• The Journal of the Korea institute of electronic communication sciences
• /
• v.13 no.1
• /
• pp.35-44
• /
• 2018

Korea government aims to generate 20 percent of its electricity with clean, renewable energy by 2030, while reducing its reliance on fossil fuel and nuclear power plants. Technically, solar energy has resource potential that far exceeds the entire global energy demand. Solar energy industry has experienced phenomenal growth in recent years due to both technological improvements resulting in cost reductions and government policies for renewable energy development and utilization. Even though solar power generation has several advantages over other forms of electricity generation, the major problem is the requirement of land which is scarcely available in the local site and its cost. This study analyzes the available capacity of landing and floating solar plants for the case of chonnam province in korea. The results of design capacity show about 7.5GW for landing and 1.5GW for floating solar power plant. Also, with a purpose to comprehend intention-behaviour gap about acceptance of solar community, the solutions are suggested.

• Ocean Systems Engineering
• /
• v.7 no.2
• /
• pp.121-141
• /
• 2017

The purpose of this paper is to understand and model the slow current (~2 m/s) effects on the global response of a floating offshore platform in waves. A time-domain numerical simulation of full wave-current-body interaction by a quadratic boundary element method (QBEM) is applied to compute the hydrodynamic loads and motions of a floating body under the combined influence of waves and current. The study is performed in the context of linearized potential flow theory that is sufficient in understanding the leading-order current effect on the body motion. The numerical simulations are validated by quantitative comparisons of the hydrodynamic coefficients with the WAMIT prediction for a truncated vertical circular cylinder in the absence of current. It is found from the simulation results that the presence of current leads to a loss of symmetry in flow dynamics for a tension-leg platform (TLP) with symmetric geometry, resulting in the coupling of the heave motion with the surge and pitch motions. Moreover, the presence of current largely affects the wave excitation force and moment as well as the motion of the platform while it has a negligible influence on the added mass and damping coefficients. It is also found that the current effect is strongly correlated with the wavelength but not frequency of the wave field. The global motion of a floating body in the presence of a slow current at relatively small encounter wave frequencies can be satisfactorily approximated by the response of the body in the absence of current at the intrinsic frequency corresponding to the same wavelength as in the presence of current. This finding has a significant implication in the model test of global motions of offshore structures in ocean waves and currents.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5B
• /
• pp.539-549
• /
• 2006

The performance of a pontoon-type floating breakwater (FB) is investigated numerically with the use of a second-order time domain model. The model has been developed based on potential theory, perturbation theory and boundary element method. This study is focused on the effects of weakly nonlinear wave on the hydrodynamic characteristics of the FB. Hydrodynamic forces, motion responses, surface elevation, and wave transmission coefficient around the floating breakwater are evaluated for various wave and geometric parameters. It is shown that the second-order wave component is of significant importance in calculating magnitudes of the hydrodynamic forces, mooring forces and the maximum response of a structure. The weak non-linearity of incident waves, however, can have little influence on the efficiency of the FB. From numerical simulations, the ratio of draft and depth, the relationship of wave number and width are presented for providing an effective means of reducing wave energy.

• Journal of the Society of Naval Architects of Korea
• /
• v.39 no.2
• /
• pp.11-18
• /
• 2002

In this paper, the method calculating hydroelastic responses of very large floating structure close to a breakwater in waves is presented. The source-dipole distribution method is used to calculate the generalized radiation problem considering breakwater effects and the diffraction problem is analyzed by using the source-dipole distribution andvelocity potential continuation method. The response of a VLFS is approximated by anexpansion in terms of a free-free beam. Calculated model is a VLFS with 1000m in length in a sea with a straight breakwater. The vertical displacements and bonding moments around a VLFS are calculated by variations for distance between a VLFS and a breakwater and incident wave angle to know the effect of a breakwater.

• Proceedings of the KIEE Conference
• /
• 2008.04c
• /
• pp.166-168
• /
• 2008

DC feeding system is mainly floating but the rail potential and the leakage current are created because of long parallelism between rails and ground. Rail potential causes electric shock to human and leakage current causes electrolytic corrosion to nearby the buried metals. Therefore the design technologies to reduce, protect and monitor these effects are important recent DC feeding system. Rail potential and leakage current are analysed based on propagation theory that is utilized in order to simulate grounding system. New measurement procedure is proposed based on this analysis in order to more be accurate in result.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.4
• /
• pp.2343-2348
• /
• 2014

Main ground net of power plant is formed to protect human body from increase in potential gradient caused by grounding current during ground fault. Calculations during ground design are generally performed according to IEEE Std-80-2000 (Kepco Design Standard 2602). However, it is difficult to apply this Standard to water environment, and a grounding technology is required to secure grounding resistance of floating photovoltaic system. Therefore the aim of this paper is to investigate and analyze ground resistivity on the water surface and underwater of reservoir using Wenner 4-pin method, a general method of measuring ground resistivity. Also, grounding resistance of floating photovoltaic systems currently in operation was measured and analyzed using the voltage drop method suggested in the international standard (IEEE Std-81) to propose a grounding method for stable grounding of floating photovoltaic system. The resistivity at 1m below the surface of water ($126.3969[{\Omega}{\cdot}m]$) is mostly higher than resistivity at the river bed ($97.5713[{\Omega}{\cdot}m]$). Also the proposed grounding anchor method was determined as the most effective method of securing stable grounding resistance in floating photovoltaic systems and is expected to be utilized as a ground method for future floating photovoltaic generation systems.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.29 no.6
• /
• pp.305-314
• /
• 2017

Ocean wave energy harvesting is still too expensive despite developing a variety of wave energy converter (WEC) devices. For the cost-effective wave energy harvesting, it can be an effective measure to use existing breakwaters or newly installed breakwaters for both wave control and energy harvesting purposes. In this study, we investigated the functionality of both breakwater and wave-power generator for the oscillating water column (OWC)-type wave energy converter (WEC) installed in a pneumatic floating breakwater, which was originally developed as a floating breakwater. In order to verify the performance of the breakwater as a WEC, the air flow velocity from air-chamber to WEC has to be evaluated properly. Therefore, air flow velocity, wave transformation and motion of floating structure was numerically implemented based on BEM from linear velocity potential theory without considering the compressibility of air within the chamber. Air pressure, meanwhile, was assumed to be fluctuated by the motions of structure and the water level change within air-chamber. The validity of the obtained values can be determined by comparing the previous results from the numerical analysis for different shapes. Based on numerical model results, wave transformation characteristics around OWC system mounted on the fixed and floating breakwaters, and motions of the structure with air flow velocities are investigated. In summary, all numerical results are almost identical to the previous research considering air compressibility. Therefore, it can be concluded that this analysis not considering air compressibility in the air chamber is more efficient and practical method.

• Journal of the Korean Society for Railway
• /
• v.12 no.1
• /
• pp.161-166
• /
• 2009

DC feeding system is mainly floating but rail potential and leakage current are due to long parallelism between rails and ground, namely rail resistance and rail to ground conductance. Rail potential causes electric shock to human and rail leakage current causes electrolytic corrosion to nearby the buried metals. Therefore the design technologies to reduce, protect and monitor these effects are important in recent DC feeding system. Rail potential and leakage current are analysed based on propagation theory that is utilized. Monitoring and controlling rail leakage current is proposed in order to maintain rail resistance and rail to ground conductance.

• Proceedings of the IEEK Conference
• /
• 2002.07a
• /
• pp.345-348
• /
• 2002

A complementary VHF CMOS active inductor is described. The proposed circuit employs 'p-type' and 'n-type' active inductor to obtain enlarged signal handling ability. Under the same inductance, Q value, and power consumption, the proposed circuit shows more than 12-㏈ improvement in dynamic range while maintaining high-frequency operation. Further enhancement is obtained by using a fully differential floating inductor structure. A 1-㎓ 4$\^$th/-order coupled-resonator filter is designed to demonstrate the potential of the proposed active inductor.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.12
• /
• pp.2173-2178
• /
• 2007

Dynamics of plasma sheath was analyzed using simple ion fluid model with poison equation. Incident ion current, energy, potential distribution and space charge density profile were calculated as a function of time. The effects of initial floating sheath on the evolution of biased sheath were compared with ideal matrix sheath. The effects of finite rising time of pulse bias voltage on the ion current and energy was studied. The influence of surface charging on the evolution of sheath was also investigated