• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.469-476
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• 2015

The purpose of this work is to investigate main factors to design a solid-state hydrogen stroage system with magnesium hydride with 10 wt% graphite using numerical simulation tools. The heat transfer characteristic of this material was measured in order to perform the highly reliable simulation for this system. Based on the measured effective thermal conductivity, a transient heat and mass transfer simulation revealed that the total performance of hydrogen storage system is prone to depend on heat and mass transfer behaviors of hydrogen storage medium instead of its inherent kinetic rate for hydrogen adsorption. Furthermore, we demonstrate that the thermodynamic aspect between equlibrium presssure and temperature is one of key factor to design the hydrogen storage system with high performance using magnesium hydride.

• 전기학회논문지
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• 제62권7호
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• pp.1045-1052
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• 2013

In this study we deal with design procedures for the flywheel energy storage system that has the capacity to store the regenerative energy produced from the railway vehicles. The flywheel energy storage system (FESS) stores the regenerative electrical energy into the high speed rotational flywheel, by conversion the electrical energy into the mechanical rotational energy. Thus the FESS is composed of the energy conversion components, such as the motor and generator, mechanical support components, such as the rotational rotor, the magnetic bearings to support the rotor, and the digital controller to control the air gap between the rotor and the magnetic bearings. In this paper the design procedures for the rotor operating at the rigid mode and the magnetic bearings to support the rotational rotor without contact are presented.

• 전력전자학회논문지
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• 제17권6호
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• pp.523-531
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• 2012

This paper proposes a high efficiency power conversion system for battery-ultracapacitor hybrid energy storages. The proposed system has only one bidirectional dc-dc converter for hybrid power source with batteries and ultracapacitors. The hybrid power source has bidirectional switching circuits for selecting one energy storage device. Bidirectional power flow between the energy storage device and high voltage capacitor can be controlled by one bidirectional converter. An asymmetrical switching method is applied to the bidirectional converter for high power efficiency. Switching power losses are reduced by zero-voltage switching of power switches. System operation and design considerations are presented. The experimental results are provided to verify the performance of the proposed system.

• 한국세라믹학회지
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• 제55권4호
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• pp.307-324
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• 2018

Rechargeable lithium-ion batteries (LIBs) have been rapidly expanding from IT based applications to uses in electric vehicles (EVs), smart grids, and energy storage systems (ESSs), all of which require low cost, high energy density and high power density. The increasing demand for LIBs has resulted in increasing price of the lithium source, which is a major obstacle to wider application. To date, the possible depletion of lithium resources has become relevant, giving rise to the interest in Na-ion batteries (NIBs) as promising alternatives to LIBs. A lot of transition metal compounds based on conversion-alloying reaction have been extensively investigated to meet the requirement for the anodes with high energy density and long life-time. In-depth understanding the electrochemical reaction mechanisms for the transition metal compounds makes it promising negative anode for NIBs and provides feasible strategy for low cost and large-scale energy storage system in the near future.

• 한국수소및신에너지학회논문집
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• 제17권3호
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• pp.317-323
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• 2006

Electric conductive material should be homogeneously mixed with sulfur in sulfur electrode fabrication of lithium/sulfur battery, because sulfur is electric insulator. In this paper electrochemical properties of Li/S battery was studied with various compositions of sulfur electrodes. When content of sulfur changed from 40 wt.% to 80 wt.%, the 60 wt.% sulfur electrode showed the maximum capacity of 1489 mAh/g-sulfur. Electrochemical properties of Li/S battery using 60 wt.% sulfur was also investigated with various carbon contents. The discharge capacity changed as a function of carbon contents. The optimum composition was 25 wt.% carbon for 60 wt.% sulfur electrode.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2004년도 수소연료전지공동심포지움 2004논문집
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• pp.65-70
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• 2004

• 청정기술
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• 제13권4호
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• pp.287-292
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• 2007

상용 알루미나($Al_2O_3$)에 담지된 $M/Al_2O_3$ (M = Mn, Fe, Co, Ni, Cu) 촉매를 함침법에 의해 제조하였으며, 이를 에탄을 자열개질반응에 의한 수소제조에 적용하였다. 각각의 촉매는 고유한 금속상을 가지는 것으로 나타났으며, 생성물의 분포는 활성금속의 종류에 크게 의존하였다. 제조된 촉매 중에서, $M/Al_2O_3$ 및 Co/$Co/Al_2O_3$는 에탄을 자열개질반응에서 매우 우수한 촉매활성을 보였다. 그러나 두 촉매상에서의 반응메커니즘은 서로 다른 것으로 나타났다. $Ni/Al_2O_3$ 촉매는 $500^{\circ}C$의 반응온도에서 100%의 에탄올 전환율을 보였으나, 수소 선택도에서는 시간에 따라 급격한 저하현상을 나타내었다. 한편 $Co/Al_2O_3$ 촉매는 수소 선택도 면에서 우수한 활성을 보였으나, 에탄올 전환율이 저조하여 수소 수율에는 큰 변화가 나타나지 않았다.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2004년도 수소연료전지공동심포지움 2004논문집
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• pp.229-232
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• 2004

• 한국태양에너지학회 논문집
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• 제21권3호
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• pp.1-8
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• 2001

고온의 태양열을 저장하기 위한 한 방편으로 화학반응을 이용한 태양에너지의 화학에너지로의 변환공정을 고려하였다. 태양에너지의 저장은 메탄의 수증기 개질반응으로 선정하였으며, 이 흡열반응에서 메탄의 전화율 특성을 살펴보았다. 반응기는 직경, 6.25 mm, 그리고 길이 30 cm 인 stainless steel을 코일형태로 제작하였다. 반응온도 범위내에서 메탄의 전화율은 반응온도에 따라서 선형적으로 증가하였으며 반응온도 $500^{\circ}C{\sim}900^{\circ}C$ 범위에서 메탄의 전화율은 약 $60%{\sim}90%$ 로 측정되었다. 이 실험을 통하여 태양열 저장을 위한 메탄의 수증기 개질반응의 타당성을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제30권1호
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• pp.14-20
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• 2019

The power to gas (P2G) is one of the energy storage technologies that can increase the storage period and storage capacity compared to the existing battery type. One of P2G technologies produces hydrogen by decomposing water from renewable energy (electricity) and the other produces $CH_4$ by reacting hydrogen with $CO_2$. The objective of this study is the reaction of $CO_2$ methanation which synthesized methane by reacting carbon dioxide and hydrogen. The effect of $CO_2$ conversion and $CH_4$ selectivity on reaction temperature, pressure, and methane contents over 40% Ni catalyst was mainly investigated throughout this study. As a result, the activity of this catalyst appeared to be the highest in $CH_4$ yield at around $400^{\circ}C$ and the selectivity of $CH_4$ increased with increasing reaction pressure. The methane content was not significantly influenced below 3% of all componets. As the space velocity increases from 10,000 to 30,000/hr, the $CO_2$ conversion rate tends to decrease.