• 드라이브 ㆍ 컨트롤
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• 제12권3호
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• pp.25-35
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• 2015

The hydraulic power-take-off mechanism (HPTO) is one of the most popular methods in wave energy converters (WECs). However, the conventional HPTO with only one direction motion has a number of drawbacks that limit its power capture capability. This paper proposes an adjustable moving angle wave energy converter (AMAWEC) and investigates the effect of the moving angle on the performance of the wave energy converter to find the optimal moving angle in order to increase the power capture capability as well as energy efficiency. A mathematical model of components from a floating buoy to a hydraulic motor was modeled. A small scale WEC test rig was fabricated to verify the power capture capability and efficiency of the proposed system through experiments.

• International Journal of Fluid Machinery and Systems
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• 제9권3호
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• pp.222-228
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• 2016

Almost 70% of the earth is covered by the ocean. Extracting the power available in the ocean using a wave energy converter has been seen to be eco-friendly and renewable. This study focuses on developing a method for analyzing a wave energy device that uses a cross-flow turbine. The motion of the ocean wave causes an internal bi-directional flow of water and the cross-flow turbine is able to rotate in one direction. This device is considered of double-hull structure, and because of this structure, sea water does not come into contact with theturbine. Due to this, the problem of befouling on the turbine is avoided. This study shows specific relationship for wave length and several motions.

• 한국산업융합학회 논문집
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• 제23권6_2호
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• pp.999-1006
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• 2020

This study was conducted to develop an efficiency prediction program of a hydraulic secondary energy converter for calculating annual power generation of a Wavestar type wave power generator. Using the period and wave height obtained from the frequency domain analysis, the behavior of the floating body was obtained by assuming the sin function. The piston displacement and speed of the hydraulic cylinder were calculated considering the behavior of the floating body and the shape of the mechanism. The numerical simulation of the hydraulic system was performed by physically modeling the hydraulic cylinders, check valves, hydraulic motors, which are the main devices. In the future, this analysis program will be used to develop a program for estimating annual power generation of a moveable body type wave power generation device.

• 한국해양공학회지
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• 제35권3호
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• pp.216-228
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• 2021

In the present study, the performance of a floating oscillating water column (OWC) device has been studied in regular waves. The OWC model has the shape of a hollow cylinder. The linear potential theory is assumed, and a matched eigenfunction expansion method(MEEM) is applied for solving the diffraction and radiation problems. The radiation problem involves the radiation of waves by the heaving motion of a floating OWC device and the oscillating pressure in the air chamber. The characteristics of the exciting forces, hydrodynamic forces, flow rate, air pressure in the chamber, and heave motion response are investigated with various system parameters, such as the inner radius, draft of an OWC, and turbine constant. The efficiency of a floating OWC device is estimated in connection with the extracted wave power and capture width. Specifically, the piston-mode resonance in an internal fluid region plays an important role in the performance of a floating OWC device, along with the heave motion resonance. The developed prediction tool will help determine the various design parameters affecting the performance of a floating OWC device in waves.

• 한국해양공학회지
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• 제27권6호
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• pp.27-31
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• 2013

The structure of a variable liquid column oscillator(VLCO) is analogous to that of the tuned liquid column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. The VLCO is a system for absorbing the high kinetic energy of the accelerated motions of multiple floating bodies using an air-spring effect produced the installation of inner air chambers. Thus, a VLCO can improve the energy efficiency of the activating object type of wave energy converters made by the Pelamis Company. In this research, an experiment was performed in two cases: with the top valves closed and open. The floating bodies were connected by hinges. The effect of the internal flow was estimated by comparing the results for the closed and open valves.

• Journal of Advanced Marine Engineering and Technology
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• 제40권8호
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• pp.710-720
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• 2016

The Floating Wave Energy Convertor (FWEC) mooring design has an important requirement associated with the fact that, for a wave energy converter, the mooring connections may interact with their oscillations, possibly modifying its energy absorption significantly. It is therefore important to investigate what might be the most suitable mooring design according to the converter specifications and take into account the demands placed on the moorings in order to assure their survivability. The objective of this study is to identify a computational fluid dynamics method for investigating the effects of coupling a wave energy device with a mooring system. Using the commercial software ANSYS AQWA and ANSYS FLUENT, a configuration was studied for different displacements from the equilibrium position, load demands on the moorings, and internal fluid motion. These results and findings form a basis for future efforts in computational model development, design refinement, and investigation of station keeping for FWEC units.

• Journal of Advanced Marine Engineering and Technology
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• 제32권1호
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• pp.169-174
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• 2008

Floating devices, such as a cavity resonance device take advantage of both the water motion and the wave induced motions of the floating body itself. The wave energy converter is known commercially as the WAGB(Wave Activated Generator Buoy) and is used in some commercially available buoys to power navigation aids such as lights and horns. This wave energy converter consists of a circular floatation body which contains a vertical center pipe that has free communication with the sea. A theoretical analysis of this power generated by a pneumatic type wave energy converter is performed and the results obtained from the analysis are used for a real wave energy converter for buoy. This paper presents the analysis results and the design method for the WEC(Wave Energy Converter), and the associate results are application to the commercially available WEC for buoy. Maximum performance of WEC occurs at resonance with driving waves. The analysis of WEC is performed with LabVIEW program, and the design method of WEC for buoy is suggested in this paper.

• 한국해안·해양공학회논문집
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• 제29권6호
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• pp.305-314
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• 2017

단독의 파력발전변환장치를 설치하는 경우 경제성이 떨어지는 문제점이 있으므로 기존 혹은 신설의 방파제에 적용하여 파랑제어와 파랑에너지의 이용을 동시에 도모하는 방식이 많이 추진되어 왔다. 본 연구는 전편의 연구(Lee et al., 2014)에서와 같이 부유식방파제로 연구 개발된 공기주입식 부유식방파제에 진동수주형 파력발전시스템을 탑재한 경우를 대상으로 부유식방파제로의 기능과 파력발전장치로의 기능을 병행하여 검토하였다. 여기서, 전편의 연구(Lee et al., 2014)에서는 공기실내에서 공기의 동적거동에 단열변화에 따른 압축성을 고려한 반면에 본 연구에서는 비압축성의 경우에 구조물의 고정시 혹은 부유시에 각각에 대한 파랑변형율, 공기흐름속도 및 구조물의 운동을 검토하였으며, 공기의 동적거동에 대한 압축성의 고려여부에 따른 결과의 차이를 논의하였다. 수치해석법으로는 선형속도포텐셜이론에 기초한 경계요소법을 적용한다. 얻어진 모든 해석결과에 따르면 공기압축성을 고려한 전편의 연구와 거의 동일한 결과를 나타내었으며, 따라서 공기실내에서의 공기거동해석에 압축성을 고려하지 않는 본 해석이 보다 효율적이고, 유용한 것으로 판단된다.

• International journal of advanced smart convergence
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• 제12권2호
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• pp.182-186
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• 2023

In this study, we measured the power and temperature of the floating horizontal solar cell in a coastal lagoon and compared with those of ground solar cell and water platform solar cell. Because the bottom surface of the floating horizontal solar cell was contacting the water, cooling effect was expected stronger than other cells. As a result of the measurement, the power of floating horizontal cell was 11.7% higher than that of the ground cell and 15% higher than that of the water platform cell. During the measurement, it was observed that water waves were continuously flowed on the top surface of floating horizontal cell by the wind, and it could be assumed that the cooling effect occurred not only on the bottom surface of the cell but also on the top surface. In order to analyze the cooling effect and power increasing of the horizontal cell in the wave situation, we measured power and temperature of the cell while generating artificial waves in a laboratory equipped with Zenon lamp as a solar simulator. At the height of thewater surface, the power of the cell with waves was 3.7% higherthan without waves and temperature was 4.6℃ lower. At 1 cm and 2 cm below the watersurface, power of the cell with waves was decreased by 14% and 11% than without waves while temperature was same . At 3 cm below the water surface, there was no effect of waves.

• 한국해양공학회지
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• 제36권6호
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• pp.390-402
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• 2022

Offshore wind energy has become a major energy source, and various studies are underway to increase the economic feasibility of floating offshore wind turbines (FOWT). In this study, the characteristics of wave-induced motion of a combined wind-wave energy platform were analyzed to reduce the variability of energy extraction. A user subroutine was developed, and numerical analysis was performed in connection with the ANSYS-AQWA hydrodynamic program in the time domain. A platform combining the TLP-type FOWT and the Wavestar-type wave energy converter (WEC) was proposed. Each motion response of the platform on the second-order wave load, the effect of WEC attachment and Power take-off (PTO) force were analyzed. The mooring line tension according to the installation location was also analyzed. The vertical motion of a single FOWT was increased approximately three times due to the second-order sum-frequency wave load. The PTO force of the WEC played as a vertical motion damper for the combined platform. The tension of the mooring lines in front of the incident wave direction was dominantly affected by the pitch of the platform, and the mooring lines located at the side of the platform were mainly affected by the heave of the platform.