• Journal of Advanced Marine Engineering and Technology
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• v.36 no.5
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• pp.707-715
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• 2012

Ocean waves are mighty and powerful. Humans have explored the possibility of harnessing this mighty power for decades now. Estimated as suffice, if only, a fraction of this energy is captured and harnessed, the worry for decrease in fossil fuels diminishes and the current energy consumption of the world can be met. Though different types of methods and devices for extracting energy from this nonstop, free source has been proposed, a handful of them have reached commercialization and others are on the verge. This paper discusses the journey so far in terms of devices that have been developed or prototypes proposed or commercialized. Only a list full of them have been discussed though they exist in numbers.

• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.8-13
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• 2011

A compact array system of small buoys is used for wave energy extraction. To evaluate the performance of this system, hydrodynamic analysis is carried out in regular waves using the higher order boundary element method. The motion response of each buoy is calculated considering hydrodynamic interactions caused by other buoys. The effect of energy extraction device is modeled as a linear damping load. The efficiencies of energy conversion are compared using the various sizes and arrangements of the array system and the damping coefficients for energy extraction. The increase in size or the packing ratio of the system gives better efficiency. However, the wave condition and the cost for the system should be considered to optimize performance from the perspective of engineering and economics. The proposed nondimensionalized damping coefficient for energy extraction is 0.1~0.5.

• Ocean Systems Engineering
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• v.11 no.1
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• pp.1-16
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• 2021

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.3
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• pp.31-38
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• 1991

Due to the structural complexity and the mutual interference of "water columns", the estimations of absorption power for a large wave energy conversion devices of flosting type in ocean could not achieve the desired results. Thus, in this paper the authors will propose a new methodology based on the three dimensional source ditribution method. We distributed the source to the device and the thin & light plate in "water column", And from the behaviour of this plated, the power and the pressure in water column are calculated. But, yet method should be proved to be valid by experiment.

• Journal of Navigation and Port Research
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• v.31 no.10
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• pp.845-852
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• 2007

An OWC-type Wave Energy Conversion passes through 3 steps energy conversion process. This paper deal with the impulse turbine with staggered blade to improved performance by numerical analysis using commercial CFD code, FLUENT Maximum value of axial airflow velocity during exhalation is higher than that during inhalation This paper deal with special-type of Impulse Turbine so-called "Staggered Blade" for more efficiency to making air flow direct to on pressure side. Also, this paper has proposed special-type turbine with self-pitched blade more efficient.

• Journal of Ocean Engineering and Technology
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• v.36 no.4
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• pp.280-294
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• 2022

This study reviews the recent development and research results of a fixed oscillating water column (OWC) wave energy converter (WEC). The OWC WEC can be divided into fixed and floating types based on the installation location and movement of the structure. In this article, the study on a stationary OWC WEC, which is close to commercialization through the accumulation of long-term research achievements, is divided into five research categories with a focus on primary energy conversion research. These research categories include potential-flow-based numerical analysis, wave tank experiments, computational fluid dynamics analyses toward investigation of fluid viscous effects, U-shaped OWC studies that can amplify water surface displacement in the OWC chamber, and studies on OWC prototypes that have been installed and operated in real sea environments. This review will provide an overview of recent research on the stationary OWC WEC and basic information for further detailed studies on the OWC.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.1
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• pp.12-17
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• 2010

Oscillating Water Column (OWC) device has been widely employed in the wave energy conversion. Wave Focusing Device (WFD) is proposed to be helpful for improving the operating performance of OWC chamber. In the present paper, a Numerical Wave Tank (NWT) using two-phase VOF model is utilized to simulate the generation and propagation of incident regular waves, water column oscillation inside the chamber. The NWT consists of the continuity equation, Reynolds-averaged Navier-Stokes equations and two-phase VOF functions. The standard k- turbulence model, the finite volume method, NITA-PISO algorithm and dynamic mesh technique are employed. Effects of WFD on the operating performance of OWC chamber are investigated numerically.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.833-838
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• 2003

The problem of elastic wave resonance scattering from elastic targets is studied in this paper. A new resonance formalism to extract the elastic resonance information of the target from scattered elastic waves is introduced. The proposed resonance formalism is an extension of the works developed for acoustic wave scattering problems by the author. The classical resonance scattering theory computes reasonable magnitude information of the resonances in each partial wave, but the phase behaves in somewhat irregular way, therefore, is not clearly explainable. The proposed method is developed to obtain physically meaningful magnitude and phase of the resonances. As an example problem, elastic wave scattering from an infinitely-long elastic cylinder was analyzed by the proposed method and compared to the results by RST. In case of no mode conversion, both methods generate identical magnitude. However, the new method computes exact $\pi$ radian phase shills through resonances and anti-resonances while RST produces physically unexplainable phases. In case of mode conversion, in addition to the phase even magnitudes are different. The phase shifts through resonances and antiresonances obtained by the proposed method are not exactly $\pi$ radians due to energy leak by mode conversion. But, the phases by the proposed method show reasonable and intuitively correct behavior compared to those by RST.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.630-631
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• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for two different models. Observation of flow characteristics, pressure and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.1
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• pp.79-87
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• 2015

This paper proposes a floating-type wave energy conversion system that consists of a mechanical part (yo-yo vibrating system, motion rectifying system, and power transmission system) and electrical part (power generation system). The yo-yo vibrating system, which converts translational input to rotational motion, is modeled as a single degree-of-freedom system. It can amplify the wave input via the resonance phenomenon and enhance the energy conversion efficiency. The electromechanical model is established from impedance matching of the mechanical part to the electrical system. The performance was analyzed at various wave frequencies and damping ratios for a wave input acceleration of 0.14 g. The maximum output occurred at the resonance frequency and optimal load resistance, where the power conversion efficiency and electrical output power reached 48% and 290 W, respectively. Utilizing the resonance phenomenon was found to greatly enhance the performance of the wave energy converter, and there exists a maximum power point at the optimum load resistance.