• 전기화학회지
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• 제16권3호
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• pp.111-122
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• 2013

나트륨 유황전지(NAS)는 대용량 에너지 저장시스템(energy storage system, ESS) 중 하나로서, 최근 풍력에너지, 태양에너지, 해양에너지 등 그린재생에너지의 사용증가로 ESS에 대한 수요가 급증함에 따라 NAS 전지에 대한 관심이 고조되고 있다. NAS 전지는 에너지 밀도가 높고(납 축전지밀도의 3배), 사이클 수명이 길고, 자가방전이 없어 대용량 전력저장 시스템에 적합하다. NAS 전지는 양극으로 황(Sulfur), 음극으로 나트륨(Na), 고체전해질 및 분리막으로 ${\beta}$"-알루미나($Al_2O_3$)로 구성되어 있고, 양극 활물질인 황은 부도체이기 때문에 도전재인 탄소섬유(carbon felt)에 함침시켜 양극으로 사용해야 함으로, 양극재 구성 및 특성은 전지성능에 상당한 영향을 미치게 된다. 따라서 본 논문에서는 NAS 전지의 구성, 다황화나트륨($Na_2S_x$, 방전생성물) 및 양극재의 특성, 전지 성능에 미치는 영향인자들에 대해서 알아보고자 한다.

• 디지털콘텐츠학회 논문지
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• 제18권6호
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• pp.1199-1205
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• 2017

산업화의 급격한 진전으로 인한 에너지 소비가 세계적으로 증가되면서 새로운 에너지 저장 소자에 대한 개발의 필요성이 늘고 있으며, 이에 빠른 충 방전 시간과 반영구적으로 사용이 가능한 슈퍼커패시터에 대한 연구가 활발히 진행 중이다. 본 연구에서는 수열반응(Hydrothermal) 제조법을 이용하여 기판인 탄소섬유(carbon cloth)에 비정질의 이산화망간($MnO_2$)을 도포하여 슈퍼커패시터를 제작하였다. 탄소섬유에 Fe 이온이 도핑 된 이산화망간을 결합한 전극으로 이루어진 슈퍼커패시터의 특성 파악을 위해 전기주사현미경(SEM), X-ray 회절분석(XRD), 그리고 X-ray 분광 분석(EDX)을 실시하였다. 또한, 1 M의 $Na_2SO_4$ 전해질에서 순환전압전류법(Cyclic Voltammetry)과 정전류충전법(Galvanostatic charge-discharge)을 통해 슈퍼커패시터의 전기화학적 특성을 조사하였으며, 이를 통해 전류밀도 1 A/g에서 정전용량이 163 F/g 임을, 그리고 1000 회의 충 방전 후 수명 측정 시에 안정적으로 87.34%가 유지됨을 확인하였다.

• 방사성폐기물학회지
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• 제7권4호
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• pp.229-236
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• 2009

우리나라에서 발생하는 사용후핵 연료를 CANDU형과 PWR형 2종류로 구분한다. PWR형 사용후핵 연료의 경우 적절한 공정을 거쳐 원료물질로 다시 사용할 수 있는 물질을 많이 포함하고 있어 재활용 공정을 고려할 수 있다. CANDU형 사용후핵 연료는 천연 우라늄을 원료물질로 사용하고 있어 재활용 가능성이 거의 없으므로 직접 처분을 고려하고 있다. 본 논문에서는 PWR형과 CANDU형 사용후핵연료 모두를 직접 처분하는 개념으로 개발한 한국형 사용후핵연료 처분시스템을 바탕으로 CANDU형 사용후핵연료 처분 시스템을 향상시키는 방안을 도출하고자 하였다. 이를 위하여, 현재 원자력발전소에서 사용하고 있는 사용후핵연료 60 다발(Bundle) 용량의 저장바스켓을 포장 활용하는 방안으로 처분용기 개념을 개선하였다. 이들 개선한 처분용기를 기반으로 하여 사용후핵연료의 심지층 처분시스템에 있어서 주요한 제한요건인 폐기물로부터 발생된 열로 인하여 완충재의 온도가 $100^{\circ}C$를 넘지 않도록 하는 요건을 만족시키면서 효율을 향상시킨 처분시스템 개념을 제시하였다. 제시한 처분 시스템 개념들은 장기저장 및 회수성이 용이한 방안을 도입한 개념과 개선한 처분용기를 1개 처분공에 2단으로 처분하는 것으로서 이들 개념을 기존 한국형 처분시스템과 효율성 측면 에서 비교 분석하였다. 본 연구를 통하여 얻은 CANDU 사용후핵연료 처분개념은 단위면적당 열효율, U-density, 처분면적, 굴착량, 완충재 및 폐쇄 물질량을 30~40 %까지 효율을 향상시킬 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 제17회 워크샵 및 추계학술대회
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• pp.634-637
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• 2005

Hydrogen adsorption mechanism onto the porous metal-organic frameworks (MOFs) has been studied by density functional theory calculation. The selected functionals for the predict ion of interact ion energies between hydrogen and potential adsorption sites of MOF was utilized after the evaluation with the various functionals for interaction energy of $H_2C_6H_6$ model system the adsorption energy of hydrogen molecule into MOF was investigated with the consideration of the favorable adsorption sites and the orientations. We also calculated the second favorable adsorption sites by geometry optimization using every combination of two first absorbed hydrogen molecules. Based on the calculation of first and second adsorption sites and energies, the hydrogen adsorption into MOF follows a cooperative mechanism in which the initial metal sites initiate the propagation of the hydrogen adsorption on the whole frameworks. In addition, it was found that the interaction strength between the simple benzene ring with hydrogen is significantly reinforced when the benzene ring has been incorporated into the framework of MOFs.

• Advances in Energy Research
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• 제7권1호
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• pp.21-34
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• 2020

Energy storage devices have received a keen interest throughout the world due to high power consumption. A large number of research activities are being conducted on electrochemical double layer capacitors (EDLCs) because of their high power density and higher energy density. In the present study, an EDLC was fabricated using natural graphite based electrodes and ionic liquid (IL) based gel polymer electrolyte (GPE). The IL based GPE was prepared using the IL, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1E3MITF) with the polymer poly(vinyl chloride) (PVC) and the salt magnesium trifluoromethanesulfonate (Mg(CF₃SO₃)₂ - MgTF). GPE was characterized by electrochemical impedance spectroscopy (EIS), DC polarization test, linear sweep voltammetry (LSV) test and cyclic voltammetry (CV) test. The maximum room temperature conductivity of the sample was 1.64 × 10^-4 Scm^-1. The electrolyte was purely an ionic conductor and the anionic contribution was prominent. Fabricated EDLC was characterized by EIS, CV and galvanostatic charge discharge (GCD) tests. CV test of the EDLC exhibits a single electrode specific capacitance of 1.44 Fg^-1 initially and GCD test gives 0.83 Fg^-1 as initial single electrode specific discharge capacitance. Moreover, a good stability was observed for prolonged cycling and the device can be used for applications with further modifications.

• Journal of Electrochemical Science and Technology
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• 제8권3호
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• pp.236-243
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• 2017

A fixed-bed zinc/nickel redox flow battery (RFB) is designed and developed. The proposed cell has been established in the form of a fixed bed RFB. The zinc electrode is immersed in an aqueous NaOH solution (anolyte solution) and the nickel electrode is immersed in the catholyte solution which is a mixture of potassium ferrocyanide, potassium ferricyanide and sodium hydroxide as the supporting electrolyte. In the present work, the electrode area has been maximized to $1500cm^2$ to enforce an increase in the energy efficiency up to 77.02% at a current density $0.06mA/cm^2$ using a flow rate $35cm^3/s$, a concentration of the anolyte solution is $1.5mol\;L^{-1}$ NaOH and the catholyte solution is $1.5mol\;L^{-1}$ NaOH as a supporting electrolyte mixed with $0.2mol\;L^{-1}$ equimolar of potassium ferrocyanide and potassium ferricyanide. The outlined results from this study are described on the basis of battery performance with respect to the current density, velocity in different electrolytes conditions, energy efficiency, voltage efficiency and power of the battery.

• KIEE International Transactions on Electrophysics and Applications
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• 제4C권3호
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• pp.96-100
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• 2004

The Nd： YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd： YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3％ error range in 600[V].

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1311_1312
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• 2009

In this article, current state of development of energy storage system using superconductor was summarized. As a result of continuous efforts, high critical current density exceeding $10^4\;A/cm^3$ at 77K and strong levitation capacity have been achieved in Y-Ba-Cu-O superconductor which is fabricated by melting technique. Various applications using the levitation properties of high-Tc superconductor is expected to come true in near future.

• Transactions on Electrical and Electronic Materials
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• 제6권4호
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• pp.186-189
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• 2005

We have fabricated superconducting HTSC ceramic thick films by chemical process. c-axis oriented HTSC thick films have been attempted bi-axially textured Ni tapes. The x-ray diffraction pattern of the HTSC thick films contained superconducting phase crystal. The critical temperature and critical current density was 110K.

• 한국정밀공학회지
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• 제16권6호
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• pp.141-147
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• 1999

Optical disk technology with a laser beam for data recording and retrieval is one of the most promising route for high density information storage in multimedia era. As the storage density and data transfer rates are increased, mechanical issues, mainly noise and vibration, become critical. Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. Over the years an enormous effort has been put into developing procedures to provide properties of rubber components with complex shape and under pre-deformed state. In this paper, non-linear large deformations of a rubber mount for optical disk drive were investigated using the finite element method. A tension test of rubber material was performed, to calculate a strain energy function. According to the pre-deformed state, the variation of rubber mount stiffness were calculated and the reliability of numerical results were checked by compared with the measuring the deflection values. Also, the effects of the pre-deformed rubber mount on the system dynamic characteristics were investigated and the relation between the static stiffness variation of rubber mount and the natural frequence variation of system was discussed.