• 세라미스트
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• 제23권2호
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• pp.184-199
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• 2020

The solid oxide fuel cells (SOFCs) are the one of the most promising energy conversion devices which can directly convert chemical energy into electric power with high efficiency and low emission. The lowering operating temperature below 800 ℃ has been considered as the mostly considerable research and development for commercialization. The major issue is to maintain reasonably high performance of SOFCs at reduced temperatures due to increment of polarization resistance of electrodes and electrolyte. Thus, the alternative materials with high catalytic activities and fast oxygen ion conductivity are required. For recent advances in electrolyte materials and technology, newly designed, highly conductive electrolyte materials and structural engineering of them provide a new path for further reduction in ohmic polarization resistance from electrolytes. Here, a powerful strategy of the bilayer concept with various oxide electrolytes of SOFCs are briefly reviewed. These recent developments also highlight the need for electrolytes with greater conductivity to achieve a high performance, thus providing a useful guidance for the rational design of cell structures for SOFCs. Moreover, cell design, materials compatibility, processing methods, are discussed, along with their role in determining cell performance. Results from state-of-the-art SOFCs are presented, and future prospects are discussed.

• 한국재료학회지
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• 제7권3호
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• pp.180-187
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• 1997

평판형 고체산화물 연료전지용 연결재료로 사용되는 $La_{0.68}Ca_{0.32}Cr_{0.97}O_{3}$박막의 소결조건을 변화시키며 곡강도, 상대밀도 및 전기전도도를 측정하였다. 그 결과 $La_{0.68}Ca_{0.32}Cr_{0.97}O_{3}$의 곡강도는 소결온도와 소결시간이 증가할수록 증가하였고, 상대밀도는 $1400^{\circ}C$, 5시간이상 소결한 시편에서 94%이상을 얻었다. $La_{0.68}Ca_{0.32}Cr_{0.97}O_{3}$의 저온소결은 $Ca_{m}(C_{r}O_{4})_{n}$에 의해 이루어졌음이 관찰되었다. 또한 $La_{0.68}Ca_{0.32}Cr_{0.97}O_{3}$의 전기전도도는 $1400^{\circ}C$, 7시간 소결한 시편의 경우 $1000^{\circ}C$에서 약 100/cm이상을 얻었다.

• 한국수소및신에너지학회논문집
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• 제31권6호
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• pp.596-604
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• 2020

Solid oxide electrolysis cell (SOEC) attracts much attention because of its high energy efficiency among many water-electrolysis technologies. SOEC operates at temperatures above 700℃, so that the water required for water-electrolysis must be supplied in the form of steam. When the steam to be supplied to the SOEC is generated by the SOEC system itself, an enormous amount of latent heat is required to vaporize the water, so additional energy must be supplied to the SOEC system. On the other hand, if the steam can be supplied from the outside, a small amount of energy is required to raise the temperature of the low temperature steam, so that the SOEC system can be operated without additional energy supply from outside, which enables efficient water-electrolysis. In this study, we figure out the size of heat exchanger for various steam temperature and effectiveness of heat exchanger, and propose the energy efficiency of the system.

• 대한금속재료학회지
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• 제56권12호
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• pp.893-899
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• 2018

In the present study, we investigated the sulfur poisoning of the Ni anode in solid oxide fuel cells (SOFCs) as a function of operating conditions. Anode supported cells were fabricated, and sulfur poising tests were conducted as a function of current density, $H_2S$ concentration and humidity in the anode gas. The voltage drop was significant under the higher current density (${\sim}714mA/cm^2$) condition, while it was much reduced under the lower current density (${\sim}389mA/cm^2$) condition, at 100 ppm of $H_2S$. A secondary voltage drop, which occurred only at the high current density, was attributed to Ni oxidation in the anode. Thus, operation at high current density with high $H_2S$ concentration may lead to permanent deterioration in the anode. The effect of water content (10%) on the sulfur poisoning was also investigated through a constant current test (${\sim}500mA/cm^2$) at 10 ppm of $H_2S$. The cell operating with 10% wet anode gas showed a much smaller initial voltage drop, in comparison with a dry anode gas. The present study indicates that operating conditions, such as gas humidity and current density, should be carefully taken into account, especially when fuel cells are operated with $H_2S$ containing fuel.

• 한국가시화정보학회지
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• 제19권2호
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• pp.56-62
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• 2021

Solid oxide fuel cells (SOFCs) is the high efficiency fuel cell operating at high temperatures ranging from 700-1000℃. Design of the flow paths of the fuel and air in SOFCs is important to improve cell performance and prevent cell degradation. However, the uneven distribution of current density in the traditional type having one inlet and outlet causes cell degradation. In this regard, the parallel flow path with two inlet and outlets was designed and compared to the traditional type based on computational fluid dynamics (CFD) simulation. To check the cell performance, hydrogen distribution, velocity distribution and current density distribution were monitored. The results validated that the parallel designs with two inlets and outlets have a higher cell performance compared to the traditional design with one inlet and outlet due to a larger reaction area. In case of uniform-type paths, more uniform current density distribution was observed with less cross-sectional variation in flow paths. In case of contracted and expanded inflow paths, significant improvement of performance and uniform current density was not observed compared to uniform parallel path. Considering SOFC cell with uniform current density can prevent cell degradation, more suitable design of SOFC cell with less cross-sectional variation in the flow path should be developed. This work can be helpful to understand the role of flow distribution in the SOFC performance.

• 신재생에너지
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• 제18권2호
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• pp.40-49
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• 2022

In this study, the phase and electrochemical properties of Co and Ti substituted layered perovskites SmBaCo_2-xTi_xO_5+d (x=0.5, 0.7, 1.0, 1.1, 1.3, and 1.5) were analyzed, and their application as electrodes in solid oxide fuel cells (SOFCs) were evaluated. After calcination at 1300℃ for 6 h, a single phase was observed for two compositions of the SmBaCo_2-xTi_xO_5+d oxide system, SmBaCoTiO_5+d (x=1.0) and SmBaCo_0.9Ti_1.1O_5+d (x=1.1). However, the phases of SmBaCoTiO_5+d (SBCTO) and SmTiO₃ coexisted for compositions with x≥1.3 (Ti content). In contrast, for compositions of x≤0.7, the SmBaCo₂O_5+d phase was observed instead of the SmTiO₃ phase. To evaluate the applicability of these materials as SOFC electrodes, the electrical conductivities were measured under various atmospheres (air, N₂, and H₂). SBCTO exhibited stable semi-conductor electrical conductivity behavior in an air and N₂ atmosphere. However, SBCTO showed insulator behavior at temperatures above 600℃ in a H₂ atmosphere. Therefore, SBCTO may only be used as cathode materials. Moreover, SBCTO had an area specific resistance (ASR) value of 0.140 Ω·cm² at 750℃.

• 한국수소및신에너지학회논문집
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• 제33권6호
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• pp.707-714
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• 2022

Hydrogen production using solid oxide electrolysis cells (SOEC) is a promising technology because of its efficiency, cleanness, and scalability. Especially, high-power SOEC system has received a lot of attention from researchers. This study compared and analyzed the low-power and high-power SOEC system in term of economic. By using revenue requirement method, levelized cost of hydrogen (LCOH) was calculated for comparison. In addition, the sensitivity analysis was performed to determine the dependence of hydrogen cost on input variables. The results indicated that high-power SOEC system is superior to a low-power SOEC system. In the capital cost, the stack cost is dominant in both systems, but the electricity cost is the most contributed factor to the hydrogen cost. If the high-power SOEC system combines with a nuclear power plant, the hydrogen cost can reach 3.65 $/kg when the electricity cost is 3.28 ¢/kWh and the stack cost is assumed to be 574 $/kW.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.306-309
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• 2005

One of the most critical issues in sol id oxide fuel cell (SOFC)running on hydrocarbon fuels is the risk of carbon formation from the fuel gas. The simple method to reduce the risk of carbon formation from the reactions is to add steam to the fuel stream, leading to the carbon gasification react ion. However, the addition of steam to fuel is not appropriate for the auxiliary power unit (APU) and potable power generation (PPG) systems due to an increase of complexity and bulkiness. In this regard, many researchers have focused on so-called 'direct methane' operation of SOFC, which works with dry methane without coking. However, coking can be suppressed only by the operation with a high current density, which may be a drawback especially for the APU and PPG systems. The single chamber fuel cell (SC-SOFC) is a novel simplification of the conventional SOFC into which a premixed fuel/air mixture is introduced. It relies on the selectivity of the anode and cathode catalysts to generate a chemical potential gradient across the cell. Moreover it allows compact and seal-free stack design. In this study, we fabricated honeycomb type mixed-gas fuel cell (MGFC) which has advantages of stacking to the axial direction and increasing volume power density. Honeycomb-structured SOFC with four channels was prepared by dry pressing method. Two alternative channels were coated with electrolyte and cathode slurry in order to make cathodic reaction sites. We will discuss that the anode supported honeycomb type cell running on mixed gas condition.

• 한국추진공학회지
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• 제23권1호
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• pp.116-123
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• 2019

열전지의 전해질은 용융염이 주성분이라서 용융염 전지라고도 불린다. 용융염 전해질은 평소에는 전기가 흐르지 않는 고체이지만, 화약 열원에 의해 녹으면 탁월한 이온 전도체가 된다. 따라서 열전지는 일종의 화약 전지이다. 화약의 열에너지로 용융염 전해질을 녹여야만 비로소 작동하게 되기 때문이다. 열전지에 사용되는 파이로테크닉 부품은 착화기, 점화스트립, 열원이 있다. 이들 파이로테크닉 부품은 극심한 환경조건에서도 안정적으로 전원을 공급해야 하는 유도 포탄용 열전지의 신뢰도는 물론 성능에도 큰 영향을 미친다. 노치형 착화기는 열원 착화 확률이 높았고, 필름형 착화기는 안전성을 향상시키는 것으로 나타났다. 열지에 금속 산화물 첨가를 통해 연소속도를 향상시킬 수 있었고, 분사형 착화기와 병행 사용하여 착화 신뢰성을 크게 높일 수 있었다. 2단계 환원 공정을 통해 산호 모양의 고순도 Fe 입자를 안전하게 얻을 수 있었다.

• 한국재료학회지
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• 제9권11호
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• pp.1075-1082
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• 1999

50/50 vol% LSM-YSZ의 복합공기극(LSM=$\textrm{La}_{1-x}\textrm{Sr}_{x}\textrm{MnO}_{3}$(0$\leq$x$\leq$0.5))이 콜로이드 증착법에 의해 준비으며 주사전자현미경과 임피던스 분석기에 의해 연구되어졌다. 재현성있는 임피던스 스펙트럼들이 LSM-YSZ/YSZ/LSM-YSZ로 구성된 향상된 셀을 사용함으로써 얻어졌다. 이러한 셀들의 임피던스 스펙트럼들은 작동온도에 강하게 영향을 받았으며, 가장 안정된 조건은 $900^{\circ}C$에서 도달되어졌다. $900^{\circ}C$에서 공기//공기 셀에 대해 측정된 전형적인 임피던스 스펙트럼들은 2개의 불완전한 호(depressed arc)로 구성되었다. LSM전극에 대한 YSZ의 첨가는 LSM-YSZ 공기극의 저항 감소를 가져왔으며, 전해질 표면의 불순물의 영향을 제거하기 위한 연마는 공기극 저항을 더욱 감소시켰다. 또한 촉매층(Ni 혹은 Sr)을 가진 LSM-YSZ 전극은 촉매층이 없는 경우에 비해 공기극 저항의 감소를 가져왔다. LSM-YSZ 공기극 저항은 전극조성, 전해질의 형태, 인가 전류에 의해 영향을 받았다.