment during installation. In installing jacket sets on the seabed, the mudmat is necessary to maintain the equilibrium of the jacket without the aid of additional devices. Hence, this study proposes the installation of skirt plates underneath the bottom frame of jackets in order to improve the installation stability of jacket structures under rougher sea conditions. To confirm the effect of skirt plates, installation stability analyses considering overturning, sliding and bearing capacity have been performed. From the results, it is shown that jacket structures with skirt plates can contribute to improving the sliding stability of the structures of new wind power farms, while providing economic benefits.

• Journal of Korea Port Economic Association
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• v.35 no.4
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• pp.85-106
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• 2019

Offshore wind power is a representative renewable energy source and a rapidly growing industry. In Gyeongsangnam-do, offshore wind farms of 461.9MW are being pushed for in the Yokji island and are expected to expand further to over 1GW in the future. Accordingly, ports supporting the storage, assembly, transportation, and installation of offshore wind power equipment are expected to play an important role in the smooth progress of the offshore wind farm development project. Based on previous research and cases in major countries,this study prepared criteria for assessment of ports supporting offshore wind farmsand evaluated ports in Gyeongsangnam-do, which are linked to Yokji island offshore wind farms. The assessment criteria have been subdivided into distance from the offshore wind farm, port entry and exit restrictions, navigational areas, fishery rights factors, additional costs, berth length, depth of berth, size of the port yard, port berth bearing pressure, interference with other cargo, a civil appeal, and relevant industrial aggregation. The ports of Tongyeong, Samcheonpo, Kohyun, Masan, and Jinhae in Gyeongsangnam-do were selected and evaluated. As a result, the port of Tongyoung was superior in terms of distance from the Yokji island offshore wind farm. The ports of Samcheonpo, Masan, and Jinhae were evaluated as excellent in other criteria such as berth length, depth of berth, and so on. This study is expected to be used as a source of basic data for offshore wind power companies and policymakers to select and evaluate the supporting ports of offshore wind farms.

• New & Renewable Energy
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• v.8 no.4
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• pp.3-12
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• 2012

Large offshore wind farms have actively been developed in order to meet the needs for wind energy since the land-based wind farms have almost been fully developed especially in Europe. The key problem for the construction of offshore wind farms may be on the high cost of energy compared to land-based ones. NREL (National Renewable Energy Laboratory) has developed a spreadsheet-based tool to estimate the cost of wind-generated electricity from both land-based and offshore wind turbines. Component formulas for various kinds and scales of wind turbines were made using available field data. In this paper, this NREL estimation model is introduced and applied to the offshore wind turbines now under designing or in production in Korea, and the result is discussed.