• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.8-22
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• 2020

In this study, we investigated the deactivation characteristics of Ni-Zn-Fe electrodes due to intermittent operation in alkaline water electrolysis. To find suitable method to accelerate deactivation of electrode, the accelerated stress-test (AST) which repeated on/off step was performed with constant current/voltage control. The AST under constant voltage control is suitable to deactivate electrode so it were selected to investigate deactivation of electrode. The AST which repeated on/off step in range of -1.3 V and 0 V was performed and the relationship between oxidation current and electrode deactivation in the off step was investigate. As results, it was confirmed that the nickel and zinc on electrode surface were oxidized due to anodic current which occurred at off step.

• 전기학회논문지
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• 제59권7호
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• pp.1259-1264
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• 2010

This paper was researched about effectiveness of the electrochemical cell which is composed of the sea water and the Cu/Zn electrode. The electric potential difference between copper and zinc finally reached 0.51 volts. Short current decreased with time. It might depend on the electromotive force decreasing. Confirmed the load resistance and electrode affect in electromotive force and electric current. The resistance which shows a maximum output power was 20[$\Omega$], and the maximum output power from this resistance was evaluated as 0.736mW. In order to calculate the energy which creates from electrochemical cell, charging voltage of the capacitor with various capacitance was investigated. It was found that energy harvesting possibility of the cell which is made of a sea water electrolyte and the copper/the zinc.

• 한국해양공학회지
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• 제26권4호
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• pp.37-41
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• 2012

Due to global warming, the need to secure alternative resources has become more important nationally. Because of the very strong current on the west coast, with a tidal range of up to 10 m, there are many suitable sites for the application of TCP (tidal current power) in Korea. In the southwest region, a strong current is created in the narrow channels between the numerous islands. A rotor is an essential component that can convert tidal current energy into rotational energy to generate electricity. The design optimization of a rotor is very important to maximize the power production. The performance of a rotor can be determined using various parameters, including the number of blades, shape, sectional size, diameter, etc. There are many offshore jetties and piers with high current velocities. Thus, a VAT (vertical axis turbine) system, which can generate power regardless of flow direction changes, could be effectively applied to cylindrical structures. A VAT system could give an advantage to a caisson-type breakwater because it allows water to circulate well. This paper introduces a multi-layer vertical axis tidal current power system. A Savonius turbine was designed, and a performance analysis was carried out using CFD. A physical model was also demonstrated in CWC, and the results are compared with CFD.

• International Journal of Ocean System Engineering
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• 제1권3호
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• pp.144-147
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• 2011

The rotor that initially converts the flow energy into rotational energy is a very important component that affects the efficiency of the entire tidal current power system. Rotor performance is determined by various design variables. Power generation is strongly dependent on the incoming flow velocity and the size of the rotor. To extract a large quantity of power, a tidal current farm is necessary with a multi-arrangement of devices in the ocean. However, the interactions between devices also contribute significantly to the total power capacity. Therefore, rotor performance, considering the interaction problems, needs to be investigated to maximize the power generation in a limited available area. The downstream rotor efficiency is affected by the wake produced from the upstream rotor. This paper introduces the performance of a downstream rotor affected by wakes from an upstream rotor, demonstrating the interference affecting various gabs between devices.

• 전기화학회지
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• 제9권4호
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• pp.151-157
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• 2006

A two-dimensional numerical model to study the performance of anode-supported flat-tube solid oxide fuel cell (SOFC) far the cross section of the cell in the flow direction of the fuel and air flows is developed. In this model a mass and charge balance, Maxwell-Stefan equation as well as the momentum equation by using, Darcy's law are applied in differential form. The finite element method using FEMLAB commercial software is used for meshing, discritization and solving the system of coupled differential equations. The current density distribution and fuel consumption as well as water production are analyzed. Experimental data is used to verify a predicted voltage-current density and power density versus current density to judge on the model accuracy.

• 한국해양환경ㆍ에너지학회지
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• 제12권4호
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• pp.235-247
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• 2009

나로도를 중심으로 한 한국 남해안에서 발생하는 C. polykrikoides 적조의 원인 규명을 위해 1995년부터 2008년까지 국립수산과학원이 조사한 정선해양관측 및 위성정보 자료에 기초하여 동계 및 하계에 있어서의 수온염분 분포의 특징을 조사하였다. C. polykrikoides 적조는 나로도 주변 해역에서의 평균 수온이 약 $25.0{\sim}26.0^{\circ}C$, 염분이 약 31.00 psu 전후일 때 가장 많이 발생하였다. 한국남해 연안수와 외해수 사이에는 동계 및 하계에 각각 서로 다른 열염전선이 관측되었다. 즉, 동계에는 저온저염의 한국남해 연안수, 쓰시마 난류계의 중간수, 고온고염의 쓰시마 난류, 저온저염의 중국대륙 연안수 사이에 네 개의 전선이 관측되었다. 반면, 하계에는 저온고염의 한국남해 연안수, 고온저염의 쓰시마 난류, 고온고염의 중국대륙 연안수 사이에 두 개의 전선이 관측되었다. 이러한 열염전선은 서로 물리적 성질이 다른 수괴에 의해 형성된다는 사실이 T-S diagram을 통해서도 확인되었다. 이상으로부터, 나로도 주변해역에서 하계에 발생하는 C. polykrikoides 적조는 한국남해 연안수와 쓰시마 난류 사이에 형성되는 열염전선과 밀접한 연관을 가지고 있음을 알 수 있었다.

• 한국수소및신에너지학회논문집
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• 제24권4호
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• pp.282-287
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• 2013

Hydrogen production from water using solar energy is attractive way to obtain clean energy resource. Among the various solar-to-hydrogen production techniques, a combination of a photovoltaic and an electrolytic cell is one of the most promising techniques in term of stability and efficiency. In this study, we show successful fabrication of precursor solution processed CIGS thin film solar cells which can generate high voltage. In addition, CIGS thin film solar cell modules producing over 2V of open circuit voltage were fabricated by connecting three single cells in series, which are applicable to water electrolysis. The operating current and voltage during water electrolysis was measured to be 4.23mA and 1.59V, respectively, and solar to hydrogen efficiency was estimated to be 3.9%.

• 한국유체기계학회 논문집
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• 제17권5호
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• pp.60-66
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• 2014

Most tidal current turbine designs are focused on medium and large scale for deep sea, less attention is paid in low water level channel, such as the region around the islands and costal sea. This study is to develop a horizontal axis tidal current turbine rotor blade which is applicable to low water level island region in southwest coastal region of Korea. In this study, the hydrofoil NACA63-415 and NACA63-817 are both adopted to analyze. The blade using NACA63-817 showed the higher maximum power coefficient and good performance at small TSR (Tip Speed Ratio), which gives the blade more advantages in operating at lower water level channel, where is characterized by the fast-flowing water. The cavitation pattern of hydrofoil is predicted by the CFD analysis and verified that the NACA63-817 is the appropriate hydrofoil in the test site of tidal current resource and the hydrofoil showed considerable performance in avoiding cavitation.

• 한국수소및신에너지학회논문집
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• 제29권6호
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• pp.549-558
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• 2018

The overall efficiency depend on the overpotential of the oxygen evolution reaction in alkaline water electrolysis. Therefore, it is necessary to research to reduce the oxygen evolution overpotential of electrodes. In this study, Ni-Zn-Fe electrodes were prepared by electroplating and the surface area was increased by Zn leaching process. Electroplating variables were studied to optimize the plating parameters(electroplating current density, pH value of electroplating solution, Ni/Fe content ratio). Ni-Zn-Fe electrode, which is electroplated in a modified Watts bath, showed 0.294 V of overpotential at $0.1A/cm^2$. That result is better than that of Ni and Ni-Zn plated electrodes. As the electroplating current density of the Ni-Zn-Fe electrode increased, the particle size tended to increase and the overpotential of oxygen evolution reaction decreased. As reducing pH of electroplating solution from 4 to 2, Fe content in electrode and activity of oxygen evolution reaction decreased.

• 신재생에너지
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• 제8권1호
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• pp.44-51
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• 2012

Due to a high tidal range of up to 10 m on the west coast of Korea, numerous tidal current projects are being planned and constructed. The turbine, which initially converts the tidal energy, is an important component because it affects the efficiency of the entire system. Its performance is determined by design variables such as the number of blades, the shape of foils, and the size of a hub. To design a turbine that can extract the maximum power on the site, the depth and duration of current velocity with respect to direction should be considered. Verifying the performance of a designed turbine is important, and requires a circulating water channel (CWC) facility. A physical model for the performance test of the turbine should be carefully designed and compared to results from computational fluid dynamics (CFD) analysis. In this study, a horizontal axis tidal current turbine is designed based on the blade element theory. The proposed turbine's performance is evaluated using both CFD and a CWC experiment. The sealing system, power train, measuring devices, and generator are arranged in a nacelle, and the complete TCP system is demonstrated in a laboratory scale.