국내 풍력단지의 풍력터빈 용량밀도와 이격거리 산정

김현구,강용혁,김진영 한국풍력에너지학회 2016 풍력에너지저널 Vol.7 No.2

Wind resource potential is calculated by multiplying an area where a wind farm can be developed by wind turbine capacity density. Therefore, the wind turbine capacity density of wind farms in Korea must be calculated precisely first, in order to accurately calculate wind resource potential in Korea. In the present study, of the 67 total wind farms in Korea, 18 wind farms were selected, all of which had a total installed capacity of 10 MW or higher and had more than 10 wind turbines. Wind turbine coordinates and wind farm areas were determined using Daum Map Skyview, facilitating the calculation of wind turbine capacity density and wind turbine spacing. The mean wind turbine capacity density of wind farms in Korea was calculated at 6.9±2.1 MW/km2, and the mean wind turbine spacing was calculated at 3.5D (D is a rotor diameter). In the future, when wind resource potential is calculated, the above values can be used to provide more realistic wind energy dissemination targets than it was previously possible.

Thrust force and base bending moment acting on a horizontal axis wind turbine with a high tip speed ratio at high yaw angles

Danijel Bosnar,Hrvoje Kozmar,Stanislav Pospíšil,Michael Macháček 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.5

Onshore wind turbines may experience substantially different wind loads depending on their working conditions, i.e. rotation velocity of rotor blades, incoming freestream wind velocity, pitch angle of rotor blades, and yaw angle of the wind-turbine tower. In the present study, aerodynamic loads acting on a horizontal axis wind turbine were accordingly quantified for the high tip speed ratio (TSR) at high yaw angles because these conditions have previously not been adequately addressed. This was analyzed experimentally on a small-scale wind-turbine model in a boundary layer wind tunnel. The wind-tunnel simulation of the neutrally stratified atmospheric boundary layer (ABL) developing above a flat terrain was generated using the Counihan approach. The ABL was simulated to achieve the conditions of a wind-turbine model operating in similar inflow conditions to those of a prototype wind turbine situated in the lower atmosphere, which is another important aspect of the present work. The ABL and wind-turbine simulation length scale factors were the same (S=300) in order to satisfy the Jensen similarity criterion. Aerodynamic loads experienced by the wind-turbine model subjected to the ABL simulation were studied based on the high frequency force balance (HFFB) measurements. Emphasis was put on the thrust force and the bending moment because these two load components have previously proven to be dominant compared to other load components. The results indicate several important findings. The loads were substantially higher for TSR=10 compared to TSR=5.6. In these conditions, a considerable load reduction was achieved by pitching the rotor blades. For the blade pitch angle at 90o, the loads were ten times lower than the loads of the rotating wind-turbine model. For the blade pitch angle at 12o, the loads were at 50% of the rotating wind-turbine model. The loads were reduced by up to 40% through the yawing of the wind-turbine model, which was observed both for the rotating and the parked wind-turbine model.

Wind-lens turbine design for low wind speed

Mohamed M. Takeyeldein,I.S. Ishak,Tholudin M. Lazim 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.3

This research proposes a wind-lens turbine design that can startup and operate at a low wind speed (< 5m/s). The performance of the wind-lens turbine was investigated using CFD and wind tunnel testing. The wind-lens turbine consists of a 3- bladed horizontal axis wind turbine with a diameter of 0.6m and a diffuser-shaped shroud that uses the suction side of the thin airfoil SD2030 as a cross-section profile. The performance of the 3-bladed wind-lens turbine was then compared to the twobladed rotor configuration while keeping the blade geometry the same. The 3-bladed wind-lens turbine successfully startup at 1m/s and produced a torque of 66% higher than the bare turbine, while the two-bladed wind-lens turbine startup at less than 4m/s and produced a torque of 186 % higher than the two-bladed bare turbine at the design point. Findings testify that adding the wind-lens could improve the bare turbine's performance at low wind speed.

Design and Manufacture of Small-Scale Wind Turbine Simulator to Emulate Torque Response of MW Wind Turbine

임채욱 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.4 No.4

Small-scale wind turbine simulators have been used in laboratories in order to verify power control of real-world large multi-MW wind turbines. The response speed of multi-MW wind turbines is so slow that the response time considerably exceeds several seconds. This fact should be considered in the design of small-scale wind turbine simulators. In this paper, a 3.5 kW wind turbine simulator is designed and manufactured in order to emulate torque response of a 2 MW wind turbine. The small-scale wind turbine simulator consists of a motor, a gear box, a flywheel, and a generator. Two main design parameters are the rotor radius and the mass moment of inertia of the flywheel. The main design objective is to make the 3.5 kW wind turbine simulator have the similar both time constant and wind speed range for optimal TSR (tip speed ratio) to those of the target 2 MW wind turbine. Through numerical simulations and experiments for step response, we demonstrate that the designed and manufactured 3.5 kW wind turbine simulator has the response speed similar to that of the 2MW wind turbine in the aspect of torque response.

Simultaneous out-of-plane and in-plane vibration mitigations of offshore monopile wind turbines by tuned mass dampers

Haoran Zuo,Kaiming Bi,Hong Hao 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.4

To effectively extract the vast wind resource, offshore wind turbines are designed with large rotor and slender tower, which makes them vulnerable to external vibration sources such as wind and wave loads. Substantial research efforts have been devoted to mitigate the unwanted vibrations of offshore wind turbines to ensure their serviceability and safety in the normal working condition. However, most previous studies investigated the vibration control of wind turbines in one direction only, i.e., either the out-of-plane or in-plane direction. In reality, wind turbines inevitably vibrate in both directions when they are subjected to the external excitations. The studies on both the in-plane and out-of-plane vibration control of wind turbines are, however, scarce. In the present study, the NREL 5 MW wind turbine is taken as an example, a detailed three-dimensional (3D) Finite Element (FE) model of the wind turbine is developed in ABAQUS. To simultaneously control the in-plane and out-of-plane vibrations induced by the combined wind and wave loads, another carefully designed (i.e., tuned) spring and dashpot are added to the perpendicular direction of each Tuned Mass Damper (TMD) system that is used to control the vibrations of the tower and blades in one particular direction. With this simple modification, a bi-directional TMD system is formed and the vibrations in both the out-of-plane and in-plane directions are simultaneously suppressed. To examine the control effectiveness, the responses of the wind turbine without control, with separate TMD system and the proposed bi-directional TMD system are calculated and compared. Numerical results show that the bi-directional TMD system can simultaneously control the out-of-plane and in-plane vibrations of the wind turbine without changing too much of the conventional design of the control system. The bi-directional control system therefore could be a cost-effective solution to mitigate the bi-directional vibrations of offshore wind turbines.

Prospects and Economics of Offshore Wind Turbine Systems

Thi Quynh Mai Pham,Sungwoo Im,Joonmo Choung 한국해양공학회 2021 韓國海洋工學會誌 Vol.35 No.5

In recent years, floating offshore wind turbines have attracted more attention as a new renewable energy resource while bottom-fixed offshore wind turbines reach their limit of water depth. Various projects have been proposed with the rapid increase in installed floating wind power capacity, but the economic aspect remains as a biggest issue. To figure out sensible approaches for saving costs, a comparison analysis of the levelized cost of electricity (LCOE) between floating and bottom-fixed offshore wind turbines was carried out. The LCOE was reviewed from a social perspective and a cost breakdown and a literature review analysis were used to itemize the costs into its various components in each level of power plant and system integration. The results show that the highest proportion in capital expenditure of a floating offshore wind turbine results in the substructure part, which is the main difference from a bottom-fixed wind turbine. A floating offshore wind turbine was found to have several advantages over a bottom-fixed wind turbine. Although a similarity in operation and maintenance cost structure is revealed, a floating wind turbine still has the benefit of being able to be maintained at a seaport. After emphasizing the cost-reduction advantages of a floating wind turbine, its LCOE outlook is provided to give a brief overview in the following years. Finally, some estimated cost drivers, such as economics of scale, wind turbine rating, a floater with mooring system, and grid connection cost, are outlined as proposals for floating wind LCOE reduction.

Aerodynamic analysis and control mechanism design of cycloidal wind turbine adopting active control of blade motion

In Seong Hwang,Yun Han Lee,Seung Jo Kim 한국항공우주학회 2007 International Journal of Aeronautical and Space Sc Vol.8 No.2

This paper describes the cycloidal wind turbine, which is a straight blade vertical axis wind turbine using the cycloidal blade system. Cycloidal blade system consists of several blades rotating about an axis in parallel direction. Each blade changes its pitch angle periodically. Cycloidal wind turbine is different from the previous turbines. The wind turbine operates with optimum rotating forces through active control of the blade to change pitch angle and phase angle according to the changes of wind direction and wind speed. Various numerical experiments were conducted to develop a small vertical axis wind turbine of 1 ㎾ class. For this numerical analysis, the rotor system equips four blades consisting of a symmetric airfoil NACA0018 of 1.0 m in span, 0.22 m in chord and 1.0 m in radius. A general purpose commercial CFD program, STAR-CD, was used for numerical analysis. PCL of MSC/PATRAN was used for efficient parametric auto mesh generation. Variables of wind speed, pitch angle, phase angle and rotating speed were set in the numerical experiments. The generated power was obtained according to the various combinations of these variables. Optimal pitch angle and phase angle of cycloidal blade system were obtained according to the change of the wind direction and the wind speed. Based on data obtained from the above analysis, control device was designed. The wind direction and the wind speed were sensed by a wind indicator and an anemometer. Each blades were actuated to optimal performance values by servo motors.

Analysis of Nacelle Cover Shape of 250 KW Wind Turbine

Ambarayil Joy Jithin,정동원,Muhammad Sajjad 한국동력기계공학회 2019 동력시스템공학회지 Vol.23 No.2

The nacelle is located at the top portion of the wind turbine, and it is the heart part of a wind turbine. Rotors and generators are the major components inside the wind generator which turn the wind energy into rotational power and generate electrical energy. The nacelle cover acts as a protective case and a technical compartment containing these important parts. Nacelle covers that protect these critical parts of wind turbines should be as light as possible, ensuring stability for strength and buckling despite strong winds, and sufficiently supported from wind loads, snow loads and self-weights. Nacelle covers of wind turbines are often used in steel sheets such as galvanized steel sheets to withstand wind and snow loads. The weight is heavy and requires a lot of economic consumption, such as the cost of installation, transportation cost, and increased tower thickness while the steel plate's nacelle cover is stable for the applied load. Recently, many wind turbines have a tendency to use a composite material of a nacelle cover; the composite nacelle cover has a similar strength as steel plate and is lighter than a steel plate, making it economical to consider the production cost of wind turbines. In this paper, we are discussing nacelle cover design process and FEM simulation to determine the shape of a wind turbine under the influence of wind. We are using CFD analysis software 'ANSYS workbench' to determine the shape of the current nacelle cover of the 250 KW wind turbine by changing the shape of the nacelle cover and streamlined shape nacelle cover. This study finds out that there are differences to an influence of wind when wind passes through the nacelle cover because of new shape.

Scale model experimental of a prestressed concrete wind turbine tower

Hongwang Ma,Dongdong Zhang,Ze Ma,Qi Ma 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.3

As concrete wind-turbine towers are increasingly being used in wind-farm construction, there is a growing need to understand the behavior of concrete wind-turbine towers. In particular, experimental evaluations of concrete wind-turbine towers are necessary to demonstrate the dynamic characteristics and load-carrying capacity of such towers. This paper describes a model test of a prestressed concrete wind-turbine tower that examines the dynamic characteristics and load-carrying performance of the tower. Additionally, a numerical model is presented and used to verify the design approach. The test results indicate that the first natural frequency of the prestressed concrete wind turbine tower is 0.395 Hz which lies between frequencies 1P and 3P (0.25–0.51 Hz). The damper ratio is 3.3%. The maximum concrete compression stresses are less than the concrete design compression strength, the maximum tensile stresses are less than zero and the prestressed strand stresses are less than the design strength under both the serviceability and ultimate limit state loads. The maximum displacement of the tower top are 331 mm and 648 mm for the serviceability limit state and ultimate limit state, respectively, which is less than L/100 = 1000 mm. Compared with traditional tall wind-turbine steel towers, the prestressed concrete tower has better material damping properties, potential lower maintenance cost, and lower construction costs. Thus, the prestressed concrete wind-turbine tower could be an innovative engineering solution for multi-megawatt wind turbine towers, in particular those that are taller than 100 m.

Investigation on Selecting Optimal Wind Turbines in the Capacity Factor Point of View

Woo Jae-kyoon(우재균),Kim Byeong-min(김병민),Paek In-su(백인수),Yoo Neung-soo(유능수),Nam Yoon-su(남윤수) 한국태양에너지학회 2011 한국태양에너지학회 논문집 Vol.31 No.5

Selecting optimal wind turbine generators for wind farm sites in the capacity factor point of view is performed in this study. A program to determine the best wind turbine generator for the maximum capacity factor for a site was developed. The program uses both the wind characteristics of the site of interest and the power curves of the wind turbines. The program developed was applied to find out optimal wind turbine generators of three different sites in complex terrain and successfully yielded the best site dependent wind turbine generators. It was also used to determine the best wind turbine generator of the wind farm currently operating in Korea and proved its usefulness. The program and methodology developed in this study considered to be very useful at the initial design stage of the wind farm to determine the best wind turbine generators for the site of interest.