• 세라미스트
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• 제22권2호
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• pp.182-188
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• 2019

Alternative energy sources to the systems using hydrocarbon fuels have been actively developed due to exhaustion of fossil fuels and issue of global warming by CO₂. Fuel cells have attracted great attentions to solve these issues as electricity can be produced with product of clean H₂O by using H₂-O₂ as a fuel. Besides, using reverse reactions make it possible to produce H₂ and O₂ gas from electrolysis of water. There are various fuel cells systems depending on the types of electrolyte, and in this mini-reviews, the main aim is to focus on perovskite oxides as a catalyst for oxygen-evolution reactions in alkaline electrolysis and its potential to application of alkaline electrolysis systems.

• Journal of Power Electronics
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• 제9권1호
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• pp.26-35
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• 2009

A high efficiency active clamp sepic-flyback converter is presented for fuel cell generation systems. The proposed converter is a superposition of a sepic converter mode and. flyback converter mode. The output voltages of the sepic converter mode and flyback converter mode can be regulated by the same PWM technique with constant frequency. By merging the sepic and flyback topologies, they can share the transformer, power MOSFET and active clamp circuit. The result has outstanding advantages over conventional active clamp DC-DC converters: high efficiency, high power density, and component utilization. Simulation results and experimental results are presented to verify the principles of operation for the proposed converter.

• 한국기후변화학회지
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• 제9권4호
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• pp.313-318
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• 2018

The growth rate of international aviation is expected to be higher than that of most industries and the proportion of carbon emissions from the aviation industry will become very significant as the year 2050 approaches. Constraining the growth of this industry is not desirable because it is essential for human welfare as well as the development of related industries. However, reduction of carbon due to aviation is not easy because it is difficult to improve fuel efficiency in a significant way. The ICAO (International Civil Aviation Organization), which is the main organization responsible for handling this problem, developed a program named CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation). The present study analyzes various strategies for countries and airlines to comply with CORSIA using a fuel-efficient system. We conclude that countries should improve their airspace utilization systems, airport facilities, and air navigation systems. Additionally, based on the results of a flight data analysis, airlines should improve their operational efficiency in terms of operations control, flight operation, and maintenance management.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2003년도 춘계학술발표대회 요약집
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• pp.56.1-56.1
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• 2003

• 신재생에너지
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• 제7권3호
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• pp.17-28
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• 2011

Biogas production and utilization are an emerging alternative energy technology. Biogas is produced from the biological breakdown of organic matter through anaerobic digestion. Biogas can be utilized for various energy sectors such as space heating, electricity generation and vehicle fuel. Especially, to be utilized as vehicle fuel, raw biogas needs to be upgraded that is mainly the removal of carbon dioxide to increase the methane content up to more than 95 ~ 97 vol% in some cases, similar to the composition of fossil-based natural gas. Usage of Biogas as a fuel of vehicles have an effect of reducing $CO_2$ emission compared to fossil fuels. Biomethane which is produced by upgrading of biogas is regarded as a good alternative energy and usage of clean energy is encouraged to deal with air pollution and waste management as well as production of clean energy. Recently, biogas projects for vehicle fuel are newly being launched and Korea government have also announced a plan for investment to develop biogas as a transport fuel. In this study, it is aimed to examine the potential feasibility of biomethane as a transport fuel. As a results, the status of biomethane, quality standard, quality characteristics, and upgrading technology of biogas were investigated to evaluate of biogas as a vehicle fuel of transportation.

• Advances in Energy Research
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• 제1권2호
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• pp.127-146
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• 2013

Torrefaction technologies convert assorted biomass feedstocks into energy-concentrated, carbon neutral fuel that is economically transported and easily ground for blending with fossil coals at numerous power plants around the world without needs to retrofit. Utilization of torrefied biomass in conventional electric generating units may be an increasingly attractive alternative for electricity generation as aging power plants in the world need to be upgraded or improved. This paper examines the economic feasibility of torrefaction in different scenarios by modeling torrefaction plants producing 136,078 t/year (150,000 ton/year) biocoal from wood and corn stover. The utilization of biocoal blends in existing coal-fired power plants is modeled to determine the demand for this fuel in the context of emerging policies regulating emissions from coal in the U.S. setting. Opportunities to co-locate torrefaction facilities adjacent to corn ethanol plants and coal-fired power plants are explored as means to improve economics for collaborating businesses. Life cycle analysis was conducted in parallel to this economic study and was used to determine environmental impacts of converting biomass to biocoal for blending in coal-fired power plants as well as the use of substantial flows of off-gasses produced in the torrefaction process. Sensitivity analysis of the financial rates of return of the different businesses has been performed to measure impacts of different factors, whether input prices, output prices, or policy measures that render costs or rewards for the businesses.

• Nuclear Engineering and Technology
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• 제23권3호
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• pp.352-362
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• 1991

가압 경수로의 노심 설계에 있어서 제한된 우라늄 자원의 효율적인 이용을 위한 다양한 방안으로 장주기 운전, 고연소도 및 저누출 장전 모형 통을 강구하고 있는 추세이다. 이러한 노심들은 원자로 운전 주기 전반에 걸친 공간적 출력 분포 제어와 잉여 반응도 제어를 위해 가연성 독물질을 사용하고 있다. 이와 관련하여 가연성 독물질 관리의 최적화 연구가 다각도로 진행되고 있다. 본 연구에서는 1990년도부터 국내 가압 경수로에 국산 핵연료가 장전되기 시작하면서 가도리니아 독봉을 사용하고 있으며 장차 주된 가연성 독물질로 쓰일 예정이므로 이에 대해서 분석을 수행하였다. 분석 결과 가도리니아 독봉은 열중성자 흡수 단면적이 매우 큰데서 기인한 특이한 연소 특성을 보이고 있다. 특히 집합체 내에서의 가도리니아 독봉의 위치에 따라 매우 다양한 출력 분포를 보이고 있다. 이러한 다양한 출력 분포 중에서 노심의 반경 방향 첨두 출력을 가능한 낮게하는 집합체 내에서의 가도리니아봉 위치 최적 선정을 위한 방법론을 제시하였다.

• Nuclear Engineering and Technology
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• 제23권2호
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• pp.165-173
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• 1991

가압경수로의 사용후핵연료를 CANDU 원자로에 재순환시키는, 이른바, 탄뎀 핵연료주기가 본 연구에서 다루어졌다. 이러한 방식으로 가압경수로의 사용후핵연료를 활용하는 것은 우라늄자원의 이용을 개선시킬뿐만 아니라 사용후핵연료 저장능력의 부족도 다소 해결할 수 있을 것이다. 핵연료를 재순환 시키는데 있어서는 CANDU 원자로의 수정을 최소화하는 방향으로 연구가 진행되었으며 본 연구에서는 9종의 핵연료가 고려되었다. 탄뎀 핵연료는 크게 핵연료재가공과 노심재구성의 두 분야로 나뉘어지는데, 핵연료 재가공의 경우, 가압경수로의 사용후핵연료는 처리되고 현재의 37 봉형 격자구조인 핵연료 다발에 맞도록 다시 성형가공되며 노심재구성의 경우, 가압경수로 사용후핵연료는 단지 격자 구조를 해체하고 CANDU의 격자길이에 맞춰 재구성만 된다. 각 탄뎀 핵연료 옵션에 대하여, 허용연소도와 출력분포를 계산하기 위해 노심연소계산이 수행되었다. 또한 경제성에 대한 접근으로 각 핵연료 옵션에 대한 핵주기비가 계산되었다. 그 결과 본 연구에서 다루어진 대부분의 탄뎀 핵연료 옵션이 경제성이 있었을 뿐만 아니라 기술적인 타당성이 있었다.

• 에너지공학
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• 제23권2호
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• pp.1-6
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• 2014

저등급석탄을 효율적으로 활용하기 위한 고품위화 기술에 대한 연구를 수행하였다. 저등급석탄을 건조시켜 고발열량 석탄으로 제조하는 과정에서 자연발화에 대한 안정화를 위해 중질유를 분무 코팅하는 방법을 적용하였다. 수분 30wt% 이상의 저등급석탄을 고품위화하여 6,000 kcal/kg 이상의 고발열량 석탄을 제조하였으며, 중질유 분무 코팅을 통해 자연발화에 대한 안정성을 확인하였다. 중질유 분무 코팅의 방법은 석탄을 건조시킨 후 분무 코팅하는 것이 가장 적절한 것으로 나타났으며, 자연발화에 대한 충분한 안정성을 갖기 위해서는 중질유를 2wt% 이상 석탄 표면에 흡착시켜야 하는 것으로 나타 났다.

• 한국수소및신에너지학회논문집
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• 제30권4호
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• pp.303-311
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• 2019

Reversible solid oxide fuel cell (RSOFC) has become a prospective device for energy storage and hydrogen production. Many studies have been conducted around the world focusing on system efficiency improvement and realization. The system should have not only high efficiency but also a certain level of simplicity for stable operation. External waste steam utilization was proved to remarkably increase the efficiency at solid oxide electrolysis system. In this study, RSOFC system coupled with waste steam was proposed and optimized in term of simplicity and efficiency. Ejector for fuel recirculation is selected due to its simple design and high stability. Three system configurations using ejector for fuel recirculation were investigated for performance of design condition. In parametric study, the system efficiencies at different current density were analyzed. The system configurations were simulated using validated lumped model in EBSILON(R) program. The system components, balance of plants, were designed to work in both electrolysis and fuel cell modes, and their off-design characteristics were taken into account. The base case calculation shows that, the system with suction pump results in slightly lower efficiency but stack can be operated more stable with same inlet pressure of fuel and air electrode.