• 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.

• New & Renewable Energy
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• v.16 no.2
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• pp.14-19
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• 2020

Recently, a project to build a carbon zero island with no carbon emissions has been carried out by replacing diesel generators with renewable energy sources in island areas where diesel generators supplied local loads as independent systems. To minimize damage to the lives of islanders, low noise wind generators should be installed by adjusting the rated speed. In islands with low loads, wind turbines that are more efficient than medium-sized wind turbines should be installed. In this study, the generator field analysis and characteristics were analyzed to develop 230 kW-class low wind medium-wind turbine technology. The electromagnetic field analysis program used Maxwell. As a result, the cogging torque was reduced, and the initial maneuver wind speed and loss value were lowered. Hence, the output amount was increased with high efficiency.

• Journal of Ocean Engineering and Technology
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• v.20 no.4 s.71
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• pp.64-69
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• 2006

A numerical analysis is made to investigate the wave absorption efficiency of a OWC-type wave power generator. Energy absorption by an OWC(Oscillating Water Column) air-chamber is computed in regular waves, taking account of the oscillating surface-pressure, due to pressure drop, across the duct of the air chamber. The problem is formulated in the scope of potential theory and solved by the Localized Finite Element Method(LFEM), based on the classical variational principle. The efficiency of energy absorption is investigated by. changing wave conditions, sea-bottom slope and pressure drop coefficient.

• New & Renewable Energy
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• v.16 no.1
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• pp.31-40
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• 2020

Most countries in the world are trying to reduce the use of fossil fuels in the production of electricity and replace them with renewable energy technologies. In Korea, there are abundant ocean renewable energy sources that will play an important role in power generation in the future. This paper introduces a new tidal energy converter utilizing flow induced vibration (FIV), which can work efficiently, even in the currents slower than 1.0m/s. All tests were conducted at the Marine Renewable Energy Laboratory at the University of Michigan to examine the effects of the damping ratio of the electric generators on the power outputs and power efficiencies. In these tests, two identical circular cylinders were used, and passive turbulence controllers were applied to the surface of the cylinders to enhance the FIV. The experimental results showed that by using the two cylinders in the FIV, the power output and efficiency reached up to 31 W and 36%, respectively. In particular, the results showed that the power efficiency was higher at the relatively low flow speed (4

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.1-7
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• 2004

This paper deals with the performance analysis of the impulse turbine for a owe type wave energy conversion device. Numerical analysis was performed using the commercially-available software FLUENT. This parametric study includes variation of the setting angle of the guide vane. Since parametric study at various flow coefficients requires a tremendous amount of computing time, two-dimensional cascade flow approximation was employed to determine the optimum principal particulars in a rather simple manner. A Full three-dimensional calculation was also performed for several cases to confirm the validity of the two-dimensional approach. Results were compared to other experimental data, such as Setoguchi et al. (2001)'s extensive set of data, and found that the usefulness of 2-D analysis was well demonstrated. The advantages of each method were also evaluated.

• Journal of Ocean Engineering and Technology
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• v.37 no.5
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• pp.181-189
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• 2023

The fuel consumption of marine diesel engines holds paramount importance in contemporary maritime transportation and shapes energy efficiency strategies of ocean-going vessels. Nonetheless, a noticeable gap in knowledge prevails concerning the influence of ship hull conditions and propeller roughness on fuel consumption. This study bridges this gap by utilizing artificial intelligence techniques in Matlab, particularly convolutional neural networks (CNNs) to comprehensively investigate these factors. We propose a time-series prediction model that was built on numerical simulations and aimed at forecasting ship hull and propeller conditions. The model's accuracy was validated through a meticulous comparison of predictions with actual ship-hull and propeller conditions. Furthermore, we executed a comparative analysis juxtaposing predictive outcomes with navigational environmental factors encompassing wind speed, wave height, and ship loading conditions by the fuzzy clustering method. This research's significance lies in its pivotal role as a foundation for fostering a more intricate understanding of energy consumption within the realm of maritime transport.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.611-614
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• 2009

The present paper relates to an integration power system combining tidal power generation and ocean current power generation, and more particularly, to an integration power system combining a tidal power plant and two ocean current power parks, which is capable of increasing the operating rate of power facilities and efficiently generating electrical energy by using incoming seawater into the lake through turbine generators of a tidal power plant or fast flow of seawater discharged to a sea side through sluice gates of a tidal power dam. It is shown that the integration power system is a new promising ocean power system and the ocean current turbine generators in the ocean current power parks of the integration power system are smaller in size and larger in power generation capacity compared with the tidal current turbine generators in the ocean.

• Proceedings of KOSOMES biannual meeting
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• 2018.06a
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• pp.175-175
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• 2018

• Nuclear Engineering and Technology
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• v.23 no.4
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• pp.387-400
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• 1991

An ocean compartment model simulating transport of nuclides by advection due to ocean circulation and intertaction with suspended sediments is developed, by which concentration breakthrough curves of nuclides can be calculated as a function of time. Dividing ocean into arbitrary number of characteristic compartments and performing a balance of mass of nuclides in each ocean compartment, the governing equation for the concentration in the ocean is obtained and a solution by the numerical integration is obtained. The integration method is specially useful for general stiff systems. For transfer coefficients describing advective transport between adjacent compartments by ocean circulation, the ocean turnover time is calculated by a two-dimensional numerical ocean model. To exemplify the compartment model, a reference case calculation for breakthrough curves of three nuclides in low-level radioactive wastes, Tc-99, Cs-137, and Pu-238 released from hypothetical repository under the seabed is carried out with five ocean compartments. Sensitivity analysis studies for some parameters to the concentration breakthrough curves are also made, which indicates that parameters such as ocean turnover time and ocean water volume of compartments have an important effect on the breakthrough curves.

• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.43-48
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• 1990

The results of previous works on the wave energy conversion do not seem to be satisfactory due to irregularity, and the non-linear hydrodynamic effect which is inevitably featured due to the structural complexity of the ocean wave energy conversion device. These may cause the difficulty estimating the extracted wave power. In this paper a study on estimating the extracted wave power and its ratio. The present authors have developed another method estimating the extracted wave power using the three dimensional source distribution method, which was turned out to be an improved one. It has been observed that the present results may be used for the control of the wave energy conversion device and the optimal design has been derived from the several case studies.