• Current Photovoltaic Research
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• 제1권2호
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• pp.82-89
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• 2013

$Cu_2ZnSnS_4$ thin film have been fabricated by rapid thermal annealing of dc-sputtered metal precursor with Cu/ZnSn/Cu stack in sulfur ambient. A CZTS film with a good uniformity was formed at $560^{\circ}C$ in 6 min. $Cu_2SnS_3$ and $Cu_3SnS_4$ secondary phases were present at $540^{\circ}C$ and a trace amount of $Cu_2SnS_3$ secondary phase was present at $560^{\circ}C$. Single-phase large-grained CZTS film with rough surface was formed at $560^{\circ}C$. Solar cell with best efficiency of 4.7% ($V_{oc}=632mV$, $j_{sc}=15.8mA/cm^2$, FF = 47.13%) for an area of $0.44cm^2$ was obtained for the CZTS absorber grown at $560^{\circ}C$ for 6 min. The existence of second phase at lower-temperature annealing and rough surface at higher-temperature annealing caused the degradation of cell performance. Also poor back contact by void formation deteriorated cell performance. The fill factor was below 0.5; it should be increased by minimizing voids at the CZTS/Mo interface. Our results suggest that CZTS absorbers can be grown by rapid thermal annealing of metallic precursors in sulfur ambient for short process times ranging in minutes.

• 상하수도학회지
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• 제30권4호
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• pp.449-457
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• 2016

In this study, the effectiveness of electrodialysis in removing inorganic arsenic from groundwater was investigated. To evaluate the feasibility of the electrodialysis, operating parameters such as treatment time, feed concentration, applied voltage and superficial velocity were experimentally investigated on arsenic removal. The higher conductivity removal and arsenic removal efficiency were obtained by increasing applied voltages and operation time. An increase of salinity concentrations in arsenic polluted groundwater exerted no effects on the arsenic separation ratios. Arsenic polluted waters were successfully treated with stack voltages of 1.8 ~ 2.4 V/cell-pair to approximately 93.4% of arsenic removal. Increase flow rate in diluate cell gave positive effect to removal rate. However, increase of superficial velocity in the concentrated cell exerted no effects on either the conductivity reduction or on the separation efficiency. Hopefully, this paper will provide direction in selecting appropriate operating conditions of electrodialysis for arsenic removal.

• 한국자동차공학회논문집
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• 제25권2호
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• pp.157-166
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• 2017

The Fuel Cell Electric Vehicle(FCEV) is recently evolving into a new trend in the automobile industry due to its relatively higher efficiency and zero greenhouse gas(GHG) emission in the tailpipe, as compared to that of the conventional internal combustion engine vehicles. However, it is important to analyze the whole process of the hydrogen's life cycle(from extraction of feedstock to vehicle operation) in order to evaluate the environmental impact of introducing FCEV upon recognizing that the hydrogen fuel, which is used in the fuel cell stack, is not directly available from nature, but instead, it should be produced from naturally available resources. Among the various hydrogen production methods, ${\sim}54.1%^{8)}$ of marketed hydrogen in Korea is produced from naphtha cracking process in the petrochemical industry. Therefore, in this study, we performed a well-to-wheels(WTW) analysis on the hydrogen fuel cycle for the FCEV application by using the GREET program from the US Argonne National Laboratory with Korean specific data. As a result, the well-to-tank and well-to-wheel GHG emissions of the FCEV are calculated as 45,638-51,472 g $CO_2eq/GJ$ and 65.0-73.4 g $CO_2eq/km$, respectively

• 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.

• Korean Chemical Engineering Research
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• 제59권1호
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• pp.6-10
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• 2021

PEMFC(Proton Exchange Membrane Fuel Cell) 고분자 막의 shorting 저항(Shorting Resistance, SR)은 고분자 막의 내구성에 관한 중요한 지표다. SR이 감소하면 shorting 전류(Shorting Current, SC)가 증가하여 내구성과 성능이 감소하고, SR이 약 0.1 kΩ·㎠ 이하가 되면 shorting이 발생하여 온도가 급상승하고 MEA(Membrane Electrode Assembly)를 연소시켜 스택 구동이 종료된다. Shorting 현상을 방지하기 위해서는 SR을 제어해야 하므로 SR에 영향을 주는 조건들에 대해서 연구하였다. SR 측정방법들에서도 차이가 있어서 DOE(Department of Energy)와 NEDO(New Energy and Industrial Technology Development Organization) 방법을 개선한 SR 측정법을 제시하였다. 상대습도와 온도, 셀 체결 압이 상승하면 SR이 감소함을 확인하였다. 고분자 막의 가속내구 평가과정에서 마지막 단계에서 SR이 0.1 kΩ·㎠ 이하로 급감해 수소투과전류밀도가 15 mA/㎠ 이상이 되었고, 이 MEA를 해체 후 SEM(Scanning Electron Microscope) 분석한 결과 고분자 막 내부에 백금이 많이 분포함을 보였다.

• 한국융합학회논문지
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• 제7권6호
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• pp.13-21
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• 2016

본 논문은 현재 진행 중인 대한민국 남부지역에 위치한 대학 내 스마트에너지캠퍼스 마이크로그리드에서 대학 내 빌딩에 설치될 수소전기분해 이용 연료전지 시스템 운용을 위한 선행 연구로써 고분자전해질막 전기분해(PEMWE)과 고분자전해질막 연료전지(PEMFC) 장치에서 동시에 온도변화 효과를 연구하고자 한다. 전반적으로 실험실에서 50W 고분자전해질막 연료전지(PEMFC)을 사용하여 수행하였다. 모니터링 프로세스는 무선 로라 노드와 게이트웨이 네트워크를 구성하여 실행하였다. 그리고 PEMWE와 PEMFC에 대한 수학적 모델링과 운전 알고리즘을 제안하였으며 제안한 모델에서 PEMWE는 낮은 발열 기준에서 효율이 더 높음을, 반면에 PEMFC는 높은 발열기준에서 효율이 더 높음을 을 알 수 있었다. 향후 대학 구내 빌딩에 설치될 실증시스템 성능을 높이기 위해 PEMWE와 PEMFC의 온도와 압력을 모니터링, 통신 및 제어 등 연구개발을 통하여 구현할 예정이다.

• 한국항공우주학회지
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• 제41권3호
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• pp.226-232
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• 2013

소형 무인항공기의 동력장치로 연료전지 시스템을 적용하기 위해 화학수소화합물 수소 저장방법을 이용한 소형 수소 발생 제어장치를 설계하였다. 효율이 높은 소형/경량 수소 발생 제어장치를 설계하기 위하여 $NaBH_4$ 수용액 공급 유량에 따른 Co-B 촉매의 수소 전환율을 확인하였고, 100W 스택의 최대 수소 발생량에 적합한 Co-B 촉매양을 제안하였다. 효율적인 연료 소모를 위해 Dead-end 방식의 스택을 선택하였고, 수소 발생 제어장치 내부 압력을 이용한 펌프 on/off 제어로 수소 생성량을 제어하였다. 소형 수소 발생 제어장치를 이용한 연료전지 시스템의 각 작동구간에서 안정된 운전을 확인하였다. 장시간 운전 실험을 통하여 최대 7시간 운전이 가능하며, 임의의 비행 프로화일에 요구되는 추력 프로화일은 최소 4시간 이상 조정 가능함을 확인하였다.

• 대한의용생체공학회:의공학회지
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• 제39권5호
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• pp.220-228
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• 2018

The internal resistance of microbial fuel cell (MFC) using stainless steel skein for oxidizing electrode was investigated and the factors affecting the voltage generation were identified. We also investigated the effect of power management system (PMS) on the usability for MFC and the removal efficiency of organic pollutants. The performance of a stack microbial fuel cell connected with (PMS) or PMS+LED was analyzed by the voltage generation and organic matter reduction. The maximum power density of the unit cells was found to be $5.82W/m^3$ at $200{\Omega}$. The maximum current density was $47.53A/m^3$ without power overshoot even under $1{\Omega}$. The ohmic resistance ($R_s$) and the charge transfer resistance ($R_{ct}$) of the oxidation electrode using stainless steel skein electrode, were $0.56{\Omega}$ and $0.02{\Omega}$, respectively. However, the sum of internal resistance for reduction electrode using graphite felts loaded Pt/C catalyst was $6.64{\Omega}$. Also, in order to understand the internal resistance, the current interruption method was used by changing the external resistance as $50{\Omega}$, $300{\Omega}$, $5k{\Omega}$. It has been shown that the ohm resistance ($R_s$) decreased with the external resistance. In the case of a series-connected microbial fuel cell, the reversal phenomenon occurred even though two cells having the similar performance. However, the output of the PMS constantly remained for 20 hours even when voltage reversal occurred. Also the removal ability of organic pollutants (SCOD) was not reduced. As a result of this study, it was found that buffering effect for a certain period of time when the voltage reversal occurred during the operation of the microbial fuel cell did not have a serious effect on the energy loss or the operation of the microbial fuel cell.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.91.2-91.2
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• 2010

SOFC는 높은 반응온도($600{\sim}1000^{\circ}C$)에서 작동되어 발전효율이 높고 다양한 연료를 사용할 수 있는 것이 장점이다. 하지만 고온에서의 운전은 구성요소의 열변형과 온도구배에 의한 전극촉매의 열화 그리고 밀봉재의 수명에 영향을 주어 결국 스택의 내구성을 감소시킨다. 특히 스택의 온도구배가 심화되면 국부적인 Hot spot를 형성하여 셀에 심각한 손상을 주게 된다. 본 과제에서는 SOFC 스택의 온도구배를 완화시키기 위한 내부개질기의 개발 및 고온용 분리판 소재의 정밀성형기술을 확보하고자 한다. 열/유동해석을 통하여 반응가스의 농도, 유속, 구조변경 등 내부개질기 온도구배에 대한 주요인자를 확인하였고, 장기 운전평가를 통하여 개질 촉매의 고온 활성 및 내구성에 대한 성능평가를 진행 중이다. 분리판의 경우, 고온용 소재(페라이트계 스테인레스)에 대한 기초실험을 실시하여 성형품질의 주요 인자를 파악하였으며 Proto-type 금형 설계 및 개발을 통하여 성형 기초기술을 확보하였다. 그리고 스택 내부온도를 구현할 수 있는 시뮬레이터를 설계 중에 있으며 이를 이용하여 개발된 내부개질기 및 분리판을 스택 운전환경에서 평가할 예정이다.

• 한국수소및신에너지학회논문집
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• 제17권4호
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• pp.403-408
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• 2006

The plate reformer consisting of combustion chamber and reforming chamber for 25 kW MCFC stack has been operated and computational fluid dynamics was applied to estimate reactions and thermal fluid behavior in the reformer. The methane air 2-stage reaction was assumed in the combustion chamber, and three step steam reforming reactions were included in the calculation. Flow uniformity, reaction rate and species distribution, and temperature distribution were analyzed. In particular, temperature distribution was compared with the measurements to show good agreement in the combustion chamber, however, inappropriate agreement in the reformer chamber.