Chul H. Jo

Parametric study on offshore jacket launching

Platform structures are commonly utilized for various purposes including offshore drilling, processing and support of offshore operations. Jacket type structures are attractive in relatively shallow water regions. A jacket is a supporting structure for deck facilities stabilized by leg piles through the seabed. The size of a jacket is dependent on deck size, pile dimensions and environmental loads. In a jacket design, operational and environmental loads are very important and must be investigated intensively to secure the stability of structures during their operation life, and installation phase as well. To confirm the stability, several analyses including in-place, fatigue, dynamic, load-out, transportation, lifting, and launching are performed. As the jacket weight and dimensions become large, a launching technique is applied to install the jacket. The launching analysis needs to consider quite a number of parameters including environmental conditions, launch barge specification, ballast, trim angle, local member integrity, etc. Due to the complexity of the operation, there is not a straightforward guideline or procedure for analysis. In this paper, a general procedure for analysis with various conditions and launching criteria are discussed and investigated. The effects of parameters are closely examined by numerical modeling.

Multi-arrayed tidal current energy farm and the integration method of the power transportation

Ocean energy resources are attractive renewable supply options for Korea being surround by ocean. Also having very strong tidal current speeds, there are many suitable sites for the application of TCP (Tidal Current Power) on the west and south coastal region in Korea with the maximum current speed of up to 6.5m/s. Not like other renewable energy sources, TCP is the high reliable and predictable and continuous energy source as the current pattern and speed can be predicted throughout the year. Since the large scale tidal current farm consists of many units of the turbine devices, the interaction effect is very important in power production. Also the power integration method in ocean energy has of very important issue. In this paper, the interaction effect and the power connection methods for each turbine unit and the integration method for 200MW tidal current farm are conceptually introduced with the offshore power integration platform.

Study of a real time emulator for marine current energy conversion

This paper presents the development of a real time marine current turbine emulator conceived with the “hardware-in the-loop” simulation techniques. The emulator is structured in two systems: an electromechanical system based on three main components: a vector controlled asynchronous machine, a double-feed asynchronous generator, and an active break; a real time software system, in which the static and dynamic characteristics of marine current turbine are implemented. The electromechanical system is controlled by the software system and provides on his shaft the characteristics as a real marine current turbine.

Investigation of jetting system of the spudcan to ease extraction in clayey soilsa)

An offshore wind turbine in shallow water is installed by a self-elevated mobile unit that is usually referred to as a jack-up barge or jack-up vessel. The jack-up vessel consists of a buoyant platform together with independent legs that can position the vessel above the water, thereby reducing external loadings for a safe operation condition. The retrieval process for the jack-up legs can be very difficult due to the high extraction resistance caused by soft soil. In soft clay, high suction force can develop around the spudcan attached at the end of the jack-up legs. Therefore, a jetting system is required to break the suction in order to pull out the legs. It is important to design the jetting system with an optimized piping arrangement to allow the easy operation. Various factors must be considered in the design of the jetting piping system since the level of embedment, type of soil, and pipe sizes and locations can affect the performance of the system. In this paper, we present the characteristics of ...

Experimental study on tensioned wire maintenance concept for tidal current turbine

Even tidal current power can extract electricity from ocean current, it is to be installed and operated in a high current speed regions. Having a limited accessible window, it is very important and critical to minimize the retrieval and installation duration. Also the driverless scheme is very efficient to reduce any hazard to the diver during the maintenance in the limited working hours. The maintenance scheme is to be developed as per the site conditions and also the device configurations and specifications. In this paper, a tensioned wire maintenance concept developed for HAT (Horizontal Axis Turbine) device is introduced with the experimental approaches at various current speeds.

A Study on Internal Flow Characteristics of T Branch using CFD Analysis

This study describes the effect of T branch shape on internal flow characteristics inside itself. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equation have been used as governing equations for the numerical analysis. The T branch was modeled assuming that it is used for Alaska pipeline project which was planned to provide reliable transportation of natural gas from ANS to Alaska-Yukon border. Therefore the characteristics of T branch and operating condition of pipeline were from report of Alaska pipeline project. The nine T branch shapes were analyzed and the mass flow rate ratio between mainline and branch was assumed to be 0.95 : 0.05, 0.9 : 0.1, 0.85 : 0.15. The results shows that there are typical flow patterns in T branch and the shape of T branch makes some differences to the internal flow of branch rather than mainline.

Numerical Study about Influence Variables of Permafrost Pipeline by using Thermal Flow Analysis

Abstract >> This paper describes thermal flow characteristics in various pipelines: straight pipeline and curvedpipeline. In the permafrost area, pipelines are exposed to an extremely low temperature (-40°C). In this situation, three-dimensional flow analysis should be analyzed to investigate thermal effects such as pressure drop, temperaturechange, velocity deficit and distribution change of liquid droplet of internal fluid. In this paper, multi-phase and multi-species analysis was introduced to analyze the flow characteristics of permafrost pipelines on the verticalsupport members above ground. Key words : Pipeline(파이프라인), Permafrost(영구동토), CFD(Computational Fluid Dynamics, 전산유체역학), Natural Gas(천연가스), Thermal Flow(열유동), Multiphase Flow(다상유동) † Corresponding author : ljunh330@inha.edu [ 접수일 : 2014.06.10 수정일 : 2014.08.02 게재확정일 : 2014.08.31 ]Copyright ⓒ 2014 KHNES 1. 서 론 세계적으로 지구 온난화 방지를 위한 온실가스 배출 규제가 시작되었고, 환경규제도 또한 강화되고 있다. 그러나 세계 각국의 기간산업은 화석연료에 기반하고 있기 때문에 화석연료 의존도는 매우 높고 자원 확보의 중요성 또한 크게 증가하고 있는 실정이다. 화석연료 자원 확보를 위해 강대국 간의 경쟁이 치열해지고 있으며, 지속적이고 안정적인 에너지 확보를 위해 육상에서 해양 및 극한지로 그 영역을 확장시키고 있다

Analysis of the Characteristics of PMSG Tidal Current Power Generation System Using PMSG and Water Tunnel

In order to analyze the characteristics of tidal current power generation system, we measured the output power according to the stream velocity by a water tunnel system and a simulation in MATLAB/Simulink. The water tunnel system consisted of impeller tidal flow transducer and permanent magnet synchronous generator (PMSG) with rotor in the water. The simulation consisted of PMSG, the tidal current turbine, and Back-to-Back converter. Also, we simulated the characteristics of output power according to the change of blade radius and velocity.

Concept development of real time emulators for offshore wind power (OWP) and tidal current power (TCP) hybrid system

This paper presents a research work that will enable realize a HILS system to study a hybrid system based on an offshore wind turbine and a tidal current power system. In the first part, its presented the general structure of a HIL simulator. Next, the composition of the two emulators (tidal and wind) is described. The fifth part is devoted to the modeling of the two energy systems conversion. Finally, the topology of coupling mode is presented and its proposed to adopt for further studies.

HILS systems applied to real time emulation for wind energy study

The purpose of this paper is to present a real time wind simulator and its different uses. Given the fact that the simulator is based on a doubly fed induction generator, one of the uses can be the study of different aspects of grid connection and impacts of different faults that may occur in normal operation of wind systems. The studied system is a variable speed wind turbine system with a Doubly Fed Induction Generator (DFIG). The stator of the generator is directly connected to the grid while the rotor is connected through a back-to-back converter which is dimensioned to stand only for a fraction of the generator rated power. The simulator is developed using Hardware-in the-Loop techniques and in order to provide the static and dynamic characteristics of a wind turbine system. We analyzed and developed an experimental system consisting of two main parts: a real time software simulator and an electromechanical system. The Electromechanical System is composed from three electrical drives: an asynchronous machine that emulates the wind turbine, an asynchronous generator, used to study the energy conversion and grid connection problems. The Software simulator is a supervising and control subsystem and is composed from a computational unit and different interface devices. This subsystem is designed equally to study the capability of the classical network to support wind turbine penetration and grid faults impacts. Experimental results from the simulator are presented in order to compare different simulation procedures.