• 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 Korea Water Resources Association
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• v.49 no.3
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• pp.227-239
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• 2016

This study is to estimate Surface Energy Balance Algorithm for Land (SEBAL) daily spatial evapotranspiration (ET) comparing with eddy covariance flux tower ET in Seolmacheon mixed forest (SMK) and Cheongmicheon rice paddy (CFK). The SEBAL input data of Albedo, Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI) from Terra MODIS products and the meteorological data of wind speed, and solar radiation were prepared for 2 years (2012-2013). For the annual average flux tower ET of 302.8 mm in SMK and 482.0 mm in CFK, the SEBAL ETs were 183.3 mm and 371.5 mm respectively. The determination coefficients ($R^2$) of SEBAL ET versus flux tower ET for total periods were 0.54 in SMK and 0.79 in CFK respectively. The main reason of SEBAL ET underestimation for both sites was from the determination of hot pixel and cold pixel of the day and affected to the overestimation of sensible heat flux.

• Smart Structures and Systems
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• v.24 no.6
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• pp.769-781
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• 2019

Dynamic displacement response of civil structures is an important index for in-construction and in-service structural condition assessment. However, accurately measuring the displacement of large-scale civil structures such as high-rise buildings still remains as a challenging task. In order to cope with this problem, a vision-based system with the use of industrial digital camera and image processing has been developed for long-distance, remote, and real-time monitoring of dynamic displacement of supertall structures. Instead of acquiring image signals, the proposed system traces only the coordinates of the target points, therefore enabling real-time monitoring and display of displacement responses in a relatively high sampling rate. This study addresses the in-situ experimental verification of the developed vision-based system on the Canton Tower of 600 m high. To facilitate the verification, a GPS system is used to calibrate/verify the structural displacement responses measured by the vision-based system. Meanwhile, an accelerometer deployed in the vicinity of the target point also provides frequency-domain information for comparison. Special attention has been given on understanding the influence of the surrounding light on the monitoring results. For this purpose, the experimental tests are conducted in daytime and nighttime through placing the vision-based system outside the tower (in a brilliant environment) and inside the tower (in a dark environment), respectively. The results indicate that the displacement response time histories monitored by the vision-based system not only match well with those acquired by the GPS receiver, but also have higher fidelity and are less noise-corrupted. In addition, the low-order modal frequencies of the building identified with use of the data obtained from the vision-based system are all in good agreement with those obtained from the accelerometer, the GPS receiver and an elaborate finite element model. Especially, the vision-based system placed at the bottom of the enclosed elevator shaft offers better monitoring data compared with the system placed outside the tower. Based on a wavelet filtering technique, the displacement response time histories obtained by the vision-based system are easily decomposed into two parts: a quasi-static ingredient primarily resulting from temperature variation and a dynamic component mainly caused by fluctuating wind load.

• Korean Journal of Construction Engineering and Management
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• v.9 no.2
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• pp.108-116
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• 2008

At present, construction automation is a critical solution for the shortage of labor and the aging of skilled workers. Especially, researches for transportation automation are achieved to improve the efficiency as the construction of tall-building construction. Transportation automation needs to control the swung member by the inertia and/or the wind-force at the end of cable. However, previous to control, the presupposition of the swing is heavily difficult work because the inertia and the wind force are irregularly changable according to work condition. Therefore, in this study, dynamic modeling of crane and simulation was performed to find the characteristic of the swing. In the result, the maximum displacement of the swung material was analyzed. And, on the basis of analysis, the criteria to decide workability of automated transportation considering the material size and the wind force onsite was proposed.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.81-89
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• 2012

Commonly used horizontal-axis wind turbines (HAWT) have the following structure: two or three blades, a nacelle which contains power converting equipments, generators, and a tower which supports the nacelle. The generated power is transmitted from the nacelle to the ground. Due to this structure, the power transmission lines are twisted when the nacelle is yawing. Thus, slip ring or additional yaw control mechanism is required. We propose a new structure of HAWT which is free of this transmission line problem. Moreover, the size of inverter can be reduced since two generators are connected in parallel in our mechanism so that power is distributed. A controller for yawing is developed so that it works in harmony with the controller for power generation. A MPPT (Maximum Power Point tracking) algorithm is implemented for the proposed system and efficiency of the system is validated by simulation.

• Bulletin of the Korea Photovoltaic Society
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• v.3 no.1
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• pp.61-67
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• 2017

Concentrated solar power(CSP) is receiving attention for its ability to generate dispatchable power from heat stored in thermal energy storage(TES). There are currently four types of CSP technology, however experts expect that only parabolic trough and solar tower are to survive from the market due to its higher efficiency and larger capacity in storage. While the initial cost for installing CSP plant is still expensive, the experts expect that investment cost of CSP would decline to the level which would be competitive with PV or wind in the near term future. In addition, further growth in its installation capacity is expected due to the United States and China's aggressive investments in CSP.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.163-169
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• 2000

Design and developments of a propeller fan for a cooling tower have been accomplished by both numerical prediction of performance and experimental validation with a wind tunnel, Main interest lies on blade geometry of a fan for optimal design of aerodynamic performance. The present methodology for numerical estimation is commercial program, Fine/Turbo, which gives us engineering information such as flow details near the blades and flow rate of it. The numerical results are compared with precise experimental output and show good agreement. Also new proposed model of a blade with the program show improved performance relative to present running model in market.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.78-83
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• 2010

Since a tower crane is too high for a worker to ascend and by the wind in the high altitude, the possibility of a safety accident is very high, a lift assist is used. In this study, the hydraulic fall prevention device using the pressure generation device by Seok, et al. was developed. For this, the effects on the fall prevention performances of factors such as gear clearance, oil viscosity, rotative velocity and so on were evaluated by the analysis of fluid flow using FEM and the prototype was producted and a function test was performed.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.276_277
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• 2009

풍력 케이블의 nacelle부와 Tower 사이에 포설되는 케이블은 사용 환경의 특성상 장력+비틀림의 스트레스를 받는다. 이러한 사용 환경 때문에 케이블은 전기적인 특성 뿐 아니라 반복 운동을 하는 환경에 대해 구조적인 특성에 대해서도 검토가 요구되어진다. 본 논문에서는 풍력 케이블의 핵심 검토 요소로 도체의 구조적 위험 요소를 줄이기 위한 연구 대상으로 도체의 (*)피치 변화의 특성을 분석하였으며, 피치가 길어지면 도체에 발생되어지는 응력(스트레스)이 작아질 것이고 피치가 짧아지면 도체에 발생되어지는 응력(스트레스)이 커질 것이라는 일반적인 상식을 벗어나 각 피치별 응력(스트레스)의 최저점들을 찾게 되었고 그 중 유연성을 함께 고려하여 품질의 향상을 기여하는 최적 피치를 선정하였다.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.263-268
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• 2008

In a residential complex case, the efficiency of land use are maximized, but a variation of external condition such as load in-equality, the increase in wind velocity and solar radiation by a height causes increasing energy in a building. Besides, because of increasing window size for a lighting and a view, it comes heating load in winter and cooling load in summer. A choice of cooling-system is important for this reason. Recently an internal high-rise residential complex installs an air-cooling system and operates individual heating. However, this study applies water-cooling used one public cooling-tower instead of an air-cooling system, also with an efficiency test of an air and a water-cooling system, consider an internal applicability.